Unlike other methods of storing solar heat, such as in water tanks or rock beds, containers for zeolites do not require insulation. Because of the relatively high cost of zeolites, however, zeolite heat storage is not yet available for residential use. We are unaware of more recent efforts. One application of zeolites in solar energy systems that was investigated is in cooling devices. Zeolites are placed inside a solar panel located on top of a compressor, a low-pressure water storage container, and a refrigerator compartment.
Sunlight dries the zeolites, which release water vapor.
The water vapor is then forced through the compressor. On its way down through the compressor to the underlying water storage container, the vapor cools and changes to a liquid. At night, the low pressure in the container causes some water to vaporize and return to the zeolites, bypassing the compressor. The zeolites bond with the water vapor, and release heat that radiates up through the collector and into the sky. The water remaining in the container freezes due to the loss of heat energy, which keeps the refrigerator compartment cold until the next cycle begins.