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Non-convex surfaces in EnergyPlus

asked 2014-11-18 22:06:57 -0500

hodor's avatar

updated 2015-07-10 09:03:59 -0500

EnergyPlus issues warnings about non-convex surfaces, can I safely ignore them? Which calculations are thrown off by non-convex surfaces? Does the answer depend on which value of 'Solar Distribution' I set?


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@hodor. I expected you to ask this question using only intonations of the word 'hodor'. :(

__AmirRoth__'s avatar __AmirRoth__  ( 2014-11-19 07:00:54 -0500 )edit

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answered 2014-11-19 08:07:54 -0500

Archmage's avatar

The Solar Distribution setting is more about non-convex zones, non-convex surface warnings will apply to the ConvexWeilerAtherton setting for polygon clipping algorithm in the ShadowCalculation object. For that any self-shading of the exterior envelope can be in serious error for non-convex receiving surfaces. But the default shadow calculation is now (since V7) SutherlandHodgman and it should be able to handle simple non-convex surfaces. I would look into the warnings fairly closely before ignoring them.

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Hey @Archmage , I have actually set the SutherlandHodgman algrithm for my model, but I still have this severe error : Severe ** DetermineShadowingCombinations: Surface="SURFACE 677" is a casting surface and is non-convex. ** ~~~ ** ...Shadowing values may be inaccurate. Check .shd report file for more surface shading details

Do you (or does anyone) know how to fix this ? (to make the surface convex )

I would appreciate your help, if possible :) Thanks

Raghda Derbel's avatar Raghda Derbel  ( 2018-08-07 09:44:51 -0500 )edit

answered 2014-11-18 22:18:16 -0500

updated 2014-11-18 22:19:08 -0500

The non-convex warning will only apply to certain Solar Distribution choices in the Building object like you said. The warnings only have an effect when FullInteriorAndExterior or FullInteriorAndExteriorWithReflections is chosen. These choices calculate the amount of beam radiation that falls on each surface in the zone instead of just assuming all of the beam radiation falls on the floor.

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answered 2023-02-25 10:32:51 -0500

This video goes into detail discussing the reason for a convexivity issue:

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Asked: 2014-11-18 22:06:57 -0500

Seen: 5,010 times

Last updated: Feb 25 '23