A Theoretical Study on the Thermal Performance of an Increasing Pressure Endothermic Cycle for Geothermal Power Generation

Hao Yu, Xinli Lu (), Wei Zhang and Jiali Liu
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Hao Yu: Department of Energy and Power Engineering, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China
Xinli Lu: Department of Energy and Power Engineering, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China
Wei Zhang: Department of Energy and Power Engineering, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China
Jiali Liu: Department of Energy and Power Engineering, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China

Energies, 2024, vol. 17, issue 5, 1-24

Abstract: In this study, a power cycle (IPEC), with an increasing pressure endothermic process in a downhole heat exchanger (DHE) and a CO 2 -based working fluid mixture, was developed for geothermal power generation. The increasing pressure endothermic process, which cannot be achieved in a conventional evaporator on the ground, was realized using the gravitational potential energy in the DHE. The parameters of the power cycle and the structural size of the DHE were optimized simultaneously. Using CO 2 -R32 as the working fluid of the IPEC provides the highest net power output. The net power generated with the IPEC was compared with a single-flash (SF) system, a trans-critical CO 2 (t-CO 2 ) system, and an organic Rankine cycle (ORC) under the same heat source and sink conditions. Six selection maps were generated for choosing the optimum power cycle for electricity production, in which four power generation systems (ORC, t-CO 2 , IPEC, and SF) were included, and two DHE diameters (0.155 m and 0.22 m) were investigated. It was found that the IPEC system had more net power output than the other three systems (ORC, t-CO 2 , and SF) under the conditions that the geofluid’s mass flow rate was less than 10 kg/s and its temperature was lower than 180 °C.

Keywords: thermodynamic analysis; increasing pressure endothermic cycle; power generation; CO 2 -based mixtures; downhole heat exchanger (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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