A Wee Bit of Dust Buildup Since Last Cleaning End of April...

[J.P.M.]

i'd be interested. our panels are disgusting right now. max outut hasn't touched 10 in a long time. a little disappointing. haven't attempted to clean at all with the drought and just praying that some rain comes and washes them off.

would you be interested in seeing a ratio between your system and mine before/after?

last 4 days:

6/11 75.02
6/12 72.56
6/13 74.34
6/14 73.81


only "cleaning" (hose) was in Jan 2014 and that was only one array. could not get the other one. we have not had the time or energy to do anything since. and the rain did such a nice job on its own, we have just been trying to leave it alone (not to mention water now costs $8.xx/HCF). but i think it's about time to call someone to clean.

Interested yes and no offense meant, but don't get all hurt if you don't like what you read. More later after analysis & dinner. As for cleaning I think your vendor may do it or know someone who does. That may be useful if the cleaners break something like a tile or a line.

[Volusiano]

This stuff looks pretty good, not sure if it's necessary though.

http://www.titanlabs.net/glass-gleam-solar.htm

I bought a bottle of this exact soap for my next cleaning but haven't used it yet. Will report back next time after I use it.

I didn't think soap was necessary either. But after 3 cleanings with plain water and final rinse with DI water using a water fed pole and brush, I still find a little bit of dirt remaining on the panels each time to my surprise. After the first couple of times, I told myself that I probably needed to brush and rinse more thoroughly. So the last time I brushed and rinsed pretty thoroughly, and the result were better than the first 2 times. But still some dirt was left behind when dried out, especially on the side area of my coverage where I had to reach out harder. The interesting part was that the dirt disappeared a day later after a windy day (wind must have blown it off the panels).

So I decided to try some soap next time to see if it'll help get rid of the dirt more easily or not. I'm suspecting that since my house is nearby a busy road, a railroad track, and a freeway about a mile away, maybe the dirt gets mixed up with car smoke and oily exhaust making the dirt more sticky on the panels. But the panels feel very slippery when wet and look clean when wet so you can't tell for sure if they're clean until they're all dried out.

The last few times I just used a regular brush designed for window cleaning. After the last time, I bought this brush specifically designed for solar cleaning with more fanned out bristles. I'll be using it next time with the soap to see if the new brush/soap combo will be more effective or not.

My panels are slightly dirty but not dirty enough to justify a cleaning yet. So I'm waiting. Monsoon season is coming to AZ now so if it's a clean rain, I may not need to clean at all. But if it's a dirty dust storm rain then I'll need to clean them up for sure.

[J.P.M.]

i'd be interested. our panels are disgusting right now. max outut hasn't touched 10 in a long time. a little disappointing. haven't attempted to clean at all with the drought and just praying that some rain comes and washes them off.

would you be interested in seeing a ratio between your system and mine before/after?

last 4 days:

6/11 75.02/11.76 = 6.38 kWhrs./day per installed kWatt
6/12 72.56/11.76 = 6.17
6/13 74.34/11.76 = 6.32
6/14 73.81/11.76 = 6.28


only "cleaning" (hose) was in Jan 2014 and that was only one array. could not get the other one. we have not had the time or energy to do anything since. and the rain did such a nice job on its own, we have just been trying to leave it alone (not to mention water now costs $8.xx/HCF). but i think it's about time to call someone to clean.

Comparison of results from 06/11 thru 06/14 for your array and mine appear similar to prior comparison done, as I recall, last winter.

On a per installed kW basis:

Bando J.P.M. Bando/J.P.M.

06/11 6.38 kWhrs/day per installed kW 6.56 kWhrs./day per installed kW .973

06/12 6.17 6.53 .945

06/13 6.32 6.57 .962

06/14 6.28 6.64 .946


Given how far apart the arrays are, I'm a bit surprised at the consistency of the data, if that's even the right word to use for only 4 data points.

I don't have last weeks totals yet for irradiance data. Probably closer to the middle of this week. For all I or anyone else knows your irradiance data could be a bit less than mine given I'm about 1,500 ft. elev. and you're a lot closer to sea level and also to the ocean. I'm about 20 miles inland, you're probably about half - two thirds as far.

I'll take this opportunity using the above data to make an anecdotal pitch from my "all panels are created equal" soapbox.

1.) You have Kyocera, I have Sunpower.

2.) We are located about 25 or so miles apart. My educated guess is you get a bit more morning marine layer, but you're a bit cooler in the afternoon. I have some late afternoon shading this time of yr. of about 50% after 1730 hrs. or so P.D.T.

Those days were generally cloudless. The 14th was a little choppy sunshine wise from ~~ 1100-1130 hrs. P.D.T. due to some contrails in my neighborhood, otherwise cloudless as were the other 3 days - at least at my house.

3.) My array is at 18.7 deg. tilt, 195.7 deg. az. You have 2 arrays both about 20 deg. tilt and about 45 or so deg. east and west of south if I remember correctly.

4.) Given the off south orientation of your arrays and my late afternoon shading, but my slightly more favorable orientation, and even though there are still a lot of unknowns with respect to your array and location that will never be known for those dates, I find it still interesting as I did last winter that the two panels' performance are as similar on a per installed kW basis as they it seem to be as represented by the above data, even if anecdotal and admittedly sparse.

One other point - my array was cleaned 04/15/2014, followed by a light sprinkle 04/26/2014. No rain since then, but a fair amount of morning dew as is usual around here. You mentioned your array was last cleaned in Jan., 2014. That MIGHT give my array some advantage depending on how the fouling (dirt) rates work in both arrays. I'd assume dirt deposition rates are different, your place to my place, but don't have a clue in what or how in many ways.

If I was a Sunpower salesperson and saw this data, even after I dismissed it as amateurish, I'd probably still "have some splaineen to do", even if my name wasn't Lucy Ricardo. Looks to me like more $$'s don't buy much performance enhancement, if any, and maybe even a bit less based on these data - Q.E.D. Kyocera panels have similar output to Sunpower panels under the observed conditions, for probably a lot less $$'s/Watt. Currently Sunpower around here runs about $4.35-$4.65/Watt. Kyocera about $3.70-$ 3.95/Watt to the vendor. Pay your money, take your choice.

As for fouling (dirt) measurements, I plan (hope really, depending on weather) on taking my array temps. 4 consecutive days this week (06/19-06/23 would be ideal with similar temp. and wind and irradiance), two times/day, each 12 min. on either side of the minute of minimum solar incidence angle. (The temp. measurement process takes about 6 minutes per 16 panel temp. measurements.), and measure inverter input & output at the inverter at time of minimum solar incidence angle on the array. On the morning of the 3d day, I'll wash the array.

Expect results in about a week. Film at 11, bulletins when they break.

[silversaver]

Here's the discontinued Bosch 7.1kW 23 deg tilt SW 245 deg:

last 4 days:

6/11 46.08/7.1 = 6.49kWh
6/12 47.55/7.1 = 6.70kWh
6/13 48.36/7.1 = 6.81kWh
6/14 47.03/7.1 = 6.62kWh

Hose cleaning on 06/04/2014.

I believe the panel addition has help better balance the SMA TLUS inverter's min DC requirement and raise PV min voltage so the system does wake up earlier and rest later. I also believe the 98.5% efficiency listed by SMA. It has the highest efficiency listed among inverters. The only draw back were the narrow range of MPPT and high min DC voltage requirement.

[J.P.M.]

Here's the discontinued Bosch 7.1kW 23 deg tilt SW 245 deg:

last 4 days:

6/11 46.08/7.1 = 6.49kWh
6/12 47.55/7.1 = 6.70kWh
6/13 48.36/7.1 = 6.81kWh
6/14 47.03/7.1 = 6.62kWh

Hose cleaning on 06/04/2014.

I believe the panel addition has help better balance the SMA TLUS inverter's min DC requirement and raise PV min voltage so the system does wake up earlier and rest later. I also believe the 98.5% efficiency listed by SMA. It has the highest efficiency listed among inverters. The only draw back were the narrow range of MPPT and high min DC voltage requirement.

Silver : Thank you for the #'s. FWIW, I'd believe .98+ eff. from SMA. They seem like a real work horse. Non SMA Sunpower rebranded Power One in my garage runs pretty consistently at .971 if I believe the monitor.

[bcroe]

Funny this thread came up. I recieved a flyer in the mail advertising a PV cleaning service. They advertise it at $99 though, so I'd rather do it myself.

Rain & snow are pretty regular in these parts. My panels have never been "washed",
but the snow has been pushed off many times. They still pass the "finger test', and
I detect no loss of production. Bruce Roe

[SunEagle]

Rain & snow are pretty regular in these parts. My panels have never been "washed",
but the snow has been pushed off many times. They still pass the "finger test', and
I detect no loss of production. Bruce Roe

Bruce

I found a company in the Middle East that performs panel washing using the equipment in the picture. I guess it gets pretty dusty out there in the desert.

[bando]

Interested yes and no offense meant, but don't get all hurt if you don't like what you read. More later after analysis & dinner. As for cleaning I think your vendor may do it or know someone who does. That may be useful if the cleaners break something like a tile or a line.

i can handle it if you can! J/K. yes let's try to see if any significant results come out of it. i still believe they do. what do you make of my system not reaching 10kW recently, even on the best of days?? i do recall after the last rain we had that the max output was higher on the days directly after the showers. the days are so much longer now and it's really not that warm here and my production is hovering around the same or less than two months ago.

silver - those are some great production numbers on the 7.1! how did you clean your panels two weeks ago?

JPM - thanks for putting together the analysis so far. i'll continue to update every now and then with production numbers so you can compare. when is the big cleaning day? i may schedule mine in about two weeks. so we could do now vs. after-JPM-cleaning vs. after-bando-cleaning and see if we have good conclusions.

[bando]

Given how far apart the arrays are, I'm a bit surprised at the consistency of the data, if that's even the right word to use for only 4 data points.

I don't have last weeks totals yet for irradiance data. Probably closer to the middle of this week. For all I or anyone else knows your irradiance data could be a bit less than mine given I'm about 1,500 ft. elev. and you're a lot closer to sea level and also to the ocean. I'm about 20 miles inland, you're probably about half - two thirds as far.

I'll take this opportunity using the above data to make an anecdotal pitch from my "all panels are created equal" soapbox.

1.) You have Kyocera, I have Sunpower.

2.) We are located about 25 or so miles apart. My educated guess is you get a bit more morning marine layer, but you're a bit cooler in the afternoon. I have some late afternoon shading this time of yr. of about 50% after 1730 hrs. or so P.D.T.

Those days were generally cloudless. The 14th was a little choppy sunshine wise from ~~ 1100-1130 hrs. P.D.T. due to some contrails in my neighborhood, otherwise cloudless as were the other 3 days - at least at my house.

3.) My array is at 18.7 deg. tilt, 195.7 deg. az. You have 2 arrays both about 20 deg. tilt and about 45 or so deg. east and west of south if I remember correctly.

4.) Given the off south orientation of your arrays and my late afternoon shading, but my slightly more favorable orientation, and even though there are still a lot of unknowns with respect to your array and location that will never be known for those dates, I find it still interesting as I did last winter that the two panels' performance are as similar on a per installed kW basis as they it seem to be as represented by the above data, even if anecdotal and admittedly sparse.

One other point - my array was cleaned 04/15/2014, followed by a light sprinkle 04/26/2014. No rain since then, but a fair amount of morning dew as is usual around here. You mentioned your array was last cleaned in Jan., 2014. That MIGHT give my array some advantage depending on how the fouling (dirt) rates work in both arrays. I'd assume dirt deposition rates are different, your place to my place, but don't have a clue in what or how in many ways.

If I was a Sunpower salesperson and saw this data, even after I dismissed it as amateurish, I'd probably still "have some splaineen to do", even if my name wasn't Lucy Ricardo. Looks to me like more $$'s don't buy much performance enhancement, if any, and maybe even a bit less based on these data - Q.E.D. Kyocera panels have similar output to Sunpower panels under the observed conditions, for probably a lot less $$'s/Watt. Currently Sunpower around here runs about $4.35-$4.65/Watt. Kyocera about $3.70-$ 3.95/Watt to the vendor. Pay your money, take your choice.

As for fouling (dirt) measurements, I plan (hope really, depending on weather) on taking my array temps. 4 consecutive days this week (06/19-06/23 would be ideal with similar temp. and wind and irradiance), two times/day, each 12 min. on either side of the minute of minimum solar incidence angle. (The temp. measurement process takes about 6 minutes per 16 panel temp. measurements.), and measure inverter input & output at the inverter at time of minimum solar incidence angle on the array. On the morning of the 3d day, I'll wash the array.

Expect results in about a week. Film at 11, bulletins when they break.

good points. agree with them. we were evacuated during the bernardo fire. the winds and dust were unreal those few days. can't imagine that helped much for the panels.

btw, i am finally making some progress with CSI on my state rebate. they did catch that discrepancy you and others noted on the system price and asked the installer to change it in PowerClerk. system cost was $41,000 for $3.486/W gross. i have already received the $1500 vendor rebate and taken the federal tax credit. currently we are in "incentive claim request review" status and should be getting payment within 4-6 wks.

[Volusiano]

Here's the discontinued Bosch 7.1kW 23 deg tilt SW 245 deg:

Wow, those panels look CLEAN!

[Volusiano]

I bought a bottle of this exact soap for my next cleaning but haven't used it yet. Will report back next time after I use it.

I didn't think soap was necessary either. But after 3 cleanings with plain water and final rinse with DI water using a water fed pole and brush, I still find a little bit of dirt remaining on the panels each time to my surprise. After the first couple of times, I told myself that I probably needed to brush and rinse more thoroughly. So the last time I brushed and rinsed pretty thoroughly, and the result were better than the first 2 times. But still some dirt was left behind when dried out, especially on the side area of my coverage where I had to reach out harder. The interesting part was that the dirt disappeared a day later after a windy day (wind must have blown it off the panels).

So I decided to try some soap next time to see if it'll help get rid of the dirt more easily or not. I'm suspecting that since my house is nearby a busy road, a railroad track, and a freeway about a mile away, maybe the dirt gets mixed up with car smoke and oily exhaust making the dirt more sticky on the panels. But the panels feel very slippery when wet and look clean when wet so you can't tell for sure if they're clean until they're all dried out.

The last few times I just used a regular brush designed for window cleaning. After the last time, I bought this brush specifically designed for solar cleaning with more fanned out bristles. I'll be using it next time with the soap to see if the new brush/soap combo will be more effective or not.

My panels are slightly dirty but not dirty enough to justify a cleaning yet. So I'm waiting. Monsoon season is coming to AZ now so if it's a clean rain, I may not need to clean at all. But if it's a dirty dust storm rain then I'll need to clean them up for sure.

I washed my panels today using the new Unger Solar Radius 11" brush and Titan Glass Gleam Solar soap with my water fed pole. I use this Unger HiFlo soap dispenser where you put concentrated soap inside and in the soap position the water mixes in with some soap as it passes through. I used normal house tap water for most of the cleaning and pure water to do the final rinse. The final rinse was just running the brush in one motion from top to bottom of the solar panel while the brush is still resting on the panel. I clean standing below the panels at a 23 degree pitch so there's no way I could do a contact free rinse without the brush touching the panels.

I'm not happy to report that the result didn't come out looking perfectly clean like I was hoping for. In the end after the panels dried out, there was still some streaks/thin layers of dirt still smeared on the panel, similar to when I did it the last few times without the soap, but of course the panels still look much cleaner than before. I was really hoping that the soap would have helped give me better result and solve this problem for me but it didn't. On the last row of panels closest to me, in the beginning I could see the dirty water coming down over the bottom ledge of the panel, then eventually the water looked clean. So I thought I got rid of all the dirt. But apparently not so and there was a tiny bit of dirt left.

I think the problem I have is the inability to lift up my brush to do a contact free rinse. So whatever small amount of dirt still lodged inside the brush gets smeared onto the panels again in the final rinse. I'm also beginning to suspect that the surface of the solar panels is also not the same as the surface of a normal window. The solar glass must be a little bit rougher or something, maybe to help refract more light onto the cells, but as a result makes it harder for all the dirt to slide off.

At this point I'm just going to live with this result because I'm able to get probably 90% of the dirt off already, so I won't let the last 10% bother me anymore. Those panels don't need to look perfectly clean. They just need to be clean enough for optimal production.

[silversaver]

I use this nozzle from Home Depot with softener water. This nozzle is perfect for clean solar panel

http://www.homedepot.com/p/Little-Big-Shot-Super-Nozzle-LBSR-1/202514529

I usually clean them once a month -- 10 min job.

[Volusiano]

I use this nozzle from Home Depot with softener water. This nozzle is perfect for clean solar panel

http://www.homedepot.com/p/Little-Big-Shot-Super-Nozzle-LBSR-1/202514529

I usually clean them once a month -- 10 min job.

I'm glad this solution works for you. Maybe you can get closer to your panels, so that approach is effective in your case.

My panels are stacked 4 rows x 11 columns altogether, starting near the top ridge line of my roof. If I stand at the bottom of the roof on a ladder (don't want to go on top of the roof if I can help it), the top row is at least 30 feet away from me. So spraying water via a nozzle on that top row from 30 ft away is akin to spraying water on my dirty car from 30 feet away trying to wash it. From afar it may look cleaner than when filthy with dirt, but if you come up close, it won't look so as clean. The only way to clean effectively is to brush to agitate the dirt into solution then do a proper rinse then dry by wiping off or squeegee or rinse using pure water and let the pure water dry by itself.

Regarding using softener water, my tap water is around 800 ppm in total dissolved solid (TDS) reading (very high in hard minerals like Calcium and Magnesium). I have a water softener, too, and the softened water indeed works better with soap and feels softer to bathing and washing clothes. But it's still very high in TDS even after softened (reading is the same at 800 ppm TDS). That's because the water softener simply exchanges the Calcium and Magnesium ions with the salt ions. So instead of having a high content of mineral ions, now the softened water just has a high content of salt ions. The salt ions still leave stain on my shower door glass when I let the water dry on its own. Because of that, in my case, using softener water would also leave stains on my solar panels. It wouldn't be mineral stains, but it'd be salt stains.

[HX_Guy]

Is it a two story house? Why not get up on the roof to wash them?

[Volusiano]

Is it a two story house? Why not get up on the roof to wash them?

If it were a 2 story house, I would have had no choice but get up on the roof to wash them because standing on the extension ladder to the top of the second story would be too high and unsafe. So no, it's a single level home, but with very high vaulted ceiling (15 foot high), resulting in a very high and large roof.

The first time I cleaned I got up on the roof to clean standing on the top ridge line of the roof to clean top down. Then next time I tried standing from the ladder at the bottom cleaning from bottom up. Cleaning from the top of the roof is not any better. Since my panels are 4 rows by 11 columns, when I'm on top of the roof, the bottom row is at least 25 feet away from me anyway. Spraying water at it from 25 ft away at the top is a little better but not that much better than spraying water on it 30 ft away from the bottom. It's still like trying to wash a car by spraying water at it 25 ft away, if you don't do any brushing.

Using a water fed pole to allow me to brush the panels, I still have the same problem with non-contact rinsing either top down or bottom up. Sure I can do non-contact rinse for the row closest to me, but beyond that, the pole is extended too long to be able to lift up the brush for non-contact rinsing.

Without any significant advantage cleaning from the top of the roof, I decided that it's better to clean from the bottom of the roof standing on a ladder. There are actually more advantages cleaning from the bottom: I don't have to walk on the tiles and risk breaking them, I don't have to deal with the safety harness and tethering rope, which got in the way more than I like it to be. I don't have to make the trip up and down the roof. The first time you have to climb up to the anchor point without being tethered to hook yourself up to the anchor point. The last time you have to unhook from the anchor point and go down the roof without being tethered for safety -> 2 unsafe trips.