Thanks!
Ok, just playing around, I wonder if a mini “geothermal “ configuration could be cost effective in some climates. For example in the pacific NW summer days and are hot but nights are cool. So often no AC. But if for control of pollution (forest fire smoke) you use heat pump a small 2 foot diameter 15 foot deep hole could house both heat pump coils and a fan driving cold air to capture cold for use during the day. In the winter a green house effect could heat the same thermal battery perhaps cheaper than solar cells.

In desert areas with cold nights an extreme heat during the day a thermal battery might also be cost effective.