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Who has solar panels?

Discussion in 'Solar Power' started by johnElarue, Dec 23, 2009.

  1. Jan 5, 2010
    johnElarue

    johnElarue Lovin' The Homestead

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  2. Jan 5, 2010
    sylvie

    sylvie Recycled Spunk

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    Great link, John! thanks!

    No problem :)
     
  3. Jan 16, 2010
    xpc

    xpc Doubled and twisted

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    A simple 5kw grid tied system will cost about $20,000 in parts and about the same for installation, there are many states that have rebates and incentives and all need an approved installer who also knows that (hence the high install costs). You can take the 30% fed tax credit but doubt the others will allow grid hookup without all the approvals and $3000 permits.

    In a good state with all rebates a $40,000 system could end up costing you only $20,000, at a net metering rate of 25 cents times 500 kwh will pay you $125 a month and over 10 years will pay you $15,000 (usually the length of the contract). Of course you still have to pay your regular electric bill at the prevailing rates.

    A 30 watt panel will run a small laptop a few hours a day (sunny days).
     
  4. Jan 16, 2010
    Farmfresh

    Farmfresh City Biddy

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    We've missed you xpc!
     
  5. Jan 16, 2010
    xpc

    xpc Doubled and twisted

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    Thanks, now go hook up those PV panels of yours and start saving the planet (that wasn't too snippy was it?).
     
  6. Jan 16, 2010
    Farmfresh

    Farmfresh City Biddy

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  7. Jan 23, 2010
    johnElarue

    johnElarue Lovin' The Homestead

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    Ok here goes,

    Got the 3- 50watt panels installed on the roof. Just waiting on the battery. Then will wire'm up and start making power. I like to think of them as my " solid state generator" , no moving parts. No fuel needed.

    Firstly they'll be used for outdoor lighting, then will run some wires into the house. This setup should hopefully provide enough power to light the house in an emergency.

    We have "candlenight" once a month for fun, soon we'll add "solarnight"(s)? I'll probably spring for the warm yellow LED's, maybe 5 for the house.

    [​IMG]
     
  8. Jan 23, 2010
    xpc

    xpc Doubled and twisted

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    Looks like you have some Sun-50s there (they all look a like), I have seen those as cheap as $100 each. What kind of charge controller do you have? only a MPPT type will harvest near all the juice that panel will give out, the 50 watts is based on 19 volts so a 12 volt charge controller will only be able to take 35 watts of it until 13.5 volts or full battery charge.

    Having your system de-rated from 150 watts to 100 watts without ever turning it on sucks, but every PV cell made will be the same and on average be de-rated by 30%. even those new 315 watt cells will most likely only make 220 watts by the time all the efficiencies are accounted for. Remember they rate these things in a laboratory under ideal conditions that will never be seen outside.

    A 12 volt battery with a 100 amp@20 hour rating would give you 60 watts total per hour, to keep the DOD (depth of discharge) at 25% or less only use that amount for 5 hours or 300 watts max. You can draw down twice as much with a total of 600 watts but will cut the battery life in half. I always use an insolation of 4 hours so your array will on average produce 400 watts a day based on 12 months year around usage.

    Using 12 volt light bulbs would be best, as the cheap car inverters can have an efficiency of only 80%, costing you 2 watts for every 10 watts used. They also tend to have an automatic cutoff set too high and will not allow the full use of the battery. My experiments with a 30 watt pv cell, 15 amp charge controller, 700 watt inverter and a marine battery worked ok for a while but never got the battery up to full charge and it died beyond recharging inside of 6 months.

    As emergency lighting you should be able to run four 13 watt CFL bulbs for 5 hours on an inverter, so it should do as you plan if you don't count cloudy days.
     
  9. Jan 23, 2010
    johnElarue

    johnElarue Lovin' The Homestead

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    Hi xpc,

    Thanks for the reply, some answers and questions:

    They're 50 watt Chinese, (yeah I know, I know) seem to be of good quality. 2$/watt , but with shipping 4$/watt.

    I have a Morningstar Tri-star 45Amp controller, not a Mppt but should do the job. Actually I'm thinking of using a smaller 20A, non mppt till I figure out what the heck I'm doing. I can get a mppt fairly cheap considering, do you think it is worth it?

    The panels are rated open circuit 22V , and 17V (closed? /load on) excuse my terminology.

    Actually funny to hear that, didn't plan on harvesting 100% of course, only 50%. Worse yet, we only get 5hrs of sun, when it is shining!

    I had it calculated at 375watts/day based on 50% of optimum performance in full sun, so again glad to hear I'm on track.

    I'd rather not go with the expense of DC fixtures, things like that here are very expensive. I also made a 30 watt wind turbine that wouldn't charge a battery, it lasted maybe 3 months.

    I'll be using a 100watt inverter for starters and moving up to 2-300watt probably max.

    I originally thought using 13watt CFL's, but then figured the new 3watt LED's would be no problem with the 100watt inverter, inefficiencies and all considered. Being able to run those about 10hrs \day if necc.

    Thanks for the response and please feel free to critique my setup, everyone.

    john
     
  10. Jan 23, 2010
    xpc

    xpc Doubled and twisted

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    All my numbers are ballparks and guesstimates at best, only after installation and monitoring for a full year can you get true numbers. And you are right, off-grid systems are generally de-rated by 50% and grid-tied by 30%.

    MPPT controllers are best suited for the smaller low voltage systems as they work like a switched mode power supply (smps) and will actually ramp the voltage up when there is shade or partial sun so it will glean all the power from the PV cell as possible, I have seen numbers of 10 to 20% higher than with a standard charge controller. Very simplified it will essentially take 9 volts and up-convert it to 13 volts so it will charge the battery, the amperage will be reduced as will the wattage but it will create power were none existed before. The $200+ price tag for a 15 amp system would have to be weighed to justify it.
     

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