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A shorter span or smaller length dimension for the same edge section profile is always stronger. However, that can and is usually considered in the mechanical design. As a practical matter, the long side of a 36 cell panel is shorter than that of a 60 or 72 cell panel, but may well have a similar cross sectional shape and section modulus (one measure of rigidity) as the larger panel, making the smaller panel more overdesigned from a mechanical standpoint, but that overdesign probably being more of a consequence of economic considerations of part stocking, production and assembly than mechanical design, making the smaller panel more overdesigned due to economic and manufacturing considerations rather than a plan to make a more rigid/stronger panel.
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Would a 60 or 72 cell panel be sturdy enough for a homemade ground-mounted human-powered tracking, sled device?Comment
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Homemade human-powered tracking deviceComment
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I can't tell how rigid the parts directly supporting the panels are on your sled.
If they're fairly rigid, I would believe that you could use a 60-cell on it without much problem.
At least I'm thinking you're talking about twisting it to track the sun on fairly level/smooth ground. Not dragging it behind a snowmobile through the brush.
I'd probably avoid pushing on the panel itself, but rather push on the frame.
My guess is that you're probably not putting much more stress on the panel than it would get from being on a roof in a windy storm. Possibly less, depending on how hard you push it / how quickly you move it.
FWIW bcroe has built ground mount system with half pointing east half pointing west. And I think that's probably better solution than this where the person has to physically move it every hour or so.Comment
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I'm new at this so I'm noticing 4 months out of the year it won't have to be moved. And varying degrees other times of t.he year but just three times a day makes a huge difference when this is what I have availableI .made a fair amount of Power with it this summer for the pool pump, fans Etc off two panels then added two more.
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Instead of pvc pipe you might want to look at some type of wheel or rubber tires that will move over uneven land. That will put less stress on the frame and panels yet can still be anchored in place.Comment
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The problem of using 30 year old panels as an indication of what current designs may last is not necessarily a great idea. Arco/Siemens did make some beefy panels but they also has major recall at some point due to issues with the encapsulant. I have a few of them around including one up on my roof running a solar hot water circulating pump and they are definitely cloudy with the encapsulant pulling away from the electrical grid on the face of the panel. They still put out power but definitely not nameplate. The concern with recent panels especially third world supplied is that compromises in longevity are being made in order to drive the price down. If a factory is under orders to drive down costs or be shut down, they are going to cut corners and any future warranty claims is definitely low on their priority list. I think its reasonable to say that well built panels made by legitmate long term manufacturers have potentially very long life far more than 20 years but specific individual panels may have inherent manufacturing flaws that may doom those particular panels to short life.
I had 24 Siemens 65 watt 12 volt panels on my pole mount at one point. I must admit barring driving a ball peen hammer into the glass, they were just about impossible to damage. Unlike larger panels they don't flex. A good indication of how abuse resistant they are is their use on portable highway road signs. I still have few around but most of them are still cranking out power at least 3 off grid camps.
The PWM morning star charge controllers also seem to be very bullet proof.Comment
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It may turn out that the life is determined not by the degradation of the silicon, but of the encapsulant. Bruce RoeComment
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My first pv install was 1983 on the Big Island of Hawaii. Panels are still producing full power. Only thing ever changed was batteries and invertersComment
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The first panels I bought were 2 Photowatt 75W I paid dearly for. Both panels went bad about 10 years later. Each still had a good 6V section so I put two panels in series. Then those sections died, I mean totally dead. You know what that warranty was worth. I sold them to a guy who specialized in repairing dead Photowatt panels, so there are a few out there. A few years ago I went out with an electronic load and measured power point of a few older oddball panels. Some had a pretty low power point voltage indicating weak cells. Finally this year I built into my software a test for the main arrays power point. Most have no ability to test panels and as long as the system still functions they assume the panels are still good. I don't have a lot of faith in the 25 year estimate. Even though it costs more I settled on 100W panels to cut my losses. That and I pack them away when I leave the camp every year, lightness counts for something.Last edited by PNPmacnab; 11-20-2016, 09:33 AM.Comment
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Its generally true that the more moving parts a system has, the more unreliable it is. PV panels have no moving parts which is largely why they are so long lasting. In a portable application where you are moving them around, mounting and unmounting them - not so much. The long term results on inverters are not in yet, but being hard-working electronics in not so friendly conditions, I am very concerned with the long-term claims that inverter makers claim.... So far I've had premature failures in every brand of inverter I've used. Some brands are way worse than others.BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installedComment
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