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OT:Solar power system questions

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  • #31
    I had/have about 100W in panels, with 400 AH of batteries. This system is primarily for lights in the building (all 12V) including a motion detector light outside. Other 12V loads include a pond pump.

    It is also used for incidental 120V loads, such as a drill press and other power tools including an air compressor (Craftsman roll-around). They don't get a lot of use, but they are really handy when needed.

    If I used those heavier loads much I would have to put up more panels per the general guidelines I mentioned in a prior post. As it is, it provides power where there wasn't any, serves as back-up power for the house, and allows me to check out various related products and devices. The irregular heavy usage and short-term nature of the lighting usage allow the small panel setup to work out OK.
    1601

    Keep eye on ball.
    Hashim Khan

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    • #32
      At retail prices, my 2, 75-watt panels, controller, and eMeter would cost about $1500.00. Because of a "hot deal" on some seconds, my panels cost only $225.00/each instead of about $450.00/each, so I came in at "only" $1000.00. Plus about $150.00 for the batteries. Output? Nearly 1/2 Kwhr/day! At our price here, that's about $.05/day or $1.50/month. If it's sunny every day.

      As far as ruggedness, most solar panels have tempered glass in front, they're very sturdy. I doubt that most hail storms would damage them.

      A solar system that will do what you want will run closer to $10,000.00, that'll buy a lot of gas every few years. Figure 8% on your money, and that's $800.00/year, which will buy all the power you need for lights, etc.

      I hate to be a wet blanket, but them's the facts. I liken what you're proposing to the fella who drops in here and insists that he's going to buy a Harbor Freight 7X10 Mini-Lathe to make big parts, to .0001" tolerances. We'd all advise him against it, as he'd be wasting his money and getting frustrated in the process.

      <<Jim>>

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      • #33
        Naw, it's not that bad....

        And I know folks who are in places as much as 2 miles and $15,000+ from the grid, who have put in LARGE systems for around $5000. Enough to run their houses.

        Point being that if you are all about the Benjamins, it may not make sense. But if you expect situations in which all those Benjamins may not make a lot of difference, then it makes sense.

        It might make NO sense to put in a $10,000 backup generator either. You can always do without for a few days, or go to a shelter/displacement camp. And if, as is usually the case, it is a natural gas generator, then just when you really need it it may be down due to pump failure at the gas Co.

        You pay a lot for insurance, have you got that much back from it? With interest? Would have made more sense to invest the $$.

        It's all choices..........
        1601

        Keep eye on ball.
        Hashim Khan

        Comment


        • #34
          Well, if W.S. is really interested, he should do the arithmetic before spending his first dollar. It's quite easy, and outlined in my article and at several of the solar sellers' sites.

          Home Power Magazine wrote up several whole-house installations, and IIRC, they were talking something like 15-20 grand to give the owner something approaching grid power capabilities.

          Again, it ain't rocket science, just simple math. If you don't do it first, you're likely to be disappointed. I'm agonizing at present over a new refrigerator for our trailer. The late models all require 12VDC for the electronics, even when running on gas. I'm told that about 500 Ma will do the job; that's 12 AH/day, nearly 1/3 of what my system is capable of. The pilot light that tells me the pump is 'on' draws 100 Ma, even that is 2.4 AH/day. It all adds up, and when you're off grid, you pay attention to those things.

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          • #35
            Originally posted by jdunmyer
            Well, if W.S. is really interested, he should do the arithmetic before spending his first dollar. It's quite easy, and outlined in my article and at several of the solar sellers' sites.

            Home Power Magazine wrote up several whole-house installations, and IIRC, they were talking something like 15-20 grand to give the owner something approaching grid power capabilities.

            Again, it ain't rocket science, just simple math. If you don't do it first, you're likely to be disappointed. I'm agonizing at present over a new refrigerator for our trailer. The late models all require 12VDC for the electronics, even when running on gas. I'm told that about 500 Ma will do the job; that's 12 AH/day, nearly 1/3 of what my system is capable of. The pilot light that tells me the pump is 'on' draws 100 Ma, even that is 2.4 AH/day. It all adds up, and when you're off grid, you pay attention to those things.
            Maybe you mis-read,but I'm not thinking of anything even close to grid power,like I said all of my heavy current loads will be on the grid,that load could be in excess of [email protected],no way would I even consider doing that with solar.
            The only thing I want to do is run the lighting in the shop,at night after the system has had 10-12 hrs in the sun during the day(I work during the day so the lights will be off then).3hrs at a 800watt max load in the evening ain't much.
            I just need one more tool,just one!

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            • #36
              Darin,

              If all you need is to run some lights and a freezer then why use a 5000 watt generator? That's inefficient as all get out. A 1000 watt inverter unit with idle back will do that and use a tenth of the fuel of the 5000 watt unit while it's doing it. I'm just finishing up building one right now. Total cost about $150 for the inverter and a battery to prevent power loss during refueling as well as act as a voltage regulator. The rest is a lawnmower engine and an alternator salvaged off an old vehicle plus a few odds and ends in my packrat stash. I'll put up some info as soon as I get the electronic throttle servo control finished, probably today sometime.
              Free software for calculating bolt circles and similar: Click Here

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              • #37
                Originally posted by wierdscience
                Maybe you mis-read,but I'm not thinking of anything even close to grid power,like I said all of my heavy current loads will be on the grid,that load could be in excess of [email protected],no way would I even consider doing that with solar.
                The only thing I want to do is run the lighting in the shop,at night after the system has had 10-12 hrs in the sun during the day(I work during the day so the lights will be off then).3hrs at a 800watt max load in the evening ain't much.
                Eh... hate to be the one to break it to you, but that is 2400 watt-hours. Remember my example above? That was for 500 watt-hours.

                Start multiplying by a factor of FIVE.

                If you want to use solar, then you need to use more efficient lighting, or you will have to re-size the system upwards by a LOT.
                1601

                Keep eye on ball.
                Hashim Khan

                Comment


                • #38
                  WS,
                  An 800 watt load for 3 hours equates to 200 Amp-Hours from your batteries. The draw will be about 67 amps, so you'll need some very sizable batteries to supply that w/o ruining them in short order. Also, you don't want to run your battery bank much below 50% charge if it's to give you good live. Just off-hand, I'd say you'll have to use the equivilant of 8 golf cart batteries in a series-parallel configuration. That would keep the draw to about 17 amps on a given battery, and the AH usage would be very doable.

                  Now, to get 200 AH of charging, you'll need about a half-dozen 100-watt solar panels. Those run between $500.00 and $600.00/each.

                  All of the above assumes 100% efficiency, and no loss from the inverter. Figure 80% overall, and you'll be closer.

                  If you want to experiment, I'd recommend that you buy one or 2 panels of [whatever] size, a 12VDC flourescent light or 2, and a pair of golf cart batteries. Get some metering of some sort so you can tell what's going on (you wouldn't attempt machining w/o measuring tools, would you?) and have at it.

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                  • #39
                    More like 240 amp-hours, with losses. And I would figure closer to an 80 amp draw, for rough estimation purposes.

                    Golf cart batteries are about 200 AH, so you'd clearly need several strings of them as mentioned.

                    It would be SUBSTANTIALLY cheaper to get more efficient lighting and THEN size the system.
                    1601

                    Keep eye on ball.
                    Hashim Khan

                    Comment


                    • #40
                      I may have caught a break today,I'm on the trail of a local junk dealer who is reported to have a "stack" of used panels.I'll know more tomorrow,wish me luck.
                      I just need one more tool,just one!

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