PERFOMANCE CONSIDERATIONS FOR GROUND SOURCE HEAT PUMPS IN COLD CLIMATES

Remote, cold climates present challenges to finding safe and affordable space heating options. In Alaska, residential ground source heat pumps (GSHPs) have been gaining in popularity, even though there is little research on their long-term performance or their effect on soil temperatures. The extended heating season and cold soils of Alaska provide a harsh testing ground for GSHPs, even those designed and marketed for colder climates. The large and unbalanced heating load in cold climates creates a challenging environment for GSHPs. In 2013 the Cold Climate Housing Research Center (CCHRC) installed a GSHP at its Research and Testing Facility (RTF) in Fairbanks, Alaska. The heat pump replaced an oil-fired condensing boiler heating an office space via in floor hydronic radiant piping. The ground heat exchanger (GHE) was installed in moisture-rich silty soils underlain with 0 degrees C permafrost. The intent of the project was to observe and monitor the system over a 10-year period to develop a better understanding of the performance of GSHPs in sites with permafrost and to help inform future design. As of this writing, the heat pump system has been running for eight heating seasons. The efficiency in those eight heating seasons has been variable with ups and downs that have been difficult to explain. This paper seeks to understand the variability in performance as well as make recommendations for GSHP use in other cold climates.