Off-design performance of a supercritical CO2 Brayton cycle integrated with a solar power tower system

This work focuses on the off-design performance of the system integrated a simple recuperative supercritical CO2 Brayton cycle, solar power tower, and thermal energy storage (TES). The system design parameters are obtained first; then, the off-design performance of power cycle and solar receiver are analyzed from the perspective of influencing factors; finally, the daily performance simulations of overall system are conducted. This work is aimed at analyzing the system performance under more realistic conditions, and clarifying the influence mechanism between parameters of solar field, TES and power cycle under off-design conditions. Results show that the increase in ambient temperature and input energy to the receiver, and the decrease in molten salt temperature from the cold tank are beneficial to improve the solar receiver efficiency. As the power demand deviates farther from design value, the temperature of molten salt at the heater outlet is higher, which leads to lower solar receiver efficiency. On the summer solstice, the system operates continuously for 24 h with 100% electricity powered by solar energy and 17.8% daily averaged solar-to-electricity efficiency. On the winter solstice, the system operates continuously for 17 h with 72.6% electricity powered by solar energy and 17.1% daily averaged solar-to-electricity efficiency. (C) 2020 Elsevier Ltd. All rights reserved.