The Heat Below

The pile of wood in the dooryard slowly seasons in the sun. The oil truck pulls into the driveway and the driver attaches a long hose to a pipe that leads to a boiler in the basement. These sights are as familiar in Maine as chickadees and potatoes. For as long as most Mainers can remember, heating one’s home in the winter months has meant burning something.

After all, it’s cold here. And while wood heat may work for the small percentage of the population with the space to store and the time to haul and split several cords a season, most of us rely on heating oil, and most of that oil comes from overseas, at an ever-increasing price. Small wonder, then, that more and more Maine homeowners and businesses are becoming interested in tapping the heat beneath the ground. Spurred by stimulus incentives from the federal government, the geothermal energy business is heating up.

It’s not new technology. Geothermal heating systems have been around for decades. But rising oil prices, coupled with an urgency to develop reliable, local sources of energy, have combined to make geothermal systems an attractive heating alternative.

Richard Hill, professor emeritus of mechanical engineering at the University of Maine, has been studying alternative energy sources for years. In the basement of his Orono home, he’s constructed a refrigeration unit that keeps food cool by transferring heat from the unit into the ground—a geothermal cooling system. Like any heat pump system, it works by transferring heat from one place to another. But Hill says that the term “geothermal” is misleading. “Geothermal energy is what they use in Iceland,” he says. Because the country is located over a volcanically active section of the mid-Atlantic ridge, Icelanders can use water heated by magma in the earth’s crust to heat their homes and power electrical plants. Only in certain areas of the world, including parts of the western United States, is this possible.

Maine has no volcanoes or hot springs, but the ground does absorb and store heat from the sun. Six feet below the surface, the ground temperature remains around 45° to 50°F throughout the year. This is the heat that systems typically referred to as “geothermal” tap into, but a more accurate term is “ground-assist heat pumps.”

These systems come in several varieties. A “closed loop” system circulates fluid between the ground and a building, with underground pipes laid either horizontally or vertically. An “open loop” system relies on a well or nearby body of water for the heat source.

Carl Snow, a former developer who has long been involved in energy issues, installed a hybrid of the two systems when he built a business park on Stillwater Avenue 20 years ago. It’s still going strong, thanks to the volume of water. “The entire project is run off a single well,” he says. “The key is having an adequate water supply. If you have a sufficient amount of water, you don’t thermally deplete the well.”

All heat pump systems can provide cooling in the summer as well as heating in the winter, because the process of moving heat from one place to another is entirely reversible. In the summertime, heat from inside the structure is transferred back into the ground (or water), keeping things cool and comfortable inside.

Retired University of Maine biology professor Ron Davis has recently contracted with ELCO Electric Inc., a Bangor company, to install a horizontal closed-loop system in his rural Orono home where he and his wife, Lee, also a retired professor, have lived for the past 35 years. The installation will cost them approximately $30,000. “It won’t pay for itself in our lifetime,” Davis acknowledges. “Our motivation is not primarily the money. We want to reduce our emission of greenhouse gases, and instead of burning oil, we’re using renewable sources of electricity.”

Jared True, geothermal division manager for ELCO, admits that the initial cost can be daunting. And retrofitting an existing building is more expensive than installing a geothermal system in new construction. “If somebody’s building a new home, the payback is usually somewhere around five years,” he says.

The installation itself takes about two weeks. Once the system is in place, maintenance costs are negligible. “The piping itself has a 50-year warranty, and a life expectancy of 200 years,” True says. “An oil burner would need an overhaul long before a heat pump would need to be repaired.”
The colder the weather, the harder a heat pump has to work, which is why many homeowners elect to keep an oil burner as a backup. According to True, it may make economic sense to install a slightly smaller system. “We might design a system that will work in temperatures down to five below zero,” he says. “In reality, it’s only going to be colder than that outside for a few hours a year. You might make the determination that it’s not cost-effective to install a larger system for those few hours.”

But Ron Davis, who installed solar panels on his house to heat water two years ago, expects his new system to supply nearly all of the home’s heating needs. “We’ll probably get by with less than 100 gallons of fuel this winter,” he says. “We used to use between 1,000 and 1,100 gallons, and we’re very frugal.”

When creating a system for a client, the first thing True does is a heat load analysis to determine how many BTUs (British thermal units) the house needs on the coldest day of the year. True then looks at the ground. In a horizontal system, soil type is important. Dry clay has about twice the thermal conductivity as dry sand. And, of course, in Maine, ledge is an obstacle, but ELCO can test for ledge depth fairly easily, True says.
 

The federal government, looking for ways to reduce dependence on foreign oil, has recently provided incentives for converting to geothermal. A homeowner can now take a tax deduction for 30% of the cost of installing a geothermal heating system, with no upper limit, and a business can deduct 10%.

The pump requires electricity to run, and owners typically see their electric bills double. But this is more than offset by the absence or near-absence of an oil bill. “We’re looking at about a 65% savings,” Davis says.
The Davises pay a small voluntary premium on their electric bill to support renewable sources of electricity. “The electricity comes off the grid, but the premium supports development of green energy sources,” Davis says. “And when you’re using electricity from the utility, you’re creating much less pollution.”

As fuel costs rise, geothermal systems look increasingly attractive, even factoring in the initial cost. Still, much of the success of geothermal heating in Maine depends on developing reliably priced sources of electricity, such as wind and hydro power. Currently, most of Maine’s electricity comes from natural gas, which makes future rates unpredictable.
“Heat pumps are very simple,” Hill says. “Something gets hot, something gets cold, and power to run it comes from the power company. The utilities are in good shape now; there’s enough generation capacity. But we’re not going to go very far with heat pumps before we have to do something about the generation of electricity.”

Another obstacle to widespread use of geothermal is the capacity of the ground itself. Because heat is being moved, not created, the ground grows colder as the surrounding homes heat up. Hill foresees potential property issues. “You could get into a situation where you’re pulling heat from out of your neighbor’s yard.”

Duane Hallowell, CEO of Hallowell International Heating and Cooling Systems of Bangor, has been busy developing a lower-cost alternative to geothermal: an air-source heat pump that can heat an average home even in subzero conditions. His patented Acadia heating and cooling system uses something called “boosted compression” to draw heat from the outside air and concentrate it. Hallowell claims the unit, which costs about $12,000 fully installed, rivals geothermal in efficiency. “I’m not against geothermal,” he says, “but we can provide equivalent efficiencies without the huge installation costs. People need other choices besides fuel.”

Air-source heat pumps are the dominant heating and cooling system below the Mason-Dixon Line. Conventional wisdom in the industry has been that they don’t work as well in colder climates. But Hallowell has bet his company on the proposition that performance can be dramatically improved, and he has the sales and industry awards to prove it. The company’s business grew by 600% in 2008.

Much more innovation will be necessary before heat pumps, ground-source or otherwise, replace oil as the primary source of heat in Maine homes and businesses. It is not at all clear that the transition will be an easy one. Hill thinks that more attention should be paid to building design that conserves energy. “We need to be looking at retrofitting old buildings. The envelope of a building becomes tremendously important. The idea that you’re going to heat an old building with a heat pump is just plain wrong.”

Almost everyone agrees that the days of cheap oil will not return, and that Maine, along with the rest of the western world, will have to change. Hill believes that the consequences of rising oil prices will “ricochet throughout society,” affecting everything from rural real estate values to family living arrangements to the relationship between generations.

“Everyone wants to hear magic,” Hill says. “I’m convinced that there’s no technology out there, heat pumps included, that’s going to keep the future like the present.”

But for Ron Davis and others living in geothermally heated homes, the future includes smaller oil bills and a sense of local responsibility. The scars in the earth outside his window will heal in a season or two, and the pipes below the ground will warm his house for years. Meanwhile, some of Maine’s best minds will continue to apply themselves to weaning the state off its dependence on expensive foreign oil. As Duane Hallowell says, “Crisis is the mother of all invention.”