An annual performance comparison of various heat pumps in residential applications

The overall goal of this work was to compare the performance of five heat pump systems to ultimately identify the residential applications where they are most suitable. These included ducted single-speed, dual-speed, and variable-speed systems, and two ductless mini-split variable-speed systems. The analysis was based on mathematical models of the equipment, simulated in a validated building energy simulation tool called TRNSYS. A total of 480 combinations, derived from the equipment types, eight unique climates, and twelve homes varying in style, construction, and efficiency, were developed and simulated. The results showed the equipment generally following trends according to published or proposed ratings. The most appropriate applications for each heat pump were identified based on comfort, and how climate, equipment capacity, auxiliary heat, and other factors impact SEER and HSPF. Overall, the comfort analysis showed relatively indistinguishable results in term of a percent persons dissatisfied metric but had more meaning when compared to relative humidity statistics. Climate had a significant impact on SEER and HSPF results. Average SEER levels were between 13 and 27% lower than expected. However, for HSPF, there were many instances where applied HSPF exceeded model calculated HSPF at rating conditions. When applied HSPF included auxiliary heating, minimum and mean values decreased significantly. The average minimum and mean performance reduced by 27% and 17%. In terms of equipment sizing, a decrease in performance as the capacity increased in sized was seen as expected for the ducted systems and it was discovered that over-sizing the variable speed system penalized performance, yet over-sizing one of the mini-split systems according to its published capacities improved performance. Each simulated combination from lower-rated heat pumps were compared to the same combinations of higher-rated heat pumps in an effort to determine where lower-rated equipment more closely matched higher-rated equipment. The majority of the differences between ducted equipment comparisons were in home size and efficiency whereas when compared to mini-split systems, climate choice and home efficiency levels were important