A simple mix of two cheap salts, Sodium Sulfate and Table Salt (Sodium Chloride) dissolved in boiling water can create a really useful Phase Change Material that has a melting point of 18c (65f) which allows it to be recharged back into it's cooling state simply by putting it in a basement and can then be used as a cooling blanket, back rest, neck pillow, etc to help keep you cool in hot weather. Longer lasting and less energy intensive to charge than an ice-pack.

In the video he talks about the potential for using a similar higher temp PCM behind solar panels to reduce efficiency loss or damage from over heating. It could also be a really interesting thing to use for transporting heat from where it's unwanted to where it's needed.