How can I model an air cooled heat pump in openstudio?

asked 2021-03-27 05:15:12 -0600

wjsjch
107 ●1 ●6

updated 2021-05-20 17:36:34 -0600

In fact, what I hope to model is an air source heat pump water chiller/heater, producing chilled water and hot water in winter and summer respectively for HVAC purpose. I only find the module of air cooled chiller. And for heating, I have tried the central heat pump while 4 severe errors occurred. Thus I think it's a water-cooled type heat pump.

So I hope that someone can give me an instruction, telling me which kind of heat pump (for heating) in OS is an air-cooled one (no need of a condenser water loop). Thank you!

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answered 2021-03-27 20:45:07 -0600

Aaron Boranian

14100 ●81 ●24 http://bigladdersoftware.com/

updated 2021-03-27 20:55:39 -0600

It sounds like you want to simulate an air-to-water heat pump using the HeatPump:PlantLoop:EIR:Cooling object in EnergyPlus for a heat pump that produces chilled water while rejecting heat to air (likewise the companion HeatPump:PlantLoop:EIR:Heating object for producing hot water). You can read more about this EnergyPlus capability in this Unmet Hours post.

This was added to EnergyPlus in v9.3 which was released in March 2020, so you would need to use the OpenStudio Application v1.0.0 or later. The Notable Changes section doesn't mention adding this capability to the application, and neither does the release notes for OpenStudio Application v1.1.0. In the OpenStudio Application v1.1.0, it doesn't appear that the HVAC library includes this option -- just the water-to-air heat pump coil or the water-to-water heat pump coil (see below).

image description

If you wanted to stay in OpenStudio, you could write a measure using the OpenStudio SDK. However, the SDK does not include any methods related to this air-to-water heat pump object in EnergyPlus, so that is not an option either. According to this Unmet Hours post, the openstudio-standards gem has a method to apply a central air-to-water heat pump that might work for you. If not, you have two other options:

Export an EnergyPlus input file (IDF) from OpenStudio and manually edit to add this air-to-water heat pump object.
An alternative method is mentioned in this EnergyPlus feature request for the air-to-water heat pump:

Current work around is to use a heat pump water heater, which is really inteded for domestic hot water, along with an air-cooled chiller. This is an air-source central heat pump and differs from the existing CentralHeatPumpSystem in that it is water-source).

Both of those HVAC components are available in the OpenStudio Application.

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It's really hard to find the right one, and I was not sure whether it's OK to use the one for domestic hot water yesterday. Now, I think I can use it with ease under your instruction. Thank you very much!

wjsjch ( 2021-03-27 20:59:36 -0600 )edit

However, I don't know what is Water to Air HP used for. I have tried it, but no matter where I put it (either on the supply-side or demand-side), it tells me this component is not allowed to locate here. So weird, it seems that it's neither a producer nor a consumer. Maybe a bug? Or do I misunderstand it?

wjsjch ( 2021-03-27 21:15:03 -0600 )edit

Unfortunately, the heat pump water heater is also not allowed to be placed on the supply side of a water loop. Did I miss some key procedures?

wjsjch ( 2021-03-27 21:25:52 -0600 )edit

@wjsjch you shouldn't use any water-to-air heat pumps for this system -- that would be rejecting heat to a water condenser loop in order to heat /cool air (like a water-source heat pump or ground-source heat pump for zone air heating/cooling). This post covers adding the heat pump water heater to OpenStudio models in the application.