Geothermal greenhouse in Nebraska grows citrus year round

Using a sunken greenhouse heated by geothermal, a Nebraska farmer is doing what everyone thought impossible, producing fruit 365 days a years with no energy costs in an area where it gets really cold in the winter. Most of the time it doesn’t need heating, when it does, heat is produced at a dollar a day by circulating air from pipes 8 feet deep where temperatures are warmer.

The floor is dug down, 4 feet below the surface. The roof is slanted toward the south to catch as much sun as possible. During the day it can reach well into the 80s inside the greenhouse, but at night the temperature plummets. That’s when Finch draws on geothermal heat.

No propane or electric heaters here. Instead, warm air is taken from perforated plastic tubing that is buried underground. The plastic tubes go out one end of the greenhouse and run a loop to the opposite end. A single fan circulates air through those tubes. As the air moves through, Finch says it picks up enough heat from the soil to keep his oranges out of danger.

“All we try to do is keep it above 28 degrees in the winter,” Finch says. “We have no backup system for heat. The only heat source is the Earth’s heat, at 52 degrees at 8-foot deep.”