OPTIMIZING OF THE USAGE OF SAMANALAWEWA WATER RESOURCES FOR POWER GENERATION Mangala Pradeep Withana Pathiraja (128774G) Degree of Master of Science Department of Electrical Engineering University of Moratuwa Sri Lanka May 2016 OPTIMIZING OF THE USAGE OF SAMANALAWEWA WATER RESOURCES FOR POWER GENERATION Mangala Pradeep Withana Pathiraja (128774G) Dissertation submitted in partial fulfillment of the requirements for the degree Master of Science in Electrical Installation Department of Electrical Engineering University of Moratuwa Sri Lanka May 2016 i DECLARATION “I declare that this is my own work and this dissertation does not incorporate without acknowledgement any material previously submitted for a Degree or Diploma in any other University or institute of higher learning and to the best of my knowledge and belief it does not contain any material previously published or written by another person except where the acknowledgement is made in the text. Also, I hereby grant to University of Moratuwa the non-exclusive right to reproduce and distribute my dissertation, in whole or in part in print, electronic or other medium. I retain the right to use this content in whole or part in future works (such as articles or books)”. ………………………. Signature of the candidate Date: (M.P.W. Pathiraja) The above candidate has carried out research for the Masters Dissertation under my supervision. ……………………………. Signature of the supervisor Date: (Eng. W.D. A. S. Wijayapala) ii ABSTRACT Samanalawewa hydroelectric project is based on Walawe basin in southern region of Sri Lanka. It includes Samanalawewa reservoir, a water way system and a 120MW power plant as stage (I). Some provisions have been kept for stage (II) to add another 120MW power plant to meet the peak power demand with low cost hydro power. Since the impounding of the reservoir there is a leak around 2.44m3/s and past leak mitigation activities have not succeeded. The leak accounts for more than one fifth of energy loss of the current energy generation by Samanalawewa power plant. The construction of stage (II) is suspended with lower energy generation than expected. This research discusses about a Leak Pump Back System (LPBS) which will curtail the net water outflow from the leak. The LPBS will pump back the leak water to the reservoir and this additional water input can be used to generate power by SPP. The pumping head of LPBS is much lower than the design head of SPP. Therefore The LPBS will consume lower energy than the extra energy generation by SPP. Since the pumped back water is regulated by the reservoir, the extra energy generation is dispatch-able. This will improve the viability of Samanalawewa stage (II). Construction works for a mini hydro power plant is underway using the leaked water. This mini hydro plant can recover less than one third of energy which could have been recovered by LPBS. The LPBS will not divert total leaked water since LPBS will not operate during peak hours and downstream irrigation water demand needs to be provided with leaked water. Therefore the combined operation of mini hydro and LPBS will give more benefits, though the LPBS is going to limit the water supply to the mini hydro plant. Key words: Samanalawewa, Leak, Pump, Peak demand, Hydro iii ACKNOWLEDGEMENT First, I pay my sincere gratitude to Eng. W.D. Anura S. Wijayapala who encouraged and guided me to conduct this study and on preparation of final dissertation. I am glad to extend my sincere gratitude to Prof. N.Wickramarachchi, Head of the Department of Electrical Engineering, University of Moratuwa and all the lecturers and visiting lecturers of the Department of Electrical Engineering for the support extended during the study period. I would like to thank Eng. H.S. Somathilaka, DGM (Samanala Complex), Eng. A.R.M.M.S. Karunasena CE (Samanala Complex), Eng. U.S.H. Ambepitiya, CE (Samanalawewa) of Ceylon Electricity Board who encouraged me and provided required facilities to carry out the study. I also like to thank Eng. H.A.S.C. Karunananda (Operations Engineer – Samanalawewa) and Eng. H.M.D. Herath, (former Civil Engineer – Samanalawewa) for encouraging and sharing their knowledge to make this project successful. Special thank goes to Mr. H.M.N.A.D. Karunananda, (Electrical Superintendent of Samanalawewa Dam Monitoring) and Mr. A.K. Wickremesinghe (Irrigation Departmant, Kaltota Scheme) for helping me to gather required data. Finally I thank all the staff members of operations, electrical maintenance and dam monitoring sections of Samanalawewa Power Station for all the support given in order to complete this project successfully. iv TABLE OF CONTENTS Declaration of the Candidate & the Supervisor i Abstract ii Acknowledgements iii Table of Content iv List of Figures vi List of Tables vi List of Abbreviations vi List of Appendices vii 1. Introduction 1-7 1.1 Background 1 1.1.1 Samanalawewa Hydroelectric Power Project 1 1.1.2 Samanalawewa Reservoir Leak 3 1.1.3 Samanalawewa Mini Hydro Power Project 5 1.2 Importance of the Study 6 1.3 Objectives 6 2. Leak Water Pump Back System (LPBS) 8-20 2.1 The Concept 8 2.2 The Design 8 2.3 Calculations 9 2.3.1 Pump Selection Calculation 9 2.3.2 Input Energy Calculation 13 2.3.3 Validating the Results 13 2.4 Cost Estimations 14 2.4.1 Construction Cost Estimate 14 2.4.2 Operations & Maintenance Cost Estimate 15 2.5 Optimization of LPBS Operations 17 2.6 Financial Analysis 18 2.7 Sensitivity Analysis 20 3. Samanalawewa Stage (II) with LPBS 21-31 3.1 Initial Studies on Samanalawewa Hydroelectric Power Project 21 v 3.2 Studies on Samanalawewa Stage (II) Development 22 3.2.1 CECB Study for Samanalawewa Stage II 22 3.2.2 JICA Study of Hydropower Optimization in SL 24 3.3 New Approach to Evaluate Samanalawewa Stage II 25 3.3.1 Waterway System Capacity 25 3.3.2 Energy Capacity 27 4. Samanalawewa Mini Hydro Project (SMHPP) with LPBS 32-34 4.1 Re-evaluation of SMHPP 32 4.2 Combined Evaluation of SMHPP and LPBS 32 5. Conclusions and Recommendations 35 Reference list 36-37 Appendix 1: Google Earth View of LPBS Site 38 Appendix 2: IRR Calculations on LPBS 39 Appendix 3: Re-Calculation for IRR on Samanalawewa Mini Hydro 40 with 8.07 LKR / kWh Energy Value Appendix 4: IRR on Combined Projects of Samanalawewa Mini Hydro 41 & LPBS Appendix 5: IRR on Samanalawewa Mini Hydro when LPBS 42 is Operated with 16.70 LKR / kWh Energy Unit Selling Rate Appendix 6: Samanalawewa Leakage Portal 43 Appendix 7: Samanalawewa Leakage Flow 43 vi LIST OF FIGURES Page Figure 1.1 Samanalawewa Leak Variation with Reservoir Water Level 04 Figure 2.1 Layout of the LPBS 12 LIST OF TABLES Page Table 1.1: Actual Energy Generation of Samanalawewa 02 Power Plant Table 2.1: Construction Cost for Supply and Install for Each Component 15 Table 2.2: Operations and Maintenance Costs 16 Table 2.3: Data for Financial Analysis of LPBS 18 Table 2.4: Sensitivity Analysis for LPBS 20 Table 3.1: JICA Energy Estimate 25 LIST OF ABBREVIATIONS BHP Brake Hose Power CEB Ceylon Electricity Board CECB Central Engineering Consultancy Bureau dia. Diameter IRR Internal Rate of Return JICA Japan International Corporation Agency LPBS Leak Water Pump Back System MOV Motor Operated Valve msl mean sea level NWS&DB National Water Supply and Drainage Board O&M Operations and Maintenance SMHPP Samanalawewa Mini Hydro Power Project SPP Samanalawewa Power Plant WHP Working Horse Power vii LIST OF APPENDICES Appendix 1: Google Earth View of LPBS Site 38 Appendix 2: IRR Calculations on LPBS 39 Appendix 3: Re-Calculation for IRR on Samanalawewa Mini Hydro 40 with 8.07 LKR / kWh Energy Value Appendix 4: IRR on Combined Projects of Samanalawewa Mini Hydro 41 & LPBS Appendix 5: IRR on Samanalawewa Mini Hydro when LPBS 42 is Operated with 16.70 LKR / kWh Energy Unit Selling Rate Appendix 6: Samanalawewa Leakage Portal 43 Appendix 7: Samanalawewa Leakage Flow 43