- Author
- Struble, L. J. | Brown, P. W.
- Title
- Inorganic Compounds for Passive Solar Energy Storage: Solid-State Dehydration Materials and High Specific Heat Materials. Progress Report.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
- Sponsor
- Department of Energy, Washington, DC
- Report
- NBSIR 86-3325, April 1986, 69 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- solar energy | inorganic compounds | dehydration | enthalpy change | ettringite | Friedel's salt | latent heat storage | passive solar energy storage | sensible heat storage | solar energy storage | specific heat | inorganic salts
- Abstract
- Two classes of hydrated inorganic salts have been studied to assess their potential as materials for passive solar energy storage. The materials are part of the quaternary system CaO-A1₂O₃-SO₃-H₂O and related chemical systems, and the two classes are typified by ettringite, a trisubstituated salt, and Friedel's salt, a monosubstituted salt. The trisubstituted salts were studied for their possible application in latent heat storage, utilizing a low-temperature dehydration reaction, and both classes were studied for their application in sensible heat storage. In order to assess their potential for energy storage, the salts have been synthesized and characterized by several analytical techniques, and their thermal properties measured. The dehydration data of the trisubstituted salts vary somewhat with chemical composition. The temperature at which dehydration begins range from 6 deg C to 33 deg C, and enthalpy changes on dehydration range from 0.3 to 0.8 kJ/g. Heat capacity values for all trisubstituted salts are approximately 1.3 J/gK and for the monosubstituted phases range from 1.0 to 1.2 J/g/K. Preliminary experiments indicate that dehydration of the trisubstituted phases is reversible, though additional tests are required. These thermal data demonstrate that the trisubstituted salts do have potential as latent heat storage materials, and that both classes of salts have potential as sensible heat storage materials. Furthermore, it is noted that these materials may be contained in conventional portland cement concrete, making them particularly attractive for thermal energy storage.