Underground Thermal Energy Storage: Overview and Case Study in Scotland

Heating and cooling account for half of the UK's energy consumption, and only less than a tenth of this demand is met using renewable energy sources. For a net-zero carbon economy, heating and cooling must be further decarbonised. Underground thermal energy storage (UTES) can handle the temporal mismatch between heat supply and demand, e.g. solar heat supply in summer and heat demand in winter. In addition, waste heat from various sources can be stored underground for green ground-based heating. In this presentation, an overview of the various types of UTES is given with a special focus on borehole thermal energy storage (BTES), in which a network of boreholes tted with heat exchange pipes use the ground as a thermal storage medium. A case study on how solar energy can be seasonally stored for use in the summer is presented for a university building. In summer, solar-thermal collectors are used to full the heat demand of the building, and any surplus heat is directed to an underground BTES store. In winter, the stored heat is extracted to meet the building's heating needs. The system design, operation and capacity based on the building location are highlighted.