Energy Conservation studies in Hydro- Generating Units and Plant auxiliaries of Hydro Power Plant

www.as‐se.org/ijpres International Journal of Power and Renewable Energy Systems (IJPRES) Volume 2 Issue 2, 2015

Energy Conservation studies in Hydro‐ Generating Units and Plant auxiliaries of Hydro Power Plant Rishabh Agrawal *1, S.C.Kaushik 2, T.S.Bhatti 3 Centre for Energy Studies, Indian Institute of Technology, Delhi, Hauz Khas 110016, India *1

rishabhhvac@gmail.com; 2 kaushik@ces.iitd.ac.in; 3tsb@ces.iitd.ac.in

Abstract This paper presented a novel comprehensive methodology to evaluate the overall performance of hydroelectric generating units (HGU) in a multi‐ generating unit’s hydro power plant. Introduced a unique economic performance evaluation method for HGUs and the corresponding quantitative indices and different criteria for performance monitoring. Several new concepts for evaluating the performance of HGUs, such as ideal performance, reachable performance, operational performance, overall efficiency, guaranteed performance are proposed and identified.

Based on analysis of the energy flow of hydroelectric generating units (HGU) at different loading, a method and related formulas to calculate the energy indices of the unit are presented. The proposed methodology is presented by using a real case study to illustrate the evaluation process of this method. The methodology proposed in this paper paves a new way to evaluate the overall condition and performance of the HGU and provides a new approach to analyze the performance of other similar plants.

Keywords Operational Efficiency; As Run Performance Analysis; Auxiliary Power Consumption (APC) Analysis; Energy Efficiency Assessment; Hydroelectric Generating Units

Introduction Growing economy, expanding energy intensive industries, rising urbanization, increasing population and on top of all, a quest for modernization and improved quality of life have increased the demand of electricity in India [1].

Energy generation is one of the major key factors for economic and social development in all the developed and developing nations of the world. Hydropower is the most widely used renewable energy source worldwide, contributing almost with 18.5% to the fulfillment of the planet electricity generation. Hydroelectric generation is a continuous production process in which hydraulic energy is converted into mechanical energy and finally converted into electric energy. This is a clean, renewable and economic way of energy production. Every single kWh of hydropower makes sense because this means a small reduction of fossil or nuclear fuel burning. The hydraulic energy is a valuable natural resource, and increasing the efficiency of hydropower production is a long term goal in the field of hydropower engineering because it greatly contributes to the economy and environment.

Usually, the rated efficiency of a large generator is above 98%, the efficiency of the water turbine is the key element in the overall efficiency of an hydroelectric generating unit (HGU). A significant performance factor in the power generation from a hydroelectric plant is the efficiency of the units. Each generating unit experiences three types of losses. These losses occur in the turbine, the generator, and the penstock. In the turbine and the generator the losses happen due to mechanical friction and heat dissipation in the process to convert kinetic energy into mechanical energy and mechanical energy into electrical energy, respectively.

This research work presents a methodology to adjust efficiency functions for hydroelectric generating units. It is based on measured data of power, gross head and water discharge. Its objective is to determine the actual performance characteristics of the turbine units.

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The cost per unit (kWh) power generation by using renewable energy technologies varies by technology, country and project based on the renewable energy resource, capital and operating costs, and the efficiency/performance of the technology. In recent years the necessity of carrying out performance testing and evaluation of large scale hydropower (HPP) plants has been felt globally and initiatives have been taken in several countries to address this need.

Literature Review Going through the literature, it is learnt that the large scale Hydro Power Plant has not been investigated to assess the as‐run energy performance of the units at different load conditions (60% MCR, 85% MCR and 100% MCR) and auxiliaries vis‐à‐vis technical specifications/guaranteed performance values, when they are operating separately and in different load combinations from station prospective in multi units plant. It is finding that due to centralized dispatch afore mentioned, each hydro power plant receives an hourly generation target for the day ahead. As a consequence, the generation distribution among the generating units in the cascaded is a local decision, because of unperfected decision generating unit efficiency drop drastically for different load requirement in multi units plant.

It is identified from literature review that the information from the single‐unit performance characteristics alone is not sufficient for achieving effective operations in a multi‐units plant. The number of units in operation depend on the “load schedule “provided by the regional load dispatch centre.In centralized dispatch afore mentioned, each hydro power plant receives an hourly generation target for the day ahead. As a consequence, the generation distribution among the generating units in the cascaded is a local decision because of unpredicted decisions in plant operation the operating efficiency of generating units goes down drastically in multi‐unit s plant. There is need to search for the most economical combination of units,which is related to the efficient use of water and to minimize startups and shutdowns of hydro generating units as well.

Case Study Plant Energy Scenario The case study hydro power plant is located in State Himalchal Pradesh of India, has four Units & its capacity 250 MW each and Unit‐I, Unit‐II, Unit‐III & Unit‐IV commissioned in March 2007, January 2007, October 2006 & July 2006 respectively, is of Turbo atom, Ukraine / Power Machine, Moscow make.

Total auxiliaries (all station auxiliaries & 75% of unit auxiliaries) and colonies power purchased from grid due to own grid connectivity problem / peak load power station.

The analysis of power purchased, power generated vis‐à‐vis power consumption in colony and the auxiliary power consumption indicates the following: 

The energy drawn from grid as percentage of generation is 1.34%.



The Plant auxiliary power consumption is about 0.13% of the total generation.



The colony consumption (inclusive of water supply) as percentage of generation is about 0.78% of generation.



The colony power consumption including the water supply is 58.66% of the purchased power.



The generation plant auxiliary consumption of HPP TEHRI as percentage of purchased power is about 9.45%.

Performance assessment of key plant auxiliaries, based on ‘As‐ run trials’ was conducted during November, 2013,‐ with the objective of energy performance validation against design value, so as to identify under performance, if any, during the as run trials .Findings are envisaged to help in assessing the performance, vis‐à‐vis design/ rated values, factors and parameters affecting performance, key result areas for improvement and attention, leading to reduction in auxiliary energy consumption. The month‐wise trend of % Auxiliary Power Consumption (APC) w.r.t. purchased power for 2012 ‐13 is summarized as under in Fig.1.

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9.69 Avg. value

FIG.1 THE MONTH‐WISE TREND OF % AUXILIARY POWER CONSUMPTION (APC)

Scope of Energy Conservation Study The scope of the proposed ENERGY AUDIT is to assess the as‐run energy performance of the units and auxiliaries vis‐à‐vis technical specifications/guaranteed performance values and to bring out any applicable avenues for energy efficiency improvement and cost reduction with cost benefit analysis and vendor information as called for.To assess as‐run performance of the four HPP units at representative load settings of 60% MCR, 85% MCR, and 100 % MCR on the broad lines of ISO/IEC 60041:1991, through short trials drawing inputs from on‐site instruments (which are requested to be calibrated prior to trials).It may be appreciated that key on site instruments for flow, net head, and power require to be calibrated since portable instruments for such duties are not available indigenously.To assess the as run energy performance of major unit and station auxiliaries which include drives above 25 kW rating, air compressors, ventilation fans, pumps etc based on measurements and trials drawing inputs from portable instruments like load analyzer, anemometer, non contact ultrasonic flow meter of NPC apart from available on site instruments. To study the grid connectivity aspects for improvements possible so that captive consumption is met with least cost combinations given that generation and import costs are not the same.

Performance Assessment of Hydro Power Generating Units Design Details of Units The Tehri Hydro development Corporation Ltd. presently has the Hydro Power Plant (HPP) in operation with a total generating capacity of 1000 MW. The plant consists of four units of 250 MW each. The design details of the each Hydraulic Turbine and Generator are highlighted below table‐1.

TABLE 1 DESIGN DETAILS OF UNITS

Turbine Make

OJSC TURBOATOM, Ukraine(PO 230‐B‐410)

Turbine Type

Vertical Francis

Rated Output

255 MW

Net Head

Rated

188 m

Maximum

230 m

Minimum

122.6 m

Rated Discharge at Rated head

145.1 m3/s

Rotational Speed

Rated

214.28 RPM

Runaway

410 RPM

Hydro Turbine Generator

Power Machine, Moscow CB‐870/300‐28

Hydraulic System

82

Diameter of Penstock

5750 mm

Diameter of butterfly valve

5000 mm

Diameter of Runner

4100 mm

Diameter of Spiral casing

:

4000 mm

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Unit Performance Assessment The no. of units in operation depends on the ‘load schedule’ provided by the Northern Regional Load Dispatch Centre, New Delhi. A typical load schedule is given in Exhibit 2.1. As HPP is a Peaking Power plant, the units are in operation only during peak load periods. The power plant therefore operates for about 10 – 12 hours in a day.

There is no specified sequence of operation of the Units and are operated as per requirement & availability.

National Productivity Council was assigned the task of evaluating the operating performance of each of the Units to establish a Merit order rating for the Units.

Performance Guarantee: As per the contract agreement, the guaranteed performances to be delivered by the Turbine and Generator at the rated conditions are indicated below in table ‐2.

TABLE 2 TURBINE PERFORMANCE AT RATED NET HEAD – 188 M

Sl. No.

Load (%)

Power Output (MW)

Flow (m3/s)

Efficiency (%)

G.V.O (%)

1.

2.

3.

100 85 60

255 216 153

145.1 122.9 91.1

95.3 95.3 91.1

100 82 59

Trial and Observations Trials were carried out to assess the performance of each Unit at different load conditions, when operating individually and at full load, when operating in combination with other Units. The operating parameters were monitored both at UCB & CCS. The parameters monitored are based on signals obtain from sensors which were recently calibrated.

Basis for analysis : The performance analysis of a Turbine is based on two major factors namely, ‘water flow’ and ‘net head’. The generator performance curve is relied up on for the Generator performance at different loads. Flow measurement available at site (UCB) is based on the pressure differential across the spherical valve while the net head available is based on the pressures at the inlet to MIV and in the draft tube (turbine exhaust). The following assumptions were made in evaluating the unit performances.   

Density of water at 800 m and 16 0C = 1000 kg/m3 Pressure drop across MIV = 0.5 m Correction for Net Head at turbine exhaust = (‐) 3 m

(Based on difference in elevation between turbine exhaust and sensor Position in the draft tube). 

Hydraulic Power (MW) = Q x ρ x g x H / 1000

Where, Q = Water flow rate, m3/s ρ = Density of water, kg/m3 g = Acceleration due to gravity (9.81 m/s2) H = Net Head, m Observations: The observations made during the trials, for single Unit operations, are summarized below tables.

1)

Performance at 500 MW:

The performances of hydraulic power generation unit at 500 MW are presented below in table 3, 4 & 5: TABLE 3 UNIT PERFORMANCE AT 60% LOAD ‐ 150 MW

Sl. No.

Operating Parameter

Unit

Unit‐1

Unit‐2

Unit‐3

Unit‐4

1.

Generation

MW

151.75

150.46

149.31

150.83

2.

Net Head

M

201.47

201.28

202.30

199.65

3.

Water Flow

m3/s

89.4

89.4

90.1

90.1

4.

Turbine Speed

RPM

212.48

210.91

212.25

210.84

5.

Hydraulic Power

6.

Unit Efficiency

%

87.5

7.

Generator Efficiency (Design)

%

97.42

8.

Turbine Efficiency

%

88.38

Actual Design

MW

176.25

176.21

178.41

176.05

%

86.10

85.39

83.69

85.67

87.65

85.90

87.94

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TABLE 4 UNIT PERFORMANCE AT 85% LOAD ‐ 212 MW

Sl. No. 1.

2.

3.

4.

5.

6.

7.

8.

Operating Parameter

Unit

Unit‐1

Unit‐2

Unit‐3

Unit‐4

Generation Net Head Water Flow Turbine Speed Hydraulic Power Actual Unit Efficiency Design Generator Efficiency (Design) Turbine Efficiency

MW M m3/s RPM MW % % % %

212.2 198.47 118.7 212.1 230.52 92.07 92.2 97.97 93.98

211 197.98 119.5 210.1 231.41 91.2

211.4 198.51 118.9 210 231 91.50

211 196.53 119.3 210 229.33 6.

93.09

93.40

93.93

TABLE 5 UNIT PERFORMANCE AT 100% LOAD ‐ 250 MW

Sl. No. 1.

2.

3.

4.

5.

6.

7.

8.

2)

Operating Parameter

Unit

Unit‐1

Unit‐2

Unit‐3

Unit‐4

Generation Net Head Water Flow Turbine Speed Hydraulic Power Actual Unit Efficiency Design Generator Efficiency (Design) Turbine Efficiency

MW M m3/s RPM MW % % % %

250 196.56 138.5 211 266.48 94.17 93.4 98.18 95.91

252 197.16 140.5 212 271.11 93.00

253.9 196.33 141.2 210 271.42 93.56

251.2 194.67 140.6 211 267.91 6.

94.72

95.29

95.52

Performance at 1000 MW

The performance of all the units was also monitored when operating together at full load and generating 1000 MW of power. The observations are summarized below in table ‐6.

TABLE 6 UNIT PERFORMANCE AT 100% LOAD ‐ 1000 MW

Sl. No. 1.

2.

3.

4.

5.

6.

7.

8.

3)

Operating Parameter

Unit

Unit‐1

Unit‐2

Unit‐3

Unit‐4

Generation Net Head Water Flow Turbine Speed Hydraulic Power Actual Unit Efficiency Design Generator Efficiency (Design) Turbine Efficiency

MW M m3/s RPM MW % % % %

250.5 192.59 140.7 212 265.08 94.52 93.98 98.18 96.28

251.8 193.4 142.4 213 269.38 93.45

245.3 193.3 137.9 214 260.9 94.03

250.7 190.6 143.1 212 266.79 93.96

95.19

95.77

95.7

Performance at 500 MW (with two units on at full load)

The performance of the units was also monitored when operating in combination i.e., with 2 Units operating at full load. The observations are summarized below in table ‐7, 8 &9.

TABLE 7 UNIT ‐1 & UNIT‐2 IN OPERATION

Sl. No. 1.

84

Operating Parameter

Unit

Unit‐1

Unit‐2

Overall

Generation

MW

251

250.6

501.6

2.

3.

4.

5.

Net Head Water Flow Turbine Speed Hydraulic Power

6.

Unit Efficiency

M m3/s RPM MW % %

201.51 140.2 211 276.51 90.80 93.3

193.88 142.3 212 270.05 92.79

197.70 282.6

246.64 91.77

7.

8.

Generator Efficiency (Design) Turbine Efficiency

% %

98.18 92.48

94.51

93.47

Actual Design

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TABLE 8 UNIT‐2 & UNIT‐3 IN OPERATION

Sl. No. 1.

Operating Parameter

Unit

Unit‐2

Unit‐3

Overall 498.8

Generation

MW

249.5

249.1

2.

Net Head

M

196.66

196.47

196.56

3.

Water Flow

m3/s

139

138.1

4.

Turbine Speed

RPM

212

212

277.28

5.

Hydraulic Power

MW

267.80

265.52

533.32

93.17

93.49

6.

% Actual

6.

Unit Efficiency

93.4

93.81

7.

Generator Efficiency (Design)

%

98.18

8.

Turbine Efficiency

%

94.90

95.55

95.22

% Design

TABLE 9 UNIT‐3 & UNIT‐4 IN OPERATION

Sl. No. 1.

4)

Operating Parameter

Unit

Unit‐3

Unit‐4

Overall 501.69

Generation

MW

247.2

254.18

2.

Net Head

M

192.03

189.26

190.64

3.

Water Flow

m3/s

138.8

145.3

284.19

4.

Turbine Speed

RPM

212

212

5.

Hydraulic Power

MW

260.87

269.13

530.09

6.

Unit Efficiency

Actual

%

94.76

94.44

6.

Design

%

93.2

7.

Generator Efficiency (Design)

%

98.18

8.

Turbine Efficiency

%

96.52

96.20

96.34

Performance at 750 MW (Three Units at full load)

The performance of the units was also monitored with three units in operation operating at full load to generate 750 MW. This analysis was done to only verify the variation in the performance of the units in comparison with the analysis made earlier. The observations for the same are summarized below in table 10 &11.

TABLE 10 UNIT‐1, UNIT‐2 & UNIT‐3 IN OPERATION

Sl. No.

Operating Parameter

Unit

Unit‐1

Unit‐2

Unit‐3

Overall

1.

Generation

MW

248.8

251.4

249.0

749.2

2.

Net Head

M

189.47

192.55

196.10

192.71

3.

Water Flow

m3/s

140.7

143.0

138.4

422.7

4.

Turbine Speed

RPM

212

212

212

5.

Hydraulic Power

MW

260.89

269.45

265.50

795.93

6.

Unit Efficiency

Actual

%

95.36

93.31

93.80

94.14

Design

%

93.3

7.

Generator Efficiency (Design)

%

98.18

8.

Turbine Efficiency

%

97.13

95.04

95.54

95.88

TABLE 11 UNIT‐1, UNIT‐3 & UNIT‐4 IN OPERATION

Sl. No.

Operating Parameter

Unit

Unit‐1

Unit‐3

Unit‐4

Overall

1.

Generation

MW

251.6

248.6

251.8

752.1

2.

Net Head

M

196.9

192.03

189.87

192.93

3.

Water Flow

m3/s

139.3

140.9

144.8

425.1

4.

Turbine Speed

RPM

211.3

211.3

212.6

5.

Hydraulic Power

6.

Unit Efficiency

%

93.30

7.

Generator Efficiency (Design)

%

8.

Turbine Efficiency

%

95.45

Actual Design

MW

268.45

264.74

269.06

802.43

%

93.72

93.96

93.57

6.

95.70

95.30

95.46

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Plant Auxiliaries Power Consumption Assessment Ventilation System Ventilation fan systems constitute a key auxiliary, in terms of connected load as well as consumption. Ventilation fan system accounted for 1.3MU consumption per annum and constitute 38.51% of APC. The as run observation data on Ventilation Fans are presented as in table ‐12 & 13 .

TABLE 12 OBSERVATION DATA ON VENTILATION FANS

Performance Assessment of Ventilation Fan System Location: Main Ventilation Intake Chamber Elevation: 640M Sl.No

Item Ref.

1

Air flow rate

2 3 4

Total Head Developed.

Air KW Measured motor input power Combined efficiency of motor, fan & Transmission Fan efficiency (@ Motor eff. 93% & Transmission eff. 97%) % Loading of Fans on flow % loading of fans on head % loading of fans on motor Outlet Damper Open SEC

5 6 7 7 9 10 11

260000 72.222 153 108.33 167.95

As‐Run S1‐1 227907.7 63.308 145 90 166.2

S1‐2 216120.96 60.034 142 83.58 150.13

%

64.51

54.15

55.67

%

70

60.03

61.71

% % % % KWH/1000 m3

Ref. Ref. 80

0.64595

87.66 94.77 78.95 100 0.72924

83.12 92.81 71.31 100 0.69466

Units

Design

CMH CMS mmWC KW KW

TABLE 13 OBSERVATION DATA ON VENTILATION FANS

As‐Run

Sl.No

Item Ref.

Units

Design

S28

S29

Location

Adit‐1

Adit‐3

Elevation

727.5M

633M

CMH

150000

95712.715

116800

CMS

41.667

28.587

32.444

1

Air flow rate

2

Total Head Developed.

mmWC

147

133

132

3

Air KW

KW

60.05

34.67

41.49

4

Measured motor input power

KW

94.08

66.05

84.78

%

63.83

52.49

49.52

%

70

58.81

55.50

7

Combined efficiency of motor, fan & Transmission Fan efficiency (@ Motor eff. 92% & Transmission eff. 97%) % Loading of Fans on flow

7

% loading of fans on head

9

% loading of fans on motor

%

98

68.99

88.55

10

Outlet Damper Open

%

100

100

11

SEC

KWH/1000 m3

0.62722

0.69009

0.72586

5 6

%

Ref.

63.81

77.87

%

Ref.

90.48

89.80

Compressed Air System: 1)

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This energy audit study report highlights the findings of NPC study in compressed air system. The study was carried out during November, 2008 & the units were mostly operating. The various areas covered during the study are given below : 

Evaluation of performance.



Survey of compressed air distribution network.



Review of existing compressed air utilization practices in the station.

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2)

The compressors and compressed air system has a total connected/installed load of 320 KW. The actual running load is about 203 KW. Compressed air systems are auxiliaries accounting for 1.60% of APC and about 0.054 MU per year consumption

Conclusions The paper demonstrates usefulness of operation schedule to improve the operation efficiencies of a real‐life hydro power generation units for multi‐units hydropower generation. Hydro power plant operated at different load conditions to search for the optimal operation sequence of units in terms of total hydropower generation, as well as water consumption efficiency and stability in power generation with greatest efficiency. A comparison of hydropower generation performance at different load conditions indicates that the optimal operation sequence of units significantly improve the existing operational efficiency. The optimization results have been shown to produce more hydropower rather than traditional scheduling for hydropower generation. The applied methods are general without restriction to any particular geographical area/region. They can be applied to other places.Based on the performance analysis of each of the units at different operating conditions, the Unit # 1 is more efficient at 250MW load demand and at the Unit # 3 & 4 are more suitable when power requirement is more than 250 MW and less than 500MW .If power requirement is more than 500 MW and less than 750MW than Unit # 1,2 &3 are more efficient in hydropower production.

ACKNOWLEDGMENT

The author Rishabh Agrawal, is gratefully acknowledged to all the officers and staff members of National Productivity Council, India for his unconditional support and constructive suggestions.

REFERENCES

[1] Ministry of New and Renewable Energy source (MNRE), http://www.mnre. gov.in/achievements.htm.

[2] Aqeel ,Ahmed Bazmi ,Gholamreza Zahedi (2011),”Sustainable energy systems: Role of optimization modeling techniques in power generation and supply—A review”, Renewable and Sustainable Energy Reviews 15 (2011) 3480–3500 [3] P.A.A.Back (1978)“Hydro–electric power generation and pumped scheme utilizing sea”ocean management 4 (1978)179‐206.

[4] Adnan Sözen , Ihsan Alp, Cuma Kilinc (2012) “ Efficiency assessment of the hydro‐power plants in Turkey by using Data Envelopment Analysis” Renewable Energy 46 (2012) 192‐202.

[5] Ministry of power .Available: http://www.powermin.nic.in.

[6] www.ceaindia.gov

R.Agrawal (Author ) Pursuing his Ph.D. from centre of Energy studies in Indian Institute of technolgy (IIT), Delhi. Received his B.E in Mechanical Engineering from the Government engineering college, Jabalpur India, and obtained his M. Tech. School of energy and environment studies DAVV, Indore India.

He is a certified energy auditor from Ministry of Power , Government of India has 10 years experience in the field of Energy Management in all kinds of energy systems.

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