Water and soil below ground contain a vast reservoir of thermal energy, thanks to the natural heat emanating from the magma layers stretching thousands of miles below the earth’s crust. Geothermal greenhouse systems can take advantage of this stored thermal energy and use it to heat (and cool) greenhouses. This is done by pumping air through the greenhouse and into the ground, where the surrounding soil cools or warms the air its in contact with. The newly warmed or cooled air is then pumped back into the greenhouse, equalizing the ambient temperature.
Geothermal energy can also be harnessed through a sunken greenhouse. A building in contact with soil, either by excavating the foundation or building into the side of a hill, will be heated or cooled by the ambient Earth's temperature. Since soil beneath the surface maintains a steady temperature despite the air above, a sunken Greenhouse can remain within a general comfortable temperature yearround.
