Optimizing Of The Usage Of Samanalawewa Water Resources For Power Generation

Abstract

Samanalawewa hydroelectricproject 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 ofthe current energy generation by Samanalawewa power plant. The construction of stage (II)is suspended with lower energy generation than expected. This research discussesabout 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 LPBSwill consume lower energy than the extra energy generation bySPP. Since the pumped back water isregulated by the reservoir, the extra energy generation is dispatch-able. This will improve the viabilityof Samanalawewa stage (II). Construction works for a mini hydro power plantis underway using the leaked water. This mini hydro plantcan 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.