For energy, Noble and Greenough goes geothermal
School officials praise system, which harnesses heat generated beneath the surface of the earth
Noble and Greenough School in Dedham is harnessing the energy beneath the earth's surface to heat and cool one of its buildings.
It is a move that saves money in the long run and coincides with the school's efforts to consider the environment in the way it runs its campus and its classrooms, school officials say.
The school is using geothermal energy -- a source more often associated with shooting geysers or bubbling sulfur pools out west -- to provide heat and air conditioning for its middle school building. The system cost more than a conventional setup, but will save the school $17,000 a year, making up the difference in six years and ringing in savings from then on, the officials say.
The geothermal system involves a series of three wells drilled 6 inches wide and 1,500 feet deep. At this depth, the earth's energy warms the well water to a constant temperature of 50 to 60 degrees. The heated water is pumped out of the wells and into a heat exchanger. In the winter, the heat exchanger takes the heat out of the water, pressurizes the heat to raise its temperature even more, and uses it to warm the cold air in the building. In the summer, the heat exchanger absorbs the excess heat from the air, blows the newly cooled air back into the building, and discharges the unwanted heat back into the earth.
"It's like a big straw we have in the well," said Tom Perry, the director of engineering services for Shawmut Design & Construction, which managed the construction of the project. "It sucks water out and uses it in the building through these ground source heat pumps that either cool or heat."
Students returning Tuesday will hardly notice a change. The ventilators used in the old system will be gone. All that's seen of the well on the surface is a single manhole cover.
"The geothermal wells are underground, so the kids probably won't even notice a difference," said Steve Ginsberg, the school's business manager.
Zaurie Zimmerman, the main consultant on the project, said the middle school building needed a new heating and cooling system and officials decided to go geothermal because the price was right and the technology fit the school's commitment to "go green."
"We said, 'This is such a no-brainer we don't even want to discuss it anymore,' " she said.
This is the school's first geothermal project, and if the process goes well, Zimmerman said they would consider the same procedure for other buildings on campus.
While geothermal heating and cooling systems were first introduced more than 30 years ago, recent improvements in materials, equipment, and installation procedures have made the system more attractive to implement, according to the Geothermal Heat Pump Consortium. Among the buildings in Massachusetts that have gone geothermal are Trinity Church in Boston and the Fessenden School in Newton.
The geothermal system at Noble and Greenough cost $723,000, which was about $100,000 more than a traditional heating, ventilating, and air conditioning system. But the annual savings made the geothermal approach more appealing.
"Retrofitting an existing building is complicated with any system," said Zimmerman, "so when we looked at the two approaches, it was clearly the favorable one."
Aside from any financial reasons, Ginsberg, the business manager, said the installation of the geothermal wells correlates with the environmentally friendly philosophy of the school. Ginsberg said the school has positioned itself on a course to become as "green" as possible.
"As we build, we're going to be very aware of how we could do it the `more green' way," he said.
Other such projects at the school include waterless urinals and double pane glass that's used to trap more heat in the winter so less fuel is needed.
The school also offers many different classes on environmental issues, and one of the school's overall goals is for its students to graduate with a real understanding of why going green is important and what they can do individually to make a difference, he said.
The geothermal system "is a good, practical way to show the school's committed to it -- not just teaching it, but practicing it as well," Ginsberg said. "It's more than just putting in a geothermal well and saying we're doing good things. We're educating future leaders, and that's important to understand."
Zimmerman said that, when compared with other energy saving systems, such as wind turbines or solar panels, geothermal wells cost less to install and have a shorter payback period. Companies interested in "going green" are often dissuaded from purchasing a solar panel system because of how long they'd need to remain in the building to start seeing benefits -- sometimes as long as 25 years, she said.
One criticism of the geothermal process is that the system does not operate with 100 percent renewable energy. Thirty percent of the energy used to run the pumps is electricity, making the school ineligible for federal grant money that's specifically for 100 percent renewable energy sources.
But, Zimmerman said that with the other systems an average person would need federal subsidies to be able to afford them, while the geothermal system is cheaper and more reliable from the beginning.
"Solar panels glisten in the sun," she said. "But they are more like decorations than being cost-effective and saving energy. Geothermal wells are a humble and hard-working system, and there's no reason for people not to consider it."
Sara E. Jacobi can be reached at SJacobi@globe.com. 