Geoexchange System FAQs
The Geoexchange System
How does the geoexchange system work?
The geoexchange system will replace Swarthmore’s outdated steam system (which relies on natural gas combustion) to provide efficient renewable-powered heating and cooling to campus buildings.
The geoexchange system works on a yearly cycle. Heat-recovery chillers, powered by renewable electricity, remove heat from campus buildings during the summer and store the heat in the earth. The heat is then extracted and returned to heat the buildings in the winter.
At Swarthmore, this heat will be stored through the use of geoexchange wells, which are essentially deep vertical holes that contain a closed loop pipe system. As liquid travels through the pipes, it is either depositing thermal energy into the earth (summer) or extracting thermal energy from the earth (winter). With the help of the central geoexchange plant, this heated or cooled liquid is then sent to individual buildings across campus, where the HVAC systems transform that thermal energy into heating and cooling for our buildings.
What system is the geoexchange system replacing?
The geoexchange system will replace Swarthmore’s high-pressure steam system, which provides heat to campus buildings. Originally built in 1911, the steam system relies on the combustion of fossil fuels, mostly natural gas, to function. In contrast, the geoexchange system is a highly efficient zero-carbon energy system.
What is the geoexchange plant, and where will it be located?
The new Dining and Community Commons (DCC) includes space in the basement for a central geoexchange plant which will be the heart of the heating and cooling systems for the entire campus. The plant will house all the large equipment to run the geoexchange system, including pipes, wiring, pumps, tanks, heat-recovery chillers, and a sophisticated control system, though it won’t look like much is happening to the casual observer.
By integrating the plant into the DCC, the College will benefit from its centralized location, its proximity to the geoexchange well site, and the cost-savings compared to constructing a standalone plant. While the first phase of the plant is not expected to be complete until 2024, the Dining Center opened fall 2022 and Sharples Commons is expected to open in early 2024.
The Geoexchange Wells
What are the geoexchange wells and how do they help us heat and cool the campus?
The wells are essentially underground pipes with liquid running through them. The earth and constant temperature (50 degrees Fahrenheit) act as a thermal storage mass for heat extracted from campus buildings during summer cooling that can then be returned to heat the buildings in the winter. Currently the extracted summer heat is expelled to the atmosphere through evaporative cooling. Transitioning to this method will also save the College millions of gallons of water annually that is currently used for evaporative cooling.
Where will the wells be installed?
All of the wells will be installed underneath Parrish Lawn. Well drilling will occur in phases to meet the geoexchange load as campus buildings are converted to low temperature hot water heating over the 13-year plan implementation. If the College expands its building space in the future and needs to increase heating and cooling capacity, an additional well field zone will be sited underneath the Ben West parking lot.
When will the wells be drilled?
The first phase of drilling, on the field in front of Mertz Hall, was completed in October 2023, and we are now in the process of restoring the field to an organic lawn. To support the reseeding and regrowing process, protective fencing will remain in place through spring and summer 2024. The area will be seeded with a winter rye grass to stabilize the soil and provide natural nutrients until it can be graded and sown with the College’s specified organic lawn seed mix. The lawn should be restored for full use by the start of the Fall 2024 semester, so long as there is a reasonable summer growing season.
How many wells will there be, and how large?
The wells will be 800 feet deep and approximately 6 inches wide. There may be up to 900 wells across 200,000 square feet.
What is the environmental impact of the well drilling?
During the drilling of the geoexchange wells underneath Mertz Lawn, as many as six drilling rigs were operated regularly to dig 350 800-feet deep, 6-inch wide wells. Based on the number of rigs, fuel amounts, and hours in operation, the emissions associated with this phase of the College's energy plan are estimated to be 940 metric tons of carbon dioxide equivalents — equivalent to 6% of the College’s overall emissions in fiscal year 2022, and to 18% of the College’s average annual emissions related only to natural gas combustion for steam generation.
Based on these estimations, the emissions associated with the geoexchange well field drilling are equivalent to the College running the natural gas steam plant for approximately 66 days, meaning the emissions payback for this project once the steam plant is shut down is a little over two months. This first phase of geoexchange wells supports the College’s transition to renewable energy and by allowing us to shut down the natural gas combustion steam plant as quickly as possible.