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Shading created by PV array on top of roof

asked 2016-03-03 11:57:39 -0500

Julio gravatar image

updated 2016-03-03 13:05:48 -0500

Good morning,

I was adding PV panels to my OS model in OS on the roof and I was wondering if some of you have dealt with the shading effect that this array will have on the building's roof. Is there a way to model this in OS or would the simulation will assume that some shading effect is present by way of having a "second" roof of PV panels? Will this have an impact on the total load of a building?

I found this solution to modeling PV in OS -at the time (Apr/15), OS did not directly support PV- perhaps this is what I am looking for https://unmethours.com/question/4331/... does anyone has any input on this?

Thank you very much!

Julio

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answered 2016-03-03 13:45:23 -0500

Impacts of external shading in EnergyPlus are set using the Solar Distribution input field of the Building object. You would want to set this to "FullExterior" at a bare minimum to account for how external shading surfaces affect solar gains on other surfaces, but there are other options to account for beam radiation distributed on internal surfaces and external reflections as well. If this field is set to "MinimalShadowing" EnergyPlus will calculate the incident solar radiation on the PV surface correctly, but then assume that the building surface behind will also receive the same amount of incident solar radiation.

In OpenStudio, you can change this input field under the Simulation Settings tab, then expanding the Simulation Control area. Reference the screen shot below.

image description

To model the electricity generation of the PV array, you can look at Unmet Hours posts HERE and HERE

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Thank you David and Aaron for your response. I was able to do it, following your solutions and it worked great for me.

Julio gravatar image Julio  ( 2016-03-04 12:13:20 -0500 )edit
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answered 2016-03-03 13:51:28 -0500

updated 2016-03-03 13:52:39 -0500

OpenStudio does now directly support OpenStudio in the SketchUp plugin using the "Add Photovoltaics" user script under "Add or Alter Model Elements".

OpenStudio lets you assign PV to base or shading surfaces. Currently if you want to model it as detached PV vs. building integrated you can use an offset shading surface. If you don't mind writing an EnergyPlus measure you can also model it as a vented cavity. That will more accurately model the interaction between the PV and the building roof, vs, just shading it.

image description Here is the before image with the user script dialog displayed. Before you call the script select the surfaces you want to apply it to.

image description Here is the after image. A texture is used to identify where PV is associated with surfaces.

The standard reporting measure will display a power generation table when PV is used in the model.

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@David Goldwasser, By 'the standard reporting measure', you meant the Add Output Variable OS measure ? Or another measure ?

Raghda Derbel gravatar image Raghda Derbel  ( 2018-09-20 07:30:53 -0500 )edit
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The OpenStudio Results reporting measure will include a table with PV generation results.

David Goldwasser gravatar image David Goldwasser  ( 2018-09-20 08:12:55 -0500 )edit

Aaah okay, I actually already have this measure and the only result related to PV generation is this even though I used the add output variable measures: to see the Generator Requested Electric Power, Generator Produced DC Electric Energy, Generator PV Array Efficiency, Generator Produced DC Electric Power.

PS: I also looked in the csv file but found nothing

Raghda Derbel gravatar image Raghda Derbel  ( 2018-09-20 08:33:46 -0500 )edit

I recommend you validate the reported results in the standard OS report measure, by the way.

rpg777 gravatar image rpg777  ( 2018-09-20 10:28:34 -0500 )edit

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Asked: 2016-03-03 11:57:39 -0500

Seen: 1,279 times

Last updated: Mar 03 '16