Energy and exergy analyses of single flash geothermal power plant at optimum separator temperature

In this work, a thermodynamic analysis consisting of energy and exergy analyses is carried out to determine the performance of a single flash geothermal power plant. A new derivation for determination of the optimum separator temperature, which results in maximum turbine power output, is achieved. The energy and exergy analyses are carried out at that optimum separator temperature. The thermodynamic derivation showed that the separator would result in maximum performance of the power plant when it operates at the average value of the production well and condenser temperatures. Moreover, the derivation was numerically validated by calculating three different values for the geothermal well temperatures. The results show that the highest exergy destruction rate is in the expansion valve followed by the steam turbine, the mixing process and the pump. The separator has exactly zero exergy destruction rate while the condenser has almost zero exergy destruction rate. The results also show that the exergy destruction rate for all components of the power plant decreases with reduction in the geofluid temperature of the production well except for the condenser. The maximum energy efficiency of the power plant is about 12.5, 11 and 9.5% when the geofluid of the geothermal well temperature is 300, 275 and 250°C, respectively.