Another newbie

BoFuller
BoFuller Solar Expert Posts: 187 ✭✭✭
I have calculated that I will need about 2445 watt hours per day, mainly a little microwave, some TV, some PC and a few lights. This is not fulltime though. It will be a long weekend for 2 or 3 weekends, then nothing for 2 weeks, then maybe 7 days straight, then every other weekend.
So would I be safe in dividing that in half? What kind of system do I need for this usage? How many batteries, panels, dollars?
12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Another newbie

    Welcome to the forum.

    2.4 kW hours per day is about what I use running a full-time refrigerator, satellite Internet set-up, computers, lights, microwave, water pump ... Much of it done with clever load shifting. :D

    This is a pretty big investment for an occasional use scenario. You might want to get a Kill-A-Watt meter, a small generator (you'll need one anyway for back-up) and run your equipment from the gen through the K-A-W and get some real-world figures on your potential usage. This will give you a good idea of how much power you're trying to supply.

    Then you're going to want to run a few theoretical systems through PV Watts http://www.nrel.gov/rredc/pvwatts/ for your area to see what sort of 'harvest' you can expect.

    As a general rule (in case you want to price things out a bit and have your heart attack near a good ER) you'd be looking at a 2 kW, probably 24 Volt inverter run off a set of "golf cart" batteries @ 225 Amp hours, around 800 Watts of panel, and at least 30 Amp charge controller.
  • BoFuller
    BoFuller Solar Expert Posts: 187 ✭✭✭
    Re: Another newbie

    We have a 1000W generator that keeps most things running, but I have to switch to the 5000W generator to run the microwave or the coffee maker. I do have a Kill-a-watt meter and used it the past few weekends to come up with the number I stated.
    We want to get away from using gasoline except for an occasional overload, or percahnce we might need to run the A/C. But at 6200 feet, I don't think that will be necessary very often.
    For the next 2 or 3 years we will be working on a log cabin and will eventually retire there.
    12 Kyocera 235 panels, 3 Gyll LiFePO4 batteries (previously 16 Trojan L16 RE-B batteries), Outback 3600W 48V system, Generac 11K propane backup generator, NW AZ, off grid, 6,000 ft (system installed in April 2015)

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Another newbie

    One thing you've got going for you already: elevation. We're at 3200 feet and you can see an improvement in panel output over what it would be at sea level. Thinner air blocks less light, and the temps tend to be cooler much of the year. All good for PV power! :D

    Microwaves are a pain because they draw 1000+ Watts, even if only for a few minutes. Electric coffee maker is another power hog. Propane is your friend when it comes to heating off-grid.

    My wife and I planned to do much the same as you, until she flipped the 4Runner. Now our retirement home is in town for Winter and out at the lake for Summer. At least it's down to an hour drive from six!

    The 1kW gen won't run the microwave, I'll bet. But a Honda EU2000i would. (Voice of experience.) Air conditioning is another nightmare altogether. We've never needed it, having several million gallons of lake in the front yard. Two years ago was the first time we ever had to run an electric fan! I rigged up an old MSW inverter on a boat battery to keep it going over night, then recharged during the day with 'surplus' solar so as to not upset the balance of the system.

    You can see our basic configuration in my sig. It works, but I'd prefer a tad more battery and panel capacity as there is almost no margin for error.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Another newbie

    Look at reducing loads. For example, look at the Coleman stove top Mr. Coffee. For a part time residence, consider a propane fridge. The equation is better for one if the use is less than full time, the closer to full time, the edge begins to go toward a conventional fridge. I would also consider not using the micro, as it is a large dra while running, even if not a huge draw cumulatively.

    We live off grid, using ~ 500-800 wh/day, and get that from 400 watts of PV if you are looking to generate ~ 2 kwh/ day, you will need a system in the 1 k range.

    Tony

    PS. Look carefully at your 2+ kwh of loading. It sounds like a bit of a large load for a small, part time cabin. Perhaps you an detail your loads on this thread so that we can see if there are places to cut a bit, or if they are unreasonable in some other ways.

    T