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  • AC Solar Panels....and HYBRID...... myth??

    I recently stumbled across this great forum several days ago after I had an
    epiphany about designing, building, and implementing a variation of the 'off grid' solar
    system.

    During my thoughts (usually while in the hot tub, looking over the beautiful Blue
    Ridge mountains of western North Carolina - I'm not complaining! ), I came to the
    question that while we have the common 12v solar panels(I have a couple on my
    motorhome), and other variations, why don't we just move toward 120v output panels ?
    Yes, I guess we can, and do, in a way, with micro-inverters , or even the newer
    micro-inverter 'integrated' AC Panels , which I recently found, and which sound like a
    great way to build a grid-tie system.

    I really want to get feedback, though, about any 'myths' related to the usage
    and deployment of micro-inverters, or AC Panels, in a HYBRID grid-tie, with
    battery-backup, system , which is what I'm leaning toward, but without the 'large bulky'
    battery-based inverter, as normally needed, if that's possible.

    Now, a little background: I'm not out to get ' the man ' - I actually used to be ' the
    man ', as a mayor of by small hometown in another state, with it's own electrical system.
    I saw first-hand the electric department's cost for maintenance, repair, and emergency
    response, and developed an understanding of why we pay what we pay for the constant
    electrical flow that we expect, though our system charged even less per kwh than most.
    I also own a diesel pusher motorhome, which is a variation of the battery-backup
    off-grid type of electrical system, with the ability to tie-in to 120v 'shore power', via it's
    shore power CORD and ATS(automatic transfer switch), when available, the addition of
    12v Solar panels on the roof to recharge the House batteries, via a solar controller, and
    the onboard 120v Generator to use for those situations and times where large loads are
    needed when off-grid, such as air conditioning and water heating, or during overnights
    when the batteries fall to a level requiring recharging.

    It's a beautiful thing, really, especially when you add the option of the
    AGS(automatic generator starter) to round out the ability to easily remain 'off-grid' for
    days, if not weeks, with little 'work' involved in switching between power sources.
    Today, though, I have the desire to move toward a more sustainable and more
    permanent 'off-grid' cabin lifestyle, similar to the motorhome, where the ability to move
    away from reliance on ' the man ' for PRIMARY power is the goal, but not to be totally
    removed, using the grid as more of the backup to the backup batteries, using a
    generator for the 'emergency' side of the equation, such as the loss of the grid, with
    snow, ice, and cloud cover for three days straight.
    My 'myth' concerns are surrounded by the idea of moving away from the typical
    inverter 'box' that we are all know and love, and more toward a simpler and more
    streamlined equipment list. Can micro-inverters and/or AC panels provide this
    solution , or will the battery-based inverter 'box' always be needed in the HYBRID
    scenario?

    I suppose we are missing charge controllers at each micro-inverter to handle the battery
    charging, and a 120v battery bank(10 - 12v batteries in series, etc) to 'trick' the
    micro-inverters to continue, even when a grid power loss, and to also do away with the
    need for a battery-based inverter, of course...
    Maybe MYTH is the incorrect word, but the question is really one of simplicity
    and ease-of-build for this type of situation. What I want is:
    -Solar to be the main 120v output , during peak sun-hours, of course
    -Battery bank as the secondary, for 'overnight', or otherwise off-peak hours power
    -Grid power for 240v power needs , during off-peak hours
    -and the Generator as the 'emergency' power source
    ...with the optional ability to sell back power during peak hours, if any, of course.
    MYTH??
    Last edited by sdold; 12-06-2018, 10:16 PM. Reason: Fixed truncated post

  • #2
    Originally posted by NCmountainsOffgrid
    it even truncated my response I TYPED!!
    Please calm down. I told you that some characters are recognized as spam.

    Don't use apostrophes. The software does not like it if the post comes from an iphone. Also using "cut and paste" can be an issue depending on what you first wrote it in.

    Comment


    • #3
      Originally posted by NCmountainsOffgrid
      if you'll provide me a way to send it to you, maybe you can post it for me
      Unfortunately we do not have any private messaging on this forum so everything must be posted.

      What is strange is that I read one of your posts which was quite lengthy and detailed concerning using 120V AC inverters matched to each panel. I can't seem to find that post anywhere so it might have been erased by our Spam Software.

      Sorry for the inconvenience. I hope you will be able to complete your post to your satisfaction.

      What I do remember from that post was you were hoping a battery system could fool the micro inverters into thinking the grid was up so they would keep producing. Unfortunately the anti island protection for grid tie inverters can't be fooled by a "grid" substitute.
      Last edited by SunEagle; 12-06-2018, 08:18 PM. Reason: added last part

      Comment


      • #4
        Originally posted by SunEagle View Post
        ..
        ...............................
        Unfortunately the anti island protection for grid tie inverters can't be fooled by a "grid" substitute.
        I agree this should not be tried by an amateur. I have seen professional installations using AC coupling that do control grid tie inverters. They operate through a gateway that provides all the anti islanding protection to anyone downstream. Is that something that is prohibited from discussing on this forum?

        Comment


        • #5
          Originally posted by Ampster View Post

          I agree this should not be tried by an amateur. I have seen professional installations using AC coupling that do control grid tie inverters. They operate through a gateway that provides all the anti islanding protection to anyone downstream. Is that something that is prohibited from discussing on this forum?
          We do discourage the DIY people that look for ways to Cheat the POCO. Doing something illegal usually means taking shortcuts that are dangerous.

          There are grid tie inverters that will work a small percentage of their full capability (SMA makes one type) but until a grid tie inverter that will work 100% when the grid goes down, is safe and UL listed and can be purchased by anyone, I would say the technology is not available and people should please not even try to experiment with one.

          There are also professional people that can install an AC grid tie inverter but then again you need to make sure you get approvals from your POCO and AHJ before doing so.
          Last edited by SunEagle; 12-06-2018, 10:56 PM. Reason: added last sentence

          Comment


          • #6
            Originally posted by NCmountainsOffgrid View Post
            I recently stumbled across this great forum several days ago after I had an
            epiphany about designing, building, and implementing a variation of the 'off grid' solar
            system.

            During my thoughts (usually while in the hot tub, looking over the beautiful Blue
            Ridge mountains of western North Carolina - I'm not complaining! ), I came to the
            question that while we have the common 12v solar panels(I have a couple on my
            motorhome), and other variations, why don't we just move toward 120v output panels ?
            Yes, I guess we can, and do, in a way, with micro-inverters , or even the newer
            micro-inverter 'integrated' AC Panels , which I recently found, and which sound like a
            great way to build a grid-tie system.

            I really want to get feedback, though, about any 'myths' related to the usage
            and deployment of micro-inverters, or AC Panels, in a HYBRID grid-tie, with
            battery-backup, system , which is what I'm leaning toward, but without the 'large bulky'
            battery-based inverter, as normally needed, if that's possible.

            Now, a little background: I'm not out to get ' the man ' - I actually used to be ' the
            man ', as a mayor of by small hometown in another state, with it's own electrical system.
            I saw first-hand the electric department's cost for maintenance, repair, and emergency
            response, and developed an understanding of why we pay what we pay for the constant
            electrical flow that we expect, though our system charged even less per kwh than most.
            I also own a diesel pusher motorhome, which is a variation of the battery-backup
            off-grid type of electrical system, with the ability to tie-in to 120v 'shore power', via it's
            shore power CORD and ATS(automatic transfer switch), when available, the addition of
            12v Solar panels on the roof to recharge the House batteries, via a solar controller, and
            the onboard 120v Generator to use for those situations and times where large loads are
            needed when off-grid, such as air conditioning and water heating, or during overnights
            when the batteries fall to a level requiring recharging.

            It's a beautiful thing, really, especially when you add the option of the
            AGS(automatic generator starter) to round out the ability to easily remain 'off-grid' for
            days, if not weeks, with little 'work' involved in switching between power sources.
            Today, though, I have the desire to move toward a more sustainable and more
            permanent 'off-grid' cabin lifestyle, similar to the motorhome, where the ability to move
            away from reliance on ' the man ' for PRIMARY power is the goal, but not to be totally
            removed, using the grid as more of the backup to the backup batteries, using a
            generator for the 'emergency' side of the equation, such as the loss of the grid, with
            snow, ice, and cloud cover for three days straight.
            My 'myth' concerns are surrounded by the idea of moving away from the typical
            inverter 'box' that we are all know and love, and more toward a simpler and more
            streamlined equipment list. Can micro-inverters and/or AC panels provide this
            solution , or will the battery-based inverter 'box' always be needed in the HYBRID
            scenario?

            I suppose we are missing charge controllers at each micro-inverter to handle the battery
            charging, and a 120v battery bank(10 - 12v batteries in series, etc) to 'trick' the
            micro-inverters to continue, even when a grid power loss, and to also do away with the
            need for a battery-based inverter, of course...
            Maybe MYTH is the incorrect word, but the question is really one of simplicity
            and ease-of-build for this type of situation. What I want is:
            -Solar to be the main 120v output , during peak sun-hours, of course
            -Battery bank as the secondary, for 'overnight', or otherwise off-peak hours power
            -Grid power for 240v power needs , during off-peak hours
            -and the Generator as the 'emergency' power source
            ...with the optional ability to sell back power during peak hours, if any, of course.
            MYTH??
            There's a lot of stuff in your post.

            First off, most modern systems do use higher voltage PV arrays. 300 volts is a pretty common target. (120V would work too; wiring is more expensive though,) They then go to a grid tie inverter. For off grid systems, closer to 120 volts is generally the target since 150 volts is the "sweet spot" for charge controller maximum voltage.

            Next, 120V DC works from the panels - but not for distribution. There's no safe way to distribute 120 volts DC with existing electrical hardware. A few companies are working on 370/400 volt distribution for data centers and the like, but these are not common, and there aren't much in the way of standards.

            You can certainly do an AC coupled system, where microinverters convert to 120/240VAC and then a larger central inverter manages the system. In about a year Enphase is coming out with the IQ8 line which will do this fairly seamlessly, and can use smaller battery modules rather than large central inverters. However you will pay even more for the smaller battery modules than you will for the large central inverter. ($1900 for a 1.2kwhr battery vs $1800 for a 3600 watt 'central inverter.')

            You could do everything you want with a Radian based system, including two power inputs (grid and generator) and battery system. That assumes a 48 volt battery system. (Your choices are really going to be 48V or 400V.)

            Comment


            • #7
              Cheat the POCO?
              How could someone cheat the POCO when the grid is down?
              The anti Island requirement for a grid tie inverter is to protect linemen down stream from an inverter that could be feeding a grid that the linemen think is dead. As long as there is no connection to the grid, there is nothing illegal about feeding a grid tie inverter a 60 Hertz signal so that the grid tie inverter could power a home from solar panels when the grid is down. The Tesla Powerwall does this and so do the Enphase batteries. These devices include a gateway which is a double pole double throw relay. The gateway operates much like a generator transfer switch. It also has sensors and some logic to control how the system performs. The difficulty is modulating the output of the grid tie inverter to match the load presented to it. This is where batteries play a role. Or a dump load can be used. When the batteries are full the controlling device (Powerwall, hybrid inverter, etc) changes its sync frequency knocking the grid tie inverter offline. My understanding is the Enphase system can turn on an off individual microinverters to match the output of the micro inverters to the load.
              Am I misunderstanding someting here? I did not see the original posters question and may have missinterpreted the comment by SunEagle about spoofing a grid tie inverter.

              Comment


              • #8
                Any system with DC battery over 50 volts, falls into the next higher class of "user protection" with locking cabinets and ways to prevent a person from contacting the high voltage DC, like with watering batteries or some such. Batteries in the middle and end of the bank, will have 60 to 120V energized in the electrolyte during testing, enough to be deadly.
                High voltage DC switching is not easy, and gear is not developed for consumers. Sure, I know there is a Buba somewhere that has a system working, but it's not ready for prime time anytime soon.
                And there's NO SUCH THING AS AC PV PANELS . Remove that from your vocabulary.
                Solar panels are solid state DC devices. You can glue a inverter on to the back of them, and then you have a PV with an inverter.
                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


                • #9
                  Originally posted by Ampster View Post
                  Cheat the POCO?
                  How could someone cheat the POCO when the grid is down?
                  The anti Island requirement for a grid tie inverter is to protect linemen down stream from an inverter that could be feeding a grid that the linemen think is dead.
                  Exactly. And clever schemes to "trick" grid tie inverters into producing often do not have those anti-islanding protections. For example, I once saw someone who advocated:

                  1) Turning off your main breaker
                  2) Plugging in a small inverter/battery to a branch circuit with the infamous "two male end extension cord"
                  3) Starting the inverter and using that signal to "fool" grid tie inverters.

                  Then his wife comes home and turns on the main breaker because she thinks the power is back on and - blam!

                  As long as there is no connection to the grid, there is nothing illegal about feeding a grid tie inverter a 60 Hertz signal so that the grid tie inverter could power a home from solar panels when the grid is down. The Tesla Powerwall does this and so do the Enphase batteries. These devices include a gateway which is a double pole double throw relay. The gateway operates much like a generator transfer switch.
                  Of course. Properly designed, AC coupled systems pose little risk. But SE was referring to "DIY people" who are "taking shortcuts that are dangerous."

                  Comment


                  • #10
                    Originally posted by jflorey2 View Post
                    Exactly. And clever schemes to "trick" grid tie inverters into producing often do not have those anti-islanding protections. For example, I once saw someone who advocated:

                    1) Turning off your main breaker
                    2) Plugging in a small inverter/battery to a branch circuit with the infamous "two male end extension cord"
                    3) Starting the inverter and using that signal to "fool" grid tie inverters.

                    Then his wife comes home and turns on the main breaker because she thinks the power is back on and - blam!
                    1) is ok
                    2) is a huge mistake and will cause problems if there is any load higher than the inverter can handle
                    3) is where the blam happens. Most likely the grid tie inverter will not be fooled, However if it is, then as a grid tie inverter that thinks it is connected to the grid, it will generate as much power as it can. There will be no place for this power to go except to try and back feed the small battery inverter which is neither designed for this nor capable of handling the load.

                    4) wife comes home to find house burned down.

                    Most likely the person advocating this didn't have solar and certainly never tried it.
                    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                    Comment


                    • #11
                      Originally posted by NCmountainsOffgrid View Post
                      Maybe MYTH is the incorrect word, but the question is really one of simplicity
                      and ease-of-build for this type of situation. What I want is:
                      -Solar to be the main 120v output , during peak sun-hours, of course
                      -Battery bank as the secondary, for 'overnight', or otherwise off-peak hours power
                      -Grid power for 240v power needs , during off-peak hours
                      -and the Generator as the 'emergency' power source
                      ...with the optional ability to sell back power during peak hours, if any, of course.
                      MYTH??
                      Most grid tie inverters, even micro inverters produce 240V. It is harder for them to provide 120V, in most cases added equipment is required.
                      You do understand how net metering works? there is no battery required or anything really to get a typical grid tie install to provide the main power during sun hours.
                      if you want a battery bank to provide power during over night then you will need a bimodal system. However if you have net metering there is of course no need for that.

                      Most bimodal system can handle a generator as backup.

                      I am not sure what all the talk of micro inverter systems is about. (AC panels are standard PV modules with micro inverters PRE-installed).
                      a bimodal system using micro-inverters is just much more complex and costly using AC coupling.

                      what you really need to answer is WHY do you want to use micro inverters in your system with the other requirements?
                      and further WHY do you want to have the batteries provide power at night, when the grid is functioning?
                      OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                      Comment


                      • #12
                        thanks for all the feedback to my original idea, great discussion topics
                        What about the idea, for grid-tie shut down of the micro-inverters, to instead
                        have an automatic disconnect, or ATS, at the METER? ... leaving the ability
                        for the solar to continue providing power to the homeowner, in the event of
                        grid power loss.

                        Comment


                        • #13
                          Originally posted by NCmountainsOffgrid View Post
                          thanks for all the feedback to my original idea, great discussion topics
                          What about the idea, for grid-tie shut down of the micro-inverters, to instead
                          have an automatic disconnect, or ATS, at the METER? ... leaving the ability
                          for the solar to continue providing power to the homeowner, in the event of
                          grid power loss.
                          If there is no grid ( you disconnect it) then all grid tie inverters including micro inverters shutdown.
                          They do not have the capability to provide power without the grid.
                          The only way to get power with out the grid from solar is with a bimodal system and most have no need for a transfer switch.

                          Unless you are talking about the fictional IQ8??
                          OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                          Comment


                          • #14
                            also, I come from the RVing world, where 'off-grid' solar, generator, and battery Inverter power options
                            are just part of the everyday life of using your motorhome - and while I can plug into the 'grid',
                            if I lose grid power, my inverter continues providing power to my 'home'... though, the difference
                            is that I'm not then sending that power OUT the shore power cord back to the meter.

                            Comment


                            • #15
                              Originally posted by NCmountainsOffgrid View Post
                              also, I come from the RVing world, where 'off-grid' solar, generator, and battery Inverter power options
                              are just part of the everyday life of using your motorhome - and while I can plug into the 'grid',
                              if I lose grid power, my inverter continues providing power to my 'home'... though, the difference
                              is that I'm not then sending that power OUT the shore power cord back to the meter.
                              Apples and oranges. Your RV inverter is not a grid tie inverter.
                              2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                              Comment

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