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  • #16
    What I forgot to mention is brand new I was seeing peaks of 210 to 220 watts... so the fact that I am still seeing this 7 years later without any panel cleaning other than the occasional rain tells me the degradation is minimal. Based on specs I should be seeing a 6% loss by now and I am not.

    12 panels - 60 cell Poly - 245 Watt STC installed in 2012
    12 controllers that are 98.5% efficient @ 200 watts
    All of them showing 210-220 watts peak from the controller output with 216 average - based on spec degradation I should be seeing 196-206 watts peak....

    It all depends on cell quality and the Canadian Solar C6SP245 that I have seem to be real good.

    Just not seeing the degradation you are claiming with my panels.... not to say other foreign made ones would not have an issue.

    Cheers,

    Rob

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    • #17
      Originally posted by MPPT_Rob View Post
      What I forgot to mention is brand new I was seeing peaks of 210 to 220 watts... so the fact that I am still seeing this 7 years later without any panel cleaning other than the occasional rain tells me the degradation is minimal. Based on specs I should be seeing a 6% loss by now and I am not.

      12 panels - 60 cell Poly - 245 Watt STC installed in 2012
      12 controllers that are 98.5% efficient @ 200 watts
      All of them showing 210-220 watts peak from the controller output with 216 average - based on spec degradation I should be seeing 196-206 watts peak....

      It all depends on cell quality and the Canadian Solar C6SP245 that I have seem to be real good.

      Just not seeing the degradation you are claiming with my panels.... not to say other foreign made ones would not have an issue.

      Cheers,

      Rob
      I'm not claiming any degradation - the panel mfg. is. I'm only reporting what I've measured and a very incomplete report of how I do it as a way of showing and an example of why I and most everyone I know in the solar energy community knows that to measure panel or system efficiency, and so panel efficiency degradation as f(time) while having any hope of anything meaningful coming from the effort, a measure of the input (the POA irradiance) is necessary.

      Since you state you do not have any irradiance or wind measurement devices, I'd conclude you cannot claim to know with any quantitative or even qualitative accuracy or precision just what your panels' degradation is either on an absolute basis or a rate over time basis.

      What you seem to have is anecdotal observations based on incomplete data. That's fine as far as it goes, but ascribing more to it than that or more than can be documented is B.S.

      Comment


      • #18
        My power measurements new and recently (7 years later) would indicate the degradation is minimal. Our controllers keep track of peak power and I periodically reset that to track what an "ideal full sun" condition does. So its not BS as you state but real world data taken under real conditions 7 years apart - June of 2012 and June of 2019. Because its PEAK POWER it is going to capture the maximum on an ideal day since last reset. Knowing the actual Solar Intensity or air temperature is not that important here and being the data was taken in June both years its a moot point. If I were comparing June and December then you have an argument.... the Peak is the best day of that month in each case so the peak solar should be nearly identical as would the air temperature be within 10 degrees F.

        Fact is I am not seeing anything significant or anything to worry about as of yet.... I am also not in a hot climate which in theory would accelerate any degradation. I would expect the manufacturer warranty would take that into account.

        Re-read your original post - you did claim that Poly panels degrade faster than Mono....
        There is however no data to support that claim.

        I stand by the data taken as I am an EE with 35 years of experience in power electronics and DC-DC conversion. It was a valid measurement of 7 years of use at my location. Especially the average value of 216 watts between the 12 panels is still 216 after 7 years....

        Cheers,

        Rob

        Comment


        • #19
          I can't find the article from Kyocera But I remember reading about the degradation testing done on Kyocera panels and They were finding their cells were only degrading less than 8% over their 20 year warranty period and that degradation was mostly happening in the first half of the warranty period and that the cells had stabilized after that point, not losing any more significant output .

          MPPT_Rob What was the status of the panels you are monitoring when you first started monitoring them? New? Used? This may help explain why you're not seeing any significant degradation in your test panels.

          https://energyinformative.org/lifespan-solar-panels/
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

          Comment


          • #20
            Originally posted by MPPT_Rob View Post
            My power measurements new and recently (7 years later) would indicate the degradation is minimal. Our controllers keep track of peak power and I periodically reset that to track what an "ideal full sun" condition does. So its not BS as you state but real world data taken under real conditions 7 years apart - June of 2012 and June of 2019. Because its PEAK POWER it is going to capture the maximum on an ideal day since last reset. Knowing the actual Solar Intensity or air temperature is not that important here and being the data was taken in June both years its a moot point. If I were comparing June and December then you have an argument.... the Peak is the best day of that month in each case so the peak solar should be nearly identical as would the air temperature be within 10 degrees F.

            Fact is I am not seeing anything significant or anything to worry about as of yet.... I am also not in a hot climate which in theory would accelerate any degradation. I would expect the manufacturer warranty would take that into account.

            Re-read your original post - you did claim that Poly panels degrade faster than Mono....
            There is however no data to support that claim.

            I stand by the data taken as I am an EE with 35 years of experience in power electronics and DC-DC conversion. It was a valid measurement of 7 years of use at my location. Especially the average value of 216 watts between the 12 panels is still 216 after 7 years....

            Cheers,

            Rob
            My point remains the same. In measuring how a power generator's efficiency changes over time, or under different operating conditions, a measure of the input and the output is required at 2 or more different points in time.

            Without a measurement of input to a power generator - in this case the POA irradiance - the denominator in the right hand term of the equation : efficiency == output/input, it's not possible to get an efficiency for that device.

            Without being able to measure that efficiency with at least precision which includes ways to account or at least consistently estimate the effects of varying operating conditions that may be different at different measurement times such as panel temps., panel fouling and probably other things in some consistent way that also reflects reality as best as possible, you will not be able to determine with any reasonable accuracy how much power a solar generator's performance has dropped.

            Since you have not measured, and have no way to consistently measure the energy input to your power generators (the solar irradiance), you have no way to measure efficiency as determined by the equation efficiency == output/input, and so no way to determine or estimate performance degradation either as a stand alone measure or as a comparison against published specs.

            There's nothing wrong with the data you have. Stand by it all you want. Real world data taken under real world conditions. but as I explained above, it's just not enough to justify what you want to claim. As you admit, you have no irradiance measurements. Without that input data you cannot make any quantitative claims about performance decline or degradation, making such claims B.S.

            As for education: That's nice. Congrads on your tuition receipt. But I've learned from and mentored, as well as hired and fired P.E.s over an engineering career longer than yours. I respect your opinions and your experience, but I'm not that impressed by those who think lots of formal education somehow takes the smell out of their engineering spoor.

            Comment


            • #21
              Originally posted by littleharbor View Post
              I can't find the article from Kyocera But I remember reading about the degradation testing done on Kyocera panels and They were finding their cells were only degrading less than 8% over their 20 year warranty period and that degradation was mostly happening in the first half of the warranty period and that the cells had stabilized after that point, not losing any more significant output .

              MPPT_Rob What was the status of the panels you are monitoring when you first started monitoring them? New? Used? This may help explain why you're not seeing any significant degradation in your test panels.

              https://energyinformative.org/lifespan-solar-panels/
              FWIW, one study from NREL I've used published in 2012 and so probably a bit dated:

              "Photovoltaic Degradation Rates - An Analytical ".

              At: www.nrel.gov/docs/fy12osti/51664.pdf

              A lot of it's value for me is in the bibliography.

              Comment


              • #22
                Thanks for the input everyone!

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