So…geothermal? I wish this was possible too but I don’t see how it will work scientifically. Water is one of the chemicals that have one of the highest thermal mass/specific heat (maybe 1/3 of salt hydrates). Even then, you have to bury a crapton of water underground. This design mentioned in the article is more for short term, like 12 hours storage (since they’re accommodating for solar in nighttime)
Is geothermal not the opposite of that? My understanding was that the geothermal MO is that there's virtually infinite thermal mass in the earth so it won't heat/cool, not that you heat/cool your local chunk