The heat beneath


PARIS – Outside temperatures were well below freezing Friday, but the offices of Bancroft Contracting were a comfortable 70 degrees.

That alone isn’t surprising, but how the local company actually keeps its offices at a comfortable temperature, both winter and summer, is.

Wrestling with how to best heat and cool an expansion to the company’s 4,500-square feet of office space, Mark Bancroft, company president, eventually settled on digging a 10-foot hole in the ground.

Inside the foundation-sized excavation, Bancroft’s workers coiled a mile of flexible piping, filled it with a special liquid and ultimately ended up tapping the natural geothermal energy stored in the earth.

When geothermal energy is mentioned, we may think of geysers at Yellowstone National Park where geothermal vents erupt from the earth or flow into hot springs.

But there are no hot springs in Maine.

Instead, there’s a layer of earth about 10 feet below the surface that is at a consistently stable temperature. At that depth and below, the daily atmospheric temperature does not affect the ground temperature.

It is too early to know how much the system will save Bancroft and his company, but he and other staffers said their building has been more comfortable than ever before.

Bancroft’s system involves a closed-loop with a liquid – what Bancroft calls an “environmentally friendly antifreeze” – passing through the underground plastic tubing. The liquid, which becomes the same temperature as the surrounding earth, about 45 to 55 degrees, is pumped through an above-ground geothermal heat exchanger with warm or cool air produced as needed.

The air is then blown into the building by a forced hot-air system. The company already had an oil-fired system in place, so it just needed to disconnect from the old oil-fired furnace, connect to the geothermal exchanger, and wave goodbye to its oil bills, Bancroft said.

The geothermal system uses electricity to modify, via a series of compressors, what Mother Nature provides. Then it circulates either warm or cool air throughout the building.

The heat exchanger’s technology works on a simple principal of thermal dynamics, the ideal gas law, which says as gas is compressed, the temperature increases.

In the simplest terms: “It takes the heat from the earth and makes it warmer,” Bancroft said.”The constant temperature of the earth acts like a heat sink or ballast. The heat exchanger efficiently modifies that energy to either heat or cool.”

Dave Everett of Everett Excavation Contracting did the excavation work on the 100-by-30 foot hole that was 10 feet deep. “For a while we called that pile Mt. Everett,” Bancroft said

While the in-ground component of this system is large, the above-ground portion is very small. A wall-mounted pump about the size of a box of donuts is located in a workshop. That connects to the adjacent geothermal heat exchanger, which is no bigger than an apartment-size refrigerator.

The system is controlled by a common thermostat on a wall in the office. Electronically regulated to keep the offices warm or cool as the season demands, the geothermal exchanger is controlled just as an oil or gas furnace would be – set the temperature and forget it.

Keeping up with the cold

The system is expected to function the most efficiently in winter. During the summer Bancroft found that the in-ground piping heated the soils adjacent to the piping, reducing its cooling effectiveness.

“As the warmer fluid from the exchanger was returned underground, some of that heat was lost to the ground. As the day went on, the fluid returned to the heat exchanger was warmer from the increased ground temperature around the tubing. That meant the system worked harder to cool the building as the day went on,” he said.

“Conversely, the loop field has cooled off some as we have been staying warm during the recent cold snap. The water is returning from the loop field in the mid-40s. After leaving the heat exchanger, it goes into the loop field in the mid-30s. That means the heat exchanger is extracting about 10 degrees from the earth and, in turn, the earth gives it right back.”

By the end of this winter’s heating season he expects to have a broader evaluation of the system.

And while his electric bill may increase slightly, that cost is more than offset by money not spent on heating oil.

In December 2006, for instance, Bancroft spent $170 more on electricity than he did in 2005, but he knows that his oil bill for that period would have been at least $200 more than that with the old system.

“Barring a few minor adjustments, which gave us some fits at first, it has actually done quite well and, during this real bad cold snap, we’ve been able to keep up,” Bancroft said.

Bancroft expects the system to pay for itself in about five years. It cost about $5,000 in excavation work to install the loop field in the ground.

The system itself would be comparable to buying and installing both an oil furnace and a central air conditioning system, Bancroft said.

“Of course, depending on the price of heating oil, the payback may be longer or shorter,” he said.

An idea by chance

Bancroft came upon the idea by chance, he said. The company had built an addition to its office building and he was looking into heating and cooling systems. Then he received an e-mail from Dan Everett (not related to Dave Everett) owner of New England Geothermal in Rumford.

Dan Everett was “cold calling” Bancroft, a heavy-industrial contractor that specializes in construction, maintenance and decommissioning for industrial clients throughout New England, to see if he might be interested in their companies working together.

Instead, Bancroft asked Everett to come take a look at their building and give him a quote on a geothermal system.

The closed-loop system Bancroft chose requires a large area in which to place the piping. A vertical closed-loop system is also available when outside space is limited. That option calls for a 300-to-500 foot shaft in the ground to contain the piping.

Dan Everett has seen the demand for geothermal systems triple in the last year.

“I think the demand is mainly because of fuel prices,” he said. “The oil companies really have a good squeeze on New England.”

Dan Everett’s company also has offices in Massachusetts, and he at first thought that’s where the biggest demand for the technology would be.

“It turned out Maine is,” he said. “People here tend to keep their homes for a long time, and they are willing to invest the money when they know it will be worth it in the long run.”

Dan Everett estimated that a geothermal system could provide heat, cooling and hot water to an 1,800-square-foot house in Maine for approximately $800 per year. With some people seeing close to that for a monthly fuel bill in winter, the demand for systems has soared. Of course, increased demand means a longer wait for the geothermal pump and exchanger.

“When I ordered the equipment, there was a two-week wait. Now, it is a several-month wait,” said Everett.

He is now contemplating opening a geothermal supply company in Maine.

Potential largely ignored

A new report on the potential of geothermal energy in the U.S. released by the Department of Energy on Jan. 22 found that geothermal systems could become commonplace nationwide within 10 to 15 years. Much of the 372-page report focuses on the potential of generating electricity from geothermal sources, like hot springs and other close-to-the-surface and naturally occurring geological heat sources, but a portion of the report also addresses the potential for systems like the one being used by Bancroft’s company.

Scientists in the U.S. have been studying the country’s geothermal potential for well over three decades and, while there are about a million systems in place here including some large ones – the entire capitol complex in Boise, Idaho, for example, is heated and cooled geothermally – the technology is still underutilized.

“Despite its enormous potential, the geothermal option for the United States has been largely ignored,” the DOE’s 2007 report states.

The energy crisis of the 1970s first promoted the federal government to take a hard look at the technology, but when oil prices declined again in the 1980s so did interest in geothermal energy, Bancroft said. But the current cost of oil and improvements in geothermal technology have again put the resource in the spotlight, he said. Still, government incentives, especially at the state level, are few.

The federal Energy Policy Act of 2005 provides limited incentives for geothermal exchange, and some states, such as New Hampshire, have specific incentives for geothermal energy. Maine does not.

The latest report for the DOE proposes the federal government increase incentives and also invest between $1.1 and $1.4 billion to help develop and deploy geothermal systems.

The report says the investment is justified by the “enormous potential” of geothermal and the “technical progress” made to date.

Mark Bancroft would clearly agree.

Regional Editor Scott Thistle contributed to this report.