Thermodynamic analysis and comparative investigation of a novel total flow and Kalina cycle coupled system for fluctuating geothermal energy utilization

Abstract

Geothermal energy is a sustainable energy source with no carbon footprint that has enormous potential for easing the climate change crisis. To improve geothermal energy conversion efficiency, a novel total flow and Kalina cycle (KC) coupled system that can overcome geothermal resource fluctuation to a certain extent is introduced. The total flow cycle is used to adapt to geothermal resource dryness fluctuations, and the KC can adapt to heat source temperature fluctuations by regulating ammonia concentrations. Mathematical models of this proposed system are established to compare its performance at both constant and variable ammonia concentrations. Simulation results show that a lower concentration is suitable for higher temperatures and leads to better system performance. The novel system adapts to a heat source with a certain dryness. When the geothermal water dryness is 0.1 and the temperature is 170 °C, the thermal and exergy efficiencies of the novel system can reach 12.84% and 38.91%, respectively, with the measure of regulating concentration. The comparative results indicate that the proposed system offers better performance than a basic KC system from both the first and second laws of thermodynamics, and the concentration regulation measure enhances the proposed system.