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Thermodynamic and economic investigation of a screw expander-based direct steam generation solar cascade Rankine cycle system using water as thermal storage fluid

Li, Jing; Li, Pengcheng; Gao, Guangtao; Pei, Gang; Su, Yuehong; Ji, Jie

Authors

Jing Li

Pengcheng Li

Guangtao Gao

Gang Pei

YUEHONG SU yuehong.su@nottingham.ac.uk
Associate Professor

Jie Ji



Abstract

Solar electricity generation system (SEGS) which employs cascade steam-organic Rankine cycle (SORC) and steam screw expander (SE) is promising due to the high efficiency at moderate heat source temperature. This paper puts a special emphasis on heat storage and thermo-economic evaluation. Preferable operating temperature of the system is first clarified on the basis of SE characteristics. The temperature-dependent permissible stress of steam accumulator is modelled and the capital cost is investigated. Comparison between the direct steam generation (DSG) SEGS and an indirect one using thermal oil is made at a power capacity of 1 MW and storage of 6.5 h. The results indicate the DSG system has both thermodynamic and economic superiorities. The hot side temperature (THTH) of SORC generally does not exceed 250 °C to achieve an optimum solar thermal power efficiency. Given radiation of 750 W/m2, the maximum efficiency (ηT,mηT,m) is 14.3% with a corresponding THTH around 240 °C. The material cost of pressure vessels is 2.55 million RMB. For the indirect system, the optimal THTH is about 230 °C and ηT,mηT,m approximates to 13.2% and the estimated oil cost is 7.92 million RMB. It is recommended to adopt steam accumulators in the SE-driven SEGS.

Journal Article Type Article
Publication Date Jun 1, 2017
Journal Applied Energy
Print ISSN 0306-2619
Electronic ISSN 0306-2619
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 195
APA6 Citation Li, J., Li, P., Gao, G., Pei, G., Su, Y., & Ji, J. (2017). Thermodynamic and economic investigation of a screw expander-based direct steam generation solar cascade Rankine cycle system using water as thermal storage fluid. Applied Energy, 195, https://doi.org/10.1016/j.apenergy.2017.03.033
DOI https://doi.org/10.1016/j.apenergy.2017.03.033
Keywords Solar thermal power generation; Screw expander; Thermal storage; Steam accumulator; Part-load behavior
Publisher URL http://www.sciencedirect.com/science/article/pii/S0306261917302568
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by-nc-nd/4.0

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by-nc-nd/4.0





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