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Solar Powered Generator?

  1. Jun 2, 2016 #1
    Hello all!
    So, my father works as a general contractor (I would work for him over the summers during high school). Being that we live in some what of a rural area, for some of our jobs we would be limited to bringing a gasoline powered generator to run all of our electrical needs until we were able to hook up to the electrical grid. With it being summer (here in the US) and it being my first summer not doing work for my dad, it got me thinking how much money was put into that generator with repairs and gasoline over the summer (last year in particular). Plus, how in some cases it would set him back. I am going into my sophomore year of college this up coming fall in a degree in engineering science (so I am lacking the knowledge in electricity for now to completely answer this question, and I wanted to hear from some actual electrical engineers on this question.). Anyways, do you think its possible to build a cost effective solar powered generator that could meet the electrical needs to say, at max power an air compressor? Or say anything in the ~2000 watts range? I have looked up to see if generators like these exist and they are quite costly compared to their gasoline/diesel cousins. I apologize if this is a silly question. Thank you so much!
     
  2. jcsd
  3. Jun 2, 2016 #2

    anorlunda

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    The cost of solar PV panels is under $1/watt. Figure $2-3 per watt including inverter and racks. Does that fit your budget?

    You'll have to be more specific on your load requirements.
    How many watt-hours do you need during the 5 sunniest hours of the day?
    How many watt-hours do you need during the rest of the day?
    Must your supply be reliable, able to work no matter what the weather?

    If you must have a gasoline or diesel generator to meet reliability requirements, then adding solar panels only contributes savings in fuel consumed.
     
  4. Jun 2, 2016 #3
    Thank you for responding! Well, Its difficult to say the amount of watt-hours. Depending on the job and whats being done it can vary wildly, plus what tools are being used. I am also not entirely sure of the compressor run time while it is filling the tanks. I should have looked into this more, my apologies.. A very rough guess would be ~10,000 watt-hours a day. It should be fairly reliable and operating in most weather conditions would be ideal. I honestly was just curious how this would work out first but I would like a budget under $1000.
     
  5. Jun 2, 2016 #4

    David Lewis

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    If your system uses an inverter to convert DC to AC, that would also need to be figured in.
     
  6. Jun 2, 2016 #5
    At Noon on a sunny day, you can only expect about 100W per square meter from a PV system. For 2000 Watts that's 1800 180 sq.ft., larger than many houses.

    Edit: Thanks to @OmCheeto for pointing out the error.
     
    Last edited: Jun 2, 2016
  7. Jun 2, 2016 #6

    OmCheeto

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    I think you slipped an extra factor of 10 into your square footage calculation.
    I only caught that, as I determined that solar doesn't sound like a reasonable option, IMHO.

    Based on CaptainAtom's description, I assume his dad has a big truck, so I found a big truck rack, and its dimensions: 53" x 172" ($560)
    From there I gathered data on a Solarworld 250 watt panel, and determined you could fit 4 of them sideways on the rack, yielding 1000 watts. ($1000)
    4 panels cover 72 ft2
    Doubling that, to match your 2000 watt system, only requires 144 ft2

    I'm estimating about $1000 for the DC to AC inverter, and another $500 for a battery backup.
    So the total cost of the system, which doesn't even meet the minimum requirements is $3000.

    It there were some way to stack extra panels, which could be slid out on site, the system might work.
    Each 1000 watts of power is an additional $1000.
     
  8. Jun 2, 2016 #7
    Ooops, you're right. That 1800 SHOULD 180 sq.ft. Now corrected in the my post.
     
  9. Jun 3, 2016 #8

    anorlunda

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    Yeah, but we can't neglect the OP's requirements for low price and all weather reliability, not to mention that some months of the year he will have to do work in twilight or dark for part of the work day.

    I saw a 8 Kw gasoline generator in a Harbor Freight catalog yesterday for only $600. That's hard to beat for a contractor.

    If we push solar for applications where it makes no sense, we lose credibility. Enthusiasm must not override sound engineering.
     
  10. Jun 3, 2016 #9
    Thanks for replying guys! I figured it might end up being more trouble than its worth for this particular application. But, I still might look into building a much smaller version of this to test out for my own enjoyment. Thanks again!
     
  11. Jun 3, 2016 #10
    If my father keeps having trouble with it, I will definitely look into helping him buy a new one, he tends to keep everything as long as possible to get everything he can out of it haha. But it looks like with current technology and pricing, its not feasible to build a solar powered generator for this application. Thanks for the reply!
     
  12. Jun 3, 2016 #11

    OmCheeto

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    As a "general contractor", I'm assuming your dad doesn't buy his compressors from Harbor Freight.

    Please don't apologize. This is the best question I've seen all week. :smile:
     
  13. Jun 3, 2016 #12

    jim hardy

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    What's the trouble he's having ?

    new sparkplug, clean the carburetor , check fuel filter and change the oil often is about all they really need. Don't leave it out in the rain of course .....
    Daughter had one that the low oil cutoff switch became intermittent, really irritating. I showed her how to disconnect the switch wire, check the oil level, start it and reconnect after a few seconds when the vibration of the engine had knocked the switch back into operating position.
    On that one, also a wire behind one of the outlets had worked loose over the years.
     
  14. Jun 5, 2016 #13
    I'm honestly not entirely sure, he stopped using it after I had stopped working for him last summer. But there was many stupid things that kept going wrong, like tires deflating and the frame would start falling apart from the motor running and vibrating for so long, there were starting issues on many occasions (though I can't remember exactly what was causing them). It just got to the point that my dad couldn't keep putting as much time and money into one generator when he had multitude of other jobs to worry about, and if it wasn't running he usually just didn't have time to try and fix it for the next job. He's been borrowing a friends generator when he needs it. Since my dad owns his own company and has his guys and other jobs and tons of other tools that also need his attention for maintenance or repair from constant use, its very hard for him to take half a day to tear apart a generator to not even find out whats wrong (which has happened on multiple occasions). The main problem I thing is just the over all quality of the generator, I just don't thing it was designed or built well (literally had to take the whole thing apart to get to anything and changing the wheels or replacing the axle was a nightmare, I had to re place some of it after I took it apart). It was given to him by my grandfather, as my grandfather got it and many other tools for a very cheap price, they are all TITAN brand and none of the tools work unfortunately. Either way, I was just curious for my own amusement if building a solar powered one would be possible or even worth while for his applications. Thanks for the reply!
     
  15. Jun 5, 2016 #14

    sophiecentaur

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    You really love this stuff, don't you Jim?
    (The smell of lubricating oil in the morning.)
     
  16. Jun 5, 2016 #15

    jim hardy

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    I think i'd extricate the working parts and re-mount on a 2X4 frame designed for easy access.

    Sam's has a 3kw for $298 ... that's almost disposable.
     
  17. Jun 5, 2016 #16

    jim hardy

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    Especially two stroke.....

    Yes.
    It seems to me wasteful to crush machinery because of something simple.
    By fixing old stuff i can enjoy things i could never afford new.
    Machines have no soul but the people who build them do. Restoring some fine machine is honoring somebody's hard work.
    Rescued one of these from the salvage yard's dumpster, received just fine so gave it to a Ham Radio friend who can legally transmit with it.
    icom.jpg
    For two bucks and a few minutes cleaning, why not try ?

    old jim
     
    Last edited: Jun 5, 2016
  18. Jun 5, 2016 #17

    dlgoff

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    (And the sounds of whirling generators and overhead hum.) :approve:
     
  19. Jun 5, 2016 #18

    David Lewis

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    If equipment powered by solar cells runs on DC you can save money and get more efficiency.
     
  20. Jun 6, 2016 #19

    dlgoff

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    Hope you don't mind me using this (your) quote for my new signature. :bow:
     
  21. Jun 6, 2016 #20

    jim hardy

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    i'm humbled, Don.....

    speaking of machines and souls

    ever see movie "The Red Violin" ?
    I just had to put this junkshop treasure back together
    Violinresized 2- Copy.jpg
    it's Czech 'copy of Jacobus Stainer' probably from between the World Wars
    a friend taught me about 'hide glue' and 'fiddle clamps'
    looking for a bow now.
    I might've posted that picture before, dont quite remember...

    Sorry for the off-topic ramble. Conversations just kinda do that, eh ?
     
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