Seasonal thermal energy storage

Seasonal thermal energy storage (or STES) is the storage of heat or cold for periods of up to several months. The thermal energy can be collected whenever it is available and be used whenever needed, such as in the opposing season. For example, heat from solar collectors or waste heat from air conditioning equipment can be gathered in hot months for space heating use when needed, including during winter months. Waste heat from industrial process can similarly be stored and be used much later. Or the natural cold of winter air can be stored for summertime air conditioning. STES stores can serve district heating systems, as well as single buildings or complexes. Among seasonal storages used for heating, the design peak annual temperatures generally are in the range of 27 to 80 °C (81 to 180 °F), and the temperature difference occurring in the storage over the course of a year can be several tens of degrees. Some systems use a heat pump to help charge and discharge the storage during part or all of the cycle. For cooling applications, often only circulation pumps are used. A less common term for STES technologies is interseasonal thermal energy storage

Examples for district heating include Drake Landing Solar Community where ground storage provides 97% of yearly consumption without heat pumps, and Danish pond storage with boosting.

There are several types of STES technology, covering a range of applications from single small buildings to community district heating networks. Generally, efficiency increases and the specific construction cost decreases with size.

The International Energy Agency's Energy Conservation through Energy Storage (ECES) Programme has held triennial global energy conferences since 1981. The conferences originally focused exclusively on STES, but now that those technologies are mature other topics such as phase change materials (PCM) and electrical energy storage are also being covered. Since 1985 each conference has had "stock" (for storage) at the end of its name; e.g. EcoStock, ThermaStock. They are held at various locations around the world. Most recent were InnoStock 2012 (the 12th International Conference on Thermal Energy Storage) in Lleida, Spain and GreenStock 2015 in Beijing. EnerStock 2018 will be held in Adana, Turkey in April 2018.

The IEA-ECES programme continues the work of the earlier International Council for Thermal Energy Storage which from 1978 to 1990 had a quarterly newsletter and was initially sponsored by the U.S. Department of Energy. The newsletter was initially called ATES Newsletter, and after BTES became a feasible technology it was changed to STES Newsletter.

...
Wikipedia