Hanson worked with the Illinois Army National Guard (IANG) energy manager and Geothermal Engineering Inc. to design a hybrid geothermal system with vertical closed-loop wells and a dry cooler for the IANG Adjunct General’s Office building. For 10 years, funding restraints kept the staff of the Department of Military Affairs, which occupies the building, from replacing the facility’s underserving HVAC systems. Hanson completed a grant application that resulted in a $1.2 million Department of Energy grant for the client to replace the boiler/chiller equipment in the 74,000-square-foot building.
The project team had previously developed a concept for heating and cooling the building with an innovative geothermal system using mine water trapped within the Panther Creek Mine, located approximately 200 feet below the building at Camp Lincoln. The project included a study phase that evaluated the feasibility of using the abandoned coal mine water as the geothermal heat sink. The project would have been the second of its kind in the U.S. and was anticipated to reduce the geothermal well field cost by a factor of five times compared to a vertical closed-loop system; however, the mine contained insufficient water upon final investigation, so the project team designed an alternative hybrid geothermal system.
The project consisted of replacing the existing 54-ton air-cooled chiller serving the north portion of the building (28,960 feet squared) with new water-to-water heat pumps and dry cooler and connected this equipment to a new geothermal well field designed to serve the south and north sides of the facility. The heat pumps also supplement the existing boiler. The geothermal header pipe was extended to the southside mechanical penthouse and capped for future use. Metering was installed on the new, northside equipment to meet Department of Energy metering requirements. The northside air system was tested and rebalanced. Southside HVAC system improvements using the same well field are planned when funding becomes available in the future.
The building’s energy needs are heavily cooling-dominant, and the use of the dry cooler for supplemental cooling allowed the downsizing of the well field to the available land and reduced the installation cost. It was connected to the back-feed part of the existing HVAC system using water-to-water heat pumps. A 7-ton geothermal water source variable refrigerant flow (VRF) system was installed to condition the Joint Operations Center, which had the most space comfort issues. The system was designed with the intent to replace the interior HVAC with geothermal VRF system in a future project. In addition, the entire building automation system was upgraded. Hanson also performed a retro-commissioning study for the project.
"Hanson was instrumental in the Illinois National Guard receiving this grant for a geothermal system for our headquarters building and has been with us every step of the way. This building is one of our top two energy users, and we are expecting significant energy savings, as well as a significant improvement in the comfort level, in the building. Hanson has been a trusted partner who has worked diligently to help us see this complex project through to completion. They really understand geothermal and the unique needs of the guard." — LTC Craig Holan, Chief, Design & Projects Branch, CFMO Directorate