The aim of seasonal storages in buildings is to store the surplus of heat from summer to cover the lack of heat in winter. With a nearly loss-free seasonal storage, it is possible to increase the share of solar thermal energy for space heating and domestic hot water up to 100%. The big advantage of sorption storages is the up to three times higher energy density of the sorption material compared to conventional water storages. In addition there are no losses during the storing period, whereas with water storages considerable heat losses to the ambient occur. Compared to large water stores, the system size (collector area and storage volume) can be greatly reduced to obtain the same or even an improved thermal performance.
Example of an experimental solar seasonal thermal storage system for a house, using zeolite in a closed sorption system. (AEE INTEC)
The solar fraction of water storage systems (black dotted lines) as function of the collector area and the type of solar collectors applied. The coloured lines are the solar fractions for a sorption storage system of the same volume. (COMTES project)