in a Missouri USA they pump water up a hill then drain it back when demand increases, it's a rather large system. In Al'Abama an individual is using underground salt water tanks to store hot an cold salt water for HVAC and electric on his farm.
personally.... I use solar electric to drive a 10k/btu AC and scavenge the unit's waste heat as a food dehydrator, storing food is also storing solar energy and the AC keeps is pleasant indoors.