Thermodynamic analysis of a power and water combined system with geothermal energy utilization

A novel combined system, integrated with a flashing Ranking cycle and humidification dehumidification (HDH) desalination unit, is proposed to achieve the energy utilization from geothermal water. The flashed steam is used to generate power while the remaining water is applied to heat the seawater for water production. Based on the coupling relation between the power and desalination unit, conservation equations based on the thermodynamic laws are constituted. Energy and entropy analysis of the combined system are achieved for determining the power and water production. Furthermore, the influence principles from the spraying temperature and terminal temperature difference of the seawater heater on the overall performance of the combined system are also focused. The simulation results indicate that the maximal net power from the flashing Rankine cycle reaches 157.0 kW when the flashing temperature is 375.15 K. Due to the leading role to determine total efficiency of the combined system, maximum values of 711.85 kg h−1 for the water production and 43.98% for the total efficiency are obtained when the flashing temperature is 378.15 K. Furthermore, it is also obtained that a lower value both for the seawater spraying temperature and terminal temperature difference of the seawater heater can help to improve the performance of the combined system.