Thermal Mass and Passive Solar Heating

i'm coind o fascinated by its thermal mass and passive solar heatings. And also, given how hot it has been in the midwest for the last couple of weeks, i would like them to start experimenting with cooling the sand as quickly as possible. I don't know enough about it to say, maybe somebody out there is an engineer who can explain that,. But could you use the heat that you store in the sand, like in a heat pump sort of situation? To create energywith a difference.