Advanced phase-change materials for passive solar storage applications: Final report. [C-16 to C-24 alkyl hydrocarbons]

Our current and most promising series of candidate phase-change materials (PCM) is the crystalline alkyl hydrocarbons. Ultra-pure C-16 to C-24 alkyl hydrocarbons that melt and freeze sharply in the temperature range desired for solar-passive applications are available from Humphrey Chemical at a premium price. These alkyl hydrocarbons have heats of fusion (..delta..Hf) of 55 to 60 cal/gm, are self-nucleating, and exhibit little or no supercooling. However, paraffin waxes are commercially available at much lower cost from several petroleum refining companies (Witco, Shell, Exxon, Union Oil, Phillips Petroleum) that have melting points ranging from 15 to 80/sup 0/C, and are available at a quoted price of $0.28/lb ($0.15/lb for some grades) in tank-car quantities. We are working with Witco to further refine the commercial material in order to develop a wax that will meet our needs at an economical price. One possibly important facet of the use of the alkyl hydrocarbon PCM in cement and plaster is that these structural materials can be waterproofed simultaneously. As is well known, containment costs and attendant problems have been the bane of many of the PCM systems developed in the past. During the past year, we have preliminarily defined economic and effective methods ofmore » packaging the candidate PCMs in common construction materials. Importantly, the containment methods appear to also provide a means of adequate heat transfer; and the processes are of the type that could be rapidly implemented by commercial manufacturers of building materials. 99 figs., 81 tabs.« less