Thermoeconomic analysis of a CO2 plume geothermal and supercritical CO2 Brayton combined cycle using solar energy as auxiliary heat source

Abstract

Abstract: This study presents an investigation of a CO2 plume geothermal and supercritical CO2 Brayton (CPG-sCO2) combined cycle using solar energy as auxiliary heat source. This combined cycle may help solve the problems of CO2 sequestration and geothermal energy utilization simultaneously. The CPG production is heated by a solar power generation system with solar tower and molten salt. Then a recompression sCO2 cycle utilizes geothermal energy and solar energy directly. A solution procedure is performed to analyze the thermoeconomic performance of the CPG-sCO2 combined cycle. Results show that the combined cycle has an optimal main compressor inlet pressure and split ratio for maximum combined cycle efficiency. It can achieve 19.57% by genetic algorithm (GA) optimization, which is 5.65% and 4.07% higher than CPG systems with indirect sCO2 cycle and organic Rankine cycle, respectively. Moreover, it indicates that the combined cycle efficiency and total capital cost have opposite variation trends with the increase of parameters, including main compressor inlet pressure (p5), split ratio (sr), well distance (d8,11) and injection temperature (T8). Based on multi-objective GA optimization and optimal solution selection, it is concluded that the most thermoeconomic CPG-sCO2 combined cycle has a combined cycle efficiency of 18.09% and a total capital cost of $5.959 × 107, respectively. Findings suggest that the CPG-sCO2 combined cycle has potential to combine CO2 sequestration with geothermal energy utilization.