Thermodynamic analysis and multi-objective optimization of a novel power generation system driven by geothermal energy

Abstract

A novel combined system integrated with a Kalina and a transcritical CO2 (T-CO2) cycle is proposed and investigated for making effective use of geothermal resources. Geothermal energy is first utilized by Kalina sub-cycle and then deeply recovered by T-CO2 sub-cycle. A steady-state mathematical model is developed to further study the novel combined system. The result shows that under the given conditions, the system net power output is up to 2808 kW, which is higher than both the single Kalina cycle and single T-CO2 cycle. The exergy analysis shows that the evaporator II is the component with the largest exergy destruction. The parametric analysis shows that increasing the basic ammonia-water solution concentration and turbine I inlet temperature, or decreasing the turbine I inlet pressure and condensation pressure of condenser I have significant effects on system performance. Furthermore, a multi-objective optimization considering both thermodynamic and economic aspects is carried out to obtain the Pareto frontier solutions, and the decision-making analysis shows that the two-stage recycling system could greatly improve the geothermal water utilization degree compared to the conventional system. The findings could provide a useful reference for system design and operation to make better use of geothermal energy.