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    #31
    Originally posted by Besoeker3 View Post
    The obvious question is why?
    Solar is still peanuts compared to total system capacity.
    What am I missing here?

    Why does the utility limit? Or why do developers choose to clip?

    Either way, solar isn't peanuts. In the California Independent System Operator it's usually somewhere around 10 gigawatts mid-day, give or take a gigawatt or so. (EDIT: And that's just registered grid generators, it doesn't include something like another 2-5 GW of net metered systems.)
    Last edited by jaggedben; 10-19-19, 09:50 PM.

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      #32
      Originally posted by jaggedben View Post


      Why does the utility limit? Or why do developers choose to clip?

      Either way, solar isn't peanuts. In the California Independent System Operator it's usually somewhere around 10 gigawatts mid-day, give or take a gigawatt or so. (EDIT: And that's just registered grid generators, it doesn't include something like another 2-5 GW of net metered systems.)
      For me, the question remains.
      Why limit it?

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        #33
        Originally posted by Besoeker3 View Post

        For me, the question remains.
        Why limit it?
        Depending on where you are and what size system you are talking about, there are many answers. At the lower end, i.e. residential systems, some AHJ's have a limit to what size system, AC rated, they will allow a homeowner to connect to their grid. Others do not have that restriction, but have a cap on what size system for which they will pay rebates. With larger systems the cost differential for the next size up inverter can be significant so it may be cheaper to overload a smaller inverter than it is to build in a larger inverter to get the same kWh/yr production.

        As I said, you have to run the numbers to determine the best course, but overloading an inverter to clipping is not necessarily a bad idea.

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          #34
          Originally posted by Besoeker3 View Post

          For me, the question remains.
          Why limit it?
          See post 27 & 30.

          its about the maximum amps dumped on the system at any given time and production contracts.

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            #35
            OK. I'm still baffled. Free energy and clip it? But I readily accept that it is not my field.

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              #36
              Originally posted by Besoeker3 View Post
              OK. I'm still baffled. Free energy and clip it? But I readily accept that it is not my field.
              Your question has been answered numerous times, why do you keep asking?
              Ethan Brush - East West Electric. NY, WA. MA

              "You can't generalize"

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                #37
                Originally posted by Besoeker3 View Post
                OK. I'm still baffled. Free energy and clip it? But I readily accept that it is not my field.
                Post #28 answers your question. The energy is not free--it requires an upfront capital investment to be able to gather it. The question is, for a fixed dollar investment, how do you allocate that investment between panels and inverters in order to maximize the energy generation? The answer will usually be a system in which there is some clipping.

                Here's a simple example with made up numbers. Suppose you have a system where each marginal panel costs $100 installed and will produce 100 kWh/year on average, given enough inverters. Each marginal inverter costs $1000 installed and will support 10 panels without clipping. Suppose the 11th panel on an inverter produces only 98 kWh/year extra; the 12th only 96 kWh/year extra; the 13th only 92 kWh/year extra, the 14th only 84 kWh/year extra, and the 15th only 68 kWh/year extra.

                Now let's say that after fixed costs, you have $20,000 you want to spend on panels and inverters. You could do that by using 10 inverters and 100 panels, and you'd make 10 MWh/year with no clipping.

                Or you could try 9 inverters and 110 panels, that would give you 7 inverters with 12 panels and 2 inverters with 13 panels, and it would generate 10.93 MWh/year. You'd be clipping 70 kWh/year, but you generate more energy for the dollar investment than the case of 10 inverters.

                In fact let's try 8 inverters and 120 panels, that would give you 15 panels per inverter. It would generate 11.5 MWh/year. You'd be clipping 500 kWh/year, but you'd still be generating more energy for the dollar investment that the cases of 9 or 10 inverters.

                Cheers,
                Wayne

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                  #38
                  Originally posted by wwhitney View Post
                  Post #28 answers your question. The energy is not free--it requires an upfront capital investment to be able to gather it. The question is, for a fixed dollar investment, how do you allocate that investment between panels and inverters in order to maximize the energy generation? The answer will usually be a system in which there is some clipping.

                  Here's a simple example with made up numbers. Suppose you have a system where each marginal panel costs $100 installed and will produce 100 kWh/year on average, given enough inverters. Each marginal inverter costs $1000 installed and will support 10 panels without clipping. Suppose the 11th panel on an inverter produces only 98 kWh/year extra; the 12th only 96 kWh/year extra; the 13th only 92 kWh/year extra, the 14th only 84 kWh/year extra, and the 15th only 68 kWh/year extra.

                  Now let's say that after fixed costs, you have $20,000 you want to spend on panels and inverters. You could do that by using 10 inverters and 100 panels, and you'd make 10 MWh/year with no clipping.

                  Or you could try 9 inverters and 110 panels, that would give you 7 inverters with 12 panels and 2 inverters with 13 panels, and it would generate 10.93 MWh/year. You'd be clipping 70 kWh/year, but you generate more energy for the dollar investment than the case of 10 inverters.

                  In fact let's try 8 inverters and 120 panels, that would give you 15 panels per inverter. It would generate 11.5 MWh/year. You'd be clipping 500 kWh/year, but you'd still be generating more energy for the dollar investment that the cases of 9 or 10 inverters.

                  Cheers,
                  Wayne
                  And on the flip side let’s say the utility limits you on your MW export. Now theres a whole other reason to clip. More MWh but less MW

                  Comment


                    #39
                    Originally posted by Besoeker3 View Post
                    OK. I'm still baffled. Free energy and clip it? But I readily accept that it is not my field.
                    It's a matter of economics and design constraints. It can be a complex problem to solve and sometimes the best solution involves some clipping. As you say, it's not your field, so without understanding the details of the equation it may be counterintuitive for you.

                    Comment


                      #40
                      Originally posted by wwhitney View Post
                      Post #28 answers your question. The energy is not free--it requires an upfront capital investment to be able to gather it.
                      Yes, up front. As do all power stations. The difference is the ongoing fuel cost.

                      Comment


                        #41
                        often you have a higher overall system efficiency when you increase clipping because the inverter operates in a more efficient region of its efficiency curve. This does not always occur but is something to look for. Where interconnection costs are a considerable effort risk, and expense, it is often more economical to oversize the system such that there is 3-4 percent clipping.

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                          #42
                          Originally posted by ggunn View Post

                          It's a matter of economics and design constraints. It can be a complex problem to solve and sometimes the best solution involves some clipping. As you say, it's not your field, so without understanding the details of the equation it may be counterintuitive for you.
                          I would think that you'd want to compare the area under the clipped vs non-clipped curve. That will tell you the lost revenue, which you can compare to the cost of up-sizing the inverter.

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                            #43
                            Originally posted by gadfly56 View Post

                            I would think that you'd want to compare the area under the clipped vs non-clipped curve. That will tell you the lost revenue, which you can compare to the cost of up-sizing the inverter.
                            Of course; it's what I meant by "run the numbers" in post #33.

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                              #44
                              Originally posted by gadfly56 View Post

                              I would think that you'd want to compare the area under the clipped vs non-clipped curve. That will tell you the lost revenue, which you can compare to the cost of up-sizing the inverter.
                              Or compare the area lost to clipping to what is gained on the 'shoulders' by spending the same money on more PV modules, and see which is more. Just for example.

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                                #45
                                Originally posted by ggunn View Post

                                Of course; it's what I meant by "run the numbers" in post #33.
                                Yes, but measuring the area under the curves is the "how to". Without the "how to," just saying "measure it" isn't very helpful.

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