[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [EnergyPlus_Support] Some issues about non-convex surfaces


I agree with jason and came across similar problem sometime back. it will cause inaccurate solar radiation distribution calculation in the space. See the discussion on page 16 of the I/O guide (pg. 60 of 1932 in the PDF). The impact is severe if the shading surface in larger in size.

Here is a very good example http://www.youtube.com/watch?v=GzJSHQHTHy4 Even if you don't use OpenStudio, you'll get the idea of what needs to be done.

 Hope this helps!    

On Tue, Sep 11, 2012 at 6:32 AM, Jason Quinn <jason.e.quinn@xxxxxxxxx> wrote:

I actually haven't researched why the non-convex surfaces are bad but I have seen how to fix them (at least with OpenStudio). Essentially you break your surface into smaller segments that are all convex. In OpenStudio all you do is draw additional lines in Sketchup to segment the surfaces to squares or triangles and the warning goes away. 

Not sure if this helps as your question 4. below seems to imply that you knew this. The folks from NREL (who are not E+ experts but do a lot of modeling and wrote the OpenStudio interface) told me this fixes this issue. If they are correct than the answer to question 4, is Yes if you break it up it should work and the results should be good.

On Tue, Sep 11, 2012 at 9:23 AM, Farhang <farhang.tahmasebi@xxxxxxxxx> wrote:

Some issues about non-convex surfaces:

1. I have a non-convex roof in my model and I get a warning about shadowing calculation of this surface. I change the "Polygon Clipping Algorithm" to SutherlandHodgman. But again I get this warning. Why?

2. I don't get this warning for the floor. Doesn't the floor play any role in shadow calculation (as a receiving surface), even in "FullInteriorAndExterior" solar distribution?

3. This zone is L-shaped. I change the solar distribution to "FullInteriorAndExterior", but I get no warning or errors, while in the reference it's been clearly stated that this solar distribution mode should not be used with non-convex zones.

4. If in an L-shaped zone we break down the roof and floor to convex surfaces, can we rely on the "FullInteriorAndExterior" solar distribution simulation?


Javed Iqbal, LEED AP, CEA
Energy Analyst   


Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

The primary EnergyPlus web site is found at:

The group web site is:

Attachments are currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.

Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe