Severe error with non-convex surfaces.

asked 2015-04-12 14:27:24 -0500

eklein12
363 ●2 ●7

updated 2015-07-10 09:02:15 -0500

When I run the Energy Plus simulation it comes up with this error. "DetermineShadowingCombinations: There are 3 surfaces which are casting surfaces and are non-convex. * ~~~ * ...Shadowing values may be inaccurate." I am not sure how to resolve this issue and what it means exactly.

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@eklein12 in the future please tag your question with the software you're using, it'll get a faster response that way. Are you also using OpenStudio?

MatthewSteen ( 2015-04-12 18:45:01 -0500 )edit

Sorry, I will do that in the future. Yes I amusing Open Studio.

eklein12 ( 2015-04-12 20:36:19 -0500 )edit

I think this is a duplicate of this question: Non-convex surfaces in EnergyPlus

Julien Marrec ( 2015-04-13 02:52:42 -0500 )edit

I think you're right @Julien Marrec. @eklein12, does the previous question help?

MatthewSteen ( 2015-04-13 08:44:39 -0500 )edit

Yes, I have been able to fix the severe error with the non-convex surfaces. Thank you.

eklein12 ( 2015-04-13 09:26:03 -0500 )edit

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4

answered 2015-04-13 08:41:49 -0500

Archmage

7185 ●3 ●11

A casting surface is one that produces a solar shadow on another surface. The shading model in EnergyPlus does not work well for non-convex casting surfaces. You can change a surface from non-convex (or concave) to convex by breaking it up into a set of smaller component surfaces that are each convex.

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1

This issue has been added to the EnergyPlus project requesting support for non-convex casting surfaces. This issue was added to request clarification on this warning output, right now it is somewhat confusing as it is labelled a severe error but the simulation completes and produces results. I think if the first issue were addressed then the second issue becomes unnecessary as there is no more error.

macumber ( 2015-04-13 09:34:20 -0500 )edit

Does anyone know, does this error actually affect the simulation results? Are the results from a simulation with this error still valid?

antonszilasi ( 2016-07-22 09:18:39 -0500 )edit

It definitely affects the results (to the bad). From the Engineering Ref: "During surface entry, surfaces are checked for convex or non-convex shape. If non-convex and inappropriate (used as a receiving surface) then a severe error is produced telling the user that shadowing calculations may be inaccurate."

rpg777 ( 2016-07-22 12:12:02 -0500 )edit

2

Sorry @Archmage , I didn't understand how to change a surface from non-convex (or concave) to convex. Could you please explain it with more details ? I am not really familiar with that concept (of convex surface) and I am new in using openstudio sketchup plugin

Thanks :)