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Modelling a gas absorption heat pump in EnergyPlus

asked 2015-03-04 02:08:54 -0500

updated 2015-11-08 11:11:09 -0500

I would like to model a gas absorption heat pump and have run into a problem. My first approach was to model it as a regular air-to-water heat pump WaterHeater:HeatPump object, and set the fuel to NaturalGas. I didn't get very far with this since EnergyPlus throws an error if the COP is too low. The absorption heat pump I'm modelling will have a COP of between 1.15 and 1.25 which is low enough to fail.

So my second approach was to search for gas absorption in the documentation, which turned up ChillerHeater:Absorption:DirectFired - link. This looks like it may be a possibility, but it's set up as a chiller which also provides hot water while I just want the hot water. This means I'll have to set up a condenser loop and a cooling loop, neither of which will actually be used which seems like a waste of time.

My question is is the ChillerHeater:Absorption:DirectFired a valid way of modelling a gas absorption heat pump if I can set it so that the chiller is never activated? Am I missing a better way of doing this?

Edit I've set this up and it's running, and with the chiller and condenser loops having operation schemes that are set to always of I think it's OK. A lot of extra lines in the IDF but it's working.

I'm still interested to know if this is the correct way to model this system or if I've missed a simpler alternative.

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answered 2015-08-05 10:07:35 -0500

updated 2015-08-05 10:18:35 -0500

With current EnergyPlus v8.3.0 capabilities, the ChillerHeater with an unused chilled water loop is the best available option. You can set the Condenser Type to AirCooled and drop the condenser loop.

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Is this still the case in v8.6?

jblake's avatar jblake  ( 2016-12-06 14:45:01 -0500 )edit

Yes, this is still the case in v8.6 and will be in v8.7.

MJWitte's avatar MJWitte  ( 2017-02-02 09:29:29 -0500 )edit

How about now??

Jean Marais's avatar Jean Marais  ( 2021-12-21 09:32:13 -0500 )edit

Still the same in v9.6.

MJWitte's avatar MJWitte  ( 2022-01-04 13:32:04 -0500 )edit

answered 2015-08-05 11:46:56 -0500

Archmage's avatar

An old workaround for this is to use Boiler:HotWater with the efficiency set to a desired average COP of say 1.2. You'll have to edit the IDD to remove the "\maximum 1.0" line in this input field.

N2 , \field Nominal Thermal Efficiency
     \type real
     \minimum> 0.0
     \maximum 1.0
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Asked: 2015-03-04 02:08:54 -0500

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Last updated: Aug 05 '15