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  • Microinverter confusion.. Doesn't make sense.

    I'm looking at the Enphase IQ7X specs that say the microinverter is good for panels between 320W to 460W+ but they have a maximum AC output of only 320 watts? Huh?

    That makes no sense unless you're using them above Canada or the Antarctic. So you hook up a 430 watt panel and its going to be clipping all day long???

    Am I reading this right? Who would do such a thing?

  • #2
    Originally posted by Murby View Post
    I'm looking at the Enphase IQ7X specs that say the microinverter is good for panels between 320W to 460W+ but they have a maximum AC output of only 320 watts? Huh?

    That makes no sense unless you're using them above Canada or the Antarctic. So you hook up a 430 watt panel and its going to be clipping all day long???

    Am I reading this right? Who would do such a thing?

    That seems typical based on the STC spec of panels. Panel to inverter power ratio range can go up to 1.50. You never get 100% from a 430 watt STC spec panel in the real world because the spec is done under ideal lab conditions (e.g. temp, etc.) and there is DC/AC conversion loss plus degradation due to aging. Panels usually have a separate PTC spec that is lower and based on more realistic conditions.

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    • #3
      Originally posted by solardreamer View Post


      That seems typical based on the STC spec of panels. Panel to inverter power ratio range can go up to 1.50. You never get 100% from a 430 watt STC spec panel in the real world because the spec is done under ideal lab conditions (e.g. temp, etc.) and there is DC/AC conversion loss plus degradation due to aging. Panels usually have a separate PTC spec that is lower and based on more realistic conditions.
      That is true as a general rule but there are some videos on YouTube of people in cold sunny areas getting 110% or more of the STC from their panels.
      It's still ridiculous even in warmer areas to hookup a 430W Panel to a 320W Micro Inverter. You can see clipping happening all throughout the peak sun hours. Normally this would not be an issue as there are some benefits during off peak solar hours but the cost of high quality brand name 430 or 440W panels like LG makes it an even worst pairing IMHO.

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      • #4
        Originally posted by robbyg View Post

        That is true as a general rule but there are some videos on YouTube of people in cold sunny areas getting 110% or more of the STC from their panels.
        It's still ridiculous even in warmer areas to hookup a 430W Panel to a 320W Micro Inverter. You can see clipping happening all throughout the peak sun hours. Normally this would not be an issue as there are some benefits during off peak solar hours but the cost of high quality brand name 430 or 440W panels like LG makes it an even worst pairing IMHO.
        I'm in Michigan and have some 400w QCells going and they push 350 to 380 quite frequently for hours on end.. During the cold spring, seeing 390 and 400 isn't unusual. To think that the microinverter would be clipping at 320 is just kind of ridiculous.

        I'm not sure how I feel about a company advertising a configuration that wastes so much power. Almost as if they're trying to drum up sales for a product that isn't a proper match for the panel.

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        • #5
          They usually write a whitepaper explaining that clipping is good

          I also see my panels putting out more than rating on my 10 year old panels in very cold weather with snow on the ground.

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          • #6
            Originally posted by robbyg View Post

            That is true as a general rule but there are some videos on YouTube of people in cold sunny areas getting 110% or more of the STC from their panels.
            It's still ridiculous even in warmer areas to hookup a 430W Panel to a 320W Micro Inverter. You can see clipping happening all throughout the peak sun hours. Normally this would not be an issue as there are some benefits during off peak solar hours but the cost of high quality brand name 430 or 440W panels like LG makes it an even worst pairing IMHO.
            Not sure what the YouTubers did but if they get above STC from a real world system then it's certainly notable especially if it's financially worthwhile to have larger inverters in such cases. However, I am skeptical as YouTube also has lots of "free energy" videos.

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            • #7
              Originally posted by solardreamer View Post

              Not sure what the YouTubers did but if they get above STC from a real world system then it's certainly notable especially if it's financially worthwhile to have larger inverters in such cases. However, I am skeptical as YouTube also has lots of "free energy" videos.
              U-tube == The new idiot's bible.

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              • #8
                Originally posted by solardreamer View Post

                Not sure what the YouTubers did but if they get above STC from a real world system then it's certainly notable especially if it's financially worthwhile to have larger inverters in such cases. However, I am skeptical as YouTube also has lots of "free energy" videos.
                I am also skeptical of YouTube videos as most of the people don't have any real knowledge of what they are talking about.
                With that said, we do know that junction efficiency increase when temperatures go down. I would doubt that 25C is the optimal temperature but more likely the one that they could get away with without getting ridiculed.
                I see a few YouTube videos making this claim, some of them seem credible others I have no idea. A quick search and I did find a few articles discussing the cooling effects on PV panels. It seems to line up with the claims.
                https://www.researchgate.net/figure/...fig2_259169728

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                • #9
                  Originally posted by Murby View Post

                  I'm in Michigan and have some 400w QCells going and they push 350 to 380 quite frequently for hours on end.. During the cold spring, seeing 390 and 400 isn't unusual. To think that the microinverter would be clipping at 320 is just kind of ridiculous.

                  I'm not sure how I feel about a company advertising a configuration that wastes so much power. Almost as if they're trying to drum up sales for a product that isn't a proper match for the panel.
                  I have seen this in a few of my hobbies. The company in question is lagging behind in technology so they create a spin to make their product seem to still be better than the newer products on the market. I suspect that making a Micro Inverter that can do 400 Watts reliably is a serious challenge. Compound that with the testing time needed and the rate at which Panel wattage's go up annually and your pretty much better off shooting for 550 Watts and praying your product is still relevant by time it hits the market. .

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                  • #10
                    Originally posted by robbyg View Post

                    I am also skeptical of YouTube videos as most of the people don't have any real knowledge of what they are talking about.
                    With that said, we do know that junction efficiency increase when temperatures go down. I would doubt that 25C is the optimal temperature but more likely the one that they could get away with without getting ridiculed.
                    I see a few YouTube videos making this claim, some of them seem credible others I have no idea. A quick search and I did find a few articles discussing the cooling effects on PV panels. It seems to line up with the claims.
                    https://www.researchgate.net/figure/...fig2_259169728
                    Sure cooler temperature at the same irradiance means higher PV power but in the real world those conditions don't meaningfully exist. As for the paper's focus on water cooling, it's is a common idea but I am not aware of a practical and economical water cooling solution for rooftop solar where the total cost of ownership is lower than the incremental PV production value from water cooling.

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                    • #11
                      The only thing I know that gets your panels to provide 110% of the STC is what is called Cloud Edge effects.

                      On sunny days with clouds when the sun passes through the edge of the cloud you get some refraction that can increase the amount of sun reaching the panel.
                      That will create a production burst that can exceed the nominal rating of the panel, but it is brief so it does not affects the global day production in a significant way

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                      • #12
                        Originally posted by robbyg View Post
                        A quick search and I did find a few articles discussing the cooling effects on PV panels. It seems to line up with the claims.
                        https://www.researchgate.net/figure/...fig2_259169728
                        We've discussed this point here several times before. If water cooling the panels was even the slightest bit practical for the typical install then why haven't any of the mainline companies adopted it by now? I'd much rather put up a few more standard panels to get more output than worry about liquid cooling to give me a boost. I've had two homes with domestic solar hot water systems and know what it takes in labor and cost to maintain them. No way I would ever want to liquid-cool my PV panels. Sure, maybe this cooling works for a few folks on YouTube for a short time but for 20-25 years?

                        Dave W. Gilbert AZ
                        6.63kW grid-tie owner

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                        • #13
                          Originally posted by scrambler View Post
                          The only thing I know that gets your panels to provide 110% of the STC is what is called Cloud Edge effects.

                          On sunny days with clouds when the sun passes through the edge of the cloud you get some refraction that can increase the amount of sun reaching the panel.
                          That will create a production burst that can exceed the nominal rating of the panel, but it is brief so it does not affects the global day production in a significant way
                          Yep, I remember the first few times I saw that I was pretty impressed and even tried to simulate it by shading/unshading a panel to verify but I have never seen the effect last for more than a few minutes so not meaningful. Temporary water cooling has similar effect. There is active research on adding heatsinks to PV cells which seems interesting but I wonder if it will be able to add enough value to justify the cost.

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                          • #14
                            Originally posted by solardreamer View Post

                            Yep, I remember the first few times I saw that I was pretty impressed and even tried to simulate it by shading/unshading a panel to verify but I have never seen the effect last for more than a few minutes so not meaningful. Temporary water cooling has similar effect. There is active research on adding heatsinks to PV cells which seems interesting but I wonder if it will be able to add enough value to justify the cost.
                            At this time the extra output that a "cool" panel can provide is far outweighed by the cost of the cooling system. It just doesn't make financial sense.

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                            • #15
                              Originally posted by solardreamer View Post

                              Sure cooler temperature at the same irradiance means higher PV power but in the real world those conditions don't meaningfully exist. As for the paper's focus on water cooling, it's is a common idea but I am not aware of a practical and economical water cooling solution for rooftop solar where the total cost of ownership is lower than the incremental PV production value from water cooling.
                              Evidently those conditions do exists on certain days in certain places. I don't think all those videos are a lie.
                              As for cooling the Panels with water, I know it can be done economically in some situations. I have a cousin with ground mounted panels that are very close to a stream. The problem is that unless that water has been run through and RoDi system I suspect that the amount of deposits that are going to build up on the glass make it a bad idea.

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