Cold Climate Air Source Heat Pump Field Assessment
Ben Schoenbauer, Dave Bohac, P.E., Martin Kushler — Jan 2015
The project team finished installing ASHPs at all six locations and will monitor through the next heating season. Three of the heat pumps were installed prior to last heating season and researchers have already begun to analyze this data, which they presented at the 2016 ACEEE Summery Study in August. Full project update
Why this research is needed
High efficiency technologies like air source heat pumps (ASHPs) have significant potential to improve space heating efficiency and reduce energy costs for houses in cold climates where natural gas is unavailable. ASHP technology has been available for many years, but technological limitations caused concern about efficiency and reliability during the colder portion of Minnesota winters.
The efficiency and capacity of older ASHPs dropped significantly for outdoor temperatures below 40°F. The newest generation of ASHPs can now operate down to 0°F to -13°F. The efficiency of these technologies in moderate climates is two to three times more efficient than standard electric heating systems, but there is less experience with the use of these systems in Minnesota’s colder climate. Monitored field performance tests will help confirm the operation of newer generation ASHP technologies so that they can be confidently included in Minnesota's utility Conservation Improvement Program (CIP).
Project process and expected outcomes
IX research project staff will install ASHPs in four to six occupied Minnesota homes where natural gas is not available. The existing furnace will be left in place to serve as a backup to the ASHP during colder outdoor conditions. In addition, we will alternate between furnace and ASHP operation throughout the heating season to compare energy use of the two systems during milder conditions. Monitoring equipment will measure the ability of each system to meet the space heating load. The annual energy use and contractor installation cost will be used to determine cost effectiveness. Occupant comfort and acceptance will be evaluated from monitored space temperatures and occupant surveys.
The results from the field study will determine ASHP savings potential and help to facilitate the design of CIP (Blog on ASHP and CIP). The project will help determine the house characteristics and existing system types that are best suited for installation of ASHPs. While the primary analysis will be based on replacing electric resistance heat, we will also assess the policy and program implications of reducing delivered fuel consumption.
*This project supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program. And with co-funding by CEE in support of its nonprofit mission to advance research, knowledge dissemination, and program design in the field of energy efficiency.
Photo credits: Drew Domkus, Minnesota Power