Wax residue on my new/used Sunpower panels. How to clean it off safely?

[Sarah F]

Hi everyone,

Newbie here! LOL
My partner and I are in the beginning stages of installing a solar rooftop. We bought a pallet of 30 SunPower 435 panels that had been decommissioned from a solar farm. They were filthy when we got them. After cleaning them off with water, detergent, and a rag mop, we discovered that there is a scummy, somewhat reflective residue on the panels. Detergent and water do not wash away the scum. Neither does window cleaner or rubbing alcohol. Vinegar attacks the scum and turns it somewhat hazy. Mineral spirits and/or WD-40 seems to clean away the scum, and then alcohol after that cleans away the remaining oils. (However, some scum seems to remain protected inside the dimply pits of the surface.) The scum can also be wiped away with some hard rubbing with a paper towel. (Please see the two photos - uncleaned scum with a bit rubbed out with a paper towel; a portion of the panel cleaned with mineral spirits.)

My conclusion is that this was some sort of hot wax that was applied to repel rain and what must have been a considerable amount of dust from a farming operation.

My questions are these:

1. Does my conclusion seem reasonable that this is wax? If so, would anyone have any idea what sort of wax might be used commercially on a solar panel? I am frankly surprised they have been treated with wax.

2. How do I safely clean it away without compromising the antireflective coating on the glass? The most challenging part might be getting to the pits in the dimply surface. Ideas???

Thanks, everyone!

 

[Sarah F]

I guess it would help if I posted pictures! Haha...

Here's the scummy film towards the bottom of the two pictured cells (but really everywhere on the panel to a lesser extent). I rubbed the area over the cell on the left with a paper towel:



And here is the area I cleaned with mineral spirits. It is mostly clean, but some scum still remains in the little pits of the pebbled antireflective surface:

 

[Sarah F]

So I talked with SunPower tech support today. They stressed that my approach should be much more chemical than physical (e.g. abraisives / polishes). I can use a pressure washer up to 1500 psi. They had no recommendations as to whether mineral spirits or floor wax stripper would damage the antireflective coating. They confirmed that the antireflective coating is a resin, but they don't know what sort. Polyurethane???? (Does anyone know?) We discussed the possibility of using floor wax stripper and then power-washing off. They said they thought it sounded promising, but of course I need to test a small area first.

Any guidance from anyone would be greatly appreciated. In particular, does anyone know what the textured anti-reflective coating is made of???

 

[pollenface]

Distilled water and a brush.

 

[shopman]

So I talked with SunPower tech support today. They stressed that my approach should be much more chemical than physical (e.g. abraisives / polishes). I can use a pressure washer up to 1500 psi. They had no recommendations as to whether mineral spirits or floor wax stripper would damage the antireflective coating. They confirmed that the antireflective coating is a resin, but they don't know what sort. Polyurethane???? (Does anyone know?) We discussed the possibility of using floor wax stripper and then power-washing off. They said they thought it sounded promising, but of course I need to test a small area first.

Any guidance from anyone would be greatly appreciated. In particular, does anyone know what the textured anti-reflective coating is made of???

I also am running some used 435 watt Sunpower panels probably from the same source. Water and a microfiber cloth is all I used to wash them down and I was able to remove most of that residue. Don't obsess too much about it. I'm getting full rated output from the panels with just six panels powering our entire house. Can't wait to see what happens after I get the other support structure built and have 9 more panels contributing to the cause. I'm amazed with just how well these panels work and glad to know they'll maintain output to 92.5% after 25 years. I'll probably die before these panels will. Lol.

 

[Supervstech]

Hi everyone,

Newbie here! LOL
My partner and I are in the beginning stages of installing a solar rooftop. We bought a pallet of 30 SunPower 435 panels that had been decommissioned from a solar farm. They were filthy when we got them. After cleaning them off with water, detergent, and a rag mop, we discovered that there is a scummy, somewhat reflective residue on the panels. Detergent and water do not wash away the scum. Neither does window cleaner or rubbing alcohol. Vinegar attacks the scum and turns it somewhat hazy. Mineral spirits and/or WD-40 seems to clean away the scum, and then alcohol after that cleans away the remaining oils. (However, some scum seems to remain protected inside the dimply pits of the surface.) The scum can also be wiped away with some hard rubbing with a paper towel. (Please see the two photos - uncleaned scum with a bit rubbed out with a paper towel; a portion of the panel cleaned with mineral spirits.)

My conclusion is that this was some sort of hot wax that was applied to repel rain and what must have been a considerable amount of dust from a farming operation.

My questions are these:

1. Does my conclusion seem reasonable that this is wax? If so, would anyone have any idea what sort of wax might be used commercially on a solar panel? I am frankly surprised they have been treated with wax.

2. How do I safely clean it away without compromising the antireflective coating on the glass? The most challenging part might be getting to the pits in the dimply surface. Ideas???

Thanks, everyone!

How much were they?
Can you post a source for them?

 

[Bobert]

If it’s actually wax it should wipe right off on a hot summer day

 

[shopman]

This was one source for them but they appear to be out of stock:

Pallet Of Used Sunpower 435 Watt Solar Panels. Free Shipping Anywhere In

wattsmonocrystallinesolar.com

A guy that's close to me bought hundreds of them and sells them on Craigslist so I was able to get mine locally which has its benefits. No shipping issues or costs, and I was able to cherry pick and test every panel before loading them up and driving away.

 

[pollenface]

If it’s actually wax it should wipe right off on a hot summer day

yeah, I have done that with a dry clean cloth