Advances in solar thermal power plants based on pressurised central receivers and supercritical power cycles

• Published in: Energy conversion and management Vol. 293; p. 117454
• Main Authors: Montes, M.J., Guedez, R., Linares, J.I., Reyes-Belmonte, M.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2023
• Subjects: Microchannel receiver; Pressurised gas; Radial configuration; Solar thermal power plant; Supercritical fluid; Supercritical power cycle; Supercritical fluid; Solar thermal power plant; Microchannel receiver; Radial configuration; Supercritical power cycle; Pressurised gas
• ISSN: 0196-8904; 1879-2227; 1879-2227
• DOI: 10.1016/j.enconman.2023.117454

•A comparative thermo-economic study of different STPP configurations is presented.•Each STPP consists of a supercritical CO2 cycle coupled to a central receiver system.•The working fluid in the solar receiver is a pressurised gas or a supercritical fluid.•The preferred working fluid in the receiver is CO2, due to its thermal properties.•There is an optimum fluid pressure that maximises the solar subsystem efficiency. This work addresses the comparative thermo-economic study of different configurations of solar thermal power plants, based on supercritical power cycles and pressurised central receiver systems. For all the cases examined, two innovations are introduced in the solar subsystem, compared to other similar studies. Firstly, the heat transfer fluid in the receiver is either a pressurised gas or a supercritical fluid. Secondly, the receiver is composed of compact structures performing as absorber panels, arranged in a radial configuration. The investigation considers different supercritical CO2 recompression cycles of 50 MWe, including a novel proposal of a directly coupled cycle with heat input downstream of the turbine. Furthermore, the study evaluates different heat transfer fluids in the receiver, specifically CO2, N2, and He, concluding that the former is preferred due to its better thermal performance. The main results show that an increase in the receiver inlet pressure yields to a reduction in its size, favouring the thermal efficiency but penalising the optical efficiency of the solar field. Therefore, optimal working pressures may exist for each configuration, depending on the operating temperature. When comparing the optimal configurations, it is observed that the plant based on the intercooling cycle demonstrates the highest overall efficiency, reaching 32.05%. At last, an economic analysis is conducted to assess the viability of the identified optimal configurations. In this regard, the plant based on the partial-cooling cycle exhibits the lowest levelised cost of electricity at 0.15 $/kWh. This is primarily due to its lower investment cost. The innovative directly coupled cycle follows closely with a cost of 0.17 $/kWh, driven by its high electricity production resulting from its low self-consumption.