PX-25-C006 - Latent Cooling Loads in Cold Climate Heat Pumps and Implications to Unit Sizing ✓ Most Recent

https://doi.org/10.63044/s25lat06

Next-generation heat pumps are poised to provide an energy efficient alternative to traditional space heating in homes, especially in colder climates. These cold climate heat pumps (CCHPs) could help reduce heating energy and utility bills in American households in cold climate regions. Field demonstration and validation of this technology are necessary to resolve barriers and develop best practices for ensuring success. The U.S. Department of Energy launched the CCHP Challenge in 2021 to accelerate the development of next-generation air source heat pumps, focusing on residential, centrally ducted heat pumps that are 2-5 tons in capacity.

Among the logistical and technical challenges that heat pumps face in cold climates is the difficulty in sizing units to provide both sufficient heating and cooling based on the size of the home, insulation level, and other characteristics of the home that affect thermal demand. Heat pumps have been traditionally sized for cooling loads, but new guidance around sizing heat pumps for heating loads is beginning to emerge to help reduce the size of auxiliary heat elements in colder climates. In addition to optimally sizing the heat pump for heating and cooling, another factor that needs consideration is the latent load on the heat pump coil in humid regions. More specifically, during cooling season, the heat pump unit must be able to adequately condense out moisture to avoid indoor air quality and moisture issues related to high humidity.

The field validation aspect of the CCHP Challenge comprised 23 pre-commercial CCHP units installed in real homes in North America along with a comprehensive data collection and monitoring system of sensors and loggers. This paper presents the results of 18 of the units with sufficient summer data showing the measured latent and total cooling output during the cooling seasons, how that compares to the winter heating output, and the implications on sizing guidance for heat pumps. We compare the drier climate sites to the more humid sites to evaluate how geographic region may impact the performance of CCHP units. The results of this research can help practitioners in properly sizing units for realistic heating and cooling loads, which will help to understand the potential efficiency and grid impacts of the adoption of the next generation of heat pump technology.

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