Heat is one of the cheapest forms of energy to store. Insulated water tanks buffer hours and days. Pit thermal storage, giant insulated basins of water, and underground stores hold heat for months.
Danish solar district heating plants pair collector fields with seasonal pit storage, so summer sun heats homes in winter. Thermal storage connects seasonal renewable supply with winter demand in a way batteries cannot, and takes pressure off the electricity grid.
Three proven ways to store heat, from hours to whole seasons.
Water tanks
HOURS · DAYS
Insulated steel tanks buffer daily swings in buildings and networks.
Pit thermal storage
WEEKS · SEASONS
Giant insulated water basins store summer heat for winter district heating.
Underground storage
SEASONS
Boreholes and aquifers hold heat in the ground itself, at city scale.