Advice on cleaning PV panels

[forrest1]

This thread prompted me to see if LG had any advice for my LG305N1C-B3 panels; from the online installation manual:

http://www.lg.com/us/commercial/documents/LG-commercial-solar-installation-instruction-UL-B3(N)-141113.pdf

"
After Installation
...
• Removal of dirt from the front glass can increase
output.
• Water, ethanol or a conventional glass cleanser
with a micro-fiber cloth can be used for regular
washing or rinsing of the front glass to remove
dust, dirt or other deposits.
• Aggressive and abrasive cleansers or chemicals
such as alkali chemicals including ammonia based
solution should not be used on cleaning the module.
• Always wear rubber gloves for electrical insulation
while maintaining, washing or cleaning panels.
• Deposits of foreign material on the frame surface
can be cleaned by using a wet sponge or cloth and
dried in air or by using a clean chamois.
..."

I hope this helps. While I'm tempted, I really don't see myself climbing up on my sloped roof very often.

[Mike90250]

And did you notice that it is always the windshield.

The windshield in a car is made of 2 layers of glass with a plastic sheet in between.
So a windshield can not really be compared with an solar panel.

A solar panel has a tempered glass last time I checked.

Well, have fun and let us know if there are any failures. All we can do is give advice on what we know.

Tempered glass is very strong, but also very brittle, and if a crack starts, it nearly instantly converts all the glass to marble size fragments.
Windshield glass is also very strong, heat molded to a curve, and plastic bonded to another sheet of glass for even more strength, but it is NOT tempered. Most of the side and rear windows are tempered, and not heated as much as the windshield is. I'll
wash my panels to avoid thermal stress and now you have told us how you want to wash yours. Fair enough.

[bcroe]

Unless you wash your panels at night without lights, then there
is gonna be voltage in the arrays which might be dangeous (especially the DC).

I have measured the voltage under a full moon and clear sky; it was less than 10V for
a 350V array. You will need a heck of a light to produce much voltage, and then it will
probably only hit one panel which here could only do 37 Voc. Bruce Roe

[Johann]

Over the years, I've seen many cars with a single stress crack across the windshield. one out of 10,000 maybe. It does not happen often, but why invite it happening at all? Early morning, with dew still on the panels, the crud is soft and washes off easily. I have pond water, no mineral content, and so here I can skip the DI rinse. While in Los Angeles, I had to use the DI rinse.

And did you notice that it is always the windshield.

The windshield in a car is made of 2 layers of glass with a plastic sheet in between.
So a windshield can not really be compared with an solar panel.

A solar panel has a tempered glass last time I checked.

[silversaver]

Does that mean there is no danger? Or, that there is no time when there is less danger?

I can look out the window and tell when the system is producing 7000 watts or 20 watts.
I have actually gone out and measured voltages at night, seeing less than 10 volts,
have you? Bruce Roe

Unless you wash your panels at night without lights, then there is gonna be voltage in the arrays which might be dangeous (especially the DC). No, I have not measure the voltage at night, but it shouldn't any voltage during night time if any. I have water in J Box and I email my installer during weekend and it got taking care first thing Monday.(they knew that is dangeous) Anything you do in life involves with different level of dangerness, then you assume your own risk.

[Mike90250]

What happened without the DI rinse?

White hard water spots on the panels, and they are very difficult to remove.

[bcroe]

Dummy Short for Washing

I'm thinking, maybe there ought to be equipment for people who want to wash panels
at night. Open the double pole disconnect switch, close a dummy shorting load to
clamp the voltage. This load might have LED or other indicators to indicate the level
of any continuing potential. Bruce Roe

[bcroe]

no really.... when there's enough lighting, the voltage is already there.

Does that mean there is no danger? Or, that there is no time when there is less danger?

I can look out the window and tell when the system is producing 7000 watts or 20 watts.
I have actually gone out and measured voltages at night, seeing less than 10 volts,
have you? Bruce Roe

[DanKegel]

What happened without the DI rinse?

[Mike90250]

Over the years, I've seen many cars with a single stress crack across the windshield. one out of 10,000 maybe. It does not happen often, but why invite it happening at all? Early morning, with dew still on the panels, the crud is soft and washes off easily. I have pond water, no mineral content, and so here I can skip the DI rinse. While in Los Angeles, I had to use the DI rinse.

[silversaver]

Maybe standing in water washing a system operating at 400 volts is a dangerous thing to do?
Bruce Roe

no really.... when there's enough lighting, the voltage is already there.

[bcroe]

[QUOTE=pleppik} "don't wash your panels during the day" is pretty much forum-standard advice[/QUOTE]

Maybe standing in water washing a system operating at 400 volts is a dangerous thing to do?
Bruce Roe

[J.P.M.]

It just struck me that "don't wash your panels during the day" is pretty much forum-standard advice, but I'd never heard of anyone actually damaging their panels this way. It seems logical that it could happen, but the more I thought about it the more it seemed that any module design likely to break in this way would probably shatter from natural causes long before its 25-year design life.

There was even a guy in Australia who posted videos to this forum a few months ago of a water cooling system for his modules, and he didn't seem to have a problem with breaking panels. So is "don't wash your panels during the day" just an urban myth, or have there been actual solar modules shattered from heat stress?

I've heard that there are some commercial and utility-scale arrays where they regularly wash the panels. I wonder what protocols they've put in place?

Tell you what: wait for a 90 deg. F. day with clear skies and no wind, then go hit your panels with full flow from a hose about 2 P.M. and report back on the results.

[silversaver]

Like most substances, glass expands as it heats up and shrinks as it cools. It also has moderately low thermal conductivity. And it's hard but brittle. These three facts are why glass can crack when suddenly cooled. Sudden changes in temperature are commonly known to cause glass (and other materials) to break.

most or all panels are with tempered glass which is fine, but I rather not take the chance.

[pleppik]

I have a feeling those showers happen in other parts of the world as well. As do hailstorms and hurricanes. Every situation is different. The probability of a panel cover cracking due to thermal stress is unknown to a large degree, but hitting a hot panel with a hose seems a moron's invitation to a disaster.

Why take the chance ?

It just struck me that "don't wash your panels during the day" is pretty much forum-standard advice, but I'd never heard of anyone actually damaging their panels this way. It seems logical that it could happen, but the more I thought about it the more it seemed that any module design likely to break in this way would probably shatter from natural causes long before its 25-year design life.

There was even a guy in Australia who posted videos to this forum a few months ago of a water cooling system for his modules, and he didn't seem to have a problem with breaking panels. So is "don't wash your panels during the day" just an urban myth, or have there been actual solar modules shattered from heat stress?

I've heard that there are some commercial and utility-scale arrays where they regularly wash the panels. I wonder what protocols they've put in place?