The main findings of the studies on closed adsorption storage, as reported by AEE INTEC in Austria, are the following:

• A sorption heat store with the material pair silica gel and water was developed, the system was scaled up for use in a single-family house and a first pilot plant was built.

• In this project, it could be shown for the first time that sorption technology for heat storage is technically feasible in a live test. The system concept, as well as the control strategy, have been proven to be functional under real operating conditions.

• The operation of the system was satisfactory and the system concept could be implemented in further systems. It has been shown that sorption storage with the used material combination is technically feasible. However, the temperature lift that can be achieved is only technically useful in a relatively small range of water contents. As long as the silica gel is very dry, the temperature lift

is sufficient. But starting at a water content of approximately 13%, the temperature lift is not large enough to compensate for higher losses in heat exchangers, pipes and tanks. That means that the energy density of the material that can be used in a real application is much smaller than both the theoretical one and what has been measured under laboratory conditions. Therefore, a large quantity of material would be necessary which makes sense neither technically nor economically.

• The used material has been chosen because it is manufactured in mass production and therefore inexpensive. Up to now, there are very few research institutes that develop sorption material specifically for heat storage. In most cases, the focus is on heat pumps, cooling machines or gas separation and drying processes. Singular projects have shown that the development of sorption materials for heat storage is technically feasible. So far, these materials have been expensive or for example corrosive.

• A TRNSYS model for the sorption store including the evaporator/condenser heat exchanger has been developed and a TRNSYS deck has been set up for the Task 32 reference conditions.

• For the simulations reported in report B6, a different sorption material has been used to show the possibilities of the store/system concept. The system concept was similar to the one used in the field test system which was using the sorption store only for space heating and not for domestic hot water preparation. This was done because of the low temperature lift of the material pair silica gel / water. The temperature lift of the material chosen for the simulations is much higher. Therefore, domestic hot water preparation would be feasible. But in the simulations, the solar fraction was limited to a value below 100% even for very large storage volumes because of the mentioned system design.