Climate commitment and carbon reduction declarations by progressive higher education institutions have driven ground source geothermal space heating and cooling systems into rapid evolution. During our decades as geotechnical and environmental consultants to education clients, we’ve seen the changes firsthand and applaud the rapid progress in utilizing geothermal systems.
The first geothermal systems were “designed” by well drillers and heat pump vendors using rules of thumb. As larger-scale systems came into demand by clients, vendors applied the “multiplier” approach, using the same single-building models and multiplying them to meet the new peak loads giving little consideration to long-term well field performance, well field balancing, bleeding aquifers, permitting and other important issues.
A higher educational facility in the mid-Atlantic applied initial “rules-of-thumb” and estimated their well field at 25 wells per building. A careful engineering analysis utilizing a temperature management system comprised of geothermal heat pumps and conventional system components to provide heating/cooling 90 percent of the energy and carbon savings could be achieved by installing six wells per building.
As the market for larger geothermal systems arose, mechanical engineers and geotechnical professionals began to team up to deliver more robust solutions to institutional owners. Their evolved approach took into account variables such as groundwater flow, soil and bedrock conditions and more robust building modeling. A characteristic of this phase in geothermal’s education was, however, to design systems based on peak loads, relying on the geothermal system for 100% of the heating and/or cooling load. Long-term financial performance projections were unattractive under these scenarios, which effectively shelved what would otherwise have been great applications, if viewed in a slightly different manner.
Yale University was planning a new residence quadrangle with a peak cooling requirement of 800 tons. The university aimed to achieve significant carbon footprint reductions on this building complex but space was limited, subsurface conditions were challenging and permitting was difficult. If the geothermal well field was designed to handle peak load, the number of wells could have exceeded 300. Haley & Aldrich applied our “Smart Sizing” approach to load modeling to better understand the yearly building thermal load profile. We determined that just 50 wells could achieve a 40 percent reduction in carbon footprint, thereby meeting Yale’s goals.
Stewardship of natural resources influenced Fairfield University to consider its options when planning for a new Jesuit Housing project while minimizing its carbon footprint. The building’s cooling loads were much larger than the heating loads, which led to an original geothermal well field design of over 45 closed loop
wells, which the constrained site would not accommodate. By adding an integrated temperature management system, the well field size was reduced to 10 closed loop wells that met both the university’s budget and its carbon footprint reduction goals.
At Haley & Aldrich, our slightly different view of geothermal applications led to our “SmartSizing” engineering design approach. We use “SmartSizing” to optimize geothermal well field size and its contribution to a district geothermal application. Our approach evaluates the complete system design which is comprised of geothermal and conventional system components. In our experience using more advanced integration and districting, well field sizes have been reduced by up to 80% while still maintaining up to 90% of efficiency gains. Using the “SmartSizing” approach, we have been able to manipulate numerous variables in the system design to achieve an optimal solution that we like to call the “geothermal sweet spot.”
For Stanford University, initial engineering evaluations arrived at the conclusion that its well field could be as large as 800 wells for a district-level geothermal system. “SmartSizing” modeling showed that the well field size could be reduced to 480 wells, saving approximately $3.2 million, while meeting the project performance goals and metrics.
After decades of geothermal design experimentation, we are beginning to see the emergence of sound and effective alternatives to standard industry practices. Advances in well field configurations are occurring simultaneously with advanced central plant configurations that utilize ground source geothermal. These integrated systems have the potential for significant carbon footprint reductions and energy efficiency improvements and should be one of the options colleges and universities evaluate as part of their overall climate action plan goals.
Ground source geothermal is truly getting a higher education. The design approaches, integration methodologies and modeling tools that can be applied are improving in response to marketplace demand for more robust, reliable and effective solutions. Geothermal solutions are indeed growing up and can offer college and university campuses a significant opportunity to achieve their strategic energy and carbon reduction goals.
