[dmlorenzetti]

You're not way off at all. In a lot of climates (SF bay area is a classic example, but also think deserts), the average temperature is comfortable even if the extremes are not. So if you have a good way to store heat during the day, and use it to avoid heating at night, you can avoid direct use of energy for heating and cooling, and yet stay comfortable most of the year.

In this case, they're not exactly storing heat, since it sounds like they require sunlight to charge up the store. However to the extent that peak cooling corresponds with peak insolation, the material might be very useful for the design of passive/net-zero-energy housing.