Operational Flexibility Assessment by Condensate Throttling Coupled With Thermal Storage Tanks on a 660 MW Supercritical Coal-Fired Power Plant

Abstract

Increasing the share of intermittent renewable energy sources in a power system poses challenges in terms of increased net load variability and maintaining grid stability and security. Operational flexibility of coal-fired power plants in China has played an essential and promising role in accommodating these nonequilibrium in the power grid. In the study, focusing on condensate throttling coupled with thermal storage tank measures, dynamic simulations of an entire 660 MW supercritical coal-fired power plant were developed via the GSE software. Then, the dynamic characteristics of main thermodynamic parameters and output power were described and compared, and operational flexibility performances of these measures were discussed. It turns out that: when condensate water flowrate decreases, the largest power ramp rate, power capacity, and energy capacity are 12.68 MW min−1, 12.76 MW, and 1084.70 MJ, respectively, and when condensate water flowrate 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 throttling without thermal storage tank measure is more suitable for power-up regulation than power-down regulation, but the shortest duration time is 130 s, which will restrict the operational flexibility regulation. However, coupling with thermal storage tanks, the deaerator water level can maintain a longer time. Meanwhile, at feedwater bypass 60% coupled with thermal storage tank, the largest power ramp rate, power capacity, and energy capacity are −3.62 MW min−1, −3.81 MW, and −897.31 MJ, respectively, and at condensate water bypass 60% coupled with thermal storage tank, the largest power ramp rate, power capacity, and energy capacity are 7.74 MW min−1, 7.88 MW, and 1829.38 MJ, respectively, and these parameter values are greater than condensate water flowrate directly increases or decreases 60%, which means condensate throttling coupling with thermal storage tanks can improve operational flexibility performances. The work is expected to reveal the performance parameters and strategies to provide detailed guidance of using turbine energy storage to improve operational flexibility of the coal-fired power plants.