Design of steam condensation temperature for an innovative solar thermal power generation system using cascade Rankine cycle and two-stage accumulators

Gao, Guangtao; Li, Jing; Li, Pengcheng; Cao, Jingyu; Pei, Gang; Dabwan, Yousef N.; Su, Yuehong

Abstract

An innovative solar thermal power generation system using cascade steam-organic Rankine cycle (SORC) and two-stage accumulators has recently been proposed. This system offers a significantly higher heat storage capacity than conventional direct steam generation (DSG) solar power plants. The steam condensation temperature (𝑇2) in the proposed system is a crucial parameter because it affects the SORC efficiency (𝜂𝑆𝑂𝑅𝐶) in normal operations and the power conversion of the bottoming organic Rankine cycle (ORC) in the unique heat discharge process. The present study develops a methodology for the design of 𝑇2 with respect to a new indicator, that is, the equivalent heat-to-power efficiency (𝜂𝑒𝑞). 𝜂𝑒𝑞 is a compromise between the efficiencies in different operation modes. The effects of main steam temperature (𝑇1), Baumann factor (a), mass of storage water (𝑀𝑤), and ORC working fluid on 𝑇2 are investigated. Results show that𝜂𝑒𝑞 is a better indicator than 𝜂𝑆𝑂𝑅𝐶. The optimum steam condensation temperature (𝑇2,𝑜𝑝𝑡) that corresponds to the maximum 𝜂𝑒𝑞 (𝜂𝑒𝑞,𝑚𝑎𝑥) is generally higher than that based on the maximum 𝜂𝑆𝑂𝑅𝐶. 𝑇2,𝑜𝑝𝑡 reduces as 𝑇1, a, and 𝑀𝑤 decrease.𝜂𝑒𝑞,𝑚𝑎𝑥 rises with the increment of 𝑇1 and the decrement of a and𝑀𝑤. Pentane is a more preferable ORC fluid than benzene and R245fa. The 𝑇2,𝑜𝑝𝑡 and 𝜂𝑒𝑞,𝑚𝑎𝑥 of pentane are, respectively, 139-190 °C and 20.93%-24.24%,provided that 𝑇1 ranges between 250°C and 270°C, a varies from 0.5 to 1.5,and 𝑀𝑤 changes from 500 ton to 1500 ton.

Citation

Gao, G., Li, J., Li, P., Cao, J., Pei, G., Dabwan, Y. N., & Su, Y. (2019). Design of steam condensation temperature for an innovative solar thermal power generation system using cascade Rankine cycle and two-stage accumulators. Energy Conversion and Management, 184, 389-401. https://doi.org/10.1016/j.enconman.2019.01.067

• Journal Article Type: Article
• Acceptance Date: Jan 11, 2019
• Online Publication Date: Feb 5, 2019
• Publication Date: Mar 15, 2019
• Deposit Date: Feb 13, 2019
• Publicly Available Date: Feb 13, 2019
• Journal: Energy Conversion and Management
• Print ISSN: 0196-8904
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 184
• Pages: 389-401
• DOI: https://doi.org/10.1016/j.enconman.2019.01.067
• Keywords: Fuel Technology; Renewable Energy, Sustainability and the Environment; Energy Engineering and Power Technology; Nuclear Energy and Engineering
• Public URL: https://nottingham-repository.worktribe.com/output/1545750
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0196890419301190