Re: [RE-wrenches] PV watts question

[Jeff Clearwater via RE-wrenches]

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.  Sent from my iPhone On Jan 27, 2025, at 7:55 PM, Jeff Clearwater <je...@villagepowerdesign.com> wrote: Yes I’ve wondered about this too and there is much debate on forums etc about exactly how this works.  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).  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?   Sent from my iPhone On Jan 27, 2025, at 12:43 PM, jay via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote: HI David, My point exactly.   On Jan 27, 2025, at 1:35 PM, david quattro via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote: 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 On Mon, Jan 27, 2025 at 12:20 PM George McClellan via RE-wrenches <re-wrenches@lists.re-wrenches.org> wrote: 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. George McClellan | Senior Manager, Technical Sales | REC Americas LLC 735 Tank Farm Rd Ste 130 | San Luis Obispo, CA |93401 Cell phone +1 805 704 3226 | Fax +1 805 357 6104 www.recgroup.com | george.mcclel...@recgroup.com -----Original Message----- From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> On Behalf Of jay via RE-wrenches Sent: Monday, January 27, 2025 11:56 AM To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Cc: jay <jay.pe...@gmail.com> Subject: [RE-wrenches] PV watts question Caution: This is an external email and may be malicious. Please take care when clicking links or opening attachments. HI All I’m working with a customer who’s pretty savvy and is using PV watts for his design. 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. Hes in Santa Fe NM. .8   ratio=  1663 kwh/yr 1.0 ratio = 1668 kwh/yr 1.2 ratio =  1671 kwh/yr 1.5 ratio = 1623 kwh/yr I was expecting that more PV = more kWh/yr. What am i missing? standard module fixed roof mount 14.08 loss’s 10 degree tilt 180 degrees jay _______________________________________________ List sponsored by Redwood Alliance Pay optional member dues here: http://re-wrenches.org List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org There are two list archives for searching. When one doesn't work, try the other: https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out or update participant bios: http://www.members.re-wrenches.org ________________________________ This message is private and confidential and may be privileged. Any unauthorized use, dissemination of the information or copying of this message is prohibited. 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