Cleaning Solar Panels

[HarryHill]

Morning guys,

I'm new to this forum, and please excuse the fact that this question may have been asked (and answered) already, but I wanted to ask about the best method for cleaning solar panels. The thing is (like many people's) my original installer went bust, which shouldn't have come as a surprise to me, since I hadn't heard from them for a couple of years. Anyway, their original contract included regular cleaning of the solar panels, but since they're no longer around, I wondered if I could do it myself.

I know that it's claimed to be best to use deionized water, rather than from a tap, but I've heard several other tips (from other companies trying to sell me replacement inverters etc.) which can appear contradictory. Some have told me to sweep any loose dust off the panels first, with a dry brush. Others say just to wash it off with water. Another industry professional recently told me he uses his pressure-washer on his own panels at home.
If you look at the Karcher website, they even have a video of rotary brushes being used with detergent on the end of an extension-pole to clean solar-panels (just like you might do with your kitchen floor)!

I just wondered if there was a 'best way' of doing it, and also if there was any need to disconnect the panels from the inverter with the switches, if there was any danger of electrocution. Thanks in advance.

 

[sgt_woulds]

The requirement to clean panels is very much installation specific. Chelsfield have a very good example of this - a system fitted to a 3 storey house right next to the A2, where cleaning is not cost effective.

You can actually see the effects of pollution on the panels from the ground, but the array (Sanyo) has performed at and above predictions (pre MCS) for over 12 years.

Testing conducted at BRE for Solar Century nearly 2 decades ago found that any (quality) panel at a pitch of 10deg or more was mostly self cleaning; bird poo, dust etc. will stick to the panels, but will become friable with the heat of the day and will wash off with the next lot of rain. You can get build-up along the bottom edges of the panels, but most of the better panels these days come with drainage on the corners that ameliorates this.

As such most systems really only benefit from a wash every 3 or 4 years, but it is not vital!

However, if your panels are subject to excessive amounts of organic matter (leaves, lichen, moss etc) or they are used as handy target practice by determined birds you may need to clean more regularly to prevent burning out the cells caused by continuous solid shading.

A soft brush with a neutral cleaner or de-ionised water is the best way to clean them. Do not use detergent unless it specifically states use with PV (unlikely) since panels contain seals, mastics, plastics which may be chemically damaged by such agents. When in doubt, clean water is best.

Beware window cleaners with long brush poles - inspect their equipment before allowing them to work. I've seen panel glass scratched by such things...

Also anyone who uses a jet washer on their roof is only asking for trouble. I remember my neighbours asked the local 'handyman' to clean their roof whilst they were away on holiday - when they came back they found the whole house inside was damp and covered in muck where water had been forced in under the tiles until the ceiling broke.

Of course he was spraying up from the ground. If you got close up to a panel with a jet washer you may damage the mastic that holds the glass in place and perhaps take paint off the frames. I stripped the paint of a Jaguar that way during work experience when I was at school!

How bad are the birds near him to require a jet washer?

Turning off the PV should not required since the panels are designed for a good soaking, but it never hurts to play it safe... spraying water on panels is a 'good' way of finding DC faults. I learned the hard way!

 

[HarryHill]

Thanks for the tips. Actually, the 'industry professional' who told me he uses a pressure-washer on his own solar panels at home (whenever he's up the ladder level with the roof) had come round to try selling me a Solar Edge replacement for my Sunny Boy inverter.

He - and the staff at his company who cold-called me and booked the appointment (which was meant to last 30 min to 1 hour tops, but went on for over 3 hours, because - as he admitted - he can talk for England) all lied to me, claiming that the Sunny Boy contains an 'oil', which can evaporate in the heat of the loft and render it useless. That was the reason they claimed for needing to replace my inverter with their Solar Edge version. However, when I contacted SMA, they assured me that there in no such 'oil' in their inverter, and it's 'dry', cooling itself only by convection.

So I guess he was spouting a load of complete crap to me in general (and, according to what you've told me, he may find his own solar-panels damaged after using a pressure-washer on them). But then again, I was amazed by the video on the Karcher website, where they were using rotary brushes & detergent to wash commercial solar-panels. Surely, any dust or grit could get ground into the glass or scratch it that way (without brushing it off first with a soft, dry brush) and the detergent may be another problem.

To be honest, I'm tempted just to wait for the next typically torrential, Summer-spoiling rain-storm to do the 'self-cleaning' thing. The trouble is, though, here in Kent, we look to be set fair in the best August weather for a few years. But then again, I suppose all that sun means a lot more lecky being generated

Cheers,
Harry

 

[The Solar King]

Do us all a favour and contact RECC, the Renewable Energy Consumer Code about these people. It is not hte first time I have heard this story. This is gross mis-selling of the worst kind. Equally, your local Trading Standards Officer should be interested.

With regard to washing panels, keeping them clean, can help, but it is a matter of degree. Utility scale solar farms do this where a tiny percentage gain of a very big number is a lot of money. Seagull attack is the worst - seems to have the adhesion quality of Araldite and due to sheer volume could cause the bypass diodes in a panel to trigger.

Due to variable irradiance day to day, hour to hour and minute to minute, unless there is side by side testing of identical systems, it is difficult to know the real benefit. There are so many other variables that could effect output. If you feel it worthwhile, do it, if not, don't.

If the ones on my own home get particularly dusty and coated in summer, then they get a quick wash, otherwise, its just the Seagull attack that gets dealt with.

 

[HarryHill]

Thanks for the feedback. Yes, I may well report that company (and if they ever called me again - they'd get a piece of my mind Just out of interest, how do you go about washing your own solar-panels, and what's the trick for dealing with Seagull splat?

 

[The Solar King]

Fortunately I live in what was a bungalow that is now room in roof, so access is easy from either a dormer window or a short ladder. I use a double sided squeegee/sponge extendable window washer. If its really bad I tie a plastic scourer to a stick. Washing up liquid seems to do the trick.

 

[Worcester]

This is quite a good read:
Official Google Blog: Should you spring clean your solar panels? - https://googleblog.blogspot.co.uk/2009/07/should-you-spring-clean-your-solar.html

It's about Google's own solar panels, so you can be sure they know where and when to spend their money - They will spend it wisely.

 

[flyingsparky]

Just read this post with some interest. I have not cleaned my panels in 5 years and they perform as good as they ever did. They are at 35 degrees so the dirt tends to crust and fall away or get washed off.
We advise our clients with pitched roofs to not really worry too much unless they can see the dirt after a good soaking. Those with less of a pitch do tend to need more attention as gravity struggles to do its thing.

 

[OH-Gerd]

Just read this post with some interest. I have not cleaned my panels in 5 years and they perform as good as they ever did. They are at 35 degrees so the dirt tends to crust and fall away or get washed off.
We advise our clients with pitched roofs to not really worry too much unless they can see the dirt after a good soaking. Those with less of a pitch do tend to need more attention as gravity struggles to do its thing.

Hi there! Here in dusty Australia , I had my 8 250 watt panels cleaned after 4 1/2 years! My son did the cleaning . There was a thin layer of fungus on them.It took some effort to remove it with only a SOFT brush and lots of town water. Don't use a pressure washer. There was no visible dirt on any panel like leafs or bird poo . I am using micro invertors. After the panels had warmed up again, I measured an increase of output of 11%. PS: I have a tiled roof. OH-Gerd .