Heating and Cooling with Geothermal Energy

Whether the air is sweltering or freezing, the temperature 10 feet below the ground is always 55 degrees.

And that’s the key to geothermal energy systems, which circulate fluid through tubes buried in the ground, then extract the earth’s hot or cool energy and send it through the building.

“You’re using the ground as a heat exchanger,” said Mark Nelson, sales manager for Wulf Brothers, Inc. “When you’re cooling you’re putting heat into the ground, and when you’re heating you’re extracting it.”

Wulf Brothers has put geothermal heating and cooling systems in about 20 Door County homes, Nelson said. To build one, Nelson has to drill wells 10 feet into the ground to run the tubes. Bigger homes that use more energy to heat and cool require more wells.

The upfront costs of implementing geothermal heating and cooling can be expensive, ranging from $10,000 to $100,000 depending on the size of the homes.

Still, there are reasons customers choose to go geothermal.

Once a geothermal heating and cooling system is in place, the costs for running it are low. Jennifer Merkel put a geothermal system into her home in 2009, and took advantage of a 30 percent tax credit on residential renewable energy systems.

“We felt that the overall savings in energy costs were well worth it over the long run,” Merkel said. “And the tax credit helped us with that, too. It turned into a no-brainer for us to go that route.”

Merkel has an electric backup system for the few winter days when the temperatures reach bitter lows, but for most of the year the geothermal energy is enough to keep her home comfortable. She said it’s also easier to maintain than other systems, and since most of the system is underground it’s more attractive than fuel systems that require things such as outdoor propane tanks.

“You don’t have any extra equipment or unsightly fixtures outside your home,” Merkel said. “It’s a nice, clean system. You don’t see all that other stuff. It keeps your property looking a little bit nicer.”

Geothermal heating is more efficient than other types. Nelson said geothermal has a “cost of performance” score of four, compared to electric baseboard heating with a score of one. So for every dollar you pay to heat your house, you’d get four times the heat from a geothermal system than an electric baseboard system.

That high “cost of performance” score makes geothermal energy more environmentally friendly, too. Geothermal energy doesn’t use any fossil fuels, and releases few carbon dioxide emissions.

“A lot of people are really doing it because they’re trying to be green,” Nelson said. “They’re trying to reduce their carbon footprint.”

Geothermal Energy Facts

• Geothermal energy was first used in Italy in 1904.

• Geothermal energy is produced in more than 20 countries.

• More than 87% of Iceland’s homes use geothermal heating.

• It’s easiest to extract geothermal energy near volcanoes, hot springs and geysers

• Geothermal plants emit 97 percent less acid rain-causing sulfur compounds than fossil fuel plants.

Source: National Geographic, U.S. Energy Information Administration