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Attached is a graph that I produced to document the effect of various
ratios between the PV array size and the inverter size. I extracted
output power data for a 1020-watt system located in NE Oregon that is
on the <a
href="http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?page=85820a73-a347-48fb-b8d1-92e5f9b78ab3&plant=608681a7-ef60-4edb-84ff-07110db0ab6a&splang=en-US">Sunny
Portal</a>. The data are publicly accessible so feel free to run your
own analysis. Better yet, analyze the data for a system near you. <br>
<br>
Using 2009 data, I looked at how much energy would have been lost if
the output was clipped at 800W, 810W, .... 1020W. I used 2009 data
because there was a period in 2010 when the Sunny Webbox didn't have
internet access. At 800 watts, power clipping would have happened on
about 25% of the days. Yet the energy that would have been lost was
only 0.38% of the annual total. <br>
<br>
The results shown on this graph aren't universal, results would be a
little different in 2010, it would be different in some other climate,
it would have been different at another elevation, it would be
different with a different array angle, ..., and the module tolerance
and inverter efficiency also effect the results. Modules in this
system are Suntech 170-watt +/-3%. The inverter is Sunnyboy 1800 that
should be operating at close to 93% efficiency.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar. Inc.<br>
<br>
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