Performance optimization and techno-economic analysis of a novel geothermal system

Abstract

A novel geothermal system that has high efficiency and economic benefits was proposed in this study. The proposed geothermal system includes an organic Rankine cycle, absorption refrigeration subsystem, and heating/hot water subsystem. The selection of working fluid, performance optimization, and techno-economic analysis of the geothermal system were conducted by establishing mathematical models. The thermodynamic performance was enhanced by using evaporators in series and the separation-flash process. And the thermodynamic performance of the proposed system was investigated with five working fluids. The ratio of mass flow rate, separate pressure, and flash pressure were optimized using the stepwise multi-objective optimization technology. The results show that R245fa was the optimal working fluid. The system can reach its optimal operating state when the ratio of mass flow rate is 2.5, separate pressure is 2500 kPa and flash pressure is 1000 kPa. The largest power generation, thermal efficiency, exergy efficiency, and the lowest irreversible loss of the optimized system are 962.5 kW, 13.64 %, 35.74 %, and 4248 kW, respectively. The techno-economic analysis shows that the total investment cost of the novel geothermal system is 8.173–9.132 million dollars, the annual revenue is 2.451–2.608 million dollars per year, and the static payback period is 3.134–3.726 years.