Design and performance evaluation of a new steam/water hybrid thermal energy storage system integrated within a coal-fired power plant
Dao Zhou, Ming Liu, Zhenzhen Wang, Yu Fu, Kezhen Zhang, Junjie Yan
Abstract
Enhancing the operational flexibility of coal-fired power plants (CFPPs) represents an effective approach to accommodate the high penetration of renewable power within the power grid. The integration of thermal energy storage (TES) system, which can achieve boiler-turbine decoupling substantially, is a potential way to enhance operational flexibility of coal-fired power plants. Direct storage of working fluids (steam and water) within coal-fired power plants may serve as a cost-effective solution. This study proposes a new coal-fired power plant configuration incorporating both steam accumulator (SA) and hot water storage tank for steam/water hybrid storage. The energy efficiency of the thermal energy storage system and flexibility enhancement of coal-fired power plants under different peak-shaving requirement are systematically investigated and compared with the integration of water storage tank or not. Results demonstrate superior energy efficiency and enhanced economic performance under non-maximum storage power through supplementary water storage tank implementation. The integrated TES system reduces the minimum electrical load from 30 % to 12.15 % of rated capacity. At the maximum storage power, the equivalent round-trip efficiency reaches 70.47 %, increasing to 82.24 % under reduced power operation. The total capital cost of the TES system amounts to 2.81 million USD, achieving a minimum equivalent levelized cost of electricity of 104.45 USD per megawatt-hour.