Optimization of Hydropower Plants’ Tailwater Energy: A Case Study for 317 MW Adana Sanibey Dam, Turkey

This work is concerned with the optimization of use of tailwater energy at hydropower plants. As a case study, extensive analyses are performed to determine the main features of the array of low-head turbines that are planned to be installed at the tailwater of the two main generators of Sanibey Dam. Sanibey Hydropower Plant is constructed on Seyhan River at Aladag region, Adana, Turkey. The plant has currently two Francis turbines (158.5 MW of each) with a total capacity of 317 MW. Tailwater can be briefly defined as the water leaving the main generators of the hydropower plant. Although most of its energy is converted to mechanical energy by rotating the blades of the turbine, it has still some energy which can be exploited by using low head run-of-river type turbines. Design and optimization of these secondary systems are nowadays among the popular research topics. This work investigates the feasibility of developing such a hydro-matrix structure consisting of an array of low-head small size turbines. Several analyses are performed to determine the optimum number and technical specifications of the generators. In this work, two different approaches aiming at maximizing the power output or minimizing the investment return period are utilized in the optimizations. Two year outflow statistics and hourly data of several operational parameters of the existing Francis turbines (provided by the operators of the dam) are analyzed to maximize the power output. Similarly, energy markets hourly price data is used for calculating the corresponding payback period and to minimize the return time of the investment. The results of the analyses obtained by using different design objectives are quite similar. The approach aiming at minimizing the payback period yields the optimal number of turbines as 27. The return time and the cost of the investment are 8.13 years and 4,940,310 USD, respectively. In power maximizing approach, the optimum number of turbines is calculated as 30. The return time and the cost of the investment are 8.15 years and 5,490,978 USD, respectively. The re-use of expensive raw material (water in this case) also results in approximately 6 % increase in the overall efficiency of the hydropower plant.