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Re: [EnergyPlus_Support] Re: create EPW weather file





Did you look further at the audit file from the weather converter?

 Warning ** DirectNormalRadiation > max theoretical        290 times
 Resultant values were set to a corrected value (max theoretical).
 Warning ** PerezSplit DirectNormalRadiation > max theoretical        281 times
 Resultant values were set to a corrected value (max theoretical).

so, the direct normal was changed from a value to the max theoretical value 290 times.

the relationship of global to direct and diffuse is:

Direct_Horizontal + Diffuse_Horizontal = Global Horizontal

Direct Normal is found by a relationship to the current (calculated) sun altitude .

Hope that helps.
In the weather converter you can choose "not to fix data" -- I don't remember if that removes the correction when it is greater than max theoretical or not.

Yes, usually the solar radiation gained from weather stations is Global Horizontal.

At 09:18 AM 6/2/2015, la.epfl@xxxxxxxxx [EnergyPlus_Support] wrote:


Hello everyone,

I was trying to make sense out of some file transformation I have made. I attach the CSV file, the def file I am using as well as the audit file of the conversion.

I would like to know if everything is fine in the process and clarify some topics.

The original data from the CSV file comes from a weather station measurment and I am automatically transcribing it in the CSV. I am mostly interested in having correct solar radiation interpolation. The station gives me a measurement for sun which I assume to be horizontal global radiation. Does that sound like a reasonable assumption or it might be something else ? I do not have so much information about the weather station it comes from wunderground.com data.

Second, the audit file gives me warnings like:
Warning ** DirectNormalRadiation   1076.0 > max theoretical=   690.6 Wh/mâ?¤ on date= 1/ 1 at hour=14
Does that mean that my original data is not good and should I do something about it ?(I have checked latitude longitude, looks fine).
Then when I look at the EPW file I have created, the direct normal radiation for this hour is not 1076 nor 690 but 829Wh/m2, which I don't really understand.

Finally, I was expecting the direct radiation to be greater than the horizontal global radiation, but that is not what happens in practice. Is that then false ?

Any other advice concerning weather conversion and creating EPW based on measured data is welcome as well :)

Thanks in advance,

Best regards




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Posted by: Linda Lawrie <linda@xxxxxxxxxxxxxx>


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