Abstract
The storage of solar thermal energy has been a subject of extensive study for many years. Various storage concepts have been extensively investigated. However, little research has been done on energy storage in the heat-of- adsorption of chemical compounds. Zeolite is, perhaps, the only substance that has been studied for its heat-of- adsorption properties (1).
A recent proposal utilizes the hygroscopic properties of sodium sulfide for thermal storage (2). Sodium sulfide has a storage capacity of 3600 kJ per kilogram. The system is economically desirable as sodium sulfide costs a mere $0.27 per kilogram (3).
Experimental research has been continuing for a year on the feasibility of the system. The performance of the model has been reasonably close to the expected level. It is believed that further work can raise the storage temperatures to levels suitable for space heating and other low temperature ap plications. This system has two problems: 1) the salt has to be under vacuum, 2) the chemical odor in the vacuum pump exhaust.
A new conceptual design has been developed that eliminates the problem of odor and the need for a vacuum pump.
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