Prefeasibility design of a 2x25 MW single-flash geothermal power plant in Asal, Djibouti

Abstract

Geologically, the most active area in Djibouti is the Asal area. Six wells have been drilled with varying depths ranging from 1137 to 2105 m. The first two wells were drilled in 1975 and the other four between 1987 and 1988. Well Asal-2 was damaged. The temperature of the other wells ranges from 260 to 360°C. In spite of significant geothermal studies and deep drilling explorations conducted since 1970 on several geothermal prospect zones, geothermal energy in Djibouti has yet to be developed. However, the process of developing a new power plant, using the steam resources from the wells, is now underway. The main objectives of this paper are to make a prefeasibility design of a geothermal power plant with a total net output power of 2×25 MWe. The purpose of modelling and simulation is to observe the performance of the system when a number of parameters, such as wetbulb temperature and cooling water supply system, are changed. Also, the model provides a tool with which to determine the optimum and adequate pressure for the technical operation of the system and to optimise the electrical power production process. The simulation and technical analysis, using the EES program, has proven very useful for calculations, giving a turbine power output of 55.6 MWe and the power plant’s electrical consumption as approximately 7.2% of the power from the turbine.