First solar power system and unique situation? Need advice.

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  • Scargo
    Junior Member
    • Mar 2011
    • 2

    First solar power system and unique situation? Need advice.

    My first post. We have a cabin, on a lake, in a remote area of British Columbia. We are completely rebuilding it. In the past we have run almost everything off propane or generator. We're new to the concept of off-grid solar power.
    We will have a main cabin that's 550 SF and three bedrooms that total about 400SF. We have a spot about 20 feet from the distribution panel where we can get about five hours of sun per day in the summer. We need to draw water from the lake; about fifty feet away from the power distribution. We may want to use a winch to haul light boats out of the water from about the same distance away. Bedrooms are 25-50 feet away, though their power usage will be minimal. All lighting will be LED. I'm familiar with it.
    Our use is primarily for two-three weeks in the peak of summer, though the cabin will be well insulated and winterized. We want to have an adequate system, though we have been used to "roughing it" while there. We may rent it at some point so we don't want to cut corners on a system by much. It is a rainy area except for summer. In my calculations I have accounted for two days of no sun and 50% battery usage. If the cabin is used during off months there will only be one or two people there, thus much lower power needs. We are in this area: 1,023+ kWh/kW Photovoltaic potential (South-facing, tilt=15 degrees). 120-135 kWh/kW in the three summer months. We have a few trees that will come into play during early and late day. I plan on using tracking devices.
    I have come up with 4.5kw hrs/day average consumption when a full crew is there; which isn't often. I think I should have a 24 or 48 volt system because of the two~three long high amp wire runs to the pump and winch. I'm trying to size components. I think I could do four, 230 watt, high efficiency solar panels and use four, 6v. 230 a/hr. batteries.
    How have I done for a start?
  • Mike90250
    Moderator
    • May 2009
    • 16020

    #2
    unless you really have decided you need the trackers, ditch them and get extra panels. Moving parts = maintainance + repairs

    Are your winches / motors / pumps Dc or 120 / 240 AC ?

    Not sure how you are calculating this kWh/kW or what it is.
    there are watts, and then watt hours, but not combined as you did.
    A 200W panel, for 2 hours, generates 400watt hours
    A 10 w light for 7 hours is 70watt hours

    it is best to wire for a higher voltage, with series batteries, than low voltage, and parallel batteries. 6V golf cart batteries make a good starting point.

    Pumps/motors may need their own remote battery and you sneaker net them back for recharge, the cable costs are too much.
    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

    • Scargo
      Junior Member
      • Mar 2011
      • 2

      #3
      Was thinking DC would be more efficient...

      My impression is if I can use PV direct or at least bypass the inverter that I will reduce power loss. I intend to use DC pumps and DC accessories whenever possible.

      The issue of "kWh/kW" nomenclature is straight off the link I gave. I believe I incorrectly combined the 1,023 number with the nomenclature when I said, "We are in this area: 1,023+ kWh/kW Photovoltaic potential... ". It is not too important. I was trying to make the point that we have lots of sun in the summer months.

      I like the idea of just carrying a battery to the pump, but it is impractical when others are there and they expect a fairly uncomplicated existence or are not capable.
      I think a Solar slowpump P-1322, PV direct pump that uses 168 PV watts (I think @ 15 volts) would work fine. Not sure at this moment what size wire would be required for 50 feet.
      Then there is the issue of an additional high volume pump that we can use in case of fire. I haven't spec'd that yet but it may have to run off AC.

      Comment

      • russ
        Solar Fanatic
        • Jul 2009
        • 10360

        #4
        It is not bypassing the inverter that saves you losses so much as bypassing the batteries.

        The kWh/kW is just the insolation multiplied by something like 275 - doesn't really mean anything. PV Watts will provide more usable information.
        [SIGPIC][/SIGPIC]

        Comment

        • ionized
          Member
          • Apr 2010
          • 83

          #5
          Reliance on battery power for fire fighting troubles me. Can you pump water to a tank with sufficient head?

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