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How can I use energyplus weather converter to split global radiation in to direct normal and diffuse horizontal radiation

asked 2017-05-20 08:44:49 -0500

Amy Lee's avatar

updated 2020-01-20 12:09:59 -0500

I'm trying to validate a building model by take into account the real weather situation. A onsite weather station had been installed.

But for solar radiation data,only global(total) radiation is available. From the auxiliary programs document,weather converter program, it seems the weather converter can use Perez split model to split the global into direct normal and diffuse horizontal values.

My questions is how can this be done using the weather converter? I do not find much useful related information yet.

If you had experience about this or done similar staffs before. Your suggestion is really appreciated.

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Good afternoon,

I would like to validate the building, but the EPW climate file I have only referred to climatic data of temperature, relative humidity, overall radiation. From what I perceive through the weather convert program it is possible to determine the diffuse horizontal and normal radiation.

In this way, I would like you to help me make a file to convert the radiation with the help of this program.

Please if you know how to solve this, it was very important to move forward with my master's thesis.

Thanks.'s avatar  ( 2017-09-21 10:34:26 -0500 )edit

2 Answers

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answered 2017-05-24 08:03:42 -0500

Repeating answer from helpdesk weather expert here. Read about the weather converter in the Auxiliary Programs document. With only Global Solar input, the program will automatically use the Perez model to split the global into direct and diffuse, which EnergyPlus needs.

You will need a "def" file that describes your input weather data. An example def file may be found here.

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Thanks a lot for your answer.

Amy Lee's avatar Amy Lee  ( 2017-05-25 03:41:07 -0500 )edit


I try to read about weather converter in the Auxiliary Programs.

As @AmyLee said, I did not understand how EnergyPlus weather Converter can split the Global solar Input, it is not very helpful.

Maybe some more explaination will be helpful?

Thank you,

BORM's avatar BORM  ( 2017-06-29 11:32:01 -0500 )edit

In the "def" file, the DataElements field specifies the contents of each column of the data file starting with column 1. If the weather data file only has global solar data, then this list will include only GloHorzRad (or Global Horizontal Radiation, long and short names are valid). When this data is processed, the Weather Converter will automatically split this into direct and diffuse.

MJWitte's avatar MJWitte  ( 2017-07-03 07:32:38 -0500 )edit

Thanks Michael for your update.

I tried to delete direct and diffuse radiation in "DataElements", "DataUnits" and "DataConversionFactors" lists in def template file. But it will report errors when trying to deal with CSV weather file with direct and diffuse radiation column deleted. The only way I find can be successfully operating is to delete all the direct and diffuse radiation data in CSV while keep them in the def file lists.

BTW. it will be very helpful to have a checking list(like e+ error file) if there are errors occurred in the weather converting and the whole process crushed.

Amy Lee's avatar Amy Lee  ( 2017-07-04 08:09:31 -0500 )edit

Hi Amy, I would really like to know how you made it work. I tried both your suggestions and it does not work for me. Could you provide your .def and .cst files that succeeded ? Thanks so much! @michael : I tried what you said and it does not work for me. Any other insights on that matter? I really think the documentation is lacking explanations on that matter ! Thanks everybody!

Aurore's avatar Aurore  ( 2019-04-03 04:38:44 -0500 )edit

answered 2022-06-23 11:17:50 -0500

hermmanhender's avatar

Hi! I had the same problem and I solved in the following way.

In Auxiliary Program documentation( part 2.5.9 Custom File Processing - Solar Radiation Value Calculation tell you:

"[...] many data sources have only Global Horizontal (sometimes called Total) or none of the solar radiation elements. When global radiation is available, then a different model (Perez Model) is used to split the global into direct normal and diffuse horizontal values.[...] In custom weather file processing does the following: [...]

  • If you have global horizontal then Perez model is used for the direct/diffuse components split.


However, you need to privide the data of Global Horizontal Radiation and indicate that you don't have other data of radiation (the normal and diffuse horizontal radiation). And in order to indicate to EnergyPlus that you don't have these, data you need to read the part 2.9.1 Data Field Descriptions. Particulary, parts and, where the documentation says "use 9999 for missing data" for these two.

With this in mind, you replace the information in your WeatherFile of solar radiation and automaticaly EnergyPlus will do the calculations of Perez model when you run the simulation.

My custom WeatherFile to use only Global Horizontal Radiation was as in the attached file.

Sorry for my english, I hope it help to all you. Best!

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Hello, hermmanhender. It seems that the custom WeatherFile run from Energyplus is not attached. Could you please provide the file? Even if I set DNI and DHI to 9999, solar splitting does not work in Energyplus.

SJ LEE's avatar SJ LEE  ( 2023-12-27 01:06:57 -0500 )edit

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Asked: 2017-05-20 08:44:49 -0500

Seen: 2,073 times

Last updated: Jun 23 '22