Yes! Geothermal greenhouses harness the natural warmth of the earth to supply heat directly to the greenhouse. In some cases, air is simply circulated through underground pipes where it absorbes the natural heat of the soil and is returned to the greenhouse. In other cases, underground aquifers can be accessed via deep wells where very warm water is pumped through a specialized heat pump which using a heat exchanger to collect the heat, a device similar to the curved pipes found on the back of a refrigerator.
Sometimes, greenhouses are constructed either partially or completely below ground, which may both insulate and transfer heat into the greenhouse. Even in partially submerged greenhouses, though, a well insulated cover and tightly sealed joints are necessary to retain the available heat.
