A down-to-earth way to heat schools

This appeared in the September 6, 2005 issue of the Roanoke Times.

trtlogoIn 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.

Home front

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.