Speakers Demystify Groton's Geothermal Heat

This winter, Groton physics and engineering teacher Bert Hall brought three groups of speakers to campus to educate students and faculty about the design and engineering of the Schoolhouse expansion project.

After learning about the design process and use of 3D Modeling in the first two lectures, the final lecture, on February 19, focused on the project’s geothermal wells and ground-source heat pumps.

The Schoolhouse's new chilled-beam geothermal system represents the most current geothermal technology. It will be used for the entire Schoolhouse building complex, including the new Forum and science and math addition, and it will go a long way toward helping the School achieve its energy-reduction goals.

Three engineers who worked on the project, David Lamothe, Steve Sundius, and Rush Schmitt, spoke. Lamothe gave an overview of the closed-water system and explained that water is nine times more efficient than air in moving heat. In effect, the new system will provide air conditioning and heating to a building complex that is 50 percent larger with no increase in energy cost. The cost per square foot per year will be less than half the average for buildings of its size.

Lamothe showed pictures of the drilling of the wells, each 500 feet deep, under Groton's Circle. Each well supports a different circuit for heat exchange. Each circuit can be used to pump heat out of the building and into the earth for air conditioning, he explained, or to pump heat into the building from the earth for heating. The system connects to the building with plastic heat-fused pipes filled with a water/antifreeze mixture. The wells plus the heat exchange circuits cover half the area underneath the Circle, but there is no outward sign of their existence. Inside the Schoolhouse complex, the water-filled pipes become the “chilled beam” cooling and heating ducts.

Sundius and Schmitt described the engineering of the super-efficient ground-source heat pumps, which take advantage of the fact that the earth maintains a relatively constant temperature of 55 degrees year round. With the earth providing energy to heat up to 55 degrees, the temperature change needed to achieve a comfortable 70-degree environment is reduced to a mere 15 degrees, significantly less than a system faces if it must start from the outside temperature. Groton's system is hybridized; additional steam energy complements the system if temperatures are extreme.

Besides saving money, use of geothermal energy reduces the school’s carbon footprint by reducing consumption of fossil fuels. After the Schoolhouse expansion is complete next fall, teachers and students will access and analyze the information about energy use, turning the building itself a learning tool for renewable energy.—Bobbie Lamont, Science Department

Back