New to Solar, need some assistance or direction

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
Well I'm brand new to solar energy. I want to create a nice system to power an appliance but from the snippets, facts and pdf's i've read it doesn't look like it will be an easy task to undertake by myself. The appliance I want to run uses 1300 watts per hour. I need to run this applience for 12 hours a day, 7 days a week totalling 84 hours a week at 1300 watts per hour. the appliance has a 11.5 amp start up(i dont really understand this but does it mean i need also a car battery?). How many deep cycle batteries would I need to store the energy to run this applience strictly from solar?
btw cost is no object.

-bryan
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    Re: New to Solar, need some assistance or direction
    orinjjuse wrote: »
    btw cost is no object.

    You really mean that???

    Anyway, a back of the envelope calculation (using this government website to predict panel output):

    Assume: Near Albany New York, that you will run 9 months of the year on full solar, you will still need a backup generator for bad weather, fixed array, standard flooded cell batteries (80% efficient), 95% efficient charge controller, 85% efficient 120/240 VAC inverter (total derating factor of 0.52).

    1.3kW * 12 hours/day * 30 days per month = 468 kWhrs per month

    Using the Government website (0.52 derating factor for off-grid system) we find that a 1kW panel will give a minimum of 59 kWHrs per month minimum for 9 months out of the year (low is 35-37 kWhrs per month in winter)...

    468 kWhrs per month needed / 59 kWhrs per 1kW of panels = 7.93 kWatts of solar panels (you would need 2x as many panels to run solar during November/December months)...

    Amount of batteries needed (battery should be 6x rated load--3 days of no sun with 50% maximum depth of discharge):

    1,300Watt * 12 hours * 6 * 1/85% (inverter efficiency) * 1/48 volt battery bank = 2,294 Amp*Hours at 48 volts

    Rough costs:

    7,930 watts of panels * $5 per watt = $39,650 of solar panels
    2,294 amp*hours of 48 VDC batteries =$30,000 (good quality batteries)

    Another $10,000 to $20,000 for mounting, charge controllers, inverter, wiring, etc...

    $80-$90,000 of parts (not including generator cost).

    Price per kWhr for electricity from solar (7.93kW of solar panels will generate 6,047 kWhrs per year--average):

    ($85,000 + $30,000 battery change) / (6,047kWhrs per year * 20 year life) = $0.95 per kWhr (not including taxes, other maintenance, etc.).

    Fuel costs, assuming 5kWhr per gallon of fuel (fairly efficient gasoline generator) with 80% charger loss, + 80% battery charging losses, + 85% inverter losses, and $4.00 per gallon fuel costs:

    $4 per gallon / (5 kWhr per gallon 1/.8 * 1/.8 * 1/.85) = $1.47 per kWhr fuel costs (excluding generator costs, wear and maintenance)...

    It is a start...

    -Bill

    PS: I guess I should add what the fuel costs would be if you simply ran the generator and skipped the whole battery storage thing...

    $4 per gallon / 5kWhrs per gallon = $0.80 per kWhr

    -BB
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
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    Re: New to Solar, need some assistance or direction

    Does this need to be a stand alone, off grid, or are you willing to offset the energy used by the appliance from your grid power bill? Rule of thumb, off grid systems increase the cost by a factor of ~2. If you can keep it grid tied you can either buy twice the capacity, or buy a system at 1/2 the cost.

    Tony
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  • System2
    System2 Posts: 6,290 admin
    #4
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    Re: New to Solar, need some assistance or direction

    BB. you rock my socks with those figures, thank you a ton. I'm currently a student but this project has nothing to do with my curriculum. If i could get a grant, life would be a lot easier but im also willing to buy parts one by one. I'm trying to use only natural fuels(mainly wind and sun). I wish I could run this system closer to home but more than likely i'm focusing on regions with 360 or so days of sun that have no power grids for miles. I saw on the history channel or discovery something about an area around the southern pacific coast that gets about that many days.

    to be honest, it's not that bad. the technology for solar panels is getting better as time progresses and i beleive this appliance will be able to offset whatever cost it produces. my goal is to be able to run 61 of these appliances but i have to get 1 working first :) the numbers all seem realistic and not even that daunting for the benefits it could possibly provide.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #5
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    Re: New to Solar, need some assistance or direction
    orinjjuse wrote: »
    BB. I'm currently a student but this project has nothing to do with my curriculum...

    Ah Ha! A student--that explains "cost is no object"... :p (just teasing ;) )

    Don't expect costs to go down much yet... There is really nothing out there for small scale installations that is going to save a bunch of money (thin film panels--I don't think they are any where near the $1 per watt magic price point--let alone the rest of the costs that are rising--copper, aluminum, lead for batteries, labor, taxes, etc.).

    In the US--we are probably pretty much in the golden age of solar (if there will ever be one)... Certainly as fuel costs soar--solar will "look better"--but the material and labor that go into solar will also increase the costs for solar as well...

    On this forum, most of us preach conservation first... For example, that load of 1,300 watts for 12 hour per day is over twice the monthly electric load of my SF Bay Area suburban home with family of four (no A/C required, natural gas for heat/cooking/hot water).

    For many people, solar thermal (hot water, domestic heating, process hot water) is a better investment vs solar electric...
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
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    Re: New to Solar, need some assistance or direction

    may i ask seeing as nobody else did what this appliance is and why 12hrs/day?
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  • System2
    System2 Posts: 6,290 admin
    #7
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    Re: New to Solar, need some assistance or direction
    niel wrote: »
    may i ask seeing as nobody else did what this appliance is and why 12hrs/day?

    yep, you can definitely ask :)
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
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    Re: New to Solar, need some assistance or direction

    i pmed you with more questions and observations.
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  • Moe
    Moe Solar Expert Posts: 60 ✭✭
    #9
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    Re: New to Solar, need some assistance or direction
    orinjjuse wrote: »
    yep, you can definitely ask :)

    Sounds like a daytime 500 watt radio station to me. ;)
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
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    Re: New to Solar, need some assistance or direction

    rather than leave the thread hanging, i advised orinjjuse that there may be further options and that the appliance he had in mind actually was 24/7. yes, ouch. i thought he may wish to reconsider doing this via solar unless it proves itself via utility power first for i pointed out a more conservative way of doing what he had in mind that he was already aware of. without revealing the appliance i can state that the appliance was meant to save space for a certain agricultural application. i've kept this vaugue as he indicated he didn't want it revealed.
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