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Producing cost estimate for a VRF System in EnergyPlus for use in jEplus

asked 2017-05-20 14:09:24 -0600

updated 2017-05-20 14:53:00 -0600

I tried using the CostComponent:LineItem to produce a cost output for a VRF system (AirConditioner:VariableRefrigerantFlow), but it didn't work. I figured it probably wouldn't because the only HVAC equipment listed in the Input-Output Reference is the Chiller:Electric HVAC equipment. Ultimately, I am trying to use jEplus+EA to determine the lowest cost of the whole building (including VRF System). The one way I have found to do this is to output the total cost of the building (including VRF System) into the .sql file, so that I can use the .vrx file to set the total cost as the objective. But I can't do that unless I can apply the CostComponent:LineItem to the VRF system. My questions are:

  1. How would one calculate the cost of a VRF system in the .idf file in order to output the price in the .sql file in order to set as the objective in jEplus+EA?
  2. Is there another method I should be looking into?


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answered 2017-05-22 03:43:30 -0600

Yi Zhang gravatar image

Hi Jonathan,

I guess the VRF cost is linked to the auto sizing outcome. If this is the case, what you really need is to get the sizing information from E+ output. Then you can apply multiplier (e.g. $/kW) in the jEPlus .rvx file to calculate the VRF system's cost, before adding it to the total cost (excluding VRF) reported by E+.

At present, jEPlus does not read zone and system sizing reports in the epluszsz.csv and eplusssz.csv. The only place to get sizing info is from Component Sizing Summary in the summary report (request AllSummary in Output:Table:SummaryReports, and see the resultant eplustbl.htm.) A more convenient and faster way to pick a single number of the summary report is using the CSV function rather than SQL. See documentation here:

Let me know if this doesn't work. There are other ways (e.g. EMS) we can try next.



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Thank you for your response Dr. Zhang. I had considered using the first option (applying a multiplier to the sizing information), but unfortunately I will be swapping out different HVAC system types other than the VRF system (using the parameter function in jEplus) so the multiplier would need to change with the different HVAC system types. I don't think there is way to automatically modify this multiplier with its corresponding HVAC system since it would exist in the .vrx file.

I'm guessing that we might want to use the EMS function?

Jonathan K gravatar image Jonathan K  ( 2017-05-22 10:27:02 -0600 )edit

What will happen if the model has no VRF and the expected part of the sizing report is void? If jEPlus return value '0', that'd be just what you need, right?

Yi Zhang gravatar image Yi Zhang  ( 2017-05-22 11:00:26 -0600 )edit

Ah I think I see your point. So as long as each HVAC system has a unique FromTable;FromRow;FromColumn from the ComponentSizingReport, then if jEplus doesn't find that value (because that HVAC system type will have a different Table name), then it will return a value of 0? For example the FromTable name for a VRF system would be AirConditioner:VariableRefrigerantFlow, while for a VAV System it would be Boiler:HotWater, since I could grab the chiller cost using the CostComponent:LineItem option? I didn't know that you can include lookup portions of the rvx file that could potentially not exist

Jonathan K gravatar image Jonathan K  ( 2017-05-22 11:36:57 -0600 )edit

in the eplustbl.csv file.

Jonathan K gravatar image Jonathan K  ( 2017-05-22 11:38:23 -0600 )edit

Uh, I am not completely sure about what jEPlus will do in case of an expected field in the eplustbl.csv is missing. But it worth a try as it is the simplest solution. You can also pass the unit cost for VRF using a LineItem, I think...

Yi Zhang gravatar image Yi Zhang  ( 2017-05-22 12:14:26 -0600 )edit

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Asked: 2017-05-20 14:09:24 -0600

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Last updated: May 22 '17