Operational flexibility assessment by condensate throttling coupled with thermal storage tanks on a 660 MW supercritical coal-fired power plant

Increasing the share of intermittent renewable energysources in a power system poses challenges in terms ofincreased net load variability and maintaining grid stability andsecurity. Operational flexibility of coal-fired power plants inChina has played an essential and promising role inaccommodating these nonequilibrium in the power grid. In thestudy, focusing on condensate throttling coupled with thermalstorage tank measures, dynamic simulations of an entire 660MW supercritical coal-fired power plant were developed via theGSE software. Then, the dynamic characteristics of mainthermodynamic parameters and output power were describedand compared, and operational flexibility performances of thesemeasures were discussed. It turns out that: when condensatewater flowrate decreases, the largest power ramp rate, powercapacity, and energy capacity are 12.68 MW min-1, 12.76 MW,and 1084.70 MJ, respectively, and when condensate waterflowrate increases, the largest power ramp rate, power capacity,and energy capacity are-5.49 MW min-1,-5.65 MW, and-695.94 MJ, respectively, which means condensate throttlingwithout thermal storage tank measure is more suitable forpower-up regulation than power-down regulation, but theshortest duration time is 130 s, which will restrict theoperational flexibility regulation. However, coupling withthermal storage tanks, the deaerator water level can maintain alonger time. Meanwhile, at feedwater bypass 60% coupled withthermal storage tank, the largest power ramp rate, powercapacity, and energy capacity are-3.62 MW min-1,-3.81 MW,and-897.31 MJ, respectively, and at condensate water bypass60% coupled with thermal storage tank, the largest power ramprate, power capacity, and energy capacity are 7.74 MW min-1,7.88 MW, and 1829.38 MJ, respectively, and these parametervalues are greater than condensate water flowrate directlyincreases or decreases 60%, which means condensate throttlingcoupling with thermal storage tanks can improve operationalflexibility performances. The work is expected to reveal theperformance parameters and strategies to provide detailedguidance of using turbine energy storage to improve operationalflexibility of the coal-fired power plants.