The second in a series

When Aimee and Christopher Gerbi built their modest Old Town home two years ago, the couple caught the local contractor off guard when he asked their choice for a heating system.

Like nearly all Mainers, the Gerbis’ source of heat comes from the ground. But instead of originating from oil or gas fields in the Middle East or Arctic, the Gerbis’ heating source is literally right below their feet.

The young couple are among a small but growing number of Mainers who are going geothermal – tapping into the internal heat of the Earth to ward off the deep chill of winter.

Aimee Gerbi estimates it cost the family $1,200 to heat their 1,500-square-foot home last year. With heating oil prices approaching $5 a gallon, that is less than the cost of filling a 275-gallon tank once.

“I would absolutely recommend it,” said the young mother of two. “Anything we can do to get off of oil.”

That’s a common sentiment these days in Maine, where nearly 80 percent of households rely on oil for heat. Many home and business owners are desperately exploring their options, whether it’s doing some long-overdue winterizing, considering a switch to natural gas or installing new pellet stoves.

Geothermal systems, which convert the relatively steady year-round temperature of the ground into either hot or cool air, still account for a tiny fraction of home heating sources in Maine. One reason is the hefty initial cost.

Prices vary wildly depending on the type of system, the size of the building and whether extensive retrofitting of the heating infrastructure is required. But installing a geothermal system typically costs several thousand dollars more than a conventional oil, gas or pellet boiler, with some systems pushing $20,000 or more.

But more people are banking on the fact that once a geothermal system is installed, the only cost to heat or cool their house is the electricity it takes to pump the air through the house.

“As the price of oil climbs, the inquiries are going up exponentially,” said Erich Kluck, who handles registration of geothermal wells with the Maine Department of Environmental Protection.

“We went from getting five or six serious calls per year to having people call daily, all day,” said Heidi Watson of Littleton, a licensed dealer of geothermal systems and proprietor of the Web site http://www.geothermalmaine.com.

In use since the 1940s

The science behind geothermal systems is not new. In fact, air conditioners and refrigerators employ similar concepts and technologies to produce cold air, and geothermal systems have been in use since the 1940s.

The technology is based on the fact that the temperature of the ground several feet below the surface stays relatively constant – typically somewhere between 45 and 55 degrees – all year long regardless of air temperature.

Geothermal systems, also known as ground- or water-source heat pumps, work during cold months by absorbing the latent heat of the Earth within water or an antifreeze solution in underground pipes.

That heat is transferred to the heat pump, which uses compressors or exchange systems to concentrate the heat. The pump, which is often located in the basement, sends the heated air through standard ductwork in a house.

During summer, the process is reversed as hot air is removed from the building and transferred into the ground. Some units can produce hot water during summer and supplement the hot water system during winter.

There are two types of geothermal systems: open-loop and closed-loop.

Closed-loop systems use a continuous loop of piping either buried in coils in trenches near the home or run down into deep, vertical holes in the ground. Closed-loop systems can also be placed in ponds or lakes; however, they must be placed deep enough to avoid the winter freeze.

The amount and terrain of available land, soil properties, the size of the building to be heated and other factors will dictate what type of closed-loop system works best.

In open-loop systems, water is extracted from a well or water body and then transferred through the heat pump system. Once the heat has been extracted from or added to the water, the water is discharged either into a recharge well or on the surface.

The Gerbis installed an open-loop system after Christopher Gerbi saw one at work on Bowdoin College’s campus, where he was teaching. Because the family was building new, the higher price tag for going geothermal was just folded into the overall cost of the house.

“It was $2,000 extra, but it paid for itself last year,” Aimee Gerbi said recently while standing near her basement heat pump.

The system at UMF

Homeowners aren’t the only ones switching to geothermal in Maine.

The University of Maine at Farmington installed a closed-loop system in the campus’s Education Center, a 44,000-square-foot structure built in 2006. Heating such a large building requires a much bigger system, so the school had to dig 42 geothermal wells – each more than 350 feet deep – that connect to 39 heat pumps throughout the building.

Robert Lawrence, director of facilities management at UMF, said the system added to the cost of the $8.8 million building.

But the Education Center uses 70 percent less energy than comparable, older buildings on campus. The school expected to recoup those additional costs in as little as five years, but that estimate is based on two-year-old fuel costs.

UMF’s new geothermal system was featured in the influential academic publication the Chronicle of Higher Education, and Lawrence frequently finds himself giving tours to outsiders.

“With the way the price of oil is going, this little puppy will pay for itself in no time,” Lawrence said. “In the future, I think you will see us converting our other buildings to geothermal.”

Likewise, School Administrative District 28 in the Camden-Rockport area is installing its second geothermal system. Camden Hills Regional High School already uses geothermal energy to supply heat to part of the large school.

The new addition to the Camden-Rockport Elementary School will stay warm during Maine’s lengthy winters by an open-loop geothermal system run through a radiant floor heat network. Work on the 1,500-foot-deep wells is under way.

Keith Rose, director of operations and maintenance with SAD 28 and Five Town CSD, estimated that the school will save up to 75 percent on its energy bill with a geothermal system. That should mean a payback period of much less than the original estimate of 10 years.

“We would have to buy oil at somewhere around $1.60 a gallon to make it cheaper than geothermal,” Rose said.

Proper installation key

Proponents of geothermal say the technology is largely hands-off and will last for decades because both the piping and the heat pump are out of the elements. Geothermal systems also produce no direct pollution emissions, other than from the electricity needed to power the unit.

While those benefits are all true, the DEP’s Kluck said geothermal systems can pose serious environmental risks if they are not installed and maintained properly.

The piping in some closed-loop systems contains a toxic antifreeze solution, refrigerants or carrier oils that that, if leaked, can contaminate a well. Kluck recommends using a biodegradable, food-grade propylene glycol instead of toxic antifreeze and installing cathodic protection to protect copper piping.

Open-loop systems merely pump water from one area into another, albeit at a different temperature. But if that first well contains high levels of arsenic – which occurs naturally in parts of Maine – or other pollutants, the well or pond that receives the discharged water can be contaminated.

These are all examples of when “going green goes bad,” Kluck said. As a result, all geothermal wells must be registered with the state as Class V injection wells, he said.

Kluck also pointed out that there are no design standards for geothermal systems. But interest in the systems among consumers and contractors is booming, he said.

“My phone is ringing off the hook,” Kluck said. “All of the drillers and installers are calling all of the time to get into it.”

Watson’s business, Watson Well Drilling in Littleton, installed its first geothermal systems in family members’ homes in the mid-1980s. The family installed more systems over time, but demand was less because oil was so cheap.

Then three years ago the family launched Geothermal Maine and demand began to grow. Today, the company sells heat pumps and works with a network of independent drillers and contractors throughout the state.

Watson said the total electric bill for her old farmhouse – located in the Aroostook County town of Littleton – was approximately $2,900 last year.

“I love it,” Watson said. “Today it’s cool and tonight if I want heat, I’ve got it.”

Air-source heat pumps

Some Mainers are also considering a related technology that, while common in the Southern United States, has not been widely available in colder climates until recently.

Air-source heat pumps employ the same concept as geothermal systems, only, as their name implies, they extract heat or cold from the air rather than the ground.

Such systems, which also serve as either heaters or air conditioners, have been used for decades. But designers struggled to develop systems that were reliable when the mercury drops below zero.

Two Bangor-area companies – Hallowell International LLC and Nyle Special Products LLC – have been leading the effort to make air-source heat pumps that are practical for Northern climates. In fact, the companies’ technology is so similar that they are in the midst of a court dispute.

Bill Hillery of Glenburn installed one of these new-generation air-source heat pumps in his family’s home when he was faced with a dying oil furnace.

Putting in a new furnace would have cost between $10,000 and $11,000 in part because Hillery would have been required to bring everything up to code. The air-source heat pump he installed cost $14,000.

During a typical February, his family would go through 95 gallons of oil. But with the heat pump, the family’s electric bill rose only $115 last February, he said.

“We were experiencing over 60 percent savings and we had the temperature much warmer in the house,” he said.

Hillery was so pleased with the system’s performance that he has persuaded the leadership at St. Mary’s Catholic Church in Bangor, where he serves on the parish council, to install the technology. The church is awaiting final approval.

“The pope was here [in the U.S.] not long ago and one of his messages was … keeping ‘green,'” Hillery said. Switching to a heat pump, he added, will allow the church to do that and save money at the same time.

kmiller@bangordailynews.net

990-8250

BANGOR DAILY NEWS PHOTO BY GABOR DEGRE

Aimee and Christopher Gerbi’s furnace isn’t really a furnace. It operates by removing heat from water drawn from their well and circulated through the geothermal water-source heat pump they had installed in their home. The Gerbis moved into their Old Town house in January 2007, and after a full year their heating cost was about $1,200.