Thermal energy storage uses widely differing technologies. Depending on the specific application, it allows for excess thermal energy to be stored for hours, days, or months at scales ranging from individual processes, buildings, multi user-buildings, districts, towns, to entire regions. Usage examples are the balancing of energy demand between day and night time, storing summer heat for winter heating, or winter cold for summer air conditioning (seasonal thermal energy storage). Storage media include water or ice-slurry tanks, masses of subsoil or bedrock accessed via borehole heat exchangers, deep aquifers contained between impermeable strata, lined pits with topside insulation and filled with gravel and water, as well as molten salts, phase-change materials, and thermochemical materials.
Other sources of thermal energy storage include heat or cold produced with heat pumps from off-peak, low cost electric power–a practice called peak shaving; heat from combined heat and power plants; heat produced from renewable electrical energy exceeding grid demand; and waste heat from industrial processes. Heat and cold storage, both seasonal and short term, is considered an important means for cheaply balancing high shares of fluctuating renewable electricity production and for the integration of the electricity and heating sectors in energy systems almost or completely fed with renewable energy.
Solid Matter Storages for Grid Stabilisation
Molten-Salt Storage for Demand-Oriented Power Supply
Latent Heat Storage for Process Steam Provision