Geothermal is often overlooked as a renewable energy source, but at the University of Illinois, multiple organizations and campus units are championing it as a solution to meet clean energy goals. Geothermal energy systems take advantage of the stable temperatures underground to heat and cool buildings. In the winter, fluid in underground pipes absorbs and carries heat stored underground to a building, while in the summer, pipes carry heat away from the building and into the ground, thus cooling the building.
In April 2021, the largest geothermal energy system on campus became operational to condition the new Campus Instructional Facility (CIF). The heating and cooling capacity of the shallow geothermal energy system is based on 40 vertical borehole heat exchangers that circulate fluid from 100 meters underground to CIF to maintain steady indoor temperatures throughout the year. U of I Facilities & Services expects the CIF geothermal system will reduce the building’s energy consumption by 65% compared to the energy use of a building with a traditional heating and cooling system. So far, the system has successfully met the majority of CIF’s heating and cooling demand, but operational testing is still underway to optimize the system.
John Zhao, a Ph.D. student in Agricultural and Biological Engineering, has focused his research on holistically evaluating the performance of the CIF’s energy system by modeling it with commercial software. Conventional techniques for determining energy efficiency in buildings with geothermal systems include measurements of electricity reduction, carbon emissions, and the coefficient of performance (COP). Zhao takes this process a step further by examining how geology and the flow of ground water impact the system’s performance. He contends, “we need to add more complexities into the system so that we can accurately predict and analyze the performance.”
Installing a geothermal energy system is no easy feat; just the process of drilling 100-meter-deep boreholes and installing heat exchange loops can take months. According to Zhao, one of the university’s greatest concerns regarding new geothermal infrastructure is land availability for drilling; “even though the land can become parking lots or athletic fields afterward, (the installation) still requires a lot of time, which could inconvenience campus operations.” Along with land availability, the existing underground infrastructure (pipes and utility lines) must be considered when planning to drill. Adding to this complexity is the fact that borehole heat exchangers cannot simply be located wherever it is easiest to drill. Engineers must determine the optimal flow rates of fluid in the geothermal loops to avoid wasting energy by designing an optimal spatial layout for the boreholes.
While many issues remain to consider, the installation of geothermal energy systems has become more economically feasible for the university. Andrew Stumpf, an Associate Quaternary Geologist with the Illinois State Geological Survey, postulates that the recent passage of the Inflation Reduction Act will “supercharge the campus” to increase geothermal energy use. “Previously, tax credits for geothermal energy were only available to entities that paid taxes,” which excluded universities, municipalities, and nonprofit organizations. Under the Inflation Reduction Act, the university is now eligible for the 30% base credit to install geothermal energy, which significantly reduces the up-front costs of implementing a new geothermal system. The university is eligible for additional 10% bonus credits if domestic materials are used for its construction and if prevailing wage requirements are met.
Said Zhao: “Right now I don’t see any F&S proposals for new geothermal energy projects on campus, but I believe the (Student Sustainability Committee; SSC) would love to see projects like that.” SSC has contributed funds to many renewable energy projects, including Solar Farm 1.0 and the CIF geothermal system. Zhao encourages students to submit proposals for future geothermal projects.
The Illinois Geothermal Coalition (IGC) is another resource for those looking to implement geothermal energy on campus and beyond. The new coalition is a collaboration between the University of Illinois, corporations, nonprofits, and geothermal professionals. Stumpf, an IGC principal founder, said “our mission is to promote the wider adoption of geothermal energy in Illinois and the U.S. Midwest, which includes campus … (and) to provide expertise and information so that people can consider geothermal energy systems as an option.” With the creation of the IGC, Facilities & Services has access to experts from across the nation for advice on geothermal projects on campus.
With the success of the CIF geothermal system and the development of the IGC, the future of geothermal energy looks bright. Still, it is an oft-overlooked form of renewable energy by the public. The main components of a geothermal system are located underground, while solar panels and wind turbines can be spotted on rooftops and in fields. According to Stumpf, geothermal energy systems are more efficient than solar or wind energy because their performance is not dependent on weather conditions. An added benefit is that materials used for geothermal systems are primarily sourced domestically, while components of solar and wind installations are imported.
The lifespan of geothermal systems is impressive as well: “I don’t know of any systems that have totally been retired because the boreholes are expected to last for over 50 years,” Stumpf said. “Typically, the first equipment that needs to be replaced is the geothermal heat pump that is located in the buildings.” High-density polyethylene (HDPE) pipes used for in the borehole heat exchangers are extremely durable and resistant to chemical degradation. Maintenance of a geothermal energy system is comparable to maintenance of a natural gas furnace for heating and an air conditioner for cooling, but geothermal heat pumps perform both heating and cooling functions.
The biggest challenge to adopting geothermal is the high upfront cost of installation, but both Zhao and Stumpf suggest there are ways to address the issue. “When installing single residential or building-by-building geothermal energy systems, the cost is great, but when these systems are upscaled to neighborhoods and multiple buildings, the economics behind are much better,” Stumpf said. He recalls a neighborhood in Austin, Texas, called “Whisper Valley” that does just that; each house has solar panels and is connected to a community geothermal energy system that provides the entirety of the heating and cooling. Along with the implementation of community energy systems, Zhao explains that expansion of existing geothermal systems by adding additional borehole heat exchangers is more practical and cost effective than creating new, separate systems. Ultimately, a “district-based” geothermal system is much easier to manage and maintain than many individual systems.
Don’t be surprised if you begin hearing more about geothermal projects on campus and in Illinois thanks to the work of the IGC and students like Zhao. The increased affordability of geothermal and accessibility of educational resources will boost awareness of this renewable energy source. This fall, the IGC plans to publish an interactive webpage to describe the potential of geothermal energy in Illinois and outline its environmental benefits and positive impacts on workforce training and economic development. Students interested in learning more about geothermal energy are encouraged to read about our past geothermal Campus as a Living Laboratory projects and to get in contact with the IGC.
— Article by Lucy Nifong, iSEE Communications Intern