Geothermal Energy 
Ground Source Heat Pumps
Ground source heat pumps (GSHPs) use the earth’s constant temperature to provide heating, cooling, and hot water for buildings. During the winter, the system uses the earth as a heat source to heat the building. In the summer, it uses the earth as a heat sink, where extra heat from the building is deposited. The heat is transferred through a system of pipes and refrigerant. Waste heat can be used to heat hot water.
There are two types of ground source heat pumps, closed loop and open loop systems. Closed loop heat pumps use the earth as the heat source and heat sink and has antifreeze in the loop water. Open loop systems use a surface or underground water source as both the heat source and heat sink.
Benefits
Ground source heat pumps:
- Use less energy than conventional HVAC systems & reduce GHG emissions
- Can be more efficient than conventional heating systems
- up to 44% more efficient than air source heat pumps & 72% more efficient than electrical resistance heating
- Lower energy costs by 20 – 50%
- Lower maintenance costs due to fewer moving parts and because equipment is not exposed to weather
- Are aesthetically more attractive- no cooling towers or HVAC equipment on roofs
- Are quieter
Water to water heat pumps at Harvard
Learn more about the ground source heat pumps at Harvard.
Engineered/Enhanced Geothermal Systems
Engineered/enhanced geothermal systems (EEGS) (also called hot dry rock) technology takes advantage of the high temperatures found miles deep in the earth. Cold water is pumped deep into the earth (via bore holes), becomes superheated as it flows through fractured rock, comes back up through additional wells, and the heat is extracted from the water to create electricity at a large scale power plant. The cooled water is reinjected into the first well to form a closed loop circuit. Hot dry rock technology was first tested at the Los Alamos Fenton Hill, New Mexico site in the early 1970s and has been tested around the world since then. EEGS is an exciting technology because of the vast amount of heat deep in the earth, but currently, the costs are very prohibitive. Recent drilling in Switzerland accidentally triggered a 3.4 magnitude earthquake.
QRAC well access
Fact Sheets & Powerpoint
Interested in installing a GSHP at Harvard? Our GSHP fact sheet goes through the basics of what you need to know, including lessons learned. A more detailed lessons learned powerpoint is available here.
LEED
Buildings can obtain LEED points for using renewable energy on-site. More information is available on our Renewable Energy and LEED page.
More Information/Sources
International Ground Source Heat Pump Association
Hot Dry Rock Geothermal Energy Technology
International Geothermal Association
MIT: The Future of Geothermal Energy (download individual chapters here)
Hot Rocks in Earth's Crust Raise Hope for Clean Energy, Quake Concerns
1 Francis Avenue:
Home to Harvard's first ground source heat pump