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  • #31
    Originally posted by SolarDave21 View Post
    I am looking to do the same. In the event of a long black out I do not want to rely on gas powered generators. I want to utilize my solar panels power. There should be a way to switch your panels into a different setting that disconnects power into your main panel bypassing the inverter and swithcing your system into a local powered system with its own off grid inverter. This can be done using switches and once the power comes back in the neighborhood the homeowner should be able to switch the system back into its original state feeding back into the main panel.

    Does anyone have any ideas?
    There are no technical reasons not to do what you suggest, but the cost of the batteries, etc to provide the off grid capability will be high.
    You may want to simplify the switching and configuration requirements by going to a hybrid system which combines the off-grid capability with grid tied operation when POCO is up.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #32
      What hybrid system do you know of? Is it the inverter that I need to buy as a hybrid?

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      • #33
        Originally posted by SolarDave21 View Post
        What hybrid system do you know of? Is it the inverter that I need to buy as a hybrid?
        The hybrid system is what I mentioned to you in your first post. Sunnyboy makes those type of inverters but again it will provide you only a small fraction of power from your panels.

        You have been posting in multiple places asking the same questions and while Sunking and I have tried to explain that you will never be able to use your entire solar panel system as an emergency power source if the grid goes down. It can't be done.

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        • #34
          Originally posted by SunEagle View Post
          The hybrid system is what I mentioned to you in your first post. Sunnyboy makes those type of inverters but again it will provide you only a small fraction of power from your panels.

          You have been posting in multiple places asking the same questions and while Sunking and I have tried to explain that you will never be able to use your entire solar panel system as an emergency power source if the grid goes down. It can't be done.
          I've not followed what all this person is trying to do, and where all they are posting, but there are strategies (other than a Sunny Island ...) that will work. Apollo at one time had a high voltage DCPV charge controller. I don't know what happened to it, but one of those on a traditional DCPV setup, with an array output transfer switch would seem to do the trick -- feed the high voltage array to either a string inverter (grid-up-mode) or the Apollo (grid-down-mode). Something like an OutBack Radian keeping a large bank of Gel (lowest maintenance requirements, longest life) periodically floated would then provide the backup power.

          The real problem is that people get themselves into PV systems without thinking through all the costs or making sure they are getting what they =need=, and not just what the installer wanted to sell. Then there is hype, and SMA's new "backup power outlet" that doesn't work at night and won't run a toaster oven falls into the category of "hype" ...
          Julie in Texas

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          • #35
            Instead of using new and expensive deep cycle batteries, would it work to use old car batteries? They may not hold a charge for long, and therefore might not be good for nighttime operation, but could they at least act as a regulator, and absorb excess production?

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            • #36
              Originally posted by DavidT View Post
              Instead of using new and expensive deep cycle batteries, would it work to use old car batteries? They may not hold a charge for long, and therefore might not be good for nighttime operation, but could they at least act as a regulator, and absorb excess production?
              Car batteries were not designed for deep discharge. They may work for a couple of months but then start to fail and not hold a charge. Going cheap on any Off Grid Battery system usually spends your money faster.

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              • #37
                Originally posted by greenHouse View Post
                I've not followed what all this person is trying to do, and where all they are posting, but there are strategies (other than a Sunny Island ...) that will work. Apollo at one time had a high voltage DCPV charge controller. I don't know what happened to it, but one of those on a traditional DCPV setup, with an array output transfer switch would seem to do the trick -- feed the high voltage array to either a string inverter (grid-up-mode) or the Apollo (grid-down-mode). Something like an OutBack Radian keeping a large bank of Gel (lowest maintenance requirements, longest life) periodically floated would then provide the backup power.

                The real problem is that people get themselves into PV systems without thinking through all the costs or making sure they are getting what they =need=, and not just what the installer wanted to sell. Then there is hype, and SMA's new "backup power outlet" that doesn't work at night and won't run a toaster oven falls into the category of "hype" ...
                The person wanted to get 100% output from his solar panels if the grid went down in case the Utility power outage lasted a long time. I tried to explain a grid tie system won't let him do that but a hybrid would allow him to get a small percentage generated from his panels. Going with a battery off grid system would cost him thousands of dollars and is not going really GREEN due to the generation of carbon to make the batteries. I suggested he use a generator but the idea of using fossil fuels was not what he wanted. He asked pretty much the same question in multiple posts and will get the same answer whether he believes it or not.

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                • #38
                  Originally posted by SunEagle View Post
                  The person wanted to get 100% output from his solar panels if the grid went down in case the Utility power outage lasted a long time. I tried to explain a grid tie system won't let him do that but a hybrid would allow him to get a small percentage generated from his panels. Going with a battery off grid system would cost him thousands of dollars and is not going really GREEN due to the generation of carbon to make the batteries. I suggested he use a generator but the idea of using fossil fuels was not what he wanted. He asked pretty much the same question in multiple posts and will get the same answer whether he believes it or not.
                  I think that part of the confusion was between
                  1. making use of all of the power from his panels (which a hybrid with batteries will do but the SMA emergency power will not) and
                  2. getting from the panels all of the power that he needs (never happening without batteries and good insolation.)
                  SunnyBoy 3000 US, 18 BP Solar 175B panels.

                  Comment


                  • #39
                    Originally posted by inetdog View Post
                    I think that part of the confusion was between
                    1. making use of all of the power from his panels (which a hybrid with batteries will do but the SMA emergency power will not) and
                    2. getting from the panels all of the power that he needs (never happening without batteries and good insolation.)
                    He was also dead set on not using a fossil fuel generator which is an important part of any off grid or hybrid system.

                    Again I think he was led to believe that going Solar was GREEN and that a grid tie system would somehow work even if the grid went down.

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                    • #40
                      The Xantrex / Schenider XW series and maybe the conext series are hybrid and can draw from the grid, or feed it.
                      BUT the inverter will need to have 100ah of good batteries for ripple control, for each Kw of export power, so you can't cheap out on the batteries. In the end, the expense of maintaining the large battery bank, wipes out any savings on your electric bill.


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


                      • #41
                        Originally posted by Mike90250 View Post
                        The Xantrex / Schenider XW series and maybe the conext series are hybrid and can draw from the grid, or feed it.
                        BUT the inverter will need to have 100ah of good batteries for ripple control, for each Kw of export power, so you can't cheap out on the batteries. In the end, the expense of maintaining the large battery bank, wipes out any savings on your electric bill.


                        solar:http://tinyurl.com/LMR-Solar
                        Thanks Mike.
                        It is refreshing to get some concrete numbers to work with instead of just general pronouncements.
                        Do you know of any experiments on what effect that kind of ripple-control microcycling has on the batteries?
                        SunnyBoy 3000 US, 18 BP Solar 175B panels.

                        Comment


                        • #42
                          Originally posted by inetdog View Post
                          Thanks Mike.
                          It is refreshing to get some concrete numbers to work with instead of just general pronouncements.
                          Do you know of any experiments on what effect that kind of ripple-control microcycling has on the batteries?
                          I'm assuming "they" have been doing this longer than I, and it's effect on the batteries is minimal.
                          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


                          • #43
                            Originally posted by Mike90250 View Post
                            I'm assuming "they" have been doing this longer than I, and it's effect on the batteries is minimal.
                            The same strategy works with any of the battery-backed inverters, not just Xantrax.

                            The key risk is sulfation over time. Plate shedding is more common with hard and heavy cycling. Float duty batteries tend to have less of that going on, but can gradually sulfate over time. Starved electrolyte batteries, such as AGM and Gel, are less prone to sulfation and have far lower maintenance requirements, but mostly because you can't. If I were designing a system for float-duty (infrequent power outage emergencies only), I'd go with a bank of AGMs in as environmentally controlled a space as I could manage.

                            The biggest "cost" in such a system is efficiency loss. The most efficient battery-backed system I ever worked on was 81% end-to-end. Mid 70's is more common -- mine ranges between 72 and 77 percent, because I have a large-ish bank of FLAs. Efficiency losses are great enough that I'm likely going to reduce the size of my DCPV array and add ACPV capacity. Not only is ACPV easier to expand that string inverters, it's also shade-tolerant, typically in the mid 90's for efficiency, and the panels and microinverters are matched so there's less risk of "too much panel, too little microinverter" or "too little panel, wrong spot on the MPPT curve."

                            On the subject of "cheap batteries", myself and others have found that cheap batteries really aren't all that bad in lighter, suburban duty. I'd love me some S-600s, but I can get better bang-for-my-buck from something in a generic FLA traction battery.
                            Julie in Texas

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                            • #44
                              Originally posted by greenHouse View Post
                              The key risk is sulfation over time. Plate shedding is more common with hard and heavy cycling. Float duty batteries tend to have less of that going on, but can gradually sulfate over time. Starved electrolyte batteries, such as AGM and Gel, are less prone to sulfation and have far lower maintenance requirements, but mostly because you can't. If I were designing a system for float-duty (infrequent power outage emergencies only), I'd go with a bank of AGMs in as environmentally controlled a space as I could manage.
                              Not sure I agree with all of that. Sulfation is a real concern. I agree if you are deeply discharging batteries below 70% capacity the sulfation and shedding of plate is accelerated. It happens with FLA Gel, and AGM. With FLA it is measurable. What I do agree with you if the batteries are going to be used for Float Service Emergency Power, AGM is the good route to go, but for different reasons than you suggested. I would never use a Gel battery for anything other than Fire Alarm Panels or Emergency Egress Lighting.

                              With that said if a battery is used in everyday Cycle Service (20 to 30% DOD daily) like an Off-Grid application, then there is no better bang for the buck than a good quality FLA battery. Even a mid grade FLA will outlive (cycle life) any high end AGM (like Concord) or Gel for that matter. AGM has its place but really is a Nich Application Product to justify the added cost per $/Kwh capacity.

                              Originally posted by greenHouse View Post
                              The biggest "cost" in such a system is efficiency loss. The most efficient battery-backed system I ever worked on was 81% end-to-end. Mid 70's is more common -- mine ranges between 72 and 77 percent, because I have a large-ish bank of FLAs.
                              How are you figuring that? If you use AGM's you can get efficiency up into the 80% range because AGM charge efficiency is in the 95% range, vs FLA in the low 80's. You would also have to use MPPT controllers and keep line losses to 2% or less from panels to input of inveter. Once you take all the losses from input end at the panels to the utilization device hanging out on the end of the inverter wiring more like 66 to 68% best case. If someone is ignorant enough to use PWM controllers 50% is best case. But I do agree efficiency is a real down and why Off-Grid should never be used unless there is no other options.

                              What I really have a problem with is the foolishness of Hybrid Systems. I refuse to give advice to anyone or take on such a job as it is unethical IMO. If you have commercial power, and demand emergency power, then the right answer is a conventional grid tied system with a Whole House Generator using either NG or LPG as the fuel source. Using a hybid battery system is just plain foolish IMO. It still requires a generator on top of very expensive batteries which are not used and a much more expensive inverter, higher installation cost, and very limited amount of power. Why on earth folks do that is beyond me especially if the live in Air Conditioning country. When there is an extended outage I could careless about lights and keeping my milk cold, I want my Air Conditioner and everything on in the house like nothing ever happened. Only way you can do that is with a Whole House Generator and I can have it for 1/2 the cost of those that go hybrid and have to suffer with limited power. That is just nucking futz. So when someone demands it, I refuse the work and send them to someone else who will take their money and waste it.
                              MSEE, PE

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                              • #45
                                Originally posted by Sunking View Post
                                If you use AGM's you can get efficiency up into the 80% range because AGM charge efficiency is in the 95% range, vs FLA in the low 80's.
                                I did not realize it was that extreme!
                                How much of that is directly due to the oxygen-hydrogen recombination and how much to other construction features including starved electrolyte?
                                ( I have a copy of the Battery Bible, but have not waded through it yet.)
                                SunnyBoy 3000 US, 18 BP Solar 175B panels.

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