Solar radiation on a tilted surface

Good morning,

I’m running a solar radiation simulation by Ladybug. The total radiation for the flat vertical surface is much higher than the tilted surface. That does not make sense since the sun should be perpendicular to the slanted surface. Can anyone tell me why I’m getting this, please?

Angle (405.5 KB)

@chris can you please help me?

Your Surfaces seem wrong, since there is basically a value of total 0,00 kWh on your facade. Depending on your climate location your average kWh/m² should be around 700 to 1300 kWh/m². Your total radiation even more, since its the cumulative result.

You´ve plugged your geometry input into your context geometry aswell, thus it currently shades itself. Also the surface orientation should be considered, maybe your surfaces normals are the wrong way. The component “flip” cloud help, or you could adress your geometry in rhino directly via “Analyze direction” and/or “flip direction” to see and change the normals.

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I mostly agree with @BenGottkehaskamp, it should definitely put you on the right path.

I just checked your script, the surface direction is correct, but you’ve set the offset distance to a negative number, so effectively your test points are being shaded by your input geometry. Set it to a positive number and it gives reasonable results.

Also the standard comments with legacy scripts - I’d recommend you use the latest version, LBT 1.5 onwards, instead of the legacy components.

In the latest release there’s a LB Directional Solar Irradiance component that can give result of angled surfaces much more efficiently than the legacy tools.

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Thank you! I updated the ladybug and it’s working right now!

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