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Design of Grid Tied Systew with Off-Grid Option?

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  • #31
    The easy way to create a grid-tie system by day, and off-grid at night.

    For what it's worth you can create a fairly simple interactive grid system (Solar panels power the house via the grid by day, and use batteries by night) by using an outback GVFX inverter. Just use the Grid-tie side of the inverter exclusively. And just use the dedicated inverter output for critical loads such as Refrigerators etc. You will have to set the AC1/Grid AAC setting way down, because the inverter tends to try to pour everything it can into the grid which is great if your just trying to spin the meter backwards. But not great at night as this will kill your battery as it has no way to measure your actual grid-side load. Setting the AC1/Grid value down will just let it pour enough into the grid to keep the meter idling and allow you to run through the night. And it's not all that expensive to put in a battery bank if you do it yourself. Just take care of them and if you don't deep cycle them all the time they will last a long time.

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    • #32
      Originally posted by Shockah View Post
      You'll need to determine the watt hours consumed by the "one computer, a couple cell phones, recharging flashlight batteries, and the pump for the rainwater harvest system."
      Use this handy off-grid calculator to determine how much panel you'll need to dedicate and battery size.

      For my "NATURAL DISASTER" plan, I would need about 3kwh per day... which means dedicating 6 panels and purchasing a 1250ah/12v battery pack, along with the CC and Inverter.
      Quite an expensive survival kit... which is why I have only pondered it so far ...
      What is the figure you estimate for your expensive survival kit?

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      • #33
        Originally posted by paulcheung View Post
        What is the figure you estimate for your expensive survival kit?
        Considering panels are being provided by an existing grid-tie system,
        Off the top of my head, I'd say $4000 might cover the 1250ah 12v (or 625ah 24v) battery, mppt controller, psw inverter, switches and hardware needed for a 3kwh system.

        A lot to pay just to keep the ice cream from melting...
        but PV back-up is the best choice (IMHO) if grid is down longer than 2 weeks due to an act of god.
        [CENTER]SunLight @ Night[/CENTER]

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        • #34
          Originally posted by FS2020 View Post
          In any case, I was asking for advice about the design and components to use. I make no claims to be experienced with this kind of design, that's why I asked. I'll follow up your advice to look into Outback hybrid systems. But I was hoping to use microinverters at the panels to avoid long runs of heavy DC cables, for safety reasons.
          Frank, MSME, and 28 years at DOE.
          Can't use microinverters. They are grid tied only and per your diagram, once the batteries are discharged you're in the dark. They would not charge your batteries when the grid is down. Outback XW and similar hybrid inverters are the way you'd have to go.

          WWW

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          • #35
            Originally posted by SunWorldGreenEnrgy View Post
            For what it's worth you can create a fairly simple interactive grid system (Solar panels power the house via the grid by day, and use batteries by night) by using an outback GVFX inverter. Just use the Grid-tie side of the inverter exclusively. And just use the dedicated inverter output for critical loads such as Refrigerators etc. You will have to set the AC1/Grid AAC setting way down, because the inverter tends to try to pour everything it can into the grid which is great if your just trying to spin the meter backwards. But not great at night as this will kill your battery as it has no way to measure your actual grid-side load. Setting the AC1/Grid value down will just let it pour enough into the grid to keep the meter idling and allow you to run through the night. And it's not all that expensive to put in a battery bank if you do it yourself. Just take care of them and if you don't deep cycle them all the time they will last a long time.
            That is total green BS and blather - a very stupid way to do things!
            [SIGPIC][/SIGPIC]

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            • #36
              Originally posted by Sunking View Post
              It is a whole house genny. In summer when th ebig t-storms and twisters roll through and knock out power, I set back in my air conditioned house and watch everyone suffer in 100 degree heat without power. I cycle the generator with the HVAC only coming on when the HVAC switches on to conserve fuel. With Sun Tubes and bay windows provides all the light I need during the day.
              And when your neighbors, who hear your 12 kW generator, and need electricity for their medical devices or whatever to survive, show up at your door with a shotgun and tell you they are going to take what they need to survive, what is your plan?

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              • #37
                Originally posted by FS2020 View Post
                And when your neighbors, who hear your 12 kW generator, and need electricity for their medical devices or whatever to survive, show up at your door with a shotgun and tell you they are going to take what they need to survive, what is your plan?
                Well for one the gernny is just outside my bedroom window and cannot be heard when running. The outside AC unit is louder than the genny. But I would shoot back with one of my many guns. In this case a Browning BAR. I don't buy into the whole SHTF scenerio. I am Christian and my belief is the Lord will take me home when that happens and leave you here in Hell On Earth to do the suffering and fight the finale battle.
                MSEE, PE

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                • #38
                  Originally posted by Sunking View Post
                  Well for one the gernny is just outside my bedroom window and cannot be heard when running. The outside AC unit is louder than the genny. But I would shoot back with one of my many guns. In this case a Browning BAR. I don't buy into the whole SHTF scenerio. I am Christian and my belief is the Lord will take me home when that happens and leave you here in Hell On Earth to do the suffering and fight the finale battle.
                  Maybe you are right. I didn't know that there are 12kW genny's that are so silent. What's the make and model? Maybe I should take your advice and get a big generator, and stock up on guns. What make and model of guns do you recommend?

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                  • #39
                    Originally posted by Shockah View Post
                    Considering panels are being provided by an existing grid-tie system,
                    Off the top of my head, I'd say $4000 might cover the 1250ah 12v (or 625ah 24v) battery, mppt controller, psw inverter, switches and hardware needed for a 3kwh system.

                    A lot to pay just to keep the ice cream from melting...
                    but PV back-up is the best choice (IMHO) if grid is down longer than 2 weeks due to an act of god.
                    Since the panel is there already, you don't need so much money for that 3kwh system, The Outback FM 60 about $550, Inverter 1000watts about $300 to 500. 4 rolls s530 6 volts 400 amps batteries @350each =1400. you only need 4 250watts panels to do that. it is $2450 so far. what you can do is wire this circuit different from the main house panel and get a 30 amps auto transfer switch to switch back to the main system when batteries get too low in case rainy days. you can use the system daily as the main system.

                    I have a similar small system about 2kwh per day. I use 3 235 watts panel and 4 6 volts 225 amps batteries and it work wonderfully.

                    Cheers.

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                    • #40
                      Originally posted by FS2020 View Post
                      Maybe you are right. I didn't know that there are 12kW genny's that are so silent. What's the make and model? Maybe I should take your advice and get a big generator, and stock up on guns. What make and model of guns do you recommend?
                      I use a Kohler pad mounted whole house generator. Cannot tell you what size works for you because there are many variables. But you can click here to Kohler Generator Selector tool that will walk you through the steps to find the right unit for you based on your specific needs.

                      A pad mounted generator is bolted down on a concrete pad, same as a 500 gallon LP tank if you do not have natural gas. Not something people just pick up and walk away with without a crane to lift it up and place on a flatbed truck.

                      As for guns, well I collect WW-II weapons, and have a few hunting weapons. But if I could only have one for home defense nothing beats a good ole fashion short barrel 10 or 12 gauge pump shot gun loaded with buckshot. They even make 12 gauge pumps just for home protection. Or use any military or police riot pump shot guns. Lots of options and you do not have to be a good shot. Just point at center mass and shoot. Kind of messy though at close range.
                      MSEE, PE

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                      • #41
                        Originally posted by Sunking View Post
                        for home defense nothing beats a good ole fashion short barrel 10 or 12 gauge pump shot gun
                        I always preferred a 20 gauge - easy to use one handed.

                        Surprising how people insist on generators being noisy.
                        [SIGPIC][/SIGPIC]

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                        • #42
                          Originally posted by russ View Post
                          Surprising how people insist on generators being noisy.
                          Non professionals and ignorance get folks trapped in a box. Joe Blow homeowner thinks a generator is a noisy 2 Kwh unit with a Briggs engine burning gasoline they buy at Agent Orange of Big Blue. They have no idea there are pad mounted LPG quite whole house gennys out there. Same thing with batteries they think they are 12 volts you put in a car.

                          I do a lot of work with ATT, Verizon Wireless, Sprint and other cellular telephone companies. As most know that live in any city the cell sites are right in the middle of a residential neighborhood, and just about all of them have Emergency Generators. They are not small by any means as they are 40 to 60 Kva and use either LPG, diesel fuel or NG if available. They run at least once every week for 20 to 30 minutes on a specific day and time from the exercise cycle. Neighbors only complain about the noise on outside units when an alarm goes off in the generator. They all use that dang annoying sonalert high pitched tone. Even a 60 Kw diesel genny is whisper quite when running and a 60 Kw genny is enough to run several homes. The only theft problem is copper thieves.
                          MSEE, PE

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                          • #43
                            Originally posted by paulcheung View Post
                            Since the panel is there already, you don't need so much money for that 3kwh system, The Outback FM 60 about $550, Inverter 1000watts about $300 to 500. 4 rolls s530 6 volts 400 amps batteries @350each =1400. you only need 4 250watts panels to do that. it is $2450 so far. what you can do is wire this circuit different from the main house panel and get a 30 amps auto transfer switch to switch back to the main system when batteries get too low in case rainy days. you can use the system daily as the main system.

                            I have a similar small system about 2kwh per day. I use 3 235 watts panel and 4 6 volts 225 amps batteries and it work wonderfully.

                            Cheers.
                            Nice... thanks for sharing similar systems out there.
                            $2450 is a bit shy considering the shipping cost of batteries to Hawaii. You also did not tally the switches and incidentals... but we're on the same page...

                            I figured 6 panels because this kit would be needed during hurricane destruction which is normally followed by cloudy weather.

                            This is not for a SHTF scenario, for I don't think the world is going to come to an end that easily or in my lifetime.
                            Super Storm Sandy & Hurricane Haiyan in the Philippines inspired me to think about this (more). For we are a small mass here and would suffer long term if we were to experience either... and like Fukushima Japan, our main power plant (fuel, not nuclear) is right on the ocean front.

                            We had our wake up calls in 1982 & 1992,,, I learned a thing or 2 about survival back then
                            [CENTER]SunLight @ Night[/CENTER]

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                            • #44
                              The fellow is history
                              [SIGPIC][/SIGPIC]

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                              • #45
                                Originally posted by Shockah View Post
                                We had our wake up calls in 1982 & 1992,,, I learned a thing or 2 about survival back then
                                No offense is being offered, but when you choose to live on an island or coast, you do so knowing the risk that you will be wiped off at some point in time. What is really ironic is you pay a premium in real-estate prices doing so.

                                Think about the folks in NOLA. They have the worlds biggest Hurricane Bulls Eye on their back and below sea level. Yet for some reason people choose to live there knowing they will be wiped out sooner rather than later. You pays your money and take your chances. No guarantees in life, just a chance is all you get.
                                MSEE, PE

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