Contemporary ENERGY Vol3 No1 (2017) by REMOO

International Journal of Contemporary ENERGY Peer-reviewed open-access E-journal

ISSN 2363-6440

Vol. 3, No. 1 (2017) February 2017 www.Contemporary-ENERGY.net

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Cover Illustration Windmill in Schiedam, The Netherlands; Source: http://de.123rf.com; Copyright: Jan Kranendonk

Founding Editor & Editor-in-Chief Zoran V. Stosic

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Director RENECON International, GERMANY; editor@contemporary-energy.net

Editorial Board Prof. Jan Blomgren

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Uppsala University; CEO of INBEx, SWEDEN

Ass. Prof. Leon Cizelj

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University of Ljubljana; Head of Reactor Engineering Division at IJS, SLOVENIA

Ass. Prof. Davor Grgić

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Faculty of Electrical Engineering and Computing, University of Zagreb, CROATIA

Dr. Maximilian Emanuel Elspas

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Head of Energy Law and Lawyer Partner at Beiten Burkhardt Law Munich, GERMANY

Dr. Dietmar O. Reich

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Co-Head of Competition Practice Group and Lawyer Partner at Beiten Burkhardt Law Brussels, BELGIUM

Dr. Miodrag Mesarović

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Secretary General of the SerbianWEC Member Committee; Senior Advisor to Energoprojekt-ENTEL, Belgrade, SERBIA

Prof. Ana M. Lazarevska

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Faculty of Mechanical Engineering, University of Skopje, MACEDONIA

Prof. Li Ran

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School of Engineering, University of Warwick, UNITED KINGDOM; Deputy Director of China State Key Lab in Power Transmission Apparatus Security, Chongqin University, CHINA

Prof. Xu Cheng

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Institute of Fusion and Nuclear Technology, Karlsruhe Institute of Technology – KIT, GERMANY; School of Nuclear Sciences and Engineering, Shanghai, Jiao Tong University, CHINA

Prof. Josua P. Meyer

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Department of Mechanical and Aeronautical Engineering, University of Pretoria, SOUTH AFRICA

Prof. Zhao Yang Dong

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Chair Professor and Head of School of Electrical and Information Engineering, University of Sidney, AUSTRALIA

M.Sci.Engng. Jukka Tapani Laaksonen

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Vice President ROSATOM Overseas, Moscow, RUSSIA; Former Director General of the STUK, FINLAND

M.Sci.Engng. Jože Špiler

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Head of TechnicalServices and Investments at GEN-energija, Krško, SLOVENIA

Prof. Michael Narodoslawsky

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Institute for Process and Particle Engineering, Technical University of Graz, AUSTRIA

Dr. Raffaella Gerboni

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Post-Doc Fellow Researcher, Energy Department, Politecnico di Torino, ITALY

Prof. Henryk Anglart

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Deputy Head of Physics Department, KTH Royal Institute of Technology, Stockholm, SWEDEN

Dr. Suna Bolat

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Ass. Professor, Eastern Mediterranean University – EMU, Gazi Mgusas, TURKEY

Prof. Nikola Popov

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Faculty of Engineering Physics, McMaster University, Hamilton; President DENIPO Consulting Ltd., Toronto, Ontarion, CANADA

Prof. Milovan Perić

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Managing Director of CoMeT Continuum Mechanics Technologies GmbH, GERMANY; Senior Corporate Consultant CD-adapco, UNITED KINGDOM

Prof. Umberto Desideri

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Department of Energy Engineering, University of Pisa, ITALY

Prof. Shpetim Lajqi

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Faculty of Mechanical Engineering, University of Prishtina, KOSOVO

Dr. Camila Braga Viera

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Université de Sherbrooke, Quebec, CANADA

Ass. Prof. Manuel Ruiz de Adana Santiago

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Department of Applied Thermodynamics, University of Cordoba, SPAIN

Dr. Naseem Udin

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Principal Lecturer, Institute Teknology Brunei, BRUNEI

Prof. Gordana Laštovička -Medin

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Faculty of Science and Mathematics, University of Montenegro, Podgorica, MONTENEGRO

Prof. Serkan Dag

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Department of Mechanical Engineering, Middle East Technical University – METU, Ankara, TURKEY

International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

ISSN 2363-6440

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___________________________________________________________________________________________________________ A Word from the Editor–in–Chief

International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

ISSN 2363-6440

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A WORD FROM THE EDITOR-IN-CHIEF I am welcoming you to this Issue of the Journal entering the third year of its existence. We mostly have published the best papers from the International Conference & Workshop REMOO. Sometimes, and in the last time more often we are receiving articles for publication, which have not been presented on the REMOO conferences. However, not all papers have been accepted because they do not fully meet our scientific or language standards. And talking about the quality of the papers, interesting is that many authors are frequently asking us about the progress in indexing and/or evaluating of the Journal by different associations. Even more interesting is the fact that sometimes they do not realise that this progress does not depend only on us but rather on the quality of their papers.

Founding Editor & Editor–In–Chief Zoran V. Stosic

However, this originates before and in aftermath of the conference. After pre-selecting a number of papers presented at the conference, which might be selected to be published in the Journal, we perform at least doubleblind peer review process. But in the most cases we make triple-blind and even quadruple-blind peer reviews to reach the quality acceptable for the Journal. This is a process in which the authors are improving their paper in accordance with the reports of reviewers. At the end, the authors are also satisfied realising that their papers became much better. There are also sometimes marginal number of authors who are not ready to finish the review process. The origin of such cases starts long before the reviewing process. It starts already by preparing the paper for the conference and initiating motives to submit it. But about this, I will perhaps write some other time. In this Issue we have published nine good papers, which went positively through our reviewing processes. So, enjoy flipping and reading …

___________________________________________________________________________________________________________ A Word from the Editor–in–Chief

International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

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Shpetim Lajqi, Xhemajl Fejzullahu, Naser Lajqi, Heset Hajdini Analysis of the Mini Turgo Hydro Turbine Performance for different Working Regimes

Yamina Boughari, Georges Ghazi, Ruxandra Mihaela Botez Optimal Control new Methodologies Validation on the Research Aircraft Flight Simulator of the Cessna Citation X Business Aircraft

Gazmend Pula, Kadri Kadriu, Gazmend Kabashi, Bajram Neshati Switch-Gear Capacity Fault Analysis of Kosovo Power System Key Busbar by Comparative Analytical and Numerical Software Methodology

Daniele Grosso, Raffaella Gerboni, Aquiles Martinez Perez Impacts of Non-Programmable Renewable Sources Penetration on the Italian Energy System: A Tool for Scenario Analyses

Gordana Laštovička-Medin Emerging Materials, Computational Research Needs and Challenges for Alternative Energy Innovations

Gordana Laštovička-Medin Open Source Sun Tracking System with Solar Panel Monitoring and Heliostat Control System

Zdravko Eškinja, Krunoslav Horvat, Vedran Bakarić, Ognjen Kuljača Review of Turbine Governing System Tests Performed on Hydro-Power Plants in Croatia

Ana M. Lazarevska, Daniela Mladenovska Corruption and Bad Governance vs. Reliable Energy in the Economies in Transition

Daniela Mladenovska, Ana M. Lazarevska Indicators Relevant for Energy Security Risk Assessment of Critical Energy Infrastructure

About the Journal

Instructions for Authors

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Authors‘ Papers

Global Energy – Uncertainty is the only Thing certain by Jan Blomgren

The Journal

Editorial

CONTENT

___________________________________________________________________________________________________________ Content

International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

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Editorial

.e1

Global Energy â&#x20AC;&#x201C; Uncertainty is the only Thing certain by Jan Blomgren

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GLOBAL ENERGY — UNCERTAINTY IS THE ONLY THING

CERTAIN

“Without passion you don't have energy, without energy you have nothing.” Donald Trump Claiming that the recent election of a new president in the US has attracted international attention is an understatement. The quote above is among the least controversial ones from the constantly twittering president-elect (when this was written). ”Without energy you have nothing” is a quote my late grandmother would agree upon immediately. She was a very calm and gentle old lady, never raising her voice – with one notable exception. Somebody once said ”back in the good old days”. This immediately triggered my grandmother. She promptly abrupted the discussion with the words ”there were no good old days – they were harsh old days!”. When she grew up, people lived a hard life at the islands where her fishermen family lived. They endured long and tough workdays and nights at sea, and if they were lucky they could get a sandwich for supper when they came back – if they came back at all. Many fishermen found their grave in the sea. Their houses were small little shacks exposed to winter storms straight from the open sea, with one single room for the entire family, having a small wood stove as the only energy source. ”It is much better now”, my grandmother concluded. ”Now we have electricity”. By the way, she lived to the age of 92, an age earlier generations could only dream about, the latter also being a consequence of improved living conditions thanks to energy. Energy shapes the entire society, and this is part of the reason the recent US election has been on the headlines. If it had been an issue about personality of candidate X versus candidate Y, but no major uncertainties about the political consequences, my guess is that the attention had still been large, but a bit smaller. However, the newly elected president has given contradicting messages on how to handle the energy challenges, and the key players identified in the new administration also seem to have rather different views on these matters. Will the US leave the international process of trying to curbe greenhouse gas emissions? Will the US leave free-trade agreements? That the former is relevant from a global energy perspective is obvious, but also the latter has implications for tackling the environmental and societal challenges in the energy sector. For instance, with high import fees, less energy-efficient production can be favoured. At present, we can only ask the questions. The answers still lie in an uncertain future. The role of science and technology as drivers in developing more efficient energy exploitation and thereby functioning as engine in global development was a common underlying theme in the recent REMOO conference held May 18-19 2016 in Budva, Montenegro. Although the conference title was ”Science and Engineering for Reliable Energy”, the conference attracted an even wider scope of contributions, not limiting to science and engineering in themselves, but also to their utilization in society. In fact, the scope was even wider: some contributions studied implications in the ___________________________________________________________________________________________________________ “Global Energy – Uncertainty is the only Thing certain”

International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

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opposite direction, i.e., how societal factors affect energy technology. Some of the contributions are presented in the present issue of the International Journal of Contemporary Energy. Two papers have a clear technical focus, in particular towards testing, training and simulation. Lajqi, Fejzullahu, Lajqi and Hajdini has developed a test facility for mini hydro turbines. Boughari, Ghazi and Botez presents work on optimization of an aircraft simulator. Moving on to energy systems, Pula, Kadriu, Kabashi and Neshati present a study of the reliability of the power system in Kosovo. Grosso, Gerboni and Martinez Perez describe trends in the introduction of variable electricity production (read wind and solar photovoltaics) and its effects on power systems. Lastovicka-Medin presents a condensed survey of computational needs for emerging energy technologies in general, with special attention on materials issues, and a paper on how to improve the performance of solar PV production by tracking the optimal direction to the sun. The governance of hydropower turbines has been the focus of research by Eskinja, Horvat, Bakaric and Kuljaca. The aim of this study is improved knowledge of the technical health of the system, to be used for improved production and maintenance planning. Finally, we have papers on how society affects energy technology. Lazarevska and Mladenovska presents findings on the consequences of corruption and bad governance on the energy system. These two authors joined forces with Mitrovska Mirchevska in an energy security risk assessment for critical infrastructure. This sums up the contributions in this issue of the International Journal of Contemporary Energy. You can look forward to most interesting reading. Last but not least, reserve May 10-12, 2017 in Venice, Italy, for the next conference in this series.

Jan Blomgren Associate Editor

Jan Blomgren is CEO and founder of INBEx (Institute of Nuclear Business Excellence), providing independent nuclear executive advice and business leadership training globally. The INBEx team comprises over 20 former CEOs, Director Generals and similar. He was the youngest professor ever in Sweden in nuclear physics, holding the chair in applied nuclear physics at Uppsala University. His research was focused on neutron-induced nuclear reactions, an area in which he has published over 200 papers in refereed international journals and conference proceedings. When plans to build new nuclear power in Sweden were initiated, he was recruited to Vattenfall, one of the largest nuclear power operators in Europe. At Vattenfall, he was responsible for planning the competence development needed for nuclear new-build, as well as coordinating training for nuclear power plant personnel. In addition, he was Director of the Swedish Nuclear Technology Centre, which is the coordination organization for nuclear research and education involving universities, industry and the regulator. He was involved in the creation of ENEN, the European Nuclear Education Network, in which essentially all European universities in nuclear engineering collaborate. Moreover, he has recently established a large collaboration with France on research and education. Finally, he is the father of several industry-sponsored university programs, as well as having started a number of nuclear business training programs in industry. Jan Blomgren is alone in Europe to have upheld high-ranked positions both at university and nuclear industry. He is frequently invited speaker at conferences, and was recently invited as expert advisor to the French Senate.

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International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

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Authors’ Papers 1

Shpetim Lajqi, Xhemajl Fejzullahu, Naser Lajqi, Heset Hajdini

Analysis of the Mini Turgo Hydro Turbine Performance for different Working Regimes 9

Yamina Boughari, Georges Ghazi, Ruxandra Mihaela Botez

Optimal Control new Methodologies Validation on the Research Aircraft Flight Simulator of the Cessna Citation X Business Aircraft 19

Gazmend Pula, Kadri Kadriu, Gazmend Kabashi, Bajram Neshati

Switch-Gear Capacity Fault Analysis of Kosovo Power System Key Busbar by Comparative Analytical and Numerical Software Methodology 29

Daniele Grosso, Raffaella Gerboni, Aquiles Martinez Perez

Impacts of Non-Programmable Renewable Sources Penetration on the Italian Energy System: A Tool for Scenario Analyses 37

Gordana Laštovička-Medin

Emerging Materials, Computational Research Needs and Challenges for Alternative Energy Innovations 44

Gordana Laštovička-Medin

Open Source Sun Tracking System with Solar Panel Monitoring and Heliostat Control System 51

Zdravko Eškinja, Krunoslav Horvat, Vedran Bakarić, Ognjen Kuljača

Review of Turbine Governing System Tests Performed on Hydro-Power Plants in Croatia 57

Ana M. Lazarevska, Daniela Mladenovska

Corruption and Bad Governance vs. Reliable Energy in the Economies in Transition 70

Daniela Mladenovska, Ana M. Lazarevska

Indicators Relevant for Energy Security Risk Assessment of Critical Energy Infrastructure

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DOI: 10.14621/ce.20170101

Analysis of the Mini Turgo Hydro Turbine Performance for different Working Regimes Shpetim Lajqi, Xhemajl Fejzullahu, Naser Lajqi*, Heset Hajdini University of Prishtina, Faculty of Mechanical Engineering Bregu i Diellit p.n., 10 000 Prishtina, Kosovo; naser.lajqi@uni-pr.edu

Abstract

1. Introduction

Many countries, especially in rural zones, have serious problems in supplying electrical energy. In order to fulfil such requirements, and obvious solution is the installing of mini hydro turbines due to their simplicity in manufacturing, installing, lower prices and wide potential.

Energy in general, and electricity in particular, are key elements and very important factors in everyday life and the development of society. Considering the increasing demands for electricity and problems with pollution coming from coal-fired power plants, its production from Renewable Energy (RE) sources is among of the alternative solutions.

During the exploitation of hydro turbines in different periods of the year, there are cases where they cannot generate electricity due to the low water flow, which is a characteristic of Kosovo rivers. In order to generate energy which corresponds to the changing flow of water, a mini Turgo hydro turbine by different working regimes has been designed and manufactured. For analysing mini Turgo hydro turbine efficiency, a test bench must be used. The test bench consists of a water steel tank from which a centrifugal pump draws the water into the Turgo turbine, therefore creating a suitable water head. An inductive generator is connected directly to the turbine runner, which converts the hydraulic energy into electric energy. The test bench has several installed measuring devices, such as flow meters, pressure gauges, ampere meters, voltage, etc. Mini Turgo turbines have four manual ball valves with four different diameters of nozzle. Valves are operated manually, creating several working regimes by changing the water head and flow. For each working regime, the results have been presented graphically and numerically in order to determine turbine efficiency and other characteristics. The aim of this paper is to make a comprehensive analysis of the efficiency obtained by theoretical and experimental methods for Turgo hydro turbines in different working regimes.

Keywords:

Turgo turbine; Flow; Pressure; Power; Efficiency

Article history:

Received: 18 December 2016 Revised: 27 January 2017 31 January 2017 Accepted: 01 February 2017

The hydropower plants represent an example of renewable energy sources through which it is possible to produce electricity by using the hydro potential of water. In addition, electricity production in hydropower plants is particularly important when considering its positive impact on environmental protection. On the other hand, the hydro turbine produces power during the day and night, and they are better than other alternative sources of energy such as wind, solar, etc. [12]. The first hydropower plant in Kosovo was built in the town of Prizren in 1929 with an output power of 160 kVA, with its energy mostly used for the lighting of the several streets. Another hydropower plant was built in Mitrovica on the river Iber in 1930. After the Second World War several locations in Kosovo began construction of Small Hydropower plants (SHPP). In 1948 a plant was built in Istog with a generation capacity of 0.5 MW, while in 1957 in Kozhnjer – Deçan two generators with capacity 8 MW were installed. Another SHPP was built in Dikanc with a capacity of 1.4 MW in 1956. The biggest Hydropower Plant in Kosovo started work in 1981 on the River Iber. It was called “Gazivoda” and had a capacity of 34 MW [3]. According to Directive 2009/28/EC of the European Council, the Republic of Kosovo has taken the obligation up to undertake the following activities by 2020:

___________________________________________________________________________________________________________ Sh. Lajqi, Xh. Fejzullahu, N. Lajqi, H. Hajdini: “Analysis of the Mini Turgo Hydro Turbine Performance for different Working Regimes”, pp. 1–8

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− 20% of electricity generation to be from RE, − 20% reduction of CO2, and − 20% increasing energy efficiency. In order to meet EC directive requirements, the government of the Republic of Kosovo has prepared a strategy for the period 2013-2020 for building new capacities from RE sources, such as water, wind, sun and biomass by approving feeding tariffs. In 2013 the generation energy from RE was 47.56 MW, while the government target up to 2020 is 765.2 MW [4]. According to some statistics, the hydro potential in Kosovo is very limited and can meet only 10% of the requirements of domestic consumption of electricity. The largest percentage of electricity generation can be obtained from wind, sun, biomass, etc. Due to poor water flow of rivers in the Republic of Kosovo, generation of energy from water is also limited, and thus the alternative is the building of hydropower plants with low generation. In order to use these rivers’ potential, the installing of the mini hydropower plants due to their simplicity in manufacturing and low costs is a very viable option [5]. The literature [6] details several Kosovo rivers flows; for example, the water flow in Mirusha river varies from a minimum of 0.02, an average 1.21 and a maximum 23.30 [m3/s]. Given the great change of flow within the year, it was necessary to choose mini hydropower plants to suit different working regimes. For this purpose, a testing device at the Faculty of Mechanical Engineering in Prishtina, funded by the Ministry of Education, Science and Technology of the Republic of Kosovo was created [7]. The Turgo turbine is a hydroelectric impulse turbine suitable for medium to high head application (50<H<250

m). It has gained renewed attention in research due to its potential application, because it is easy to produce and it has a low cost [8-9]. Under the best conditions, the Turgo turbine efficiency was observed to be over 80%, which is quite good for pico-hydro-scale turbines [10]. The purpose of this study is to analyse the performance of a developed mini Turgo Turbine for 15 different working regimes to determine its efficiency.

2. Testing bench of the mini-hydropower plant The Testing Bench has been designed for students in order to understand the basic working principles of the mini hydroelectric power station. It is a complete system like in a real hydro power plant, only that the water regulated from the pump instead of a waterfall. The testing bench consists of a water steel tank (1) from which a centrifugal pump (2), which draws the water into the Turgo turbine (3), creating a suitable water head (H). An inductive generator (4) is connected directly to the turbine runner, which converts the hydraulic energy into electric energy, Figure 1 [7]. A test bench (mini Turgo turbine) has four manual ball valves with different diameters of nozzle. Valves are operated manually which create several working regimes by changing the water head and flow. Each working regimes is presented with graphic and numeric results in order to determine turbine efficiency. The turbine power is dependent from the water head (H) and flow rate (Q). These parameters determine runner pitch diameter (dp), rotational speed (N), turbine power (Pturb), numbers, diameter of nozzles and number of spoons of runners are in the function of pump characteristic, Figure 2.

Figure 1. Test bench of the mini hydropower plant [7] ___________________________________________________________________________________________________________ Sh. Lajqi, Xh. Fejzullahu, N. Lajqi, H. Hajdini: “Analysis of the Mini Turgo Hydro Turbine Performance for different Working Regimes”, pp. 1–8

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Figure 2. Pump curves of producer and measured flow rate in test bench

Figure 3. Measuring instruments for determining turbine efficiency

From Figure 2 we can see that the curves of pumps taken from the producer and measuring are different. This difference is a result of using available bulk water meters

with a small size in the output of pump as well as pipe fittings, ball valves which create additional losses and reflect in the decreasing flow and water head.

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Figure 4. Configuration of nozzles in test bench

Figure 5. Method for measuring of force in steel rope through pulley

Table 1: Possible combination of nozzles Working Regimes 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Combinati on of nozzles 1 2 3 4 1+2 1+3 1+4 2+3 2+4 3+4 1+2+3 1+2+4 1+3+4 2+3+4 1+2+3+4

Cross section of nozzles [mm2] 59.86 71.33 83.65 111.41 131.19 143.50 171.26 154.98 182.74 195.05 214.83 242.60 254.91 266.38 326.24

Diameter of equivalent nozzles [mm] 8.73 9.53 10.32 11.91 12.92 13.52 14.77 14.05 15.25 15.76 16.54 17.58 18.02 18.42 20.38

The measuring instruments which are used in the test bench are: ampere meters, voltage meters, a digital tachometer, water flow meter, pressure gauge and a dynamometer, which allows us to determine turbine efficiency during the different working regimes, Figure 3.

3. Methodology for analysis of working regimes A testing bench has four ball valves with four different sizes of nozzles (Figure 4), which gives 15 possible operation points of turbine (the 16 is the trivial zeroflow maximal head point on the pump curve), Table 1.

The output power in the shaft of a hydro turbine (Pturb) is a function of the head and flow and is written by the following expression:

Pturb = ρ ⋅ g ⋅ H n ⋅ Q ⋅η t [W ]

(1)

In the other side, the turbine’s power output (Pturb) is the product of the torque (T) and rotational velocity (ω), which is determined by the following expression, Figure 5:

Pturb = T ⋅ ω = F ⋅ r ⋅ ω [W ]

ω=

π ⋅ NTurb 30

[s ]

(2)

−1

(3)

A turbine’s experimental efficiency is:

ηt =

Pturb

ρ ⋅ g ⋅ Hn ⋅Q

⋅100 [%]

(4)

where:

ρ = 1000 [kg/m3] – water density, g = 9.81 [m/s2]

– gravity acceleration,

ηt [%]

– turbine efficiency,

T [Nm]

– torque in shaft of turbine,

F [N]

– force in steel rope,

r = 0.1 [m]

– pulley radius,

N [rpm]

– rotation speed of generator shaft.

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Measurement of turbine power (Pturb) is done through a pulley with a radius (r) which is fixed in the shaft of the generator. In the pulley is an open trapeze channel in which is located a steel rope. One side of the steel rope is fixed for the beam, while the other has a dynamometer which measures tensile force (F). During measurement, the rotational speed of the generator (N) should be constant (1500 rpm).

4. Determining of turbine efficiency In this paper we analyse six working regimes of the mini Turgo hydro turbine. The first working regime is when the first ball valve is open by the nozzle diameter Ø8.7 mm, while the second

regime is only when the second ball valve with nozzle diameter Ø9.5 mm is open. These cases present a situation where the water flow rate has a lower value but the water head gets large values, Figure 6. Figure 7 presents the output power obtained in a shaft of the turbine for the first and second working regimes. The turbines efficiency for the first working regime is:

η1turb =

P1turb = 0.845 ρ ⋅ g ⋅ H 1n ⋅ Q1

(5)

The turbines efficiency for the second working regime is:

η 2turb =

P2turb = 0.838 ρ ⋅ g ⋅ H 2 n ⋅ Q2

(6)

Figure 6. Flow rate vs. water head for first and second working regimes

Figure 7. The output power of turbine vs. water head for the first and second working regimes ___________________________________________________________________________________________________________ Sh. Lajqi, Xh. Fejzullahu, N. Lajqi, H. Hajdini: “Analysis of the Mini Turgo Hydro Turbine Performance for different Working Regimes”, pp. 1–8

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Figure 8. Flow rate vs. water head for third and fourth working regimes

Figure 9. The output power of turbine vs. water head for third and fourth working regimes

From Figure 6 and Figure 7 we see the increasing diameter of nozzles from Ø8.7 to 9.5 mm, where the water flow is significantly increased while the water head is the same. The output power of the turbine is increased by 16% while the efficiency is reduced from 84.5 to 83.8%. The third working regime is when the third ball valve is open by a nozzle diameter of Ø10.3 mm, while the fourth regime is when the fourth ball valve, with a nozzle diameter of Ø11.9 mm, is open exclusively. These cases are presented in Figure 8. Figure 9 presents the output power obtained in the shaft of the turbine for the third and fourth working regimes. The turbines efficiency for third working regime is:

η 3turb =

P3turb = 0.835 ρ ⋅ g ⋅ H 3n ⋅ Q3

(7)

The turbines efficiency for fourth working regime is:

η 4turb =

P4turb = 0.832 ρ ⋅ g ⋅ H 4 n ⋅ Q4

(8)

In Figure 8 and Figure 9 it is shown that with an increasing diameter of nozzles from Ø10.3 to 11.9 mm water flow significantly is increased while the water head is dropped from 28.7 to 27.8 m. The output power of turbine is increased to 27% while efficiency is reduced from 83.5% to 83.3%. The fourteen working regimes happen when the second + third + fourth ball valves are open (nozzles diameter Ø9.5 + Ø 10.3 + Ø 11.9 mm), while the fifteen regimes is when all ball valves are open (nozzle diameter Ø8.7 + Ø9.5 + Ø 10.3 + Ø 11.9 mm). These cases present a situation where water flow rate gets the largest value but the water head gets lower values, Figure 10.

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The turbines efficiency for fourteen working regime is:

η14turb =

P14turb = 0.825 ρ ⋅ g ⋅ H14 ⋅ Q14

(9)

The turbines efficiency for fifteen working regime is:

η15turb =

P15turb = 0.805 ρ ⋅ g ⋅ H15 ⋅ Q15

(10)

In Figure 11 are presented the output powers obtained in the shaft of the turbine for the fourteen and fifteen working regimes. From Figure 10 and Figure 11 we can see that with an increasing numbers of nozzles from 3 to 4 pieces, water flow significantly is increased while the water head is dropped from 21.4 to 18.7 m. The output power of turbine is increased 2.5%, while efficiency is reduced from 82.5 to 80.5%.

Figure 10. Flow rate vs. water head for fourteen and fifteen working regimes

Figure 11. The output power of turbine vs. water head for fourteen and fifteen working regimes

5. Conclusion Based on the comprehensive analysis of the working regimes of a developed mini Turgo turbine through a test bench, we can conclude that:

− For a higher water head (around 30 m), the turbine efficiency is better (~ 84%), while for lower head the efficiency significantly dropped (81%), although water flow increased. This fact confirm the Turgo turbine gives better efficiency

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in medium and higher head application 50<H<250 m; − By decreasing of the water flow, the number of nozzles should be reduced in order to maintain higher water head respectively efficiency; − Each working regime has a slightly different peak power and rpm, which significantly influences fluctuation tension and frequency in the generator; − In order for the test bench to be more suitable for a mini Turgo turbine for medium and higher head application, it is necessary to replace the existing pump with a higher head in order to maintain efficiency, voltage and frequency. Based on the findings outlined above on river hydrology and configuration of Kosovo rivers, the authors recommend the installing of Turgo turbines.

[3]

Hajdini Heset, Analysis of working regimes of mini hydropower plants, Master Thesis, University of Prishtina “HASAN PRISHTINA”, pp. 1-94, Prishtina 2016.

[4]

http://eroks.org/2016/Vendimet/V_810_2016.pdf/17.12.2 0106/

[5]

Lajqi Shpetim, Lajqi Naser, Hamidi Beqir, Design and Construction of Mini Hydropower Plant with Propeller Turbine, International Journal of Contemporary ENERGY, Volume 2, Issue 1 (2016), pp. 1-13.

[6]

http://www.ammkrks.net/repository/docs/raporti_ujrave%202010 _shq.pdf

[7]

Lajqi Shpetim, Pehan Stanislav, Fejzullahu Xhemajl, Design and Production of the Testing System of the Mini-Hydroelectric Power Station with Turgo Turbine, The 4th International Conference & Workshop "Energy Infrastructure Development" REMOO 2014, 12-13 November 2014, Ljubljana, Slovenia.

[8]

Guide on How to Develop a Small Hydropower Plant, ESHA 2004.

[9]

Gaiser Kyle, Erickson Paul, Stroeve Pieter, Delplanque Jean-Pierre, An experimental investigation of design parameters for pico-hydro Turgo turbines using a response surface methodology, Renewable Energy, Elsevier, Volume 82 (2016), pp. 406 -418.

[10]

Cobb Bryan, Sharp Kendra, Impulse (Turgo and Pelton) turbine performance characteristics and their impact on pico-hydro installations, Renewable Energy, Elsevier, Volume 50 (2013), pp. 959-964.

Acknowledgements The authors are profoundly grateful to the Ministry of Education, Science and Technology of the Republic of Kosovo, who have financially supported this research project.

References [1]

Mohibullah, M. A. R. and MohdIqbal Abdul Hakim, Basic design aspects of micro-hydropower plant and its potential development in Malaysia, National Power and Energy Conference (PECon) Proceedings, Kuala Lumpur, Malaysia, 2004.

[2]

Bilal Abdullah Nasir, Design of Micro - Hydro Electric Power Station, International Journal of Engineering and Advanced Technology, Volume 2, (2013), Issue 5, pp. 39-47.

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DOI: 10.14621/ce.20170102

Optimal Control new Methodologies Validation on the Research Aircraft Flight Simulator of the Cessna Citation X Business Aircraft Yamina Boughari*, Georges Ghazi, Ruxandra Mihaela Botez ETS, Laboratory of Active Controls, Avionics and AeroServoElasticity LARCASE 1100 Notre Dame West, Montreal, Quebec, H3C-1K3 Canada; Yamina.boughari.1@ens.etsmtl.ca

Abstract

1. Introduction

In this paper the Cessna Citation X clearance criteria were evaluated for a new Flight Controller. This Flight Controller was designed and optimized using a combination of the Hinfinity method and the Differential Evolution algorithm, during a previous research. The linear stability, eigenvalue, and handling qualities criteria in addition of the nonlinear analysis criteria were investigated during this research to assess the business aircraft for flight control clearance and certification. The optimized gains provide a very good stability margins as the eigenvalue analysis shows that the aircraft has a high stability, and a very good flying qualities of the linear aircraft models are ensured in its entire flight envelope, its robustness is demonstrated with respect to uncertainties due to its mass and center of gravity variations.

The clearance of the flight control laws of a civil aircraft is a fastidious process, especially for modern aircrafts that need to achieve high performance as shown by in [1]. This process aims to prove that the selected stability, robustness and handling requirements are satisfied against any possible uncertainties. Because of the high number of data, the parameters variations and their uncertainties have to be provided for the clearance of the large flight envelope. To carry out this process, a detailed description of methods and procedures, which are used in industry, was given by Udo Korte [2]. The presence of uncertainties is related to many factors, such as the mass and Xcg variations, aerodynamics data values, control surfaces dynamics and delays, and Air Data measurements errors [3]. To demonstrate the effects of uncertainties, the clearance criteria are considered as robustness criteria from the Airbus team point of view, and were applied in linear, and nonlinear analysis. As well as in the simulation of HIRM+ generic model and HWEM the realistic model aircrafts as shown in [1]. A benchmark of high- fidelity generic civil aircraft was developed by Airbus for advanced flight control, and fault diagnosis research in [4]. In [5] a stochastic robust flight control was applied to the highly uncertain nonlinear HIRM aircraft model and compared its robustness of its flight control laws with other competitive flight control laws by using the Nichols plot. The research presented in [6], highlighted the importance of the clearance task, where it summarized five (5) new analysis techniques were applied to solve a benchmark clearance problem, researches and results of one of these 5 new techniques were presented extensively in [7], this technique is known as the clearance based optimization technique. Linear and nonlinear Cessna Citation X business aircraft benchmark was developed at Laboratory of Active Controls, Avionics and AeroServoElasticity LARCASE in [8]-[9] by using a Cessna Citation X Level D Research Aircraft Flight

Keywords:

Flight control clearance; Stability criteria; Aircraft handling qualities; Eigenvalues; Aircraft nonlinear analysis

Article history:

Received: 08 April 2016 Revised: 22 January 2017 Accepted: 23 January 2017

___________________________________________________________________________________________________________ Y. Boughari, G. Ghazi, R. M. Botez: “Optimal Control new Methodologies Validation on the Research Aircraft Flight Simulator …”, pp. 9–18

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Simulator designed and manufactured by CAE Inc. This benchmark programmed in Matlab/Simulink was used for advanced flight control design and clearance [10][11], for robust control analysis in [12]-[13], and for new identification methods designed and developed in [14][16]. The clearance analysis of linear and the nonlinear the Cessna Citation X business aircraft is addressed for the first time in this paper, which gives to the reader an excellent understanding of the criteria and visualization tools used in the assessment of the flight control laws. The aircraft linear model with actuators, and sensors dynamics is detailed, then a brief description of the clearance criteria theory is listed. Analysis of results and conclusions is further given.

2. Cessna Citation X aircraft actuators and sensors dynamic The Cessna Citation X is the fastest civil aircraft in the world, as it operates at its speed upper limit given by Mach number of 0.935. [18] The longitudinal and lateral motions of this business aircraft are described, as well as its flight envelope and the flying qualities requirements. The aircraft nonlinear model for the development and validation of the flight control system used the Cessna Citation X flight dynamics, and was detailed by Ghazi in [8], [9]. This model was built in Matlab/Simulink based on aerodynamics data extracted from a Cessna Citation X Level D Research Aircraft Flight Simulator designed and manufactured by CAE Inc. According to the Federal Administration Aviation (FAA, AC 120-40B) [19], the Level D is the highest certification level that can be delivered by the Certification Authorities for the flight dynamics. More than 100 flight tests were performed on the Citation X Level D Research Aircraft Flight Simulator within the aircraft flight envelope to validate linear model in [8], and tests were performed extensively in order to identify the Cessna Citaion X aircraft model in [14], [15], and the Engine model as in [16]. Using trim and linearization routines developed by Ghazi and Botez [8], and [9], the aircraft longitudinal and lateral equations of motions have been linearized for different flight conditions in terms of altitudes and speeds, and different aircraft configurations in terms of mass and center of gravity positions. In order to validate the different models obtained by linearization, several comparisons of these models with the linear model obtained by use of identification techniques as the ones proposed in [14-[16] were performed for different flight conditions and aircraft configurations. Results have shown that the obtained linear models were accurate and could be further used to estimate the local behaviour of the Cessna Citation X for any flight conditions.

2.1. Aircraft dynamics The aircraft’s dynamics is represented firstly by nonlinear equations representing the equations of motion in the three axis (x, y, z) as given in [19], and secondly these nonlinear equations are linearized, the longitudinal and lateral motions are decoupled for each equilibrium point, which means that the longitudinal motion dynamics can be represented for each flight condition or equilibrium point under the form of the following state space equation, using the elevator as deflection angle input: =A A

(1)

= X X X Z Z Z M +M Z M +M Z M +M u 0 0 1

Xδ Zδ + M Zδ 0

−gcosθ 0 , 0 0

(2)

where the state vector (t) are given by: vector

( ) and the control

Mδ

( ) = (u w q θ) and

( ) = δ (3)

In the same way the aircraft’s lateral motion dynamics is also given by the state space equation, using the aileron and the rudder as deflection angle inputs: =A A

+ B u

(4)

Yβ ⁄u Y ⁄u −(1 − Y ⁄u ) gcosθ ⁄u L L Lβ 0 Nβ N N 0 0 0 1 0 Yδ ⁄u Yδ ⁄u Lδ Lδ B = Nδ Nδ 0 0 where the state vector ( )are given by: ( ) = (β p r ϕ)

(5)

( ) and the control vector

and

( ) = (δ δ )

(6)

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(a)

(b)

Figure 1. (a) Flight envelope with LFR regions; (b) Weight versus Xcg envelope

Table 1: Actuators dynamics characteristics

ఠమ ௦ మ ାଶ ζ ఠ௦ାఠమ

Actuator

Frequency Damping Angle  ߱ [rad/sec] ζ [ ]

(7)

Rates 

[ /s]

Elevators

0.7

േ20

േ30

Rudder

0.7

േ20

േ30

Ailerons

0.7

േ60

േ30

The linearized model of the Cessna Citation X is obtained for 36 flight conditions using the Cessna Citation X Aircraft Flight Research Simulator tests performed at our laboratory LARCASE. The linearized model is further decomposed using the Linear Fractional Representation (LFR) method as explained in [20]; the bilinear interpolation method is used to present by 26 regions of the flight envelope by LFR models as shown in Figure 1(a). Thus, 72 flight points represented by state space models are obtained for each Xcg and weight configuration for a total of 12 Xcg and weight configurations shown in Figure 1 (b).

2.2. Actuators and sensors dynamics The actuators dynamics are provided from the literature [8], and are given as second order transfer function – their damping and frequencies are mentioned in Table 1:

2.3. Flight controller The flight controller is designed, and optimized using a combination of the Hinfinity control method and the Differential Evolution algorithm, where the objective function used in the previous research combined both time domain performance criteria and frequencydomain robustness criterion, which led to good level aircraft flying qualities specifications and reduce considerably the time computing, this method is given in detailed by Boughari et all [11] and [21].

3. Clearance criteria 3.1. Linear stability and eigenvalue analyses The aim of the aircraft clearance and certification is to prove that the aircraft is stable over its full flight envelope with sufficient margin stabilities, in the presence of uncertainties as shown in [6]. An overview of 5 new techniques for analysing the stability and robustness was considered by the industry in [6]. The basic theory of the linear stability was given in [22], while methodologies and results on these new techniques were presented in [23], [24], [25], and [26]. The weight functions method was applied on the business Hawker 800 XP, and on the HIRM aircrafts to assess their stability in [27] and [28]. In this paper linear stability margins for the pitch, and roll open – loop

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frequency responses were investigated for the Cessna Citation X business aircraft using Bode and Nichols plots. The unstable eigenvalues either of the unaugmented aircraft or augmented closed-loop system must be identified for the worst cases [29]. During this research, the open loop eigenvalues are identified by using “the robustness stability”, and analysed using the GUI developed by the COFCLUO project [30]. In addition the closed loop eigenvalues are investigated by using zero poles map.

3.2. Linear, nonlinear handling qualities and nonlinear analyses The linear handling analysis is presented in time domain and frequency domain criteria [31]. The time domain criteria are given by : 1.

Pitch acceleration peak time, pitch rate peak time, pitch rate overshoot/dropback, roll mode time constant, and time to bank.

The frequency domain responses and results, which are the most used to assess the linear handling criteria are defined [31-32]: 2.

Pitch/bank attitude frequency response.

The pitch/bank average phase rate, and the absolute amplitude should assess the resistance to Pilot Induced Oscillation (PIO).

Frequency and damping of short period mode, dutch roll and Flight Control System (FCS) modes [31]-[32] and their relationships with flight tests data parameters were given in [33].

Closed-loop pitch axis bandwidth (Neal Smith), the open-loop pitch axis bandwidth (Hoh), and phase and gain margin criterion (Roger).

A civil aircraft should have good handling requirements in addition of the stability ones. The aircraft certification and assessment has to give the proof that the aircraft is capable to accomplish the flight easily with excellent handling qualities given by level 1, which is defined as the highest by the American military specification F8785C [32] among 3 levels of flying qualities. Also the nonlinear analysis has to investigate problems encountered in the linear analysis, and to evaluate the aircraft stability, handling and control in the presence of nonlinearities.

3.3. Pitch control and rapid roll The aircraft manoeuvres are usually evaluated in modern flight control according to [1], which means that the load factor and angle of attack are proportional to the pitch command (stick deflection). By using different

inputs types (pull/push, step, and ramp), the required aircraft response trajectory should not exceed a given limit in the nominal aircraft model including added uncertainties. The rapid roll control mode is a very important criterion to be checked for the nominal aircraft model or in presence of uncertainties. The maximum roll rates/overshoots, roll angle overshoot, maximum sideslip generated during roll, and the load factor have to be verified.

4. Analysis of results Closed loop simulations of the Cessna Citation X longitudinal and lateral aircraft linear and nonlinear models, were performed for the whole flight envelope. The results presented below were obtained for 12 XCG and weight configurations, by using of 72 flight conditions obtained from both the Cessna Citation X flight simulator, and by using the interpolation method.

4.1. Stability analysis The phase margin for 26 regions (where each region is obtained for a number of 4 flight conditions) representing the entire flight envelope as shown in Figure 2. It can be noticed that the phase margin of almost the entire envelope is between 60 deg, and 90 deg, which is stable. If the results obtained for different weight and Xcg conditions are compared, we can see that they decreases for some flight conditions of heavy Gross Weights, high True Air Speeds (TAS), and Altitudes (h) above 35000 feet and 300 knots, and for those beyond the flight envelope limits. Detailed Bode and Nichols plots are shown in Figure 3, where the gain margin for almost the entire envelope is higher than 6 dB, which leads to the conclusion that good stability margins are ensured by the new optimized controller.

4.2. Eigenvalue analysis The aircraft open loop eigenvalues are analyzed using the Lyapunov function given by the “Stabilty and Robustness” toolbox developed during COFCLUO project developed in Europe in 2011, for a given weight and Xcg condition as shown in Figure 4. It can be deduced that the behaviour of the aircraft is “naturally stable“ except for the region of very high altitudes and True Air Speeds (TAS), which is already shown by the stability margins results given in the Figure 2 and Figure 3, and also for other worst combination of parameters (altitude h and TAS). The closed loop eigenvalues are presented by pole zero maps and are shown in Figure 5(b), where all flight conditions are given in the left half plan of the pole- zero map, which means that the new controller stabilizes the aircraft.

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(a) The 1st weight and Xcg condition

(b) The 12th weight and Xcg

Figure 2. Minimum phase margin versus flight conditions per region for all angle of attack (up to 14 deg)

4.3. Handling qualities analysis The aircraft longitudinal and lateral motions are stabilized with the H-infinity controller. For both controls the pitch angle rate q, and the roll angle ϕ, the resulting response for pitch rate control are shown in Figure 5: the flying qualities level 1 are satisfied as they have the damping ratio, and natural frequency within the limits given by [32] for both lateral and longitudinal motions, and the imposed time domain performance, given by the Integral Square Error (ISE) less than 2%, and overshoot (OS) of less than 30%, which means that the optimized gains are very satisfactory, they ensure a very good flying qualities of level 1. The results in Table 2 show the percentage of the cleared flight envelope according to the Flying qualities level 1, by using the new optimized controller in both the pitch and roll angle controls.

Table 2: Flight points with the good handling qualities over the flight envelope Controls

Flight points with the good handling qualities using the DE algorithm

Pitch rate q

860/864 (99.5%)

Roll angle φ

851/864 (98.5%)

4.4. Nonlinear analysis Finally, to prove the efficiency of the optimized controller, its robustness against uncertainties, and the effects of nonlinearities, a nonlinear validation was performed using the Cessna Citation X aircraft’s nonlinear model developed to simulate a real aircraft dynamics. A simulation of a pitch angle rate and roll angle ϕ controls responses were performed, and the results were shown respectively in Figure 6, and Figure 7 for the altitude of 2000 ft, TAS of 230 knots and load of 26000 lb, and varying mass. It can be seen that the pitch angle rate q and roll angle ϕ hold responses remained stable during the simulation despite the mass variation, and that all the performance criteria were reached. Figures 8 (a) and (b) show robustness results for the nonlinear model of the Cessna Citation X with H∞ controller by taking into account the nonlinear dynamics, actuators, sensors, saturations and signal processing times. A total of 160 tests were performed by generating uncertainties of +/- 5% on the mass and the center (position of center of gravity) with respect to a nominal condition for which the controller was obtained. The selection of the nominal flight condition and uncertainties were random. The results revealed that the pitch rate, and roll angle controls were stable with respect to the mass, and center of gravity position variations; the variations were stable and further included in the acceptable range.

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(a) Bode diagram

(b) Nichols diagram Figure 3. Bode diagram and Nichols for the 2nd Xcg condition ___________________________________________________________________________________________________________ Y. Boughari, G. Ghazi, R. M. Botez: “Optimal Control new Methodologies Validation on the Research Aircraft Flight Simulator …”, pp. 9–18

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Figure 4. Aircraft stability analysis using Lyapunov function.

(a)

(b) (b)

Figure 5. (a) Time response for the pitch rate q (b) the resulting pitch angle and pole, zero map

Figure 6. (a) Pitch angle rate q hold control responses (b) the resulting altitude, true airspeed, heading and mass variation responses of the nonlinear aircraft model

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Figure 7. Roll angle ϕ control responses of the nonlinear aircraft model

(a)

(b)

Figure 8. Pitch rate q (a) and Roll (b) response using mass and Xcg variation

5. Conclusion In this paper, the clearance criteria for the new flight controller of Cessna Citation X business aircraft were evaluated, which is a part of the certification process. The clearance addressed how flight limitations were derived for the Cessna Citation X business aircraft from the worst cases parameters combinations, such as True airspeed (TAS) and altitude (h), and they could be visualized and analysed to give precise information on the direction, which the aircraft was allowed to fly. These limitations were clearly shown by the eigenvalues analysis, where the stability of the aircraft could be analyzed in its flight envelope limits. The flight control

laws design optimization provided gains that have ensured very good stability margins in terms of phases and gains, these gains also provided to the aircraft very good flying qualities of Level 1. Regarding the manoeuvres such as the pitch and roll hold, their stability and robustness in presence of uncertainties dues to the mass and center of gravity variations were tested on the nonlinear aircraft model, and the obtained results were found to be very good. The new optimized controller had ensured its stability and robustness against mass variations to the Cessna Citation X business aircraft which has led to safe control flight operations.

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Control and Information Science. Springer-Verlag Berlin Heidelberg, Germany, 2012.

Nomenclature A,B,C,D p, q, r u, v, w u(t) x(t) V X, Z, Y OS Ts , θ, β, ϕ

ωn ζ

State Space matrices Angular Speeds along Ox, Oy, Oz axis Linear Speeds along the Ox, Oy, Oz axis Control Vector State Space Vector True Aircraft Speed Aircraft Aerodynamic Forces Overshoot Settling Time Elevator, Aileron, and Rudder deflections Pitch angle, Sideslip angle, and Roll angle Natural Frequency Damping Coefficient

[8]

Ghazi Georges, Développement d’une Plateforme de Simulation et d’un Pilote Automatique-Application aux Cessna Citation X et Hawker 800XP., Doctoral dissertation, Master’s thesis, University of Quebec-École Polytechnique de Montréal, Canada, 2014.

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Ghazi Georges, Botez, M. Ruxandra, Development of a High-Fidelity Simulation Model for a Research Environment. SAE AeroTech Congress and Exhibition,Seattle, WA, USA, 2015 September 9, pp. 2569.

[10]

Boughari, Yamina, et al., Optimal Flight Control on Cessna X Aircraft using Differential Evolution. International Association of Science and Technology for Development IASTED Modelling, Identification and Control (MIC 2014), Innsbruck, Austria. 2014 February 17, pp. 189-198.

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Boughari, Yamina, et al.Evolutionary Algorithms for Robust Cessna Citation X Flight Control. No. 2014-01-2166. In SAE 2014 Aerospace Systems and Technology Conference, ASTC 2014,. Cincinnati, OH, USA, September 23-25, 2014, September Vol. 2014 September.

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Ghazi, Georges, Botez, M .Ruxandra, Lateral Controller Design for the Cessna Citation X with Handling Qualities and Robustness Requirements. In 62nd Canadian Aeronautical Society Institute CASI Aeronautics Conference and AGM, Montreal, Quebec, Canada, 2015.

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Ghazi, Georges, Botez, M. Ruxandra. New Robust Control Analysis Methodology for Lynx Helicopter and Cessna Citation X Aircraft Using Guardian Maps, Genetic Algorithms and LQR Theories Combinations. In 70th American Helicopter Society International Annual Forum,. Montreal, QC, Canada May 20-22, 2014, Vol. 4, Coll. Annual Forum Proceedings – AHS International, American Helicopter Society, pp. 3138-3146.

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Hamel Clement, et al., Cessna Citation X Aircraft Global Model Identification from Flight Tests. SAE International Journal of Aerospace, vol. 6, 2013, No 1, pp. 106-114.

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Hamel Clement, et al., Cessna Citation X Airplane Grey-Box Model Identification without Preliminary Data. In SAE 2014 Aerospace Systems and Technology Conference, ASTC 2014, Cincinnati, OH, USA, September 23- 25, 2014, Vol. 2014-September.

References [1]

Fielding, Christopher, et al., Advanced techniques for clearance of flight control laws. Springer Science & Business Media; Berlin Heidelberg, Germany, 2002.

[2]

Korte, Udo, Tasks and needs of the industrial clearance process.. In Advanced Techniques for Clearance of Flight Control Laws, (Fielding, C., Varga, A., Bennani, S., Silier, M.), Springer Berlin Heidelberg,Germany 2002, pp. 13-33.

[3]

Boughari Yamina., Botez M. Ruxandra., Optimal Flight Control on the Hawker 800 XP Business Aircraft. In IECON 2012-38th Annual Conference on IEEE Industrial Electronics Society Montreal, Canada, 2012, Oct 25, pp. 5471-5476.

[4]

Goupil Philippe, Puyou Guilhem, A high fidelity AIRBUS benchmark for system fault detection and isolation and flight control law clearance. In Proceedings of the 4th European Conference for Aero-Space Sciences, EUCASS Series, Munich, Germany, 2013, Vol. 6,pp. 249-262.

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Menon, Prathyush, et al., Nonlinear Robustness Analysis of Flight Control Laws for Highly Augmented Aircraft, Control Engineering Practice Journal. Vol. 15, 2007, no. 6, pp. 655-662.

[6]

[7]

Slier Michiel, et al., New Analysis Techniques for Clearance of Flight Control Laws., AIAA Guidance, Navigation, and Control Conference and Exhibits,11-14 August, Austin ,Texas, USA, 2003, pp. 5476. Varga, Andreas, et al., Optimization Based Clearance of Flight Control Laws. Lecture Notes in

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[17]

[18]

Ghazi Georges, et al., Cessna Citation X Engine Model Identification from Flight Tests. SAE International Journal of Aerospace. Vol 8, 2015 September 15, pp. 2015-01-2390. FAA testing confirms that Citation X as world’s fastest civilian aircraft, http://newatlas.com/citation-x-faa-testingfastest-civilian-aircraft/29660/ (on line 14 January 2017). Circular, FAA Advisory. "120-40B" Airplane Simulator Qualification (1991), https://www.faa.gov/regulations_policies/advis ory_circulars/index.cfm/go/document.informati on/documentID/22762 (on line 14 January 2017).

[19]

Nelson Robert C., Flight Stability and Automatic Control, WCB/McGraw Hill, Second Edition 1998.

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Poussot-Vassal Charles, Roos Clement, Flexible Aircraft Reduced-Order LPV Model Generation from a Set of Large-Scale LTI models. In American Control Conference (ACC), 2011, June 29, pp. 745-750.

[21]

Boughari, Yamina, et al., Flight Control Clearance of the Cessna Citation X Using Evolutionary Algorithms, Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, April 2016, pp. 0954410016640821.

[22]

De Oliveira, Rafael Fernandes, et Guilhem Puyou., On the Use of Optimization for Flight Control Laws Clearance: a practical approach, IFAC Proceedings Volumes, vol. 44, 2011, No 1, pp. 9881-9886.

[23]

COFCLUO, Deliverable D 1.1.1 – Selected Clearance Problems. Part 1 Nonlinear Model, Technical Report, AIRBUS France SAS, France, 2007.

[24]

Garulli Andrea, et al., D2. 3.5 Final Report WP2. 3, Technical Report COFCLUO project, 2010, pp. 41, http://www.dii.unisi.it/~garulli/lfr_rai/D2.3.5.pd f (on line 14-01-2017).

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Bates Declan G., et al., Improved Clearance of a Flight Control Law Using µ-Analysis Techniques,

Journal of Guidance, Control and Dynamics, Vol. 26, 2003, No 6, pp. 869-884. [26]

Mack L. M., Linear Stability Theory and the Problem of Supersonic Boundary – Layer Transition, AIAA journal. 1975, Vol 13, No 3, pp. 278-289.

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Anton, Nicoleta, Botez, Ruxandra M., Weight Functions Method for Stability Analysis applied as Design Tool for Hawker 800XP Aircraft, The Aeronautical Journal, Vol. 119, 2015, No 1218, pp. 981-999.

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Anton, Nicoleta, et al., Application of the Weight Function Method on a High Incidence Research Aircraft Model, The Aeronautical Journal, Vol. 117, 2013, No 1195, pp. 897-912.

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Stevens, Brian L., et al.,. Aircraft Control and Simulation: Dynamics, Controls, Design and Autonomous Systems. Wiley Blackwell, 2015.

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Garulli, Andrea, et al., LFR RAI User’s Guide, 2015. LFR RAI User’s Guide, Technical Report. Coll. Tech. Rep: DII, Universit`a di Siena, Via Roma 56, 53100 Siena, Italy, pp. 21, http://www.dii.unisi.it/~garulli/lfr_rai/lfr_rai_us ers_guide.pdf (on line 14-01-2017)

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DOI: 10.14621/ce.20170103

Specifics of Switch-Gear Capacity Fault Analysis of Kosovo Power System Substations by Comparative Analytical and Numerical Software Methodology Gazmend Pula*, Kadri Kadriu, Gazmend Kabashi, Bajram Neshati Faculty of Electrical and Computer Engineering, University of Prishtina 10000 Prishtina, Kosovo; fiek@uni-pr.edu

Abstract

1. Introduction

This paper deals with short circuit fault analysis for checking out and determining the adequacy of the power switchgear capacity following changes in network configuration for a given power system substation facility under assumed worst case scenarios of fault occurrences. Namely, changes in the configuration of the power system alter both the short circuit levels and short circuit currents in the system. Hence when any major modifications to the power system are made, these computations must be repeated to determine the adequacy of the protective equipment [1] i.e. circuit breaker switchgear. The case study analyses a typical substation facility of the Kosovo Power System (KPS) with short circuit fault calculations for the analysed busbar have been carried out in order to establish whether fault currents exceed the earlier installed switchgear/circuit breaker capacity following more significant changes in network configuration. Functional performance of power circuit breakers have been checked out in view of this for an entire sequence of symmetrical and unsymmetrical short circuit fault in order to avoid equipment failure i.e. related dynamic or thermal equipment damage in a typical power system substation with two modes of operations.

The demand for electric power consumption continues to increase globally with no significant saturation trend in sight. In order to meet this demand appropriately a continuous increase in generation, transmission and distribution facility capacities are necessary. Therefore, every year many more power stations, substations and transmission lines are added to thus permanently expanding power systems. These changes in the configuration of the power system alter increase short circuit fault levels and short circuit fault currents in the system [1]. Hence the installation of appropriately dimensioned switchgear for protection and control of the network that can withstand possible major fault occurrences and power disruptions. It is therefore important to determine the values of system voltages and currents during faults short circuit conditions so that protective devices may be set to minimize the harmful effects of such contingencies [2]. The proper coordination of protective relays and the correct specification of circuit breaker rating are based on the result of such fault calculations and analysis [3].

The analysis is carried out by simulating the full range of short-circuit faults with emphasis on the three-phase and single-line-to-ground faults. The fault calculations for the analysed case study have been carried out with different fault methodologies i.e. by application of the power system software packages such PSS/E, the MATLAB as well as the classical analytical Thevenin method. The results obtained are used also for a establishing a practical applicative methodology of switchgear check-out thru an easier applicable preliminary fault analysis. A comprehensive assessment pertaining to the adequacy of the switchgear is then made based on a parallel and comprehensive fault analysis with different comparative methodologies and levels of calculation accuracy for determining accurately switchgear ratings as applied also in the KPS.

Keywords:

Adequacy of switchgear capacity; Circuit breaker; Comparative fault analysis; Short circuit fault current, Power system

Article history:

Received: 27 January 2016 Revised: 30 October 2016 24/30 January 2017 Accepted: 31 January 2017

The probability and gravity of major network faults and ensuing disruptions increases proportionally with network enlargement and complexity that result in increasing fault levels i.e. fault currents. Hence fault currents have to be kept in check with appropriately rated protective switchgear in order to minimize potentially serious permanent equipment and network damage. Network faults can strike in various forms and gravities. The ones that are accompanied with manifold larger currents and fault levels than the near-nominal load ones are short circuit fault currents, the gravest being usually those of 3-phase faults and in certain cases also line-to-ground faults [4]. Fortunately 3-phase faults are the simplest ones for calculation, analytically and numerically, due to their inherent fault symmetry.

___________________________________________________________________________________________________________ G. Pula, K. Kadriu, G. Kabashi, B. Neshati: “Specifics of Switch-Gear Capacity Fault Analysis of Kosovo Power System Substations …”, pp. 19–28

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The line-to-ground (L -G) faults, which by the same token are the most frequent and most complex for calculation, statistically reach the highest incidence of occurrence of some 70% of the overall number of short circuit faults. The line-to-line (L-L) faults have an incidence of ca. 15%, line-to-line-to-ground (L-to-L-to-G) faults stand at ca. 10%, whilst the incidence of the 3-phase faults stands at some 5% of such fault occurrences [5]. The 3-phase short circuit occur rarely but it is the most severe type of fault involving largest fault currents and fault levels. For this reasons this symmetrical short circuit calculation is performed to determine the largest currents to determine the rating of circuit breaker switchgear [1] despite the fact that L-to-G faults sometimes reach somewhat higher values in certain circumstances i.e. when they occur in the vicinity of synchronous generators.

Figure 1. Single-line diagram of the faulted substation SP

Table 1: Transformer data1

2. Case study The case study for the analysis is taken to be the Kosovo Power System respectively its Substation Podujevo (SP) of rated capacity 2x40 MVA and 220/35/10 kV with the one-line diagram shown below in Figure 1. Fault calculations provide information on currents and voltages of a power system during short circuit fault conditions. For the purpose of the comparative fault analysis a sequence of typical faults are applied on the mentioned substation busbars connecting its two parallel power transformers as shown in Fig.2. The sequence of faults applied consists of all the four standard types of short circuits mentioned above affecting all its 220/35/10 kV busbars. The fault points at all of its three-voltage levels are symbolically noted with F1, F2, F3 and F4 as shown in Figure 2.

TR1

TR2

Sn [MVA]

Vp [kV]

220

Vs [kV]

36.75

10.5

Vt [kV]

10.5

Regulation [%]

±12x1.25

Connection group

YNyn0 d5

YNyn0 (d5)

uk-HV-MV [%]

10.97

15.41

uk-HV-LV [%]

15.29

PcuHV-MV [kW]

178

181

Pcu HV-LV [kW]

187

Pfe [kW]

i0 [%]

0.2

The two parallel power transformers TR1 and TR2 of the analysed substation are: A three-winding transformer 220/35/10(20) kV with rated capacity 40 MVA, and a two-winding one 220/10 kV of the same rating. Their relevant data are given in Table 1 below. Note: uk not available N/A for HV-LV level for TR2 – values taken from manufacturer’s data.

represented interconnected integrated real regional power system.

3. Fault analysis with PSS/E program package

The three-winding transformer TR1 and the TR2 have been appropriately modelled as such in the PSS/E. The 10 kV windings of both transformers have both delta windings d5.

The initial calculation of short circuit fault currents for the purpose of providing for the study case of the comparative analysis for the sequence of fault occurrence analysis for the SP substation was carried out with the highly accurate large scale industrial PSS/E program package. Upstream boundary conditions of the system are simulated with the actual fully accurately

3.1. Fault calculation – Substation power transformers in non-parallel mode of operation

The obtained results from the same series of fault simulations consisting of Line-to-Ground fault (L-G), Line-to-Line (L-L), Line-to-Line-to-Ground (L-L-G) and 3Phase (3-PH) faults are presented as given in Tables 2 and 3.

Subscripts of data transformer table (n, p, s, t, k, Cu, Fe, o) voltage, copper and iron losses and transformer magnetizing pertain to nominal, primary, secondary, tertiary, short circuit current respectively. ___________________________________________________________________________________________________________ G. Pula, K. Kadriu, G. Kabashi, B. Neshati: “Specifics of Switch-Gear Capacity Fault Analysis of Kosovo Power System Substations …”, pp. 19–28

International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

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Figure 2. Single-line diagram of the Kosovo Power System

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International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

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Table 2: Non-parallel mode of operation – fault currents BUS 220 kV (F1) 35 kV (F3) 10 kV-T1 (F2) 10 kV-T2 (F4)

L-G [AMP] 6005.8

L-L [AMP] 7052.4

L-L-G [AMP] 4769.7

3-PH [AMP] 8165.9

303.9

3827.9

152.8

4421.1

0.0

17676.8

0.0

20417.7

0.0

15398.6

0.0

17785.6

Table 3: Non-parallel mode of operation – fault powers BUS

L-G [MVA]

L-L [MVA]

L-L-G [MVA]

3-PH [MVA]

220 kV (F1)

2288.53

2687.32

1818.00

3111.64

35 kV (F3)

18.42

232.05

9.26

268.11

0.00

306.17

0.00

353.64

0.00

266.71

0.00

308.06

10 kV-T1 (F2) 10 kV-T2 (F4)

From the results obtained other indicators of fault currents can be observed such as the dynamic currents, which taken as peak values are: Idyn2 = Ipeak = 11.8091 kA for the 3-phase faults and Idyn = Ipeak = 0.4384 kA for the single-phase faults. This peak current would be taken as meritory for the short circuit Making3 Current of the circuit breaker as opposed to the short circuit Breaking Current for which meritory is the symmetric steady state short circuit current. Depending on the X/R ratio i.e. the DC component of the short circuit current the Making current can be up to 2.5 times the Breaking current despite its extremely short duration of half a cycle i.e. ca. 5 msec. Hence the dc component is also calculated for the entire series of the faults applied and stands at: Idc = 1.7223 kA. The related Breaking Current i.e. the Breaking Capacity of the switchgear is taking into account most frequently when fault calculations for circuit breaker capacity are determined for fault points in close electrical proximity to synchronous generators which would significantly increase the Breaking Capacity of the switchgear. As the duration of the peak dynamic short circuit i.e. asymmetric maximal momentary current is half a cycle i.e. 5 milliseconds that no protective relay can react within such an instantaneous time frame, no significant thermal effect can take place within the half cycle,

especially as the substations not in electrical proximity of synchronous generators the Breaking capacity of the circuit breakers has been taken as meritory rather than the Making capacity. Power switchgear capacity for the 220 kV voltage level stands at Ik3=40 kA, for the 35 kV one at Ik3=25 kA, while for the 10 kV stands at Ik3=25 kA. From the results obtained and the installed power switchgear capacity nominal ratings, it can be clearly seen that for the nonparallel transformer mode of operation of the Podujevo substation, which is a critical one in the KPS in this respect, fault currents pose no danger of exceeding switchgear power rating and hence no damage can result even in the worst case scenario. In other words the analysed installed switchgear provides a sufficient safety margin for their respective power ratings. This mode of operation is the standard mode applied in KPS substations [6].

3.2. Fault calculation – Substation power transformers in parallel mode of operation The case of parallel mode of operation of the two power transformers of the substation, as the worst-case scenario i.e. mode of operation of the substation has also been subjected to the entire series of faults at F1, F2, F3 and F4 for the comparative analysis. The obtained results have been presented as given in Tables 4 and 5. From the results obtained from the fault simulation at F2 for the case of the parallel mode of operation of the two substation transformers, it can be seen that the fault current Ik3= 34.573 kA clearly exceeds the rated maximal switchgear capacity, which for the 10 kV voltage level stands at 25 kA. Hence if such a fault occurs for the parallel mode of transformer operation the switchgear equipment would not have the required rating i.e. capacity to withstand this fault current and hence permanent equipment damage, thermal and/or mechanical and possibly even personnel damage would be caused as well as a power system disruption. Such a surge increase of the fault current close to being coupled (precisely 70% increase i.e. from 20.4 kA to 34.5 kA) for the 3-phase fault at the fault point F2 of the 10 kV voltage level for the parallel mode of operation of the two substation transformers, as compared with the same fault current for the non-parallel mode of operation. This is obviously due to the approximate

Subscripts of data transformer table (dyn, peak, dc, k3) Interrupting (Breaking) Current. Symmetrical short-circuit pertain to dynamic, peak, direct and 3-phase short circuit current is obtained by using subtransient-reactance for currents respectively. synchronous machines, while Momentary (breaking) currents 3 The two ratings of the circuit breaker which require the (RMS) is then calculated by multiplying the symmetrical calculations of the short- circuit currents are: Rated current by a factor of 1.6 to account for DC offset component Momentary (Making) Current & Rated Symmetrical current [1]. ___________________________________________________________________________________________________________ G. Pula, K. Kadriu, G. Kabashi, B. Neshati: “Specifics of Switch-Gear Capacity Fault Analysis of Kosovo Power System Substations …”, pp. 19–28

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Table 4: Parallel mode of operation – fault currents BUS

L-G [AMP]

L-L [AMP]

L-L-G [AMP]

3-PH [AMP]

220 kV (F1)

6005.8

7052.3

4769.6

8165.8

35 kV (F3)

304.6

5618.7

152.9

6490.1

0.0

29925.5

0.0

34573.0

0.0

29925.5

0.0

34573.0

10 kV-T1 (F2) . 10 kV-T2 (F4)

Table 5: Parallel mode of operation – fault currents BUS

L-G [AMP]

L-L [AMP]

L-L-G [AMP]

3-PH [AMP]

220 kV (F1)

2288,52

2687.30

1817.48

3111,59

35 kV (F3)

18,46

340.61

9,27

393.44

0.00

518.32

0.00

598.82

0.00

518.32

0.00

598,82

10 kV-T1 (F2) 10 kV-T2 (F4)

halving of the equivalent substation reactance resulting from the parallel connection/operation of the two transformers (see Figure 1) can be technically implemented within a transient-transfer time frame of 60 sec. by SCADA-activated 10 kV bus-coupler switch. Nevertheless the optional parallel connection of the two transformers thru the 10 kV as shown in Figure 1 for the given ratings of the installed switch gear of 25 kA is provided for as an N-1 criterion emergency operating option for the case of an outage of any of the two substation transformers. In such a case the transformer

remaining in operation would be able to overtake and supply the consumers on both groups of 10 kV feeders irrespective of the outage of the parallel one as both transformers have the rating to cover the entire substation load separately and currently without even reaching full-load condition This substation full redundancy capacity that provides for the fulfilment of N-1 criterion is system code policy applied in all major KPS substations [6-7, 10]. Alternatively, should the two substation transformer been allowed to operate in parallel the circuit breaker switchgear rating would have needed to be enhanced from the 25 kA class rating to the 40 kA class rating to provide the respective breaking capacity for the 3-phase current of 34.5 kA, along with other downstream ones other facilities compromising the comparable costeffectiveness of the solution.

4. Fault calculations with the MATLAB program package The same series of fault analysis for the case study was carried out with the application of the MATLAB software. The respective equivalent schematic Mat/Lab block diagram of the KPS as presented in Figure 3. The entire spectra of faults analysis mentioned before was carried out for both two modes of operation of the substation i.e. the non-parallel and the parallel mode of operation. In other words for the two substation transformers operating independently, whilst the other case being the two substation transformers operating in parallel mode thru the interconnecting power buscoupler 10 kV closed (see Figure 2). The respective equivalent schematic MATLAB block diagram is presented in Figure 4. The two inter–connected 220 kV

Figure 3. Schematic Matlab/Simulink block diagram for the fault analysis – case of non-parallel mode of operation – transformer inter-connecting power link switch open ___________________________________________________________________________________________________________ G. Pula, K. Kadriu, G. Kabashi, B. Neshati: “Specifics of Switch-Gear Capacity Fault Analysis of Kosovo Power System Substations …”, pp. 19–28

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Figure 4. Schematic Matlab/Simulink block diagram for the fault analysis – case of parallel mode of operation – transformer inter-connecting power link switch closed

network systems have same fault levels (of 15.000 MVA) respectively finite bus external impedances Xe1.2. In order to calculate the sub-transient fault current or the initial symmetrical current for a 3-phase short circuit in a power system, the following assumptions are made for the simplicity of calculations: • Transformers represented by their leakage reactances; • Transmission lines represented by their equivalent series reactances; • Synchronous machines are represented by constant voltage sources behind sub-transient reactances; • Non-rotating (dynamic4) impedance load are neglected; • Rotating (dynamic) loads are neglected or if of larger ratings then represented by constant voltage transient reactance. In the case study analysed and for reasons of a solid base for a greater accuracy of the comparative short circuit fault analysis the two parallel substation transformers have been represented with “T” equivalent scheme meaning with the included shunt impedance. Dynamic loads have been neglected and after the power transformer data in per unit have been fed into

respective schematic blocks including the 220 kV network parameters the simulations have been carried out for the faults occurring at 0.2+ sec. and being cleared at 0.4 sec, with simulation time extending to 0.5 sec. as in the previous analytical calculation. The obtained results have been graphically presented for the case of the 3-phase fault occurring at F4 for the non-parallel mode of operation of the two substation transformers. As can be seen in the Figure 5 below, all the three fault regimes i.e. the sub-transient, transient and the stationary ones are clearly discernible. Relevant for our comparative analysis is however the stationary 3-phase fault current observed to stand at 17.1 kA rms as shown in Figure 5 in a time-current coordinate system below, while standing at 17.7856 kA rms when simulated by the PSS/E (see Table 2). Figure 6 below shows the 3-phase rms voltage curve in a time-voltage coordinate system before, during and after the fault occurrence is cleared. Figure 7 below shows the stationary 3-phase fault occurring at F2 for the parallel mode of operation of substation transformers standing at 33.750 kA rms, as compared to 34.573 kA rms when simulated by the PSS/E (see Table 4). In Table 6 and Table 7 rms values for fault currents have been presented for the line-to-ground fault, line-to-line one and for the 3-phase faults at F1, F2, F3 and F4 for the two case studies analysed.

In the case analyzed the contribution of dynamic loads significant power rating downstream, nor are there any further downstream are neglected as there are hardly any of sizable motor-load industry facilities [8]. ___________________________________________________________________________________________________________ G. Pula, K. Kadriu, G. Kabashi, B. Neshati: “Specifics of Switch-Gear Capacity Fault Analysis of Kosovo Power System Substations …”, pp. 19–28

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Figure 5. Fault current sec. for the 3-phase fault occurring at F4, case of non-parallel mode of transformer operation

Figure 6. 3-phase fault rms voltage curve before, during and after the fault occurrence at F4 case of non-parallel mode of transformer operation

Figure 7. 3-Phase fault current at F2 for parallel mode of transformer operation ___________________________________________________________________________________________________________ G. Pula, K. Kadriu, G. Kabashi, B. Neshati: “Specifics of Switch-Gear Capacity Fault Analysis of Kosovo Power System Substations …”, pp. 19–28

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Table 6: Non-parallel mode of operation – fault currents L-G [AMP]

BUS

L-L [AMP]

3-PH [AMP]

220 kV

(F1)

6750

7238

8360

35 kV

(F3)

313

3861

4440

10 kV-T1

(F2)

0.0189

17491

20080

10 kV-T2

(F4)

0.0189

14870

17100

admittances of the power network have been neglected for the simplicity and transparency of calculation. For the assumed 3-phase fault at F3 the same two interconnected network reactances (Xe1 and Xe2) have been calculated, whilst the TR1 and TR2 transformer reactances (XA, XB and XC) have been calculated as below and schematically presented as in Figure 8. =

∙

= 1.0273 [Ω]

(1)

where m is transformer ratio. Table 5: Parallel mode of operation – fault currents = L-G [AMP]

BUS

L-L [AMP]

3-PH [AMP]

220 kV

(F1)

6766,20

7215

8355

35 kV

(F3)

313.85

4494

5169

10 kV-T1

(F2)

0.0189

29010

33750

10 kV-T2

(F4)

0.0189

29010

33750

∙

= 5.203 [Ω]

(2)

For TR1 the reactances are calculated as below: = ∙

−

= 3.852 [Ω]

(3)

= ∙

−

= − 0.149[Ω]

(4)

= ∙

−

= 1.3101 [Ω]

(5)

With the equivalent reactance being: = 4.21755 [Ω] From Figure 8 the three-phase fault current can be calculated to be: =

Figure 8. Equivalent Thevenin scheme

5. Analytical fault calculation For the analytical i.e. the Thevenin method of fault calculations, the fault types analysed were taken to be the 3-phase fault and the single-phase one for the two modes of transformer operation the non-parallel and the parallel one. Most of the cases of short-circuit calculation is a simple E/X calculation (E being the circuit operating voltage and X the equivalent reactance) if X/R is 15 or less [9].

5.1. Phase fault calculation The power system elements are represented with their equivalent reactances calculated as reduced at the faulted–busbar voltage level. The line resistances and

∙

√ ∙ ∙ .

∙

=− ∙ .

[

]

(6)

The three-phase fault current F3 calculated by the PSS/E stands at 4.4211 kA rms and by MATLAB at 4.44 kA rms, thus resulting in less than 1% relative difference i.e. accuracy deviation between the two applied software methods. However the accuracy deviation between the PSSE/E method and the analytically calculated one by the Thevenin equivalent as presented above has resulted in an accuracy deviation of 25.2% and 22.5% respectively.

5.2. Line-to-Ground fault calculation The L-G fault is assumed to have occurred at F3 on the 35 kV busbar of TR1. For the analytical calculation the approximation included taking into account only the grounding resistance Rg as the other reactances are significantly lower than the Rg, with c=1.1, where c represents the voltage security margin according to the IEC standard. The respective Thevenin equivalent schemes as established for the direct, inverse and zero sequences are presented as in Figure 9:

International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

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two numerical computer methods i.e. power system software packages have been applied along with the classic analytical Therein equivalent method and the results obtained have been subjected to a comparative analysis. Numerical software packages used were PSS/E and the MATLAB based on the IEC standards).

Figure 9. Network equivalent schemes for d, i, o sequences

Hence =

∙

(7)

∙

In the expression above Rg represents the grounding resistance installed for limiting (asymmetric) fault currents. The grounding resistance Rg is very large compared to other components of the denominator of the expression which are therefore negligible. Hence ≅

∙

(8)

∙

than =3∙ =3∙

∙ ∙

1.1 ∙ 36,75 √3 ∙ 70

=−

= .

[ ]

(9)

As the single-phase fault current F3 calculated by means of the PSS/E stood 303.9 A rms, while the one resulting from the MATLAB stood at 313 A rms, the relative difference i.e. accuracy deviation between them standing at only 2.99%. However the accuracy deviation between the PSS/E method and the analytically calculated one by the Thevenin equivalent as above has resulted in an accuracy deviation of 9.7% and 3.1% respectively.

6. Conclusion This paper has carried out a comparative fault analysis of a crucial substation of the KPS for checking out the adequacy of the installed switchgear ratings applying the three short-circuit calculation methods most frequently used in power system fault calculations. Thus

By comparing the fault power levels Sk of the KPS substation taken as case study subjected to a full sequence of possible short-circuit types with the rated power capacity of the installed switchgear, this paper concludes that the two power parallel transformers of the substation may not be allowed to operate in parallel mode at the 10 kV voltage due to the fault levels exceeding the rated installed switchgear capacity. The KPS transmission operator Electrical Equipment Codebased policy implemented in all of its major the substations is that its transformers operate independently and not in parallel. This due to severely increased potential fault currents in case of their parallel mode of operation as presented above and so that the fulfilment the N-1 criterion for all major substation as an emergency operating option i provide for. Namely that for the case of an outage of any of the two substation transformers, the remaining one in operation would be able to cover the entire substation load of both 10 kV feeder groups separately irrespective of the outage of the other one. This substation full redundancy capacity that provides for the fulfilment of N-1 criterion is system code policy applied in all major KPS substations. Along this line it can be concluded from the analysis that an occurrence of a severe fault in case of a parallel operation mode would put at risk all of the 10 kV feeder circuit breakers. Alternatively, a parallel transformer mode of operation, if needed for the substation and the system, could be permitted only if all the installed 25 kA power circuit breakers would be replaced by a higher class of capacity ratings of 40 kA on practically all 10 kV feeders thus providing the required power capacity redundancy for such contingencies. Such an approach would clearly entail a significant costs increase for the respective system operator, as the next higher class of switchgear power capacity are significantly more expensive. There we arrive at the necessity of determining the compromise cross point between the economic and the functional technical aspect of the power system i.e. substation operation. It is important to conclude also that the comparative fault calculation analysis presented in this paper clearly indicates that thorough fault analysis of power system are simply indispensable periodically as system expands and its configuration changes. Namely as the system expands and the fault levels increase this necessarily imposes respective periodic check-outs and verification of the adequacy of the installed switchgear ratings/

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capacities. Therefore application of more practical and simpler fault calculation methods as the Thevenin classical method can be efficiently applied for preliminary purposes and assessments. Namely they can provide sufficient accuracy for the purpose rather than applying accurate but exhaustive power system software methods posing significant computational time and capacity requirements. The comparative analysis carried out on the case study has concluded that a preliminary assessment of fault current levels with an acceptable accuracy range deviation of 10-25% can be achieved also with the simple classical Thevenin method and/or the MATLAB application as compared to the elaborate and sophisticated software packages such as the PSS/E. However this would be applied primarily for the purpose of a preliminary and educated assessment of fault levels and fault currents.

[3]

Yamayee Z., Fala R., Electromechanical Energy Devices and Power Systems, Wiley, Sew York, 1994, pp. 384-386.

[4]

Saadat H., Power System Analysis, 3rd ed., McGraw-Hill Book Company, Boston, 2013.

[5]

Pula G., Transmission and Distribution of El. Energy, ETMM, Prishtina, 1983.

[6]

KOSTT Kosovo System Transmission and Market Operator, Electrical Equipment code, Prishtina, 2013, www.kostt.com

[7]

Kosovo Power System Transmission Development Plan 2014–2023, KOSTT, Prishtina, 2014, www.kostt.com

[8]

Kaloudas Ch., Papadopoulos P, Short Circuit Analysis of an Isolated Generator and Comparative Study of IEC, ANSI and Dynamic Simulation, 7th MedPower Conference, 7-10 Nov. 2010, A. Napa, Cyprus (paper # MED 10/195).

[9]

Prachal J., Abhijeet S., Effects of DC Components on Circuit Breaker, International Journal of Science and Research IJSR, Vol 4, Issue 10, October 2015, www.ijsr.net

[10]

Pula G.,Kadriu K., Kabashi G., Sadiku V. “LongTerm Enhancement of the Operational Security of the Kosovo Power System by Applying Augumented Deterministic Methodology”, IEEE Xplorer, SAI Conference, London, UK, July 28-30, 2015, pp. 1266-1271.

References [1]

[2]

Gagandeep K., Amandeep S., Selection of Circuit Breaker Rating for Symmetrical Fault Analysis on Transmission Lines, International Journal of Science and Research IJRT, Volume 4, Issue 4, April 2015, www.ijsr.net Kakilli A., System Analysis with the MVA Method for Symmetrical Three-Phase Faults, TEM Journal – Volume 2, No.1, 2013, pp. 51-56, www.temjournal.com

International Journal of Contemporary ENERGY, Vol. 3, No. 1 (2017)

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DOI: 10.14621/ce.20170104

Impacts of Non-Programmable Renewable Sources Penetration on the Italian Energy System: A Tool for Scenario Analyses Daniele Grosso*, Raffaella Gerboni, Aquiles Martínez Pérez Politecnico di Torino, Energy Department (DENERG) Corso Duca degli Abruzzi 24, 10129 Torino, Italia; daniele.grosso@polito.it

Abstract

1. Introduction

The penetration of renewable sources in the national energy mix is necessary for most of the industrialised countries in order to comply with the ever-challenging constraints imposed by environmental impact reduction policies. However, a big family of renewable sources have the peculiarity of being non-programmable, that is very variable throughout hours and seasons. While the traditional electrical grid management philosophy has always been oriented towards the timely fulfilment of the demand via a set of conventional uninterruptible (or hardly so) large power plants complemented with a set of quickly adjustable smaller power plants, the integration of non-programmable renewable (NPR) power plants may represent a challenge. The planning of this kind of plants has to be accurately assessed as an over-installation may result in an overproduction of electricity that the existing electrical network cannot be able to transmit and the system to absorb. The paper presents a tool, inspired by previous NREL studies, to evaluate the effects of the penetration of NPR sources in the Italian energy mix. The study starts from the definition of the load profile of the country and it assesses the percentage of load that can be fulfilled by NPR sources until possible, taking into account the un-flexibilities of the electrical system, mainly due to the base load power plants that can hardly be adjusted. If more NPR electricity is instantly produced, this represents a waste (of energy and money). Thanks to the developed tool, a set of possible scenarios for the different geographical areas of Italy are presented and discussed, focusing in particular on the increase in the flexibility of the electrical system and in the penetration rate of NPRS.

The penetration of renewable sources in the energy mix of a country is more and more necessary to comply with the constraints and targets set by environmental impact reduction policies. However, renewable sources (in particular wind and photovoltaic) have the peculiarity of being variable throughout hours and seasons and, as a consequence, they can be considered nonprogrammable (Non-Programmable Renewable Sources, NPRS). This fact originates several issues related to their integration, that can be clearly understood by analysing the structure of the traditional power systems and their management, mostly focused on conventional (and almost uninterruptable) large plants for covering the base load and adjustable smaller plants for the peak coverage.

Keywords:

Non-programmable renewable sources; Electrical grid; Energy mix; Capacity; Storage

Article history:

Received: 02 May 2016 Revised: 12 January 2017 Accepted: 20 January 2017

Considering the studies already available in the scientific literature, it can be noticed that a large number of authors highlight the need for quantitatively evaluating the impacts on the power system of an increasing penetration of NPRS. This is due to the inflexibility of the system itself and to the necessity of additional solutions in order to allow large penetration rates avoiding relevant excess of NPRS production. Among these studies, the one carried out by Denholm et at. [1] can be mentioned. In particular, it focuses on the assessment of the effects of solar photovoltaic (PV) on the ERCOT (Electric Reliability Council of Texas) power system, performed by simulating scenarios in which up to 50% of the system energy is produced by PV. Several options in order to avoid the limitations related to the integration of significant amount of PV have been considered. The authors highlighted that an increase in system flexibility is crucial to ensure a relevant integration; however, additional actions are needed to manage the excess of PV production, especially during non-summer seasons. For this purpose, the potential

___________________________________________________________________________________________________________ D. Grosso, R. Gerboni, A. Martinez Perez: “Impacts of Non-Programmable Renewable Sources Penetration on the Italian …”, pp. 29–36

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contribution given by load shifting and energy storages has been explored. Denholm et al. [2] also performed further simulations on the ERCOT grid to analyse the system variations corresponding to scenarios in which different mixes of solar PV, concentrating solar power (CSP) and wind are able to satisfy up to 80% of the electricity demand, under the hypothesis that the ERCOT system cannot exchange power with other grids. The results show that an increase in flexibility allows NPRS penetration rates up to 50% with curtailments lower than 10%; if a penetration rate of 80% is requested, the increase in flexibility is not sufficient by itself but a combination of storage systems (both electrical and thermal) and load shifting is needed. Denholm et al. [3] in a technical report of the National Renewable Energy Laboratory (NREL) also stress the economic issues related to the increase in NPRS penetration, including the integration costs of NPRS and the evaluation of the maximum NPRS penetration before storages become the most economic alternative for further increase. This study also underlined the opportunity of performing optimisation analyses (i.e. of finding the system configuration that corresponds to the minimum cost) and cost/benefits analyses related to the storage systems. Referring to works carried out by other authors, the one of Kirby et al. [4] still focused on the US power system, and in particular on the modification of the operating reserve policies caused by the increase in the penetration of NPRS. It highlights the need for these operating reserve requirements to become dynamic, particularly considering the possible relevant level of penetration that NPRS could reach in the future. As the NPRS issue arises in selected geographical areas where the potential is high, it is interesting to mention the work of Solomon et al. [5], who analysed and quantified the effects on the Israeli power system of the integration of very large-scale photovoltaic plants (VLSPV). They underlined that this quantification is important to help planners in finding the optimal siting of VLS-PV plants and the best technological option to adopt and in defining future grid expansion strategies able to take into account the need for increasing flexibility (in anticipation of a possible increase in NPRS penetration). Focusing again on the Israeli power system, Fakhouri et al. [6] based their analysis on the Government’s target of a NPRS penetration equal to 10% by 2020, evaluating the need for backup in the system, also considering that Israel – from an electrical point of view – is a closed market, i.e. an electricity island. Like many of the previously mentioned studies, this work shows that an increase in NPRS penetration rate has to be coupled with

an increase in flexibility of the system and with the implementation of options like storages in a framework of a smart management of the network in order to ensure quality and reliability of the electricity supply. Erdinc et al. [7] underlined the additional critical issues that a high penetration of NPRS in power generation could cause in insular electric systems, which usually suffer from a structural fragility in comparison with the continental ones. This weakness is mostly due to the low number of interconnections with the main grid and the small size of the local networks (with a low number of generators causing a low inertia of the systems and relevant sensibility to possible outages). Oree et al. [8] show the need for considering the variability and intermittency of the NPRS in planning techniques (commonly based on least-cost optimisation or, more recently, on multi-criteria methodologies), critically analysing the models and methodological approaches currently available in the scientific literature. Ulbig et al. [9] proposed modelling techniques to describe and evaluate the operational flexibility of individual power system units and of clustering of several power system units. Franco et al. [10] focused on some possible scenarios able to ensure an optimal NPRS penetration in the Italian energy system. The authors underlined that an increase in renewable penetration could be effective in reducing the consumption of fossil fuels (in particular natural gas for power generation), thus enhancing the energy security level of the Country (contributing to decrease the relevant dependency on import of fossil commodities). They also suggested that the increase in CHP plants and electric vehicles could promote the integration of wind and photovoltaic power. They further highlighted the possible issues deriving from the distance between large hydropower plants (mainly located in the North) and wind farm (mainly located in the South), which could impede the implementation of a wind and water model helpful in controlling the power intermittency. Still referring to an Italian case study, the study performed by Barelli et al. [11] can be mentioned. In this work, the authors focused on a peculiar issue of the Italian power system, i.e. the effect of the renewables penetration on the thermoelectric production. In fact, policy strategies aiming at promoting renewable sources penetration (especially photovoltaic) implemented in the period 2007-2013, the concurrent absence of additional actions to optimise their integration in the power system and the higher cost of natural gas, with respect to coal, led to the use of gas combined cycle (CC) plants as backup for renewable plants and no more as base-load plants, thus causing a decrease in the thermal

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generation efficiency, mechanical stresses on the CC plants and an increase in the related maintenance costs. In order to overcome this problem – as alternative solution to the retrofitting of the existing power plants – the authors suggested the integration between energy storage systems and large CC plants, allowing them to operate again close to the nominal conditions (with relevant benefits from the efficiency point of view), by storing the produced energy surplus.

consumed because it exceeds the instantaneous flexibility of the system, i.e. the difference between the instantaneous load and the minimum output power of the other plants belonging to the analysed system. This minimum power is defined inflexibility (Figure 1) and corresponds to the threshold below which the production of the base load plants has to be modified, often causing the shutdown of certain units in order to avoid damages.

Eventually Gullì et al. [12] and Bigerna et al. [13] analysed the economical and market aspects related to the enhancement of renewables penetration in Italy. Gullì et al. evaluated the impact of photovoltaic power generation on the wholesale electricity prices: they showed that an increase in production from PV could lead to non-univocal effects on the price. Bigerna et al. studied the influence of RES penetration on the possible contagion effect among the six regional electricity markets in which Italy is divided (North, Center-North, Center-South, South, Sicily and Sardinia) as a consequence of a shock in a certain market: they demonstrated that evidences of an increase in such effects caused by renewables penetration cannot be found.

Starting from the load profile and the NPRS production profile, the net load is evaluated as the difference between the hourly load of the considered system and the hourly production from NPRS. As a consequence, the obtained profile corresponds to the load that has to be covered by base-load units, load-following units and peak shaving units. If the net load is lower than the inflexibility value, the surplus of energy produced by NPRS plants cannot be instantaneously consumed: if storage systems are available, it could be stored and used later, otherwise some NPRS plants have to be disconnected from the grid.

2.1. Data

Starting from these studies and findings, the goal of this work is to analyse the Italian power system, which can be considered an interesting case study due to its peculiarities. The analysis of the NPRS effects on the Italian electrical transmission grid under different penetration rates and flexibility levels is performed by developing a tool based on the NREL approach methodology [3]. The penetration rates proposed are assumed in order to verify the sensitivity of the present system.

To proceed with the analysis, input data were collected from the Italian grid operator, Terna, which, in a dedicated section of its website [14], provides access to data related to load, generation and transmission profiles. Figure 2 shows values of hourly load and NPRS generation retrieved on Terna database for a representative day in 2013 (January 3rd). To prepare this figure, data were summed up for the different Italian areas and the NPRS production has been assumed equal to the sum of wind and photovoltaic electricity production. Later in the analysis, the different geographical areas were kept separated to allow a more structured analysis.

2. Methodology The adopted approach aims to calculate the percentage of energy produced by NPRS that cannot be immediately

Power [GW]

Italy 30 Load Production from FRNP Load - Production from FRNP

20 10 0 0

10 12 14 16 18 20 22

Hours Figure 1. Definition of Flexibility / Inflexibility in an electric system

Figure 2. Typical load and NPRS generation profile for a sample day (January 3rd, 2013) [14]

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• Annual load and NPRS production in each area:

∗∑

Starting from an Excel template including data on the hourly load, the hourly wind and photovoltaic production (expressed in GW) in 2013 for several Italian areas (corresponding to the regional market zones mentioned in Section 1), the algorithm firstly calculates the following parameters: • Electricity production from NPRS for each hour in all the considered areas: NPRS production (h, z) = PV production(h, z) + Wind production (h, z) [GW]

(1)

where: h =

hour (ranging over the year)

z =

ID of the geographical area

1 ∗ 1000 (4)

• Percentage contribution given by NPRS to the total load in each area: NPRS contribution (z) =

( )

∗ 100 [%]

(5)

• Peak load and minimum load: Peak load (z) = max Load(h, z) [GW]

(6)

Minimum load(z) = min Load(h, z) [GW]

(7)

• Minimum flexibility factor of the system: (z) =

FF =

( )

∗ 100 [%]

(8)

NPRS penetration and Flexibility Factor For each geographical area, the annual quantity of energy produced by NPRS that cannot be instantaneously consumed is evaluated as a function of the imposed NPRS penetration and of the Flexibility Factor of the system. First of all, the factor K is defined as the ratio between the imposed NPRS penetration and the corresponding annual production:

h ∈ ℕ [0 ; 8760] ; z ∈ ℕ [1 ; 7]

K(z) =

z = 1 → NORTH z = 2 → CENTER − NORTH

NPRS penetration ; NPRS contribution (z)

NPRS penetration ∈ ℝ [0 ; 100]

(9)

z = 3 → CENTER − SOUTH z = 4 → SOUTH

Total NPRS (z) = K(z) ∗

z = 5 → SICILY

∗ Total NPRS production (z) [TWh]

z = 6 → SARDINIA

(10)

For each area the inflexibility corresponding to a certain imposed Flexibility Factor FF is then evaluated:

z = 7 → ITALY • Net load for each hour in each geographical area:

Inflexibility(z) = Peak load(z) ∗ 1 −

[GW] (11)

where:

Net load (h, z) = Load (h, z) − NPRS production (h, z) [GW]

(3)

NPRS production (h, z) [TWh]

2.2. Procedure

Input Data

Load (h, z) [TWh]

Total NPRS production (z) =

A MATLAB-based simulation tool has been developed; the general approach adopted for the implementation can be summarized as follows.

∗∑

Total load (z) =

(2)

∈ ℝ [

( ) ; 100]

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The net load profile corresponding to the imposed NPRS penetration is: Net load (h, z) = Load (h, z) − K(z) ∗ ∗ NPRS production (h, z) [GW]

(12)

The amount of energy given by NPRS that cannot be instantaneously consumed is then: Inflexibility (z) − Net load (h, z) if Net load (h, z) < Inflexibility (z) Excess (h, z) = (13) 0 if Net load (h, z) ≥ Inflexibility (z)

Summing over the total number of hours, the annual quantity of NPRS energy that cannot be immediately consumed is: (K, FF, z) =

Excess =∑

Excess(h, z) [GWh]

(14)

As a consequence, the percentage rate of unconsumed energy from NPRS referred to the total energy yearly produced by NPRS can be expressed as: Excess rate (K, FF, z) = =

( ,

, )

( , )

∗ 100 [%]

(15)

By applying the above described procedure to different NPRS penetration and FF values, the evolution of the Excess rate for each geographical area can be obtained.

inconsumable NPRS energy is higher than 70% (NORTH with FF=70%). In particular, NORTH and SOUTH areas show a behavior slightly different in comparison with the one of the remaining areas, as – for the same FF value – the amount of NPRS production that cannot be instantaneously consumed is higher, as it can be noticed comparing the curves represented in Figure 4 for a certain FF (for instance, FF=70%).

4. Discussion and conclusions The results obtained in this study highlight the relevant role that the amount of energy from NPRS that cannot be instantaneously consumed plays when the issue related to the integration of the NPRS in the power generation system is taken into account. As previously shown in the analysed case study, in fact, this parameter can reach high values (in particular, it can be equal to 70% of the production). As a consequence, if alternative solutions (like storage systems or ad hoc interconnections) are not available, this limitation can have a significant impact on the increase in NPRS penetration, especially for power systems characterized by an already high amount of NPRS installed capacity: this is due to the fact that further new wind or photovoltaic plants could be affected by longer payback time and the whole management of the system could be more complex. In order to reduce the amount of energy that is not instantaneously consumed, different alternative options can be explored.

3. Results The Excess rate as a function of the NPRS penetration is plotted in Figure 3 and 4 a-f (respectively at National and area scale) for different FF values (i.e. 70%, 80%, 90% and 100% for all the areas and 60% for the major islands) where FF = 100% means that the amount of energy produced by NPRS is sufficient to cover the entire annual load). In all the simulations, the obtained curves are monotonically increasing: the annual amount of energy produced by NPRS that cannot be instantaneously consumed increases when the NPRS penetration increases or FF increases. Referring to the single areas, in the case of NPRS penetration = 100%, it can be noticed that in the most favorable case about 30% of the NPRS production cannot be instantaneously consumed (SOUTH with FF=100%), while in the worst case the amount of

Figure 3. Energy yearly produced by NPRS that cannot be instantaneously consumed (Excess rate), expressed as a function of the fraction of energy produced by NPRS (NPRS penetration) for different FF values at National scale

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Figure 4. Energy yearly produced by NPRS that cannot be instantaneously consumed (Excess rate), expressed as a function of the fraction of energy produced by NPRS (NPRS penetration) for different FF values at area scale

The first one is the increase in the flexibility of the power system. This goal could be reached by substituting the base load plants with more flexible ones (like loadfollowing units). These interventions, however, are characterized by relevant investment costs and the obtainable benefits could be not so relevant, because – as previously seen – even in the case of a Flexibility Factor equal to 100% a significant amount of NPRS

energy still cannot be consumed, especially in some areas. It can be noticed that this solution could be more effective if applied to Southern Italy and to the islands (Sicily and Sardinia). The second alternative is to increase the transmission capacity among the different areas. This solution gives only limited benefits in terms of reduction of the Excess

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rate and requires relevant investments; however it can be useful not only for the purpose of allowing a better management of the NPRS but mainly to obtain a more reliable service and an easier dispatching. The last option is the introduction of storage systems that can be particularly valuable for electrical systems characterised by an NPRS penetration of about 60% and an NPRS production mostly based on photovoltaic. Each of these possible actions has to be considered and explored for each area independently, in order to find an equilibrium among reduction of the NPRS Excess rate, economical aspects, technical feasibility, possible future developments, climatic conditions, etc. However, generally speaking, it has to be underlined that the best solution for each area could be represented by a mix of the three actions above described, according to more detailed studies and analyses. It can be further demonstrated that the kind of NPRS plants installed, be they photovoltaic plants or wind plants, matters. The power generation mix has to be suitably defined: by well-balancing the contribution given by wind and photovoltaic, a significant reduction in the Excess rate can be obtained, up to 25%. The main advantage of this solution is represented by the fact that no further investments in new plants are required. Furthermore, the presented case study shows that the obtained results remain similar even if the load profiles are quite different among the considered areas; this means that the NPRS Excess rate seems to be independent from the load profile. However, this outcome should be confirmed by taking into account other typologies of load profiles and by applying the methodology to different countries. Referring to other possible future improvements, it has to be underlined that the available data used for the analysis are hourly based and so they do not allow to extend the study to the sudden load variations (usually characterised by an order of magnitude of minutes, seconds or fractions of a second) that can happen in a power system. Some of the storage technologies (like flywheels and supercapacitors) are used to face these rapid load changes, and thus a finer timescale should be adopted when these systems are implemented into the algorithm.

References [1]

Denholm P., Margolis R.M., Evaluating the limits of solar photovoltaics (PV) in electric power systems utilizing energy storage and other

enabling technologies, Energy Policy, 35, 2007, pp. 4424-4433. [2]

Denholm P., Maureen H., Grid flexibility and storage required to achieve very high penetration of variable renewable electricity, Energy Policy, 39, 2011, pp. 1817-1830.

[3]

Denholm P., Ela E., Kirby B., Milligan M., The Role of Energy Storage with Renewable Electricity Generation, Technical Report, TP-6A2-47187, NREL, USA, 2010.

[4]

Kirby B., Ela E., Milligan M., Chapter 7: Analyzing the Impact of Variable Energy Resources on Power System Reserves, in Renewable Energy Integration, Lawrence E. Jones, Elsevier Inc., 2014, pp. 83-99.

[5]

Solomon A.A., Faiman D., Meron G., The effects on grid matching and ramping requirements, of single and distributed PV systems employing various fixed and sun-tracking technologies, Energy Policy, 38, 2010, pp. 5469–5481.

[6]

Fakhouri A., Kuperman A., Backup of Renewable Energy for an Electrical Island: Case Study of Israeli Electricity System—Current Status, The Scientific World Journal, 2014, pp. 1-8.

[7]

Erdinc O., Paterakis N.G., Catalão J.P.S, Overview of insular power systems under increasing penetration of renewable energy sources: Opportunities and challenges, Renewable and Sustainable Energy Reviews, 52, 2015, pp. 333346.

[8]

Oree V., Hassen S.Z.S, Fleming P.J., Generation expansion planning optimisation with renewable energy integration: A review, Renewable and Sustainable Energy Reviews, 69, 2017, pp. 790803.

[9]

Ulbig A., Andersson G., Chapter 18: Role of Power System Flexibility, in Renewable Energy Integration, Lawrence E. Jones, Elsevier Inc., 2014, pp. 227-238.

[10]

Franco A., Salza P., Strategies for optimal penetration of intermittent renewables in complex energy systems based on technooperational objectives, Renewable Energy, 36, 2011, pp. 743-753.

[11]

Barelli L., Desideri U., Ottaviano A., Challenges in load balance due to renewable energy sources penetration: The possible role of energy storage technologies relative to the Italian case, Energy, 93, 2015, pp. 393-405.

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[12]

Gullì F., Lo Balbo A., The impact of intermittently renewable energy on Italian wholesale electricity prices: Additional benefits or additional costs?, Energy Policy, 83, 2015, pp. 123-137.

[13]

Bigerna S., Bollino C.A., Ciferri D., Polinori P., Renewables diffusion and contagion effect in Italian regional electricity markets: Assessment

and policy implications, Renewable and Sustainable Energy Reviews, 68, 2017, pp. 199211. [14]

Terna, “Transparency Report” web section, http://www.terna.it/itit/sistemaelettrico/transparencyreport.aspx

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DOI: 10.14621/ce.20170105

Emerging Materials, Computational Research Needs and Challenges for Alternative Energy Innovations Gordana Laštovička-Medin Faculty of Sciences and Mathematics, University of Montenegro Dzodrdza Vashingtona bb, 20000 Podgorica, Montenegro; gordana.medin@gmail.com

Abstract

1. Introduction

The demand for new energy technologies has greatly exceeded the capabilities of today’s materials and chemical processes. To convert sunlight to fuel, efficiently store energy, or enable a new generation of energy production and utilization technologies requires the development of new materials and processes of unprecedented functionality and performance. New materials and processes are critical elements for progress in advanced energy systems and virtually all industrial technologies. Harvesting the potential of computational science and engineering for the accelerated discovery and development of disruptive technologies and an enchanted and integrated interplay of Computational Materials Science, Chemistry and Biology will definitely establish a new era of technology evolution. This paper shows advances and challenges in the field of computational materials science, smart materials and innovative approaches. It identifies what are some of the future trends and innovations that may make an impact on the world of energy.

It is important not only to identify hardware and software technologies but also ideologies and legaslative that can affect significantlt how particular energy will rich a crucial mass in terms of impact of our lives. This paper is focused on importance of emerging computational science and impact of technologies being pursued for harvesting the renewable energy but also for developing disruptive technologies. The disruptions in technology development are enabled by a novel approaches of energy exploration and synthesizing multiple and multidisciplinary approaches in one intelligible and robust integrated system. The objectives of this paper were to identify possible priorities and synergy trends (fundamental science, manipulation of materials through computational science and energy innovations) in the field of emerging energy technologies and to gather ideas on how to progress towards the successful development of materials with disruptive approaches. The paper provides a summary of information in references, identifies issues and problems that need to be addressed, and to some extent provides recommendations for new approaches to solving these problems. Also, the paper briefly touches the scientific contribution to solving the identified problems.

Keywords:

Multidisciplinary computing; Emerging technology, Challenges, Material science

Article history:

Received: 26 April 2016 Revised: 27 December 2016 Accepted: 20 January 2017

This technical paper is organised as follows. In the Chapter 2 the capability of predictability which is enabled through advanced computational science is discussed. The Chapter 3 deals with the challenges of technology complexity that were accelerated due to demands for more efficient harvesting the renewable and alternative energies. Particularly, the focus is given to controlling the material’s micro- and nano-structures including the self-assembly. The Chapter 4 is devoted to challenges posed to PV cells. There we explored the theoretical, experimental and technological challenges

___________________________________________________________________________________________________________ G. Lastovicka-Medin: “Emerging Materials, Computational Research Needs and Challenges for Alternative Energy Innovations”, pp. 37–43

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posed to organic polymeric and small molecules and inorganic nanostructure PV, as well as to the hybrid structures and the biomimetic materials. In the fourth chapter we tackle advantages of manufacturing the materials in microgravity environment. Conclusion is given in the last chapter.

2. Capability of predictability The computational materials science tools, based in chemistry and physics, give us as follows: the qualitative frameworks for thinking about atomistic processes and mechanisms, the quantitative understanding of thermodynamic driving forces, and the prediction of the properties or molecular architectures for engineering design. Often, we want to know the structure of a few atoms in a material (e.g., defect or reactive sites), and quantum mechanics allows us to calculate these structures and associated electronic energies to high accuracy. However, we ultimately need to predict multiscale properties that can be compared with experimental data, so we use statistical mechanics to perform temporal or spatial averages over a large number of simulations to obtain these macroscopic observables. We thus develop predictive insight that may be used to guide experimental design of new materials. The benefits of predictive capability in science and engineering are as follows. The scientific discovery process is not linear—it follows an often chaotic path of intuition, trial and error. Predictive capability accelerates discovery by guiding experiments in the most productive directions (as we saw in particle physics experiments and in nuclear industry), by reducing the number of options or configurations that need to be tried, by suggesting specific breakthrough opportunities for experimental verification, and by providing powerful tests for theories that improve fundamental understanding. In many cases, progress demands predictive capability due to the complexity that must be navigated. Capability of predictability of Computing Science is powerful tool in the transformation of technological innovation. Computing science not only predicts some material behaviour but can help to design novelty using novice approaches.

3. The challenge of complexity: The discovery of design with the mathematical modelling The advanced materials are complex. Their development includes multiple chemical components, nanoscale architectures, and tailored electronic structures. The discovery is increasingly confronted with complexity, which cannot be explored only experimentally. Thus new materials and new chemistry

have to be designed, using new synthesis, synergy and characterization tools, theory, and simulation and modeling to understand complex materials and chemical systems and predict the most promising research directions. Computational materials science and engineering has emerged as an interdisciplinary subfield spanning materials science and engineering, condensed matter physics, chemistry, mechanics and engineering in general. A number of computational methods and tools are developed, ranged from electric structure calculation based on density functional theory [1, 2], atomic molecular dynamics [3-4] and Monte Carlo techniques [5], phase-field methods [6-8] to continuum microscopic approaches. The Open Visualization Tool (OVITO), a new 3D visualization software designed for post-processing atomistic data obtained from molecular dynamics or Monte Carlo simulations is described in [9]. Transient current technique and appropriate simulation modeling is promising technique for studies of silicon detectors [10]. It is important to note that over last couple of decades the different trends in computational science in correlations to science of materials were developed. For instance, researches and approaches have been steadily moving from technique development and purely computational studies of materials towards discovering and designing new materials facilitated by computation, artificial intelligence such as neural networks and deep machine learning and data mining or by comparing and combination of computational prediction and experimental data/validation. The most resent trend emphasized the focus on design on discovery of new materials rather than on purely computational; technique improvement or purely theoretical understanding of materials structure and properties. One of Journal that support such initiative is Computational Materials [11]. The physical properties (mechanical, electrical) are often brought to the theoretical limits. What we now see is a new concept: discovery by design. Predictive modeling fosters design and testing. State-of the-art computational tools allow scientists to calculate from first principles the interactions that dominate microstructural behavior, while experimental tools can now provide time resolved measurements on real materials to validate these models. Integration of theory, simulation, and experiment accelerate materials discovery and innovation. Obviously, the keys to achieving these advances are verification, validation, and uncertainty quantification of the computer models. Thus, it is important to think and work from atoms to the bulk, and the divisions between disciplines (first principles theory to mechanical engineering) will start to dissolve. To achieve this goal one must be able to realistically simulate the physical phenomena over a vast range of time and length scales.

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3.1. Controlling microstructure Frankly speaking, simulation-based engineering is not a new concept. We now see only a new approach which employ an old concept on revolutionary new way, bringing chemistry, physics and biology to dissolve their boundaries into world of computational modelling. The availability of structural materials that can operate at extreme values of temperature, stress and strain, pressure, radiation flux, and chemical reactivity is the principal limiting factor in the performance of many energy systems. Fossil power plants, nuclear plants, and transportation systems all operate at lower efficiencies due to the limitations of existing structural materials. Central to this challenge is predicting and controlling the microstructure—the complicated arrangement of crystalline grains, defects, interfaces, and impurities that make up the microscale structure. Microstructure is the key to understanding damage processes, preventing failure, and enhancing performance. State-of the-art computational tools allow scientists to calculate from first principles the interactions that dominate microstructural behaviour. The microstructure of a material controls a wide range of important properties, including strength, fatigue, and high-temperature performance, corrosion, and radiation resistance. While there is substantial qualitative understanding of microstructural evolution, there are no predictive models that link materials processing to resultant microstructures. The special emphasis is on the experimental verification of the theoretical predication and feedback to theory. For example, the broad range of imaging and microscopic tools such as optical microscope (Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Field Ion Microscope (FIM), Scanning Tunnelling Microscope (STM), Scanning Probe Microscope (SPM), Atomic Force Microscope (AFM), Xray diffraction topography (XRT)), or spectroscopic (Energy-dispersive X-ray spectroscopy (EDX), Wavelength dispersive X-ray spectroscopy (WDX), Electron energy loss spectroscopy (EELS), Photoluminescence (PL), Photon correlation spectroscopy and dynamic light scattering (DLS), smallangle X-ray scattering, Ultra-visible light spectroscopy (UIV-vis, Small-angle neutron scattering (SANS) etc.) and many others provide information on material structure and functionality on macroscopic level and local levels. Systematic analyses and curation of these types of data will allow construction of libraries of structure-property relationship at atomic levels (similar concept used for decades in high energy physics analyses where each signal/track is assigned to different libraries and correlation between them through library manipulations allows scientists to perform physics

analyses). This knowledge can then be incorporated in theoretical models by providing realistically observed defect configurations and providing refinement of theoretical model parameters. Furthermore, there is a lack of understanding of the connections between microstructure and materials performance. The new generation of synchrotrons and neutron sources, and synthesis and characterization equipment, together with recent computational and algorithm advances, provides an opportunity for the first time to envision designing microstructures for specific purposes and bringing them to fruition in real materials [12].

3.1. Designing and engineering materials at the nanoscale: Understanding and controlling selfassembly Structures whose constituents can assemble, disassemble, and reassemble autonomously or on command enable materials capable of self-repair, multitasking, and even shape-shifting—properties known throughout the biological world. By combining organic and inorganic matter into hybrid building blocks, hierarchically ordered nanostructures can be achieved through self-assembly. Let us first define the meaning of self-assembly. According to [13] “Self-assembly is the process by which small components automatically assemble themselves into large, complex structure”. There are many examples as such: lipids self-assemble a cell’s membrane and bacteriophage virus proteins selfassemble a capsid that allows the virus to invade other bacteria. The study addressed the question “How could such a process be described as “algorithmic”?” It was clearly pointed out that since the meaning of algorithm is to automate a series of simple computational tasks, then, algorithmic self-assembly systems means that they automate a series of simple growth tasks, in which the object grown is simultaneously the machine controlling its own growth. So it becomes clear that the idea of “molecules that can perform computation” is transforming the way the engineer is self-assembling molecular systems. The systematic manipulation of information moves slowly to systematic manipulation of matter. To emphasize the computational impact on controlling self-assembly we firstly summarize some of distinctive features of self-assembly materials [14]. The sselfassembling molecules adopt a structure at the thermodynamic minimum, finding the best combination of interactions between subunits but not forming

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covalent bonds between them. Thus, in self-assembling structures, the scientist must predict this minimum, not merely place the atoms in the location desired. Another characteristic common to nearly all selfassembled systems is their thermodynamic stability. For self-assembly to take place without intervention of external forces, the process must lead to a lower Gibbs free energy, thus self-assembled structures are thermodynamically more stable than the single, unassembled components. A direct consequence is the general tendency of selfassembled structures to be relatively free of defects. An example is the formation of two-dimensional superlattices composed of an orderly arrangement of micrometre-sized polymethylmethacrylate (PMMA) spheres, starting from a solution containing the microspheres, in which the solvent is allowed to evaporate slowly in suitable conditions. In this case, the driving force is capillary interaction, which originates from the deformation of the surface of a liquid caused by the presence of floating or submerged particles [15]. These two properties—weak interactions and thermodynamic stability—lead to the sensitivity to perturbations exerted by the external environment. Those small fluctuations alter thermodynamic variables. Self-assembly also permits material structures far more complex than traditional metals, ceramics, and polymers, with many levels of hierarchical organization and compartmentalization typical of biological structures such as cells and organelles. Such materials may perform functionally in ways not possible today for traditional, non-biological matter. It requires developing simulation-based design tools that enable both the prediction of structures and their properties from building blocks and the rapid prototyping and reverse engineering of building blocks designed and preprogrammed to assemble into target structures. A huge pool of a “bricks” of next-generation, selfassembled and self-programed materials are born enabling their self-reflection and self-direction within ingested collective intelligence. Nanoparticles and colloids of nearly any shape, made of metals, semiconductors, and/or polymers, and functionalized with organic molecules and biomolecular ligands— including proteins, viruses, and DNA—as well as other chemical “hooks” are now possible. The design space for self-assembled materials is now so vast that computational tools are required for the rapid screening and prototyping of building blocks that will predictably self-assemble into desired structures. In recent years, promising new theoretical and computational approach the study of self-assembly have emerged to guide experiments, but these are in their infancy.

At the same time, continued investments in highperformance computing (HPC) have produced computing platforms that are now fast enough to permit predictive simulations of self-assembly for complex building blocks, and new experimental probes promise the needed resolution of nanoscale structure to monitor assembly processes in situ, parameterize models, and validate simulation that might lead to marked changes in the structure and even compromise it, either during or after SA. The weak nature of interactions is responsible for the flexibility of the architecture and allows for rearrangements of the structure in the direction determined by thermodynamics. If fluctuations bring the thermodynamic variables back to the starting condition, the structure is likely to go back to its initial configuration. This leads us to identify one more property of self-assembly: reversibility. One interesting example where authors cite number of hypotheses and mathematical models that try to explain how these structures self-assemble from liquid crystals is given in [16]. The authors were focused on liquid crystal self-assembly in plant cell walls (“nature’s most abundant biological fibrous composite”)—since this is an “energy-efficient material synthesis mechanism that plays a crucial role in building these materials with varied material properties”. One key term used in the paper [4] is plywood, describing the way in which selfassembled fiber constructions in nature are layered and oriented to produce particular properties—no matter whether the underlying biochemistry is based on proteins (collagen) and/or polysaccharides (chitin, cellulose) in animals or plants.

4. Computational science and PV cells Here we explore the theoretical, experimental and technological challenges posed to organic polymeric and small molecules and inorganic nanostructure PV. A common feature of organic polymer and inorganic nanostructures is the localization of their excited excitation and carriers in bulk leading to the large electron-hole interaction [17], and consequently to an obvious fundamental issue – dissociation of excitation into separated electron and hole carriers. Beside excitation transport, single-carrier transport is another issue [6] since the hole has a very small mobility in the polymer, so the hole transport is very complicated and additionally there is an lack in understanding the description of the hole mobility: is it a hopping transport, or a free-carrier-like transport or tunneling transport. Moreover, nanostructures pose a technology challenge on its own right in the areas of electronic structures, and electron-electron, electron-photon, electron-phonon interactions because of very sophisticated and

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complicated nature of wavefunction localizations caused by quantum confinement effects, band offsets and piezoelectric effects. Further, Auger effect (electron-electron interactions) causes multiple excitation generation in nanocrystal and the effect can be further explored in order to achieve highly efficient solar cells. However as it is emphasized in [18] to fully exploit the electron-electron and electron-photon interactions in order to achieve the optimal efficiency of organic PV cells, one has to understand the carrier dynamics and possible quantum coherence effects and for it is needed to perform time-dependent simulations simultaneously for both the electron and atom. Computationally, and theoretically, this is very challenging. So the potential impact of computational science is huge and both, theoretical models and computational research can mutually benefit from each other, both supported with experimental verifications. One of the issues where impact of computing can be significantly seen is to find accurate and reliable way to calculate the wavefunctions and binding energies of excitations. The exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and in some liquids. The exciton is regarded as an elementary excitation of condensed matter that can transport energy without transporting net electric charge. The wavefunction of the bound state is said to be hydrogenic, an exotic atom state akin to that of a hydrogen atom. However, the binding energy is much smaller and the particle's size much larger than a hydrogen atom. This is because of both the screening of the Coulomb force by other electrons in the semiconductor (i.e., its dielectric constant), and the small effective masses of the excited electron and hole. The recombination of the electron and hole, i.e. the decay of the exciton, is limited by resonance stabilization due to the overlap of the electron and hole wave function. Some of existing methods of calculating the wave function of exaction are as follows: variation wavefunction calculations, GW Bethe-Salpeter equation [19], excited–state quantum chemistry method [20], quantum Monte-Carlo method (which deals directly with the many-electron Schrodinger equation). However here is problem with scaling the simulation to size of the system since it requires pentascale computing or developing a new methodologies and parallel processing. Second issue is developing a good theoretical model which would describe and simulate atomic structure at the surface and interface. An initio molecular dynamics (MD) simulation seems to work well. However, to accelerate the development of a new generation of solar cells based on the organic polymers and nanostructure the supercomputer are necessity.

Another design of solar cells we want to mention here is based on biomimetic and hybrid technology which involves inorganic, organic and polymeric components interface with each other. Such structures are very complex, involving considerable challenge in reliable and effective predictions of the material structure and morphology stability, electrical transport, accurate predictions of level alignment in heterojunctions and contacts, etc. The reliable simulation of transport properties is necessity. One solution is dynamical simulations by using the Green-Kubo mechanism with the Boltzmann transport theory to calculate the thermoelectric power. Beside atomistic computational modeling technique there are important challenges such as development of force fields and coupled quantum mechanical/molecular methods for describing week (van der Walls) and strong interactions. To summarize the significant parallel computing and advanced modeling of transport properties and physical phenomena on quantum level are needed to accelerate hybrid technology for solar cell. New characterisation techniques help understand fundamental processes [21] where the major issue is electronic structure of heterojunction which heavily influences device performances and where major limitation of inorganic nanoparticles are related to the surface chemistry. An interesting technique which was developed to study the properties of the silicon detector at LHC (CERN), so called the transient current technique (TCT) seems to be promising tool to study the photovoltaic solar cells [2224]. TCT technique is suitable technique to study the charge-carrier transport mechanism. This includes the determination of electron and hole drift velocities as a function of electric field, charge carrier lifetimes as well as effective concentration of space charge in the sensor/detector bulk. The method is based on the injection of alpha source or laser short pulse close to surface and measuring the induced current in the detector electrodes as a function of time.

5. Computing the microgravity: Manufacturing in the space The concept “zero gravity” is moved to the concept of “microgravity”. There are many surprises and not all experiment results have yet been satisfactorily explained. An early extensive study on microgravity effects on materials processing is given in [25]. Here we summarize some advantages that were enabled through microgravity: microgravity enhances the sedimentation and buoyancy, increases dopant homogeneity in semiconductors. Semiconductors are often doped to establish specific electronic properties (i.e. n-type or ptype). Convection on Earth can cause the distribution of these dopants to be inhomogeneous, degrading the

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suitability of crystals for their intended application. Absence of convection [24] in microgravity enables uniform distribution of the dopants. Moreover microgravity expands the possibilities for container less processing. It enables accurate measurements of material properties such as viscosity and surface tension, facilitates nucleation studies, and increases the size of crystals that can reduce defect densities from contact with container wall [27].

6. Final remarks: Creating an innovating ecosystem This paper provides learning opportunities for those who are not familiar with emerging trends in science of materials and computational science, both used as a driver force in the energy innovation sector. Importantly it gives an insight into innovations which are the results of a fruitful exchange of ideas among interdisciplinary research projects. It is enabled by an innovative ecosystem where approaches from different disciplines are transferred in the energy sectors (bio-mimicking in engineering such as the photosynthesis and selfassembling etc.). Doing extensive research on the trend of the emerging technologies we have the following conclusions: -

There is no single technology which would be a total solutions in itself;

Developing an energy mix would become more important in the future;

The current trends clearly addressing issues towards the integration of new technologies such as micro and nano-electronics, micro-and nanoelectro-mechanical, micro-fluidic, magnetic, photonics, bio-chemical, multi-functional and smart integrated system;

An understanding of technology fundamentals, prototyping at low scale, and then up-scaling and tech remonstrations are all very important in the development of new energy technologies;

An innovation in computational science education is of crucial importance in particular towards not only developing tools for verification existing tools but also towards creating new through accidentally merging the different concepts and by systematic studies of the outcomes;

Developing curriculum at Universities with a wide mix of disciplines.

Achieving predictive capability will accelerate progress in Integration of synthesis, processing, characterization, theory, mathematical modelling, chemistry breakthrough discoveries and simulation. Simulationbased engineering and science benefit from predictive capability in science and engineering. Multimodal, multifunctional and multidisciplinary modelling has a significant role in accelerating scientific discovery, enabling new technologies, efficient transfer and incorporation of simulation-based engineering and science in industry.

Acknowledgements This work is supported by Ministry of Science of Montenegro, and it is part of innovative teaching methods which will create an innovative ecosystem for synergy of interdisciplinary studies.

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Yogesh K. Murugesan1, Damiano Pasini2 and Alejandro D. Rey, Self-assembly Mechanisms in Plant Cell Wall Component, J. Renew. Mater., Vol. 3, No. 1, DOI: 10.7569/JRM.2014.634124, March 2015.

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consisting of soluble polythiophene and fullerene derivatives, Appl. Phys. Lett. 97, 132105. [19]

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DOI: 10.14621/ce.20170106

Open Source Sun Tracking System with Solar Panel Monitoring and Heliostat Control System Gordana Laštovička-Medin Faculty of Sciences and Mathematics, University of Montenegro Dzodrdza Vashingtona bb, 20000 Podgorica, Montenegro; gordana.medin@gmail.com

Abstract

1. Introduction

Issues, challenges and opportunities in the energy sector clearly address the necessity for innovations not only in technology but importantly also in the education sector. But how to create environment for innovations in energy technologies, regulations and policies is another challenge. An apparent decline in interest and enrolment of young people, especially young women, in engineering, science and technology is widely seen. This sheds new light on the need to develop public and policy awareness and understanding of engineering, affirming the role of engineering as the driver of innovation, social and economic development is of crucial importance. It also emphasizes the need to transform engineering education, curricula and teaching methods to emphasize relevance and a problem-solving approach to engineering. Another challenge is how to integrate both teaching the fundamental sciences such as physics and chemistry and innovations in engineering. The overall objectives of this paper are thus to show how through already existing open source products students may build a flexible, modular and multifunctional sun-tracking set up. The paper is mainly technical report on the work in progress. The method combines both, optical sensors and astronomical calculations. The tracking program (astronomical calculation) is selected as an auxiliary method. The initial set up is built from the SwitchDoc Labs Products such as SunAirPlus Solar Power Controller Board. The board is compatible with the microprocessor Raspberry Pi and the microcontroller Arduino. Furthermore, the board incorporates a number of outstanding features in a very compact, inexpensive single fully assembled and tested PC Board. Moreover, the Field Programmable Gate Arrays (FPGAs) is considered as an appropriate solution to behavioural control of the tracing system. The final aim of this research and main motivation is to use the set-up for the teaching basic measurements in Physics and to encourage students to take role in engineering and energy innovations.

The photovoltaic (PV) is divided into fixed-type where the angle of PV module is fixed at a certain angle and tracking-type where the azimuth and altitude of the sun is tracked to receive the sunlight perpendicular to the module surface. Tracking the location of sun on the ground includes the method of using optical sensor (passive), the method by astronomical calculations (active), and the method combining the two. The sun tracking device using optical sensor involves operation of an actuator to operate the sun tracking system using the difference of radiation intensity detected through photo sensor. The astronomical calculations are based on information of longitude and latitude of the tracking system installation location.

Keywords:

Sun tracking; Sensors, Embedded systems; FGPA; SunAirPlus; Auxiliary

Article history:

Received: 26 April 2016 Revised: 27 December 2016 Accepted: 20 January 2017

There are three main tracking systems: auxiliary bifacial solar system, electro-optical sys-tem, and microprocessor/computer system. Aauxiliary bifacial system is the simplest among them. The bifacial auxiliary solar cell is fixed to the rotary axle of the tracker and is placer perpendicular to the main bifacial solar panel array. The sensor cell is mounted directly to the motor (direct current (DC) electromotor or stepper motor) [1]. The electro-optical sys-tem is another relatively simple system. Typically two photoresistors or PV cells are used as sensors for one-axis systems. These sensors are positioned near one another and have a divider or use a collimator to create a useful current and/or voltage difference between the two sensors. A combination of resistors, capacitors, amplifiers, logic gates, diodes, and transistors are used to form a comparison and driver circuit. The output of the comparing circuit powers a driver circuit, which in turn powers a motor and changes direction according to which sensor receives a higher amount of illumination. This orients the solar panel to be perpendicular to the sun [2, 3]. The microprocessor and computer systems make up the last type of system. They are some-times classified into

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two different groups, but essentially they are quite similar. The main difference to the first two mentioned systems is microprocessor/computer systems use algorithms to determine the position of the sun instead of using sensors. Typically, microprocessor/computer systems only use sensors to reduce error or calibrate the system. Some micro-processor/computer systems even use a current maximization routine for error correction instead. In many systems a cheap microprocessor such as a Programmable Interface Controller (PIC) will have the algorithm for tracking, while information is fed to a computer, for analysis purposes. In [4] the microcontroller has two primary modes, clock mode and sun mode. The clock mode calculates the position of the sun and makes any modification to the algorithm based on the solar error sensors. In the sun mode, the algorithm actively positions the solar panels. If the solar intensity decreases below a set value, the clock mode is activated. This variety of modes helps in better positioning and therefore a higher gain [4]. In what follows we explore the hybrid version of above discussed tracking systems.

2. The conceptual design The solar tracking system uses a DC motor as the drive source to rotate the solar panel. The position of the sun is determined by using a tracking sensor, light

dependant resistor (LDR). A Light Dependent Resistor (LDR) or a photo resistor is a device whose resistively is a function of the incident electromagnetic radiation. Hence, they are light sensitive devices; they are also called as photo conductive cells or simply photocells. They are made up of semiconductor materials having high resistance. The analogue signal (reading from LDR) is then converted to digital signal by using an analogue digital converter (ADC) and then further passed to a fuzzy logic controller implemented on FPGA card (Figure 1). The interfaces are crucial components. The SunAirPlus board has the following other interfaces: the built into the board: the built-in I2C data gathering chips for system currents /voltages, the built-in I2C Interface for solar tracking photoresistor devices, the built-in Interface for servo motor or stepper motor and the built-in interface for limit switches. The Solar Charge Controller on SunAirPlus is based around a CN3065 Lithium Ion Charge Controller to run the charging sequences for the batteries. The CN3065 is a complete constant-current /constant voltage linear charger for single cell Li-ion and Li Polymer rechargeable batteries. The device contains an on-chip power MOSFET and eliminates the need for the external sense resistor and blocking diode. An on-chip 8-bit ADC can adjust charging current automatically based on the output capability of input power supply, so CN3065 is ideally suited for solar powered system The chip does an

Figure 1. Solar tracking control architecture ___________________________________________________________________________________________________________ G. Lastovicka-Medin: â&#x20AC;&#x153;Open Source Sun Tracking System with Solar Panel Monitoring and Heliostat Control Systemâ&#x20AC;?, pp. 44â&#x20AC;&#x201C;50

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ideally suited for solar powered system The chip does an approximation of the Maximum Power Transfer Tracking (MPPT). Thus, it is the purpose of the MPPT system to sample the output of the cells and to apply the proper resistance (load) in order to obtain the maximum power for any given battery and the temperature conditions. Furthermore, the SunAirPlus contains the robust ADS1015 A/D converters, INA3221 voltage and current sensing circuitry and an optional stepper motor controller which allows user to expand the project. The controller output is connected to the driver of the DC motor in order to rotate PV panel in two axes until it faces the sun. In order to reduce the control problems, the two drive motors (for azimuthal and attitude angle) are decoupled, i.e., the rotation angle of one motor does not influence that of the other motor. Thus, the processor is the main control core and adjusts the twoaxis motor so that the platform is optimally located for efficient electricity generation. The logic flow design of the system is implemented with an embedded processor control circuit. When the tracking control circuit is activated, the system performs tracking, energy conservation, and system protection, as well as system control and external anti-interference measures. External interference includes weather influences, such as wind and rain. Thus, the embedded processor acts as the control center and integrates the two-axis control chip. The Field Programmable Gate Arrays (FPGAs) is considered as an appropriate solution to the behavioural control of the tracing system. Here we will give brief description of FPGA. A field-programmable gate array (FPGA) is an integrated circuit (IC) that can be programmed in the field after manufacture. FPGAs are similar in principle to programmable read-only memory (PROM). In this building project the FPGA supports an intelligent tracking prototype that move around and explore the area while sending back reports. At the same time the system may track the sun position and extract the weather conditions following the sensor information and compared it to the sun position using astronomical data. Furthermore, FPGA can be programmed to calculate solar efficiency and radiation emissions, managing a power budget tightly and providing a platform for testing new sensors and equipment as they become available.

2.1. The azimuth positioning and the elevation control Figure 2 shows a motor driver shield for Arduino boards. Its features are as follows: it can control up to 4 bidirectional DC motors with an individual 8-bit speed selection, or 2 stepper motors (unipolar or bipolar) with a single coil, double coil, interleaved or micro-stepping

Figure 2. Arduino boards that can control up to 4 bi-directional DC motors with individual 8-bit speed selection, or 2 stepper motors (unipolar or bipolar)

and 2 connections for 5V 'hobby' servos connected to the Arduino's high-resolution dedicated timer [5]. The shield contains two L293D motor drivers and one 74HC595 shift register. The shift register expands 3 pins of the Arduino to 8 pins to control the direction for the motor drivers. The output enable of the L293D is directly connected to the pulse width modulation (PWM) outputs of the Arduino. Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a modulation technique used to encode a message into a pulsing signal. Although this modulation technique can be used to encode information for transmission, its main use is to allow the control of the power supplied to electrical devices, especially to inertial loads such as motors. This project uses a stepper motors to control the position of solar energy collectors. One of the possible concepts is to use bipolar stepper motors to rotate 2 photovoltaic cells around the altitude and azimuth axes. Alternative option is to use a servo motor geared for high-torque controls the azimuth positioning of the solar panel, and a 12 VDC linear actuator to control the elevation. It is important to note however, that stepper motors operate at full torque while the advantage of a servo motor is the ability to control torque in an application.

2.2. Optical sensing and processing: The sun tracking sensor LDR (Light Dependent Resistance) is used as a sensor for generating an electric signal proportional to intensity of light falling on tracking system. The idea is to mount the LDR at the focus of reflector which is directly mounted on solar energy collectors. The LDRs are connected via a 4-conductor cable to analog input pins of the Arduino; azimuth is determined by the light levels sensed by two of these side-by-side, and elevation is determined by

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averaging the levels of those two and comparing to the light sensed by the third LDR positioned below them. This arrangement allows the Arduino to orient the face of the solar panel towards the direction with the most light by driving the servo and linear actuator. The Arduino communicates with the Aduino Motor Shield using I2C over pins A4 (SDA) and A5 (SCL). The servo motor is controlled using an output from the Arduino on pin 9. The linear actuator has a built-in potentiometer for indicating its position. One end (yellow wire) of the pot resistor is connected to +5V. The other end is tied to the wiper (white and blue wires) which are then connected to pin A3 through a 10k resistor, forming a voltage divider allowing the Arduino to sense the position of the actuator.

2.3. The control subsystem / Raspberry Pi The microprocessor Raspberry Pi 2 additionally enables image processing. This processor could run both the PiCamera, and the light emission diodes (LEDs).

2.4. LOGI FPGA communication to control subsystem (Raspberry Pi) LOGI is an open-source closed-loop FPGA (Field Programmable Gate Arrays) development solution consisting of an ecosystem of FPGA hardware, software, drivers and applications which builds on the BeagleBone or Raspberry Pi platforms. Its distinctive feathers are as follows: it has gateway for MCU/CPU users to learn and use FPGA, seamless FPGA and CPU development on BeagleBone or Raspberry Pi, plug-and-play for Arduino compatible and Pmod peripheral modules, supports Raspberry Pi and BeagleBone Black. Furthermore it allows the dynamic reconfiguration of FPGA from the host CPU.

2.5. SunAirPlus: Single axis azimuthal tracker SunAirPlus is a solar power controller / sun tracker / power supply system developed by SwitchDoc Labs to power Arduino and Raspberry Pi based systems. The board consists of solar panel/charge control system, a voltage booster, two A/D systems and GPIO interface circuitry systems. The interface systems is used to shift the voltage level and also for the servo motors as well as for the stepper motor control. The SunAirPlus contains robust ADS1015 A/D converters, INA3221 voltage and current sensing circuitry and an optional stepper motor controller built into the SunAirPlus board [6]. It does not have dual auxiliary system for azimuthal and elevation tracking. The internal A/D converters on the Arduino are sufficient for reading the photoresistors used by

SunAirPlus to track the sun, but since the Raspberry Pi has no built-in A/D converters, SunAirPlus includes a circuit to do this. The current/voltage sensors are one of the most interesting parts of the SunAirPlus board since they allow user to receive dynamic and accurate information on how Solar Power system is running. Interfacing a stepper motor to SunAirPlus is a little more complicated but there is an excellent tutorial in [6-7]. Importantly, the SunAirPlus contains a space for a stepper motor driver utilizing the L293D Dual H-Bridge Motor Driver. L293D is a typical motor driver or Motor Driver Integrated Circuit (IC) which allows DC motor to drive on either direction. To be more precise, L293D is a 16-pin IC which can control a set of two DC motors simultaneously in any direction. It means that you can control two DC motor with a single L293D IC. It works on the concept of H-bridge. H-bridge is a circuit which allows the voltage to be flown in either direction. The voltage needs to change its direction for being able to rotate the motor in clockwise or anticlockwise direction. Thus, H-bridge IC is ideal for driving a DC motor. Another interesting component is Quad Power Management Board that is also SwitchDoc Labs Product. This way the solar power susbsystem incorporate both the SwitchDoc Labs SunAirPlus solar power control board and the Quad Power Management Board. The Quad Power Management I2C Board allows user to switch on and off batteries, power supplies and solar panels. It is like an I2C controlled quad solid–state relay. Its technical features are the following: it has I2C controlled, four independent solid state relays each equipped with LEDs (where each LED is able to switch 20 V and 2.3 A), and four additional GPIOs.

2.6. I2C control subsystem One of the challenges is to be able to develop and prototype/manufacture smart objects and systems that closely integrate sensors, actuators, innovative microelectromechanical systems (MEMS), embedded memory and communication capabilities. For this purpose, the I2C bus (Figures 3 and 4) connects together the vast majority of the sensors and the various motor controllers inside of SunTracker. The Inter-Integrated Circuit, I2C, is a multi-master, multi-slave, single-ended, serial computer bus invented by Philips Semiconductor (now NXP Semiconductors). It is typically used for attaching lower-speed peripheral ICs to processors and microcontrollers in short-distance, intra-board communication. In design, explored here, there are two groups of I2C busses, one for the microcontroller Arduino and one for the microprocessor Raspberry Pi. The SwitchDoc Labs I2C 4 Channel Multiplexer has potential to isolate address ranges. It has both 3.3V and 5.0V I2C busses and communicates to both, the Arduino

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Figure 3. Solar tracking system built by WatchDoc Lab.

Figure 4. More expanded version of SolarSunAir [8]

and to the Raspberry Pi. This a very careful software that controls the two I2C Muxes; in electronics, a multiplexer (or mux) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. An external device can also communicate to the same I2C (like the motor controller).

3. The azimuthal orientation program To perform heliostat system, an azimuthal orientation program based on statistical metrological data has to include the following functions: latitude and longitudinal input, location selection, geographical data acquisition,

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processing of data, calculating the number of vertical and horizontal steps which provides calculations of steps to be performed by bipolar stepper motor [9] that realize two axes orientation.

many open source tracking algorithms are freely available. All above mentioned provides a rich pool of opportunities for lab exercises that encourage students to be engaged in energy prototyping innovations and research.

4. Conclusions and the possible potentials for advanced lab measurements

Although using sun-tracker is not essential, its use can boost the collected energy 10–100% in different periods of time and geographical conditions. But, it is not recommended to use tracking system for the small solar panels because of high energy losses in the driving systems. It was found that the power consumption by tracking device is 2%–3% of the increased energy. The proposed prototype can offer a tool for the systematic and comprehensive study on this issue. Furthermore, the reviews about sun-tracking methods for maximizing solar systems’ output [11, 12] can be used for further upgrade or comparative studies. Image Pro-cessing described in [13] is an interesting proposal to be considered. Moreover, the heat transfer from heliostat to receiver that is delivered by solar radiation can be further investigated and adjustment applied to control heliostat. Among other topics, the energy returned on energy invested, is an interesting topic of research to be considered, too.

This paper presented the work in progress. The main motivation was to create innovative ecosystem for students through developing a modular and multifunctional set-up which might be use to demonstrate energy harvesting and for the labmeasurement exercise. The first phase of project is completed and as outcome we presented the hardware design and features of the electronic components. The proposed design is based on open source software and hardware components. It includes also embedded technologies. The second phase – building the experiment and as its outcome – the measurement results together with study of correlations of variables, is under developing. The simulation/modelling of sensor behaviours is also under development. Lack of some sensor components and furthermore delay with the fabrication of some mechanisms further delayed the study. The proposed tracking system scheme is tested on a hardware prototype experimental set-up. For future work, we will do performance testing in the field and iteratively adjust all parameters of the Sun tracking algorithms to develop an optimal tracking system. The solar tracking design includes the solar tracking system, sun tracking system, sun tracker system, solar track system, sun positioning system, and sun path tracking with follow the sun position calculation (azimuth, elevation, zenith), sun trajectory, etc. It requires automatic solar tracking software and solar positioning algorithms. As a result of the apparent motion of the sun, a sun-path on-axis sun tracking system such as the attitude-azimuthal dual axis or multiaxis solar tracker systems use a sun tracking algorithm or ray tracing sensors or soft-ware to ensure that sun passing through the sky is traced accurately and his position deter-mined with high accuracy in automated applications using sun positional astronomy. Sun Surveyor and Sun Position computer software for tracking the sun are now available as pen source code, sources that are listed in [10]. Automatic sun tracking system software includes algorithms for solar attitude azimuth angle calculations required in following the sun across the sky. In using the longitude, latitude GPS coordinates of solar tracker location supports precision solar tracking by determining the solar attitude×azimuth coordinates for the sun trajectory. As emphasized in [10]

Acknowledgements This work is supported by Ministry of Science of Montenegro as part of workshops “Innovative teaching methods”.

References [1]

V. Poulek and M. Libra, A very simple solar tracker for space and terrestrial applications, Solar Energy Materials & Solar Cells 60 (2000) pp. 99 – 110.

[2]

H. Mousazadeh, A. Keyhani, A. A. Javadi, H. Mobli, K. Abrinia, A. Sharifi, A review of principle and sun-tracking methods for maximizing solar systems output, Renewable and Sustainable Energy Reviews, January 2009. pp 1800 – 1812.

[3]

Adrian Catarius, Mario Christiner, AzimuthAltitude Dual Axis Solar Tracker, A Master Qualifying Project: submitted to the faculty of WORCESTER POLYTECHNIC INSTITUTE In fulfilment of the Degree of Bachelor of Science, December 16, 2010.

[4]

P. Roth, A. Georgiev, H. Boudinov, Cheap two Axis sun following Device, Energy Conversion and Management. 2005.

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[5]

http://www.hobbytronics.co.uk/arduino-motorshield

[6]

http://www.switchdoc.com/wpcontent/uploads/2015/03/SunAirPlus_031215V1.2.pdf

[10]

Prinsloo, G.J., Dobson, R.T. (2015). Solar Tracking. Stellenbosch: SolarBooks. ISBN 978-0-62061576-1, p 1-542. DOI: 10.13140/2.1.2748.3201.

[11]

H. Mousazadeh, A. Keyhani, A. Javadi, H. Mobli, K. Abrinia, A. Sharifi, A review of principle and sun-tracking methods for maximizing solar systems output. Renew. Sustain. Energy Rev. 2009, 13, 1800–1818.

[7]

http://www.instructables.com/id/Control-yourmotors-with-L293D-and-Arduino/

[8]

http://www.switchdoc.com/wpcontent/uploads/2015/09/IMG_5790.jpg

[12]

C.Y. Lee, P.C. Chou, C.M. Chiang, Sun tracking systems: A review. Sensors 2009, 9, 3875–3890.

[9]

Constantin Ungureanu and Condrut-Stfan Ababii, Buletinul, Research on the development of azimuthal tracking system used for photovoltaic panel orientation, 2012, AGIR nr. 4/2012.

[13]

Cheng-Dar Lee, Hong-Cheng Huang and Hong-Yih Yeh, The Development of Sun-Tracking System Using Image Processing, Sensors 2013, 13, 54485459; doi:10.3390/s130505448.

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DOI: 10.14621/ce.20170107

Review of Turbine Governing System Tests Performed on Hydro-Power Plants in Croatia Zdravko Eškinja*, Krunoslav Horvat, Vedran Bakarić, Ognjen Kuljača Brodarski institute 10020 Zagreb, Croatia; zdravko.eskinja@hrbi.hr

Abstract

1. Introduction

This paper reviews different measurement methods of dynamic parameters in hydro-power turbine governing system. Twenty years of developing and maintaining such systems allow our experts to do diagnostics of a developing fault before its actual occurrence. Significant amount of collected data enabled a comparative analysis with very interesting results. Measurements made by integrated applications will be presented here alongside regular tests. The most valuable benefit of all described efforts is energy production without unpredicted breaks.

In order to ensure safety and increase operational performance and reliability of a complex system, such is a hydro-power plant, periodical tests should be performed. The testing procedure is defined by the set of standards [1] [2] and codes [3] that requires actual information about the dynamic parameters of the turbine system. Adequate provision for testing should be ensured through the phase of plant design. Appropriate conditions are elementary requirement for easy and affordable tests that guarantee long and healthy lifetime of the system. The choice of sensory system and data acquisition (DAQ) depends on the plant. There are three basic approaches as shown in Figure 1: 1. Standalone, completely independent measurement system added to the observed system while testing; 2. Combined system that uses data from the digital regulator with pre-calibration and some additional sensors; 3. Transient recorder, integrated in the system with the main purpose of the post-failure diagnostics [4].

Keywords:

Measurements; Turbine; Regulator; Dynamic; Parameters

Article history:

Received: 15 April 2016 Revised: 20 January 2017 Accepted: 20 January 2017

The first option is used when testing older or protected systems that don’t allow any connections [5]. All measuring equipment is required to be set just for testing purpose. Placing sensors, arraying cables, setting the adjustment circuits etc. may be costly in both time and money, a clear disadvantage. The most common approach is the second one, with combined configuration where existing infrastructure is used. Each sensor must be tested individually and calibrated if needed. Setting up the software for data collection is a bit different than in standalone configuration: digital addresses of relevant variables from the turbine control

___________________________________________________________________________________________________________ Z. Eskinja et al: “Review of Turbine Governing System Tests Performed on Hydro-Power Plants in Croatia”, pp. 51–56

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Figure 1. Block schematics of three different testing approaches

Table 1: Characteristics of the tested HPP turbines shown in this paper POWER PLANT

Type

Unit

P [MW]

Design Head [m]

21.9

Rated discharge [m3/s]

Rated Rotation sped [o/min]

Construction year

Testing approach

225

125

1975

turbine 30 pump 20

600

1984

HPP Varaždin

Kaplan

PSPP Velebit

single-stage turbine-pump

138

turbine 517 pump 559

Francis

18.4

212.7

10.5

600

1968

Francis

187.5

2005

Kaplan

20.4

110

166.6

1989

1/2

HPP Rijeka HPP Peruća HPP Đale

system should be known. The integrated approach is a new product, very similar to the combined system, but it does not require PC and enables recordings of transient events even in every-day working mode. Transient recorder is triggered manually or automatically as response on some specific event like emergency stop or initial start. The examples of such approach may be seen in HPP Lešće, HPP Čakovec, HPP Dubrovnik, HPP Senj, HPP Đale etc.

2. Turbine tests The scope of this paper is testing functions and components of basic primary modes of hydro control systems: speed, power and opening control. The output

of each segment has common elements: reference values, actual values and additional auxiliary values such as limiters and disturbance parameters. Thanks to the Institute’s expertise as a national leader in turbine governing systems, as described in [6], [7], [8] and [9], our engineers have the privilege to test and analyze most of high power hydro turbines in Croatia [10]. Due to limited space, only a selection of the performed tests will be mentioned here. Choosing from portfolio spanning 20 years was a very demanding task. At the end, geographical and technical characteristics became main guideline for the selection. Chosen turbine systems with their basic parameters are listed in Table 1. This paper will try to point out the significance of performing qualitative testing through the examples of

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the real power generating systems. Analyzed data were collected periodically and two of three mentioned testing approaches were used. By comparing the turbine’s behavior in the same experiment performed in different years, this review will track changes through time. Different tests are usually performed with same method, but with different settings or with different plant components, since the aged equipment is regularly replaced during the plant maintenance. Therefore, differences recorded in different years do not reflect equipment aging, but show differences in the plant control system setup. This paper will exclude all the details and will concentrate just on existence of difference and hint some possible causes.

2.1. Opening control The role of the opening control is to position the servomotor, usually as a follow-up control in master control operations. A special design of servo opening systems implemented on PSPP Velebit includes the group of servomotors, linked all together, guiding the wicket gates to a desired position. Such electro hydraulic control requires very precise synchronization. The closing and opening movements of the servomotors are not continuous but take place in 2 or more speed steps. Opening and closing speed rates are defined by the manufacturer, so there is no purpose to directly compare behavior of different opening control systems. Pressure variations are not subject of this paper, but it is worth to mention that the safety testing procedures should be done if some boundary values are exceeded.

2.2. Speed control Speed control of the turbine is tested while starting, stopping and in steady-state conditions in mechanical run. Turbine startup is the most interesting because its behavior is unique from system to system. While starting, the speed curve is mainly determined by the characteristics of the installation, such as the unit acceleration constant, the allowable gate opening rates etc. The speed governor is turning on when approximately 80% of rated speed is reached (t0.8). The main objective of this phase is to reach synchronization readiness within an acceptable time span. Synchronization readiness is achieved when the speed change rate dx/dt does not exceed a given value within the synchronization band. According to [2] recommended values for synchronization band are from 0.995 to 1.01 of the rated speed. Speed change rate for synchronization is dx/dt = 0.003 s-1. The ratio between time at which the generator is switched on line and startup time t0.8 should be in range from 1.5 to 5. The fluctuation of the turbine speed shall not exceed the speed limit of 0.1% for measurements under steady-

state conditions, except if permitted by mutual agreement. Figures 2 to 6 represent speed control at turbine startup of different governing systems during different periodical tests. Figure 7 shows the speed curves recorded at five different plants. Curves are matched together to fit as much as possible. Almost every test of this system took place after annual system maintenance. Different settings caused some deviations from year to year, but all curves are still within predefined boundaries. Figure 2 shows pretty large variation in turbine startup behavior recorded in different tests. Similar behavior may be also seen in Figure 3 and Figure 4. The optimal curve shape should be defined by the project documentation. Figure 5 shows two startups (2008 and 2015) from 0% to 100% and one startup (2013) when the machine was not started from still mode. This is an example of good regulation where startup behavior is not affected by aging, and also by different way of starting. The reason why the turbine from Figure 6 does have significantly different behavior in 2015 in comparison to two earlier tests is completely different regulator. Figure 7 proves the fact that different systems have different behavior. It is also noticeable how HPP Varaždin has quite different, slow starting dynamics compared to other systems. HPP Peruća and HPP Rijeka have very similar but not identical startup curve shapes. They both have the Francis turbine, but the first system is part of an adjacent plant with a reservoir and the second one is installed in the run-of-river plant with a long penstock. As presented, all units satisfy defined conditions, but their behaviors are not optimized. Optimal curve shapes that should be defined by documentation are not present in reality. The variations between different settings are quite different and it is yet not known how it affects the system. The results indicate clearly just how a dedicated research would be needed to obtain more answers.

2.3. Power control Power control is the most important segment of regulation. Due to the fact that the power output affects quality of the international power grid, many power control aspects are regulated by the law. The crucial parameters are variation of the referenced value (power and frequency), but also start-up time. The minimum speed of changing power is 1% of rated power in second. Primary regulation conditions are [2]:

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Figure 2. Turbine startup tests at HPP Rijeka

Figure 3: Turbine startup tests at HPP Varaždin

Figure 4. Turbine startup tests at PSPP Velebit

Figure 5. Turbine startup tests at HPP Peruća

Figure 6. Turbine startup tests at HPP Đale

• Static speed control system should be adjustable upon request of the transmission system in the range of 2% to 5% • Insensitivity of the primary control is 20 mHz for new and refurbished generating units.

Figure 7. Comparison analysis of different turbine response during startup

Secondary control has even more strict demands: • Hydro generating units, intended for secondary control, must be capable of continuous change of active power from 1.5% to 2.5% Pn (Pn = nominal active power) between the minimum and nominal active power.

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• The production unit must be able to provide the power grid, contracted reserve power for tertiary regulation no later than 5 minutes after application. Additional requirement from the standard is: • During the steady-state working regime, power output of the turbine shall not derivate from the reference value by more than 1.5% of rated output. Comparison of different systems while changing power is given in Figure 8. Testing years are chosen randomly. Diversity of power curves in this figure originates from differences in system characteristics between various plants, as was the case in the speed control section. The desired power curves are set by plant design documentation in order to achieve optimum performance. They may differ between various plants, although all of them have to satisfy criteria set by the standards.

3. Conclusion The subject of presented tests was turbine system of hydro generating plants with different technical design. Results show differences in system’s behavior. The

reason why the different systems are observed under same frame is to emphasize the differences between systems that are covered with one general standard. In other words, satisfying the standard should not be the only condition for all power units. Small variations over years are significant signs the system is not optimized. It is yet to research if and how these tolerated deviations affect the system’s health. Satisfying the standard is primary task, but with sophisticated measurements and adequate project documentation it is possible to set optimal configuration and extend lifetime of the system. The focus of this paper is given to shapes of the curves rather than their values. For the purpose, uncertainties and detailed characteristics of each system are left out. It is not relevant how quick the startup sequence is or how large is deviation of power response. The observed subject is dynamic behavior during fast transitions, and the general conclusion is absence of uniformity. Obviously, speed and power curves cannot be standardized on the higher level, but optimization of individual power unit type should be placed in higher position of hierarchy in HPP's priority. As already noted in the paper, testing turbine control system is done because of a few reasons. Testing verifies the conformity with the technical regulations and international standards, detects possible defects,

Figure 8. Comparison analysis of power control tests ___________________________________________________________________________________________________________ Z. Eskinja et al: “Review of Turbine Governing System Tests Performed on Hydro-Power Plants in Croatia”, pp. 51–56

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detects mistuning of parameters or parts and so on. This ensures that the power plant is more robust and meets the international standards, satisfying grid codes and reduces maintenance costs because the replacement of worn-out parts of the plant can be performed when the machine is not used in the production. New digital turbine systems allow performing required periodical tests much easier and faster. The annual plan of produced electric power is more reliable if positive result of such tests stands behind it.

Machines, Plants, Equipment and Drives”, hr, Šibenik, Croatia, 06-07.06.2005 , pp. 45-48. [6]

Mišković Ivan, Horvat Krunoslav, Ambruš Davorin, Paviša Tomislav, Mišković Mato, “HPP Dubrovnik - measurements of water level oscillations in surge chamber and tailrace tunnel”, hr, 8th HRO CIGRÉ Session , Cavtat, Croatia, 04-08.11.2007., C2-22.

[7]

Bakarić Vedran, Mišković Ivan, Horvat Krunoslav, Bojić Davor, Šikić Držislav, Stojsavljević Milan, “HIL TESTINGS OF TURBINE GOVERNING SYSTEM OF HPP LEŠĆE“, hr, 10th HRO CIGRÉ Session , Cavtat, Croatia, 06-10.11.2011, C2-06.

[8]

Šijak Tomislav, Horvatek Hrvoje, Horvat Krunoslav, Kuljača Ognjen, Vrdoljak Krešimir, Nemec Darko, Plavšić Tomislav, Brezovec Miljenko, Štefan Željko, Strnad Ivan, Marković Darko, “Pilot project of generating unit monitoring system for primary frequency control“, hr, 11th HRO CIGRÉ Session , Opatija, Croatia, 10-12.11.2014., 1-09.

[9]

Linarić Davor, Boko Momčilo, Ambruš Davorin, “HPP Orlovac Hydraulic System Testing”, hr, 8th HRO CIGRÉ Session , Cavtat, Croatia, 0408.11.2007., C2-21.

[10]

Sever Zvonimir, Franković Borislav, Pavlin Željko, Stanković Vladimir, Hydroelectric power plants in Croatia, Hrvatska elektroprivreda d.d, Croatia, Zagreb, 2000.

References [1]

Hydraulic turbines – Testing of control systems, HRN EN 60308, 2008.

[2]

Guide to specification of hydraulic turbine control systems, HRN EN 61362:2014, HRN EN 61362, 2008.

[3]

“Grid Code” of the Croatian public electric network, hr, NN 36/2006.

[4]

Eškinja Zdravko, Mišković Ivan, Horvat Krunoslav, “Transient recorder of the turbine governance system“, hr, 28th International Conference ENERGETIKA 2012, Zlatibor, Srbija, 27-30. 03. 2012.

[5]

Horvat Krunoslav, Mušicki Goran, Linarić Davor, Seferović Dario., “Significance of testing turbine governing system on HPPs”, eng, ESSUP 2005, 11th International Conference “Electrical

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DOI: 10.14621/ce.20170108

Corruption and Bad Governance vs. Reliable Energy in the Economies in Transition Ana M. Lazarevska1*, Daniela Mladenovska2 *Ss Cyril and Methodius University, Faculty of Mechanical Engineering Karposh II b.b., P.O. Box 464, 1000 Skopje, Macedonia; ana.lazarevska@gmail.com 2 JSC “Macedonian Power Plants”, Skopje, Macedonia 1

Abstract

1. Introduction

The late eighties and the early nineties of the past century marked the breaking apart of certain states established during the post war years of the 20th century. The disintegration of these entities set-off severe ramifications in the affected states and their overall economy. Additionally, countries resulting from the disintegration of the former Yugoslavia were drawn into war conflicts, primarily affecting the basis of these emerging economies in transition, i.e. their energy sector, causing serious break-down in its stability and reliability. This paper focuses not only on the challenges and implications of decades-lasting corruption and bad governance in the economies in transition originating from the breaking apart of the former Yugoslavia – in particular the effects caused on the energy sector –, but as well on the opportunities offered to these countries should they decide to tackle this challenging status-quo and fulfil the EU accession requirements. Analysed are political and legal constellations, relevant stakeholders and measures affecting stability and reliability in operating the existing energy facilities and plants, but as well similar challenges affecting, even preventing new investments in the energy infrastructure. The proposed reliability indicators are applied to measure these constellations relevant for the Macedonian case.

Given that energy resources play an important role in providing economic growth, energy sector is the crucial part of any national economy. Hence, maintaining stable, reliable and secure energy supply is the main precondition for normal functioning, development and welfare of any state [1]. On the other side, governance and corruption have appeared as critical elements in describing the performance of the energy sector. Having in consideration that issues in the energy sector have significant impact on the overall economy of any country, as well as on the social welfare of its population, it is quite clear why researchers, decision makers and policy makers show sustained and increased interest towards finding indicators and correlations in terms of reducing the impact of corruption in this sector/branch. (Depending on the country, energy is under the authorities of either a ministry, a department, a sector, a sub-sector or a branch. The same counts for industry. Depending on the governance structure of each country, energy is a sub-set of industry and vv.) Bergara et al. (1998) [2], Dal Bó and Rossi (2007) [3], Estache, Goicoechea and Trujillo (2009) [4], Estache and Wren-Lewis (2011) [5], have analysed corruption impacts on utilities inefficiency, bureaucracies and security of supply (e.g. blackouts’ frequency).

Keywords:

Reliable energy; Corruption; Risk assessment

Article history:

Received: 18 April 2016 Revised: 24 January 2017 Accepted: 25 January 2017

Developing countries and countries with economies in transition have shown to be a fertile soil for corruption [6]. In particular, drivers for corruptive actions in the energy sector are overwhelming. A typical and indicative example are the electricity utilities, which in these countries, often are very large enterprises in terms of investments, revenues, number of people employed, the size of the customer base etc. Moreover, often such enterprises are in full or partial public ownership. As a consequence, corruptive actions in the electricity sector are left poorly or inadequately dealt with or often

___________________________________________________________________________________________________________ A. M. Lazarevska, D. Mladenovska: “Corruption and Bad Governance vs. Reliable Energy in the Economies in Transition”, pp. 57–69

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unchecked. The ramifications of such governance setup often keeps doors open for the process of deterioration of the utilities which further results in deprivation of the entire community [7]. Having the aforementioned in perspective, this paper focuses not only on the challenges and implications of decades-lasting corruption and bad governance (C&BG) in the economies in transition – in particular, their effects on the energy sector – but as well on the opportunities offered to these countries, should they decide to tackle this challenging status-quo and fulfil the European Union (EU) accession requirements. Analysed are political and legal constellations, drivers and obstacles affecting stability and reliability in operating the existing energy facilities and plants, but as well similar challenges affecting, even preventing new investments in the energy infrastructure. The identified indicators can be further applied to measure these constellations, as well as to assess the potential and the risks towards corruption.

2. Corruption in the sector energy Institutions and/or academics [8] actively conducting research in the field of corruption provide various and slightly differing definitions. However, they all have one unified approach practically summarized in the definition of Transparency International (TI), i.e. “Corruption is the abuse of public funds and/or office for private or political gain.” [9] Аs defined in the United Kingdom (UK) Prevention of Corrupt Practices Act from 1916 which in 2011 was replaced by the Bribery Act 2010 [10, 11], corruption has the narrower definition of “offering, giving, or acceptance of an incentive or reward that may influence the decisions and actions taken by any authority, its members or officers”. As one of the pillars of any nation day-to-day functioning – both in the productive and non-productive sector, thus including the industry –, energy sector plays a crucial role in the society and economy [12] providing a dominant role in the redistribution of the national income. Such a decisive function of the sector energy inherently and consequently implies its attractiveness to numerous contractors and, proportionally to this, its vulnerability to corruptive activities. E.g. Hobbs (2005) [13] estimates that 10-15 % on average contract value is taken as kickbacks on World Bank (WB) projects, while Kenny (2006) [14] noted that 5% of the investment and maintenance costs in infrastructure are lost due to corruption [15]. Moreover, since electricity plays a significant role in the energy sector, numerous studies present that corruption [3, 4, 6, 8, 16] almost always goes alongside with the electricity sector, and contributes to significant additional costs in activities connected with investment

in and operation of the energy generation and/or utilization companies. Since weak governance is the other face of corruption, developing countries and countries in transition, not being able to cope the challenges of weak governance, experience significant political influence over their energy utilities (no matter whether they are in full or partial public ownership), thus are vulnerable and instable in terms of corruption. As a consequence, in countries where energy sector consists of vertically integrated, public companies/utilities, those utilities often are used by the governments to pursue their political, social, and economic objectives, whereby they completely neglect the fundamental economic basis of any company existence – the profit. The above described circumstances, thus lead to significant lack of transparency with reference to all aspects in managing the utility: inefficiency, corruption, overstaffing, weak financial performances etc. [11]. Gulati & Rao (2006) [16] roughly estimate that, in developing countries, annual losses caused by corruptive activities in capital expenditure amounts to US$8 billion, while US$33 billion are attributed to electricity theft (non–technical losses being stolen by consumers in collusion with the involved staff). Bearing in mind that erection of new power plants or similar large investments in the energy sector are worth billions of Euros, the practice shows that public procurement processes are prone to significant contribution in numerous corruption activities regarding energy [1]. An indicative example is the public procurement process in Macedonia in the period 2010–2014, whereby, among the five most valuable contracts awarded, even in four, the contracting party is the Joint Stock Company (JSC) “Macedonian Power Plants” (in Macedonian AD “Elektrani na Makedonja” – AD ELEM), which is the energy generation public utility [17].

3. Measuring corruption in the sector energy The most productive way to measure corruption, i.e. to assess and estimate the effects corruption has on specific parameters, is to associate numerical values to the costs of corruption, e.g. in terms of currency. Consequently, every thorough analysis which should lead to identifying and measuring corruptive actions involves an appropriate and precise definition of the set of suitable corruption-related indicators [8]. As indicated in the previous section, and as clearly explained in WB (2007) [11] weak governance and poor development are a fertile soil for corruption, especially in the energy sector. Having this in perspective, herein we take the top-down approach and look for gaps in the governance structure to identify vulnerable points (spots) in order to build the structure and interrelations among attributes defining potential corruptive activities in the energy sector.

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3.1. Good vs. weak governance As pointed out in WB (2009) [8], good governance encompasses but is not limited to: − General adherence to rule of law; − Freedom of speech; − Transparency, responsibility and accountability in governance, correlated to and deriving from relevant stakeholders’ decision-making an all governance levels; − Decision making oriented towards effective and efficient outcomes for the society, environment and economy, i.e. in compliance with the sustainable development framework; − Decision making opened to public opinion, inclusiveness and responsiveness; and − Distribution of effective power to local government institution. On all levels of governance, corruptive activities can be identified and measured with indicators such as the Worldwide Governance Indicators (WGI) [18], which represent an aggregate and simple approach in providing information for 215 countries for the period 1996–2014. WGIs are based on over 30 individual data sources (w.r.t. companies, non-governmental organizations, international organizations, think-tanks, etc.) and are estimated for six dimensions of governance [19], i.e.: − Voice and Accountability (VA), measuring perceptions of the extent to which citizens of a respective country are able to participate in selecting their government, as well as freedom of expression, freedom of association and a free media; − Political Stability and Absence of Violence (PV), measuring perceptions of the likelihood that the government will be destabilized or overthrown by unconstitutional or violent means, including political violence and terrorism; − Government Effectiveness (GE), measuring the quality of public services, the quality of the civil service and the degree of its independence from political pressures, the quality of policy formulation and implementation, and the credibility of the government’s commitment to such policies; − Regulatory Quality (RQ), measuring perceptions of the ability of the government to formulate and implement sound policies and regulations that permit and promote developments in the private sector;

− Rule of Law (RL), measuring perceptions of the extent to which agents have confidence in and abide by the rules of society, and in particular the quality of contract enforcement, the police and the courts, as well as the likelihood of crime and violence; and − Control of Corruption (CC), measuring perceptions of the extent to which public power is exercised for private gain, including both petty and grand forms of corruption, as well as ‘capture’ of the state by elites and private interests.

3.2. Development, economic growth and political stability Alesina et al. (1992) [20], describe that there is a strong interconnection between political stability and economic growth. Firstly, due to the lack of investments resulting from the instable political environment, and secondly, since the poor economic performance could be a serious driver for the collapse of the government, which often leads to political crisis. The conclusion of their investigation is made based on a sample of 113 countries for the period 1950–1982. It could be pointed out that no firm evidence is found that economic growth substantially differs when authoritarian regimes are compared to democracies. Further, political instability tends to be persistent or self-sufficient in the way that the occurrence of frequent government collapses increases the probability of additional development collapses. An indicative example of this strong interconnection is the dissolution of both the former Yugoslav and the Russian Federation. Both were drawn into the turmoil of war conflicts, leading to new constellations in the countries behind the “ex-iron curtain” after the fall of Berlin wall. This in turn, brought on the scene the period of transition and increased presence of corruptive activities. For the purpose of comparing countries’ development and their state of wellbeing, between the periods prior and after 1989, the European Bank for Reconstruction and Development (EBRD) introduces a so-called standardized transition indicator (STI) (EBRD, 2013) [21]. The STI shows the sum of standardised individual scores for: large-scale privatisation, smallscale privatisation, companies restructuring, price liberalisation, reform of the trade and foreign exchange system, competition policy and overall infrastructure reform. According to the annual reports prepared by EBRD it can be concluded that, e.g. despite the better position of Macedonia, Serbia and Montenegro in 1989 compared to Romania and Bulgaria, in the forthcoming period, these countries have lost their advantages over the newest EU member countries which implied a

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significant delay in structural reforms preventing corruption. In 1990, the United Nations Development Programme (UNDP) introduced another composite indicator i.e. the Human Development Index (HDI) [22], indicating the average country’s achievements related to the following three aspects of human development: Life Expectancy, Literacy (Education) and Standard of Living (Quality of Life). HDI is a geometric mean of the three above listed simple indicators [23]. HDI level enhances citizens’ expectations from the policymakers, resulting in an increased level of participation in the democratic process. A true democratic government should always be aware of the political cycle on a long term period, and should strive to enhance economic growth and quality of life (expressed trough HDI) of the electorate. However, an autocratic regime may or may not share this motivation [24]. There are findings that the higher HDI contributes to decreasing levels of corruption [25]. Figure 1 depicts the ranking (values) of some of the South East European (SEE) countries based on the normalized WGI and HDI mentioned above.

3.3. Corruptive activities in the energy sector In terms of defining corruption related indicators in the energy sector, it should be pointed out that, as presented on Figure 2, at least the following specific business fields relate to corruption features [8]: I. Type of investments in the energy sector, i.e. investing either in new or in existing energy facilities (Box B on Figure 2). II. Type of operation and maintenance (O&M) activities in the energy sector (Box C on Figure 2) related to: − providing services, such as human resources (in order to avoid overstaffing and unnecessary outsourcing) and equipment (to provide appropriate quality/quantity); − addressing energy demand via securing energy production, independency and minimal loses; − providing materials (goods) via ensuring sound and transparent procurement procedures which includes avoiding collusion with suppliers and contractors (e.g. in the country members of the Organisation for Economic Cooperation and Development (OECD), natural gas share in the total electricity production costs amounts to 70% [26]. Such a vast share is prone to induce and challenge corruptive activities); another indicative example is the repeated closing and re-opening of the bidding process concerning a

certain project until a certain vendor wins the contract. The corresponding bribery mechanisms may range from small fees paid to clerical staff to large scale bribes to senior officials [27]; and − responding properly and transparently where taxes and fees (e.g. concession, liquidation etc.) are involved. III. Levels of Governance prone to corruptive activities Political and economic independency of an Energy Regulatory Authority (or the Regulator) is a vital part in preventing corruption in the energy sector. The available resources (e.g. license fees or other levies from regulated entities) are a form of financial independence assistance. Constant monitoring and control, whether financial resources are sufficient to regulate the market players, is very important in maintaining economic independence of the Regulator. Consequently, assessing the political independence of the Regulator is a complex issue. Although the operation of the regulatory authority and its responsibilities are determined by Law, the interests of the lawmaker represent an additional issue that could also be affected by corruption. Hence, the independence of the Regulator from the government and the ruling parties is still a challenge in many countries. Possible suitable indicators to assess these constellations potentially affected by corruption could be as follows: number of changes in the energy law, number of changes in bylaws and regulations in the energy sector, as well as the timing of the performed changes [28]. Political influence is usually applied at the highest levels and then allowed to work its way down the chain of commands and responsibilities by using different forms of pressure and power misuse. [29] Bearing in mind that in order to identify, allocate and assess governance/management levels prone to corruptive actions in the energy sector, the complete governance structure of a country should be included as mandatory, while the respective analysis should span from the top governmental/country, via sectoral levels, through the provider (companies) level, to the lowest i.e. project management/implementation level. Figure 2 aggregates all levels of governance which should be considered and measured via the worldwide accepted indices for corruption assessment (Box A) versus the business fields where corruption is expected (Box C), versus investment actions connected to either new or existing energy infrastructure (Box B). As an addition to the two elaborated aspects relating to corruption – the good governance and development –, based on experts opinion, TI, introduced the so-called Corruption Perceptions Index (CPI) [30] as a measure for the perceived levels of corruption in the public sector, worldwide. However, this index is not accounted for herein.

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___________________________________________________________________________________________________________ 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

Albania

Bosnia & Herzegovina

Bulgaria

Croatia

Voice and Accountability Government Effectiveness Rule of Law Human Development Index

Greece

Macedonia

Montenegro

Serbia

Political Stability and Absence of Violence Regulatory Quality Control of Corruption

Figure 1. Ranking of SEE countries in terms of the normalized WGI and HDI (Based on: [18, 30, 32])

Figure 2. Attributes indicating governance levels vulnerable to corruption in the energy sector (aggregated by the authors, based on [8,9,12,18,19,23,30]

3.4. Corruption vs. energy sector Energy security issues are in the focus of policymakers due to the fact that energy supply interruptions and systems failures could induce serious damages on the economy, public health and safety and the environment [31]. Energy security could be defined as a state of

condition when the risk from high energy import dependency, political instability in production and/or transit countries, and other relevant factors, are compensated at reasonable economic costs. The complexity of energy security takes in consideration not only natural hazards and resources depletion, but as well technical factors (infrastructure obsolesce and

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depreciation, technology incidents), political (disputes at international level affecting the supplies, sabotage and terrorism) and economic factors (high prices as well as price volatility). In concordance to the above mentioned, the “risk protection” is most commonly described as reliability, availability, robustness, independency and sustainability of the energy systems [33]. Thus, risk to the energy supply appears due to the possibility of physical interruption (system failure or other factors), and due to a major movement in energy commodity prices (economic risk) [34]. Since corruption activities overburden the contract values [16, 35] (e.g. overstaffing in the energy companies, inefficiency, etc.), it is obvious that corruption affects country public debt and strongly correlates to social risks, economic-driven risks as well as intrinsic energy risks. The corruption emerges from political institutionally related risks (See Figure 3) and affects and/or is influenced by a set of energy security risks. Hence, lack of new investments, lack of proper maintenance activities and trained and motivated professionals, as well as mismanagement and bad governance, imply weak operation performances, problems with utilities liquidity and solvency, deteriorated system’s security and reliability, and even blackouts as a final result of corruption [6]. Figure 3 shows relations between the risk of energy security and corruption. A sound procedure to monitor and evaluate (M&E) corruptive activities in the energy sector should not stop

only on identifying suitable indicators, since they are only one step from the broader five-steps M&E procedure [8] including: (1) Defining expected gains in governance, probity, and performance; (2) Choosing suitable indicators; (3) Establishing baseline indicators; (4) Monitoring progress at appropriate intervals; and (5) evaluating results and extracting lessons for the future. However, this falls out of the scope of this paper.

4. Pin-pointing possible corruptive activities in the Macedonian energy sector Based on the afore-mentioned indicators of corruptive activities in the energy sector, in the following subsections, several cases of such activities in the R. Macedonia shall be pin-pointed.

4.1. Energy Regulatory Commission History: The Energy Regulatory Commission (ERC) of the Republic of Macedonia was set up in 2002. It commenced its operation on 23 July 2003 when the Parliament of the Republic of Macedonia adopted a Decision nominating the President and the members of the Commission [36]. Dispute, Impact (Outcomes) and Challenges: Several issues w.r.t. establishing and regular activities of the ERC that challenge its political independence can be identified as follows:

Figure 3: Energy security risk: Energy security vs. corruption (Based on: Delgado B. M. (2011) [34]) ___________________________________________________________________________________________________________ A. M. Lazarevska, D. Mladenovska: “Corruption and Bad Governance vs. Reliable Energy in the Economies in Transition”, pp. 57–69

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− Due to the fact that both the President and the Members of the ERC are appointed by the Parliament (i.e. mainly by the parliamentary majority), it can be concluded that direct or indirect political influence in the ERC is significant. Thus, political background (indirectly) prevails over the professional and other competencies; − Notified are changes in the methodologies regarding price-forming and unjustified changes in deadlines for implementing those foreseen changes (e.g. before elections either local, parliamentary or presidential); − Notified are delays in appointing new members of the ERC after expiring of the mandates of current members. Thus, on several occasions, members of the ERC continued their work even after the end of their mandate. This is the case with the President of the Commission in 2008, when he continued working for an additional one year although his 5-year mandate expired. In 2007, there was a delay in appointing new members for six months, as well as in 2006 when there was a delay exceeding a period of one year [37]. − Although energy prices (incl. electricity) are subject to independent regulation to be performed by the ERC, Governmental influence over the work of this body is still obvious, due to governmental efforts to maintain stable social climate and provide support for the fragile quality of life. As a social category, the prices of electricity and district heating for households are among the most significant tools used by the Government to keep level of satisfaction among voters. The main goal is to keep prices of these commodities for households as depressed as possible, although as a consequence, energy generation public utilities operate below the economically justified margin. An indicative example is as follows: analysing the electricity price approved by ERC in 2015, 2014 and 2013, it can be concluded that the price changes per produced kWh electricity are negligible despite the significant financial losses of the Public Service Obligations (PSO) company (the JSC Macedonian Power Plants). Approved increase of the electricity price in 2015 was 0.34%, in 2014 - 3.04%, while in 2013 - 3.00%. The question is whether the 2015 price is really based on the methodology or there was state capture due to upcoming elections due to the current political crisis announced in the beginning of June 2015? The price corrections approved for the electricity distribution utility

(EVN) (on the electricity supply side) were: 0.33% lower price for 2015, 3.47% higher price in 2014 and 4.48% lower price in 2013 [38].. In terms of district heating, in 2015, for the state owned district heating company, approved was a price decrease of 0.8% [39, 40].

4.2. Postponing liberalisation of the electricity market Although a member of the Energy Community (EnC), Macedonia has several open infringement cases, which are noted by EnC in its latest report. Currently, four cases are indicated. Two of them occurred both as lack of competences and capacities, as well as an intention to prevent social disturbances (postponing electricity market liberalization [41]). On 30 January 2015, the Secretariat sent Macedonia an Opening Letter for its failure to comply with the Energy Community’s eligibility rules by postponing full liberalization of the electricity market until 2020. The Energy Community Treaty sets 1 January 2008 as the implementation deadline for market opening for non-household customers and 1 January 2015 for all customers including households. This issue clearly is connected to the above elaborated questionable political independence of the ERC.

4.3. Unjustified and unnecessary engagement of services, energy demand, materials and taxes and fees in public utilities History: Resulting from a long lasting period of lack of investments in new energy production capacities, a trend of decreased electricity production attributed to the state owned JSC Macedonian Power Plants is noted, implying continuous increase in electricity import. This trend is particularly present in the latest years, especially since it coincides with steady increase in the number of employees in the company. Another point that draws attention is that the latest published report on the company website is from 2013, while data for the current number of employees are not available [42]. Dispute, Impact (Outcomes) and Challenges: As elaborated in Section 3, an indicative example for corruptive activities in the energy sector when it comes to public utilities, is overstaffing (unjustified and unnecessary employment, lack of competencies of the new employees etc.). It is a clear form of political corruption on governance level of a ruling party over the citizens. The numbers presented in Table 1 clearly show the relations between the produced and imported electricity in parallel with the number of employees in the period 2002 – 2015. Namely, in parallel with the

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Table 1: Overview of the electricity generation vs. import in the period 2002–2015 [44, 46, 47] Imported electricity (GWh) 1027.9 953.0

Import as percentage from total demand (%) 15.46 13.18

2002 2003

Produced electricity (GWh) 5618.7 6272.6

2004

6063.3

n.a

2005 2006 2007 2008

6352.5 6195.9 5513.3 5615.4

1652.7 1958.3 2615.5 2801.5

20.64 24.01 32.17 33.28

n.a n.a 3910 4033

2009

5886.2

1716.7

22.57

3809

2010 2011 2012 2013

6462.3 6075.0 5369.9 5113.0

1602.0 2748.7 2741.4 2490.6

19.86 31.15 33.79 32.75

3880 4065 4732 4682

2014

4535.0

3072.7

40.38

4566

2015

4950.8

n.a

Year

continuous decrease in annual electricity production, which reached its historical minimums in 2014 and 2015, the state owned company JSC Macedonian Power Plants faced significant financial net losses. In 2014 the minus on the account of JSC Macedonian Power Plants reached 14 million euro [43]. Despite these circumstances, the number of employees is in a constant rise reaching 4566 in 2014, compared to the 3910 employees in 2007 [44]. Since, the current total installed production capacity of the company remained almost the same, it resulted in increase of the “number of employees/total installed capacity in MW” ratio. Increasing non-technical losses in public electricity distribution companies could be subject to corruptive activities. The fee collection process, relating not only to the incentives of specific collectors and consumers, but more significantly related with the officials’ behaviour as a form of their goodwill, as well is prone to corruptive activities. E.g., an India-based research shows that not only electricity theft was significant, but the losses were larger prior to elections and follow an “electoral cycle” pattern [45]. Quantitative analysis of the labour surplus in the electricity sectors of the Western Balkan countries, based on a set of variables including net electricity generation, show low labour efficiency in the Macedonian electricity sector. Values for 2007 are presented on Figure 4. Hence, as presented on Figure 5, the status – quo regarding lack of investments in new energy production capacities, the mismanagement and political abuse of

Number of employers 3801 n.a

Elections Parliamentary Elections, 15.09.02 Referendum, 7.11.04 Presidential Election, 14&28.04.04 Local Elections, 13&27.03 and 10.04.05 Parliamentary Elections, 5.07.06 Early Parliamentary Elections, 1.06.08 Presidential and Municipal Elections, 22.03 and 5.04.09 Early Parliamentary Elections, 5.06.11 Local Elections, 24.03.13 Presidential and Early Parliamentary Elections, 13&27.04.14

public money, and the labour surplus and labour inefficiency lead towards continuous worsening of the company’s vital economic parameters. Current ratio shows the company ability to meet its short term liabilities, while quick ratio is an indicator of the company’s short term liquidity. The liquidity ratio denotes a company’s ability to pay off the obligations towards short-term creditors out of its total cash. Values lower than 1, in terms of all three above mentioned indicators denote that the company is unable to pay-off its obligations.

4.4. Energy dependency Significant energy dependency of the country could also represent an important source for corruption. The problem becomes even more serious in case of lack of transparency and accountability both on a sectoral as well as on governmental level. A relevant indicator can be defined as the percentage of import share in the total production, or net import versus total consumption [50]. In 1990 as a part of the Socialist Federative Republic (SFR) of Yugoslavia, Macedonia had a total of installed gross capacities equal to 1445 MW and a gross electricity production of 5737 GWh [51]. The annual levels of growth in electricity consumption (4.5% per year) especially in the years following 2007 [52], accompanied by a continuous decrease of domestic production, whereby the total gross installed capacities compared to 1990 remained almost unchanged, denote a significant absence of solid management, lack of

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Figure 4. Labour efficiency in the electricity sector [48]

Figure 5. Current ratio, quick ratio and liquidity ratio for JSC Macedonian Power Plants in the period 2010 – 2014 (based on [49])

investments and lack of solid decision-making in the Macedonian energy sector. Hence, the energy dependency further remains one of the main challenges of the country which could not be treated separately from the issues of corruption and bad governance. A prudent state governance and company management should favour investments in electricity generation facilities which increase energy independence, security and reliability instead of the steady increase in the amounts of imported electricity posing a direct threat to the national budget, economical and thus political independence. The above mentioned lack of investment in the last decades, combined with continuous investments in non-energy related projects due to the state capture on the overall governance of the energy

sector, lead towards worsening the reliability and security of the energy system. Among the ten most valuable contracts signed in the period 2010-2014, even five are signed by JCS Macedonian Power Plants in a total value of 261 million euro [17]. None of them is related with erection of a new energy production facility. Moreover, the subject of four of those contracts is coal excavation from existing coal deposits.

5. Conclusion Although attempts to tackle corruption go centuries back, corruptive activities endure and even emerge in newer and more inventive form, as though corruption manages to remain an uncharted territory that has to be

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mapped over and over again. This paper is a contribution to the everlasting process of “charting” corruption and grasping as much aspects as possible in order to build the puzzle relevant, separate and specific for each country, each society, each governance scheme, each company and each project in cases when energy sector is affected. An aggregation of the set of attributes defining the frames of the types of activities and types of investments prone to corruptive activities is performed. It is shown that their tentacles span from the top country governance level to the lowest project implementation level. Since developing countries and countries in transition often in parallel “suffer” from weak governance and development stagnation (or even downgrade), as a final instance, they consequently are more vulnerable to corruptive activities. As an indicative example, four cases in Macedonia, where corruptive activities in the sector energy have been identified, were elaborated and weaknesses were identified. The practice shows that public ownership brings an additional level in the complexity of the corruption scheme, since it offers additional challenges for the top governance to involve into corruptive actions down to the level of project implementation.

UNDP USAID WB WGI

Acknowledgement Part of the herein presented work has derived from the involvement of the authors in the project activities of the Project “Assessment of corruption and anticorruption in Southeast Europe”, prepared by the Southeast Leadership for Development and Integrity (SELDI) Initiative (SELDI.net) implemented by a consortium led by the Center for the Study of Democracy, co-funded by the European Union and the Central European Initiative. (http://seldi.net/home/) (2015 – 2016).

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Acronyms and abbreviations C&BG CPI CSD EBRD EnC ERC EU GTZ HDI IEA JSC NATO NEA M&E OECD O&M PSO SEE STI TI UNCAC

Corruption and Bad Governance Corruption Perceptions Index Center for the Study of Democracy European Bank for Reconstruction and Development European Commission Energy Regulatory Commission European Union Deutsche Gesellschaft für Technische Zusammenarbeit Human Development Index International Energy Agency Joint Stock Company North Atlantic Treaty Organization Nuclear Energy Agency Monitor and Evaluate Organisation for Economic Cooperation and Development Operation and Maintenance Public Service Obligations South East Europe Standardized Transition Indicator Transparency International UN Convention Against Corruption

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DOI: 10.14621/ce.20170109

Indicators Relevant for Energy Security Risk Assessment of Critical Energy Infrastructure Daniela Mladenovska1*, Ana M. Lazarevska2 *JSC “Macedonian Power Plants”, Branch "Energetika" 16 Makedonska brigada bb, 1000 Skopje, Macedonia; dmladenovska@gmail.com 2 Ss Cyril and Methodius University, Skopje, Macedonia, Faculty of Mechanical Engineering 1

Abstract Energy security is one of the most important issues affecting not only national economies, but as well the national security systems. Hence, various approaches in different studies and reports are utilized to analyze this topic. Energy systems are subject to diverse risks and threats which can vary according to specific geopolitical circumstances, geographical location, technical failures, environmental risks, social crises and timescale. Any source of danger to the continuity of the energy production, its consumption and/or final supply or other energy services is defined as a risk to the national energy security and integrity. This topic is even more important when it comes to energy infrastructure defined as critical, which can often be subject to asymmetrical risks and threats. Bearing in mind the long history of war and conflicts, as well as recent refugees crises, the region of South East Europe, in particular the Western Balkans is quite vulnerable regarding those issues. In order to protect the energy system and to ensure its security, it is necessary to understand the causes of danger, the nature of risks, as well as to quantify their impact. Thus, identifying tangible and measurable indicators represents a sound basis towards tackling risks and preparing measures for response and mitigating consequences.

Keywords:

Article history:

Energy security; Critical energy infrastructure; Risk assessment; Asymmetrical threats Received: 11 April 2016 Revised: 20 January 2017 Accepted: 23 January 2017

1. Introduction: Energy security and Critical Energy Infrastructure Resilience is focused on protection from disruptions originating from less predictable factors of any nature, such as political instability, game-changing innovations, or extreme weather events [1]. Having this in perspective, energy security refers to a resilient energy system. As pointed out in Brown et al. (2003) [2] such a system would be capable of withstanding threats trough a combination of (a)

active, direct security measures: e.g. surveillance and guards; and

(b) passive or more indirect measures: e.g. redundancy of critical equipment, diversification of fuel sources, other sources of energy, and reliance on less vulnerable infrastructure. One of the most frequently quoted definitions of energy security is Yergin’s (2006) definition, i.e. energy security is the “availability of sufficient supplies at affordable prices” [3]. It was preceded by a similar energy security definition of the European Commission (2000) [4] as the “uninterrupted physical availability on the market of energy products at a price which is affordable for all consumers.” As an antipode, Bohi and Toman (1996) [5] define energy insecurity as the “loss of economic welfare that may occur as a result of a change in the price or availability of energy.” Energy security focuses on the so-called Critical Energy Infrastructure (CEI); a term that is receiving increasing attention in today’s world [2]. An indicative example which can be pointed out is that much of the energy infrastructure in the Western Balkans was damaged during the conflicts related to the dissolution of the

___________________________________________________________________________________________________________ D. Mladenovska, A. M. Lazarevska: “Indicators Relevant for Energy Security Risk Assessment of Critical Energy Infrastructure”, pp. 70–81

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Figure 1. Interrelationship between Energy and Other Critical Infrastructure [8]

Socialist Federal Republic (SFR) of Yugoslavia in the 1990s [6]. These wars physically damaged a significant part of the energy infrastructure and energy production capacities in the affected region. The consequences were even more devastating for Serbia, as a result of the conflict in 1999, in particular as a consequence of bombarding. The existing energy infrastructure of the country was seriously disrupted resulting in severe heating and electricity shortages, although some energy resources provisions were provided from Russia [7]. Critical Energy Infrastructure is usually defined as “those assets if undelivered are expected to make significant impact on energy security and energy supply, as well as on the overall social and economic well-being of the nation. Such assets include physical energy facilities, energy supply chain, information technologies and communication infrastructure that make up and integrate an energy system.” [9] CEI assets in general can be destroyed or degraded by both natural and

human initiated threats. Any disruption of a single CEI sector – whether from a terrorist attack, natural disaster or man-made damage –, is likely to create a cascading effect on any particular country’s energy system that is both complex and interconnected. [10] The energy system could not be analysed as a separate and isolated entity since it is evolved in a complex set of nation’s infrastructure. The interconnections of the nation’s energy, water, electronics and telecommunications systems, as well as, their complexity [2], are clearly indicated on Figure 1. A good example of infrastructure’s interdependency is the case of electric power and telecommunications networks, since the power grid control and governing relies on the corresponding telecommunications infrastructure, while the power grid is crucial for telecom electricity supply [11]. By means of analysing the interdependences and their nature, as well as the importance of the connections, the indicators of critical infrastructure resilience could be defined. They are important not only for establishing a

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sound project design of the infrastructure, but can also limit the loss of functionality and improve recovery of infrastructure’s function in cases of shock or disturbance [12]. Hence, as resilience is the key issue towards enabling energy security in politically unstable and fragile environment typical for the analysed region, identifying relevant indicators that describe the system’s vulnerability and assure its stability in spite of potential (non)identified threats, should be one of the major priorities of policy makers. This paper specifically focuses on the afore mentioned topics, which although occasionally elaborated among countries in the Western Balkans region, require additional efforts in order to be in line with the European Union (EU) energy security policy. The issue of asymmetrical risks and threats has gained significant importance in today’s world, thus the necessity for protecting critical energy infrastructure has urged authorities in the South East European (SEE) region to reconsider their national security strategies.

2. Legislation framework related to Critical Energy Infrastructure In accordance to the ANNEX I from the COUNCIL DIRECTIVE 2008/114/EC, as critical energy infrastructure related energy sources identified are as follows: − Electricity (generation and transmission infrastructures and facilities in respect of electricity supply), − Oil (oil production, refining, treatment, storage and transmission by pipelines), and − Gas (gas production, refining, treatment, storage and transmission by pipelines; Liquefied Natural Gas (LNG) terminals). The European Commission denotes critical energy infrastructure which is of common interest of at least two EU member countries, or is important for a specific EU country member, but is located in another country, also an EU member [13]. Across countries in the regions of SEE and Western Balkans, initiatives and, in particular, legal frames in terms of protecting CEI, are unequally developed. An indicative case in the region with regards to CEI development and relevant legal frames is the former SFR of Yugoslavia. Due to political and war conflicts in the beginning of 1990s, once highly coordinated operations and systemic planning were decomposed into a separate parts within separate newly emerging countries. The infrastructure in each republic proved unable to support current energy needs without new investments or import from the neighbouring countries. Within the YUGEL (Yugoslav Association of Electric Power Industry) pool, the internal

exchange of electricity in SFR of Yugoslavia in 1990 was four times more intensive than the exchange with foreign countries. In the same year Serbia and Bosnia & Herzegovina were net-exporters, Croatia and Montenegro were net-importers, while Slovenia and Macedonia were almost self-sufficient [14]. In the past decades, the situation in the new established countries concerning critical energy infrastructure became quite different, depending on their economic strength, political stability as well as the governance quality. As a EU member state, via identifying and defining national and European CEI, related CEI sectors, their management, preparation of studies on risk analyses, as well as appropriate designation of the stakeholders roles and responsibilities, Croatia transposed the Council’s Directive into "Law on critical infrastructures" [15]. Similarly, in 2011, Bulgaria completed several crucial tasks in terms of transposing requirements of the Council’s Directive onto the national legislation. Moreover, Bulgaria adopted the New National Security Strategy, whereby, for the first time, a chapter on Energy Security and Policy was included [16]. Although not yet a member state, the Serbian Government adopted a “Regulation for protection and rescue’s preparation in emergency situations” based on the “Law on emergency situations”. This document denotes pioneering introduction of the term “critical infrastructure” in the Serbian legislation. However, detailed explanation of type or elements referring to critical infrastructure was neither provided nor included. Taking in consideration that the country had been affected by the turmoil of conflicts resulting, one side, in physical damage of vital infrastructure elements, as well as in increasing vulnerability of energy facilities, from the other, the National Security Strategy noted certain crucial parts of the “critical infrastructure”, although not elaborated in details. A particular focus has been provided on the context of economic development [17]. Keeping the pace with the new paradigm regarding the international world order and the fragile security environment, Republic of Macedonia, as well, initiated providing a challenging driver for developing corporate protection of the critical infrastructure, in particular the CEI. There are several specific reasons that amplified the necessity for actions in this field: − Firstly, the absence of values that were expected to endorse private sector in the security area and the inexperience in new decentralized security management. − Secondly, the fact that the country involvement in the military operations in Afghanistan and Iraq, as well as the latest events related to the Middle East refugee’s route, significantly increased

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security threats to the critical infrastructure in the Republic of Macedonia [18]. − Thirdly, no legal document exist in Macedonia that contains a list of identified critical energy infrastructure. Nevertheless, based on the “Law on Crisis Management” [19] and the “Energy Law” [20], (Art. 13, 154, 179), yet Macedonian authorities prepared the “Regulation for criteria and conditions in proclaiming electricity supply crisis”, and the “Regulation for criteria and conditions in proclaiming natural gas supply crisis” [21]. Hence, it can be concluded that currently Macedonia does not have a specific strategy for CEI. Thus, there is an urgent need to define the elements of the national CEI, and to further assess risks based on relevant indicators. The North Atlantic Treaty Organization (NATO) – based approach regarding CEI is followed by most of the EU members [22]. Since, Macedonia is on the path towards Euro-Atlantic integration, a similar choice of route should certainly be followed [18].

3. Risk assessment indicators for Critical Energy Infrastructure Critical energy infrastructures are vulnerable to cascading failures/threats both from a natural origin, as well as from system failures [23]. Since, asymmetric threats are the focus of this paper, system failures

including: sabotages and terrorism, equipment breakdowns and human errors, are regarded herein. Over the last years, the words “asymmetry” and “asymmetric” have often been used in the discourse of national strategic and political sciences. As pointed out by Blank (2003) [24], asymmetric threats generally include terrorism, unconventional or guerrilla tactics or guerrilla warfare, the use of Weapon for Massive Destruction (WMD), cyber warfare or information war (IW). On a strategic level, “asymmetric” denotes the capability to act, organize and think differently compared to one’s opponents in order to maximize one’s own advantages, use enemy weaknesses, attain initiative, or obtain more freedom of action. According to Burgherr et al. (2008) [25], and Hirschberg et al. (2008) [26], risk relevant criteria and indicators are assigned to all three dimensions of sustainability [27, 28]. Nevertheless, the devastation and consequences can be similar, regardless the cause of the event [2]. Asymmetrical threats are the newest energy security threats emerging during the 1990’s, while dominating this century. They deserve special attention due to several reasons, among which the following can be pointed out: highly developed means of destruction and highly developed national infrastructures [29]. Vulnerability assessment is an important part of the risk assessment process (Figure 2). It enables analysing the system’s elements and their failure modes based on a given set of identified threats [30]. Today, the vulnerability of the CEI is not only a matter of a bulk

Figure 2. The risk assessment process [30] ___________________________________________________________________________________________________________ D. Mladenovska, A. M. Lazarevska: “Indicators Relevant for Energy Security Risk Assessment of Critical Energy Infrastructure”, pp. 70–81

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Figure 3. Critical Energy Infrastructure vulnerability and threats: Macedonian case

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Table 1: Risk assessment indicators related to critical energy infrastructure: Macedonian case [24, 35, 36]

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power electric system or a physical system. It is significantly more a matter of cyber security, since without SCADA/EMS an energy system could not be efficiently operated and governed. [31] As clearly shown on Figure 1, the interrelation between energy infrastructure and the communication sector is significant. As there are numerous definitions for terrorism, there are a proportionally various definitions for “cyber terrorism”. “Cyber terrorism is generally defined as attacks and threats of attack against computers, networks, and the information stored therein when done to threaten a government or its people in persisting of their political or social objectives” [32,33]. In addition, when it is discussed about the energy dependent country the problem becomes even more complex and implies a wider economic and energy security impact. Every energy system that is dependent on a single fuel supply source, a single transmission line or even a single telecommunication system is more vulnerable than one that relies on a supply diversification and connections redundancy. This implies that solid and stable energy system should be planned and operated in a manner that achieves resiliency by means of diversity and redundancy. Identifying relevant indicators is the first step which is followed by calculating relative importance (weight) of each indicator and finally results in selecting the optimal scenario for risk mitigation by means of various decision making methods including Multi Criteria Decision Making (MCDM).[1, 34]. Bearing in mind the afore mentioned, while considering all herein elaborated aspects applied on the Macedonian case, Figure 3 provides a schematic representation of the identified interrelations between the CEI elements of the Macedonian energy sector from a vulnerability and threats assessment point of view. Natural hazards are not taken in consideration. Having in consideration the feature and specifics of the Macedonian energy sector, Table 1 provides an overview of some of the identified CEI related risk indicators. In terms of energy system’s sovereignty although the main threats are recognized in sabotage and terrorism, the political and economic stability as well as political embargoes and availability of domestic energy sources/energy dependency, plays an important role [37]. While infrastructure’s robustness is related with failures and obsolescence of the system, its resilience is defined as the ability to withstand disruptions [1]. The both are very important issues, especially when analysing risks in the countries with fragile and quite vulnerable and import dependent energy system. Lack of maintenance, human errors (manmade accidents) and corruption can also have significant impacts leading to failure of the CEI. The probability of failure will vary

depending on the nature of the disturbance and the nature of the CEI. Hence, design faults, lack of maintenance of inadequate maintenance, long service etc., will influence the occurrence of the failure and its scale. Thus, organizational and management strength/weakness can also significantly affect this issue [12]. Regarding the third indicator “terror potential” there are several elements which are introduced. “Attractiveness of the target” is one of the most important elements, and according to the available analysis [30] it is assumed that the main goal of terrorist attacks is to cause as many fatalities as possible. This indicator is graded from 1 to 10, whereby the value is larger if the target is more attractive, e.g. nuclear technologies have maximum value. In terms of pulverised coal thermal power plants, the values is 1 or 2, thus they are the least attractive targets together with photovoltaics, solar thermal and offshore wind. CCHPP are in the range 2-6 depending on the technology type [27]. Figure 4 indicates the globally increasing trend of the attractiveness of energy infrastructure as a target. Although a lot of research in analysing CEI disruptions is focused on prevention and protection, most of the recent work is oriented towards “readiness, timely response and fast recovery” from such failures [39]. Due to the fact that there is a lack of statistical data for such failures, empirical data reported by the media can also be used as a solid base [40]. Since the Macedonian energy infrastructure has not yet been a target of terrorist attacks, only examples of energy supply disruption can be pointed out – one as a result of geopolitics and the other as a result of human errors and equipment breakdown. The partial collapse of the electricity system in SEE on July 24th 2007, is the most severe incident since the region of SEE has been connected to the European electricity power system [41]. As a result, also in Macedonia a serious power blackout of the national power system occurred. Neighbouring power systems in Albania and Kosovo as well experienced the consequences of this blackout, while there was a partial blackout in Montenegro and Serbia [42]. This incident was denoted as a typical frequency disturbance of the system. Under the provoked circumstances, Albania had imported more than 50% from the electricity demand, two 400kV transmission lines (Kosovo B- Nis and Kosovo B- Ribarevina) were facing simultaneous disruption due to human error, while the 400 kV transmission line Blagoevgrad – Thessalonica had a disruption due to overload [41]. In January 2009, the interruption of gas delivery via Ukraine resulting from a bilateral dispute between Russia and Ukraine escalated into a serious gas supply

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Figure 4. Number of terrorist attacks on energy infrastructure as a share of total attacks (globally) [38]

Figure 5. Impact of Ukrainian gas crisis on individual countries [44]

crisis in Europe. Significant number of countries in Europe were seriously affected (Figure 5) and suffered various losses. Boltz (2009) [43] provides a consolidated overview of those losses for each country, while

considering that the “cost of disruption” covers not only losses from industrial production stoppage, but as well losses for providing alternative fuels etc.

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4. Conclusion Identification and protection of critical energy infrastructure is among the key tasks for Macedonia as well as for its neighbouring region. Sovereignty, robustness and resilience are the main pillars of energy security, thus they are important elements in the efforts to withstand the threats, especially those defined as asymmetric threats. In order to be compatible in actions, national legislation should be prepared in line with the EU Directive on critical infrastructure, whereby designation of roles and responsibilities among the institutions is very important. Cyber security, as well as, communication as a vital infrastructure should be analysed as a subset of critical energy infrastructure, since both are significantly interlinked. In the case of Macedonia, where the country relies on limited number of energy sources (e.g. only one import line for natural gas, originating from only one source, limited reserves of coal, increasing trend of electricity import etc.) and has limited interconnections facilities, the national economy is significantly more exposed to “attacks” causing disruption and failure of any part of the corresponding critical energy infrastructure. As elaborated herein, the history of the energy system disruptions in Macedonia shows dominant influence of its geopolitics (e.g. in terms of TRI relating the gas infrastructure), as well as equipment breakdowns and failures due to transition from one system (part of SFR Yugoslavia) towards being a member of the European electricity system. In order to strengthen the capacities, one of the national priorities in this field should be building-up skills, training the personnel, coordination improvement, solid legislation in terms of CEI and crisis management, as well as, investments in new power-generating facilities, new energy sources (domestic/abroad), equipment redundancy, reliability and more sophisticated systems for governing and protection.

NATO SCADA SEE SFR TPP TRI WMD YUGEL

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Acronyms and abbreviations CCHPP CEI CNG EMS EU EC HPP IW LNG MCDM

Combined Cycle Heat and Power Plant Critical energy Infrastructure Compressed Natural Gas Energy Management System European Union European Commission Hydro Power Plant Information War Liquefied Natural Gas Multi Criteria Decision Making

North Atlantic Treaty Organization Supervisory Control And Data Acquisition South East Europe Socialist Federal Republic Thermal Power Plant Transit Risk Index Weapons of Mass Destruction Yugoslav Association of Electric Power Industry

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