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Can you offer some advice on refrigeration?

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  • #16
    Perfect. Thanks again. I'll report back with how it turns out.

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    • #17
      OK I am missing something with the answers being given. My understanding is the OP want 1300 wh/day, and basically the system is a full time system with the OP occupying th premises 2 weeks at a time. Quite doable, but I am having trouble with the answers. Right off the bat Battery size is:

      12 volts @ 540 AH
      24 volts @ 270 AH
      48 volts @ 135 AH

      Minimum required panel wattage regardless of battery voltage is 700 watts.

      Given 700 watts minimum you can eliminate a 12 volt system simply because the Charge Controller would need to be 60 Amps, and that cost some big $$$. At 24 volts you are looking at a 30 amp controller, but I would advise at least a 45 amp controller as that will allow the OP to grow up to 1200 watts @ 24 volt battery or 2400 watts @ 48 volt battery. Take your pick.

      Lastly I woul dnot advise the OP to use a Parallel Battery Configuration. You can buy 6-Volt batteries up to 435 AH. There is no reason to be stuck with 225 AH unless you want a 48 volt 225 AH system.
      MSEE, PE

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      • #18
        FYI, for novices like me, on Renvu's website, under "Plan and Design", "Solar Kit Guide" they have an outstanding wizard that will step you through both Grid-Tied and Off-Grid setups. The tools are pretty thorough and you can have them email you a quote at the end. I ran several such Grid-tied comparisons (various panels, Micro vs Optimizers) to compare to the installer quotes I was getting (to get a feel for the cost of labor).

        I just ran a quick "Off-Grid" scenario and it stepped me through calculating how many kWh a small fridge would use, sizing the batteries, charge controller, panels, inverter, racking, etc. Still waiting for the quote via email.

        -Jonathan

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        • #19
          I think you did miss something but went back and forth so much that it would be easy. I'm using 4, 6v batteries all in series to get to 24v at 230AH. At 50% dod, that's 2760 watt hours. I'm using my existing 30 amp mppt controller that will allow me to run 1000 watts of panels. It will limit it's output to 30 amps, but with an oversized array it will provide that 30 amps for a longer period of time. Say I get 5 hours of 30 amps of charge, thats 3600 watt hours. There is no paralleling of batteries. There is a series-parallel config of the 4 panels though.

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          • #20
            Originally posted by Basketcase View Post
            Since panels are so cheap, I feel like I can keep my battery bank smaller because it will be charging longer throughout the day, and even on bad days I should have plenty of charging. I'm trying to make it idiot proof so when I'm not there and there are people using the house, it will just work.
            On "bad days" your PV solar power may drop to 10%; even less if covered with snow. More "cheap panels" can
            be used to raise that, and the same panels can lengthen your solar day with multiple orientations. Bruce Roe

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            • #21
              When you purchase your load of groceries for the 2 week visit, get a chunk of dry ice, it will help cool down the fridge the first day
              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

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              • #22
                Originally posted by bcroe View Post

                On "bad days" your PV solar power may drop to 10%; even less if covered with snow. More "cheap panels" can
                be used to raise that, and the same panels can lengthen your solar day with multiple orientations. Bruce Roe
                The house is only used in summer so no snow to worry about. If the charge drops to 10% for too long that could be problematic though. Is that likely in July? I have a perfectly pitched, directly south facing roof for my panels that has no obstructions such as trees.

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                • #23
                  Originally posted by Mike90250 View Post
                  When you purchase your load of groceries for the 2 week visit, get a chunk of dry ice, it will help cool down the fridge the first day
                  That's actually a pretty good idea. I may try that.

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                  • #24
                    Originally posted by Mike90250 View Post
                    When you purchase your load of groceries for the 2 week visit, get a chunk of dry ice, it will help cool down the fridge the first day
                    And for all treehuggers, mostly carbon neutral too.

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                    • #25
                      Originally posted by J.P.M. View Post
                      And for all treehuggers, mostly carbon neutral too.
                      Don't forget to use gloves. That stuff is cold.

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                      • #26
                        Originally posted by SunEagle View Post

                        Don't forget to use gloves. That stuff is cold.
                        ~ -110 F. or so, FWIW. And on a serious note: Handle only in well ventilated areas.

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                        • #27
                          And dispose of "extra" dry ice in a 2 liter bottle

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                          • #28
                            Originally posted by Basketcase View Post
                            And dispose of "extra" dry ice in a 2 liter bottle
                            And don't be around when the ice melts and the container fails catastrophically.

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                            • #29
                              Originally posted by J.P.M. View Post

                              And don't be around when the ice melts and the container fails catastrophically.
                              Exactly. I used to work at a restaurant and we'd get meat packed in dry ice. We used to put the dry ice in the big olive containers (plastic). It was fantastic. Of course this was when you could do stuff like that without getting put on a list.

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                              • #30
                                Catch 22, you either get more cost and less selection with DC refrigerators or good price and great selection with Ac units but must run an inverter, the inverter will be the weak link and the new problem that you grow to hate with your plan, if you get a decent $500 to $800 dollar quality inverter then you wont have too many problems, but i have not seen too many sub $400 units that are going to be happy about cycling that fridge surge 10-20 times a day and hold up for very long, I like your plan on panels, batts, etc. just make sure you really check out inverters well and don't be overly optimistic about that side of things and then i think you will be okay. Everything else in the system may last many, many years but i would not expect the inverter to unless you spend the extra money for a premium heavy duty one, the startup surge on ac fridges is very significant and many times a day over weeks, months, years can take its toll.

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