the perfect weekend?

[Ferdinand]

I am waiting for @JSHarris to get a drone and invent a device to do it from the air  !

 

Whereas I am happy to put my proven technology back in the garage and relax with my Aviation cocktail.

 

That actually could be a good idea if spraying eg dilute bleach or some other chemical. Needs de-industrialising, though.

 

 

Hmmm. https://www.alibaba.com/product-detail/RJX-professional-agriculture-uav-drone-sprayer_60642902411.html

Edited April 12, 2017 by Ferdinand

[Jeremy Harris]

I had thought of just trying to clean them with a pressure washer.  I have a small one, although I've not used it for years, I might dig it out and see if it will spray up high enough.  Looking at the panels this afternoon, the sun seems to have killed off the algae and now the bottom of the panels looks like it has a layer of dirt, worse on the lower edge of the lower panels than the ones near the ridge, for some reason.  This does mean that I could probably get away with just cleaning the lower panels.

[Onoff]

Normal water leaves "mineral" streaks on glass. It's a little rough and gives purchase to algae etc over time. If glass is dirty then it really needs a detergent (Fairy's the weapon of choice) wash with a dolly then squeegee to get it off. THEN once clean you can use a pure water system to keep it clean. If glass is really stained say from concrete overspill etc which was inadequately washed off then you're down to mechanical abrasion methods like cerium oxide (jeweller's rouge).

[billt]

3 hours ago, JSHarris said:

The snag is that there is visible algal growth on our panels, plus I'm sure the peak output has dropped.  I'll try and remember to bring a camera over tomorrow and take some photos of the green stuff on the panels.

 

Last weekend we should have seen a peak of well over 6 kW, based on the peak output we've seen before in bright sunshine, yet the maximum was only around 5.5 kW.  We haven't hit the inverter limit once yet, and I'd have expected the inverter to be limiting for a couple of hours either side of midday last weekend.

 

Is the algae all over the panel surface or just at the bottom edge? Some of my ground mounted panels get green mould on the bottom edge where water stays for the longest time, but it doesn't get up to the active area of the panels, so doesn't affect the output.

 

Not reaching peak output is almost certainly due to the panels warming up. My roof mounted system very rarely gets up to the inverter output unless the day is very cold as the output is reduced due to heat. The larger ground mounted arrays reach peak output much more readily as they are in free air and stay significantly cooler.

 

You can see the difference here. The first graph is from Sunday when we had more or less unbroken sun and all the panels got warm. The 3.8kW system only reached 3.1kW while the 5kW system just about reached 5kW.

 

Today with broken sunshine, a much cooler day and some wind the 3.8kW system got to 3.77kW (about the most it ever gets too) and the other systems clipped as well..

[Jeremy Harris]

The lower panels seem to have a covering of muck that extends up over around a quarter of the panel area, and my panels have no significant inactive area around the sides, the crystalline elements are right up to around 20mm of the frame.

 

This system used to limit all the time in bright sun, usually at an indicated power of around 6.1 kW (I have 6.25 kWp of panels and a nominal 6 kW inverter).  I've yet to see them exceed 5.5 kW this year, which is noticeably lower than in past years, and something that was very noticeable last weekend, when we had clear skies with little or no cloud cover.

 

I had a good look this afternoon and will get a ladder up there tomorrow and take some photos, and try to clean the lower parts of the panels that I can reach.  They do look very mucky, and if I had to guess I'd say that algae are the primary cause, providing a sort of rough layer that has attracted more dirt and that seems to have resisted being cleaned by rain.  The fascias look to be covered in the same stuff, as do the slates on the roof.  On the positive side, it's probably indicative of good air quality, I suppose.

[SteamyTea]

Wash them when it is raining, that should rinse them off a bit more.

[Onoff]

You might be better if stuff is really stubborn, with a scrub pad on the end of the pole and indeed as said above a mild bleach solution well rinsed afterwards. On these lines:

 

http://www.windowcleaningstuff.co.uk/poles-water-fed/515-unger-indoor-scub-pad-white-ops20.html

[Onoff]

Auto solar panel cleaning. Looks like the brushes are of an Archimedes screw type profile to clean and push the debris downwards. Scrapheap hats on:

 

http://www.vjpequipments.com/?page_id=38

[Jeremy Harris]

I managed to get up a ladder this afternoon to try and get a photo that shows the (now dead) algae and dirt:

 

 

The stuff wipes off easily, I rubbed my hand over part of it and it cleaned up OK, so I think a water fed pole with a brush on the end will do the job OK.  Looking at the muck closely confirms that it is an algal growth of some kind.  My guess is that it's got a good foothold because the panels are faced with non-reflective glass (which was a planning requirement).  The whole surface of every panel is affected, although the lower 1/4 of the bottom panels is the worst bit.

 

Here's another photo looking up at the panels, with the bit I rubbed with my hand visible:

 

Edited April 13, 2017 by JSHarris

[Ferdinand]

Can you paint the surface with anything after the fact, even if more reflective?

 

Ferdinand

[Jeremy Harris]

I'm not sure.   Rain X might work, but it needs buffing off, and access to do that would be difficult, and would need scaffolding.

 

I think that the best bet will be to give them a regular clean, to prevent the build up of algae.  It's probably something that grows over the winter, so a yearly clean, at the right time of the year, may do the trick.

[Onoff]

+1 on Rain X. I used it a few times on the car screen and was fascinated driving along with the wipers OFF in the rain watching it bead off.

[ragg987]

In my experience, the beading effect of rain-x only lasts a few months on car windows, so it may be of limited use of growth takes hold after 1 year.

[Jeremy Harris]

Having been thinking about it, I think the answer is probably to get a cheap'ish window cleaning pole and just give the panels a clean once a year.  It's taken about three years for them to get to this state, so an annual clean is probably enough.  If cleaning them gets back the ~10% output that I think we've lost, then the pole would pay for itself in the first year.

[Steptoe]

On 14/04/2017 at 10:08, ragg987 said:

In my experience, the beading effect of rain-x only lasts a few months on car windows, so it may be of limited use of growth takes hold after 1 year.

But that's because you keep rubbing it off with your wipers, seriously.

 

Bob Heath is actually better, but a helluva lot more expensive,

there is other stuff that's really good, but damned if i can remember its name, it's made on the Isle of Man, 

The only other thing i can think of is "aqua" , very, VERY water repellant, not sure if it's readily available on mainland UK or not though. and again, not the cheapest.

[Onoff]

31 minutes ago, Steptoe said:

But that's because you keep rubbing it off with your wipers, seriously.

 

Bob Heath is actually better, but a helluva lot more expensive,

there is other stuff that's really good, but damned if i can remember its name, it's made on the Isle of Man, 

The only other thing i can think of is "aqua" , very, VERY water repellant, not sure if it's readily available on mainland UK or not though. and again, not the cheapest.

 

Is it this:

 

http://www.salclear.com/contents/en-uk/d37.html

 

?

[Steptoe]

6 minutes ago, Onoff said:

 

Is it this:

 

http://www.salclear.com/contents/en-uk/d37.html

 

?

That's the stuff, 

I actually wired the first proper unit they had.

[jack]

Bit late to this, but I was away on hols last week.

 

9 April was our best day since late August last year:

 

 

(Note: the graph shows Wh per 15 min interval. So, for example, between 12 and 1pm we averaged about 5.6kW)

 

Generation started at 6:30 in the morning and was still going after 7:15 that night.

 

The flattening out between 8 and 9:30 is due to shading from trees beside the house.

[SteamyTea]

10 hours ago, jack said:

Note: the graph shows kWh per 15 min interval

Isn't it Wh?

[jack]

Good spot, thanks. I've corrected it.

 

My main point was that it isn't a graph of power.

[SteamyTea]

 

Not unusual to get the best relative performance this time of year because of the combination of temperature and array angles.