Homeowners tap earth for geothermal energy
With concern about energy costs and environmental sustainability now widespread, people are less likely to snicker when others talk about “green living”. Whether the intent is to reduce their ecological footprint or to seek greater value for money, more and more people are harnessing the power of renewable energy sources at home.
Solar, water, and wind power are well-known forms of clean energy but aren’t necessarily easy to use in one’s humble abode. A prohibitively high installation cost is the typical reason such options are swept under the proverbial rug.
Geothermal energy, which comes from heat stored beneath Earth’s surface, is another form of clean energy. It can be tapped by homeowners through the use of a geothermal heat pump—a system often referred to by its trademarked name, GeoExchange.
GeoExchange systems use the ground as a source of heat for a building. They were developed more than 50 years ago, but recent innovations have made the technology more efficient. While these systems require an initial investment of thousands of dollars, they can lead to significantly lower monthly energy bills compared with conventional electric or natural-gas heating.
In the past, GeoExchange has mainly been applied to office blocks, apartment buildings, and district heating systems, where the initial expense can be absorbed by large organizations. But these days, single-family homes are starting to reap the rewards. According to a survey by the Canadian GeoExchange Coalition, more than 3,000 geothermal heat pumps were installed across the country in 2006 and industry revenues grew by about 40 percent in both 2005 and 2006. The survey identified British Columbia as one of Canada’s most active markets for GeoExchange systems.
Guy Dauncey, president of the B.C. Sustainable Energy Association, calls GeoExchange “a really efficient way of taking existing energy from a renewable world and using it to heat a building”. Switching to renewable energy sources is key, he told the Georgia Straight in a phone interview, because “all energy coming from fossil fuels is part of a 200-year blip in time, which, when it’s ended, has ended forever.”
Here’s how GeoExchange works: a few feet below Earth’s surface, the ground holds a constant year-round temperature of 10 ° C to 20 ° C. It’s this stability of temperature underground, regardless of the weather, that GeoExchange exploits. Specifically, a pipe is buried underground; it contains a fluid that absorbs heat from the earth as it travels the length of the pipe. The fluid passes through a heat exchanger that extracts the heat, using a small amount of electricity. The heat is distributed throughout the home via forced-air ventilation or a radiant-heating system under the floor or behind walls or ceilings.
Some GeoExchange systems can also operate in reverse to cool a home, by transferring heat from the home to the colder ground. By performing both the heating and the cooling, a single system can replace separate furnace and air-conditioning units.
What kind of savings could you see? According to John Maragliano, CEO of the Vancouver-based GeoTherm Utility Corporation, which installs residential GeoExchange systems, local residents can expect ongoing savings of between 50 and 70 percent on the heating and cooling of their home. “When you sit down with a homeowner and run through the numbers, it essentially sells itself,” Maragliano said.
But there’s still that pesky initial investment. A price tag as low as $10,000 and as steep as $20,000 for a residential installation means the system may take 10 to 15 years to pay for itself.
“GeoExchange systems, to a homeowner, [are] generally price-prohibitive,” Maragliano said, referring, in particular, to the installation of underground pipes. To up the incentive, GeoTherm Utility covers the cost of an installation, so the homeowner only pays monthly bills to the company.
Maragliano concedes that qualified GeoExchange installers are a rare breed, although not as much as in the past. The historical dearth of expertise in this field is also lamented by Vladimir Mikler, a partner in the Vancouver-based Cobalt Engineering, a building-systems consultancy that specializes in sustainable design.
“It was safer for many years for them [contractors] to steer the project towards installing something they’ve done before and were familiar with,” Mikler said.
Those considering GeoExchange should line up installers who have experience, check their references, and ask to see systems they’ve installed. Don’t just go digging up the back yard with your cousin, your best friend, and a case of beer, based on a semi-successful hot-tub installation.
Mikler is a big proponent of energy-efficient design for new houses and optimization of existing structures. According to him, homeowners should take care of such basics as fixing drafty windows, switching to double-paned glass, and insulating their house from top to bottom before looking at GeoExchange.
“I don’t think it’s wise to apply any highly efficient technology before the fundamentals of reducing the demand on the building are looked at,” he said.
Mikler also says it’s critical to get a detailed site-specific survey of ground conditions before proceeding with a GeoExchange installation.
You just might find that the monthly savings mean you can ditch your leaky hot tub and take trips to the health spa instead.