Performance study of solar tower aided supercritical CO2 coal-fired power generation system with different schemes

Abstract

Solar tower aided coal-fired system can obviously reduce coal consumption and CO2 emission, but there are few studies on integration system using supercritical CO2 (S-CO2) Brayton cycle. Therefore, in this paper, three new solar tower aided 300 MW S-CO2 coal-fired power generation systems with different integration schemes are proposed and their performances are studied and compared. In the schemes 1, 2, and 3, the solar energy is used to replace the partial heat loads of the low-temperature recuperator, the superheated surface, and the reheated surface, respectively. The results show that performances of new integration systems are significantly better than those of the traditional S-CO2 coal-fired power station in terms of standard coal consumption rate and CO2 emission rate. The standard coal consumption rates of schemes 1, 2, and 3 are reduced by 7.71 g/kWh, 9.95 g/kWh, and 10.54 g/kWh, respectively. Compared with the traditional S-CO2 coal-fired power station, the boiler exergy losses of new integration systems are obviously reduced, of which scheme 3 is reduced by 13.7 MW. After comprehensive consideration and comparison, the scheme 3 is the optimal system. In addition, influences of both the solar energy and operation load on the performances of scheme 3 are studied. The results show that under off-design conditions, the solar generating power, the solar field efficiency and the solar-to-electricity efficiency of scheme 3 increase with an increasing solar energy. Under the 100% load rate, when the solar energy increases by 1 MW, the solar generating power increases by about 0.35 MW on average. The proportion of power generation from solar energy increases with a decreasing operation load. When the solar energy is 40 MW, the proportions of power generation from solar energy at 100%, 75%, and 50% load rates are 3.44%, 4.52%, and 6.50%, respectively.