Analyses of Thermal Performance of Solar Power Tower Station Based on a Supercritical CO₂ Brayton Cycle

Concentrating solar power (CSP) technology, possessing an inherent capacity to couple with energy storage ideally, attracts a great deal of attention nowadays. However, these power plants with various types of CSP system still cannot compete with the traditional thermal power plants in terms of levelized cost of electricity (LCOE), and their potential for utilizing clear and renewable solar energy cannot be overestimated. To improve the total efficiency of the solar power tower (SPT) plant is the key factor for its development. In this present paper, a SPT plant based on an S-CO₂ Brayton cycle (with S-CO₂ serving as heat transfer and working fluid) is proposed. A numerical simulation is carried out to calculate the effects of key operating parameters, including power cycle and subsystem parameters, on the overall performance of the SPT plant. The results show that there is an optimum value for the compression ratio for the SPT plant. For the heat receiver, the trends of exergy and thermal efficiency varying with turbine inlet temperature are reversed, because of the significant energy loss caused by high temperature of the surface of the heat receiver. As for the overall performance, the SPT plant proposed in this paper is better than other SPT plants based on a steam Rankine system and an S-CO₂ Brayton system with molten salt serving as heat transfer fluid (HTF) operating under the similar condition. Its overall thermal efficiency is 1.04% and 3.42% higher than that of two other SPT plants, respectively.