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Raju naidu
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Effect of Module Mismatchment in Solar Power Plant

06/08/2011 7:51 AM

Hello,

Please let me know the module mismatchment meaning in solar power plant. Specifically the Effect of

1) Module having lower Imp in an array and

2) Module having lower Vmp in an array?

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PWSlack
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#1

Re: Effect of Module mismatchment in Solar power plant

06/08/2011 8:08 AM

Either way will mean a drop-off in performance compared to installing a matched one.

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PFR
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#2

Re: Effect of Module Mismatchment in Solar Power Plant

06/09/2011 7:42 AM

When modules are connected in series (string method of high voltage production), the module having the lowest IMP will cause those panels with higher imp to operate at a level below their IMP. This results in suboptimal performance. Mismatch error and degraded performance is much less common than it used to be, with manufacturers testing cells more effectively so that they can group them together to make higher wattage modules. Solarworld now has 230,235,240,245,250 watt panels that are all identical physically. The cells are graded and grouped, hence the variation in total output, and they all have different IMP from the others, but are very close within there rated size, so that string mismatch is very minor.

Incidentally, this is the motivation behind the microinverter craze, which loses it's advantage of avoiding mismatch by operating at a lower voltage with higher transmission losses, not to mention increasing system complexity. The monitoring functions are very good because the individual panel is isolated, so that is a plus. Overall, we don't find a lot of applications for them.

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Raju naidu
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#3
In reply to #2

Re: Effect of Module Mismatchment in Solar Power Plant

06/09/2011 7:55 AM

Hi, Thanks for the detail, in our case, we have Imp varying from 1.04 to 1.22. Now we are planning not to use the modules with Imp from 1.04 to 1.07. I am hoping this would increase the overall efficiency of the plant, Assuming if the plant is in MW capacity, will the Performance Ratio be reasonably increased?

Thanks again

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PFR
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#4
In reply to #3

Re: Effect of Module Mismatchment in Solar Power Plant

06/09/2011 12:52 PM

On a small system, efficiency is not relative, however production is. So leaving mismatched modules unused will not result in more power than using them and taking a lowered operating efficiency. On a MW system, accurate panel testing, and grouping into strings, can have very good results. Most modern designs do not require this, as the panels are not that variable.. I do wonder, though, if at ten years of age, simply re grouping modules by Matching Imp would be worth it. I doubt it, but would like to hear other opinions

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Raju naidu
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#5
In reply to #4

Re: Effect of Module Mismatchment in Solar Power Plant

06/10/2011 12:26 AM

Hi,

I understand the power plant need to operate with guaranteed efficiency upto 25 years. and the modules having lower Imp can be kept as spares. With this will it make sense to separate out modules having lower Imp.

Thanks again,

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