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  • Originally posted by Jest Waitn View Post
    not to rain on anyone's parade, but this thread seems to have been hijacked. not that it is irrelevant to PV systems, but perhaps this 'departure' might be moved to the new topic?
    You insisted on this by pushing for folks to weigh in on differences between string inverters and microinverters. You got your wish! Differences in monitoring, and the value of that, is an important part of the discussion.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

    Comment


    • Originally posted by foo1bar View Post

      You said "if for no other reason than their being more of them per install"

      Since you were talking about "modules", I assumed you were using the usual definition of that term. A module is what is sometimes called a "panel" - a collection of PV cells, usually 60 or 72 of them in an aluminum frame. A "module" is a good term for them as it is short and descriptive of it yet is a distinct term from the thing you put circuit breakers into.

      My best guess is that for a situation with some shade the micro-inverter or optimizer setup gets you a few percent benefit vs. a string inverter.
      Obviously it's going to change based on what kind of shading, etc.
      I don't think I've seen "hype" that a 50% shaded array you'll get 50% of the unshaded output.
      My guess is that you'd see less than 25% of the output with a string inverter (depending heavily on the type of shading)
      And you'd see a significant increase in production with microinverters or optimizers.
      BUT it'd really really really depend on the type of shading and the topology of the system.
      Understood (I think).

      I've found terminology use and assuming everyone is on the same page with definitions can be confusing if not carefully explained.

      Example: Up to about the mid point of my engineering career, I'd spent the better part of my time designing heat transfer equipment of all sorts, from power boilers to cooling towers and a lot of applications in between. So, once upon a time, some purchasing slug at a compressor co. my outfit was trying to garner business from challenged my design credentials and experience on a project proposal because there was no mention of "cooler design" on my resume, coolers being the generic term the compressor industry commonly uses for intercoolers and aftercoolers used on their products. He, not understanding that about half or more of the equipment I'd designed up to that point involved removing heat from a fluid or a process, and thus "coolers", didn't know that a "cooler" is an application more than an equipment classification, or that a "cooler" is actually more generally described as a heat exchanger. A short conversation cleared up the confusion, but his ignorance and myopic assumption caused an initial problem that might have caused a lost opportunity if not caught.

      In this thread, I should have been more aware of similar terminology confusion and the problems imprecise writing and assumptions can cause. I'll make more effort to be more careful in the future.

      Comment


      • Originally posted by J.P.M. View Post

        Understood (I think).

        I've found terminology use and assuming everyone is on the same page with definitions can be confusing if not carefully explained.

        Example: Up to about the mid point of my engineering career, I'd spent the better part of my time designing heat transfer equipment of all sorts, from power boilers to cooling towers and a lot of applications in between. So, once upon a time, some purchasing slug at a compressor co. my outfit was trying to garner business from challenged my design credentials and experience on a project proposal because there was no mention of "cooler design" on my resume, coolers being the generic term the compressor industry commonly uses for intercoolers and aftercoolers used on their products. He, not understanding that about half or more of the equipment I'd designed up to that point involved removing heat from a fluid or a process, and thus "coolers", didn't know that a "cooler" is an application more than an equipment classification, or that a "cooler" is actually more generally described as a heat exchanger. A short conversation cleared up the confusion, but his ignorance and myopic assumption caused an initial problem that might have caused a lost opportunity if not caught.

        In this thread, I should have been more aware of similar terminology confusion and the problems imprecise writing and assumptions can cause. I'll make more effort to be more careful in the future.
        cool.

        Comment


        • Originally posted by sensij View Post

          You insisted on this by pushing for folks to weigh in on differences between string inverters and microinverters. You got your wish! Differences in monitoring, and the value of that, is an important part of the discussion.
          actually, my statement concerned the significant advantage of string over micro-inverters in being the ability to employ long dc-wire runs to avoid power loss. of course the ability to tag any digital or analog device with a unique identifier in order to provide RTA of this device presents 'an advantage' over the lack to do so.

          no one actually answered the long wire run; although i now assume this is 'the' or one primary advantage.

          Comment


          • Originally posted by Jest Waitn View Post
            actually, my statement concerned the significant advantage of string over micro-inverters in being the ability to employ long dc-wire runs to avoid power loss. of course the ability to tag any digital or analog device with a unique identifier in order to provide RTA of this device presents 'an advantage' over the lack to do so.

            It isn't that they are DC power runs but that they are higher voltage. This can be done with both String and Optimized systems. Though not all string systems use high voltage. Most grid tie only systems do but most bimodal and off grid systems use 150V strings so not an advantage there (Schneider being the exception with their 600V Charge Controller). Though I hear OutBack is working on a 300V ChargeController.

            Originally posted by Jest Waitn View Post
            no one actually answered the long wire run; although i now assume this is 'the' or one primary advantage.
            If by " 'the' or one primary advantage" you mean the one or primary advantage that you are concerned with sure. Most people would consider this pretty low on the comparison chart unless they have very long wire runs.
            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

            Comment


            • Butch: Thank you for the consideration, time and effort of your response. I doubt you and I will ever entirely agree on advantages/drawbacks of string vs. other methods of converting solar PV DC to AC, but I bet reading this exchange may well enable others to gain some additional useful information and food for thought to help make more informed decisions.

              Respectfully,

              J.P.M.

              Comment


              • Originally posted by J.P.M. View Post
                Butch: Thank you for the consideration, time and effort of your response. I doubt you and I will ever entirely agree on advantages/drawbacks of string vs. other methods of converting solar PV DC to AC, but I bet others reading this exchange may well enable them to be able to gain some useful information and food for thought to help make more informed decisions.

                Respectfully,

                J.P.M.
                That was entirely my point (to give others food for thought). As I stated I have a string inverter and it was after a lot of research that I settled on Outback some of it here.

                I would love to have a SolarEdge SE3000H with DC coupled VRLA batteries but such a beast does not yet exist
                When it does come out, I will NOT be changing out my Outback for one because we seem to agree on some things like: [SIZE=16px][FONT=times new roman]don't fix what ain't broke[/FONT][/SIZE].

                Very Respectfully
                Butch
                OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                Comment


                • Originally posted by Jest Waitn View Post

                  actually, my statement concerned the significant advantage of string over micro-inverters in being the ability to employ long dc-wire runs to avoid power loss. of course the ability to tag any digital or analog device with a unique identifier in order to provide RTA of this device presents 'an advantage' over the lack to do so.

                  no one actually answered the long wire run; although i now assume this is 'the' or one primary advantage.
                  As Butch writes, The long wire loss is mostly f(voltage), not whether the line is carrying AC or DC. Higher Voltage results in lower line loss.

                  For a given amount of power transmission, higher voltage reduces the line current which is what reduces the resistive losses in the conductor. One better way to make the losses as small as desired is to use appropriate wire thickness and or material as required by specs. Making the choice of micro inverter or optimizers vs, string inverter based on line loss due to voltage drop seems a bit odd.

                  Comment


                  • Originally posted by ButchDeal View Post

                    That was entirely my point (to give others food for thought). As I stated I have a string inverter and it was after a lot of research that I settled on Outback some of it here.

                    I would love to have a SolarEdge SE3000H with DC coupled VRLA batteries but such a beast does not yet exist
                    When it does come out, I will NOT be changing out my Outback for one because we seem to agree on some things like: [SIZE=16px][FONT=times new roman]don't fix what ain't broke[/FONT][/SIZE].

                    Very Respectfully
                    Butch
                    Understood and ( perhaps) and maybe another one : Don't make things more complicated than necessary for the task. KISS.

                    Comment


                    • 600Vdc Charge Controller, Morningstar also has one too.
                      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

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

                      Comment


                      • Originally posted by ButchDeal View Post

                        If by " 'the' or one primary advantage" you mean the one or primary advantage that you are concerned with sure. Most people would consider this pretty low on the comparison chart unless they have very long wire runs.
                        i understand that most people live in the polluted urban areas on 1/4 to 1/3 acre sites. since i have long wire runs, this is high priority. the long wire runs were stated in the original post; this is the context.

                        Comment


                        • Originally posted by ButchDeal View Post


                          It isn't that they are DC power runs but that they are higher voltage.
                          and i already told someone that suggested this that i am not interested in long dc runs. too dangerous. more context added.

                          back to what i said, the only real advantage to the string is the ability to have long runs without much power loss. this is not an advantage to me, given the context.

                          Comment


                          • Originally posted by J.P.M. View Post

                            As Butch writes, The long wire loss is mostly f(voltage), not whether the line is carrying AC or DC. Higher Voltage results in lower line loss.

                            For a given amount of power transmission, higher voltage reduces the line current which is what reduces the resistive losses in the conductor. One better way to make the losses as small as desired is to use appropriate wire thickness and or material as required by specs. Making the choice of micro inverter or optimizers vs, string inverter based on line loss due to voltage drop seems a bit odd.
                            if i could transmit 480vac to the main panel and then split it or step it down, i'd do it. but not 430vdc. too dangerous.

                            as far as the line loss, this point was not made by me. it was made in this thread by another. it was suggested that the micros would have trouble when the line voltage rose above 261vac. this was something new to me. and i asked the question about string inverter response to rising voltage (261vac). more context.

                            Comment


                            • Originally posted by Jest Waitn View Post
                              and i already told someone that suggested this that i am not interested in long dc runs. too dangerous. more context added.

                              back to what i said, the only real advantage to the string is the ability to have long runs without much power loss. this is not an advantage to me, given the context.
                              Ok yes you are the king of random statements. You claimed that the advantage is that the can have less loss due to D.C. Runs. I corrected your inaccurate statement that it is not the D.C. But the high voltage that makes it have less lose.


                              it doesn't matter if you already told someone or are arrfrade of D.C., facts are facts

                              OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                              Comment


                              • Originally posted by Jest Waitn View Post

                                if i could transmit 480vac to the main panel and then split it or step it down, i'd do it. but not 430vdc. too dangerous.

                                as far as the line loss, this point was not made by me. it was made in this thread by another. it was suggested that the micros would have trouble when the line voltage rose above 261vac. this was something new to me. and i asked the question about string inverter response to rising voltage (261vac). more context.
                                Why is 430 or 600 for that matter D.C. Too dangerous but 480 AC isn't? Maybe with a string inverter without ground fault and arc fault protection but any that is approved for US installs now will have those features .

                                Microsw or string inverter trying to push 240v AC a long distance is going to be creeping up on the voltage at the inverter. Micros will not have a choice for higher D.C. Voltage but string inverters will have that option. Further they will not shut down of the D.C. Voltage is effected by the long run, but they will have to shut down if the AC voltage gets too far off.
                                OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                                Comment

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