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Plant loop with steam equipment definitions possible?

asked 2018-04-16 15:07:56 -0500

hnagda's avatar

updated 2018-04-16 15:57:04 -0500

I am modeling a lab building with a lot of equipment like steam sterilizers with direct steam consumption. I added steam equipment loads in the spaces and I am getting the MBtu's of steam consumed by the building in the OpenStudio output. However, I want the output in terms of natural gas used to produce that steam. Is there a way I can model a plant loop, add these steam equipment loads on the supply side and have a natural gas fired boiler producing steam on the demand side ? How can this be done in OpenStudio? Or is there any other way I can model steam consumption in spaces and natural gas consumption as the output?

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answered 2018-04-17 09:37:58 -0500

Short story: you can't.

Option 1: post processing

You'll need to do some post-processing to calculate that yourself.

If you are using the DistrictHeating fuel for something else than your steam equipment, make sure you fill in the SteamEquipments' End-use subcategory, so you can easily only get the consumption for these steam equipment.

Use the consumption to calculate your natural gas consumption. The easiest way would be to calculate it with a fixed system efficiency (boiler efficiency + distribution losses).

Option 2: bump SteamEquipment consumption

Another alternative is to bump your SteamEquipment's consumption to factor in the steam system efficiency and adjust the fraction lost so you don't end up with too much extra heat in your Zone.

Here's a dummy example for you. Green=E+ inner working, Blue=Input, Red=Calculated.

Bump up SteamEquipment Consumption

Limitations prevent you from connecting your SteamEquipment to a PlantLoop:

  • OpenStudio aside, this isn't possible in E+ to my knowledge: SteamEquipment cannot be linked to a PlantLoop, and I don't see any other components that could be fit for this job.

  • Steam systems are not supported in OpenStudio. There is only one component you'd need that is implemented (Boiler:Steam), but others are not (PumpVariable:Speed:Condensate, Pipe:Adiabatic:Steam, all the steam components such as Coil:Heating:Steam etc). This is why the steam boiler is not yet included in the HVAC library.

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Here is the new feature request for steam to hot water heat exchanger capability in EnergyPlus. Add your positive reaction (e.g. 'thumbs up' emoji) to express your enthusiasm for this feature.

ericringold's avatar ericringold  ( 2018-04-17 10:42:31 -0500 )edit

Thanks for the answer @Julien. 19k karma points is amazing! After you short derivation, I read about the fraction lost/radiant/latent terms and I understand those better now. As for the the steam equipment, there is an option to change the fluid type to steam in the plant loop, but I assume that wouldn't be very useful as of now?

hnagda's avatar hnagda  ( 2018-04-17 15:49:20 -0500 )edit

@Eric Ringold I upvoted the request. Thanks for adding it.

hnagda's avatar hnagda  ( 2018-04-17 15:50:23 -0500 )edit

@hnagda: in the OS App changing the fluid Type to Steam won't do much no.

Julien Marrec's avatar Julien Marrec  ( 2018-04-18 04:53:02 -0500 )edit

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Asked: 2018-04-16 15:07:56 -0500

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Last updated: Apr 17 '18