Thermodynamic Performance of Molten Salt Heat Storage System Used for Regulating Load and Supplying High Temperature Steam in Coal-Fired Cogeneration Power Plants

Abstract

In order to accept more electricity from renewable energy, cogeneration power plants are considering to reduce electricity production, which affects the heat supply. Here we present a molten salt heat storage system for coal-fired cogeneration power plants, which can supply high temperature steam to users and decouple the heat and electricity production. The first and second law-based analytical models for the cycle and a real device are built. Two water input methods are taken into account. The results show that the high and low temperatures in the two molten salt tanks influence the design of the components and the entropy generation distribution significantly. The pinch temperature difference in the discharge duration limits the lowest molten salt temperature. The device with real heat exchangers produces higher entropy generation and lower second law efficiency. Environmental water input requires more heat and entropy generation for the same steam supply. Recommendations are provided for practical designs.