The objective of this effort is to leverage existing geothermal district heating and cooling technology (GDHC), in conjunction with underground thermal energy storage (UTES), to enhance thermal energy resilience in cold regions installations. The goal is to develop a system that will result in cost savings and that will support the transition towards NetZero emissions.

GDHCs integrate diverse energy loads to optimize overall system efficiency and can be augmented with other renewables (e.g., solar). Traditional heating and cooling systems are linear, with a producer sending hot or cold temperatures to a consumer, whereas GDHC systems allow rejected hot or cold temperatures to be used. Long-term energy extraction from the shallow subsurface in cold climates with unbalanced heating and cooling loads can lead to lowering of available thermal energy and less efficient operation over time. The introduction of underground thermal energy storage can mitigate the degradation in subsurface energy storage and improve efficiency of the GDHC. Similar configurations have been proven in temperate environments (e.g. ESTCP-funded UTES at Marine Corps Logistics Base in Albany, GA), and individual components of such a system have been validated in cold climates (Garber-Slaght and Keays 2014; Garber-Slaght et al. 2017), but a holistic demonstration in cold climates has not been pursued. This effort will adapt and optimize design, management, and operations of GDHC systems for cold climates (i.e. heating dominant climates). The project team will also perform a model demonstration for an optimized GDHC UTES in Fairbanks, AK, with the goal of demonstrating the efficiency of such a system in cold temperatures.

There are nearly one hundred U.S. Air Force, U.S. Army, U.S. Navy, and U.S. Coast Guard installations in cold regions globally. The cold region GDHC and UTES demonstration will include design and implementation of a cost effective thermal energy system that will support the transition toward NetZero emissions. Payback analysis is site dependent, and the selected site, Fairbanks AK, is expected to be on the longer end of a payback of approximately 10 years. Additionally, since GDHC runs on electricity, they can easily operate on a backup power system, unlike traditional district heating systems that cannot be similarly backed up in an efficient and cost-effective manner. This study will demonstrate the feasibility of cold regions installations thermal energy systems (for which a failure event can result in threat to life, infrastructure, and mission) that can be less reliant on off-base supplies.