Optimization of Olkaria II Geothermal Brine for a Proposed Binary Unit by Energy and Exergy Analysis

Abstract

The paper presents the best working fluid to optimize the geothermal resource of Olkaria complex geothermal field in Kenya. The reinjected brine at 156oC with 206 kg/s is used to model, design and optimize basic binary unit using Engineering Equation Solver (EES) code for different working fluids. System optimization defines the guidelines in selection of working fluid and the configuration of the power plant. The objective functions of the paper are to optimize the system to get the highest power output. The design is constrained by the available separator parameters, by application of the first and second laws of thermodynamics. The power generation output from Olkaria II unit will have additional power to supply to the national grid. For the different working fluids studied the least power that can generated is 3,794 kWe using R152a fluid with the highest being application of R600a, 6,792 kWe. Addition of power from renewable source will also reduce the effect of CO2 emissions. Energy and exergy analysis is a powerful tool in decision making in power plant designs.