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  • Newbie Questgion


    I have spent some time looking through this forum, other forums and Google, etc. I am so confused so please excuse me if this is posted somewhere and I just don’t get it.


    My wife and I are in the process of buying a small cabin in upstate NY. There is no grid power available. There is a large propane tank, woodstove and a small refrigerator (electric) that I assume the previous owner used a generator.


    My goal is to design a hybrid system (not sure if this is the correct term) with battery power from solar along with a backup generator. I am not looking to go complete solar, I want to be able to have some electrical capacity without running a generator 24/7. I plan to use propane as much as possible. Below is a list of appliances off the top of my head. Cabin would be used in spring, summer and fall mainly with temps getting near or around freezing at the beginning and end of seasons.


    Fans 10 WH

    Lights 280

    Micro 4

    TV 45

    Refr 750


    Total ~ 1100

    25% 275 - Laptop/phone chargers and other miscellaneous

    1375 WH/Day


    I currently own a 3500W generator as well as a portable 2000W generator.


    The goal is to provide electricity without constantly running a generator. My head is spinning trying to figure out the size inverter, solar panels, etc.


    Initial thoughts are to get a 3000W Inverter/Charger. I am banging my head trying to figure out battery requirements and solar panel requirements. There is a tree line to the south of property so I assume solar would be marginal at best.


    Questions.

    What size battery bank would be required?

    Would it be possible to run one of my generators during the day to charge the battery bank?

    Would it be feasible to set up solar to trickle charge while we are not there to prevent depletion of batteries?

    Am I way off base?

    https://poweredportablesolar.com/pro...000-flexx-kit/ - $7595 - is buying a kit a good way to go?

    Other suggestions/opinions please?


  • #2
    One option is having a battery bank charged by a generator that kicks in when the battery bank gets low. I did not know about that when I built my system for my RV.

    I recommend staying away from kits. I did not find any good kits when I was looking. I did not look too much at your kit, but it had flexible panels. These may not last as long as flat panels. I'm told for my climate in AZ perhaps as quick as a year. I've not seen the warranties on these flexible panels as I have on flat panels. A lot of kits come with hidden costs like inadequate wiring, no circuit breakers, mounting brackets, all things that add up$$.

    You can take a look at SANTANsolar.com for some inexpensive larger panel pricing. Some of these 400 watt panels sell for the same price as 100 watt panels. Shipping may kill you on the larger panels, but I'm sure you have a distributor local.

    For battery bank, if you go to batteryuniversity.com you can learn a lot about batteries. If your calculations show 1375 wh a day, four tall golf cart flooded lead acid (FLA) 6 volt batteries may be enough. My system has those, and it's around 5200 wh of power, because its FLA I can use 50% or 2600 wh before I need to charge it, which two days worth of electricity at 1300 wh per day.

    For the batteries getting charged by the generators, you can look at transfer switches. I do not hook my generator to my batteries on my RV. If I use my generator, it is because I have some high draw loads like the microwave. I read about transfer switches being set up to auto switch between generator and battery operated.

    With the lights, its amazing in my RV how little the LEDs draw. I replaced four small incandescent bulbs at $10 per LED bulb. I had about 3 amps of draw off those incadescent volts and dropped it to next to nothing, perhaps .5 amps. THat may bring down your 280 if you haven't done an LED conversion yet.

    The system I described, you could rent a trenching tool and burry quite a length of electric wire to make your cabin grid tied for less money than what I mentioned. I'm thinking if you go quality in your solar build and install this yourself, it may be around $8k, with all new parts and no hidden costs.
    Last edited by chrisski; 11-25-2020, 08:39 PM.

    Comment


    • #3
      You're right to start thinking battery now. That's the biggest question and probably the biggest cost factor in the whole system.

      Solar is often limited by roof space. Once you figure out how many solar panels you can fit on the roof, you can use a tool like PVWATTS to determine how much energy that will produce per day in each month. Expect very little in November and December, when the sun is lowest and shade is worst. The number of panels and amount of load will determine the size inverter you need.

      You mention using a generator to fill in the gaps. The batteries fill in the gaps when the generator and solar are both off. For example, in winter (virtually no sun), if you run the generator for 4 hours a day every day, then you need the batteries to supply your expected load for 20 hours. That load is the accumulated load (integral of power over time), not peak load.

      We recommend buying at least 2X the battery capacity of your needs, so that you never deep-discharge the batteries. That prolongs battery life. Any battery lasts longer if you don't discharge it much.

      Others here can comment on using solar to keep batteries charged.

      A kit is the least flexible solution, so I would expect it to be the poorest place to start. But you can't be sure until you price an alternative.

      Others here are doing similar systems to the one you plan. They can give you detailed recommendations on components, such as the best batteries and inverter/chargers.

      The other concept worth noting is that anything you can do to reduce power consumption will be more cost effective. Your fridge is the biggest user, so start there. Can you switch to an outdoor fridge in the winter? That fridge would run very little time because outdoor air is so cold. Mother nature can cool your food for free.

      Then address the lights. Are you using the most efficient lights (LEDs, skylights, etc.)?

      I hope that this is a bit of help.
      7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

      Comment


      • #4
        Avoid auto start generators. They are fine, till they dont. And you forgot to add oil. or it's monthly test cycle ran out of fuel.

        How long do you want to forgo using the generator. ?

        Your lighting usage looks high, have you converted to LED bulbs yet ? I doubt I can turn on all my 2 stories worth of lights, and reach your wattage.

        A usual scenario is run the generator for a couple hours in AM, make coffee, nuke breakfast and charge batteries. Then let solar do the day thing, and run genny for a hour in evening to prep dinner and charge.
        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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        • #5
          Thanks everyone. I didn't think about the lighting, so I will definitely switch over to LED's. I have also researched propane refrigerators. I did not mention but we have an RV. I was actually thinking of trying to make something that is portable or somewhat portable so that I can take it with me, with the exception of the solar panels. We have plenty of time since I will not be doing anything until spring. This is all new to me and I appreciate all the help.

          .

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