Some greenhouse are partially or even completely sunk below ground and take direct advantage of the natural warmth of the surrounding soil. Above ground geothermal greenhouses typically employ a series of underground pipes, through which air travels, absorbing heat from the natural heat of the earth. Many passive geothermal greenhouses will also employ thermal batteries to store heat during the daytime and then gradually release it during colder nights through the thermal flywheel effect.
Many passive geothermal greenhouses will also employ thermal batteries to store heat during the daytime and then gradually release it during colder nights through the thermal flywheel effect. These batteries may be as simple as a series of large plastic water barrels, painted black.
