http://thermalbatterysystems.com/2013/0 ... UhbG0IzrNA
In the early days of the development of Thermal Battery Systems we studied the use of phase change materials or PCM’s for their latent energy storage capacity. These materials are waxes or salts and we got ours from a company in Germany called Rubitherm. Rubitherm makes a number of different phase change materials that have different melting points and different latent capacity. We also got a 5 gallon bucket of technical grade Eicosane from a company in the states called Roper Thermals.
We did some testing with these materials and we came to the eventual conclusion that the best PCM for our purposes was… water. The thing is, the freeze point of water is generally not considered to be in a useful temperature range for thermal energy storage. Thus, it is not often considered as an option when PCM’s for thermal energy storage are being studied or discussed.
In our case the 32 degrees happens to be ideal. It provides a soft landing point that is at the temperature that closed loop geothermal systems are rated to operate in. This also allows the system to be in the best possible condition for receiving source energy during times that the loads are the heaviest.
A Thermal Battery System is a phase change material latent energy battery. That just sounds better than calling it a cistern tank full of water.