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Elements direct and diffuse solar radiation rate too small

asked 2023-08-21 02:16:58 -0500

just a undergraduated's avatar

updated 2023-08-21 15:34:25 -0500

I modified a epw file with element

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and run the simulation. But as seen in the simulation result chart in dview. The direct

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the modified data is very different from original data. I don't know the element method to calculate radiation rate and how to correct this error. Can somebody teach me?

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answered 2023-08-21 08:42:41 -0500

The methodology for how Elements keeps the Global, Beam, and Diffuse components of solar radiation in balance is written out here -- if you have additional questions not addressed by that post, please let us know:

Just looking at your screen shot, it appears that the diffuse component of your solar is quite large as compared to your beam normal (direct) solar radiation (which is also what the simulation is saying); that might be possible under cloudy conditions but if you are adjusting the total global solar radiation and you want to keep the same normal to diffuse ratio as the source EPW, please use the "Beam Fraction of Total" under "variables to hold constant" when adjusting the Global Solar amount.

If you believe you've found a bug, please let us know by sending a bug report to the support email for Elements found here:

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Thank you.,the main problem I'd like to know is after I use the modified epw file by element.and I output both diffuse and direct radiation rates in openstudio,both of them are much smaller than the number I set. as you can see in the last chart

just a undergraduated's avatar just a undergraduated  ( 2023-08-21 21:23:36 -0500 )edit

I would open the modified *.epw file in a text editor and confirm that the numbers you see in Elements are the same numbers that you see in the epw file. If they are, the problem must be somewhere else. Note that EnergyPlus does not use all 3 components of solar radiation as indicated here: Also, be sure that the definitions you are looking at are on the same basis. For example, direct beam normal vs beam radiation on a horizontal surface

Michael OKeefe's avatar Michael OKeefe  ( 2023-08-22 08:09:47 -0500 )edit

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Asked: 2023-08-21 02:16:58 -0500

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Last updated: Aug 21 '23