EnergyPlus Air to Water Heat Pump

Since E+ still doesn't have this object (unless I'm missing something?) we've borrowed the method from Sefaira here to use a little EMS code to calculate an efficiency, and then assign that energy to an exterior light. I'm assuming they chose an exterior light because it was pretty simple and many building don't have them modeled, but it's causing some issues with the meter files as the boiler energy still shows up (and in this case I can't just remove that variable, since I need the output meters to be consistent throughout many models).

So my questions:

1 does anyone have any better/more direct methods of modeling air source HPs?

2 if not, is there a way to either zero out the boiler energy via EMS, or just adjust it to not use the exterior light at all? From digging around it seems like it's not really possible to just change the energy of an object like this (for obvious reasons I'm sure).

Thanks

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bbrannon4

asked 2021-08-29 21:49:37 -0500

4.4k

__AmirRoth__

updated 2022-02-23 12:18:45 -0500

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@bbrannon4 would the HeatPump:PlantLoop:EIR:Cooling (and Heating) objects with the Condenser Type input field set to "AirSource" work for your project?

Aaron Boranian (2021-08-30 09:35:47 -0500) edit

Potentially, though the constant volume assumption is likely a bit unrealistic so I'll have to test it. And am I correct that this issue has been resolved but not released yet (mine will be auto-sized)?

bbrannon4 (2021-08-30 09:47:10 -0500) edit

I'm gonna make an answer post with some ideas soon.

Aaron Boranian (2021-08-30 13:05:24 -0500) edit

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EnergyPlus did add the HeatPump:PlantLoop:EIR:Cooling (and Heating) objects in version 9.4, meant to cool or heat a water loop by transferring heat to air or water. Some ideas on implementing this:

The objects are currently constant flow, so you can use EMS actuators like Pump Mass Flow Rate or System Node Mass Flow Rate Setpoint to change that to variable flow
You are correct that there was an issue found related to autosizing flow rates and capacity. You can find more discussion on this topic in an Unmet Hours post. This issue has been fixed and merged into the source code, but won't be available until the v9.6 release expected in end of September 2021. If you don't want to wait for that public release, you can install a pre-release version that's been built by the EnergyPlus development team.