Washing panels revisited.

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mcgivor
mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
Looked back on posts and comments regarding washing panels, there were various opinions on what or what not to use to clean with but nothing with measured performance gains, so today I conducted an experiment to see for myself. Recently there has been an escavator working upwind creating dust which had left a light coating, not enough to see from a distance but visible close up.

Took a current reading before and after each panel was washed using plain water and a sponge/squeegee. Did this in the morning before they are too hot, each panel read 3.4A to 3.6A before washing and post wash measured 4.7A to 4.8A. readings taken 30 second after wash. Took another reading 15 minutes later to confirm the cooling effect didn't skewer the results, the readings were the same as the post wash, so a gain of around 1.1 amps per panel, that is a 30% improvement in peformamce.

One member claimed that anything other than leaves or shadows was negligible and washing was not necessary, I beg to differ, personally I like to put figures behind my claims if possible, hense the experiment. So my opinion is to keep panels clean for best peformamce.
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.

Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    In the morning,as the sun rises, power is going to increase.  15 min shows up in my logging,
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
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    mike95490 said:
    In the morning,as the sun rises, power is going to increase.  15 min shows up in my logging,
    Understandable, they were in fact a little higher but only about 0.1A per panel, and there is the question of clamp on ammeter deveation, collectively over the array that would be noticed more, in my case the post wash current was 10A higher.If only I could stop the world from revolving for 15 nimutes.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
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    Mid day, High Noon , should give more repeatable results...  but you would have to negate the morning incoming solar  (cover the panels) to keep the temp down
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • BB.
    BB. Super Moderators, Administrators Posts: 33,532 admin
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    "Cooling" will affect Vmp (assuming MPPT based controller). Imp/Isc current is much less affected by temperature (and Imp/Isc very slightly drops as panels cool). So array current would be the optimum to see how much improvement you get from washing.

    Doing the test around solar noon would make sun positioning less of an issue.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
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    The morning was chosen as it was cool, 25 deg C same temperature as the water used,  have read that it's not advisable to wash  when hot, must admit i didn't think of shading as westbranch suggested. The result supprised me though and along with all the other maintenance this will become yet another task, when off grid it is a marrige with your system, you have to keep it happy, or so I have learned.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • jimmyaz
    jimmyaz Registered Users Posts: 114 ✭✭
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    While I agree that a cleaner panel would surely give a slightly more power.   But I don't think 30%.  I have done this many time, since my panels are on the ground.  I clean one set and run right in to see if it increase much.... but it only increase 5-10 watts for 600watts rated panels.

    :)

    But well, this is all depend on how dirty the panels is...  hard to say. 
  • dexter12353
    dexter12353 Registered Users Posts: 19 ✭✭
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    This is part of our struggle on our property...we have quads and side-by-sides so every time some friends come over and ride around for a few hours my 1000w of panels are usually covered pretty thick...If only there was a system that washed them automatically.....


    luckily my system is a tracking system and I can set the panels in a vertical position and just stand in front of them to clean them.  I'm glad I didn't put all my panels butted against each other otherwise I'd probably have to walk on them to clean them....
  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
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    Just washed mine today, sun almost set; dish detergent in a garden sprayer.  Pollen has been real bad here, I do see a difference in power output I think it was around 10-20%.  I've got large oak and other hardwood trees.  Most times I just use water sprayed from the ground.  When using the soap, my sprayer is low pressure and I climb up on the roof (single story.).  I also keep a hose on the roof.
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • dexter12353
    dexter12353 Registered Users Posts: 19 ✭✭
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    dennis461 said:
    Just washed mine today, sun almost set; dish detergent in a garden sprayer.  Pollen has been real bad here, I do see a difference in power output I think it was around 10-20%.  I've got large oak and other hardwood trees.  Most times I just use water sprayed from the ground.  When using the soap, my sprayer is low pressure and I climb up on the roof (single story.).  I also keep a hose on the roof.
    do you dry off your panels?  I was thinking any minerals in the water would cause hard water spots on the panels...Do you have those kinds of issues?
  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
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    dennis461 said:
    Just washed mine today, sun almost set; dish detergent in a garden sprayer.  Pollen has been real bad here, I do see a difference in power output I think it was around 10-20%.  I've got large oak and other hardwood trees.  Most times I just use water sprayed from the ground.  When using the soap, my sprayer is low pressure and I climb up on the roof (single story.).  I also keep a hose on the roof.
    do you dry off your panels?  I was thinking any minerals in the water would cause hard water spots on the panels...Do you have those kinds of issues?

    I have city water for this job (well water for specific uses.)
    Bird poop spots get removed from washing, panels look clean without hard water spots.
    Tried a brush/water applicator once but started to think I could scratch them if not real careful.  Drying might create a problem with scratches also.

    And again, this is not a regular task, only when pollen collects and is not removed by rain.
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
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    Washing a ground array is no big deal, in the dry season I wash mine about once per month with a sponge/squeegee and plain water, takes 10 minutes, just a form of general maintenance. Rainy season it pretty much rains every night so no need then, but if I had mounted on athe roof, which was tie initial plan, they would probably never get washed, my choice to go ground was more for electrical maintenance reasons and I have plenty of space. Some information in link.
    https://evergreensolar.com/how/cleaning/
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
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    Adding one extra panel to the array would add more than enough to offset the need to wash the panels it seems. I'd rather add a panel than fall off a roof and be out of commission for a period of time. It's like the old to track or not to track debate. The cost of a good tracking set up will be more than adding a panel in a lot of cases and will not net any more power.
  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
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    Lumisol said:
    Adding one extra panel to the array would add more than enough to offset the need to wash the panels it seems. I'd rather add a panel than fall off a roof and be out of commission for a period of time. It's like the old to track or not to track debate. The cost of a good tracking set up will be more than adding a panel in a lot of cases and will not net any more power.
    This is OK for new or flexible systems.  However. I thought the discussion was, should an existing system be washed.
    In my case, grid tied, I installed largest system allowed by utility based on my electrical KWH usage from previous 365 days, (prior to design). 

    So it's obvious to all of us, clean panels are providing more power than dirty panels, all other parameters being equal, weather  :-) it's 1% or 30% is probably debatable without hard data.
    Sure, falling off a roof has it's drawbacks (I googled it), so it is not in my plan.

    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,077 ✭✭✭✭✭
    edited June 2017 #15
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    Sure, falling off a roof has it's drawbacks (I googled it), so it is not in my plan.

    Did it mention that the fall isn't as bad as the sudden stop at the bottom:  :o 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
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    LOL exactly, you can fall from miles up without any harm at all. It's that last inch that kills you.

    I would think it was obvious without measuring it. Transparent materials transmit more light than translucent ones or opaque ones. Hint: Don't use paint on the panel fronts to get the colors you like to match the house, there are already colored panels available.
  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    edited June 2017 #17
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    This year, rain has kept my panels clean enough until recently.
    Saturday, at Solar Noon, I cleaned my panels for the 1st time this year, I gained 10%.
    I used warm water to dissolve the crud quickly.
    The previous panel was drying before I was even finished with the next panel.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
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    The valley of the Sun is quite a dusty place in summer.  I only use a hose and water to "rinse" the panels early in the morning to avoid the thermal shock as much as possible.
  • animatt
    animatt Solar Expert Posts: 295 ✭✭✭
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    I believe it is good practice to clean panels with water that is similar in temperature to the solar panel. This usually happens while they are cooler. (not in direct sun). 

    This can reduce thermal shock to the glass. 
    Your heating your water first helped. 

    But throwing bucket of 50f water on a 150f panel is probably not a great idea.  Just a consideration for casual readers whom may happen upon this thread. 
  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
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    A 100 degree difference won't make a difference really, and the water will reach the temp of the panels almost instantly.
    To break a glass, you need to heat it to around 500 degrees and then submerge it in ice water quickly. I used to make glasses out of jars with this method and even then, you need to score the glass heavily first.
  • animatt
    animatt Solar Expert Posts: 295 ✭✭✭
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    What about glass that has imperfections.  It may not be visible but why risk it. 

    I had a car with a small chip /crack in the windshield. One winter morning without thinking I started car up and had heat going to the windshield. When I went back to the vehicle a few minutes later. The small issue I had beckoned now more immediately attention. 

    You can assume everything works and will work as designed, but why not treat your stuff more gently.  Even with a warranty I would rather not deal with that process if I could avoid it. 

    I guess I error on the side of caution and having good practices.  In general I believe those are the things we should promote.  

  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
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    I'd agree that cleaning panels out of direct sun is wise for a number of reasons.

    - hard to clean bird bombs, dead bugs, etc when it dries too fast.
    - full sun causes glare and hurts my eyes.
    - standing in a pool of water with panels at full current may be safe, but I'm chicken.
    - I wilt at much over 75°f. Shade is cool.

    @Lumisol is probably right about the panels standing up to the thermal shock. A squall can go from full sun to buckets of cold rain or hail in seconds, which is probably worse. Still, I'd prefer to be elsewhere in the circumstance.

    The ability to handle thermal shock likely depends some on the initial state. Strange things happen to stuff at temps <-40°f or so.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    edited June 2017 #23
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    Ratio absentis, impulsum, quando praecepta

    Incidentally, -40 is the same in Fahrenheit and Celsius.
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
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    Wow. Latin. You must be aiming for a wide audience there.

    I'm aware of how °c relates to °f. Not everyone here does though, which is why I normally specify.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
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    LOL
    Latin is after all the base for English, so most know it.
    I am not sure they still teach it in schools, but I have taught my kids just as I learned.
    I was pointing the temperature thing out to those that did not know it, as you say, not everyone does. :)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,532 admin
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    While panels are supposed to be OK to hit with cold water on a hot day--It is not something I would recommend either.

    I used to evaluate disc and tape drives decades ago. And just the simple temperature cycling twice a day (within product specification) fairly quick ramps (something like 20 minutes from 40F to 120F)--And within two weeks of this, about 80% of the commercial products (at the time) would fail. Traces delaminate, solder joints fail, flex circuits delaminate, surface mount components pop-off, etc.

    Solar panels have lots of laminated layers--And the amount of stress that can happen from shock cooling one side and thermal mass on the other side of a "layer"--Lots of bad things can happen.

    Because solar cells are (especially now) extremely thin, and the backing is plastic (with low thermal mass, low heat transfer capability), running a hose on a hot panel is probably not the worst thing that could be done (with a well designed/manufactured panel).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
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    That's comparing apples to oranges. Did the disks actually break or just become unreadable? In my experience, the discs become unreadable as the data is corrupted by tiny migrations on the surface as the substrate expands and contracts.
    That is not a thing that can happen to a piece of glass. If fact, that is the reason that the new data storage methods use glass crystals to store data. 


    https://www.theverge.com/2016/2/16/11018018/5d-data-storage-glass

    It is also not a thing that can happen to the glass over your PV panels. And it's certainly not anything worth worrying about.

    Ratio absentis, impulsum, quando praecepta
     ;) 

  • BB.
    BB. Super Moderators, Administrators Posts: 33,532 admin
    edited June 2017 #28
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    Mostly, physically broken electrical connections from thermal cycling (not thermal shocks, but reasonably quick ramping of temperature).

    - Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
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    Oh, sorry, I read the other post as discs and not disc drives. Yeah, I'd expect that from a drive too. In normal use they never experience climate changes that fast since they are in a relatively climate controlled setting indoors, a lot different than a panel face up in the sun that gets cold rain dumped on it or hail.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    I generally wash my panels first thing in the AM, while they are still damp from overnight dew.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,