Solar Data Error? Producing more at 6pm than 1pm

  • reploglem1006
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27 Feb 2016 21:53 #4121 by reploglem1006
Solar Data Error? Producing more at 6pm than 1pm was created by reploglem1006
I am currently modeling a small scale 20W solar panel in the Champaign Illinois area. After running the simulation I have found some very strange results.

Going to the hourly data, SAM is indicating that our production is higher at 4pm than 1pm on June 22! This seems very strange, since the previous data points show production decreasing from 1pm to 3pm.

Data shown below:
Power Generated by System (kWh)
12pm: 0.013
1pm: 0.0103
2pm: 0.00598
3pm: 0.00374
4pm: 0.08849
5pm: 0.0834
6pm: 0.0775

Referring to the above data, why is there a drastic increase in production from 3-4pm? This seems counterintuitive. I am using weather station number 725315.

More importantly, how is a 20W panel spitting out 88W at 4pm? I've double checked all my data (since I had to make a custom PV module in SAM) and the data is correct.

Any help is greatly appreciated!

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  • Paul Gilman
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29 Feb 2016 16:09 #4122 by Paul Gilman
Replied by Paul Gilman on topic Solar Data Error? Producing more at 6pm than 1pm
Hello,
There may be a problem with the solar irradiance data in your weather file. Did you check to see if those values look reasonable during the evening hours.
Please [url=mailto:sam.support@nrel.gov?subject=PV%20output%20question%20from%20support%20forum t=_self]email me[/url] a copy of your .sam file and the weather file you are using.
Best regards,

Paul.

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  • Paul Gilman
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29 Feb 2016 19:22 #4123 by Paul Gilman
Replied by Paul Gilman on topic Solar Data Error? Producing more at 6pm than 1pm
Good to know that the problem seems to have resolved itself.

It is possible that with negative shading loss values or for a system with storage you would see results like the ones you describe. Your file does not include either of those, so I'm not sure what might have caused those results.

Best regards,
Paul.

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