Anyone with good cleaning tips?

[Volusiano]

i would be very interested in seeing the results of your study! i requested access to the slideshow...

your photo also shows exactly what is happening on mine, however on mine the caked-on dirt is a straight line covering the bottom 5-6" of the panels, not just the corners. the caked on dirt just looks terrible. it has been WEEKS here without any drop of rain, and the panels are pretty dusty again. we are planning some spring cleaning ourselves with some pressure washing and window cleaning and will probably have them do the panels just for our own research's sake this time.

I'm curious on what the pitch of your roof is? Maybe if your roof is not pitched steep enough, and the rain is not hard enough and long enough, then the dirt on the top part of the panel simply gets moved to the bottom part of the panel.

Also, if I remember from your picture, you do have panels lined up in 2 rows one on top of the other, right? Do you have caked on dirt on the top row panels, too? Or just on the bottom row panels? Just curious to see whether it's a problem of too many stacked panels resulting in dirt from the top row panels accumulating at the bottom row panels, or whether it's just a panel by panel issue.

[bando]

I'm curious on what the pitch of your roof is? Maybe if your roof is not pitched steep enough, and the rain is not hard enough and long enough, then the dirt on the top part of the panel simply gets moved to the bottom part of the panel.

Also, if I remember from your picture, you do have panels lined up in 2 rows one on top of the other, right? Do you have caked on dirt on the top row panels, too? Or just on the bottom row panels? Just curious to see whether it's a problem of too many stacked panels resulting in dirt from the top row panels accumulating at the bottom row panels, or whether it's just a panel by panel issue.

i'm sorry, i'm very bad with these things. all i know is that the tilt is 24 degrees and the azimuths are 159 and 249. i don't know which array is which azimuth.

it's a pretty standard pitch, nothing too crazy but nothing flat either. part of the reason we didn't utilize more of the backyard roof is because there are multiple roof "sections" with varying pitches so (1) it would look bad and (2) the lower sections of the roof don't have ideal pitches.

yes, the larger array is two rows of 18 panels across, however there is a very small gap between the two rows, the same gap that exists between each panel side by side. so condensation that runs off the top row just drips underneath, unless the water flow is great enough that it "jumps the gap" coming down (which is the case when you hose off Row 1). i don't know much about various mounting differences. we have Unirac TileTrac mounting if that helps.


it could be the area i live in is just kind of dusty - there are some newer developments within 1-2 miles in all directions of me (literally west, east, north and south), even though my neighborhood has been established for quite some time. i imagine dust and dirt can travel pretty far, esp with the occasional santa ana wind conditions. i just didn't know it until i had solar panels on there.

[bando]

forgot to add that Row 1 and Row 2 show the same amount of caked on dirt. so it doesn't appear that Row 1 is making Row 2 worse.

also, the larger array faces more to the west that the backyard array, and the larger one appears to be significantly dirtier. so that probably has something to do with wind directions and patterns too ...

[J.P.M.]

i'm sorry, i'm very bad with these things. all i know is that the tilt is 24 degrees and the azimuths are 159 and 249. i don't know which array is which azimuth.

it's a pretty standard pitch, nothing too crazy but nothing flat either. part of the reason we didn't utilize more of the backyard roof is because there are multiple roof "sections" with varying pitches so (1) it would look bad and (2) the lower sections of the roof don't have ideal pitches.

yes, the larger array is two rows of 18 panels across, however there is a very small gap between the two rows, the same gap that exists between each panel side by side. so condensation that runs off the top row just drips underneath, unless the water flow is great enough that it "jumps the gap" coming down (which is the case when you hose off Row 1). i don't know much about various mounting differences. we have Unirac TileTrac mounting if that helps.


it could be the area i live in is just kind of dusty - there are some newer developments within 1-2 miles in all directions of me (literally west, east, north and south), even though my neighborhood has been established for quite some time. i imagine dust and dirt can travel pretty far, esp with the occasional santa ana wind conditions. i just didn't know it until i had solar panels on there.

FYI: 0 deg. is north, 90 east, 180 south, 270 west.

[silversaver]

i'm sorry, i'm very bad with these things. all i know is that the tilt is 24 degrees and the azimuths are 159 and 249. i don't know which array is which azimuth.

it's a pretty standard pitch, nothing too crazy but nothing flat either. part of the reason we didn't utilize more of the backyard roof is because there are multiple roof "sections" with varying pitches so (1) it would look bad and (2) the lower sections of the roof don't have ideal pitches.

yes, the larger array is two rows of 18 panels across, however there is a very small gap between the two rows, the same gap that exists between each panel side by side. so condensation that runs off the top row just drips underneath, unless the water flow is great enough that it "jumps the gap" coming down (which is the case when you hose off Row 1). i don't know much about various mounting differences. we have Unirac TileTrac mounting if that helps.


it could be the area i live in is just kind of dusty - there are some newer developments within 1-2 miles in all directions of me (literally west, east, north and south), even though my neighborhood has been established for quite some time. i imagine dust and dirt can travel pretty far, esp with the occasional santa ana wind conditions. i just didn't know it until i had solar panels on there.

Bando,

Thanks for update the orientation of your arrays. So we know they are 24 deg tilt, large array facing SW249, smaller array facing SE159. Your installer's estimation of annual power generation 18200kWh seems to be a reasonable estimate. (some think your installer under estimate your production.... for some reason.....regardless of either SAM or PVWatt the estimation is fair). Your daily output of 50kWh is super!! My 6.63KW Bosch facing SW245 with 23 tilt only producing around 24kWh daily (I have a hill above my house from SW240 all the way up to the NW which kill the late afternoon production).

I'm using the softener water and seems to does the trick. I look at my panels next day and haven't see any water spot as using hard water. It looks like the the panels love collecting dust for just one night, I'll try not to think about the dirt for while........

[J.P.M.]

Welcome back. Hope all's well. The short answer is yes. More to follow shortly.

01/13/ and 01/14/2014 were about as close to identical and cloudless as may be possible to get. I washed my array 01/14/2014 at about 0715 hrs. with a soft cloth, water and a 10ft. pole. the job took about 30 min. The array was assembled 10/02-10/03/2014. There was some mist and fog, but no rain between installation and 1st cleaning. The array was dusty w/ more dirt along the bottom 9-12 in. of the panels when cleaned. the array is 4 X 4 in landscape.
There is a Davis Instruments Pro 2 Plus weather station located about 3 ft. north of the centerline of the array about 1 ft. higher than the highest point of the array. The Davis instrument records all the usual weather variables including wind speed and also global horizontal irradiance. Weather variables are recorded at 1 min. intervals on a continuous basis. The solar array output is measured and recorded at 5 min. intervals, with linear interpolation at 1 min. intervals.

Between the hours of 0930 and 1430 P.S.T. for the 13th (dirty) the irradiance in the plane of the array was 97,201 Watts. The array output to the grid was 17,542 Watts.
Between the hours of 0930 and 1430 P.S.T. for the 14th (clean) the irradiance in the plane of the array was 97,608 Watts. The array output to the grid was 17,642 Watts.

If adjusted for ambient temp. and the effects of wind on the array which it is assumed changes the array temp. and hence output, the output on the 13th would have been about 17,465 Watts. The 14th was warmer and less windy, thus the array would likely have been a bit warmer with correspondingly lower array output if the temp. and wind profiles on the 13th had been those of the 14th.

Using the adjusted output on the 13th, the dirty system efficiency was : 17465/97201 = .1797.
Using the Unadjusted output on the 14th, the system efficiency was : 17642/97608 = .1807.

From the above I estimate that cleaning the array (I believe thoroughly) , resulted in an increase in system efficiency of approx. : (.1807/.1797) -1 = .0056, or roughly somewhere between ~~ .5% and 1.0% penalty for an array with 3+ months of dirt on it.

There's a lot more to this and anyone who wants to know more can send me a P.M. I just don't want to bore folks w/gory details.

I'm not claiming this is typical or predictive. It's simply what I got as described above. The whole issue of array "fouling" is one of those things that is not now and may never be amenable to analysis. The array next door to me may well be and probably is different in how quickly and the mechanisms by which it fouls.

I plan on doing this about every quarter or so. I'll advise results.

[Mike90250]

...... we are planning some spring cleaning ourselves with some pressure washing and window cleaning and will probably have them do the panels just for our own research's sake this time.

The gaskets on the PV panels are NOT rated for the force of a pressure washer, and you ARE likely to screw them up. I'd try a carwash kit with the soft brushes and lots of water flowing to prevent the grit from scratching.

[bando]

The gaskets on the PV panels are NOT rated for the force of a pressure washer, and you ARE likely to screw them up. I'd try a carwash kit with the soft brushes and lots of water flowing to prevent the grit from scratching.

whoops, sorry for the confusion - i meant we are pressure washing the house, not the panels. we usually have some areas of the roof done (east and north facing sections) where green algae has built up from prolonged time in the shade as well as pressure wash the white stucco walls around the house and landscaping. then we follow up with window cleaning, and we will ask them to wash and squeegee the panels...

[bando]

thought you all might like to see actual pics of the dirty panels ...

i hosed off the panels two weeks ago (Jan 11) in the afternoon. not one drop of rain in that time period , and no rain in the immediate forecast. i can't really comment on output loss since this past week has been partially cloudy, and yesterday was very cloudy from morning til evening and only produced 19.61.

here is what it looked like this morning you can see from the far away photo that there is just this brown haze on the bottom of each panel . and of course on the close up photos you can see how dirty/dusty each panel really is. might have to hose it off again this evening.

dusty1.jpgdusty2.jpgdusty3.jpg

[silversaver]

That is pretty normal in this season. You should be glad your panels are much easier to clean from ground level unlike mine.... try not to look at them haha. As you see, the panels are spread out in 4 rolls (can't see the 4th roll, at bottom). It makes them harder to clean from ground. It required a tall ladder to do the cleaning job..

[silversaver]

I got this today with Locus monitoring and comfirm the same result with SMA inverter. It is now Jan 2014 and it is no way to get that kind of output, it must be the light reflection from clouds. Now I know if under good sun light my 6.63kW DC can generates the output of 5.97kWh instantaneous power.

[J.P.M.]

I got this today with Locus monitoring and comfirm the same result with SMA inverter. It is now Jan 2014 and it is no way to get that kind of output, it must be the light reflection from clouds. Now I know if under good sun light my 6.63kW DC can generates the output of 5.97kWh instantaneous power.

I agree with your conclusion about cloud reflections. The solar irradiance monitor located about 3' north of my array records @ 1 min. intervals. Today it has regularly recorded readings in excess of 800 Watts/m^2 horizontal irradiance. Peak was 852. Under cloudless conditions that reading could be expected to be no more than about 650 W/m^2 Max. @ solar noon ( ~~ 12:01:53 P.S.T), this day at this location in zip 92026. Before noon mostly cloudy. Things cleared some after noon probably ~~ 60-70% cloud cover in the P.M. My system output was also quite a bit higher than expected for intermittent 5 min. periods.

[bando]

i haven't looked at mine today but wonder if i got the same spikes. when they were brand new i got up in the 10's on a 11.76 system. but i really don't see anything past the high 8's anymore.

did you get rain last night? our panels are looking much better after the first rainfall in weeks, maybe almost 2 months. maybe that might have a little bit to do with it. we've had mostly clouds today with patches of full sun. yesterday was dreadful though - only produced about 16.xx kwh.

[J.P.M.]

i haven't looked at mine today but wonder if i got the same spikes. when they were brand new i got up in the 10's on a 11.76 system. but i really don't see anything past the high 8's anymore.

did you get rain last night? our panels are looking much better after the first rainfall in weeks, maybe almost 2 months. maybe that might have a little bit to do with it. we've had mostly clouds today with patches of full sun. yesterday was dreadful though - only produced about 16.xx kwh.

Bando: You don't usually see past the 8 kW power right now mostly because the sun's zenith angle (complement of elevation angle) is greater than when you had the system installed. Dirt may have a BIT to do w/it also. Zenith angle is also a big part of the reason why you'll likely see larger power readings in May for non May-gray days. and through most of the summer.

[bando]

Bando: You don't usually see past the 8 kW power right now mostly because the sun's zenith angle (complement of elevation angle) is greater than when you had the system installed. Dirt may have a BIT to do w/it also. Zenith angle is also a big part of the reason why you'll likely see larger power readings in May for non May-gray days. and through most of the summer.

i hope so, but it only took about 3 days after turning on to get from the 10's to the 8's.