Thermodynamic performance and economic feasibility of Kalina, Goswami and Organic Rankine Cycles coupled to a polygeneration plant using geothermal energy of low-grade temperature

Abstract

Low-temperature geothermal energy is an abundant and renewable resource, but with technical and economic limitations for the generation of electricity. Currently, the polygeneration systems are an alternative for effective use of energy resources, geothermal energy included. In this paper a comparative analysis of the thermodynamic and economic performance of Kalina (KAC), Goswami (GOC) and Organic Rankine (ORC) cycles coupled to a polygeneration plant that uses geothermal energy of low-grade temperature to produce electricity, refrigeration and dehydrated products, simultaneously, is presented. It is proposed that the system design operates sequentially at different thermic levels under the concept of cascade utilization. The KAC, GOC and ORC cycles are analyzed as candidates for electricity generation, placed in a first thermal level. In a second thermal level, a cooling technology activated with thermal energy for fresh product conservation is included. Finally, a fresh product dehydrator is included in the last thermal level. To carry out the analysis, a standard structure has been proposed, to which the laws of mass and energy conservation apply. In addition, an exergy analysis is performed to know the performance of the system from the perspective of the second law of thermodynamics. The results indicate that the KAC and ORC cycles are more flexible to integrate, since the systeḿs products can adjust to the predefined needs. However, a better energy and exergetic efficiency of the polygeneration plant is obtained with the ORC, having 30.68 and 27.43%, respectively. From economic perspective the ORC has also the lowest Simple Payback Period (3.36 years) and the highest NPV (1.684 × 106 USD) among power cycles studied.