FAQ Frequently Asked Questions on Small Hydropower (SHP)
Produced by MHylab, Switzerland within the engineering group of the TNSHP- European Commission (NNE5/2001/886.)Contract. The Swiss partners are financed by the State Secretariat for Education and Research (SER) with the Project 02/0007.
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This document has been prepared within the FP5 Project Thematic Network on Small Hydro Power, with the support of the European Directorate for Transport and Energy and the Swiss Federal Office for Science and Education, by: •
ESHA, European Small Hydropower Association
•
MHyLab, Fondation du laboratoire de mini-hydraulique de Montcherand, Switzerland
•
ÖVFK, Österreicher Verein zur Förderung von Kleinkraftwerken, Austria
•
SERO, Sverige Energiföreningars RiksOrganisation, Sweden
•
EPFL-LCH, Laboratoire de constructions hydrauliques of the Ecole Polytechnique Fédérale de Lausanne, Switzerland
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1
GENERALITIES............................................................................................................... 6 1.1
What is SHP?........................................................................................................................ 6
1.2
What about the power threshold between SHP and big hydropower? ........................... 6
1.3
Why should SHP be distinguished from the usual hydropower? .................................... 6
1.4
What are the main advantages of SHP? ............................................................................ 6
1.5
How old is the SHP experience? ......................................................................................... 7
1.6
Is there a renewed interest for SHP? ................................................................................. 7
1.7
What kind of potentials exists for the SHP plants? .......................................................... 8
1.7.1 1.7.2 1.7.3
How could drinking water be an interesting potential for SHP? ..................................................... 8 Is water still drinkable after being turbined? ................................................................................... 8 How could wastewater be an interesting potential for SHP? .......................................................... 9
1.8
Any concrete examples of a good integration of SHP plants? ......................................... 9
1.9
What is the current SHP position in Europe? ................................................................... 9
1.10
What are the main barriers against the development of SHP in Europe? ................... 11
1.11
Is SHP interesting for developing countries? .................................................................. 11
1.11.1 Is SHP interesting for developing countries with respect to geopolitics, ethics and environment? ............................................................................................................................................... 11 1.11.2 Is SHP financially affordable for developing countries? .......................................................... 12
1.12
What is the remaining potential for SHP?....................................................................... 12
1.12.1 1.12.2
2
1.13
What are SHP objectives in Europe? ............................................................................... 13
1.14
How to develop a small hydropower project? ................................................................. 13
ENVIRONMENT ............................................................................................................ 15 2.1
Can SHP be considered as a clean energy? ..................................................................... 15
2.2
How can the local environmental impact of a SHP plant be reduced? ......................... 15
2.3
How much does a hydro-electric GWh reduce the CO2 emissions? .............................. 15
2.4
What happens to the water that is used for power production?.................................... 15
2.5
What happens to fish when a SHP plant is set on a water stream?............................... 15
2.6
What is the residual discharge or reserved flow? ........................................................... 16
2.6.1 2.6.2
2.7 2.7.1 2.7.2 2.7.3 2.7.4
3
In Europe? ................................................................................................................................ 12 In the world?............................................................................................................................. 13
How can the reserved flow be estimated? ..................................................................................... 16 What is the cost of providing a reserved flow? ............................................................................. 16
What is a fish by-pass system?.......................................................................................... 17 What are the different types of fish bypass systems? .................................................................... 17 What do fish bypass systems consist in? ....................................................................................... 18 How much water is used to run a fish bypass system?.................................................................. 18 What is the cost of building and operating a fish bypass system?................................................. 18
TECHNIQUES................................................................................................................ 19 3.1
How do SHP plants produce electricity? ......................................................................... 19
3.2
What is the difference between gross head and net head? ............................................. 19
3.2.1
3.3
How can the gross head be measured? .......................................................................................... 19
How high can the SHP-plant energy efficiency be? ........................................................ 19
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3.4
How can the generated electric energy be estimated? .................................................... 19
3.5
What is the difference between efficiency and power?................................................... 20
3.6
What is the average power of a small turbine? ............................................................... 20
3.7
How can the hydraulic power be estimated?................................................................... 20
3.8
Could SHP plants produce peak hours electricity? ........................................................ 21
3.9
What are the mean dimensions of a SHP power plant? ................................................. 21
3.10
How can the number of turbines in a power plant be chosen? ...................................... 21
3.11
Are there different kinds of small turbines?.................................................................... 21
3.11.1 What are their main specific characteristics? ........................................................................... 22 3.11.1.1 What are the main characteristics of a Pelton turbine? ........................................................ 22 3.11.1.2 What are the main characteristics of an axial turbine (as the Kaplan one)? ........................ 23 3.11.1.3 What are the main characteristics of a Francis turbine? ...................................................... 24
3.12
What is a guide vane system?............................................................................................ 24
3.13
What is the difference between an action (or impulse) turbine and a reaction one?... 24
3.14
What is the best material for a runner?........................................................................... 24
3.15
What is systemisation? ...................................................................................................... 25
3.16
What is the specific hydraulic energy of the machine? .................................................. 25
3.17
What is a flow duration curve?......................................................................................... 25
3.18
How can the discharge be measured? .............................................................................. 26
3.19
What are head losses?........................................................................................................ 26
3.19.1
3.20
What is cavitation? ............................................................................................................ 26
3.20.1
4
How does the penstock act on head losses?.............................................................................. 26 How can the cavitation phenomenon be avoided?.................................................................... 27
POLITICAL ASPECTS .................................................................................................. 28 4.1
What is the objective of the White Paper concerning SHP? .......................................... 28
4.2 What is the objective of the Directive 2001/77/EC, “Promotion of Electricity Produced from Renewable Energy Sources� (RES-e Directive)?................................................................ 28 4.3
How is the European SHP sector interconnected?.......................................................... 28
4.4 What are the main support policy instruments for renewable energies in general and SHP in particular? .......................................................................................................................... 29 4.5 What are the complementary support policy instruments for renewable energies in general and SHP in particular? ..................................................................................................... 30 4.6
5
6
Where to get hydrological data?....................................................................................... 30
ECONOMIC ASPECTS.................................................................................................. 31 5.1
How much money can be earned with a SHP?................................................................ 31
5.2
How much does a SHP project cost? ................................................................................ 31
5.3
How long is an acceptable payback time? ....................................................................... 32
5.4
How many SHP manufactures are in Europe? ............................................................... 32
5.5
What are the present employment figures and future perspectives?............................ 32
Glossary ........................................................................................................................... 32
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7
Bibliography .................................................................................................................... 32
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1
GENERALITIES
1.1 What is SHP? SHP stands for Small Hydro Power, in which 'small' means below 10 MW if the EuropeanUnion definition is taken into account. SHP schemes generate electricity by converting the power available in flowing water of rivers, canals and streams. SHP schemes are mainly run-of-river without any reservoir impoundment (if it is not a small one). The objective of a hydropower scheme is to convert the potential energy of a mass of water, flowing in a stream with a certain fall (called the 'head'), into electric energy at the lower end of the scheme, where the powerhouse is located. What can be pointed out is that the power of the scheme is proportional to the flow (called the 'discharge') and to the head. 1.2 What about the power threshold between SHP and big hydropower? In the European Union, the 10-MW threshold is considered as the SHP one, even if the SHP plant capacity varies from country to country from 1.5 to 12 MW. But this power criterion is not enough to define the difference between SHP and big hydropower. For more details, see paragraph § 1.2 of the "Guide on how to develop a small hydro site"viii.
1.3 Why should SHP be distinguished from the usual hydropower? SHP should be distinguished from the usual hydropower because a small power plant is not the geometric reduction of a big one. Indeed such a process would lead to an excessive damage of the performances in case of a non-controlled simplification of the turbine geometry or to an expensive, complex and of a delicate exploitation construction. On the contrary, the geometry of a few-kW turbine can not be extrapolated to the geometry of a 10- or 100-kW turbine. In both cases, the constrains are different. Thus it is essential to develop and produce equipments specific to small power plants so as to assure the fundamental exigencies of simplicity, high energy efficiency, maximal reliability and easy maintenance. As a conclusion a small power plant could be defined as a power plant that due to technical and economical reasons could not be the geometric reduction of a big one. 1.4 What are the main advantages of SHP? SHP contributes towards sustainable development by being economically feasible, respecting the environment (no green house gases emissions) and allowing decentralized production for the development of scattered populations. Furthermore some other advantages can be underlined regarding the different following fields: ƒ Environment: o SHP is a clean and renewable energy source (the fuel for hydropower is water, which is not consumed in the electricity generation process) o SHP plants, if well-equipped, with fish ladders are not an obstacle for migratory fish. TN_FAQ_En
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o Small hydropower plants ensure a minimum flow downstream called the reserved flow (or residual discharge) that guarantees fish life. o SHP schemes assist in maintaining river basins by allowing the recovery of wastes that flow in the river stream. Economy: o Current SHP technology assists in refurbishing old SHP plants. o SHP mobilizes financial resources and contributes to the economic development of small scattered populations, ensuring autonomous and reliable energy for the long term. o SHP plants create local jobs for the monitoring of the running phase of the plant. o SHP plants assure a high energy payback ratio. For each power generation system, the “energy payback” is the ratio of energy produced during its normal life span, divided by the energy required to build, maintain and feed the generation equipment. If a system has a low payback ratio, it means that much energy is required. Electricity supply: o Building SHP plants helps create a more diversified electricity system. o Since SHP is located close to the consumers, transmission losses can be reduced and the electricity supply lines are eased. Logistic: o SHP schemes assist in monitoring hydrological indicators.
1.5 How old is the SHP experience? SHP history is characterised by two main periods, based on the use of water energy: first period: when hydraulic energy is meant only to generate mechanical energy second period: when hydraulic energy is meant to generate electrical energy The first hydraulic machines appeared about 2'200 years ago probably almost at the same time in China as in the Mediterranean basin. In Europe, before the general electric-networks extension, about ten thousands of small hydraulic installations existed and were used in sawmills, tanneries, pulp and paper mills, mechanical shops, etc. And then due to the electricity development, hydraulic turbines had to be adapted to this new energy use. What can be emphasized is that current turbines have nothing to do with the old water wheels and have been much improved so as to reach:
high performances for the efficiency (level and area of the operating range) and for the cavitation,
simplified geometry,
technical solutions assuring a high reliability.
1.6 Is there a renewed interest for SHP? Whereas the number of SHP plants has decreased much since the middle of the 20th century, nowadays an important renewed interest can be observed. Several reasons could explain such a renewal, such as the SHP advantages as developed in the question 1.4 and also: • The oil crisis and the strong increase of the price of crude oil during the seventies ; • The possibility to realise technically forward, more reliable and efficient installations with a simple maintenance ; TN_FAQ_En
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•
The people's growing ecological sensibility, more and more favourable to renewable energies, as well as the corresponding authority's incentives. Legal disposition forces the electric utilities to buy the energy produced from renewable energy, even if this production is not steady. Moreover, for SHP the taking back price is guaranteed so as to encourage their development in each European country.
1.7 What kind of potentials exists for the SHP plants? Interesting potentials for SHP can be divided into two categories: 1. rehabilitation, 2. new constructions, such as: 2.1. usual construction on water streams 2.2. use of water networks: • irrigation • drinking water • wastewater network: The development of the use of water networks is strongly recommended, as up to now only a few sites have been equipped. The main advantages compared to the other types of potentials are: less administrative constraints often lower costs valorisation of energy that is currently lost. 1.7.1 How could drinking water be an interesting potential for SHP? In mountain regions, usually a strong slope exists between the water catchments and the consumers. It results in a pressure so important for the distribution network that it has to be wasted in a surge tank. Instead of using pressure reducer device, it is often technically and financially possible to use this pressure in small Pelton turbines. Therefore water is optimally used, as it generates energy before being consumed. Furthermore no environmental impact is created, since the water catchments, basins and pipes have in any case to be made so as to satisfy the people's water needs. On top of that, no other special water right is needed, which allows a quick carrying out of the projects. 1.7.2 Is water still drinkable after being turbined? If we consider a turbine set on a drinking-water network, we may wonder on the hygiene of such a process. What should be pointed out is the difference between a usual drinking-water network and a turbined drinking-water one. • Concerning the equipments: a turbined drinking-water network is composed of the same equipments as a usual drinking water one, and a few more: a turbine, a discharge regulation device and an automatic bypass, • concerning the entities that come into contact with drinking water: the same material is used: essentially stainless steel, moreover no oil could come into contact with water. Furthermore so as to guarantee a minimum of head losses in the pipes, the pipes walls have to be prevented from any deposit. On top of that, the turbining does not raise the water temperature as the recovered energy is transformed in kinetic energy, then in mechanical energy and finally in electricity. Besides water turbining increases water oxygenation. TN_FAQ_En
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To conclude a turbined drinking-water network does not imply more sanitary risks than a usual drinking-water one. 1.7.3 How could wastewater be an interesting potential for SHP? Two possibilities to turbine wastewater exist: 1. the turbine can be set before the wastewater treatment plant. In this case, the wastewater network of an agglomeration situated at altitude is linked to a screening chamber and a surge tank. The wastewater is then led through a penstock to the wastewater treatment plant situated in the valley where it is turbined before being treated. 2. the turbine can be set after the wastewater treatment plant. In this case, the wastewater treatment plant is situated at altitude, and the treated water goes through the valley in a penstock to the turbine installation, before being discharged in a lake or in a river. Furthermore what can be underlined is the problem of the deposit on the penstock walls, which increases head losses: another reason to guarantee an optimal dimensioning. For more details, see paragraph § 1.3 of the "Guide on how to develop a small hydro site"viii. 1.8
Any concrete examples of a good integration of SHP plants? SHP plant at Farebout, France: the use of aspiration turbines and the injection of air at the turbine implies an oxygenation of the river water, which results in improving the water quality downstream from the SHP. SHP plant at Steinen, Germany: the erection of a hydroelectric facility below the flow of the water in a totally submerged powerhouse inside a residential area has the benefit of ensuring an optimal, economical and non-polluting production of electricity. SHP plants on the Louros River, Greece: biotopes have been created thanks to the combination of architectural and technical solutions. Fish passes are getting commonly used in most of the EU countries. The impacts on fish migration can be minimised by using fish passes to allow the upward migration of fish -these should be installed on rivers with migratory species – and by installing grids or other diversion methods across water intakes and tailraces to prevent the entry of fish into the turbine.
1.9 What is the current SHP position in Europe? Hydropower now accounts for about 84 % of the electricity generation from renewable sources in Europe (EU-25) and for 13 % of total electricity production in the EU-151. In 2001, in EU-15, SHP contributed about: • 2 % to the total electricity generation • 9 % of the RES (Renewable Energy Source) electricity generation • 4 % of the RES primary energy. This contribution was similar to wind and lower than biomass At present, almost in all countries hydropower is a dominant source of energy in RES electricity production. SHP accounts for approximately 4.6 % of total hydro generation in the
1
EU-15: Portugal, Sweden, Germany, France, Italy, Luxembourg, Greece, Spain, Finland, Belgium, the Netherlands, Denmark, Austria, Ireland, UK
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new EU Member States (EU-10new2) and in the Candidate Countries (CC3). None of the other renewable energy sources (wind, biomass, photovoltaic, etc) is able to compete with small hydropower in these countries. In EU-25 about 16'800 SHP plants are in operation with a total installed capacity of 11 GW, while the total production is about 41 TWh per yeari. 12000
Installed Capacity MW
10000
9909
8000 6000 4000 2000 822
608
EU-10
CC
969
777
NO
CH
0 EU-15
Electricity Generation, GWh/year
SHP installed capacity (MW) in EU-25, in the candidate countries (CC) and for Norway (NO) & Switzerland (CH) (official limit for SHP: 10 MW)i
45000 40000
39397
35000 30000 25000 20000 15000 10000
2329
1407
4415
3372
EU-10
CC
NO
CH
5000 0 EU-15
SHP electricity generation (GWh/year) in EU-25, in the candidate countries (CC) and for Norway (NO) & Switzerland (CH) (official limit for SHP: 10 MW)i 2
EU-10new: On 1 May 2004 eight Eastern European and two Mediterranean countries, the Czech Republic, Cyprus, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, Slovenia joined the EU 3 CC: Bulgaria, Romania and Turkey are Candidate countries
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According to Eurostat figures for 2002, Italy accounted for about 21% of the total SHP installed capacity in the EU-25, followed by France (17%) and Spain (16%). Poland and the Czech Republic both with 2% of the total EU-25 SHP capacity are the lions of the New EU Member States. From the Candidate countries, Rumania and Turkey represent about 25 % and 15 % respectively of the total SHP installed capacity in 2002 in EU-10 + CC. Other figures for SHP: • 5-15 Eurocents/kWh: European average SHP electricity production costs • € 1 200 -3 500/ kW: European average SHP investment costs • 6'000 SHP jobs (direct and indirect jobs) in 2002. 1.10 What are the main barriers against the development of SHP in Europe? At present, numerous institutional barriers still stand in the way of SHP development, such as: • difficulties to obtain permission to abstract water from rivers ; • perceptions that a hydro plant might adversely affect fishing ; • difficulties in gaining affordable connections to the grid (although this situation is tending to improve). At the same time the pressure of a few environmental groups, which are opposed to SHP for its local environmental impacts on the river ecosystem, hinders progress in many developed countries. However, new technology and improved methods of operating SHP are steadily reducing the local environmental impacts by integrating environmental issues and local population in the planning, design and management process. For more details, see paragraph § A.3 of the "Guide on how to develop a small hydro site"viii.
1.11 Is SHP interesting for developing countries? 1.11.1 Is SHP interesting for developing countries with respect to geopolitics, ethics and environment? So as to know if a SHP turbine is an interesting energy supply for developing countries, the following characteristics ought to be considered: • The energy resource is an indigenous one and does not need to be bought: the energy dependence is reduced. • According to the water potentials which can be geographically wide-spread, small power plants can be decentralised and assure the energy needs of isolated villages. • SHP rarely needs the construction of a large dam. • Thanks to their small size, it permits local people's involvement from the implementation to operation, maintenance and management. • A small hydropower plants do not generate atmospheric emissions, or solid wastes or liquid ones. • As far as the small power plant implementation and operations respect the state of the art in terms of reduction of the environment impacts, the environment should be preserved. • The electrification can become possible, where a supply network would have required much more time and money.
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1.11.2 Is SHP financially affordable for developing countries? To know if SHP is financially affordable for developing countries, the following characteristics ought to be considered: • the resource is an indigenous one • the decentralisation characteristic implies low distribution costs • thanks to their small size, civil engineering cost can be reduced • SHP plants have a long life (> 25 years) compared, for instance, to fuel engines Note: financing from international funds can be claimed for large development projects. 1.12 What is the remaining potential for SHP? 1.12.1 In Europe? SHP has a huge and still untapped potential, which will allow EU SHP industry to increase its activities by developing new SHP plants and refurbishing old ones. Indeed, the best home market for EU manufactures is the refurbishing of existing plants. Moreover, outside Europe there are new opportunities for export and technology transfer that offer good prospects for EU manufactures. And what can be added is that an economic growth and an increase of energy needs will govern hydropower progression. Currently, the remaining economically feasible potential amounts: • to some 20 TWh/year in EU-15ii • to some 26 TWh/year in the New Members States and CC, which majority (roughly 80% or 19'300 GWh/year) is located in Turkey, while Poland and Romania rank second, having indicated potential 6 to 10 times lower than that of Turkey (the third group is composed by the Czech Republic, Slovenia, Bulgaria and Slovakiaii). 22809
Remaining SHP potential GWh/year
25000 20000
19645
15000 10000 2620
4004
5000 0 EU-15
EU-10
CC
CH
Figure 1. Remaining SHP potential in EU-25, in the candidate countries (CC) and in Switzerland (CH) (official limit for SHP: 10 MW)
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1.12.2 In the world? The following figure shows potentials for the whole hydropower area (small and large hydropower). Asia (especially China and India) is set to become a hydro leader. Concerning SHP, the remaining potential could be estimated at about 300 TWh/year.
Total hydropower potential by continent (for small and large hydropower)
1.13 What are SHP objectives in Europe? • 33%: Renewable Energy Industry EU-15 target for the contribution of renewable energy to electricity production by 2010. • 22%: EU-15 renewable electricity target set up by the European RES-e Directive by 2010. For SHP this target means to reach by 2010: 14 GW of installed capacity, generating 55 TWh of electricity 1.14 How to develop a small hydropower project? Once the site is located, the first basis of a small hydropower project are the knowledge of the available difference of levels (since the turbine has to be set the lowest as possible from the upstream water level) and discharges (minimal, mean, maximal, annual averages, daily averages, on one year, on ten years) - the more available details, the more adapted the turbine will be to the site. These first data will enable to calculate the hydraulic power, the first turbines characteristics, and to do a first economic calculation so as to have an idea on the cost efficiency of the project. A checklist, that gathers all the steps to build a hydropower project, was created by the Thematic Network on Small hydropower, and is available on the web.iii.
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Note: generally, on an administrative and political point of view, it would be easier to build a SHP scheme on an existing water network (drinking water, wastewater, ‌) than on a river.
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2
ENVIRONMENT
For more details, see chapter § 7 of the "Guide on how to develop a small hydro site"viii, the brochure on environmental aspectsix and some other ESHA publicationsiv, v 2.1 Can SHP be considered as a clean energy? Regarding the fact that the production of hydroelectricity does not emit polluting substances, electricity from a SHP plant could be considered as clean. What can be added is that a special care has to be taken to limit the local environmental impacts (ecosystem of the water stream) of the turbine setting and operations. Moreover laws such as environment, energy, water protection, soil, fishing ones guarantee that ecology is respected. 2.2 How can the local environmental impact of a SHP plant be reduced? So as to limit the environmental impact of a SHP plant, construction and operating methods as detailed in the following examples ought to be applied: • Creation of dam-crossing systems for fish and invertebrates • Respect of a fixed residual discharge (or reserved flow) in the bypassed section. • Fittings of the bypassed section so as to assure a satisfactory flow speed. • Dam emptying avoided during low-water period. • Creation of life spaces in the tanks and basins. 2.3 How much does a hydro-electric GWh reduce the CO2 emissions? 1 GWh (corresponding, for instance, to the mean electrical consumption of 220 Swiss households) of European mix electricity replaced by 1 GWh from a hydraulic source results in reducing the CO2 emissions of 481 tonnes. 2.4 What happens to the water that is used for power production? When it gets out of the turbine, the water that has been tapped from the river returns to the river downstream from the tap. For the protection of the ecosystem, just a part of the river flow can be tapped, so as to maintain a correct water level in the river for flora and fauna and flora and especially for fish. This flow or discharge that can not be used for power production is called the residual discharge or the reserved flow. On top of that, it can be emphasized that the water that flows out of the turbine is not dirtier than when it has flowed in. Thanks to that fact, it is possible and often really interesting on an ecological and economic point of view to turbine drinking water, since the water is still drinkable when it flows out of the turbine. See 1.7.2 Is water still drinkable after being turbined? 2.5 What happens to fish when a SHP plant is set on a water stream? Special equipments are set with the SHP plant to protect fish, such as: • grids at the entry of the water tapping to prevent fish from going into the penstock, • fish by-pass systems
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Moreover, what should be noticed is that not all the water of the river goes into the turbine, water remains in the river, which discharge is regulated by laws. The minimum water discharge that has to remain in the river bed and can not be turbined is called the residual discharge or the reserved flow. 2.6 What is the residual discharge or reserved flow? The residual discharge, or also called reserved flow, is the discharge of the water stream that remains in the water-stream bed after the water tap for the turbine and before the turbinedwater return. Indeed water is tapped from the water stream, led to the turbine and turbined before returning to the water-stream bed, but downstream from the tap. A residual discharge is meant to: • assure fish survival, • feed underground waters, • favour species diversity, • valorise landscape, • create alluvial spaces, • assure cleanliness of water streams. 2.6.1 How can the reserved flow be estimated? There are many formulas, which can be divided into different groups: • The most famous group estimates the values based on hydrological data. The approximation of a reserved flow equalled to 5-10% of the mean flow is widely spread • Another well-known approximation is based on the width of the river bed and proposes a residual discharge of 30-40 L/s per meter. • Another approach uses the size of the catchment and gives a first estimation of the residual discharge of 2-3 L/s per km². The final value should be found by means of insitu tests and measurements of various parameters such as depth and flow velocity. 2.6.2 What is the cost of providing a reserved flow? The cost of providing a reserved flow can be estimated with the following formula: C = 0.001. η .ρ .Qr .g. ∆Z. T. t C = annual cost [€/year] η = global power plant efficiency [-] ρ = water density ≅1000 [kg/m3] [m³/s] Qr = residual discharge or reserved flow g = gravity ≅ 9.8 [m/s2] ∆Z = difference of level between the upstream level at the water [m] withdrawal and the downstream level T = tariff [€/kWh] t = full-load hours per year [hours/year] usually: t = 5'000 [hours/year] The formula can be reduced to: C = 40'000 .Qr .H .T See also the formula to estimate the electrical energy and power - questions 3.4 and 3.7
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For more details, see paragraph § 7.4.3.2 of the "Guide on how to develop a small hydro site"viii, and some other ESHA publicationsvi, vii
2.7 What is a fish by-pass system? A fish by-pass system is a technical construction aiming at mitigating the interruption of the river continuity. It connects the upstream area to the downstream one. What can be pointed out is that the operations need a certain amount of water. 2.7.1 What are the different types of fish bypass systems? There is a wide range of fish bypass systems between rather technical constructions and very natural solutions. The most used technical system is the “vertical slot pass. The “natural-like creek” without any steps is representative of the natural solutions. Nevertheless what should be noted is that the choice of a fish by-pass system for a site has to consider the type of the river, the space available, the fish concerned and the migration direction.
Vertical slot passviii
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Environment friendly and efficient natural-like fish by-passix
2.7.2 What do fish bypass systems consist in? A fish bypass system for the upstream migration lets the head at the weir passable for fish and ensures the river continuity as a fauna habitat. Using the bypass system, fish can migrate between top-water and tail-water of the weir. 2.7.3 How much water is used to run a fish bypass system? The amount of water depends on the system size and type, that itself depends on the water stream. The bigger the system, the bigger amount of water is necessary. A rough estimation gives values between 1% and 5% of mean flow depending on the size of the mean flow of the water stream. The final decision ought to be taken by in-situ tests after the system erection by measuring flow velocities, turbulences, aeration etc. 2.7.4 What is the cost of building and operating a fish bypass system? In relation to the total cost of the SHP, the cost for the fish bypass system may vary between 1% and 10%. The more technical the systems, the more expensive they are. The simple nature-like creeks are usually rather cheap. Consequently it is recommended to mandate an experienced professional for the design work. For more details, see paragraphs ยง 7.4.3.2.6 & ยง 7.4.3.2.7 of the "Guide on how to develop a small hydro site"viii.
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3
TECHNIQUES
3.1 How do SHP plants produce electricity? The basic principle of hydropower is to transform water energy in mechanical energy through a turbine and afterwards in electricity through a generator. Water can be piped from a certain level to a lower level. A head is thus necessary so that water, diverted through an intake channel or a pipe (or a penstock) into a turbine, is discharged back downstream into the river. If the water pressure has the possibility to move a mechanical component then that movement involves the conversion of the water energy into mechanical energy. Hydro turbines convert water pressure and velocity into mechanical power, which can be used to drive an electricity generator. How to estimate the generated electric energy is explained in the question: 3.4. 3.2 What is the difference between gross head and net head? Usually the gross head is equivalent to the difference between the water intake (upstream level) and the lower water level (downstream level) (∆Z), whereas the net head (Hn) is related to the discharge and is defined as the specific hydraulic energy, gH, divided by the gravity g. This net head can take into account head losses in the penstock. And when "head" is used without any adjective, it could often stand for 'gross head'. 3.2.1 How can the gross head be measured? The gross head can be measured using: • a level • a clinometer • a pressure gage • an altimeter For more details, see paragraph § 3.4.5 of the "Guide on how to develop a small hydro site"viii. 3.3 How high can the SHP-plant energy efficiency be? The efficiency of a small turbine (the ratio of electricity and hydraulic energy) can reach 90 % or more as far as it comes from laboratory development. Each power plant operator should ask the manufacturer for an efficiency guarantee based on laboratory developments. It is the only way to be sure that the turbine will operate properly. The origin of the guarantees ought to be known, even for small hydro turbines. 3.4 How can the generated electric energy be estimated? The generated electric energy can be estimated with the following equation: E= η ·ρV·g·∆Z E= electric energy yearly generated by the installation ρ = water density ≅ 1000 TN_FAQ_En
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[J/year] [kg/m3] 04.08.2005
V= yearly mean volume of turbined water according to the flow duration curve,
[m3/year]
g = gravity ≅ 9.8 [m/s2] ∆Z = difference of level between the upstream level at the water [m] withdrawal and the downstream level η = global efficiency, product of the mean efficiencies of the penstock ηp, of the turbine ηT, of the possible speed increaser ηM, of the electric generator ηG and of the possible transformer ηTr η = ηp⋅ηT⋅ηM⋅ηG⋅ηTr
[-]
Note: the penstock efficiency is directly linked to head losses. For more details, see paragraph § 3.6 of the "Guide on how to develop a small hydro site"viii.
3.5 What is the difference between efficiency and power? The global efficiency of a scheme is the ratio of the generated electricity by the hydraulic energy of the site, which is also the ratio of the electric power by the hydropower of the site. This efficiency has no units, and is often expressed in percent (%). It is also the product of the mean efficiencies of the penstock ηp, of the turbine ηT, of the possible speed increaser ηM, of the electric generator ηG and of the possible transformer ηTr (see 3.4 question). The power of a scheme is the product of the global efficiency by the hydropower available for the turbine. It is expressed in kW. Efficiency and power are essential to the development of a small hydro project. The electric power will enable to estimate, thanks also to the annual operation hours, the quantity of annually-generated electricity. And the efficiency shows the quantity of hydraulic energy that is lost through such a scheme. 3.6 What is the average power of a small turbine? This question has no right answer as a small-turbine power can vary from a few kW to 10 MW (which is the official definition of the threshold between small and big hydropower). But if the small turbines set in 2002 in the European Union (EU-25) are considered, that represents circa11 GW for 16'800 power plants, the average power of a SHP plant is 650 kW. 3.7 How can the hydraulic power be estimated? The hydraulic power can be estimated with: Ph = ρQ gH P = hydraulic power available for the turbine ρ = water density ≅1000 Q = discharge gH = specific hydraulic energy of the machine g = gravity ≅ 9.8 H = net head
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[W] [kg/m3] [m3/s] [J/kg] [m/s2] [m]
04.08.2005
3.8 Could SHP plants produce peak hours electricity? Generally small hydraulic power plants have a limited storage capacity, which means they are, most of the time, run-of-river power plants and can not be used for peak hours production. 3.9 What are the mean dimensions of a SHP power plant? This question has no right answer as the turbine dimensions have a large range of variation. 3.10 How can the number of turbines in a power plant be chosen? The number of turbines to be set on a site depends on the duration curve of the water stream (see question 3.17), or on the discharge variability and on the turbine flexibility (its efficiency evolution when the discharge moves away from the design discharge).
3.11 Are there different kinds of small turbines? Three main kinds of small turbines exist (the same as for the big hydropower ones): 1. Pelton turbines: with a runner composed of buckets, they fit especially to high-head applications (from 60 m to more than 1'000 m). 2. Axial turbines: with a runner composed of blades, they gather Kaplan, bulbs and propellers ones, and are suited for low head between 2 and 40 meters. 3. Francis turbines: they are suited for heads from 25 to 350 meters. The following figure shows the operating areas of the turbines regarding their discharge and head.
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Areas of turbine applications regarding the head (H, meters) and the discharge (Q, m3/s)
3.11.1 What are their main specific characteristics? 3.11.1.1 What are the main characteristics of a Pelton turbine? A Pelton turbine, as shown in the following figure, is an action turbine, which means the energy available for the runner is kinetic (water speed). A small Pelton turbine will reach a mechanical efficiency at the coupling of 90 % (as far as its development is based on laboratory works). The buckets runner is driven by one or more free-water jets that come from the nozzles and exert a force on the profiled buckets. Thanks to these different nozzles, a Pelton turbine can assure a good efficiency for a wide range of discharge. Moreover, the runner is under water and the machine inside is at the atmospheric pressure, or even at a light depression.
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View of a two-nozzle Pelton turbine
For more details, see paragraph ยง 6.2.1 of the Guide on how to develop a small hydro siteviii. 3.11.1.2 What are the main characteristics of an axial turbine (as the Kaplan one)? Axial turbines, as shown in the following figure, are all reaction turbines, and can be seen in constructional works with high discharges and low heads (from 2 to 40 m). Their mechanical efficiency level is about 92% for SHP (as far as their development is based on laboratory works). The propeller configurations are seldom in SHP, as it needs a quasi constant flow. On the other hand, many installations with movable blades and fixed guide vane system (simple adjustment) or with movable blades and guide vane system (double adjustment) exist. In both cases, these machines accept a wide range of flow variations.
Cross section of a double-regulated Kaplan turbine
For more details, see paragraph ยง 6.2.1 of the Guide on how to develop a small hydro siteviii.
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3.11.1.3 What are the main characteristics of a Francis turbine? As the Kaplan one, a Francis turbine, as shown in the following figure, is a reaction machine. Its runner is under water and exploits the water speed (kinetic energy) and the pressure difference. This kind of turbine can be seen regularly in old low-head installations where they are often composed of a water chamber, which is without any spiral case. Since their rotation speeds are very low, and as they do not adapt themselves properly to the flow variations, they have been replaced by small Kaplan turbines that appeared on the market in the thirtiesforties. The operation field of Francis turbine currently ranges between 25 to 350 metres. The mechanical efficiency of small Francis turbines from laboratory developments is about 92 %.
View of a Francis turbine
For more details, see paragraph ยง 6.2.1 of the Guide on how to develop a small hydro siteviii.
3.12 What is a guide vane system? Reaction turbines are equipped with a guide vane system, set just before the runner. It is composed of blades or guide vanes that can be moveable or not, and it is made so as to control the flowing angle at the runner inlet. 3.13 What is the difference between an action (or impulse) turbine and a reaction one? For an action (or impulse) turbine, the water pressure is only converted into kinetic energy. The most usual impulse turbine is the Pelton one. On the other side, a reaction turbine uses water speed (kinetic energy) and the difference of pressure.The most usual reaction turbines are the axial and the Francis ones. 3.14 What is the best material for a runner? The best material for a runner is stainless steel.
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3.15 What is systemisation? The systemisation process is meant to parameter completely the turbine hydraulic profile, then to test its behaviour and its performances, depending on the parameters evolution. Since this process is consolidated by laboratory tests, similitude laws allow then to calculate each new turbine depending on the exact characteristics of the site to be equipped and especially to guarantee the performances. Therefore tests on turbines are achieved in the upstream process, and not once the turbines are built, which reduces the costs for the investor. 3.16 What is the specific hydraulic energy of the machine? The specific hydraulic energy can be estimated with: E = gH = 1 ⋅ (p1 −p2 ) + 1 ⋅ (c12 −c22 ) + g ⋅ (z1−z 2 ) ρ 2 Where : gH = specific hydraulic energy of the machine g = gravity ≅ 9.8 H = net head ρ = water density ≅ 1000 px = pressure in section x cx = water velocity in section x zx = elevation of section x
[J/kg] [m/s2] [m.] [kg/m3] [Pa] [m/s] [m]
3.17 What is a flow duration curve? A flow duration curve is a curve that represents mean daily discharges classified in a decreasing order. This curve shows the number of days for which a considered discharge is reached during one year.
12.000
10.000
Flow rate m3/s
8.000
6.000
4.000
2.000
0.000 0
50
100
150
200
250
300
350
days/year
Example of a flow duration curve
For more details, see paragraph § 3.4.2 of the Guide on how to develop a small hydro siteviii. TN_FAQ_En
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3.18 How can the discharge be measured? Several methods exist so as to measure the discharge: • the bucket method • the velocity-area method • the weir method • the salt-dilution method • the slope-area method • the stage-discharge method For more details, see paragraph § 3.3 of the Guide on how to develop a small hydro siteviii. 3.19 What are head losses? Head losses are energy (pressure) losses that come from the changes of the flow directions, the frictions on the pipes walls, the obstacles (such as the grids), etc. 3.19.1 How does the penstock act on head losses? The penstock acts on the energy assessment of the installation. Indeed if an increase of 20% of the diameter is considered, head losses decrease by 60%. Moreover deposit on the penstock walls results in increasing head losses, which is an essential problem for turbines set on wastewater. For more details, see paragraphs § 2.2 & § 5.5.3 of the Guide on how to develop a small hydro siteviii. 3.20 What is cavitation? When the hydrodynamic pressure in a liquid stream falls below its vapour pressure, vapour is created that implies small bubbles. This bubbles formation can generate a cavitation phenomenon, with high impulse pressures and a substantial noise (to give a picture: the cavitation phenomenon sounds like gravels passing through the turbine). The repetitive actions of such bubbles close for instance to the runner blades result in eroding them. And finally in a short time the turbine can be seriously damaged. Next photo shows a blade achieved without any laboratory developments that has been damaged through cavitation after a few months of operation and had to be replaced.
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Blade damaged through cavitation
3.20.1 How can the cavitation phenomenon be avoided? The cavitation phenomenon can be avoided with an optimal turbine dimensioning and design, and by fixing the turbine operating area. Laboratory developments allow to understand the cavitation behaviour of a blade, to define this operating area, and to set a maximal level for the runner setting. In front of such phenomenon, in addition to efficiency guarantees, a SHP investor should ask for guarantees on an operation without any cavitation damages. For more details, see paragraph ยง 6.2.4 of the Guide on how to develop a small hydro siteviii.
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4
POLITICAL ASPECTS
For more details, see chapter § 9 and annex § A of the Guide on how to develop a small hydro siteviii. 4.1 What is the objective of the White Paper concerning SHP? In 1997, 5.4% of the European gross electricity consumption was renewable energy, in 2001 6%. The European objective is to reach 12% in 2010. That target concerns also SHP: 4'500 MW should be created, which means the annual production ought to grow from 37 TWh to 55 TWh. Also see the question: 1.9 What is the current SHP position in Europe? For more details, see paragraph § A.1 of the Guide on how to develop a small hydro siteviii. 4.2
What is the objective of the Directive 2001/77/EC, “Promotion of Electricity Produced from Renewable Energy Sources” (RES-e Directive)? The Directive sets up specific goals to reach 12 % use of electricity from renewable in the EU by the year 2010. The RES-e4 Directive gives Member States a reason to be interested in SHP since it is the best proven renewable-energy technology. The Directive proposes the following measures: Quantified national targets for consumption of electricity from renewable sources of energy National support schemes and, if necessary, a harmonised support system Simplification of national administrative procedures for authorisation Guaranteed access to transmission and distribution of electricity from renewable energy sources
4.3 How is the European SHP sector interconnected? The European SHP sector is interconnected through two ways: ¾ a biennial conference ¾ an European association, called ESHA for European Small Hydropower Association The Hidronergia international conference organized every 2 years brings together specialists and stakeholders in the SHP field from all over Europe. It provides excellent opportunities for main stakeholder across Europe, who can find there a meeting point to know each other, to exchange information, define common strategies, and promote new actions and initiatives. This conference covers the main technological, administrative, environmental and political issues of the SHP sector. At a European level ESHA represents the interests of the SHP sector regrouping national associations of SHP producers, which themselves gather operators, industries, project developers, consultants, utilities, research institutions. ESHA is a well-established organization that has set up a SHP network throughout Europe with continuous communication with politicians and decision-makers.
4
RES-e: electricity from Renewable Energy Sources
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4.4
What are the main support policy instruments for renewable energies in general and SHP in particular? There are basically three main instruments to promote renewable electricity, which are:: ¾ feed-in tariffs ¾ quota obligations in combination with a green certificate system ¾ tendering / bidding schemes These policy instruments are all based on two main principles. They affect the supply or the demand of renewable electricity, and they focus either on the production of electricity or on the installed capacity of renewable electricity plants. a. feed-in tariffs Operating currently in several EU Member States, (notably Germany and Spain), they are characterised by a specific price being set for RES-e that must be paid by electricity companies, usually distributors, to domestic producers of RES-e. In a variant of the system the government sets a fixed-premium paid above the normal or spot electricity price, to RES-e generators. The fixed price or fixed premium may be revised by the government to reflect falling costs of the technology. b. quota obligations systems and green certificates Quota obligations are used to impose a minimum production or consumption of electricity from RES. The government sets the framework within which the market has to produce, sell or distribute a certain amount of energy from renewable sources. The obligation is imposed on consumption or production. The quota can usually be traded between companies to avoid market distortions. A Tradable Green Certificate (TGC) is needed for this system. Operating notably in Ireland and The Netherlands, and foreseen for introduction in Denmark and Flanders, the producers sell electricity in the open market, but at the same time receive a “Green Certificate” per MWh produced, which is traded separately from the physical commodity. The value of the TGC comes as the result of the obligation, placed on all consumers to purchase a certain amount of green certificates from RES-e producers according to a fixed percentage, or quota, of their total electricity consumption/production. Since consumers wish to buy these certificates as cheaply as possible, a secondary market of certificates develops where RES producers compete with one-another for the sale of the green certificates. c. tendering / bidding schemes Historically operating in the United Kingdom under the NFFO agreements but no longer in place, prospective RES-e generators submit competitive bids for fixed-price contracts offered by authorities. The system is combined either with feed-in tariffs or TGCs. In UK, where this system operated with some technologies, the TGCs are known as ROCs (Renewable Obligation Certificates). Bidding procedures can be used to select beneficiaries for investment support or production support or for other limited rights. Potential investors or producers have to compete through a competitive bidding system. The criteria for the evaluation of the bids are set before each bidding round. The government decides on the desired level of electricity from each of the RES, their growth rate over time and the level of long-term price security offered to producers over time. The bidding is accompanied by an obligation on the part of electricity providers to purchase a certain amount of electricity from renewable sources at a premium price. The difference between the premium and market price is reimbursed to the electricity consumption. In each bidding round the most cost-effective offers will be selected to receive the subsidy. The mechanism therefore leads to the lowest cost option. TN_FAQ_En
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For more details, see the annex A of the "Guide on how to develop a small hydro site"viii.
4.5
What are the complementary support policy instruments for renewable energies in general and SHP in particular? Besides the three main instruments (see question 4.4 What are the main support policy instruments for renewable energies in general and SHP in particular?), there are complementary mechanisms, like investment subsidies and fiscal measures. ¾ Investment subsidies: Authorities offer subsidies on investment for RES-e technologies, in general in terms of % of the Total Investment. This type of support can help to overcome the barrier of a high initial investment and it is commonly used to stimulate investments in less economical renewable energy technologies. ¾ fiscal measures: Some MS like Austria, Belgium, Denmark or Portugal support renewable electricity by means of fiscal system. These schemes may take different forms, which range from rebates on general energy taxes, rebates from special emission taxes, proposals for lower VAT rates, tax exemption for green funds to fiscal attractive depreciation schemes, which must be in line with the Community guidelines on State aid for environmental protection. 4.6 Where to get hydrological data? Hydrological data can be obtained at governmental bodies that collect and pre-process measurement data from official gauging stations. Usually they are called “hydrological department”. There you will get primary information. Then a more detailed analysis should be done by the civil engineer running the design process.
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5
ECONOMIC ASPECTS
For more details, see chapter § 8 of the Guide on how to develop a small hydro siteviii. 5.1 How much money can be earned with a SHP? The money to be earned with a SHP is related to the amount of kWh produced and the price, for which each kWh is sold (either defined as a fixed tariff or as a green certificate). Depending on the annual hydrological characteristic the production may vary between 75% and 125% of the mean annual value. A first approximation of the annual production (in kWh/year) can be found as the product of the rated power (in kW) x 4000. 5.2 How much does a SHP project cost? An investment in a SHP scheme entails a certain number of expenses, extended over the project lifetime, and produces at the same time revenues also distributed over the same period. The expenses include a fixed component - the capital cost, insurance, taxes, etc- and a variable component -operation and maintenance costs-. 2.0 1.8 1.6
cost â‚Ź/kWh*a
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
1'000'000
2'000'000
3'000'000
4'000'000
5'000'000
6'000'000
7'000'000
8'000'000
9'000'000
10'000'000
Production kWh/a
Cost curve: investment cost in euros/(kWh/year) vs annual electrical production in kWh/year (Source: Thematic Network on Small Hydropower, ESHA, 2005)x
The graph shows the investment cost expressed in euros per kWh/year versus the annual electrical production in kWh/year, between 500 MWh/year and 10 GWh/year. Assuming the typical 5'000 hours per year of full load for a SHP site, this range equals an installed capacity from 100 kW to 2 MW. For example, considering 5'000 hours of full load per year, the investment cost for a 100 kW SHP ranges from 0.95 to 1.80 euros per kWh/year or from 475'000 and 900'000 euros, whereas for a 2 MW SHP it ranges between 0.55 and 0.75 euros per kWh/year, or between 5.5 and 7.5 millions of euros.
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Of course, this cost curve gives a rough idea of the investment cost for a SHP. Only a feasibility study achieved by SHP specialists can precise the real costs of a project. 5.3 How long is an acceptable payback time? So as to know if the payback time is acceptable, the turbine life has to be considered. Indeed the life of a SHP turbine is usually higher than 30 years. For more details, see paragraph § 8.4 of the Guide on how to develop a small hydro siteviii.
5.4 How many SHP manufactures are in Europe? There are 23 substantial hydro manufactures active in small hydro in the European Union. Four major multinational companies dominate the market for larger turbines, but the market between 0.5-5 MW/site is more open to smaller companies. 5.5 What are the present employment figures and future perspectives? Latest employment figures show that in 2002 about 2'200 people were working directly in the small hydropower sector in the EU. This includes manufactures (around 1'200 employees) plus research and consultancy sector (around 1'000 employees). In addition, there are about 4'000 people indirectly involved, including electricity producers. It can therefore be estimated that about 6'000 employees are working – directly and indirectly – in the European SHP sector. Future expansion of employment in the small hydropower sector depends on overcoming legal, administrative and environmental constraints on development.
6
Glossary
ESHA: European Small Hydropower Association EU: European Union RES-e: electricity from Renewable Energy Source RES: Renewable Energy Source ROCS: Renewable Obligation Certificates SHP: Small Hydro Power TGC: Tradable Green Certificate
7 i
Bibliography
Small hydropower in New Member States and candidate countries, TNSHP, 2004 Small hydropower in New Member States and candidate countries, TNSHP, 2004
ii
iii
Check list, Thematic Network on Small Hydropower, ESHA, (www.esha.be), 2005
iv
Reserved Flow - Effects of additional parameters on depleted Stretch, ESHA, (www.esha.be)
v
Reserved Flow - Short critical review of the methods of calculation, ESHA, (www.esha.be)
vi
Reserved Flow - Effects of additional parameters on depleted Stretch, ESHA, (www.esha.be)
vii
Reserved Flow - Short critical review of the methods of calculation, ESHA, (www.esha.be)
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viii
Guide on how to develop a Small Hydro site, Thematic Network on Small Hydropower, ESHA, (www.esha.be), 2005 ix
Brochure on the environmental aspects of small hydroelectric plants, Thematic Network on Small Hydropower, ESHA (www.esha.be), 2005 x Cost Curve, Thematic Network on Small Hydropower, 2005
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