MAXIMIZATION OF ENERGY GENERATION FROM SMALL HYDROPOWER PLANT IN SRI LANKA

Transcription

1 MAXIMIZATION OF ENERGY GENERATION FROM SMALL HYDROPOWER PLANT IN SRI LANKA A dissertation submitted to the Department of Energy Technology, Royal Institute of Technology, Sweden for the partial fulfillment of the requirement for the Degree of Master of Science in Engineering By Pathiranage Guminda Sanjeewa Priyadarshana 2014 Department of Energy Technology Royal Institute of Technology Stockholm, Sweden

2 MAXIMIZATION OF ENERGY GENERATION FROM SMALL HYDROPOWER PLANTIN SRI LANKA By Pathiranage Guminda Sanjeewa Priyadarshana Supervised by OUSL Supervisors: Dr. N.S. Senanayake & Mr. Ruchira Abeyweera KTH Supervisors: Prof. Mark Howells & Mr. Francesco Fuso Nerini 2

3 Declaration The work submitted in this thesis is the result of my own investigation, except where otherwise stated. It has not already been accepted for any other degree and is also not being concurrently submitted for any other degree. Pathiranage Guminda Sanjeewa Priyadarshana Date We/I endorse declaration by the candidate. Dr. N.S. Senanayaka & Mr. Ruchira Abeyweera (OUSL Supervisors) Prof. Mark Howells & Mr. Francesco Fuso Nerini (KTH Supervisors) 3

4 Abstract Sri Lanka has a number of small waterfalls and channels. Related to this there is a significant potential to develop small hydropower plants, thus to generate much needed electricity for country s development efforts. Small hydro power plants cause less environmental effects compared to large scale hydro power generation and power generation using fossil fuel. Therefore, it is a timely requirement to explore the possibilities of utilizing small water streams to generate electricity as much as possible as well as to optimize the energy generation with the available water in those water streams. The importance of small hydro power is highlighted in the Sri Lanka s energy generation plan, and the Ceylon Electricity Board (CEB) annual report states that in year 2011 total installed capacity of small hydro plant was around 200MW and it is expected to expand energy generation to around 800GWh. This study focuses on finding out optimum operating parameters to maximize the energy generation of existing small hydro power plant in the country. By selecting a few small hydro power plants, preliminary studies were performed to identify optimum values of water flow rate to maximize the efficiency of the power generation. The study revealed that the selected plants had not operated at the maximum efficiency; hence they did not optimally utilize the available water. 4

5 Acknowledgments I would like to express my sincere gratitude to Professor Torsten H. Fransson Head, Department of energy technology for expanding the DSEE Programme to Sri Lanka and pave the way for us to explore the world of sustainable energy engineering. I am really grateful to Professor Mark Howells and Mr. Francesco Fuso Nerini for their unwavering guidance, support towards successful research activity. I specially thank my local supervisors, Dr. N.S. Senanayaka and Mr. Ruchira Abeyweera for their unwavering guidance, support and advice for carrying out this research work successfully. I am also very appreciative for their extensive help in fulfillment of some publications related to this research work, in some prestigious international forums. I am indebted to my parents, wife and son for constant support and encouragement for successfully carrying out this work. My gratitude also due to all academic staff of Open University Sri Lanka, all academic staff of KTH Sweden and Sri Lanka Sustainable Energy Authority for the support given with my studies. I have been assisted extensively by Mr. Asela, Mr. Manjula Wickramathilaka in obtaining required measurements and data for the research activity which I should greatly appreciate. Finally, my thanks go to various other personnel without whose help this work wouldn t be a success. Understandably, their individual names cannot be mentioned here due to being large in number. 5

6 Table of contents Declaration...3 Abstract...4 Acknowledgement....5 Abbreviation...7 List of figures... 8 List of tables. 9 1 Introduction Litterature survey Hydropower sector in Sri Lanka Problem formulation and objectives Method Analysis of Data Data collected from Ella Pita Ella Small hydro plant Data collected from Kebilladowa Small hydro plant Data collected from Watawala Small hydro plant Electrical power flow rate curves Turbine efficiency flow rate curves Maximum energy from the available water Kebilladowa Plant Watawala Plant Conclusions and future work...35 References...37 Annexure A: Rain fall data of Nuwara Eliya ( )...38 Annexure B: Rain fall data of Watawala ( )..39 Annexure C: US 300PM Protable Ultrasonic Flow Meter Catalogue..40 AnnexureD: US 300PM Protable Ultrasonic Flow Meter Photogrphs of Flow Measurements at Ella Pita Ella Small Hydro Power Plant

7 Abbreviation g Q H a P T CEB MHPP SHPP SLSEA DMSL Overall efficiency Gravitational Constant Water flow Rate Water head Constant Generator electric power output Time period of operation at optimum condition Ceylon Electricity Board Mini hydro power plant Small hydro power plant Sri Lanka Sustainable Energy Authority Department of Meteorology Sri Lanka Subscripts n n th element 7

8 List of figures Figure Original and Degrade Performance curves of turbine Figure Efficiency curves of typical hydro turbine Figure CO 2 emission data analysis in Figure The electricity generation in CEB Figure Typical layout of hydro power plant Figure 4.4 Electrical Power Vs. Average Flow Rate Figure Turbine Efficiency vs. Flow Rate curve for Ella Pita Ella SHPP Figure Turbine Efficiency vs. Flow Rate curve for Kebilladowa SHPP Figure Turbine Efficiency vs. Flow Rate curve for Watawala SHPP Figure Comparison of actual flow rate and optimum flow rate on monthly basis for Kebilladowa SHPP Figure Actual generation of energy and the optimum generation on monthly basis for Kebilladowa SHPP Figure Loss of generation due to non-operation of the plant at optimum efficiency for Kebilladowa SHPP Figure Comparison of actual flow rate and optimum flow rate on monthly basis for Watawala SHPP Figure Actual generation of energy and the optimum generation on monthly basis for Watawala SHPP Figure Loss of generation due to non-operation of the plant at optimum efficiency for Watawala SHPP

9 List of tables Table 1.2.1Hydro Power Plant Category Table Total Energy generation Laxapana Complex Table Total Energy generation Mahaweli Complex Table Total Energy generation Other Hydro Complex Table Age analysis of hydropower stations in Sri Lanka.. 21 Table 4.1 Summary of data from Ella Pita Ella Small Hydro Plant Table 4.2 Summary of data from Kebilladowa Small Hydro Plant Table 4.3 Summary of data from Watawala Small Hydro Plant Table 4.4 Electrical Power and Average Flow Rate data.. 26 Table Summary of overall efficiency calculation for Ella Pita Ella Power Plant 27 Table Summary of overall efficiency calculation for Kebilladowa Power Plant Table Summary of overall efficiency calculation for Watawala Power Plant..28 Table Details calculation results of Kebilladowa SHPP Table Detail calculation results of Watawala SHPP

10 1 Introduction The government owned Ceylon Electricity Board (CEB) is the main producer and the provider of electricity in Sri Lanka. CEB generation divisions consist of sixteen large hydro power plants totaling to an installed capacity of 1205 MW. As per the annual report of CEB most of them exceeded their 25 years of operation. The rest of the small hydro power plant is mainly owned by private power producers. At the same time there are large numbers of rural hydro power projects which are available most frequently in the area of still not covered by national grid. Hydro power unit cost is around 1.50 Sri Lanka rupees whereas thermal power generation takes it more than Sri Lanka rupees. Therefore effectiveness and improvement of hydro power generation more effective to national economy of Sri Lanka. In the backdrop of end of conflict situation that existed for over 30 years, Sri Lanka has is geared to fast development and the expansion of economic activity. This situation inevitably call for higher energy demands that the country could not meet unless it focus on new sources as well as maximizing efficiency of power generation together with sustainable utilization. In this scenario, hydro power generation has a major role to play, and furthermore with the reach of limit in exploitation of large hydro power sources, small water streams can make a major impact in satisfying the demand at affordable costs. Therefore, it is very timely requirement to study the problems of the present small hydro power plant and research on ways and means to optimize the energy generation from these resources. In view of searching solutions to this uncertain situation in the energy sector, this study was undertaken to find out possible means of maximizing the water potentials in small hydro power generation. 1.1 Literature survey Hydropower is energy that comes from the force of moving water. The fall and movement of water is part of a continuous natural cycle called the water cycle. Energy from the sun evaporates water in the Earth s oceans and rivers and draws it upward as water vapour. When the water vapour reaches the cooler air in the atmosphere, it condenses and forms clouds. The moisture eventually falls to the Earth as rain or snow, replenishing the water in the oceans and rivers. Gravity drives the water, moving it from high ground to low ground. The force of moving water can be extremely powerful. Hydropower is called a renewable energy source because the water on 10

11 Earth is continuously replenished by precipitation. As long as the water cycle continues, we won t run out of this energy source [1]. Hydropower has been used for centuries. The Greeks used water wheels to grind wheat into flour more than 2,000 years ago. In the early 1800s, American and European factories used the water wheel to power machines. The water wheel is a simple machine. The water wheel is located below a source of flowing water. It captures the water in buckets attached to the wheel and the weight of the water causes the wheel to turn. Water wheels convert the potential energy (gravitational energy) of the water into motion. That energy can then be used to grind grain; drive sawmills, or pumps water. In the late 19 th century, the force of falling water was used to generate electricity. The first hydroelectric power plant was built on the Fox River in Appleton, WI in In the following decades, many more hydroelectric plants were built. At its height in the early 1940s, hydropower provided 33 percent of this country s electricity. By the late 1940s, the best sites for big dams had been developed. Inexpensive fossil fuel plants also entered the picture. At that time, plants burning coal or oil could make electricity more cheaply than hydro plants. Soon they began to underprice the smaller hydroelectric plants. It wasn t until the oil shocks of the 1970s that people showed a renewed interest in hydropower [1]. Devapura Jayasena Wimalasurendra ( ) was a Sri Lankan engineer who played a prominent role in the establishment of hydropower in Sri Lanka and is known as the "Father of Hydropower. Having had his initial proposals on hydro power he constructed the first Ceylon's small hydro power station in at Blackpool, between Nanu Oya and Nuwara Eliya, to supply electricity to the Nuwara Eliya town. In 1918 he submitted a paper to the Engineering Association of Ceylon titled "Economics of Hydro Power Utilization in Ceylon", in it he proposed the possibility of hydro power from Maskelioya and Kehelgamuoya capable of lighting 100,000 lamps (114.5 MW) and the concept of developing a national grid [2]. With his initiation Sri Lankan hydro power generation sector was groomed to present condition and Sri Lanka energy sector has enriched with hydro power generation, approximately it could be higher than 45% of total generation as per the data shown in CEB annual report Hydro power contributes around 45% of the national electricity generation in year 2010, whereas wind contributes less than 1% of total generation [3]. As a renewable energy source it has become more important economical resource compared to other renewable sources. Hydro power produces no direct waste and contribution to CO 2, green house gasescompared to fossil fuel plants.at present, all most all hydro potentials available in the country have been utilized for electricity generation and few remaining are under construction.therefore it is very important to improve the efficiency of the existing power plants. 11

12 The performance levels for the turbine design could be identified as three levels such as Installed Performance Level (IPL), Current Performance Level (CPL) as well as Determination of Potential Performance Level (PPL). The Installed Performance Level (IPL) is described by the unit performance characteristics at the time of commissioning. These may be determined from reports and records of efficiency and/or model testing conducted prior to and during unit commissioning. The Current Performance Level (CPL) is described by an accurate set of unit performance characteristics determined by unit efficiency testing, which requires the simultaneous measurement of flow, head, and power under a range of operating conditions, as specified in the standards referenced in this document. Determination of the Potential Performance Level (PPL) typically requires reference to new turbine design information from manufacturer to establish the achievable unit performance characteristics of replacement turbine. Turbines installed performance level (IPL) degrade after operating it long time period and ended up with lower efficiency than design values. As can be seen in figure 1.4 the turbine efficiency reduce after operating it long time period [7]. According to previous research activity (Figure 1.4) the Overall efficiency of the turbine was reduced from 90% to 86% approximately during the period of operation from 1950 to Figure Original and Degrade Performance curves of turbine (Source: HAP best practices catalogue Francis turbine) With the change of turbine size and type efficiency characteristic curves will be differ from one to another. It could be observed each and every type of turbine has coherent peak efficiency range at particular flow rate range, It could be seen in figure 1.5 [8]. 12

13 Figure Efficiency curves of typical hydro turbine (Source: HAP best practices catalogue Francis turbine) As can be seen in above figures (Figure and Figure 1.1.2) turbine performance curve will change with time period of operation as well as turbine type and sizes. Other important matter is at a particular water flow rate every given turbine gives its peak efficiency. Therefore it is very important to consider above characteristic for the purpose of enhancing maximum energy output from a given particular water resource. The selection of type of turbine is one of the problems in design of hydro plant. The characteristics, parameters, and classification involved facilitate the choice of turbine. There are two methods of selection. The first method is graphical selection. It is the various types of turbine, graphs relating discharges, head work, model test result, and test report. Turbine is selected according to the head and discharge values. The Analytical Selection will be the second method. According to the head and discharge values, the turbine parameters are calculated using the formula and conclude turbine type [9]. As a thumb rule pelton wheel type turbine is suitable where high water head and low specific speed applications. If the water head and specific speeds are medium it could be suitable Francis type turbine. Whereas low water head and high specific speed applications are goes for Kaplan and Propeller type turbine selection. Where Specific speed (N s ) is a dimensional parameter used to characterize turbo machinery speed. In order to enhance small hydro power plant efficiency it is very important to conduct both absolute and relative efficiency tests of hydro turbines. It is invariably in the best interest of a power plant to have the efficiency of its hydraulic turbines to measure at the start of operation 13

14 and subsequently at regular intervals [10]. Normally large type turbines performance is determined initially in model test and consequently absolute installation and testing. During the efficiency testing of the turbine it s normally tested whether the manufacturer recommended performance have been met, and checking for the adjustments of blades and gate mechanism as well as the hydraulic governor. In the same time it could obtain information that could be used to evaluate machine wear and cavitations. Prototype turbine installations always have some differences from their models which alter their performance characteristics. The model must be subjected to conditions that would be detrimental to a prototype such as severe and maximum runway speed [10]. However turbine model test is very important to identify full performance of the system in actual situation. There are two basic types of turbine efficiency testing the absolute and the relative. These terms denotes whether the discharge is measured absolutely or in relation to some other known parameter. The absolute methods are invariably more complex, expensive and difficult; and are generally done only once to ensure the contract guarantees have been meat. The discharge water flow rate measurement will be vital to analyse the current performance of the turbine and the following techniques methods could be used to measure the water flow rate [10]. 1. Gibson Method: The changing the momentum of the fluid column resulting from a load change is measured to determine the flow rate. 2. Allen Salt Velocity Method: The time for the passage of an injected saline solution two electrode station is measured to determine the flow rate. 3. Weir Method: A calibrated weir, usually downstream is used to measure discharge. 4. Piezometer Traverse Method: Piezometers are used to determine the velocity profile which is integrated over the cross-sectional area to determine flow rate. 5. Current Meter Method: Same as the piezometer traverse expect for the use of current meter instead of piezometers. 6. Sonic Method: Acoustic transducers are used to measure the Doppler or phase shift between two stations the average flow rate separating the two. 7. Thermodynamic Method: Minute changes in the temperature of the discharge water compared with the incoming are used to evaluate efficiency. The relative efficiency testing is comparatively easier than absolute method. For the flow is only measured relative to or is indexed against some parameter which is a direct function of flow rate. Almost any parameter will do, such as venturi suction in the penstock or the friction head loss in a penstock or the centrifugal force of the flow around a bend and so on [10]. 14

15 1.2 Hydro power sector in Sri Lanka With the increasing electricity demand, Sri Lanka has to think about efficiency improving of the existing hydro power plants or implementing new thermal power plants with comparatively higher cost and higher environment effects. Presently Sri Lanka has implemented 300 MW of coal power plant in Puttalam area, and idea is to extend coal power Generation Island wide. As can be seen in figure 1.1, coal power plants and other thermal generation create more environmental adverse effects compare with small & lager hydropower plants. On the other hand power generation cost per is very high in thermal power generation compared with hydro power generation. As per the Ceylon Electricity Board (CEB) data in year 2010, power generation cost per one unit of energy (kwh) for hydro Rs whereas thermal generation it s goes up to Rs Figure CO 2 emission data analysis in 2013 (Source: statistics 2013) Renewable energy technologies are getting cheaper and environment friendly [11]. As amongst renewable technologies Hydro Power in Sri Lanka is already a consolidated technology and with relevant potentials, Sri Lanka energy sector has to think about improvement and efficient usage of the available water resources island wide. Hydro power plant could be categorized from Pico hydro plant to small & large hydro plant and this research work focuses on small hydro plants. Table 1.2.1: Hydro Power Plant Category (Source: Hydro Power Plant Pico Hydro Power Plant Micro Hydro Power Plant Small Hydro Power Plant Large Hydro Power Plant Capacity Less than 5 kw 5 kw to 100 kw 100 kw to 10 MW More than 10 MW 15

16 Most of the large scale power plants are owned and operated by CEB whereas Pico, Micro and small hydro plants are most probably owned and operated by private companies. As can be seen in figure 1.2, reasonably higher contribution of energy generation is come from hydro power plant in Sri Lanka. Figure The electricity generation in CEB (Source: CEB annual report 2010) Micro or small hydro, wind, biomass and solar are the main renewable sources capable of offering a sustainable contribution to the Sri Lanka s electricity generation apart from large scale hydro power generation. Penetration of renewable energy to the electricity generation sector has been extremely limited by the various constraints such as lack of investment, attitudes, technology and management of resources. However, during the recent past some interest has been shown in the construction of small-hydro plants due to its relatively low capital investment and greater opportunities for grid connection [4]. In general small hydro power plant electrical power output range from 100kW to 10 MW. Since the most suitable source of energy generation to Sri Lanka would be hydro power this research activity mainly focus to enhance hydro power generation. Therefore, it is essential to obtain the maximum capacity from the existing plants by improving the efficiency as much as possible. As 16

17 can be seen in figure 1.3 the major components of hydro power plant could be identified as water diversion & screens, pipe line (penstock line), turbine and generator set, tailrace as transmission line. Therefore hydro power plant efficiency will be depended on friction effects of pipelines, internal blocking of flow path as well as turbine generator set efficiency. Figure Typical layout of hydro power plant (Source: An introduction to hydro power concepts and planning, a publication of canyon hydro) Mahaweli Hydro complex, Laxapana Hydro Complex and Other Hydro Complexes contributes 40% of the total requirement to the national energy supply while the rest is coming from thermal Power, mainly diesel and coal. Laxapana Power Complex, having a total installed capacity of 335MW, comprises of five main generating stations at four locations. These include the first major hydro power station in Sri Lanka, i.e. Old Laxapana Generating Station, which was built on a pioneering proposal of the visionary engineer, late Mr. D.J. Wimalasurendra. These Power Stations are situated in cascade in two contributory streams of Kelani River; Wimalasurendra and Old Laxapana plants fed by KehelgamuOya, and Canyon and New Laxapana Plants fed by MaskeliyaOya, while Samanala PowerStation at Polpitiya is finally supplied with water from both these streams. The total Power Generation of the Laxapana Complex was 1,779.5 GWh the year 2010, which accounts for 17.8% of the total generation of the network. during 17

18 Table 1.2.2: Total Energy generation Laxapana Complex (Source: Ceylon Electricity Board, Generation data 2010) Mahaweli Complex will be the next hydro power scheme which comprises of Kotmale, Victoria, Randenigala, Rantambe, Ukuwela, Bowatanna and Nillambe Power Stations. The total installed capacity of the Complex is 666 MW. Mahaweli Complex had generated 2,445 GWh during the year 2010, which accounts for 22.8% of the total generation of the network. In addition to the planned maintenance activities of power stations, replacement of the defective excitation system with Brushless Excitation of two generators at Kotmale Power Station, and the Procontic Control System at Randenigala Power Station were in progress during the year. Table 1.2.3: Total Energy generation Mahaweli Complex (Source: Ceylon Electricity Board, Generation data 2010) Other than the main complexes few hydro power plants are taking in to consider as other hydro complex which is comprises of Samanalawewa, Kukule, Inginiyagala, and Udawalawe hydro power stations and Hambantota Wind Power Station. The installed capacity of the Complex is 213 MW. Other Hydro Complex generated 767 GWh during the year 2010, which accounts for 7.2% of the total generation of the network. It is to note that the operating patterns of Inginiyagala and Udawalawe are solely dependent on the irrigation water releases, and hence the low plant factors attributed to these stations. 18

19 Table 1.2.4: Total Energy generation Other Hydro Complex (Source: Ceylon Electricity Board, Generation data 2010) Ukuwella power station, Old Laxapana and New Laxapana hydro power plants are already exceed their life span more than 25 year and CEB has plan to rehabilitate them in order to enhance efficiency of the system. CEB entered into a contract with consortium of Mitsubishi Corporation, Japan and Indo East Engineering and Construction (Lanka) Pte Ltd for rehabilitation works of Ukuwela Power Station, initially commissioned in Under this rehabilitation project, Turbines, Generators and their associated equipment will be replaced and/or rehabilitated in order to achieve better efficiency and reliability of the plant at a total cost of Rs. 1,800.0 million. About 85% of this cost is funded by the JBIC on export credit basis and the Loan Agreement between Ministry of Finance and JBIC was signed in February In terms of the Agreement, the Contract is in force from April 2008, and the works will be completed by the end April 2011 and presently work has completed. Under Laxapana Power plant rehabilitation project, 2 x 50 MW New Laxapana and 2 x 25 MW Wimalasurendra Power Plants will be refurbished and modernized. Under this contract, the Generator, Turbine Control and Auxiliaries will be rehabilitated or replaced at a cost of Rs. 6,500 million. Alstom Hydro France is the contractor for project and 85% of the contract value is provided by Credit Agricole CIB, France on Export Credit terms and balance 15% is funded by Hatton National Bank. The Project works started in February 2008 and completed during year Most of hydro power plants in Sri Lanka where constructed and put into operation more than 20 years ago and now they are having long period of operation time. Since the long period of operation, turbine performance may change with their original condition. Therefore the research activity mainly focuses on overall efficiency of turbine generator set. Electricity generation sector of Sri Lanka has higher potential of sustainable energy development and improvement. As far concern about sustainable energy sources, small hydro, wind and biomass would play vital role. 19

20 Small hydro power is one of the most efficient and well elaborated kinds of renewable sources of energy [5]. According to CEB annual report data during the year 2010, four wind power projects of total capacity 30 MW have been connected to the grid. The total generation was 50 GWh. By the end of the year, CEB has entered in to 8 Standardized Power Purchase Agreements (SPPA) for an aggregate capacity of 119MW. SPPA's have been signed for 8 plants of total capacity 92MW. The construction of some of the above wind plants are in progress. Biomass will be the next alternative renewable energy source in Sri Lanka. Biomass Power plants consist of three main categories such as Dendro, Municipal Waste and Agricultural and Industrial Waste. With regard to Biomass Power Projects, there are two Agricultural and Industrial waste power plants of total capacity of 11MW have been connected to the grid. The total generation was 32GWh and the same for the year 2009 was 23GWh. By the end of the year, CEB has entered in to 08 Standardized Power Purchase Agreements (SPPA) for an aggregate capacity of 37MW. During the year 2010, three small hydro power projects of total capacity 3.7 MW were connected to the grid. The total grid-connected installed capacity of 84 small hydro power plants reached 170 MW by the end of the year. The total energy generated by these was 642 GWh and for the year 2009 the corresponding amount was 524 GWh. By the end of 2010, CEB has entered in to 61 Standardized Power Purchase Agreements for an aggregate capacity of 119MW [3]. According to above literatures Sri Lanka energy sector mainly enrich with hydro power and it contribute more than 45% of total requirement. Electricity generated in three major hydropower complexes such as Mahaweli Hydro complex, Laxapana Hydro Complex and Other Hydro Complexes contributes 40% to the national energy supply while the rest is coming from thermal power, mainly diesel and coal. Hence, obtaining the maximum possible share from hydropower has the potential of giving overall benefits to the national economy. In order to enhance hydro power generation CEB has initiated few rehabilitation projects as well as new construction project such as rehabilitation project of Ukuwela power station, rehabilitation project of new & old Laxapana power station, construction projects of Upper Kotmale and Broadland power station etc. 20

21 Table 1.2.5: Age analysis of hydropower stations in Sri Lanka (Source: Ceylon Electricity Board, Generation data 2010) Name of the Station Installed Capacity (MW) Inginiyagala Norton 50 Udawalawe 6 Old Laxapana 50 Polpitiya 75 Ukuwela 40 Bowatenna 40 New Laxapana 100 Canyon 60 Kotmale 201 Victoria 210 Samanalawela 120 Randenigala 122 Nilambe 3.2 Rantambe 50 Kukule 70 Commissioned year Age (years) As per the data collected from CEB, around 95% of existing hydro power plants in Sri Lanka have passed the 25 year limit of their life span and previous research activities proves efficiency deviation with the operating time periods [6]. With the existing energy demand Sri Lanka is not in a situation to replace old-hydro power plants, within a short period and also its energy production is mainly depends on hydropower. Age analysis of the hydropower plants in Sri Lanka is shown in Table 1. Therefore, it is essential to obtain the maximum capacity from the existing plants by improving the efficiency as much as possible. As can be seen in figure 1.3 the major components of hydro power plant could be identified as water diversion & screens, pipe line (penstock line), turbine and generator set, tailrace as transmission line. Therefore hydro power plant efficiency will be depended on friction effects of pipelines, internal blocking of flow path as well as turbine generator set efficiency. 21

22 2 Problem formulation and objectives This research activity mainly focuses on overall efficiency of turbine generator set. Since the most of hydro power plants in Sri Lanka have passed 25 years limit of their life span, field performance testing of hydraulic turbine is required to find head, power, flow rate relationship which identify the turbine s peak operating point [6]. As per the literature review it was identified that turbines performance level goes down with the time periods of operation. Most of the hydro power plants of Sri Lanka had installed more than 25 years ago. Therefore turbines efficiency and performance could be change from its original value and optimum level of operation may not be come in to play in present operation condition. Therefore this research activity is aiming to find out optimum level of operation and possible extra energy harness from existing water resources. The objective of this research activity can be listed down as follows: To identify operation difficulties of small hydro power plants that result in reduction of total energy generation in Sri Lanka. Establish operating conditions or operating pattern of small hydro power plant that will give maximum energy output. 22

23 3 Method Three small hydro plants were selected as a sample for the study. These were namely Ella Pita Ella, Kebilladowa and Watawala. The flow rates were measured at different power outputs for each plant. The efficiency was computed at different flow rates to obtain the efficiency variation with the flow rate. The Ella Pita Ella small hydro power plant was analyzed only for the observation of efficiency & flow rate characteristic curve. Then it could extend for other small hydro plant which has little bit higher installed capacities. The flow velocity was measured with the simple float method using plastic ball without rope. When the measurements were taken the power generation of the plant was adjusted by controlling the flow rate. Also channel width and flow height were measured to determine the volume flow rate. The turbine efficiency was calculated using the following formula for different measured values of the electrical power output. Where Turbine efficiency values were plotted against the flow rate to obtain the efficiency-flow characteristic curve for each plant. The actual monthly average flow rates available from past records were used to determine the volume of water consumed in each month. 23

24 In the computation, it was assumed that the plant is in operation 24h day and all days in a month. Then, the number of hours (T) for utilizing this amount of water at maximum efficiency is determined by dividing Va by the optimum flow rate (Q opt ) corresponding to the maximum turbine efficiency which is obtained from the efficiency -flow characteristic curve for each plant. The energy (E opt ), which could be generated by operating the plant for time T was calculated by using the following equation. In the same manner, the actual energy (E a ) generated in the particular month was calculated using the following formula for comparison with E a. 24

25 4 Analysis of data 4.1 Data collected from Ella Pita Ella Small hydro plant: Installed capacity -600 kw Penstock line Diameter = 30 cm Cross flow type turbine H- Head (m) = 70 m Table 4.1 Summary of data from Ella Pita Ella Small Hydro Plant Power (kw) Flow(m 3 /h) (Test 1) Flow(m 3 /h) (Test 2) Flow(m 3 /h) (Test 3) Flow(m 3 /h) (Average) Data collected from Kebilladowa Small hydro plant: Installed capacity -900 kw Penstock line Diameter = 35 cm Pelton wheel type turbine H- Head (m) = 145 m Table 4.2 Summary of data from Kebilladowa Small Hydro Plant Power (kw) Flow(m 3 /h) (Test 1) Flow(m 3 /h) (Test 2) Flow(m 3 /h) (Test 3) Flow(m 3 /h) (Average)

26 4.3 Data collected from Watawala Small hydro plant: Installed capacity -1MWx2 Penstock line Diameter = 40 cm Turgo Impulse type turbine H- Head (m) = 98 m Table 4.3 Summary of data from Watawala Small Hydro Plant Power (kw) Flow(m 3 /h) (Test 1) Flow(m 3 /h) (Test 2) Flow(m 3 /h) (Test 3) Flow(m 3 /h) (Average) Electrical power flow rate curves Table 4.4 Electrical Power and Average Flow Rate data Electrical Power (kw) Flow(m3/h) (Average) Ella Pita Ella Kebilladowa Watawala

27 Figure 4.4 Electrical Power Vs. Average Flow Rate 4.5 Turbine efficiency flow rate curves The efficiency values were calculated using the equation (3.1) for all three plants. Table Summary of overall efficiency calculation for Ella Pita Ella Power Plant Power (kw) Flow (m 3 /h) Mechanical Power (kw) Overall Efficiency (%) Table Summary of overall efficiency calculation for Kebilladowa Power Plant Power (kw) Flow (m 3 /h) Mechanical Power (kw) Overall Efficiency (%)

28 Table Summary of overall efficiency calculation for Watawala Power Plant Power (kw) Flow (m 3 /h) Hydraulic Power (kw) Overall Efficiency (%) Figure Turbine Efficiency vs. Flow Rate curve for Ella Pita Ella SHPP Maximum point: Turbine Efficiency, η t =73.3% Flow Rate, Q (m 3 /h) =

29 Figure Turbine Efficiency vs. Flow Rate curve for Kebilladowa SHPP Maximum point: Turbine Efficiency, η t =79.9% Flow Rate, Q (m 3 /h) =1270 Figure Turbine Efficiency vs. Flow Rate curve for Watawala SHPP Maximum point: Turbine Efficiency, η t =73% Flow Rate, Q (m 3 /h) =

30 4.6 Maximum energy from the available water Kebilladowa Plant The maximum or optimum energy generation from the available water in each month calculated using the equations 3.2, 3.3 and 3.4. The following is the sample calculation carried out for the Kebilladowa plant for month of January. Water volume No. of hours for utilizing this amount of water at optimum flow of 1270m 3 /h = T Actual efficiency is taken from the Efficiency Vs. flow rate curve in Fig Actual Energy Energy at optimum operating condition, 30

31 Table below gives the calculated values for and for all months. Figure compares the actual flow with the optimum flow rate in order to achieve the maximum efficiency. Also Figure and Figure illustrate the variations of month actual energy with the optimum values and the losses or water energy not converted to electrical energy respectively. Table Details calculation results of Kebilladowa SHPP Month Q a (m 3 /h) Va(m 3 ) T (h) ηa Ea(GWh) E opt loss (GWh) (GWh) January February March April May June July August September October November December Optimum flow rate, 1270m3/h Figure Comparison of actual flow rate and optimum flow rate on monthly basis for Kebilladowa SHPP 31

32 Figure Actual generation of energy and the optimum generation on monthly basis for Kebilladowa SHPP Figure Loss of generation due to non-operation of the plant at optimum efficiency for Kebilladowa SHPP 32

33 4.6.2 Watawala Plant Similar calculations as for the Kebilladowa plant carried out for the Watawala plant and results are given in the Table Table Detail calculation results of Watawala SHPP Month Q a (m 3 /h) Va(m 3 ) T (h) ηa Ea(GWh) E opt loss (GWh) (GWh) January February March April May June July August September October November December Figure Comparison of actual flow rate and optimum flow rate on monthly basis for Watawala SHPP 33

34 Figure Actual generation of energy and the optimum generation on monthly basis for Watawala SHPP Figure Loss of generation due to non-operation of the plant at optimum efficiency for Watawala SHPP 34

35 5 Conclusions and futurework Sri Lanka relies mainly on hydro power and thermal power that utilizes imported fossil fuels. According to the CEB annual report 2010, in that year the hydro power generation was 5720 GWh and thermal power generation was 4955 GWh. The research has shown that hydro power generation using large rivers is limited, and by now Sri Lanka has utilized all such possibilities. This situation naturally leads to thermal power as a convenient alternative, but with high cost in the backdrop of ever increasing fuel prices. By the mid of 2011 Sri Lanka has commissioned and commercially startup first ever coal power plant in puttalam area with the collaboration of Chinese government. The number of Thermal power plant increasing means more adverse effect on economy as well as socio environmental conditions of Sri Lanka. The next option available is to explore the renewable energy sources like solar, wind and biomass, and micro or small hydro power generation using small streams of water ways. Apart from renewable energy sources such as solar and wind, small hydro power generation is one of the promising renewable energy sources to be explored in the country with the reaching of maximum utilization of hydro power generation using large rivers. It has been identified that about 600 small scale hydro power plants capable of adding about 500MW of power to the national grid are available in the country [4]. On the other hand existing power plant performances have to check and using possible methods it should improve to enhance energy output from a particular water resource. In a recent study carried out to determine the performance of Small hydro power plants in the country revealed that they did not reach the expected targets. According to the findings of previous researchers, major issues which severely affected the plant performance were found to operational issues and the improper or lack of maintenance. In design stage faults also contributed to reduced generation capacity as well [4]. The objective of the research activity was to investigate selected Small hydro power plants to determine the actual performance and the possibilities of improvements. Three Small hydro plants were selected for the study. According to the literature review findings Electricity generation sector of Sri Lanka enrich with substantially higher amount of hydro power generation. Ceylon Electricity Board and Sri Lanka government further planned to extend hydro power generation with the aids of foreign countries like Japan and China. On the other hand most of the existing hydro power plant in Sri Lanka exceeds more than 25 years of their life span and their performance level differ from original design condition. In order to find out their optimum operating conditions power plant authorities may have to perform actual testing work with some analysis. 35

36 Hydro power plants of Sri Lanka vary from Pico hydro power station (Up to 10 kw) to large scale hydro power station (Above 10 MW). Here this research activity mainly focuses on Small hydro power plants and with the measurements taken during actual operating condition possible energy saving was calculated. Based on the results Kebilladowa Small hydro power plant and Watawala Small Hydro Plants have potential to improve energy extraction up to 5% ~10% from annual generation. This would however require additional costs for the improvement of water storage capabilities in the evaluated case studies. With a proper utilization of water resources by means of storage system there is possibility to improve hydro power sector efficiency. This type of interventions could help avoiding the requirement of new thermal power plant installation. 1kWh of thermal energy generation replacement by renewable energy means it s reduces 2 lbs CO 2 emission to the environment (As can be seen in figure 1.2.1). In order to enhance green technology and make human friendly environment these research findings could be helpful to the Sri Lanka. 36

37 References [1] (01/09/2013) [2] (01/09/2013) [3] Ceylon Electricity Board Annual Report [4] D.H.G.S.R. Somasundara, A.M.A.J. Abeywardana, I.U. Attanayake and N.S. Senanayake Problems associated with mini hydro power plants for successful operation- a case study in Sri Lanka. [5] Blyashko, Ya. I. Modern Trends in the Development of Small Hydro Power around the World and in Russia, Thermal Engineering, 2010, Vol. 57, No. 11, pp [6] Jessica Brandt and Jay Doering, Towards of improved model for predicting hydraulic turbine efficiency, University of Manitoba. [7] HAP best practices catalogue Francis turbine, Prepared by MESA ASSOCIATE INC, Chattanooga. [8] Short-cut design of small hydroelectric plants, N.G. Voros, C.T. Kiranoudis and Z.B. Maroulis, Department of Chemical Engineering, National Technical University of Athens, Polytechnioupoli,Zografou,Athens. [9] M. Borota, Mini Hydro Power Plants Green Power for Users, Directorate for Water Management, Ministry of Agriculture, Forestry and Water Management, MeritaBorota, Serbia, [10] L.H. Sheldon, Field testing and optimizing efficiency of hydro turbines, water power & Dam Construction January [11] (20/02/2014) 37

38 Annexure A: Rain fall data of Nuwara Eliya ( ) Source: Department of Meteorology Sri Lanka 38

39 Annexure B: Rain fall data of Watawala ( ) Source: Department of Meteorology Sri Lanka YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA Avg NA- Not Available 39

40 Annexure C: US 300PM Protable Ultrasonic Flow Meter Catalogue 40

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