The sand battery for heat storage. Another good reason for compact, campus style development versus sprawl.

I read that Finland now has a sand battery in use for storing heat from intermittent energy sources; such as solar energy. This can work well for district heating systems; such as central steam heating systems on university campuses.

Excess power, from solar panels during sunny daylight hours, can be used to heat the sand. Sand is easier to work with than water at higher temperatures; otherwise they would just use water, I guess. When water is heated, it becomes pressurized. Sand can be heated to over 1,000 degrees F.

At night, air can be circulated through the hot sand and then go to a heat exchanger to heat water. Hot water is then piped to buildings that are close to one another similar to the steam / hot water systems on many college campuses. This system could fit into an already existing district heat system, like I would guess at a college campus.

This could fit into my philosophy of more compact city planning, versus spread out sprawl. Using a sand battery in a sprawling area would be more difficult due to bringing hot water out to each house. That would imply using it to generate electricity to send longer distances. I think generating electricity from the stored heat would add another layer of complexity.

Just moving the heat itself into an already existing heat distribution system; such as a district heating system for a campus, would be easier. This heat battery could also be used for some industrial processes as well.