Control and Techno-Economic Analysis of Cross-Seasonal Thermal Energy Storage: A Multi-Scenario Assessment

Under the global energy transition and the decarbonisation of building heating, cross-seasonal thermal energy storage has emerged as a crucial technology to address the seasonal mismatch between renewable energy supply and demand. This study proposes and evaluates a modular composite thermal storage system that integrates thermochemical and phase change storage modulars. An intelligent control strategy is adopted to achieve functional decoupling and coordinated operation. Taking a residential district in Beijing, China, as a case study, three system scenarios are constructed: a full thermal storage system, a hybrid storage system supplemented with off-peak electricity, and a fully electric system. The results show that the hybrid system maintains the same annual solar energy utilisation as the full storage system while reducing the levelised cost of heat by 33%. The modular strategy reduces the scale of the storage system and enhances operational flexibility. Among the three scenarios, the hybrid system achieves the best balance in terms of storage efficiency, grid interaction, and cost-effectiveness. This study provides strategic insights and design references for the engineering application of cross-seasonal thermal storage systems, contributing positively to the decarbonisation of district heating.