Panel Cleaning!!
- Thread starter clayswen
- Start date
The article is talking about the theory of having a bypass diode for every individual cell. This setup does not exist.If only you had kept on reading...
Bypass Diodes | PVEducation
www.pveducation.org
It then explains the bias mechanism of the group layout for bypass. Its unfortunate an individual cell has to be perfectly shaded for absolute protection. Its a compromise designed for multiple cell shading. In bypass, the remaining energy still goes through the weakest cell in a mini closed loop(the group). A partial shaded single cell (bird doo) won't necessarily provide the bias to use the diode for group bypass. Your cheese is still in the wind (or sun).
There is a reason why solar panel manufactures will void warranty for shading.
This guy has a good example of a cell getting "COOKED" by the array. I time stamped it but earlier in the video he shows some glass cracked from heat vs impact. He describes how an impact will have the impact mark or circle and heat cracking does not have those crack patterns or circles:
wattmatters
Solar Wizard
It describes the use of bypass diodes in panels to protect cells when there is shading. There are also half cut cells which help add another layer of protection in combination with bypass diodes.
Which just reinforces that your original claim suggesting the whole power of a PV array passes through a single cell is nonsense. It's not even a whole panel. Current <> power.
Some do, some don't. REC, Trina, SunPower for instance do not explicitly say their warranty is voided due to shade. Others are more vague on the topic.
I can't speak for other countries but here Australian Consumer Law applies and manufacturer warranty conditions cannot override the law. Transient and partial shading is inevitable. The sun comes up and goes down each day and shade will be cast on every panel on the planet at some point. Trees exist near homes and will at times cause some transient partial shading. No installer or manufacturer can avoid their ACL obligations for typical installations such as that.
Just use quality panels and avoid permanent hard shading on a PV array. If there is a blob of something on a panel, then clean it off. If a panel appears damaged, then take it out of service. It can't be that hard now, can it?
Well....if the arrays power doesn't pass through every cell, where does it pass through?
ksmithaz1
Solar / EV Junkie
You should feel free to solve nonexistent problems. A bird-dropping here and there is just not an issue for solar production or reliability of a solar panel. If it was a danger it would be daily headline news with the number of solar installations out there. There are a ton of folks on this forum with panels that get shaded/dirty etc. Nobody is coming to your rescue with stories of having birds pooping on the corner of their panel, causing it to self-destruct. Reality is most all instances of panel destruction are traceable to a manufacturing defect , some sort of abuse, or improper installation. Feel free to wash and wax your panels every weekend, nobody will stop you.
There are solar farms here in AZ, miles of panels. Never heard of an incident of one catching on fire because they didn't ( because they don't ) clean them off regularly. I would guess they probably monitor and examine / spot clean if a given string shows production loss. I would recommend a similar strategy. I mostly clean mine for cosmetic reasons, I don't like my install to look like sh*t.
There are solar farms here in AZ, miles of panels. Never heard of an incident of one catching on fire because they didn't ( because they don't ) clean them off regularly. I would guess they probably monitor and examine / spot clean if a given string shows production loss. I would recommend a similar strategy. I mostly clean mine for cosmetic reasons, I don't like my install to look like sh*t.
ksmithaz1
Solar / EV Junkie
Assuming you are referring to a string. Do you have a long flashlight with stacked batteries? The current stays the same, the voltage (pressure) goes up. The current is what makes it hot, that should be ~constant at whatever the worst panel can push. Most panels have multiple "sections" , if a section can't keep up current wise it will get dropped out of the string by the diodes, dropping the overall output voltage. They also prevent backflow in a parallel scenario. They've been building this stuff for quite a while, most of the safety stuff is pretty solid.
Did you see the video I posted above? Clearly shows a damaged cell from heat.
sunshine_eggo
Happy Breffast!
The hot cell is a defective cell. It's not the result of shading. This video is a compilation of damaged and defective PV modules - not the consequences of shading.
In solar farm training, they utilize tracking meters to evaluate production losses from lower edge buildup, or animals blocking portions of panels, and schedule service.
They aren’t worried about panel failure, they are maximizing production.
Do you seriously think a poop spot on a cell would damage a panel in a string of 1000 to 1500 V sets of panels?
So… all the degraded or old panels that are replaced with larger panels, and sold used… are they trash because of dust on lower edge cells?
The used panels I’ve gotten have not shown any damage like this… and I have used shattered panels for years…
That solar panel shipped after being tested. Was it defective or a miss matched cell? There is not so much difference since all cells technically have defects. Most panels will have one or two cells that are the weaklings. Go out with an IR imager on a full production day and look at your panels. You will see some cells that are much hotter then the others. Usually just one or two. By the way, a tiny bit of shade is the same affect as a miss match as far as hot spotting goes.
There was a good article on a lawsuit from a solar farm that had a bunch of cells burn up on at least 50% of their panels over a few years. The cheap China panels had cells that where probably never matched up. This is why I only like buying known panel manufactures vs say pingdongsun or some such name...lol
Ever wonder why an exact panel from the same manufactures will be for sale with one say having 250w rating and another offer for 255w rating? Its like LEDs or LFP cells. Not one of them is alike in performance but they can be matched up close enough to work. A weak cell in a solar panel just gets run over by the rest of the array and eventually cracking is the usual out come over time. If they are matched well, and running conditions are within specs, they will never go bad.
Truth is, there is no such thing as a perfect silicone cell, they ALL have some defects. They need to be matched as close as possible. The worse thing is, an under rated cell with higher rated cells will make lots of heat WITHOUT providing enough bias for making in past the breakdown window on the bypass diodes. I call it the yellow zone with no bypass. Not red as danger but not green.
By the way, if you run low power strings, you will never have the shade performance to really cook cells, not enough juice.
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There are thousands upon thousands of used panels with heat damaged cells for sale used from solar farms. I have some.
Bird poo creates the same condition as a weak or non matched cell. Partial shading of just that cell can create a condition that heats it up beyond normal operation range. To much heat causes lots of issues over time.
wattmatters
Solar Wizard
a bit of a mess which generally gets washed off with rain. If it never rains, then a quick wipe is all that's needed.
Why are you rabbiting on about a non-issue? It's such a confected concern.
Don't buy junk panels, don't mistreat them, don't do a poor installation and keep an eye on things in case something needs attention. It ain't rocket surgery. Fortunately the good manufacturers have done that for us.
Just sharing facts. Take from it what you want. Some people have had issues, glad you haven't yet.
I don't have 5,000 watts of silicone roasting on my roof so I sleep good. Some people might not like what I'm saying for this reason. The mind has a hard time with new concepts that are a risk.
I completely agree. I won't buy any off brand panels anymore. I have some cheap panels with substantial hot spots, they are new and in full sun. Likely they will not make the full life cycle.
wattmatters
Solar Wizard
1 in 3 homes in Australia has a rooftop PV system. The average installation size for new systems is now close to 10 kW. Yet amazingly there have been zero fires caused by bird shit.
Just sharing facts. Take from it what you want.
Just sharing facts. Take from it what you want.
sunshine_eggo
Happy Breffast!
Technically defective, but mismatched is no different than defective.
There is still a threshold beyond which a defect is an issue. Below which, it isn't. It may pass initial testing but manifest later after being in operation.
This has not at all been established.
What happens to the shaded portion of a panel when a bypass diode activates due to shading?
What happens to a cell subjected to reverse bias?
robby
Photon Vampire
- Joined
- May 1, 2021
- Messages
- 4,199
Almost three years and I have never cleaned the panels once. The rain takes care of that.
I don't think there is a one size fits all solution for dust, poop, etc. on the panels. It all depends on what kind of weather conditions you have and the slope of the panels.
Mine look like new after a few hours of heavy rain but I know some people don't get a lot of rain.
I don't think there is a one size fits all solution for dust, poop, etc. on the panels. It all depends on what kind of weather conditions you have and the slope of the panels.
Mine look like new after a few hours of heavy rain but I know some people don't get a lot of rain.
Yes of course, lol.....I don't think anyone is worried about bird dropping like that. Just trying to explain how partial shading can damage cells.
I do think large solar strings are a bad idea. To much energy concentration going through to much Chinese components. I'm retired now but I use to work around very high voltage and perhaps I have seen to much go wrong over the years.
I will stick with lower power/multiple strings. You all can have your fun, I wont say anymore.
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wattmatters
Solar Wizard
China are approaching a production capacity of 1TW/year of solar PV panels. The paradigm on performance and quality has changed.
The vast majority of DC strings are typically well under 1500 V.
