The main findings of the studies on closed adsorption storage, as reported by SPF in Switzerland, are the following:

• The geometrical parameters and the dynamical behaviour of the closed sorption system are strongly related. The available temperature depends on the pressure of the sorbate and the driving force is limited by the external temperature ranges — the low temperature energy source — the mid temperature source/sink and — the high temperature energy source, which is aimed to be a solar collector.

• The measured temperature behaviour as a function of time in the sorbent module and in the sorbate (water) tank is indicating an optimum cycle time in the range 3 to 8 min. The determined power output shows a higher system performance for cooling than for heating because of a higher heat transfer in the evaporation of the sorbate. Regarding the short cycle time and the higher power output for cooling, the adsorption process is more suitable for cooling application of a thermally driven heat pump. At this development level a scaling up to long term storage is doubtful.

• A further understanding of the sorption system will be needed for a maximum power design because it will be determined by the geometric dimension of the system i. e. particle distribution of the sorbent fixed bed in a defined solid sorbent — liquid sorbate material combination.

• In a comparison of the solid adsorption and a the liquid absorption processes the liquid system could be favoured for storage application — exactly because the fluid can be pumped from one storage tank through a reaction zone to an other storage tank.

• Thermal energy storage in a sorption storage system is depending on the available thermal energy sources and sinks. So, the selection of the sorbent — sorbate material combination has to be done under these general conditions, beside of others. With the idea of the reduction of moving parts i. e. pumps in a solid sorption system the power limiting low heat transfer coefficients are leading to a layer structure in the sorption module. But a layer structure applied to a heat exchanger will limit the energy output of the system.