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research-article

A Study of S-CO2 Power Cycle for CSP Applications using an Isothermal Compressor

[+] Author and Article Information
Jin Young Heo

Korea Advanced Institute of Science and Technology, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
jyh9090@kaist.ac.kr

Jinsu Kwon

Korea Advanced Institute of Science and Technology, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
jinsukwon@kaist.ac.kr

Jeong Ik Lee

Korea Advanced Institute of Science and Technology, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
jeongiklee@kaist.ac.kr

1Corresponding author.

ASME doi:10.1115/1.4038476 History: Received August 10, 2017; Revised September 06, 2017

Abstract

For the concentrating solar power (CSP) applications, the supercritical carbon dioxide (s-CO2) power cycle is beneficial in many aspects, including high cycle efficiencies, reduced component sizing, and potential for the dry cooling option. More research is involved in improving this technology to realize the s-CO2 cycle as a candidate to replace the conventional power conversion systems for CSP applications. In this study, an isothermal compressor, a turbomachine which undergoes the compression process at constant temperature to minimize compression work, is applied to the s-CO2 power cycle layout. To investigate the cycle performance changes of adopting the novel technology, a framework for defining the efficiency of the isothermal compressor is revised and suggested. This study demonstrates how the compression work for the isothermal compressor is reduced, up to 50%, compared to that of the conventional compressor under varying compressor inlet conditions. Furthermore, the simple recuperated and recompression Brayton cycle layouts using s-CO2 as a working fluid are evaluated for the CSP applications. Results show that for compressor inlet temperatures (CIT) near the critical point, the recompression Brayton cycle using an isothermal compressor has 0.2-1.0% point higher cycle thermal efficiency compared to its reference cycle. For higher CIT values, the recompression cycle using an isothermal compressor can perform above 50% in thermal efficiency for a wider range of CIT than the reference cycle. Adopting an isothermal compressor in the s-CO2 layout can imply larger heat exchange area for the compressor which requires further development.

Copyright (c) 2017 by ASME
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