<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif">Yes, as Matt pointed out, with PV prices much lower now, the economics point toward erring on the side of oversizing the array. This should provide benefits in later years as modules degrade, even if there is some clipping in early years. It definitely reduces the cost per installed watt, and since most comparisons at the end user level are done at a $/watt level, it can provide a competitive advantage. On the other hand, it can look like you are providing less value relative to a competitor that provides a larger inverter relative to the array rating.</div>
<div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">Very interesting discussion. Thanks for the replies.</div><br><br><div id="WISESTAMP_SIG_gmail_session" href="http://WISESTAMP_SIG_gmail_session">
<div style="font-size:13px;font-family:Verdana,Arial,Helvetica,sans-serif"><div style="margin:0 0 8px 0"><p style="margin:0"><span><span>Jason Szumlanski</span></span></p><p style="margin:0"></p><div class="gmail_default" style="font-family:verdana,sans-serif;display:inline">
Fafco Solar</div><br> <p></p><div style="clear:both"></div></div><img src="https://wisestamp.appspot.com/pixview.gif?p=chrome&v=3.44.0&t=1409059885740&u=d0c775731865b324" width="1" height="1"></div></div></div>
<div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Aug 26, 2014 at 9:11 AM, Isaac Opalinsky <span dir="ltr"><<a href="mailto:David.Opalinsky@sunpower.com" target="_blank">David.Opalinsky@sunpower.com</a>></span> wrote:<br>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Jason,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">This seems to be a regular topic of discussion in our training classes not only for microinverters, but also for string inverters. Especially for 3.8 kW units
that are optimal for backfeeding 100A service panels and 7.6 kW units that are optimal for 200A panels. A slightly bigger array can give a higher total yield, maybe some power clipping, without the additional cost of a supply-side connection. As long as
you stay below the maximum VOC and ISC, there isn’t a safety issue. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">So it really just boils down to economics and the overall value proposition for the customer, which makes it hard to provide a blanket recommendation. We’ve
been training people for years to model PV system performance to determine an acceptable DC/AC ratio on a project-by-project basis.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The inverter manufacturers pretty much all claim that there is no concern about overworking or shortening the useful life of their inverters since limiting
operating power limits the operating temperature as well, but that leaves me with two questions:<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>1.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Does anyone have any evidence that high DC/AC ratios does/does not shorten the life of the inverter?
<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>2.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">If there is a small amount of power clipping (say <1% total annual energy), are many customers likely to notice/care?<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><span>3.<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">If they do notice, does the customer service aspect of having to defend a design decision outweigh the potential economic benefits of a smaller inverter?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal" style="line-height:12.0pt;text-autospace:none"><b><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";color:#5f5f5f">Isaac Opalinsky
</span></b><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";color:#5f5f5f">| Technical Trainer |
<b>SunPower Corporation<u></u><u></u></b></span></p>
<p class="MsoNormal" style="line-height:12.0pt;text-autospace:none"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";color:#5f5f5f">Desk <a href="tel:443-569-3476" value="+14435693476" target="_blank">443-569-3476</a> | Cell <a href="tel:443-277-6286" value="+14432776286" target="_blank">443-277-6286</a><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> RE-wrenches [mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>]
<b>On Behalf Of </b>Jason Szumlanski<br>
<b>Sent:</b> Monday, August 25, 2014 4:41 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> [RE-wrenches] Inverters Maximum Input Ratings<u></u><u></u></span></p><div><div class="h5">
<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal"><span style="font-family:"Verdana","sans-serif"">I had a tough customer recently that grilled me on how we can put a 270W solar module on a 215W inverter. Fortunately, Enphase has a wonderful white paper on the subject. However, it got
me thinking... Enphase has demonstrated that higher output panels in many climates (hot SW Florida included) can benefit from modules that far exceed the inverter rating, and even exceed the inverter's "recommended input" rating. Enphase has shown that 270W+
modules can show energy harvest on the M215 where it makes sense to "oversize" the module.<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-family:"Verdana","sans-serif""><u></u> <u></u></span></p>
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<p class="MsoNormal"><span style="font-family:"Verdana","sans-serif"">I also received a similar query from a rather uninformed plan reviewer in an area AHJ along similar lines. Fortunately I was within the "recommended input" rating on the spec sheet of 270W
with a 265W module, but I wonder what would happen if I had paired the M215 with a 280W module on my plans, which are becoming readily available now in 60 cell modules with 300W modules on the near horizon. I'm pretty sure my plan would have been kicked back
for exceeding the manufacturer's recommendation.<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-family:"Verdana","sans-serif""><u></u> <u></u></span></p>
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<p class="MsoNormal"><span style="font-family:"Verdana","sans-serif"">My question, which applies to string inverters and microinverters, is how much is too much, what would happen if you paired an array that far exceeded the rating, and how do inverter manufacturers
determine the recommended and/or maximum rating of the connected module or array? Also, why do some manufacturers have a simple recommendation while others have a "maximum" rating?<u></u><u></u></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><u></u> <u></u></p>
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<p style="margin:0in;margin-bottom:.0001pt"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">Jason Szumlanski<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""></span><span style="font-size:10.0pt;font-family:"Verdana","sans-serif"">Fafco Solar</span><span style="font-size:10.0pt;font-family:"Arial","sans-serif""></span><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""><u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""><u></u> <u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Verdana","sans-serif""><img width="1" height="1" src="http://portal.mxlogic.com/images/transparent.gif"><u></u><u></u></span></p>
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