Coupled Analysis of Thermal Performance and Economics of the Insulated Floating Cover of Water Pit for Solar Seasonal Thermal Energy Storage

Abstract Water pit for solar seasonal thermal energy storage (WPTES) system can store and transfer the abundant solar energy in the nonheating season to the heating season, which is one of the important technical routes for solar energy to be used for clean heating in buildings. On the one hand, the superiority of the insulated floating cover (IFC) insulation performance of WPTES determines whether WPTES can form a stable thermal stratification phenomenon, and also determines the thermal storage performance of WPTES. On the other hand, the cost of IFC accounts for 40–60% of the cost of WPTES, and reasonable cost control is an important prerequisite for the optimal system design, engineering application, and widespread promotion. In this article, based on the TRNSYS simulation platform, the heat transfer model of IFC coupled with the thermal economic model of the system is used for multidimensional comprehensive analysis, and the comprehensive heat transfer coefficient of IFC, the heat loss of WPTES, the unit cost of IFC, the unit cost of WPTES, and the heat price including tax are used as the evaluation parameters to comprehensively analyze the thermal performance and economics of IFC. The correlation analyses revealed a J-type empirical correlation relationship between the thermal performance and economics of the IFC, where the thickness of the IFC should be considered first and then the thermal conductivity should be adjusted. The relevant research results have been applied in the second phase of the Huangdicheng project and will also provide reference for the optimal design and construction of IFCs and systems in other projects.