Experimental verification of a high-parameter hot water storage tank for enhancing the load ramp-up capability of subcritical steam-generation system

The increasing penetration of renewable energy into power systems has placed greater demands on the load ramp-up capability and operational flexibility of coal-fired power plants. Coupling external thermal storage with coal-fired power units is a promising approach to meeting this requirement. In this study, a novel method for enhancing the load ramp-up capability of a subcritical steam-generation system with the assistance of high-parameter hot water was experimentally verified by integrating a high-parameter hot water storage tank into an existing pilot-scale molten salt-steam generation platform. Experiments were conducted under constant pressure to investigate the steady-state characteristics, heat storage behavior, and load ramp-up performance of the steam-generation system. The results show that the available molten-salt thermal input is an important operating factor governing the steam output under the present test conditions. The hot water storage process causes a short duration and recoverable transient disturbance. The first transient steam flow reductions are 3.8%, 5.3%, and 4.6%, while the larger reductions of 6.4%, 8.6%, and 5.0% represented the maximum fluctuations during the subsequent storage period. More importantly, the release of stored hot water effectively accelerates load ramp-up under the tested conditions, shortening the total ramp-up time by 8.4%–15.5% over different load intervals compared with standalone mode. The hot water release-assisted mode enhances the load ramp-up rate by 0.38% Q t /min, 1.19% Q t /min, 3.71% Q t /min, and 1.36% Q t /min in the 40–60%, 40–80%, 50–80%, and 80–100% load ranges, respectively. By directly introducing high-enthalpy hot water into the steam generator, the proposed method markedly improves the system's dynamic load ramp-up performance. These findings provide experimental evidence and theoretical support for the feasibility of using a high-parameter hot water storage tank to enhance the load ramp-up capacity of subcritical coal-fired power plants.