PORTLAND — Drivers who use a new parking lot at the Portland International Jetport won’t notice, but their vehicles will be atop more than 11 miles of plastic tubing.

If they could slice open the earth, they would see 120 loops extending 500 feet into bedrock. And if they could peer through the tubing, they would see fluid circulating at 500 gallons a minute.

Drill rigs will run every day for the next month to turn the land under the new parking lot into a giant heat exchanger. The fluid will absorb some of the earth’s stored heat in winter and help warm a new addition at the jetport. The process will be reversed in summer, with heat being dumped into the cooler earth.

When the jetport’s $75 million expansion opens in 2012, it will be heated and cooled by Maine’s largest geothermal system. The system is expected to cut the amount of oil that would otherwise be used for the new terminal by 90 percent — nearly 102,000 gallons a year.

Geothermal heating and cooling isn’t new, but it has been slow to catch on in Maine. That may be because it’s less familiar to contractors here, and because the systems are expensive to install.

But supporters say geothermal, when properly financed, can compete with oil heat because of its low operating costs. They hope high-profile systems such as the one being installed at the jetport will draw more attention to geothermal as an alternative, especially in commercial buildings that are climate-controlled year-round.

One advocate is Paul Bradbury, the jetport’s director. Trained as a mechanical engineer, Bradbury sees geothermal as a way to help control long-term energy costs at the city-owned airport.

“There’s no question in my mind that it’s an underutilized technology in this state,” he said.

The system will warm and cool the jetport’s 137,000-square-foot addition, which is being built to high energy-efficiency standards.

The system will cost $3 million. Roughly $2.5 million is coming from a federal program aimed at reducing air pollution and climate change emissions at airports. Portland is the first commercial airport to use the money. The balance will come from fees paid by airport passengers.

The system is being designed and installed by National Geothermal of Plymouth, Mass., with help from local contractors and drilling companies.

Visitors can see the work as they drive by the airport entrance across from the Hilton Garden Inn. On a recent day, the roar of four drilling rigs filled the air as their bits gnawed away at the bedrock.

“This isn’t a huge technological leap for Maine,” Bradbury said, noting that the work is similar to installing a well.

The bore holes are 20 feet apart in the well field. Steel casings stick up from the earth at the finished holes, with sprouts of black polyethylene tubing. The tubing will be tied together to a manifold and routed underground to the jetport’s mechanical room via 10-inch supply and return lines. The system is a closed-loop design; it’s sealed and won’t exchange fluid with groundwater.

Indoors, warmth will come from radiant floors heated electrically to around 100 degrees. Because the earth below the frost line in Maine averages about 50 degrees year round, it will take relatively little energy for heat pumps to raise the temperature to a comfortable level in the building.

A small oil boiler and baseboards will still be needed, to temper winter heat loss against a stretch of big windows.

Geothermal systems have been installed in Maine since the late 1970s. The state has at least 500 homes that use geothermal heat, according to industry estimates, and at least two dozen commercial buildings.

Roughly 50,000 such systems are installed in the United States each year, according to the Department of Energy.

One of the larger commercial systems in Maine is at the Black Point Inn in Scarborough. It was installed in 1998 by Eric Cian-chette, a developer who owned the inn. “I was the first guy to do a commercial one here in Maine,” he said.

Cianchette also used geothermal when he built the Evie Cianchette Block on Portland’s Commercial Street in 2000. And he installed a system at his house in Falmouth.

“Once you get past the cost of equipment, geothermal is the way to go,” he said.

Most of the large commercial systems in Maine are at schools, including Gorham Middle School, the University of Maine at Farmington, the University of Southern Maine in Portland and Bowdoin College in Brunswick.

Homeowners may be scared off by the cost. Total prices can range from $22,000 to $30,000 for a typical new home, said John Logan, regional director in Maine for Water Energy Distributors Inc.

But when geothermal is financed as part of a mortgage and owners take advantage of the current 30 percent federal tax rebate, Logan said, the systems immediately save money, compared with heating with oil.

Logan helped persuade the Legislature to pass a resolve directing the state’s energy office to examine incentives for geothermal systems, especially in multifamily homes. That study is due out this winter.

Logan hopes the system being built at the jetport will raise geothermal’s profile in Maine, for installers, well drillers and the public.

He said, “It’s one of the best-kept secrets in Maine.”

 

Staff Writer Tux Turkel can be contacted at 791-6462 or at: tturkel@pressherald.com