Design and performance analysis of deep peak shaving scheme for thermal power units based on high-temperature molten salt heat storage system

Abstract

The transition to renewable energy production is imperative for achieving the low-carbon goal. However, the current lack of peak shaving capacity and poor flexibility of coal-fired units hinders the large-scale consumption of renewable energy. This study takes a 670 MW coal-fired unit as the research object and proposes eight design schemes for molten salt heat storage auxiliary peak shaving system. And through simulation calculations using Ebsilon software, the thermal performance, peak shaving capacity, environmental performance, and investment cost of each scheme were compared and analyzed. The results show that the molten salt heat storage auxiliary peak shaving system improves the flexibility of coal-fired units and can effectively regulate unit output; The combination of high-temperature molten salt and low-temperature molten salt heat storage effectively overcomes the problem of limited working temperature of a single type of molten salt, and can further improve the peak shaving capacity of coal-fired units, and the overall efficiency of operation is not low; Choosing LiNaK carbonates as high parameter molten salt and Hitec as low parameter molten salt has greatly expanded the operating range of the unit; Upgrading the combined molten salt solution with the existing low pressure cylinder zero output pipeline of the power plant can further improve the thermal performance, peak shaving performance, and environmental performance of the thermal power molten salt coupling system, with a peak shaving depth of up to 90.2 %; Combined with the zero output technology of low-pressure cylinder, when heat storage, the intermediate pressure cylinder exhaust steam extraction and electric heater heating molten salt. When releasing heat, use combined molten salt to heat bypass water supply. During heat release, a combination of molten salt is used to heat the bypass water supply. This scheme is the best flexible peak shaving transformation plan for the unit studied in this article, which can recover the initial investment within five years and meet the requirements of technical transformation difficulty.