Thermodynamics analysis of single-flash wellhead geothermal power plant at Jailolo field, Halmahera

Thermodynamics analysis of single-flash wellhead generator system was carried out for the early stage of the development of Jailolo geothermal field, Halmahera. The analysis was performed in the forms of energy, exergy and efficiency calculations. The single-flash wellhead generator system was adopted due to its some advantages over conventional plants such as 1) wellheads have short steam transmission lines and this will result in less losses and lower costs, 2) the energy is transmitted as electricity which is more efficient than transporting steam, 3) individual characteristics of well can be fully utilized by selecting the plant for the most optimum point on the output curve, 4) ease of maintenance with small individual plant that can be shut for maintenance, 5) cost effective and competitive. Analysis was conducted for Jailolo geothermal fluid with an estimated enthalpy of 1100 kJ/kg, wellhead temperature of 179oC, and steam fraction of 20% using Cycle Tempo 5.1 software. The results of calculations showed that the optimum wellhead pressure is 9.8 bar(g) and mass flow rate of 52.86 kg/s. The system produces 5086.76 kW for turbine power output, kW for generator power output, and 4368.16 kW for delivered net power. From the thermodynamics point of view, the single flash wellhead generator has 34.1% utilization efficiency obtained from exergy analysis.