Navitron Renewable Energy and Sustainability Forum

SOLAR PHOTOVOLTAIC => Solar Photovoltaic Systems => Topic started by: pantsmachine on April 10, 2019, 05:40:51 PM



Title: Cleaning gains?
Post by: pantsmachine on April 10, 2019, 05:40:51 PM
Hi all,
One of the guys I am working with has oversized his 4kw system to 8kw and he swears by cleaning regularly the panels for a couple of percent gain. Online sources tout 3 to 5 % and onwards to a heady 30% improvement from dirty to clean. I am not buying into that but would be interested to hear what you guys have experienced?


Title: Re: Cleaning gains?
Post by: Philip R on April 10, 2019, 07:03:16 PM
As every day is so different from others in terms of temperature profile, cloudiness etc. Ellucidating a meaningful figure is like licking your finger and sticking it in the air and saying about +3%.
What works for me is a sunny day like today with a cool breeze. My system generated over 21kWh today from a 3.5kW install. This often betters generated kWhs from longer, hotter summer days.

Philip R


Title: Re: Cleaning gains?
Post by: marshman on April 10, 2019, 07:49:16 PM
I agree with Philip that it is hard to get a definitive figure for any gains.  My first system with Sharp panels is coming up to 9 years old (9 days to go). The panels are easily accessible and mounted at a shallow pitch of only 11 degrees. I used to clean my panels quite regularly. I did have a period early on of cleaning them every few months and noting the effect. More recently I have only rinsed them off if, as last year, we have a very prolonged dry spell. Last year May to August we had little or no rain so by the end of June they were pretty dusty. In all the times I have cleaned them I have noticed a temporary large increase in output due no doubt to the cooling effect of the cold water. If they were really dusty, as last year, then I guestimate I gain up to 10% extra output under similar conditions for a short period until they start to get dirty again. So in the peak season on a good day an extra couple of units a day. My overall annual generation has remained fairly constant - first year was 3268kWh, 9 years later and the last 12 months saw 3862kWh generated, average annual generation is  3578kWh. Trouble is early on I had problems with inverter tripping due to high grid volts so not  a true comparison. I think that panels at a more "Normal" angle than mine, say 30 to 45 degrees, should be pretty much self cleaning with sufficient rain. The only issue can be with bird poo and in some areas lichen growth has been reported to be a problem. I did notice some lichen starting to develop along the bottom edge of mine last year, a quick scrub with a brush and good rinse soon dislodged it, but left for a season or two it may be more difficult.

I suspect the 3 to 5% gain for regular cleaning may be in the ball park, but it depends on the situation of the panels and how dirty they and how quickly.

All a bit too subjective really and if you have made the effort to clean them then of course you will hope to see an improvement whether there is one or not!

Roger


Title: Re: Cleaning gains?
Post by: pantsmachine on April 10, 2019, 08:49:01 PM
Thanks for taking the time to reply lads. I am in year 1 of ownership so it's all very exciting. I am looking to see if general consensus is thumbs up or down to cleaning. I have 10 months of data so will see how it pans out post clean. Thought I'd do this first then remove a couple of panels set up elsewhere and extend the leads to simulate another part of available roof. See if 5he gains are magnificent or not.


Title: Re: Cleaning gains?
Post by: dan_b on April 10, 2019, 09:21:16 PM
If you can do it safely yourself at zero cost then by all means give them a clean on a regular basis. But if you need to get a man in to do it and pay for the effort, it probably isnít cost effective so to it more than once every few years and then only if they look really skanky.


Title: Re: Cleaning gains?
Post by: pantsmachine on April 10, 2019, 10:39:31 PM
If you can do it safely yourself at zero cost then by all means give them a clean on a regular basis. But if you need to get a man in to do it and pay for the effort, it probably isnít cost effective so to it more than once every few years and then only if they look really skanky.

Thanks Dan, bought a hose fed brush/squeegee pole and the panels are easy enough to get to without any acrobatics. Will give it a go on return to Scotland and report if improvement seen.


Title: Re: Cleaning gains?
Post by: GeoffM on April 11, 2019, 08:21:21 AM
Must admit I don't think mine get dirty, but next door has some too and has offered to clean mine when he does his. I declined, as they are at least working no - there's no telling what might happen if someone starts poking around with tools!! Leave well alone, I'd say, unless there is an obvious problem.


Title: Re: Cleaning gains?
Post by: book_woorm on July 11, 2019, 07:39:40 PM
I've had PV for a long time now, originally I did not clean my panels for a number of years and then I noticed that there was a drop in output each year from the previous one (in the order of 4% each year), which was greater than the ageing effect that everybody used to talk about when domestic PV first appeared. Nothing ventured nothing gained I cleaned my panels using a long telescopic pole with hose and brush. Lo and behold I got more output in the following 12 months than the first year after installation! Now-a-days if I don't clean them for 4 years then the drop in output becomes noticeable again but doing it every year seams like to much effort. So I now clean them every other year, also I wait after we have had the dusty Sahara rain the UK seams to get May/June time. The output has stayed up and I'm not seeing any aging effect on this 15 year old system.


Title: Re: Cleaning gains?
Post by: dan_b on July 11, 2019, 07:54:25 PM
Solar panel soiling is a thing, and a headache for owners or large solar PV farms in particular.  It clearly causes a generation drop-off, but how often should you clean them is a difficult question to solve.
Coincidentally saw this article today - seems there's a company who has produced a solution for measuring solar panel soiling.

https://cleantechnica.com/2019/07/10/what-is-the-greatest-environmental-hazard-for-solar-energy-dust/


Title: Re: Cleaning gains?
Post by: privet_hedge on July 12, 2019, 11:24:41 AM
The problem that I have had is Lichen growing on the surface of the panels. General dust is bound to stick to the panels to some extent, and bird poo is guaranteed to stick! If you have any sort of perch (TV aerial?) anywhere near the panels, then the poo builds up and gives the Lichen food to start to grow. Heavy rain will wash off a lot of grot, but Lichen sticks like....well...poo!
This will then cause a significant reduction in output. (check this forum with a search for 'Lichen' for a fuller discussion). I had to erect a scaffold tower to access my panels for cleaning, and then used a telescopic pole with a soft brush, generous amounts of water and 'Mr. Muscle' kitchen cleaner. Rinse off with a hose. That was 2 years ago, and I guess it will need repeating next year.
It is sometimes difficult to see the lichen until you get close up, although a pair of binoculars might help! I was very surprised to see just how bad my panels had got in 6 years.
Alan


Title: Re: Cleaning gains?
Post by: pantsmachine on July 14, 2019, 04:31:21 PM
I did ours 9 months after install and could see a large visual difference in cleanliness, thought they weren't quite as perky in output in the previous month to cleaning. Seeing 5kw output in best conditions now. Will do every 6 months as access is not a problem. Stepladder  and 13ft water fed extension pole with soft brush. Nice and easy does it, I noticed the panel  corners are the prime spots for build up to begin. Can see how it would impact over time.Just nature doing its thing.