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Minimal Solar for Storage Barn

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  • Minimal Solar for Storage Barn

    Wife is pushing (and I'm very curious anyways) for solar for my storage barn, a 40x40x10 that I'm using for storage. It's new construction this year and doesn't have any electric currently. It's about 300' from the house so running power would be a bit of a project. My loads would be minimal. I'm looking to power the following:

    Garage door opener - The one I have doesn't have battery backup so to use it would probably require a hefty inverter that would have a lot of parasitic draw so I'm guessing it would be much easier to replace it with one with a battery backup. Or from reading is the parasitic now low enough that it's not an issue to keep the inverter live all the time? The rating plate on the opener is 6A but I'm pretty sure that's peak draw. It would be used most of the time only 2x per day.

    Trickle chargers for 10 cars. I don't anticipate having to charge anything, mainly it's just to keep the parasitic draws from running batteries dead. From the research I've done I'm anticipating the float function would be sufficient and would probably only need to be on a few hours a day.

    Lighting - I have translucent panels on the east wall so it's all I need in the daytime but nights get long in the winter. I don't anticipate working, more along the lines of being able to have the lights on for 10 minutes to check things or grab parts off of the shelving I have.

    Air compressor - Mainly to be able to pump up tires. With my minimal usage I'm probably going to be generating excess energy so I thought it would be nice to have a 50 gallon compressor with a 12v compressor to fill it. As I doubt I would use it very often if it took it a week in the summer or several weeks in the winter I would be fine with that. I would configure things to run this only when I'm generating enough power to run it from the solar.

    I realize it would probably be cheaper to run electric out but I want to learn how to make it work. I'm guessing a couple of panels mounted on the roof, an MPPT controller and probably a battery for the lighting. I'm an electrical engineer but know enough to know that probably makes me more dangerous. I did most of the wiring in my shop by myself and have a local contractor who has been very helpful when I need it.

    Any comments or suggestions? Specific equipment or methods to control the loads?

  • #2
    I'd say if you want to learn about solar, buy some panels, a charge controller, a few T105 batteries and an inverter. They can all be had for fairly cheap and you can get a sense of how solar works from all that. You can run basic loads on it. It might be a nice (but unreliable) backup for outages and whatnot.

    If you want power to your barn, run a new line to the barn.

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    • #3
      The compressor - to fill a 50 gal tank, you will need a larger compressor, a small 12V model will likely burn out before the tank is full.

      10 cars on chargers ! Wow. That may be your deciding factor there. All seasons or winter only ? How will you manage this, 1 charger and carrying it to each car, or do you have a central station to select a vehicle from ?
      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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      • #4
        Part of the reasoning for getting the 12v compressor from an air suspension is that it should be much more durable than what is normally sold. As it is I'm guessing a single tire has a capacity of more than 5 gallons as I have never managed to inflate a tire with less than 3 trips with my 5 gallon tank unless they are only a little low. I've had to inflate all 4 tires on my car at work with a 12v compressor and the $30 HF freight one has done it multiple times so I'm hoping one from a car is even more durable.

        The cars aren't being charged, they're being floated. They have lived for years with HF trickle chargers on them that are rated at 1/2 amp, so they are only pulling max 6w each.

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        • #5
          Originally posted by teal95 View Post
          It's about 300' from the house so running power would be a bit of a project.
          300' is quite doable for running power.
          A voltage drop calculator tells me you could run 2/0 aluminum.
          I used:
          300' cable length,
          60A (a large subpanel for what you're looking for - but probably as small as I'd want to install)

          $0 for the "call before you dig" people to come out and mark everything before you dig.
          ~$1000 for ditch-witch rental
          ~$900 for wire
          ~$200 for breakers and other misc. things.

          So my guesstimate is around $2k, and 2-3 weekends of work.
          I think it's a reasonable to do project - probably less than an off-grid solar system with 2 sets of batteries. And IMO more useful.
          So I'd take that route.

          Another option is pay someone to come in and do a horizontal drilling. I'm not sure how much they are in your area, but I recently watched a crew do a short-ish one (~30') and it works well.

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          • #6
            My setup is similar to yours. The straightforward answer is run the usual 240V (4 conductor) 60A feed to
            the building. Get an 18 inch deep trencher like I did and throw in PVC conduit.

            If you have time and cash for education, convert to solar with batteries. But batteries are expensive, high
            maintenance, and short lived. A really clever system might let your vehicle batteries also serve light duty
            as your battery system.

            If you expect to open the garage door by radio, it would need to be powered continuously. Running an
            inverter continuously will up the KWH usage by orders of magnitude over a battery powered opener used
            occasionally. I get annoyed by the 1W the radio uses continuously.

            Many HF bat maintainers have been used here. Note that as the bat levels off, each maintainer
            continues to draw a few W, very poor efficiency. If you turn off the AC, they will run your bat down. Poor
            efficiency adds up with several in use, running an inverter is much worse. Better to work out a sun
            powered system which has no back drain after sunset.

            I have equipped all starting batteries (car, tractor, generator) with EC3 connectors, no clip leads for
            regular service. They are compact, cheap, robust, polarized, and you can make dummy dust covers
            out of extras for when on the road. Plug in your maintainer or inflator, an Anderson might also be there
            for much bigger stuff.

            Reality is air systems leak, another continuous drain on battery power. I decided to use a very small air
            tank, which can be pumped up very quickly only when needed. Those 12V tire inflators could be operated
            directly from a vehicles bat on the rare times needed.

            Minimal 12V LED lights won't need much. That is if you don't forget to turn them off, better use some with timeouts.
            good luck, Bruce Roe

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