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OT:Solar power system questions

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  • wierdscience
    replied
    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.

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  • J Tiers
    replied
    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.

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  • jdunmyer
    replied
    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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  • J Tiers
    replied
    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.

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  • Evan
    replied
    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.

    Leave a comment:


  • wierdscience
    replied
    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.

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  • jdunmyer
    replied
    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.

    Leave a comment:


  • J Tiers
    replied
    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..........

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  • jdunmyer
    replied
    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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  • J Tiers
    replied
    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.

    Leave a comment:


  • wierdscience
    replied
    Originally posted by J Tiers
    The panels the tree smashed were "folded over", the top 1/3 of the panel was at a 60 deg angle to the rest.

    But, they were actually still putting out about 40% of the power they had before being squashed.

    Arrays are not necessarily that fragile. And new ones have very substantial frames. The frames of the individual Carrizo panels were minimal, almost an "edging" only.

    The overall frame was bent by the tree, or the panels might have been un-damaged. The tree fell about 40 feet and the panel setup was hit by two forks in the branch. The first one the panels actually split off the tree, likely without damage, but the second and larger one bent them.

    I assembled my system for less than $1000, including a 2500W inverter, but you can't do that now. Panels have gone up a lot, and no more used ones are out there. Apparently some countries have tax credits, and they are buying every panel that can be made... no discounts.
    I'm not as concerned with tree damage as I am them turning in to frisbies and ending up with Dorthy and Toto,but it is incouraging that they can take some abuse and still function.

    There are some panels out there that aren't too bad price wise,the Chinese models for one.

    How much wattage in panels did you have for what capacity system?

    Leave a comment:


  • J Tiers
    replied
    The panels the tree smashed were "folded over", the top 1/3 of the panel was at a 60 deg angle to the rest.

    But, they were actually still putting out about 40% of the power they had before being squashed.

    Arrays are not necessarily that fragile. And new ones have very substantial frames. The frames of the individual Carrizo panels were minimal, almost an "edging" only.

    The overall frame was bent by the tree, or the panels might have been un-damaged. The tree fell about 40 feet and the panel setup was hit by two forks in the branch. The first one the panels actually split off the tree, likely without damage, but the second and larger one bent them.

    I assembled my system for less than $1000, including a 2500W inverter, but you can't do that now. Panels have gone up a lot, and no more used ones are out there. Apparently some countries have tax credits, and they are buying every panel that can be made... no discounts.
    Last edited by J Tiers; 09-10-2007, 10:38 PM.

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  • wierdscience
    replied
    I'm not looking for free electricity,pay me now pay me later is still in effect.If I could shave a few dollars off my monthly bill it would be nice.Using the system after a storm for running a few lights or fans or for that matter just saving a freezer of food would be nicer.In that case the cost of a small home built system might payback in a couple weeks.

    I rode out Katrina,power was off two weeks here,1-1/2 in town and then on again off again for about 4 months later.A 5,000 watt Briggs generator drank 7 gallons of gas in about 8-9hrs run time,gas when you could find it was $5+.All that generator did was run lights a couple hours after dark and a couple fans so we could sleep,it sat idle during the day.$35/day especially when gas is scarce and you have basicaly no income because work has shutdown is difficult to manage.In two weeks of run time $500 goes down the toilet not counting the cost of the generator in the first place.From what I see a small home system could be assembled for less than $2,000.Diffrence is the solar system is quiet and won't be running out of fuel anytime soon.

    I know the flaw in my thinking is possible damage to the panels in a storm,simple answer is bring them inside until the storm is past,average storms can be handled by plexi covers.After a storm like Katrina payback could be in a matter of a couple weeks.

    We haven't even considered the age of our grid system and the possibility of terrorism.IMHO our grid system is one of the weakest areas we have and I believe the crazies realise this too unfortunately.

    Leave a comment:


  • wierdscience
    replied
    Originally posted by Your Old Dog
    Got Rhode Island Red cartoon character in my head.......

    "I say I say come on men, answer the booooys question! I say I say the sale ain't gonna last forever you know!"

    My trailer has a round vaulted roof and these particular units (3seperate one to a panel) would lay nice on the roof.
    He was a HSM you know,Foghorn Leghorn,ever see the one where he is chasing the dog around the barnyard when he stops and chops down a tree drags it into the shop and spins a ball bat out of it to whack the dog?

    Leave a comment:


  • jdunmyer
    replied
    Here's a link to an article I wrote several years ago on the subject of solar power for RVs: http://www.fiberglassrv.com/solar.html

    Since the article was written, we've changed trailers and now use an MPPT controller and 2 golf cart batteries. Most of the rest still applies.

    As others have said, if your object is to save money by using solar power, you should lay down until the temptation passes: it ain't gonna happen. If you want backup, get a generator, fueled either by Diesel or propane; Diesel fuel keeps pretty well, and propane will keep forever. You should be able to store enough fuel for at least several days, and by then you should be able to get to some place to get more. Be sure to exercise your generator regularly, or it won't work when you need it. My genset is shown here:
    http://www.oldengine.org/members/jdunmyer/genset/

    Rigid conservation measures will save much more $$$ than any solar system.

    My comments do not apply if you're off-grid.

    Leave a comment:

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