Thanks for your response. I will do this and update the thread.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?
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...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
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?
but Why??Either way, it is a manufacturing defect and id put in a warranty claim.
You seem to be having a very similar issue to mine.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 .
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.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.
Yes I did. But there is nothing tangible to be wiped away there. Whatever there is, is flat with the glass surface.If putting water on it makes it disappear then it is some kind of surface contaminate. Have you tried to clean a spot?
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.