Frequently Asked Questions

Watch this Carleton Connects UMP webinar for more informaiton on the Utility Master Plan project. 

What is heat and what is a heat pump?

Students Anne Hamilton, Max Trostel, and Winston Goldwaite created two posters that easily explain what heat is and what a heat pump does. They also created a video that ties together the concepts of geothermal and physics:


What is the difference between a geothermal bore and a well?

Our geothermal bores are 6" diameter holes drilled into the earth and are quickly filled with piping and encased with grout. Aside from a few hours during and after drilling, these bores do not allow water to flow between the discrete aquifers that they are drilled through. Wells are open and allow groundwater at various depths to intermingle.

How long has geothermal technology been around?

Humans have used the Earth to cool and heat things for hundreds of years (think root cellars). Once below the frost line, the Earth stays at a constant 50-55 degrees Fahrenheit year round. Ironically, as the fracking industry has advanced, so has specialized drilling equipment and methods, making it easier and more economically viable to install geothermal systems.

Are there any known environmental impacts of geothermal?

The bores are drilled through limestone and shale bedrock and, because they are encased in concrete grout, they don't allow for water to flow between aquifers. The project is permitted by the Minnesota Department of Health and must meet their very strict guidelines. The bore fields are not expected to raise the local ground temperature by more than five degrees. With this new system, we are moving to a utility system that is more dependent on electricity and less dependent on natural gas burned on site. This opens the door to using more renewable energy like wind and solar which are known technologies that are becoming more mainstream.

Carleton is the first campus in Minnesota to install a district-energy scale geothermal heating system. Is this technology common in other states?

Only a few other campuses in the nation (Ball State University, Miami of Ohio, Grinnell) have installed geothermal systems on a campus scale as opposed to systems that serve only one building. While those few campuses were trailblazers with geothermal, Carleton will be the first to transition its entire utility system off of steam heating.

What is the timeline for the geothermal bore fields to be constructed?

The Bell Field bore field was completed in August 2017 and contains 95 x 510 ft horizontal bores. The Mini Bald Spot vertical bore field was finished October 2017 and contains 77 x 520 ft vertical bores. The Bald Spot will begin in June 2018 and contains 133 x 520 ft vertical bores. The full construction timeline can be seen here.

The Bald Spot will have 56 more wells than the Mini Bald Spot. How long will that take to drill?

That depends on many factors related to construction methods and weather. The Bald Spot drilling will begin as soon as drill rigs are available after Reunion 2018. The drilling team will have 2 -4 drill rigs that can each drill about one bore a day, provided weather and geological conditions cooperate. We are exploring various construction methods and tactics that might help to speed up the process, but we won't really know how long it will take until we have those conversations. The Bald Spot will definitely be restored for spring events, graduation, and reunion.

Will the Bald Spot drilling disturb any trees, pipes, or tunnels?

The Bald Spot bore field will be within the lower elevation center of the Bald Spot where the ice rinks are each winter. All of the tunnels and underground utilities are around the sides of this area, so drilling will not disturb them. We do not anticipate that any of the trees around the perimeter of the field will have to be removed.

What is the piping made of, how long will it last, and what is the maintenance?

The piping is made of heavy-duty PVC that has a warranty of 50 years and is expected to last decades longer. Each area has multiple valve and circuits to monitor its performance. Each bore is fully encased with concrete to protect both the water table and the piping.

Will the pipes be at risk of freezing?

No, they are buried well below the frost line where ground temperatures are a consistent 50-55 degrees year-round. But we will have alarms throughout the system to let maintenance staff know of any changes so we can quickly fix any problems that arise.

What will happen to the existing steam plant?

The current steam plant is where all of the campus's heating and cooling needs are met using inefficient and old steam boilers. The existing approx. 77% efficient steam boilers will be decommissioned in 2021 and replaced with 97% efficient hot water boilers. These will be used to supplement the geothermal heating system during our coldest winter months. There will also be room in the existing steam plant to add other technologies that can plug into our system, such as combined heat and power (CHP). The chillers and cooling tower that will supplement our geothermal cooling will also stay at the existing steam plant. Our steam plant operators currently monitor the plant 24 hours a day and with this new system, will no longer need to work around the clock.

How is this project different than the new science building?

The Integrated Science Facility will house the new geothermal system equipment in the sub-basement. This "East Energy Station" will operate in conjunction with the existing facilities building. For more information about the Integrated Science Facility, see the Facilities Website.

How will the heating systems change in the campus buildings?

Building on the east side of campus will be converted to run on 120 degree F hot water rather than their current setting of 180 degrees F. To accommodate the lower temperature, we need to add more surface area for the heating coils in the air handling units and the radiators in the rooms. In many buildings this simply means adding sections of radiation, but in some buildings the radiators will be entirely replaced. These are usually buildings where radiator replacements are due or buildings that are currently heated by steam but need to be converted to hot water. Hot water is a much more comfortable and controllable form of heat than steam.

Skinner Chapel is a good example of how this will work. It was renovated in 2015 from steam radiators to hot water radiators capable of operating on 120 degree water. Instead of small, very hot, radiators placed at spaced out intervals throughout the Chapel, there is now a larger radiator that spans the length of the room. This radiator is not as hot and heats the room like a large warm blanket, instead of the steam radiators which acted like lots of small, hot campfires spaced out throughout the room.