Use this in mini greenhouse for "rotation planting transplants"? The thermal "battery" in a passive solar greenhouse - barrels of plain old water on the north wall of the structure. Warmed by day, they release their heat at night.
Greenhouse design being used in Colorado at 30 below 0 temps with no added heat other than solar and stored energy. it will have 55 gallon barrels filled with water only. These will be stacked against the inside back wall 3 high and 7 wide.