Zone as supply side in Openstudio

asked 2015-06-30 09:24:48 -0500

Hi

How’s everyone doing?

I have one question for you if someone can help me out. It’s just “work around” question where I need to understand how to model this particular kind of system in OS (preferably) or energyPlus. I am doing this greenhouse in openstudio (a pdf attached for greenhouse geometry & HVAC system) where small chambers with no fenestration are for mushrooms (65F, 80-90% RH) & big chambers (with fenestration) are for normal plants (85F with 60%RH). As the greenhouse is on roof-top (something like gotham greens - http://gothamgreens.com/our-farm/), we have constraints on structure loads & HVAC heavy equipment installations.

Majority of cooling load is because of high LPDs (28W/sf for germination & plant growth), envelope loads & ventilation loads. We are also the HVAC designer of the project & calculated the cooling load as 326 tons(!!) for 6500 sq project. We cannot install such a heavy chiller on the roof & building owner can provide us only 50 tons of cooling from his chillers. We figured out that evaporative cooling can be appropriate for the project with very high ACH (78 maximum & 5 minimum) for plant growing chambers (85F). For heating we will use baseboards or radiant heating with natural gas boilers as source.

We have proposed to use cooling coils for mushroom chambers (with 65F) & owner’s chillers can be used for that purpose. To make it more efficient, we are proposing to use “growing plant chambers” as “OA” source for mushroom chambers. It means for mushroom chambers, OA temperature will always be 85F.

My problem is how to create this secondary loop for mushroom chambers where I can assign growing plant chambers as OA source. Any “work around” for that? I am not able to assign a zone in Openstudio airloop’s supply side. Please look at PDF if it makes more sense to you.

Thank you, and looking forward for your response. Best,

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answered 2015-06-30 11:55:23 -0500

Lincoln

1521 ●1 ●10 http://www.kw-engineering.com/

Take a look at the ZoneMixing and ZoneCrossMixing objects in EnergyPlus. These can't be accessed through OpenStudio yet but an OpenStudio Measure can be written to import these objects into your model. These objects are slated to be available in OpenStudio around September '15.

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answered 2015-07-01 10:18:33 -0500

Kyle Benne
6027 ●4 ●9 https://www.openstudio.net/

updated 2015-07-01 10:50:35 -0500

I believe @Archmage put a feature into EnergyPlus where a zone is allowed on the supply side of AirLoopHVAC. I couldn't find an example file or documentation, but @Archmage or @MJWitte can probably point you to some information.

OpenStudio currently forbids a ThermalZone on supply side, but if it is something people need we can certainly open up the API to do this.

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There is a new feature for this in the pipeline but it was by another developer, not me. I don't know the status or why it wasn't merged but the github branch for this work is https://github.com/NREL/EnergyPlus/tr...AsGeneric_HVAC

Archmage ( 2015-07-01 12:54:39 -0500 )edit

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answered 2015-07-01 12:34:04 -0500

Harshul Singhal

565 ●2 ●9 http://www.som.com/

@Lincoln - thanks a lot for sending the info. I will dig more into it.

@Kyle Benne - Thanks for writing me. I wil wait for some replies from @Archmage and @MJWitte on this.

That will be helpful if OpenStudio can do this. I guess this is my 3rd project where we need to use a zone as source. I know NREL is planning to release zone mixing in September 1.9 version but if you can me help me out before that with OS, it will be very helpful. Again, thanks a lot.