You don’t have to coax Dan Sirkis into talking about geothermal energy.

The chief of the Geo-Environmental Section in the U.S. Army Corps of Engineers (USACE) Philadelphia District extols the benefits of geothermal every chance he gets, whether he’s talking to a colonel in the Pentagon, an engineer in the field, or a student at a local high school.

And not just for places such as Iceland or Yellowstone National Park where the magma is close enough to provide direct heat and the hot springs burst through and awe the tourists.

“When you say ‘geothermal’ people tend to think of places like that,” Sirkis said, “and that is certainly one form of geothermal energy. Call it ‘Big-G’ geothermal.”

But the kind of geothermal Sirkis likes most to talk about is more properly called “ground source energy” and works about as spectacularly as your average heat pump, which is precisely how it does work.

Ground source energy takes advantage of the relatively constant temperature a few feet below the earth’s surface.

“The earth maintains a relatively constant temperature of about 55 degrees Fahrenheit,” Sirkis said. “In the winter, when the temperature outside is 35 degrees, that difference can be used to help heat a building. In the summer, with the temperature at 85, it can be used to cool the air.”

Conventional heat pumps use air as a mode of heat exchange. Ground source energy systems use the earth, a far more efficient medium.

The technology has been in use for more than two decades now, in both the public and private sectors.

The Army installed a ground source system at Fort Monmouth in New Jersey in 2003 and more recently has installed systems at Fort Drum in New York and Fort Gordon in Georgia. The New England District of USACE has been working with the U.S. Army Engineer Research and Development Center, in Vicksburg, Miss., to develop a ground-testing protocol that will help developers decide what kind of system would work best at their site.

Despite their potential, geothermal energy systems – whether you’re talking Big-G or ground source systems – have not been widely employed. Geothermal systems today provide less than 1 percent of the country’s heating and cooling needs.

Figures like that challenge Sirkis, who knows that the science is sound and the technology proven, and, in most cases, the economics are favorable, too.

“Ground source energy is good all around,” Sirkis said. “Take your pick. If you’re worried about operating costs, it will save you money. If you’re worried about the environment, it doesn’t burn fossil fuels and pollute the air. If you’re worried about Libya and the Mideast, it reduces dependence on foreign oil.”

The only real obstacle, he said, is upfront costs. Ground source systems cost more to install than conventional ones, but with reduced operating costs, Sirkis noted, a large building can make up the difference in three to six years, from which point the savings just keep piling up.

What’s needed, apparently, is some promotion. Philadelphia, better known for cheesesteaks than hot springs, to be sure, is nonetheless ready to do its part for ground source energy.

The Base Realignment and Closure Commission’s decision to close Fort Monmouth and move that operation to Aberdeen Proving Ground, Md., gave the Philadelphia District its chance to become a champion of ground source energy.

“We were blessed with C4ISR,” Sirkis said, referring to the communications operation – Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaissance – that the Army moved to Aberdeen. “They wanted us to do geothermal at the new facility. We did. We like it. Now we’re trying to export the technology.”

Ryan Scanlan, an environmental engineer at the Philadelphia District who worked on the Aberdeen project, discussed the largest building that the district constructed there for the Army.

Known as C2East, it is a five-story, 500,000-square-foot building, completed this fall, that the Army will use to develop, operate, and administer a variety of sophisticated communication systems.

Keeping it warm in the winter and cool in the summer will be a ground source energy system – more precisely a “closed loop, ground source heat pump,” Scanlan said. No fewer than 750 wells are being drilled deep into the ground that will eventually be paved over and become a parking lot.

Each boring is being drilled approximately 360 to 400 feet into the ground and consists of a supply and a return with a U-bend at the bottom.

There is nothing magical about the depth of the wells, Scanlon said, as the temperature of the ground remains fairly steady once you have gone down a few feet below the frost line. What’s important is to have a length of pipe sufficient for the heat exchange to take place (whether the pipes are laid out vertically or horizontally) – and for there to be enough room between the pipes or wells so they are not influencing each other.

“The wells are 20 feet apart,” Scanlan said. “This allows the earth to heat up without influencing other wells.”

With the ground temperature holding steady at about 50 to 55 degrees, the U-bend can be used to extract heat from the ground in the winter while serving as a place to dump heat in the summer.

Estimates indicate that the ground source heat pump will be nearly 50 percent more efficient in heating and cooling C2East than a conventional system, costing roughly $600,000 a year to operate versus $1.2 million with a conventional boiler system.

At that rate of savings, the project will pay for itself in less than six years.

And with few moving parts, the system requires relatively little maintenance, Scanlan noted, adding one more plus to the list.

“It’s designed to last 30 years,” he said of the system being installed at C2East, “and that’s backed up by the designer and the contractor.”

Economies of scale figure prominently in the decision on whether or not to install a ground source system, Scanlan said. For schools, hospitals, and military installations it makes eminent sense. For homeowners, the big bite at the outset is likely to be more daunting.

“A 2,000-square-foot house would require two 400-foot loops,” Scanlan said. Horizontal tubing could be installed, 4 to 5 feet down, provided the lot was big enough, saving the homeowner the cost of vertical borings. But the cost would still be substantial relative to the annual savings. “You could be looking at 20 to 25 years to get your money back, which is tough for most people to swallow,” he said.

In addition to size, a number of other factors – windows, insulation, roof materials, location – need to be considered when deciding whether to go geothermal, he added.

But overall, and particularly for larger buildings, the Philadelphia District has become positively bullish on geothermal.

“We’re talking with the 99th about installing it at their sites,” Sirkis said, referring to the Army’s 99th Regional Support Command, which supports Army Reserve facilities in 13 Northeast states from Maine to Virginia. The 99th operates out of Fort Dix, N.J., and has been in frequent and extended conversations with the Philadelphia District about geothermal (as well as other energy-saving moves such as LED lighting).

The district is administering about $500 million a year in contracts to build power facilities in Afghanistan, an undertaking with significant potential for geothermal and other alternative energy ideas.

“Afghanistan actually has the Big G geothermal,” Sirkis noted. “It is very active geologically, with young mountains in some places with high-temperature rock, magma, close to the surface.”

Tom Gibison, the project manager for contingency power contracts, said anything the Army can do to reduce oil consumption in Afghanistan would be more than welcome. The cost of transporting diesel fuel to conventional power generating stations is high in both dollars and lives.

“There’s a casualty every 16 convoys,” Gibison said.

The district has been talking with the 249th Prime Power Company, the military unit of USACE that installs generating equipment in the field, and with the Office of Operational Energy, the Army office that deals with energy for deployed units.

“If we can give someone an idea and they can run with it, great,” Gibison said.

This article first appeared in the 2011-2012 edition of the U.S. Army Corps of Engineers Building Strong®, Serving the Nation and the Armed Forces publication.