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Weather Convertor and Perez Model not working

asked 2019-03-28 08:45:14 -0500

Aurore's avatar

updated 2019-03-28 14:14:20 -0500

Hi everybody,

I have meteorological data for a .epw file. I have the dry bulb temperature, relative humidity, atmospheric pressure, global solar radiation, wind direction, wind speed and total cloud cover.
When I try to use the weather converter (I convert .epw to .epw), it does calculated the horizontal infrared radiation (and delete my values for cloud cover), however it does not fill the direct and diffuse solar radiation (does not use the Perez model) I have tried adding a .def file, but it does not change anything, thought I am not sure that I use it correctly as my case is not in the examples of the AuxiliaryPrograms Documentation.

Any help on that matter would be highly appreciated. Thanks!

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@Aurore, have you tried using Elements to create your weather file?

Jeremy's avatar Jeremy  ( 2019-03-28 10:45:16 -0500 )edit

Hi Jeremy, thanks for your answer! I just did and it split it but its the same at all hours of the day : example my Global solar goes from 416Wh/m² at 7am to 658 (pic at noon) and then to 268 at 6pm, but then it puts the normal solar at 402 from 7am to 6pm and diffuse at 268 from 7am to 6pm so this cannot be correct. Do you have any other insights ? I'm really confused, since in the Engineering Reference and Auxiliary program it says E+ uses the Perez model to split it. I've looked everywhere and I don't understand why it does not work if the documentation says it should... ? Thanks

Aurore's avatar Aurore  ( 2019-04-02 03:04:24 -0500 )edit

@Aurore - when you say that you did it, do you mean using Elements? If so, I have never used it (hence the suggestion in a comment instead of a full answer) so can't be of much help. You could try emailing the developers:

Jeremy's avatar Jeremy  ( 2019-04-02 10:43:48 -0500 )edit

Yes. I emailed them, lets see what they answer. I have found a similar post to mine here : However I tried what Michael and Amy both suggested and it does not work for me. It would be nice to have an example of the .cst and .def file that successfully work to do the Perez split, since the documentation says the WeatherConvertor can do it. It's really missing! Any help would be appreciated. Thanks

Aurore's avatar Aurore  ( 2019-04-03 04:50:44 -0500 )edit

@Aurore - Did you get the reply? Any updates on it.

simransinghal's avatar simransinghal  ( 2020-01-12 05:21:42 -0500 )edit

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answered 2020-04-18 04:12:48 -0500

Aravinda27's avatar

Here is an example file. Weather convertor works fine for me, however, I would not suggest using Perez splitting. There are better models available now.

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May you please share the 'better models' you are aware of?

ajeb's avatar ajeb  ( 2021-05-25 18:16:49 -0500 )edit

Perez model did not give valid results for me. Direct radiations were peaking during the evening. A model's usability depends on the data on which they were built upon. You can search for models which account for data from various parts of the world (North and South Hemisphere). I used the BRL model (Boland-Ridley and Lauret) recently and it worked fine.

Aravinda27's avatar Aravinda27  ( 2021-05-26 22:45:39 -0500 )edit

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Asked: 2019-03-28 08:45:14 -0500

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Last updated: Jul 13 '20