Developing Choices for Optimal Binary Power Plants in the Existing Geothermal Production Areas in Indonesia

Abstract

Generally, single flash technology is the first step of development, but this study focuses on the utilization of waste heat from existing geothermal power plants to generate electricity at lower temperatures. Binary cycle technology is considered with four different proposed designs to maximize the output. The risk of silica scaling is one of the design constraints under typical conditions in geothermal fields in Indonesia; reservoir temperature, enthalpy of wells and brine pressure are employed in optimization calculations. A binary unit that combines brine and condensate before reinjection will produce the highest power production, 46 kW per 1 kg/s of brine for certain conditions. By simulating 2 MWe of development for each design at a reservoir temperature of 250°C, well enthalpy of 1200 kJ/kg and brine pressure of 10 bar absolute, it was found that the cost would be about 4.56-5.55 M USD, and would require an electricity price of 6.39-7.62 US₵/kWh to achieve 16% IRR.