Comparative technical and economic study of Hybrid Solar-Geothermal Power Plant in Ethiopia

This paper presents a techno-economic assessment of a hybrid solar-geothermal power plant that is modelled taking into account the available geothermal and solar energy resources at the Tendaho-1 (Dubti) geothermal field in Ethiopia. The hybrid power plant combines a single-flash geothermal power plant with a parabolic trough solar thermal plant to increase the energy level of geothermal steam. The geothermal fluid from one of the production wells at the geothermal site and the direct normal solar irradiance prevailing in the area offer the primary sources of energy used in the modelling. A thermodynamic analysis based on the principles of mass and energy conservation and a figure of merit analysis that allows evaluating the energy and economic performance of the hybrid power plant were performed. The technical and economic efficiency assessment was performed by comparing the performances of the hybrid power plant with a power system consisting of stand-alone geothermal and solar power plants. Results of the techno-economic assessment showed that for the same amount of energy inputs, depending on the available thermal energy storage capacity, a hybrid power plant generates up to 10.4% more electricity than a power system of two stand-alone power plants while generating a higher net present value at a lower cost of generation. In addition, the hybrid power plants with and without thermal storage system exhibit an economic figure of merit values of 2.62 and 3.42, i.e. the cost of solar resource per kWh of electricity in the hybrid energy system is reduced by 70.5% and 61.5%, respectively.