Thermoeconomic Optimization of Geothermal Flash Steam Power Plants

Abstract

Flash steam power plants are relatively a common method used to convert the geothermal energy into electricity when production wells produce a mixture of steam and liquid in a geothermal system. In comparison to the single flash system, the double flash steam power plant generates more power from geothermal fluid at the same conditions. However, electricity generation costs are higher for double flash plants. A thermoeconomic optimization model is presented in this paper as the generation costs of single and double flash steam power plants. By considering the pressures in the separator and flash vessel (only in a double flash plant) as the independent variables in the objective function and using numerical search methods (Golden Ratio and Nelder-Mead ), the minimum power generation cost was calculated at different geofluid conditions for either single or double flash steam power plants.
The analysis was carried out for plant sizes from 5 to 150 MW. The economy of scale was taken into account for Investment costs and Operation & Maintenance costs. The results for minimum generation cost and net power output using single and double flash geothermal power plants is presented for different geofluid temperatures and flow rates.