<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">Ahh I see the light now on the inverter size point. Still I wonder if all MPPts are made equal in terms if they ability to clip high ratios with no ill-effects. <div><br id="lineBreakAtBeginningOfSignature"><div dir="ltr">Sent from my iPhone</div><div dir="ltr"><br><blockquote type="cite">On Jan 27, 2025, at 7:55 PM, Jeff Clearwater <jeffc@villagepowerdesign.com> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><meta http-equiv="content-type" content="text/html; charset=utf-8">Yes I’ve wondered about this too and there is much debate on forums etc about exactly how this works. <div><br></div><div>Large PV plants have long used 1.4 order of magnitude ratios to maximize economics (but much of that was under “per watt” incentives rather than performance based incentives). </div><div><br></div><div>However I’ve long wondered what the true effect of red-lining MPPTs is. I’ve seen it as more of a lifetime issue but I wonder that if you consider overheating of the circuit if we might actually be clipping more than just squaring the top off the curve. Perhaps PVWatts modeled this? They are pretty thorough there at NREL. Or perhaps they have a bug or sloppy programming. It would be worth asking them. Anyone got a buddy at NREL we can ask? <br><div><br></div><div><br><div><br></div><div><br><div><br></div><div><br><div><br></div><div><br></div><div><br></div><div><br id="lineBreakAtBeginningOfSignature"><div dir="ltr">Sent from my iPhone</div><div dir="ltr"><br><blockquote type="cite">On Jan 27, 2025, at 12:43 PM, jay via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><meta http-equiv="content-type" content="text/html; charset=utf-8">HI David,<div><br></div><div>My point exactly. </div><div><br></div><div><br id="lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>On Jan 27, 2025, at 1:35 PM, david quattro via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote:</div><br class="Apple-interchange-newline"><div><div dir="auto">Jay you are right - that doesn’t make sense because with more PV, the system will reach “max AC out“ power sooner every morning and hold it longer into the evening</div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><br></div><div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Mon, Jan 27, 2025 at 12:20 PM George McClellan via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">Probably due to clipping. The panels are generating more energy than the power electronics can process, so that excess energy gets cut off (or clipped). It looks like a 1.2 ratio is optimal.<br>
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George McClellan | Senior Manager, Technical Sales | REC Americas LLC<br>
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-----Original Message-----<br>
From: RE-wrenches <<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>> On Behalf Of jay via RE-wrenches<br>
Sent: Monday, January 27, 2025 11:56 AM<br>
To: RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a>><br>
Cc: jay <<a href="mailto:jay.peltz@gmail.com" target="_blank">jay.peltz@gmail.com</a>><br>
Subject: [RE-wrenches] PV watts question<br>
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HI All<br>
<br>
I’m working with a customer who’s pretty savvy and is using PV watts for his design.<br>
<br>
What I can’t figure out is the kwh/year goes down if he uses dc/ac ration of 1.5 instead of 1.2 which is the default.<br>
<br>
Hes in Santa Fe NM.<br>
<br>
.8 ratio= 1663 kwh/yr<br>
1.0 ratio = 1668 kwh/yr<br>
1.2 ratio = 1671 kwh/yr<br>
1.5 ratio = 1623 kwh/yr<br>
<br>
I was expecting that more PV = more kWh/yr.<br>
<br>
What am i missing?<br>
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<br>
standard module<br>
fixed roof mount<br>
14.08 loss’s<br>
10 degree tilt<br>
180 degrees<br>
<br>
<br>
<br>
jay<br>
<br>
<br>
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