Seasonal Heat Storage

Solar thermal technology is the largest potential supplier of renewable heat for the built environment, which has the largest heating demand of all energy consuming sectors. State of the art solar thermal systems for combined hot water generation and space heating cover between 15% and 40% of the heat demand, be it for small domestic systems or for larger, solar assisted district heating systems.

This solar fraction can only be substantially increased if new storage systems are developed that can efficiently store heat over the seasons. The necessary storage volume needed for a single family house with very high energy efficiency is 120 m³ for a sensible heat storage, 60 m³ for a latent and 12 m³ for a chemical heat storage.

Heat consumption and solar irradiation over the year

For most regions in the world, solar thermal technology has the potential to provide 100% of the heating and DHW demand in buildings, provided that heat can be stored over the season.

A large part of the potential can be filled in with already existing sensible heat storage, mostly in combination with heat pumps. These water-based systems are more profitable when they are very large, supplying storage for a large number of houses or for a district.

For a more decentralised demand of heat, compact solutions need to be found, needing less volume for energy storage and thermal insulation.

Necessary storage volume for sensible, latent and chemical heat storage in a single family house.