Sky matrix containing horizontal irradiation

Hi,
for a study I need to calculate a sky matrix which contains for each sky patch the amount of horizontal irradiation coming from it. Is it possible to do this with Ladybug?

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Permalink Reply by Devang Chauhan on December 9, 2016 at 3:29am

Hi Nills,

Please find attached file.

-Devang

Attachments:

SkyMetrix.gh, 377 KB

Permalink Reply by Nils on December 9, 2016 at 10:24am

Hi Devang,

thanks for the fast response. It worked like a charm.

There's only one question I'd like to ask: When I sum the values of the sky dome and compare it to the annual sum of the epw weather file, they match only for direct normal radiation:

global horizontal direct diffuse horizontal

epw 1183.5 911.9 (normal) 628.7

skymtrx 2172.7 911.9 (horizontal?) 1260.7

Should it not be the other way around, i.e. matching values for global and diffuse horizontal and not for the direct part. Am I confusing something?

Nils

Permalink Reply by Devang Chauhan on December 9, 2016 at 12:08pm

Hi Nils,

Apology for not writing your name right the first time.

As the hint on directNormalRadiation says, it is the radiation received on a surface perpendicular to the sun ray coming from the skydome. Therefore, only direct normal radiation should match, as you pointed out.

globalHorizontalRadiation and diffuseHorizontalRadiation are radiation on a horizontal surface, so they will differ. Attached image should give you a clue. You can test this using Ladybug.

Take the total of globalHorizontalRadiation. From that deduct the total of diffuseHorizontalRadiation. That number will be less than the total of directNormalRadiation.

-Devang

Attachments:

Cosine Angle.png, 72 KB

Permalink Reply by Nils on December 10, 2016 at 8:03am

Hi Devang,

no worries for the name spelling:)

Now it became clear to me. My mistake was to assume that the sky matrices produced by the model you sent me, were already containing the horizontal values. Didn't think about verifying it with the elevation angles... sorry.

Thank you again for your help and explanations!

Nils

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