Hi Jason,
Regarding modeling the efficiency of equipment...
It depends on whether you're modeling a specific system for a specific building project, or if you're trying to model generalized performance, for example for research. I'll comment on the latter scenario. For generalized research purposes, where we don't know the exact heat pump system and configuration, my team has found that energy simulation results are too sensitive to many of the heat pump details in the energy model. Therefore, to avoid our results being overly-specific to one heat pump model and configuration we've done one of the following two things.

1.
We've output the annual heating and cooling demands from tour energy model, then applied the heat pump heating or cooling COPs in a spreadsheet. We've found the COPs from a published study with realized, weather-dependent, COPs (from representative climates and buildings)

2.
We've also done this with hourly performance, based on realized, weather-dependent COPs at different temperatures from representative field studies. For interpolation, we've calculated the maximum possible COP (based on the Carnot Cycle) for each time step, then scaled those values down to something more realistic, based on the results from the published field studies.

Hope this helps.
Best,
Holly

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Holly Samuelson

Associate Professor of Architecture

Harvard University | Graduate School of Design

www.hollysamuelson.com

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