Pennsylvania Farm Stores Heat Underground

Tim Clymer of Threefold Farm in Pennsylvania built a greenhouse that stores heat in the soil. He designed the system to avoid burning propane, a common practice that raises costs and contributes to climate change.

During warm days, fans move air into underground tubes to heat the surrounding soil. When temperatures drop, the system reverses and draws heat from the soil back into the greenhouse.

Clymer began using this “climate battery” greenhouse roughly nine years ago. He currently grows figs, Meyer lemons, and satsuma mandarins inside. He now shares his design through a company offering plans and consultation to other farmers.

The system’s effectiveness depends on consistent temperature differences between the greenhouse and the earth. Clymer continues to refine the design and help others adopt this alternative heating method.