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  • #46
    Originally posted by SunEagle View Post

    All good info. A generator is still the best emergency backup power solution in my book.

    I think the OP was looking for a way to utilize their expensive solar pv array when the grid is down. Not being able to use any of it or just a little of it seems to get people pretty hot under the collar.
    This is exactly it for us.
    Obviously being tied to the grid is an important piece of the equation for solar to make sense economically. However the aggravation of not being able to use the system is difficult for customers.We are in Florida where hurricanes are common and outtages are constantly considered. We are currently looking at this as an opportunity to sell them a battery backup but the additional cost can kill some projects and having a way to install systems with some kind of transfer switch would make a ton of sense.

    "Until the rules change the require a full disconnect between a solar pv system and the grid to be installed by all, there will not be any grid tie inverter that works fully without the grid."
    Is this because of an NEC rule?

    I don't understand why there isn't a way to install a manual transfer switch that will allow the system to power back on in the event of an outtage (similar to the way a generator works). How does a battery allow this and keep utility lineman safe?

    I really appreciate the input

    Comment


    • #47
      Originally posted by notJEA View Post

      ............

      "Until the rules change the require a full disconnect between a solar pv system and the grid to be installed by all, there will not be any grid tie inverter that works fully without the grid."
      Is this because of an NEC rule?

      I don't understand why there isn't a way to install a manual transfer switch that will allow the system to power back on in the event of an outtage (similar to the way a generator works). How does a battery allow this and keep utility lineman safe?

      I really appreciate the input
      The rules will not change because they are there to protect the linemen. A hybrid inverter will do all that but they are more expensive than a grid tie inverter.

      There are a number of reasons a grid tie inverter is less expensive than a hybrid inverter. The circuitry is simpler because the grid tie inverter can simply follow the sinewave of the grid.The grid presents an infinite load to the grid tie inverter so it does not need to measure or control the power output. There is no transfer switch in a grid tie inverter. The hybrid inverter has to have circuitry to charge batteries. The circuitry and software is also complex that allows the hybrid inverter to modulate power from the solar panels when the batteries are full and the load is small.

      As to how batteries do that, the only one that I know of is the Tesla Powerwall which does contain and inverter and it is installed with a separate transfer switch and uses a third party device to measure currents and communicate with the inverter and integral battery charger.

      I hope that answers some of your questions. The more I have learned about this issue the more I find there is to learn. It is not as simple as it would seem.
      Last edited by Ampster; 04-29-2019, 03:31 PM.

      Comment


      • #48
        Originally posted by Ampster View Post

        The rules will not change because they are there to protect the linemen. A hybrid inverter will do all that but they are more expensive than a grid tie inverter.

        There are a number of reasons a grid tie inverter is less expensive than a hybrid inverter. The circuitry is simpler because the grid tie inverter can simply follow the sinewave of the grid.The grid presents an infinite load to the grid tie inverter so it does not need to measure or control the power output. There is no transfer switch in a grid tie inverter. The hybrid inverter has to have circuitry to charge batteries. The circuitry and software is also complex that allows the hybrid inverter to modulate power from the solar panels when the batteries are full and the load is small.

        As to how batteries do that, the only one that I know of is the Tesla Powerwall which does contain and inverter and it is installed with a separate transfer switch and uses a third party device to measure currents and communicate with the inverter and integral battery charger.

        I hope that answers some of your questions. The more I have learned about this issue the more I find there is to learn. It is not as simple as it would seem.
        You definitely are helping me understand.

        I wasn't thinking about an inverter with a transfer switch built in.

        I am trying to understand why we cannot install a manual switch that can be physically switch by the home owner in the event of an outtage.
        Similar to the way you can power your home with a generator.

        Comment


        • #49
          Originally posted by notJEA View Post

          You definitely are helping me understand.

          I wasn't thinking about an inverter with a transfer switch built in.

          I am trying to understand why we cannot install a manual switch that can be physically switch by the home owner in the event of an outtage.
          Similar to the way you can power your home with a generator.
          The generator has circuitry that allows it to follow the load, the grid tie inverter does not have that. A generator can simply adjust the power as the load goes up and down.

          A hybrid inverter has the circuitry to follow the load but it also has to control the output of the panels which is more complex than what a generator does.
          NB, subsequently [USER="20178"]ButchDeal[/USER] described that process as throttling.
          Last edited by Ampster; 04-29-2019, 06:13 PM.

          Comment


          • #50
            Originally posted by notJEA View Post

            I am trying to understand why we cannot install a manual switch that can be physically switch by the home owner in the event of an outtage.
            Similar to the way you can power your home with a generator.
            You can. It is just that a grid tie inverter will not do ANYTHING at all if it doesn't see the grid.

            A bimodal inverter will isolated and continue providing power but only what is required for the load.
            Bimodal inverters are capable of throttling where regular grid tie inverters are not.
            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

            Comment


            • #51
              Originally posted by notJEA View Post
              I am trying to understand why we cannot install a manual switch that can be physically switch by the home owner in the event of an outtage.
              Similar to the way you can power your home with a generator.
              The SMA inverter works like that - you throw a switch and it powers an outlet (not the whole house.) The IQ8 system will have something like what you describe but it's not out yet.


              Comment


              • #52
                Originally posted by notJEA View Post

                This is exactly it for us.
                Obviously being tied to the grid is an important piece of the equation for solar to make sense economically. However the aggravation of not being able to use the system is difficult for customers.We are in Florida where hurricanes are common and outtages are constantly considered. We are currently looking at this as an opportunity to sell them a battery backup but the additional cost can kill some projects and having a way to install systems with some kind of transfer switch would make a ton of sense.

                "Until the rules change the require a full disconnect between a solar pv system and the grid to be installed by all, there will not be any grid tie inverter that works fully without the grid."
                Is this because of an NEC rule?

                I don't understand why there isn't a way to install a manual transfer switch that will allow the system to power back on in the event of an outtage (similar to the way a generator works). How does a battery allow this and keep utility lineman safe?

                I really appreciate the input
                As others have stated the NEC rule is to keep people safe. There is also an issue with building an inverter that will "automatically" disconnect from the grid yet keep working at full capacity. To build one that continues to provide the home full power is both expensive and actually not very practical without another "steady" power source to keep the lights from dimming or loads from turning off. That "steady" power source is either a battery system or "the grid". That is why a Hybrid type works with batteries.

                Even though SMA makes an inverter with a "secure" power option the truth is it will only work while the sun is out and is a constant power source. Since the sunlight is a variable (minute to minute) then the output of that "secure" power option is also variable. Imagine if your power kept dipping or spiking. That would kill a lot of appliances.

                So having a solar inverter that can disconnect from the grid and provide full power is a little misleading since the sun is your power source and it does not provide the "constant" needed to keep the loads running efficiently. You still need either a battery or the grid.

                Comment


                • #53
                  Originally posted by SunEagle View Post

                  As others have stated the NEC rule is to keep people safe. There is also an issue with building an inverter that will "automatically" disconnect from the grid yet keep working at full capacity. To build one that continues to provide the home full power is both expensive and actually not very practical without another "steady" power source to keep the lights from dimming or loads from turning off. That "steady" power source is either a battery system or "the grid". That is why a Hybrid type works with batteries.

                  Even though SMA makes an inverter with a "secure" power option the truth is it will only work while the sun is out and is a constant power source. Since the sunlight is a variable (minute to minute) then the output of that "secure" power option is also variable. Imagine if your power kept dipping or spiking. That would kill a lot of appliances.

                  So having a solar inverter that can disconnect from the grid and provide full power is a little misleading since the sun is your power source and it does not provide the "constant" needed to keep the loads running efficiently. You still need either a battery or the grid.
                  Ahh thanks so much.
                  This is starting to make sense.

                  So if we used a Bimodal inverter this could allow for some usage in an outtage situation? [USER="20178"]ButchDeal[/USER]
                  However without the constant power it wouldn't be reliable.

                  Sounds like i might need to wait for the IQ8.
                  But also seems like it would be better than nothing?


                  Thanks again guys
                  Last edited by notJEA; 04-29-2019, 06:30 PM.

                  Comment


                  • #54
                    Originally posted by notJEA View Post

                    So if we used a Bimodal inverter this could allow for some usage in an outtage situation? [USER="20178"]ButchDeal[/USER]
                    However without the constant power it wouldn't be reliable.

                    Sounds like i might need to wait for the IQ8
                    a bimodal inverter has batteries and will be reliable. The IQ8 is just a gimmick lick the SMA (in)secure power
                    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                    Comment


                    • #55
                      Originally posted by notJEA View Post

                      Ahh thanks so much.
                      This is starting to make sense.

                      So if we used a Bimodal inverter this could allow for some usage in an outtage situation? [USER="20178"]ButchDeal[/USER]
                      However without the constant power it wouldn't be reliable.

                      Sounds like i might need to wait for the IQ8.
                      But also seems like it would be better than nothing?


                      Thanks again guys
                      This is Butch's area of expertise so I am only offering possible clarification from my listed experience with two bimodal inverters.
                      The constant power that Butch was referring to was batteries or the grid. When the grid is down you are relying on the batteries. The sun is only an intermittent source of power. The IQ8 would also be intermittent unless Enphase has a battery system designed to work with the IQ8.

                      Comment


                      • #56
                        Originally posted by notJEA View Post
                        So if we used a Bimodal inverter this could allow for some usage in an outtage situation?
                        A bimodal (hybrid) inverter plus battery does indeed allow a lot of usage during an outage. But you need the battery and it's a lot more expensive. Examples are the Outback Radian and the Schneider Conext line.
                        However without the constant power it wouldn't be reliable.
                        Right. Power only when the sun is out. If constant power is a requirement for your application you could get a $99 UPS from Best Buy and use that - but we're talking constant power for things like lights, not refrigeration.
                        Sounds like i might need to wait for the IQ8.
                        But also seems like it would be better than nothing?
                        If you want backup power without batteries right now your only choice is SMA.

                        Enphase IQ8 isn't released yet, and I wouldn't get the first release anyway; first releases are always buggy. But Enphase has a good track record and they also have small AC batteries you can add to your installation to allow you to power loads constantly, so there's an upgrade path later for customers.

                        Outback Skybox will not provide any power during a blackout without a battery, but you can add a battery later.

                        Comment


                        • #57
                          Originally posted by jflorey2 View Post
                          A bimodal (hybrid) inverter plus battery does indeed allow a lot of usage during an outage. But you need the battery and it's a lot more expensive. Examples are the Outback Radian and the Schneider Conext line.

                          Right. Power only when the sun is out. If constant power is a requirement for your application you could get a $99 UPS from Best Buy and use that - but we're talking constant power for things like lights, not refrigeration.

                          If you want backup power without batteries right now your only choice is SMA.

                          Enphase IQ8 isn't released yet, and I wouldn't get the first release anyway; first releases are always buggy. But Enphase has a good track record and they also have small AC batteries you can add to your installation to allow you to power loads constantly, so there's an upgrade path later for customers.

                          Outback Skybox will not provide any power during a blackout without a battery, but you can add a battery later.
                          Ahhh I think i understand now.

                          We are planning on using Enphase IQ7 micro inverters. If we swap these for bimodal inverters and use a cheap battery it sounds like we could potentially allow our customers to keep the lights on and charge phones? Thinking we could offer this as a slight upgrade over the standard system for a small price increase. Might just be easier to sell a full battery system...

                          Without a battery to supply "constant" power in an outtage etc. what would happen if you tried to use the system?
                          Would the lights/AC, refrigerator flicker on and off?

                          Comment


                          • #58
                            Originally posted by notJEA View Post

                            Ahhh I think i understand now.

                            We are planning on using Enphase IQ7 micro inverters. If we swap these for bimodal inverters and use a cheap battery it sounds like we could potentially allow our customers to keep the lights on and charge phones? Thinking we could offer this as a slight upgrade over the standard system for a small price increase. Might just be easier to sell a full battery system...

                            Without a battery to supply "constant" power in an outtage etc. what would happen if you tried to use the system?
                            Would the lights/AC, refrigerator flicker on and off?
                            Without a battery system or the grid, solar pv output can and will fluctuate based on the intensity of the sunlight and clouds passing over head. The fluctuating output will cause lighting to dim and possibly damage motors on appliances like a refrigerator or AC unit.

                            Comment


                            • #59
                              Originally posted by notJEA View Post
                              We are planning on using Enphase IQ7 micro inverters. If we swap these for bimodal inverters and use a cheap battery it sounds like we could potentially allow our customers to keep the lights on and charge phones? Thinking we could offer this as a slight upgrade over the standard system for a small price increase. Might just be easier to sell a full battery system...
                              It is very unlikely that 1) you will be able to do a "cheap battery" or that 2) it will be a small price increase. The closest thing to that is probably the Skybox, which you can add a battery to later. Your battery choices will devolve to a cheaper lead acid battery (but then you need the right container, they are heavy and short lived etc) or an expensive integrated battery like the SimpliPhi (simple, sexy, long lived - but pricey.)

                              Note that even with a Skybox you will not get any backup power unless you install a "critical loads" subpanel. The inverter cannot backfeed the main panel when power is out, so critical circuits (lights and outlets usually) have to be moved to a subpanel that the inverter powers up. That is often a significant cost. You can also use a cheap transfer switch (you can get them at Home Depot) but that's not good practice.
                              Without a battery to supply "constant" power in an outtage etc. what would happen if you tried to use the system? Would the lights/AC, refrigerator flicker on and off?
                              With a conventional string inverter, or regular IQ7's, it won't work, period. No flickering because no power.

                              With something like the SMA Secure Power output, the output will be good until the solar output drops below the demand, at which point it will shut off instantly. No flickering/dimming.
                              Last edited by jflorey2; 05-01-2019, 05:42 PM.

                              Comment


                              • #60
                                Originally posted by quiet_rider View Post
                                Don't try to trick it to be on. Waste of money & won't match load cycle (cloudy, night).
                                Why not buy or lease an electric car (EV, PHEV) which would be charged with your system? Connect a 12VDC inverter (car type, 1500W or RV camper type, 5000W) & run extension cords to appliances or use manual interlock to power house (same as with Generac). Plenty of deals on used cars too.
                                Drive car to charging station (Chargepoint) if needed. You can even find free stations. Back to house for a few hours or days of power.
                                Theoretically you could replace a gas car with electric & have net savings or short term breakeven.
                                Who wins a prize for a solution you choose? Interested to hear update...
                                This is pretty clever.
                                Might have to start an electric vehicle leasing company for emergency services here in FL.
                                For all grid tied solar owners without a battery ha.

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