Within a few years of its installation, the geothermal system serving Stead Hall and the Loder Building experienced performance problems, including very low heat transfer to the geothermal field located under a parking lot. Steam heat exchangers were being used to inject heat into the system to handle demand in winter—an inefficient work-around. In addition, a contractor had discovered that the system’s two sealed geothermal vaults had both filled with water, and that pipe fittings were so deteriorated as to raise the strong possibility of failure. The original geothermal system installer had gone out of business.
- GBA investigated three options: maintaining the system and field with repairs, including vault repairs costing at least $75,000; maintaining the system and field with more significant repairs and upgrades, including additional heat injection and heat rejection capacity; and abandoning the geothermal field while maintaining a heat pump loop within the buildings, adding heat injection and rejection equipment (or connecting to the Northwestern University campus infrastructure for steam and chilled water).
- The investigation included locating and reviewing existing documentation; calculating theoretical capacity; conducting a heating/cooling block load calculation; reviewing BAS trending; and assessing the adequacy of the systems to meet connected building loads. An assessment of the steam-to-hot water heat exchanger capacity was made to see if campus steam could be used, as well as calculations of sizing and footprint of chilled water equipment that would be needed if the geothermal system were abandoned and campus chilled water was used.
- The firm’s final report discussed five potential upgrade options, and ultimately recommended that the client should either connect to the campus chilled water system, or install a fluid cooler on the Loder Building roof to provide adequate heat rejection for both buildings (using existing heating capacity via steam converters and circulation loops). GBA recommended abandoning the geothermal field due to the high estimated cost of implementing repairs (more than $450,000).
- GBA subsequently provided plans and specifications for installing a closed-circuit fluid cooler atop the Loder Building. The system was completed in 2017.
