Heat Recovery Chiller Staging in EnergyPlus

I'm having difficulty with staging the hot water side of a Chiller:Electric:EIR with heat recovery. I have the hot water side of the condenser barrel connected to the supply side of a hot water loop in parallel with a DistrictHeating object. The demand side has a LoadProfile:Plant object that provides the load.

I want the Chiller:Electric:EIR to first try to meet the load and the DistrictHeating to provide the remainder of the heat to meet the loop setpoint. I've tried various configurations and can not seem to get the heat recovery side to control in the correct way.

Does anyone know the correct way to control the heat recovery chiller model with district heat in parallel?

Heat recovery from Chiller:Electric:EIR is a passive benefit when the chiller operates to meet a cooling load. In the EnergyPlus world, the heat recovery side of the chiller should be on the demand side of a heat recovery loop which has a storage tank (WaterHeater:*) on the supply side of that loop. Then the "use" side of the water heater serves as a supply for the hot water loop. If you do not have storage in your plant design, then you could make the tank volume small.

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MJWitte

answered 2014-12-05 13:46:00 -0500

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Michael, thanks for the reply. It would be really helpful if this was clarified in the Engineering Reference section on "Hot Water Heat Recovery from Chillers", since the heat recovery condenser bundle is treated differently than the standard demand/supply side components. Is the treatment as a passive component due to the limitations in the loop heat balance manager? We have had issues matching the design temps and flow rates when we add an additional heat exchanger. Having the ability to model using the PlantEquipmentOperation:* would be desirable for this reason.

jmcneill (2014-12-15 11:44:49 -0500) edit

It could be done, but it is not straightforward because the chilled water and hot water loops need to coordinate for this to work without over-chilling just to meet a heating load. It is this way mostly, because this was not a use-case that was considered at the time the component model was developed.