why LadyBug radiationAnalysis and energyplus differ in results?

Hello everyone

I check the results of LadyBug radiationAnalysis component with energy plus result for

Surface Outside Face Incident Beam Solar Radiation Rate per Area [W/m2](Hourly) .

I have checked the energy plus InputOutputReference and the explanation for this output variable is :

1.9.45.13
Surface Outside Face Incident Beam Solar Radiation Rate per Area [W/m2]
The solar beam radiation incident on the outside of an exterior surface, including the effects of shadowing, if present. The beam here is that directly from the
sun; it excludes beam specularly reflected from obstructions.

Dose radiationAnalysis calculate the same thing?can any one explain ?

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Replies to This Discussion

Permalink Reply by Abraham Yezioro on January 5, 2017 at 10:55am

Mostafa,

I'm not sure if i understood your question, but i'll try to answer what i did.

Ladybug considers ONLY direct beam radiation. It doesn't account for the reflected/diffuse. For that you need to use Honeybee (Radiance radiation analysis)

Hope this is what you asked.

-A.

Permalink Reply by mostafa on January 5, 2017 at 11:11am

Abraham,

I think the variable you mentioned is :

Surface Outside Face Incident Solar Radiation Rate per Area [W/m2] but the one I mentioned is :

Surface Outside Face Incident Beam Solar Radiation Rate per Area [W/m2](Hourly)

the first one contains reflections and ...... but the one I mentioned just contain "The beam here is that directly from the sun; it excludes beam specularly reflected from obstructions."

Permalink Reply by Mostapha Sadeghipour Roudsari on January 5, 2017 at 2:14pm

What is your test case? Can you share the results? The way ladybug generates the sky is different from what energyplus does. You can compare the results against the weather data for a horizontal surface. I believe I have answered similar questions a couple of times.

Also diffuse can be confusing in this case. Ladybug does consider both direct-light and sky-light from the sky. It doesn't calculate the reflections though.

Permalink Reply by mostafa on January 6, 2017 at 3:07am