Geothermal heating and cooling system to reduce greenhouse gas emissions in new UMMS building

Before the foundation is poured or the first piece of structural steel is placed for the new education and research building on the campus of the UMass Medical School in Worcester, work has started on a geothermal heating and cooling system that will reduce the building’s greenhouse gas emissions by 55 percent will decrease. percent compared to servicing its HVAC needs solely with the campus switchboard.

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Drilling boreholes (seen here) began on July 1 and is expected to continue throughout the summer. Once completed, the entire system of boreholes and pipe loops will be buried deep under the turf.

Geothermal systems work by circulating water through loops of pipes buried deep in the ground. The heart of the geothermal system for the new building is a series of 75 boreholes, each 15 cm in diameter and 150 feet deep, drilled into the bedrock beneath the campus greenery. Water circulating through a closed system of pipes in those holes will help heat and cool the new building. Drilling of a borehole began on July 1, and is expected to continue through the summer. Once completed, the entire system of boreholes and pipe loops will be buried deep under the turf.

“This is a major sustainability milestone for the Worcester campus,” said John Baker, associate vice chancellor for facilities management. “It’s a big step toward meeting our long-term decarbonization goals.”

The campus power station will supply the new building with power. The installation will also help to meet peak heating and cooling demand during the winter and summer months. Over the course of a year, the geothermal system will provide 88 percent of the heat for offices, labs, and education and public spaces, and 50 percent of the building’s cooling needs.

If the new building were served solely by the campus power plant, it would generate approximately 3,000 tons of greenhouse gas emissions annually. The geothermal system will reduce that carbon footprint by 1,660 tons per year, according to an energy analysis of the building conducted by engineering firm BR+A.

The geothermal system for the new building will exceed the latest “stretch” energy efficiency building codes and is aligned with the goals for new public buildings expressed in the state’s Executive Order 594 “Leading the Lead: Decarbonization and Minimization of the Environment”. Environmental Impacts of State Government” issued by Governor Charlie Baker on April 22.

Technically called a ground source hybrid heat pump system, the technology works on the same principle as a window-mounted air conditioner that blows air through pipes filled with a pressurized refrigerant to cool the air in a room and send the warm air out. . Now imagine if that window air conditioner sat on a turntable and could be turned on demand so that the cold air blows out and the warm air blows into the house. That is essentially how the geothermal heat pumps will heat and cool the new building.

A window-mounted air conditioner transfers heat from your home’s ambient air. A geothermal system transports heat energy stored in the ground. Once you are a few meters deep, the soil remains at a constant temperature all year round, about 55 degrees in our region. That’s one of the reasons a home’s basement is cooler than the top floors, even on the hottest summer days.

The constant level of underground heat – 50 degrees of soil, rock or even air contains a lot of heat – is captured by water circulating in U-shaped pipes inserted into each of the 75 boreholes. Hot water flows into the building and returns to be cooled in the ground.

The holes are 500 feet deep to give the water enough time in the ground to exchange heat. 75 boreholes are needed to supply the system with sufficient water.

An oil rig will use an impact head to move the rock and soil. The hole is lined with a steel casing and water is pumped through during drilling to flush soil and rock to the surface. The U-shaped tube is lowered and fixed in place with a special mortar designed to conduct heat energy efficiently.

A network of horizontal pipes will connect the boreholes to a series of heat pumps in the building. Water from the boreholes circulates through one side of the heat pumps, while a second closed system of water circulates through the other side of the heat pumps to carry chilled or heated water.

Nestled between each of the closed water cycles is a compressor coil filled with a refrigerant that exchanges the heat. Higher pressure in the coil raises the temperature. Lower pressure in the coil cools the water.

Every heat pump has reversing valves, which are able to change the flow of heat exchange back and forth. Almost every day, some parts of the building need heat and other cooling to maintain the right temperature. The flexibility of the system allows some heat pumps to operate in heating mode while others operate in cooling mode at the same time.

“The constant temperature of the ground is like having a head start to heat the building and a refrigerator to cool it down,” said Suzanne Wood, associate director, Sustainability and Campus Services. “With a relatively low input of electricity to power the pumps and compressors, it keeps the building in balance and drastically reduces the need to burn fossil fuels.”

Related story on UMassMed News:
Excavations started for new education and research building

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