Energy optimization and gas removal selection of geothermal power plant

Abstract

Non-condensable gas (NCG) is a part of geothermal fluid that affects geothermal power plant performance. Two scenarios were proposed to extract NCG out of condenser; i.e two-stage steam jet ejector (SJE) intercondenser plus one-stage SJE after condenser (three-stage SJE) and hybrid (combination of two-stage SJE intercondenser and vacuum pump). Both scenarios were optimized by the installation of Variable Frequency Drive (VFD) to hot well pump and cooling tower fan, respectively. Each scenario was analyzed to the wet bulb temperature (WBT) fluctuation. This study modeled the data of Darajat Geothermal Power Plant unit III on load 100% (110 MW) and computed it using Engineering Equation Solver commercial version 9.430. The consideration of both scenarios was analyzed by Specific Steam Consumption net. The result of this study indicated that hybrid system can save 1.11% energy compared with three-stage SJE. It is also found that hybrid system had a possibility to optimize by VFD installation when WBT in 15.5 °C up to 19.5 °C. The highest energy saving was obtained 1.03% compared to constant L/G, on WBT 19.5 °C, where L/G denotes the ratio of inlet water mass flow rate to cooling air inside cooling tower.