Thermodynamic analysis on the transient cycling of coal-fired power plants: Simulation study of a 660Â MW supercritical unit

The flexibility of coal-fired power plants must be improved to satisfy load fluctuations in power grids caused by the rapid spread of power generation capacity from unpredictable renewable energy sources. Startups, shutdowns and large amplitude load cycling have become normal operational states for coal-fired power plants in recent years. The extremely high thermal inertia of a power plant influences the energy consumption of the power plant in load fluctuation processes. To obtain the energy consumption characteristics of power units during transient cycling processes, dynamic models of a 660 MW supercritical unit were established with the GSE software. The heat storage and control systems of the unit were considered. The energy consumption of the power plant was obtained at different cycling rates and compared with the results calculated with steady-state models. Results show that compared with those obtained with steady-state models, the standard coal consumption rate (SCCR) of the power plant increased by 3.57 g (kW h)−1, which accounts for 1.3% of SCCR at most during the load-up process, and decreased by 2.96 g (kW h)−1, which accounts for 1.0% of SCCR at most during the load-down process. The average SCCRs of these dynamic and steady-state models differed when the load cycling rates were different. When the load varied between 50% THA and 75% THA, the maximum difference of standard coal consumption rate variation (SCCRV) were 1.2 and 0.26 g (kW h)−1 during the load-up and load-down transient processes, respectively. The maximum differences in SCCRV were 0.85 and 0.34 g (kW h)−1 during load-up and load-down transient processes, respectively, with the load ranging from 75% THA to 100% THA.