Abstract

AMBRIZ-DIAZ, Víctor M.; RUBIO-MAYA, Carlos; PACHECO-IBARRA, J. Jesús  and  PASTOR-MARTINEZ, Edgar. Conventional exergy analysis applied to a polygeneration plant operating in a geothermal cascade. Ing. invest. y tecnol. [online]. 2019, vol.20, n.3, e035.  Epub Oct 15, 2019. ISSN 2594-0732.  https://doi.org/10.22201/fi.25940732e.2019.20n3.035.

In this work a conventional exergy analysis applied to a polygeneration plant that uses geothermal energy to produce electricity, cooling and useful heat for dehydration is presented. The polygeneration plant operates using medium enthalpy geothermal energy and is composed by several energy conversion technologies that operate with three thermal levels in a geothermal cascade. The first thermal level includes an Organic Rankine Cycle (ORC) for electricity production. The second thermal level has an absorption refrigeration machine for preservation of agricultural products at a low temperature as well as to maintain more stable the condensation temperature of the ORC. The thermal energy of the last level of the geothermal cascade feeds a dehydrator module. To determine the energy performance of the system, the polygeneration plant was subjected to a conventional exergy analysis calculating the exergy destroyed in each component and the entire plant. The plant was modeled working under realistic, unavoidable and ideal operating parameters to obtain the thermodynamic behavior under different efficiency criteria. The results show that the polygeneration plant operating under real conditions presents the greatest destruction of exergy (127. 7 kW), the lowest exergy efficiency (26.9%), and the lowest production of energy products. The results also show that taking into account the unavoidable conditions, the performance of the plant increases up to an exergy efficiency of 29.75%. Finally, the polygeneration plant has an exergy efficiency limit of 73%, which corresponds to the operation under ideal conditions. The values obtained in this study are of vital importance since they provide information for proposing improvements individually in components and in the plant as a whole.

Keywords : Conventional exergy analysis; polygeneration plant; geothermal cascade; multi-generation.

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