Thermodynamic analysis of a geothermal-solar flash-binary hybrid power generation system

In order to achieve efficient utilization of geothermal and solar energies, a new geothermal-solar hybrid power generation system with flash-binary configuration is proposed in this work. This system consists of a solar preheating subsystem, a flash binary power subsystem, and a binary power subsystem. The thermodynamic performances investigation of the hybrid system is implemented, under the designate condition with the geothermal water temperature and solar collection temperature of 170 degrees C and 390 degrees C, respectively, the net power output of the hybrid system is 12.76 MW. In the hybrid system, the proportion of solar energy input is 69.95%, the system energy efficiency and exergy efficiency reach to 10.74% and 23.9%, respectively. The maximum exergy loss is generated within the solar collection process and accounts for 33.27% of system total exergy loss. Additionally, the sensitivity analysis of main operation parameters (i.e., the flash pressure and the evaporation pressure, pinch point temperature difference and superheat degree in organic Rankine cycle) are carried out, the results indicate that the thermodynamic performances of system improved with the increase of flash pressure. In addition, the net power output and energy efficiency can increase to the maximum value at the evaporation pressure of 1.5 MPa. Through the system evaluation, the proposed geothermal-solar hybrid power generation system achieves favorable thermodynamic performances, and it provides an alternative way to improve the energy conversion efficiencies of the geothermal and solar energy. (C) 2019 The Authors. Published by Elsevier Ltd.