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Washing Ash from PV Panels

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  • Washing Ash from PV Panels

    Ash + Water = Lye
    Lye attacks & dissolves alunimun

    Maybe hit the panels first with a leaf blower and then flood them with water and more water ?

    Other suggestions ?

    ( I'm currently just outside an evac warning zone for the OAK fire in northern california, but most of our ash and smoke is from the August complex 60 miles away. pic is from 1pm yesterday when I was running the generator )


    Left side is battery room, right is generator
    Generator is Lister style 1929, 600rpm diesel

    Powerfab top of pole PV mount (2) | 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


  • #2
    After so much water the lye becomes diluted to as not eat the aluminum. I say after leaf blower power wash the panels on "both sides" and hit again with leaf blower to blow dry them and cover them since you aren't getting any solar in those conditions.
    I have the exact same generator head as you on your back up. What's yours rated for? Mine is a 9 kw though don't have a Lister yet...
    Last edited by Weldman; 09-09-2020, 12:37 PM.
    1.2 kWh solar 10.56 kWh battery @ 24v in a RV


    • #3
      A couple of random thoughts:

      Any early A.M. condensate or rain on the aluminum or the glazing ?
      Check vehicle windshields for condensate.
      If such surfaces are wet from condensation or other causes, blowing may increase the evap. rate of the condensate and bond the mixture to the glass, making later removal by hosing or other means less effective.
      If so, I'd hose the panels.
      If dry, I might blow them off and call it done, at least for the next 24/48 hr. or so and hose the array after the smoke event.

      Without an aqueous mixture for the ash and some time to work, I'd think a short exposure (but just how short is short ??) is probably not too much of a problem.

      Ash that gets wet from condensate or rain and doesn't run off may start to bond w/what it gets stuck to. See chemistry books for Na + Al reactions.
      If the ash does anything to aluminum, it might be thought of as increasing the rate of passivation (the aluminum will form aluminum oxide). It won/t be shiny and pretty for as long.
      When passivation becomes corrosion is something of a matter of opinion and application. Most aluminum passivates. That's a big reason it's so corrosion resistant.

      I might also have some concern about exposed Cu or Al wiring and any condensate/moisture combo w/any ash floating around in the air or deposited on such surfaces that could be cooled below the evening dew point by thermal radiation to the night sky and form condensate but that's a less likely temp. condition under a lot of smoke.

      FWIW, some types of caustic ash that contains mostly sodium can bond w/glass and be a complete bitch to remove. About the only removal that works is with hydrofluoric acid which is highly corrosive and toxic.

      However, I believe of the group I and group II chemicals found in wood ash (Na, Mg, CA, etc.), most of it is calcium based and so probably not an adhesion or bonding problem for the glass. But if the ash does bond, I'd wonder if more difficult removal by abrasion or chemical means would harm an antirefletive surface.


      • #4
        Originally posted by Weldman View Post
        .... after leaf blower power wash the panels on "both sides".....
        Never "power wash" pv panels, the gaskets and backing sheet are not made to withstand that pressure. This AM, it's still light and fluffy, so maybe this afternoon, I'll blow them off

        The alternator on my lister is a ST-5, even though the 6hp can only do 3kw, having the extra capacity helps with unbalanced loads and surge starting. Too large and the internal cooling fan starts eating Hp.

        Powerfab top of pole PV mount (2) | 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



        • #5
          It takes time for ash to turn water caustic, in the 30 seconds it takes the water to run down the panels and drip off, nothing is going to happen.. Hit it with the leaf blower, flood them with water.

          Better yet, use a leaf blower to get the bulk off, then an air compressor to get anything remaining.. then flood with water.

          Don't forget to do the bottoms as well.


          • #6
            Not sure how much ash you have on your panels. Today I washed 10 out of 14 of my panels. (Kept 4 dirty for a comparison). Didn't make as much difference to generation as I expected. This after... what 4 days of ash fall, in Oakland CA.



            • #7
              What would have been more valuable is see the individual panel monitoring of all the panels to see the production difference between the clean panels and the dirty ones.


              • #8
                Everyone's smoke/ash stories will be different.

                FWIW, my observations:
                Zip: 92026.
                Last array thorough cleaning: 09/04/2020.
                Hazy smoke started 09/07/2020.
                Average daily actual array output 09/07 - 09/12/20: 21.69 kWh.
                Average daily actual output for those same dates for years 2014 - 2019: 27.39 kWh.
                Max. possible average daily clear sky output for same dates: 31.98 kWh.

                All figures reflect a 3.5 % reduction in output due to late afternoon shading loss.

                So, comparing the most recent 6 days output in a very smoky situation to the historic output for the same 6 dates, 2014 - 2019, array production is down 1-(21.69/27.39) = ~ 20.8%.

                On clear days, I estimate the array fouling using a method I've developed and described previously. Long, boring story. The last thorough cleaning was done the day after the last of a series of daily cleanings done from 07/01/202 - 09/03/2020. At that time (09/04), after 66 daily cleanings and 65 measurements of array output and parameters, as well as a lot of weather measurements including irradiance taken at the minute of min cos(solar incidence angle) on very sunny days during that 65 day period, I believe the array was as clean as it's possible to get it. I measured and defined the array fouling as == zero on that day's (09/04/2020) cleaning.

                On 09/11/20, after no daily cleaning since 09/04/2020, I measured the array fouling using my usual methods as 0.061, that is, dirt/dust/smoke/soot on the array impaired performance by ~ 6.1 % from what it would have been if the array was as clean as it was on 09/04/20, the last thorough cleaning.

                On 09/12/20, I hosed the array in the A.M. at a ~ rate of 4l/panel, 16 panels, 64 l total water, 2 rinses, using no special methods/brushes/soaps, etc. - just 2 rinses with a hose from above the array at a rate of ~ 3 GPM. The array fouling at the minute of min. incidence angle for that day ~ 5 hrs. after those rinses measured out at ~ 1.8% or so. That reduction in fouling from 6.1% down to 1.8 % by simple hosing alone seems to be in reasonable agreement with prior measurements I've made and reported here - that is that simple hosing on a regular basis can restore ~ 2/3 - 3/4 of the performance lost by fouling.

                After doing this daily measurement stuff with and without daily cleaning for most clear days for the last ~ 6 yrs. or so, I estimate that without rain or cleaning, my array fouls at a rate of something like ~ 0.75 - 0.90% per week under normal conditions, with the total fouling perhaps leveling off at somewhere between 8% and maybe 10 % w/out rain or cleaning.

                Simple hosing may be something folks in smoked up areas may consider as a workable means of not only keeping arrays reasonably clean during/after smoke events but also as a way to avoid getting ripped off by cleaning scams that are always present and probably more common now in light of recent events/fires/etc.



                Take what you want of the above. Scrap the rest.


                • #9
                  I'd add to my last post to this thread:

                  The measured total Global Horizontal insolation (GHI) at my location for the period 09/07/2020 to 09/12/2020 was 27.39 kWh for the 6 days per m^2 of horizontal surface

                  The sum of the average measured Global Horizontal Insolation for my location for the period 09/07 thru 09/12 inclusive for the 6 prior years I've been measuring it was 34.08 kWh for the 6 day period per m^2 of horizontal surface.

                  The sum of the extraterrestrial horizontal insolation (immediately above the earth's atmosphere) for the same dates = 56.15 kWh per m^2.

                  27.39/34.08 = ~0.804. So, at my location, for the period 09/07/2020 through 09/12/2020, all the smoke in the atmos. reduced the GHI received at the ground by ~ 20 % or so from the average amount received over the prior 6 years for the same 6 day period.

                  For those who may be interested, the average daily Clearness Index (C.I., or K,t as it's usually referred to in the literature) at my location for the dates 09/072020 to 09/12/2020 was 27.39/56.15 = ~ 0.488.
                  The average daily C.I. for the prior 6 yrs. for the same dates was 34.08/56.15 = ~ 0.607.

                  As for reductions in array output, the effect of smoke/dirt manifests in 2 ways. The first is from reductions in received insolation due to atmospheric attenuation. The second is from increased fouling of the panels from the increased deposition of dirt/soot/ash /smoke onto the array over and above what would normally be deposited on the array.


                  • #10
                    In the SF Bay area, the worst ash cloud days this week (9th and 10th), the production of my 6kW array was about 100W during the best part of the day, with an hour reaching 300W.
                    The day production was only 4% of a normal day (96% loss)