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Solar panel hotspot?

KNAD

New Member
Joined
Mar 25, 2023
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10
Location
Colombo
I have got some Ulica Solar 580w bifacial solar panels installed on a concrete slab.
After about 2 weeks some of them have developed patches like those on the photos.
Is this normal? Are they hotspots?

Thanks in advance

hotspot3.jpg
hotspot.jpg
 
They don't look like hot spots to me, but the photos are too fuzzy to really see whats going on. Can you post a couple of close ups of one or two spots?

You can confirm or exclude hotspots with an IR thermometer. You can buy for about $10 if you don't have one. Be sure it's a sunny day and your modules are under load when you get the temps. Get temps where the spots are and nearby, and ambient temp. Don't shade the modules with your body and then come in and get your temps quick because shading from your hands and body can in themselves cause temporary hotspots.

What do you mean by the modules are on a concrete slab? Directly laying on the concrete? Air space? Tilt angle?
 

Common Solar Panel Defects: Solar Panel Discoloration & Delamination​


 
They don't look like hot spots to me, but the photos are too fuzzy to really see whats going on. Can you post a couple of close ups of one or two spots?

You can confirm or exclude hotspots with an IR thermometer. You can buy for about $10 if you don't have one. Be sure it's a sunny day and your modules are under load when you get the temps. Get temps where the spots are and nearby, and ambient temp. Don't shade the modules with your body and then come in and get your temps quick because shading from your hands and body can in themselves cause temporary hotspots.

What do you mean by the modules are on a concrete slab? Directly laying on the concrete? Air space? Tilt angle?
Thanks for your response. I will do this and update the thread.
The solar panels are installed at the correct tilt angle for the region and about 1m above the concrete surface. Just wanted to highlight that they are not roof-mounted
 
Ok great. Since they're bifacial modules and you have 1 meter clearance, if might be helpful to get underneath and see if discoloration and or localized heating shows up on the back of the cells as well as the front.
 
I'd recommend roping whatever distributor/store you purchased them from/through, and see if they have seen this before, and if you should look into warranty replacement. The manufacturer might want to be made aware that this is happening with their product in the field. I can't nail down when they were first introduced, but I have seen recalls involving some change in process of manufacturing, that didn't work out like they'd planned.
 

I've never seen bird droppings etch a pv module. Chemicals in industrial locations yes. With good closeups it should be easy to tell if the discoloration is internal to the laminate or on the glass surface. We just can't tell from the photos provided.

Internal discoloration can be hotspots, improperly cured encapsulant, internal corrosion, or contaminants like finger oils, solvents or fluxes that got there during module assembly.

Internal corrosion is usually due to moisture intrusion which isn't likely to happen in the middle of a double glass bifacial module. It also usually takes awhile after installation to manifest itself.
 
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Thanks for all the inputs.
I have got some close-ups now (The bright spot is from the flash of the camera - forgot to turn it off)
I will check the temperature values once I get the IR thermometer tomorrow.
I must also mention these solar panels are only two months old.

IMG-20241213-WA0070.jpg
IMG-20241213-WA0071.jpg
IMG-20241213-WA0072.jpg
IMG-20241213-WA0073.jpg
IMG-20241213-WA0074.jpg
 
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I don't think you'll find that those are hotspots. I see no sign of heating.

See the well defined rounded edges of the darker areas that look like bubbles? That looks like delamination to me. Basically places where the EVA encapsulant pulled away from the cell surface.

EVA needs to be heated to a specific time and temperature spec in an evacuated laminator in order to adhere and cross link properly. That doesnt look like it happened in this case. Either that or it didn't adhere to the cells due to some surface contaminant but that is less likely I think.

So you have a warranty Claim against Ulica which warrants their products to be free from defects in materials and workmanship. Take a close look at all your modules and ask that any with those bubbles in them be replaced. If you don't eventually those cell surfaces will collect moisture (because EVA does absorb moisture over time) and become corroded.
 
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Contamination during cell manufacturing? Someone spilt their Mt Dew on the assembly line?

Here is an unmatched weak cell put into a panel full of strong cells. The entire cell is WAY hotter than the rest. Panel is brand new.

Solar Panel Hot Spot.png
 
Contamination during cell manufacturing? Someone spilt their Mt Dew on the assembly line?

Here is an unmatched weak cell put into a panel full of strong cells. The entire cell is WAY hotter than the rest. Panel is brand new.

View attachment 262829
The most popular soft drink in China is Coca Cola so that could be it. But I suspect it's more likely the contaminate is alcohol ingested by the laminator operator...

Yep that IR image is typical of what a hot spot looks like. Either a whole cell or a partial because its got a crack through it so it's active area is reduced. Either way, that cell isn't producing as much current as it's neighbors so the good cells in the string push current through it which drives it into reverse bias and it gets hot. The bypass diodes limit the reverse voltage so in theory the bad cell doesn't get hot enough to burn up the laminate. Sometimes it actually even works that way.
 
Checked with a thermometer and there is no noticeable difference in temperature between the affected cells and the rest.
One more observation - if you spill some water over it the patch becomes hardly visible. Does that mean anything? The patch has something to do with the glass?
 
Yep, not hotspots.

When light passes through a surface where the index of refraction changes (say between air and water or air and glass) it gets bent to a different angle. That's why when you look into a pool objects appear distorted.

Glass and water have about the same index of refraction so pouring water on the glass essentially creates a new air to glass surface. if you're saying the spots disappear when you do that it would indicate that the spots could be on the glass surface, not internal to the module.

Solar module glass has an antireflection coating on it to improve light collection.
So it could be youre seeing a defect in the AR coating. If that was the case though it should have been visible all along, unlike say a hot spot or a delam which would more likely show up after installation and module exposure to electrical and thermal cycling. Were the spots possibly there from the beginning?

Since the glass is about 3mm thick, take a close look at the spots with a magnifying glass under direct sunlight, you should be able to see if they are on the surface or internal. Looking at the edges of them on an angle will help.

Either way, it is a manufacturing defect and id put in a warranty claim.
 
Checked with a thermometer and there is no noticeable difference in temperature between the affected cells and the rest.
One more observation - if you spill some water over it the patch becomes hardly visible. Does that mean anything? The patch has something to do with the glass?

Here are some pics from my one and half year old bifacials
IMG_20241214_125141308_HDR.jpgIMG_20241214_125148212_HDR.jpg

When photographed dead on:
IMG_20241214_125153683_HDR.jpg
Either way, it is a manufacturing defect and id put in a warranty claim.
but Why??
any new panels will also develop those soon assuming there are birds around .
 
I don't understand your question.

Your spots are either internal delaminations which will eventually result in corrosion internally or they are defects in the glass surface AR coating, which may or may not get worse over time. Are you able to determine which?

Either way it's a manufacturing defect which should be covered by the product warranty.

I don't see what that has to do with bird droppings. But of course, it's entirely up to you if you want to pursue a warranty claim or not.
 
Here are some pics from my one and half year old bifacials
View attachment 262885View attachment 262886

When photographed dead on:
View attachment 262887

but Why??
any new panels will also develop those soon assuming there are birds around .
You seem to be having a very similar issue to mine.
What brand are your solar panels?
Do you mean to say whatever panels that you install in this premises eventually end up like this irrespective of the brand/model?
 
If putting water on it makes it disappear then it is some kind of surface contaminate. Have you tried to clean a spot?
 
Yep, not hotspots.

When light passes through a surface where the index of refraction changes (say between air and water or air and glass) it gets bent to a different angle. That's why when you look into a pool objects appear distorted.

Glass and water have about the same index of refraction so pouring water on the glass essentially creates a new air to glass surface. if you're saying the spots disappear when you do that it would indicate that the spots could be on the glass surface, not internal to the module.

Solar module glass has an antireflection coating on it to improve light collection.
So it could be youre seeing a defect in the AR coating. If that was the case though it should have been visible all along, unlike say a hot spot or a delam which would more likely show up after installation and module exposure to electrical and thermal cycling. Were the spots possibly there from the beginning?

Since the glass is about 3mm thick, take a close look at the spots with a magnifying glass under direct sunlight, you should be able to see if they are on the surface or internal. Looking at the edges of them on an angle will help.

Either way, it is a manufacturing defect and id put in a warranty claim.
The panels were installed during the rainy season here. I would not have been able to see the spots unless I was specifically looing for as such at that time due to water on the surface.
Looked at it with a normal magnifying glass but you don't see anything like AR coating being eroded away from the glass. Maybe I should use a small USB microscope!

P.S I have already contacted the distributor about this. Awaiting their response...
 
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If putting water on it makes it disappear then it is some kind of surface contaminate. Have you tried to clean a spot?
Yes I did. But there is nothing tangible to be wiped away there. Whatever there is, is flat with the glass surface.
 
It looks like an oily residue on the external surface. At least that's the simple explanation. If you washed the panels, what did you use? I would wash them with a dishwashing detergent like Dawn. That's what I use on my panels. I fill a spray bottle with water and add a few drops of Dawn.

I bought some used panels and they really needed a good cleaning so I used some light auto paint polish. That took care of the imperfections. You wouldn't have that on brand new panels. I bring this up to show what you can use on PV panels if you need to.

As stated in other posts, if the discoloration is internal then I would try to warranty them out.
 
It looks like an oily residue on the external surface. At least that's the simple explanation. If you washed the panels, what did you use? I would wash them with a dishwashing detergent like Dawn. That's what I use on my panels. I fill a spray bottle with water and add a few drops of Dawn.

I bought some used panels and they really needed a good cleaning so I used some light auto paint polish. That took care of the imperfections. You wouldn't have that on brand new panels. I bring this up to show what you can use on PV panels if you need to.

As stated in other posts, if the discoloration is internal then I would try to warranty them out.

No amount of cleaning could get rid of it. It is either embedded in to the AR coating or something internal.
I am yet to hear from the distributor.
 
I have 3 sets(pallets) of panels. One set all has cracked glass, second set has internal corrosion and the third set has cracked backing. They all look bad but make expected power. All where very cheap. Don't worry to much about the stains. Panels are a long term consumable, nature gets them eventually.

I will add....ALL of my strings are under 100v.
 
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Broken solar modules aren't worth anything. They should be paying to take them to the landfill. Water will get into the EVA quickly and corrode the cells. They're also a shock hazard if you have a (typical) several hundred volt system.

Good modules should last 25 years or more. There are plenty that have been in the field longer than that and are still going strong. And rigorous accelerated life testing is required as part of the IEC61215 certification that solar modules all have. The manufacturers wouldn't offer 25 year warranties otherwise.
 

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