[en] Highlights: • An application of different power cycles coupled to a geothermal polygeneration plant is presented. • The polygeneration plant sequentially produces electricity, refrigeration and dehydrated products, using the cascade concept. • Power cycles considered as feasible are Goswami, Kalina and ORC. • Thermodynamic and economic performance was carried considering energy, exergy and economic indicators. • Among power cycles studied ORC cycle achieved better energy and economic performance. 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 system's 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.

[en] Highlights: • Cascade utilization of low- and mid-temperature geothermal energy is presented. • The system consists of three thermal levels producing power, ice and useful heat. • A techno-economic analysis is performed evaluating energy and economic benefits. • A simple optimization algorithm was developed to optimize system benefits. • Inconvenience of low thermal efficiency and high capital cost of ORC were overcome. - Abstract: The Organic Rankine Cycle (ORC) is a technology that has reached maturity in cogeneration or waste heat applications. However, due to low thermal efficiency and high capital cost of ORC machines, geothermal-based ORC applications represent only a small percent sharing of the geothermal power capacity worldwide. Several countries have reported a great potential of low- and mid-temperature geothermal energy, representing an opportunity to explore a more efficient ORC integration into non-conventional applications of geothermal energy. One alternative, resembling the polygeneration concept, is known as cascade utilization of geothermal energy, where different energy outputs or products can be obtained at the same time, while improving thermal and economic performance. In this paper, a techno-economic analysis for the selection of small capacity ORC machines and absorption chillers (for ice production), to be integrated into a polygeneration plant that makes use of geothermal energy in a cascade arrangement, is presented. A simple cascade system that consists of three sequential thermal levels, producing simultaneously power, ice and useful heat is proposed, considering typical temperatures of geothermal zones in Mexico. A simple optimization algorithm, based on energy and economic models, including binary variables and manufacturer’s data, was developed to evaluate and determine optimal ORC and absorption chiller units. Results show, firstly, that inconvenience of low thermal efficiency and high capital cost of ORC machines can be overcome. Secondly, that the temperature difference in ORC evaporator strongly influences the overall energy efficiency and the economic profit of the system.