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How to generate point-in-time sky-vectors for sun-coefficient step in five-phase method

asked 2021-06-30 12:54:49 -0500

JChen1234's avatar

updated 2021-07-01 12:18:25 -0500

The annual sky-matrix for the sun disk can be generated using (e.g., from here):

gendaymtx -m 6 -5 0.533 -of assets/NYC.wea > skyVectors/NYCd6.smx

However, if I only want to generate the sky-vector for a certain point in time, what should I use?

I tried:

gensky 3 20 10:30EDT -m 75 -o 73.96 -a 40.78 | genskyvec -m 6 -5 0.533 > NYC_CIE_sun.vec

but got an error:

Unexpected command-line argument: 0.533

Can I simply do

gensky 3 20 10:30EDT -m 75 -o 73.96 -a 40.78 | genskyvec -m 6 -d > NYC_CIE_sun.vec

? In this case, will the absence of the sun disk size '-0.533' information post any problem?

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answered 2021-07-02 10:46:48 -0500

The "-5" option to gendaymtx is special to the 5-phase method, and puts all the solar energy into a single patch, re-normalizing it to get the correct irradiance for the solar disk size (specified as 0.533 degrees).

It is better to extract the single point of interest from your .wea file, removing all the other times and dates, and give this to gendaymtx with the same options. Then, you should get the result you are after.

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Asked: 2021-06-30 12:54:49 -0500

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Last updated: Jul 02 '21