A down-to-earth way to heat schools
This appeared in the September 6, 2005 issue of the Roanoke Times.
In Rockbridge County, the schools are cool. In the winter they’ll be warm. And keeping them that way is going to cost the county a fraction of what it used to.
Three elementary schools are using a new kind of heating and cooling system that literally uses the Earth as an air conditioner and a furnace.
Known as geothermal heating and cooling system, it takes advantage of the natural temperature of the planet once you get below the frost line. While the surface temperature changes with the seasons – below zero in the winter, to possibly over 100 in the summer – dig a little and it stabilizes.
“Once you get below that [first few feet] it stays very constant,” said Bob Tracy, chairman of the geosciences department at Virginia Tech. “You don’t have to go down very far.”
A geothermal system can take advantage of that constant temperature, drawing heat from the Earth in the winter, and dumping heat into it in the summer. That can save thousands in energy costs every year.
In 2001, Bill Clements, then facilities director for Rockbridge schools, was overseeing the renovation and expansion of Fairfield Elementary School. It included installing a new heating and cooling system.
Clements had read about geothermal systems in trade magazines, then attended a seminar where John Garland, president of Spectrum Design, an engineering and architecture firm in Roanoke, spoke on the benefits of geothermal heat pumps in schools.
He was interested, and got county officials interested as well. They began talking to the folks at Spectrum, and eventually took a tour of schools in Chesapeake and Johnson City, Tenn., where they could see geothermal in action.
They liked what they saw.
“The more I talked and learned,” Clements said, “the more I was convinced it was a good way to go.”
The original architecture firm handling the renovation had recommended simply replacing the existing boiler and cooling tower, but the county was sold on geothermal. It spent about $815,000 for the labor and equipment.
“It was just a little bit more than $100,000 more than a conventional system would be,” Clements said. And some of that was offset by savings in other areas. For example, the money planned for the new boiler and mechanical room – things recommended by the project’s original architect, according to Garland – could be used toward the cost of digging the 100 300-foot wells.
“When you go to geothermal,” he said, “You don’t need the boiler and you don’t need the cooling tower.”
More importantly than the short-term finances, though, the county would also save in the long run by reducing energy costs dramatically – on the order of tens of thousands of dollars per year.
Clements expected it would take a while to recoup the investment. “We were hoping for a four- or five-year turnaround on it,” he said. Instead, “We recouped it in about three years.”
And the savings continue: “We doubled the size of that building,” he said, referring to the school. “We went from 30,000 to about 60,000 square feet.” But, he said, they’re using the same amount of energy as when it was half that size.
It’s all about “life cycle costs,” according to Garland – the long-term price you pay, as opposed to just the initial cost. “It makes sense to spend more up front if it’s going to reduce utility costs by more than that amount,” he said.
So when the county saw the results of the Fairfield Elementary “experiment,” officials decided to use geothermal systems in every school that’s scheduled for renovation, according to Garland.
So this year, Effinger and Natural Bridge elementary schools are sporting new geothermal systems. (Mountain View Elementary was also renovated, but the geology wasn’t suitable for a geothermal system.)
The county expect a return on those investments in the next few years. Further, Clements said, the system is environmentally friendly.
“You don’t have pollution in that you’re not burning any fuel, and you don’t have a chance for pollution because you’re not storing any fuel,” he said. “It’s what they call a green system.”
Clements has since retired from full-time work for the school system, but said he sees the decision to invest in geothermal paying off, especially recently.
“The higher fossil fuels get,” he said, “the better our system looks.”
How it works
Outside, the temperature can range from below zero to over 100 degrees. In the center of the Earth, it’s about 6,000 to 7,000 degrees.
But from about 5 to 500 feet underground, the temperature is consistent – between 52 and 56 degrees, year round.
A geothermal system takes advantage of that.
Water-filled pipes are placed in the Earth; in Fairfield Elementary’s case, about 100 of them, each in a 300-foot-deep hole.
In the winter, those pipes take warmth from the Earth and bring it to a heat exchanger where it’s used to warm the building. In the summer, the same pipes take heat from the building and “dump” it into the Earth.
“A heat pump is either extracting the heat from, or putting heat into the system,” explained Spectrum Design president John Garland.
But unlike a traditional heat pump that draws heat and cooling from the air, a geothermal system uses a “water-source” heat pump. Its source is always about 54 degrees – warm in the winter, cool in the summer – which makes it much more efficient.
Geothermal systems aren’t just for public buildings. Homeowners can have them too, and they don’t even have to dig 300-foot well holes.
You would need about 1,000 linear feet of cooling pipes to heat and cool a 3,000-square-foot home, according to John Garland, president of Spectrum Design.
But instead of three or four 300-foot-deep holes, a homeowner could have trenches dug just 5 or 10 feet below ground, “kind of like a septic field,” said Bob Tracy, chairman of Virginia Tech’s department of geosciences.
“There’s a big upfront cost of installing this compared to a normal heat pump system,” Tracy said, “but it reduces the running cost so much that payback is only a few years.”
In fact, according to Garland, although you might spend $12,000 to $15,000 to outfit a 3,000-square-foot house, you would probably recoup that in four to five years just in energy savings.