How do you clean your panels?

[reader2580]

I need to clean the panels on the roof of my detached garage. How do you guys clean your panels? The entire one side of the my roof (32 feet wide by 17 feet) is covered with panels. The city and fire chief allowed me to cover the whole side of the roof with no walkways since they don't vent detached garages in case of fire.

I was looking at 16 foot painter's poles at the store yesterday, but none of them seem very sturdy at 16 feet. I didn't buy one because the window cleaning heads with threads would not fit on any of the really long poles. I was thinking about standing on the other side of the roof to clean, but then I couldn't use the squeegee to get the water off. I would like to avoid cleaning from a ladder if possible.

[Mike90250]

I just use a hose with a jet nozzle (sweeper nozzle) It just barely gets the stream lofted above the highest panels, and just the impact of the water gets the bird poop off. The panels are at enough of an angle to let water run off, don't need a squeegee. if you have hard water, one of the DI Rinse car wash kits to prevent spotting might be useful.

[J.P.M.]

After experimenting with a lot of different cleaning scenarios over the last 4 + years and making what I think is a professional attempt at measuring the results in terms of restoration of a clean condition and performance for each method, several times, I've got a lot of data that suggests (for my location), while soap and water and cloth scrubbing and rinsing/drying/windexing/buffing will get things clean(est), I've found that once cleaned that way, a simple hosing will restore almost as much lost performance (I'd estimate >75% or so) as any other method, including the more complicated methods just described.

Bottom line: Clean the array with dish soap and rinse with plain tap water from a hose. Then, every 4 weeks or so, if it doesn't rain, hose the panels with tap water straight from a hose from the top to the bottom of the array at a rate of ~~ 1.5 gal. per panel and let the array drip dry. Doing so may hold the fouling penalty to something like 2 -3 %.

DO SO EARLY IN THE MORNING BEFORE THE ARRAY GLAZING HAS BEEN HEATED BY THE SUN.

if interested, some observations/fill in info:

1.) Without rain, my array's performance falls off at a rate of approx. 1% per week due to dirt/dust/guano/etc., generally what I call array fouling, or simply fouling.

2.) Rain will clean the panels, including most of the guano smaller than an owl skrock. As might be expected, depending on the intensity and duration of the rain, it may restore all of the unfouled performance or a little, or, most likely, something in between. The recent 3.62" of rain on my array over about 2 days or so, accompanied by some, but not a lot of wind, took the fouling from about 9% performance penalty to close to zero, or nominally clean. Lots of rain gets most of the dirt off. Less rain not so much. More than that is hard/impossible to quantify.

3.) Morning dew, depending on how heavy that dew is, can have some cleaning effect. For several years I observed that the 1%/week fouling seemed to become asymptotic at ~ 6% or so and stay at about that level. I also noticed that a heavy dew will produce ~~ 0.01" to 0.02" of measureable precipitation in the rain gauge on my roof, produce roof dripping, array wetness (top and underside both BTW), wet windshields and some small puddles in the driveway. That, BTW, is about in line or reasonable agreement with what I calculate as condensation potential on a surface when nite sky radiant temps., dew points and wind are considered. On measuring array performance on such days, there was often a noticeable (but difficult to quantify in a hard way) improvement in array performance from any series of immediately prior and recent measurements. While this qualifies as only slightly better than anecdotal (if even that much), it would perhaps help to explain the asymptotic behavior of the increase in array fouling as f(time) I've logged and documented.

4.) I believe I cannot detect a difference in measured performance of an array that has been soap washed/brushed/rinsed with tap water and one that has been soap washed/brushed/rinsed with distilled water. That is, I can't find a measureable difference in performance by using distilled water, or probably D.I. water either, as a final rinse, with the distilled water rinse leaving no water spots. I've observed hard water spots left behind by tap water rinsing as Mike notes, but as hard and as much as I've looked and combed the data I've collected, I can't see a performance or fouling penalty from hard water spots. If it does exist, which I kind of doubt, I'm pretty comfortable saying it's probably less than the 0.75% or so that I feel comfortable claiming as my +/- tolerance for array fouling estimates. If so, that 4 week hosing schedule I suggest will probably take care of it, or at least make it hard to measure. As it turns out, the transmittance of group IIA chemicals that mostly make up the stuff that makes water hard and leave spots, is pretty high in the wavelengths of solar radiation that PV panels need. That makes the eye not the best judge of what is happening in terms of what hard water spots do to PV performance.

Take what you want of the above. Scrap the rest.

[reader2580]

These panels are used and came very dirty to start with. I should have cleaned them before installation, but circumstances didn't allow that. It has rained quite a bit since installation in October and they are still dirty.

This is probably more of a one time thing than ongoing. Will just water from a hose really clean them up?

[J.P.M.]

These panels are used and came very dirty to start with. I should have cleaned them before installation, but circumstances didn't allow that. It has rained quite a bit since installation in October and they are still dirty.

This is probably more of a one time thing than ongoing. Will just water from a hose really clean them up?

Depending on the nature and extent of the fouling, water from a hose will probably remove some/a lot of it. You've got nothing to lose by a hosing. As I wrote, I've found that for my array, once "deep cleaned", hosing ~ 1X/month when it doesn't rain will restore most of the performance lost from dirt, etc.

If the panels have not been cleaned in some fashion in the past, or in a long time, I'd speculate it's possible that some of the fouling may be of the type that has etched the glass or got baked on over a long time period, and you may be stuck with some more/less permanent performance penalty. Impossible to say for sure.

I'd try some glass cleaner - windex , blue squirtum' type - a soft cloth, and some gentle persistence on a small area, but no abrasives and no very hard scrubbing to see if the fouling is dirt that can be removed or if it's something of a more permanent nature. Anti reflection coatings (ARC's) are pretty durable but can be damaged by harsh chemicals and abrasion. I'd be more inclined toward more soft scrubbing with less applied force and more time rather than more applied force and less time.

If the glazing surface cannot be restored by cleaning, at least a 1X/month or so regular hosing will help to limit further deterioration in performance from more dirt accumulation.

[bcroe]

These panels are used and came very dirty to start with. I should have cleaned them before installation, but circumstances didn't allow that. It has rained quite a bit since installation in October and they are still dirty.

This is probably more of a one time thing than ongoing. Will just water from a hose really clean them up?

If your panels are configured in series strings, It would be much electrically safer to clean
them when it is completely dark. Bruce (rains a lot here) Roe

[J.P.M.]

If your panels are configured in series strings, It would be much electrically safer to clean
them when it is completely dark. Bruce (rains a lot here) Roe

Except when your sight is diminished by the reduced light and you lose your footing on the roof and mean ol' mr. gravity shortens the distance between you and the ground.

[bcroe]

Except when your sight is diminished by the reduced light and you lose your footing on the roof and mean ol' mr. gravity shortens the distance between you and the ground.

Yea, pick your poison. Death by falling, or electrocution? I will add this to my list of advantages
of a ground mount. Bruce Roe

[SunEagle]

Yea, pick your poison. Death by falling, or electrocution? I will add this to my list of advantages
of a ground mount. Bruce Roe

+1 for the ground mount.

[J.P.M.]

Yea, pick your poison. Death by falling, or electrocution? I will add this to my list of advantages
of a ground mount. Bruce Roe

Given my druthers, from an engineering, practical, and most every other standpoint, I'd prefer a ground mount hands down. Full stop.

However, and probably mostly because housing was chosen before any PV/retrofit considerations, I'd bet that about 90+ % of all residential systems are not ground mounted. Therefore, the castor oil is administered as a roof mount.

Ya' deal with the situation as you find it. Your situation, while not unique, is quite a bit different than Joe & Jane Sixpack's.

[littleharbor]

Given my druthers, from an engineering, practical, and most every other standpoint, I'd prefer a ground mount hands down. Full stop.

However, and probably mostly because housing was chosen before any PV/retrofit considerations, I'd bet that about 90+ % of all residential systems are not ground mounted. Therefore, the castor oil is administered as a roof mount.

Ya' deal with the situation as you find it. Your situation, while not unique, is quite a bit different than Joe & Jane Sixpack's.

Do they even make 6-packs anymore?

[reader2580]

My original plan was to go full ground mount. The solar guy who helped me with the installation convinced me to mount the panels on the roof of my garage. He said it would be less expensive and even if I paid his employer full price to remove and reinstall panels that I would still be ahead.

However, my solar guy found a local company that does helical ground mounts. The supports are helical anchors spun in with a skid steer auger attachment. I used this style of ground mount for an additional 12 panels that are yet to be wired up. I most likely would have done all of my panels this way if I knew about it earlier. I have lots of open land since I have three acres.

[bcroe]

However, my solar guy found a local company that does helical ground mounts. The supports are helical anchors spun in with a skid steer auger attachment. I used this style of ground mount for an additional 12 panels that are yet to be wired up. I most likely would have done all of my panels this way if I knew about it earlier. I have lots of open land since I have three acres.

I can't use the easy ways , because of all the rock below the first half foot, must dig it out. But with
my own mini equipment, its not costly. Bruce Roe


PVSep17rock2.JPG

[littleharbor]

That's some fine looking topsoil ya got there anyway.

[frankiek3]

Don't use dish soap if they have a protective coating. Car wash soap should be fine though.