[sammyg2]

I worked on an interesting project in the 80's.
It was based on energy absorbtion during phase change (from a liquid to a solid or versa visa).
The product they were using was a special salt/water solution with a freezing point around 45 degrees.
it was contained in thousands of plastic bottles that were stacked in a something that looked like an enclosed swimming pool.

It's been a long time so the details are a little foggy but if I remember right, at night cooling tower pumps circulated water through the cooling towers which dropped the temperature significantly through evaporation and convection. Then the cold water was circulated around the plastic bottles. Eventually they would get cold enough to freeze.
During the day when it started getting hot, they reversed the flow of coolnig water from the bottles to heat exchangers in the HVAC system, which cooled the large industrial building.

The salt solution would freeze at 45 degrees but because of the phase change characteristics it wouldn't melt until it got to almost 50 and it would absorb a great deal of energy in the process.
It was actually very efficient except when it was humid or extremely hot outside. then it wouldn't get cold enough to freeze the salt at night. We installed one system in Palm Springs, another in the Ventura city building, and a couple others scattered around.
I worked for them on the side but make good $$$$.