Most modern string inverters have a DC-DC boost phase to allow a wide DC voltage operation. Whatever voltage the inverter side works at is where the inverter will be most efficient, and thus generate less heat.
So it is not really accurate to say high voltage is worse than low voltage for the “heat kills” concern (which I agree with). The same is true for DC-DC optimizers – they contain a boost/buck circuit that has an optimum efficiency point in the midrange of the DC operating voltage... Current a bit more complicated but generally efficiency curves for inverters are pretty flat above 10-15% loading. Obviously the same efficiency operation generates more heat when processing more power – so good thermal design matters. And removing as much power conversion equipment from under the array should help reduce thermal load and cycling too (but that is definitely a biased opinion =) ) Mike Michael Mahon (he/him) Solar Academy Manager | SMA America +1 916 918 9412 SMA America<https://www.sma-america.com/> | Solar Academy<https://solaracademy.sma.de/en/> | TechTip Channel<https://www.youtube.com/playlist?list=PLoiOll7F4i-_Wc4JVN8ga2x2vxc8xews_> | Upcoming Academy Trainings<https://solaracademy.sma.de/en/courses.html?filter%5b1%5d=English&filter%5b2%5d=United%20States> [cid:image001.jpg@01DB7176.DEABC400] This email and any attachments thereto may contain SMA America, LLC confidential, privileged and private material for the sole use of the intended recipient. Any review, copying, or distribution of this email (or any attachments thereto) by others is strictly prohibited. If you are not the intended recipient, please contact the sender immediately and permanently delete the original and any copies of this email and any attachments thereto. Thank you. From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> On Behalf Of Jerry Shafer via RE-wrenches Sent: Monday, January 27, 2025 10:21 PM To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Cc: Jerry Shafer <jerrysgarag...@gmail.com> Subject: Re: [RE-wrenches] PV watts question Wrenches, So MPPT,s working at high voltage high and high current with even with the electronic switching you will generate heat and over time heat kills Fun times On Mon, Jan 27, 2025, 8:04 PM Jeff Clearwater via RE-wrenches <re-wrenches@lists.re-wrenches.org<mailto:re-wrenches@lists.re-wrenches.org>> wrote: 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<mailto: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<mailto: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<mailto: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<mailto: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<https://www.google.com/maps/search/735+Tank+Farm+Rd+Ste+130+%7C+San+Luis+Obispo,+CA+%7C93401?entry=gmail&source=g> Cell phone +1 805 704 3226 | Fax +1 805 357 6104 www.recgroup.com<http://www.recgroup.com/> | george.mcclel...@recgroup.com<mailto:george.mcclel...@recgroup.com> -----Original Message----- From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org<mailto: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<mailto:re-wrenches@lists.re-wrenches.org>> Cc: jay <jay.pe...@gmail.com<mailto: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<http://re-wrenches.org/> List Address: RE-wrenches@lists.re-wrenches.org<mailto: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. 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