ALTERNATIVE to batteries...?

I've been reading, in other strings, about the numerous disadvantages of battery systems for storage of power for off-grid applications.

Is it naive to think that we are overlooking an elegantly simpler and safer method/technology...? What about storing our energy in the form of lifting weights while the sun is shining, and dropping those weights when it is not? (Oversimplified, ofcourse)
The advantages would be 1) no danger of acids and lead, 2) energy does not "leak" out of this system 3) no batteries to replace.. 4)?
The DISADVANTAGES would be..1) buffering for instantaneous demand (big capacitors?) 2) big heavy weights that could fall and squiiiish someone
3) nobody's designed it yet?

It seems to me that a resourceful individual could put together a straightforward system of weight(s), cables, clutches, gears, pulleys, ?? and ONE very efficient generator/motor in such a way as to run your energy "up the flagpole" during the day, and bring it down in pieces, as you need it, at night. Looking around the internet, it seems like motors can be had for 90% efficiency and greater, so why hasn't someone built it?

Gordon in Flower Mound

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: ALTERNATIVE to batteries...?

    Hydroelectric/Pump stations already are operational--and from what I have read, one of the most efficient non-chemical means of storing energy.

    There are molten salts batteries that are beginning to be deployed now--and may well be the best way to balance loads. Much longer life than normal lead acid type batteries. Once they are heated, they can stay hot for days (well insulated), and normal charging/discharging is enough to keep them warm.

    Others are looking at alternative ways of shedding/shifting peak loads. One suggestion was regarding large frozen food warehouses. Basically, turn down the temperature off-peak (colder), and let the temperature float up a bit during peak power usage.

    I am sure that there must be other options out there too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: ALTERNATIVE to batteries...?

    Compresed Air is another alternative. Serious research is going on about filling stations having massive compressors and storage tanks which pump up off peak ie overnight to power compressed air powered engine cars . The cars are lighter than conventional cars much smaller light weight engines and Ive read range and efficiency are good. So it may be an alternative. Whether I read this onApril 1st sometime I cant remember but I think it was a serious report. Sounds more practical for the off grider that a massive weight shift distribution system
  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: ALTERNATIVE to batteries...?

    Yep, I had forgotten the compressed air car...

    It has generated a fair amount of news--but I have always wondered about all of the losses from compressing and expanding the air. They claim it is competitive with battery technologies.

    India will be producing 6,000 of this next year--if all goes according to plan.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: ALTERNATIVE to batteries...?

    compressed air car... a lot of heat is generated compressing air, but I suppose when released, you can cool the car with it. SCUBA tanks occaisionaly blow apart when refilling, and that's pretty exciting, a car sized unit, even more so.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: ALTERNATIVE to batteries...?

    Thanks BB I didnt think it was April 1st I read it, the indian link is interesting
    68 mph 120 mile range on a tank full. In built compressor can plug into mains and fill tank in 4 hours. Sounds like an intresting addition to batteries not neccessarily an alternative to batteries as you still have to convert air power back to electrical power. Could be used as a backup genny device to run for 2/ 3 hours pumping power back in to bb
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: ALTERNATIVE to batteries...?
    It seems to me that a resourceful individual could put together a straightforward system of weight(s), cables, clutches, gears, pulleys, ?? and ONE very efficient generator/motor in such a way as to run your energy "up the flagpole" during the day, and bring it down in pieces, as you need it, at night. Looking around the internet, it seems like motors can be had for 90% efficiency and greater, so why hasn't someone built it?
    There are a couple of challenges with this approach. One is that typical motor efficiency is ~75%. Another is that electric motor efficiency varies with load, and lightly loaded motors are not particularly efficient. Then there's the problem with poor generator/alternator efficiency when converting the mechanical kinetic energy to electrical energy.

    I think Bill's got it right about "pump back" hydro plants: My recollection is that they're about 75% efficient.

    HTH,
    Jim / crewzer
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: ALTERNATIVE to batteries...?

    Problem with the weight and pully system is mechanical friction. Granted nowthing is 100% effecient but friction losses are huge.

    Another alternative is heat. Have your panels convert to heat, Heat massive quantites of water over the course of the day, give back the heat at night. Problem is how do you get electricity out of hot water unless you boil?

    You could also do cold if you wished.

    Icarus
  • System2System2 Posts: 6,290 admin
    Re: ALTERNATIVE to batteries...?

    Thanks, all, for the various ideas of energy storage.

    Compressed air I had not thought of. It will be interesting to see the actual engine when they enter mass production, how cost effective, etc.
    And the "pump-back" hydro plants, that sounds more like what the average person could construct, on a low budget. However, my reservations would be twofold...1)the vulnerability of having a storage tank elevated high enough to get a good "head", (low pressure/high flow vs. high pressure/low flow??) and 2)the inevitable maintenance involved with water systems. Perhaps the setup could have the upper tank at ground level, and the lower tank below ground?
    Handled properly, could this system also be the primary source for drinking water? Just throwing some ideas out there... I'm not looking to construct such a monster anytime soon.

    Icarus, I can only guess you're meaning losses in excess of 30% when you characterize friction losses as "huge" with a pulley and weight system. I was thinking more in the neighborhood of 10% or less. Could be wrong though...Combined with a motor efficiency of NLT 80% going in, and NLT 80% going out, this would be 72% (0.80x0.90) going in (storing), and 72% coming out, ending up around 52% (.72x.72=.5184). Probably not as good as the hydro setups out there, but may be better suited for some applications, where water may be a deciding factor. I say "Not Less Than" 80% because I don't expect I'd run a motor (either coming or going) at anytime except under full load. I may be speaking out of ignorance, also, about motor efficiencies, but I see some out there (on the 'net) that are over 90%. Most are over 1HP, though. And though a hydro setup may be preferable in most applications, you can't escape having an electric motor there to do the converting. So...as long as you're going to use them, the motor efficiency is really a moot point. It all boils down to whether you want your energy stored as water, a good chunk of concrete hanging from a cable, or maybe something else....?
  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: ALTERNATIVE to batteries...?

    I would guess the largest energy storage systems are they Hydro/pump stations. They are quite efficient and all it takes are dams and lakes for storage.

    The problem is really more environmental... Streams, rivers, and lakes and their native "life" have evolved over millions of years.

    Water levels that change dramatically, drawing colder water from below the surface, streams that don't experience normal seasonal flows, CO2 released from decaying vegetation cycled through dams/hydroelectric plants (if you are into CO2/global warming), dams, etc. have all added up to the tremendous impact that dams/hydro have on the environment.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: ALTERNATIVE to batteries...?

    it's not going to matter what you do to store energy as you will have efficiency losses no matter what and there are other factors with some you may not even think of, but for example on a hydro system there is much evaporation that takes place and the only way to get close to stopping that is a closed system. batteries are small and efficient comparing to other methods and a king's ransom isn't quite needed yet for them, although it's getting there quickly.
  • khottonkhotton Solar Expert Posts: 38
    Re: ALTERNATIVE to batteries...?

    Let me have a crack at this (please correct me if I am mistaken in what I write). Assume two "golf-cart" batteries wired in series (12V, 220Ah at 20hr discharge rate). This battery bank discharging at the 20hr rate would be 11A at 12V or 132W (.176 hp = 96.8 ft-lbf / s). To discharge the batteries to 50% DOD would imply a constant draw of 132W for 10hrs (36000-sec). If we suspended a 10000-lb weight (neglecting all inefficiency - 100% efficient) this weight would have to drop at a rate of 96.8/10000 = 0.00968 ft/s (0.11616 in/s) for 10hrs = 4182 in (348 ft !!!). Does not seem practical to use mechanical potential energy to replace battery chemical energy.

    Kevin
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: ALTERNATIVE to batteries...?

    Why would a "weight based" system, be inherently lossy? Pulleys and bearings can approach nearly frictionless, winching motors, set for a known load, using a high-E motor should be above 95%, and re-generation, from a dedicated generator, should be above 90%, coming close to the same 80% see by batteries. Of course, if your weight falls early, you are in trouble, but likewise, a battery bank has been know to "rapidly dissemble".
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: ALTERNATIVE to batteries...?

    Unfortunately, the collection and delivery cycles are not particularly stable. I believe that variable solar enegy to the motor and varying loads on the generator/alternator introduce considerable efficiency issues.

    This aricle in Wikipedia suggests pump-back hydro-electric systems are 70% to 85% efficienct: http://en.wikipedia.org/wiki/Pumped_storage_hydroelectricity I suspect the fairly constant load during pump back opertion contributes to this level of efficiency.

    HTH,
    Jim / crewzer
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: ALTERNATIVE to batteries...?
    khotton wrote: »
    Let me have a crack at this (please correct me if I am mistaken in what I write). Assume two "golf-cart" batteries wired in series (12V, 220Ah at 20hr discharge rate). This battery bank discharging at the 20hr rate would be 11A at 12V or 132W (.176 hp = 96.8 ft-lbf / s). To discharge the batteries to 50% DOD would imply a constant draw of 132W for 10hrs (36000-sec). If we suspended a 10000-lb weight (neglecting all inefficiency - 100% efficient) this weight would have to drop at a rate of 96.8/10000 = 0.00968 ft/s (0.11616 in/s) for 10hrs = 4182 in (348 ft !!!). Does not seem practical to use mechanical potential energy to replace battery chemical energy.

    Kevin

    I want to see the 10,000lbs wieght and the structure to hold it dropping 348 feet! I guess you could reduce the number of feet with multiple passes of line (more fricton loss however) Looks like something out of junkyard wars!
  • khottonkhotton Solar Expert Posts: 38
    Re: ALTERNATIVE to batteries...?

    If you reduce the drop height of the weight with a block-and-tackle arrangement, you will be reducing the power output into the generator. The weight must be dropping at the full 0.116 inch per second to produce 132W continuously.

    Kevin
  • System2System2 Posts: 6,290 admin
    Re: ALTERNATIVE to batteries...?

    Khotton,
    That WOULD be quite a structure, and, assuming your numbers are anywhere near close, a prohibitive set-up. I didn't realize the mechanical energy-to-electrical energy conversion (1.32KwH=3,480,000 ft/lbs) was on such a scale. The whole idea was to find an alternative to batteries for storing energy. Even if one took a stab by jacking the weight up x10, to reduce the height x10, it would STILL leave you with an unweildy 34' tall structure, and perhaps an eyesore for the neighbors...and that's if you could find the hardware to keep 100,000 lbs. from coming down on your head! All to store a measly couple of KWH's..??.. For now I think I'll stick with that huge AC battery called "the grid", and when the time comes to go offgrid, pay the piper's ransom for some good quality batteries~~
  • System2System2 Posts: 6,290 admin
    Re: ALTERNATIVE to batteries...?

    VERY informative site for water energy storage, Crewzer! Thanks~!

    http://en.wikipedia.org/wiki/Pumped_storage_hydroelectricity

    Yes... doesn't seem like lifting stuff is the way to go, unless you can lift a LOT of it!
  • bgarrettbgarrett Solar Expert Posts: 48
    Re: ALTERNATIVE to batteries...?

    It seems that super capacitors are the alternative to batteries. I have seen several articles lately that mention capacitors as storage units.
    --heres one

    http://www.fastcompany.com/magazine/120/motorhead-messiah.html

    When will we be able to use capacitors instead of batteries for solar systems?
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: ALTERNATIVE to batteries...?

    capacitors are not good batteries. caps cannot hold as much power as batteries can and they tend to leak current internally in varying degrees, but would be more over much shorter periods of time than a battery would. they are better electronic parts, but are not good enough as a means of power storage yet.
  • JamesJames Solar Expert Posts: 248 ✭✭
    Re: ALTERNATIVE to batteries...?

    I'm not a physics major, but I once heard there is no such thing as a free lunch.

    Energy conversion always comes at a cost (loss)...

    What is the most efficient?
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