The rising penetration of variable renewable energy sources necessitates that conventional coal-fired power plants operate more frequently at partial loads to ensure grid stability. However, such operations can significantly reduce the efficiency of air pollution control units and exacerbate pollutant emissions. Understanding the exergoenvironmental performance of power plants under fluctuating load conditions is essential for the development of sustainable flexibility retrofit strategies. In this study, the exergoenvironmental performance of a 660 MW coal-fired plant is assessed at both 100% and 50% load conditions. At full load, the total environmental impact rate reached 42.38 mPts/kWh, with the most significant impact categories being global warming potential (34.16%), ozone formation potential (25.66%), and acidification potential (12.37%). Flue gas pollutants were the main contributors to the overall environmental impact, accounting for 63.86%, followed by exergy destruction (35.84%). At 50% load, the total environmental impact rate increased by 2.93 mPts/kWh. An increase by a factor of 1.6 was observed in global warming potential, while ozone formation potential rose by a factor of 1.4. Exergy destruction in the boiler, SCR unit, and air preheater increased by 1.36, 1.37, and 1.50 times, respectively. The boiler consistently exhibited the highest potential for minimizing environmental impacts, demonstrated by the highest relative difference ( r b ) under both load conditions. These findings underscore that low-load operations intensify environmental impacts, highlighting the necessity of integrating strategies for both pollution mitigation and exergy destruction reduction in the flexibility retrofitting of power plants.
Wu et al. (Sun,) studied this question.