Annual performance of subcritical Rankine cycle coupled to an innovative particle receiver solar power plant

Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerged as the preferred commercial solution for solar thermal electricity in central receiver technology. Despite their ability to store large amounts of thermal energy and efficient receiver designs, further efficiency improvements are constrained by tight temperature restrictions when using molten salts (290 °C-565 °C). In this work, a novel heat transfer fluid based on a dense particle suspension (DPS) is used due to its excellent thermophysical properties that extend the operating temperature of solar receiver and allow its coupling with higher-efficiency power cycles. In this paper, the design of a DPS solar receiver working at 650 °C has been optimized for two commercial sizes (50 MWth and 290 MWth) coupled to an optimized subcritical Rankine cycle. The results showed that a five-extraction reheated Rankine cycle operating at 610 °C and 180 bar maximizes power plant efficiency when coupled with a DPS central receiver, giving 41% power block efficiency and 23% sun-to-electricity efficiency. For optimization purposes at design point conditions, in-house code programmed into MATLAB platform was used while TRNSYS software was employed for annual plant performance analysis.