Comprehensive assessment of the efficiency of using latent heat thermal energy storage in the heat circuit of nuclear power plants with water-cooled reactors

Under modern system and market conditions, it is necessary to ensure the operation of NPPs under variable electric load schedules, enhancing their competitiveness in the electricity and capacity market. Given the expected growth of the share of NPPs in the generating capacity structure, the approaches that enable not only efficient operation of the nuclear power unit in load-following mode but also improvement of its operational safety become especially relevant. This article presents an integration layout developed by the authors for incorporating a latent heat thermal energy storage system with an additional steam turbine into the NPP power unit. The proposed circuit arrangement enables expansion of the station's load regulation range, while the additional wet-steam turbine provides backup power supply for the station's auxiliary systems in the event of a loss of external power supply. The aim of this article is to investigate the impact of combining an NPP power unit with a thermal energy storage system based on latent heat thermal energy storage and an additional turbine on the station's efficiency. A critically important indicator of economic efficiency determining the competitiveness of an NPP is the specific cost of the electricity it supplies. This article presents a comparison of electricity costs for a nuclear power plant unit under various operational scenarios: in nominal mode; with forced nighttime load reduction; and in combination with a thermal energy storage system. Taking into account the achieved effects from enhanced safety at the NPP, integration with a thermal energy storage system allows a reduction in the electricity cost from the nuclear power plant unit, while simultaneously enabling nighttime load reduction and covering semi-peak loads in the power system. It was found that integrating an additional steam turbine and LHTES into a nuclear power plant power unit reduces the Specific electricity cost by an average of 3%. When the benefits associated with the enhanced operational safety provided by the additional steam turbine are also considered, the reduction approaches 5%. The integration of LHTES enables nuclear power plants to participate in meeting daily fluctuations in electricity demand and to operate flexibly over a power range of 72% to 110% while maintaining the reactor at its rated thermal power. This operating strategy partially displaces fossil fuel-based generation, thereby reducing CO 2 emissions by up to 280 t per year.