Compact storage of seat and coolness by phase change materials while preventing stratification

While many materials and additives which will melt and freeze at various temperature levels for storing and releasing large amounts of heat thereby per unit volume have been disclosed, the packaging of these materials with suitable non-corrodible long-lasting heat exchange structures has been cumbersome and expensive. The present invention provides an inexpensive, high performance, non-corrodible thermal storage method and system adapted for use with heat storage materials of various compositions and adapted for use over a wide range of temperatures, including a heat exchanger which provides for phase change to occur approximately simultaneously throughout the volume of the entire storage mass and provides for the sites at which the phase change is occurring to be approximately uniformly distributed throughout the volume of the heat storage material. Problems of thermal expansion, stratification and sub-cooling are eliminated. Thermal storage methods and systems embodying the present system may advantageously be used for off-peak storage of electric refrigeration, cooling and heating as well as solar heating and other applications.