Guidelines for Optimal Selection of Subcritical Low-Temperature Geothermal Organic Rankine Cycle Configuration Considering Reinjection Temperature Limits

Chao Zhang, Jinglun Fu, Pengfei Yuan and Jianjun Liu
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Chao Zhang: Institute of Engineering Thermodynamics, Chinese Academy of Sciences, Beijing 100190, China
Jinglun Fu: Institute of Engineering Thermodynamics, Chinese Academy of Sciences, Beijing 100190, China
Pengfei Yuan: Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, Tianjin 300384, China
Jianjun Liu: Institute of Engineering Thermodynamics, Chinese Academy of Sciences, Beijing 100190, China

Energies, 2018, vol. 11, issue 11, 1-18

Abstract: General guidelines are proposed to select the optimal subcritical organic Rankine cycle configuration considering reinjection temperature limits for a low-temperature geothermal brine power plant. Saturated/superheated, non-regenerative/regenerative cycles are investigated. Evaporating temperature and overheating degree at the turbine inlet are selected as design variables, and highest plant exergy efficiency is pursued for current optimizations. Through theoretical analysis of mathematical modelling and typical case studies, a simple optimization approach is presented. The new approach consists of up to three judgements on reinjection temperature and evaporating temperature in comparison two optimization calculations along the saturated line and along the given reinjection temperature line. The potential optimal cycle configurations are saturated non-regenerative cycle, saturated regenerative cycle and superheated regenerative cycle. Then, this new optimization approach is applied to obtain optimal cycle configuration and relevant working condition. The working fluids investigated are R245fa, R1234ze(Z), isopentane, and isobutane. The saturated non-regenerative cycle is the optimal cycle when the reinjection temperature limit is equal or less than the optimal reinjection temperature with no reinjection constraint. Otherwise, the reinjection temperature limit influences not only the optimal cycle configuration but also the optimal working condition. Working fluid isobutane always achieves highest plant exergy efficiency for optimal cycles with either reinjection temperature limit.

Keywords: geothermal power plant; organic Rankine cycle; saturated cycle; regenerative cycle; plant exergy efficiency (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: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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