Power-to-Heat and Seasonal Thermal Energy Storage: Pathways Toward a Low-Carbon Future for District Heating

Power-to-Heat and Seasonal Thermal Energy Storage are emerging technologies that facilitate the integration of variable renewable energy sources into building and district energy systems. This review synthesizes recent advancements in technologies, integration strategies, and case studies, with a particular focus on nearly zero-energy buildings and nearly zero-energy districts. A structured literature survey, prioritizing sources from 2020 to 2025, was conducted to map available options. The analysis includes Power-to-Heat systems, primarily electric boilers and heat pumps, as well as various seasonal thermal energy storage configurations, including Aquifer Thermal Energy Storage, Borehole Thermal Energy Storage, Pit Thermal Energy Storage, Tank Thermal Energy Storage, and Packed Bed Thermal Energy Storage. The findings indicate that coupling renewable energy with Power-to-Heat and seasonal thermal energy storage can significantly enhance the flexibility of buildings and district systems, reducing the curtailment of renewable sources by utilizing surplus electricity from renewable generation, particularly during periods of low demand, and lowering the environmental impact of buildings and district heating networks.