Any green home worth its weight in compost draws heavily on solar energy. Mine is equipped with all the standard offerings, such as a solar-powered boiler, the subject of my last column. Trouble is, the sun doesn’t always shine. So to make up the difference during cold, dark winters and rainy spells, I’m turning to another eco-friendly energy source: my backyard. The two 325-foot-deep geothermal wells I’m boring there will use the constant 50°F temperature of the Earth at that depth to meet all my extra heating and cooling demands.
A geothermal heat pump works like a regular heat pump, only it pulls heat out of the ground instead of the air. During the winter months, the pump circulates a mix of water and glycol (antifreeze) into the wells through loops of pipe. The fluid absorbs warmth from the ground and travels back up to the pump, which absorbs the extra heat, compresses it to make it even warmer, and then transfers it to the heat exchangers inside the tanks that supply my hot water and radiant heating. In the summer, the process reverses, with the pump sending water and glycol into the pipe to help cool the house.
The upfront costs of geothermal are steep. I paid $16,800 for the whole installation, even after the tax credit [see “Get Green for Going Green”] and doing some of the work myself. But the system should pay for itself within six years. Geothermal is four times as efficient as fossil-fuel-burning furnaces and twice as efficient as a conventional air conditioner. And unlike gas and oil, the price of dirt is steady, so my energy bill won’t spike with the market.
Next up: building energy-efficient windows.
House: 3,500-square-foot, four-bedroom contemporary
Location: Greenwich, N.Y.
Project: Geothermal heat pump
Cost: $16,800 (after tax credit)
Time to install: 5 days
Eco-advantage: No emissions; consumes 33 percent less electricity than typical HVAC systems
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.