Molten Salt Thermal Energy Storage Systems:Salt Selection.

摘要

A research program aimed at the development of a molten salt thermal energy storage system commenced in June 1976. This topical report describes Work performed under Task I:Salt Selection is described. A total of 31inorganic salts and salt mixtures,including 9alkali and alkaline earth carbonate mixtures,were evaluated for their suitability as heat-of-fusion thermal energy storage materials at temperatures of 850to 1000exp 0 F. Thermophysical properties,safety hazards,corrosion,and cost of these salts were compared on a common basis. We concluded that because alkali carbonate mixtures show high thermal conductivity,low volumetric expansion on melting,low corrosivity and good stability,they are attractive as heat-of-fusion storage materials in this temperature range. A 35wt percent Li sub 2CO sub 3 -65wt percent K sub 2CO sub 3 (50mole percent Li sub 2CO sub 3 -50mole percent K sub 2CO sub 3 ) mixture was selected as a model system for further experimental work. This is a eutectoid mixture having a heat of fusion of 148Btu/lb (82cal/g) that forms an equimolar compound, LiKCO sub 3 . The Li sub 2CO sub 3 -K sub 2CO sub 3mixture is intended to serve as a model system to define heat transfer characteristics,potential problems,and to provide ''first-cut''engineering data required for the prototype system. The cost of a thermal energy storage system containing this mixture cannot be predicted until system characteristics are better defined. However,our comparison of different salts indicated that alkali and alkaline earth chlorides may be more attractive from a salt cost point of view. The long-term corrosion characteristics and the effects of volume change on melting for the chlorides should be investigated to determine their overall suitability as a heat-of-fusion storage medium. (ERA citation 02:017397)