Advanced exergy investigation of a combined cooling and power system with low-temperature geothermal heat as a prime mover for district cooling applications

Abstract

Present work deals with the conventional and advanced exergy analyses for an ammonia-water combined power and cooling cycle integrated with a low-temperature geothermal heat resource for district cooling applications. The energy and exergy calculation of the mentioned cycle was carried out by the Engineering Equation Solver (EES) software. The thermodynamic cycle method is used for advanced exergy analysis. The advanced exergy analysis by dividing the exergy destruction into the endogenous/exogenous and avoidable/unavoidable portions reveals the reducible exergy destruction part in each cycle element. Consequently, it determines the real improvement potential in the system. Results represented that the overall exergy efficiency with real and unavoidable conditions is 41.03% and 47.29%, respectively. It was found that from the 3681.2 kW of total exergy destruction for this cycle, about 941.5 kW (26% of total exergy destruction) can be mitigated by technology modification of components, where 75% is the endogenous avoidable, and 25% is related to the exogenous avoidable part. It also showed that the prioritizing of the components improving in terms of conventional and advanced exergy is different. The conventional exergy destruction presents the priority as the boiler, the absorber, the rectifier, the HER, the turbine, the RHE, and the pump. In contrast, the advanced exergy analysis’s suggested order is the turbine, the boiler, the rectifier, the HER, the absorber, the RHE, and the pump. They suggested that improving the Turbine and the boiler, and the rectifier is more efficient in increasing the system efficiency due to high endogenous avoidable exergy destruction.