"Long" term energy storage?

audredger
audredger Solar Expert Posts: 272 ✭✭
in Off Grid Solar & Battery Systems #1
It's beginning to be that time again, two weeks ago I ran the generator every day, yesterday at 2:00pm the charge controllers said "Bat Full". With the "bad" weather comming it tomarrow (rain & snow mix, not 30" of snow, sorry east coast) I may not feel so smug.

The Question: How can we ( I ) store the excess power my system generates in the summer for use in the winter?

Super/ultra capacitors: still to expensive

Pumping water & small hydro: at $1.00 a gallon for storage tanks = too expensive too quick. Digging a lake is out too! And, with only 20" of rain a year, I need all that I can capture off the roof to drink.

Fuel Cell & Hydrogen: How to pump Hydrogen & how to store? Metal hydride tanks get real expensive real quick!

Grid Tie: = 187 year pay back. Yea right! LOL

Your solution?
Mike
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Comments

  • bryanl
    bryanl Solar Expert Posts: 175 ✭✭✭✭✭
    #2
    Re: "Long" term energy storage?

    You solve this one and you'll find the holy grail.

    Energy storage is the real reason why many 'alternative' energy sources are not feasible replacements for traditional sources. Power is one thing and energy is another. The fundamental problem is storing energy so it is available when you need it.

    The economy of scale has been the only means a 6 month energy storage of household consumption size or bigger has been feasible. That includes nuclear, hydroelectric, or fossil fuels.

    When you restrict your methods to regenerative forms, the field of options narrows considerably. Entropy is difficult and expensive to reduce and it leaks. Trapping it for months in something as non-stable as to be inexpensive or easy to regenerate is pushing at both sides of the compromise.
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #3
    Re: "Long" term energy storage?

    When it rains and snows, it there lots of wind? If so, get a wind turbine. Problem is, current off-the-shelf small wind turbines are not good enough and too expensive (my opinion). To aquire one cheaply, you have to build it yourself. But most of plans, online and for sale, to build one are junk as well. Except plans on otherpower website maybe.

    But the kind of seasonal electrical energy storage is not going to happen anytime soon. Unless you have $ 1 million to spend on batteries.

    So, adjust your electricity usage according to available resources.
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #4
    Re: "Long" term energy storage?

    Maybe if you could use the excess energy to wind up a giant spring, you could let the spring unwind when you needed the power. Another idea = What if you used the theory that is used on grandfather clocks. You could get some weights and use an electric winch to raise them with excess power and let the weights lower to supply a small generator. Figure with the bad weather we ae havivg everyone needs a laugh. Vic
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #5
    Re: "Long" term energy storage?
    solarvic wrote: »
    Another idea = What if you used the theory that is used on grandfather clocks. You could get some weights and use an electric winch to raise them with excess power and let the weights lower to supply a small generator.

    I have got to be a total nerd to have to calculate this. Assuming no losses, 32000 pound weight at 100 feet has same potential energy as 100Ah 12V battery.
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  • GreenerPower
    GreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    #6
    Re: "Long" term energy storage?
    bryanl wrote: »
    You solve this one and you'll find the holy grail
    How about using the excess energy to re-align some di-lithium crystals ... and that could be converted to any form of energy later ... Oops ! are we still in the 21st century ?
    GP
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Re: "Long" term energy storage?
    AntronX wrote: »
    I have got to be a total nerd to have to calculate this. Assuming no losses, 32000 pound weight at 100 feet has same potential energy as 100Ah 12V battery.

    Using a handy-dandy random power conversion calculator:
    • 32,000lbs * 100' * 1 hour = 1,205.171509626 watt*hours
    • 100 AH * 12 volts = 1,200 Watt*Hours
    OK--being silly with the decimal places on the right--gives you a good idea of how difficult it is to store mechanical energy.

    -Bill "To the caves, and beyond!" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ajbelcher
    ajbelcher Solar Expert Posts: 27 ✭✭
    #8
    Re: "Long" term energy storage?
    AntronX wrote: »
    I have got to be a total nerd to have to calculate this. Assuming no losses, 32000 pound weight at 100 feet has same potential energy as 100Ah 12V battery.

    Problem Solved - buy 32000 lbs of battery and a hoist - and you've got hybrid storage

    lol
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #9
    Re: "Long" term energy storage?
    BB. wrote: »
    Using a handy-dandy random power conversion calculator:

    Hey sir , not fair! I had to go look for Physics tutorial to figure this out the hard way. I wish I paid more attention in class!
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  • audredger
    audredger Solar Expert Posts: 272 ✭✭
    #10
    Re: "Long" term energy storage?

    "re-align some di-lithium crystals" even William Shatner can't aford them!

    batteries are not a good long term storage either

    Yes Bill, thats a lota granddfather clocks

    Really now, dosent it bother the tar out of you to see "Bat Full" and know there is another 3,000 watts just begging to be harvested?

    I know that when you change energy forms (electric to hydrogen and back) the overall efficiency's are the pits but "another 3,000 watts just begging to be harvested"

    Mike
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #11
    Re: "Long" term energy storage?
    audredger wrote: »
    Really now, dosent it bother the tar out of you to see "Bat Full" and know there is another 3,000 watts just begging to be harvested?Mike

    You can divert this excess energy to heat water for washing or if you have enough of excess, for space heating. I wonder how efficient it would be to store energy in large, extremely well insulated and buried under ground hot water tanks for space heating in the winter with excess summer energy? Then when water temperature equalizes with living space air temperature, a heat pump wound suck all remaining thermal energy up to the point of freezing. The holding tanks would have to be expandable or elastic, to allow water to expand when it turns to ice.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #12
    Re: "Long" term energy storage?

    Load shifting helps, I'm off grid so I run heater on the composting toilet, even have a 600 watt oil heater in the house/cabin in the winter and run an AC in the summer. Hate topping off at 11 and wasting power the rest of the day. I also bake bread on sunny days this winter, I'm storing all sorts of energy around my belly!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #13
    Re: "Long" term energy storage?
    Photowhit wrote: »
    Hate topping off at 11 and wasting power the rest of the day. I also bake bread on sunny days this winter, I'm storing all sorts of energy around my belly!

    Haha, I do something similar. I make tea using 600W coffee maker. It makes 2 cups of tea using only 50 Wh of energy. I usually turn it on when solar panels output about 400 - 440W with the rest coming from the battery. Today I had a record solar harvest of 2.5 KWh from 520W of panels. My batteries were absorbing by 11am, so excess power went to dump load.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #14
    Re: "Long" term energy storage?
    AntronX wrote: »
    Hey sir , not fair! I had to go look for Physics tutorial to figure this out the hard way. I wish I paid more attention in class!

    Well, there is the old math/physics of unit conversion equations--find something you "know" the diffinition of and start unit converting:

    1 horsepower = 550 foot-pounds/second
    1 horsepower = 33,000 foot-pounds/minute
    1 horsepower = 42.44 Btu/minute
    1 horsepower = .7456999 * kilowatts

    1 foot = 0.3048 Meters
    1 pound = 4.44822162825 Newtons
    1 kilogram = 1000 gram = 9.80665002864 Newtons
    g = 9.812865328 m/s^2
    1 Watt = 3.413 BTU/h
    1W = 1Js^-1 = 1kgm^2s^-3 = 1Nms^-1

    Let's see--I think there is enough there for you to write the conversion equation in several variants...

    Or--there is Google...

    -Bill :-)
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • audredger
    audredger Solar Expert Posts: 272 ✭✭
    #15
    Re: "Long" term energy storage?

    Photowhit: I too have excess energy around the middle. Doesen't run the lights though.

    AntronX: I'm a yank; make coffee; only a pommy would make tea. LOL Now if we could turn watts into 12 year old single malt we all might be happy.
    Mike
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #16
    Re: "Long" term energy storage?

    A fairly nice small load shift/diversion is a propane fridge heating element. I have set mine up so that when the controller begins to dial down, it turns on the fridge element, reducing the need for LP. In my case, I am just on the threshold of having this make much sense, since my PV is ~400 watts, and the heating element is 350 watts. Additionally since the fridge runs intermittently, the timing is pretty sketchy. If I manually lower the t-stat temp of the fridge at ~noon the fridge can use the power, but I have to remember to turn it back up or things freeze. The reality is that it doesn't save enough LP to make it worth the effort. A bit more fine tuning and maybe it will be.

    Tony
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  • GreenerPower
    GreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    #17
    Re: "Long" term energy storage?
    BB. wrote: »
    Well, there is the old math/physics of unit conversion equations--find something you "know" the diffinition of and start unit converting:

    1 horsepower = 550 foot-pounds/second
    1 horsepower = 33,000 foot-pounds/minute
    1 horsepower = 42.44 Btu/minute
    1 horsepower = .7456999 * kilowatts

    1 foot = 0.3048 Meters
    1 pound = 4.44822162825 Newtons
    1 kilogram = 1000 gram = 9.80665002864 Newtons
    g = 9.812865328 m/s^2
    1 Watt = 3.413 BTU/h
    1W = 1Js^-1 = 1kgm^2s^-3 = 1Nms^-1

    Let's see--I think there is enough there for you to write the conversion equation in several variants...

    Or--there is Google...

    -Bill :-)
    A little bit simpler if going the "basic SI units" route :-)
    1 watt = 1 kg·m^2/s^3
    1 hour = 3600 s
    1 lb-foot = 1.355 817 948 331 4004 kg·m^2/s^2

    1200 Watt-Hrs = ??? lbs-foot

    GP
    (edit to correct: should have been lbs-foot only, energy dimension, instead of lb-ft-hr.
    Same energy, it doesn't matter whether it takes 1hr or 1sec to move 32000lbs 100 ft)
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #18
    Re: "Long" term energy storage?

    Maybe a thermoelectric cooler (summer) or heater (winter) is a good surplus load.
    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 ,

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  • dsp3930
    dsp3930 Solar Expert Posts: 66 ✭✭✭✭
    #19
    Re: "Long" term energy storage?

    Smart Energy 25 / Flywheel storage @ 16k RPM?
    I have no clue how much these are ($$$$$) or how well they would work for offgrid: http://www.beaconpower.com/products/smart-energy-25.asp
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #20
    Re: "Long" term energy storage?

    Thermo Electric Coolers/Heaters are pretty energy inefficient... A good heat pump would be way more effective.

    Regarding Beacon Flywheels--We did talk about that in this thread 2 years ago:

    Flywheel based electrical storage

    Appears to be OK for large scale wind farms with highly varying production. And sometimes used as a UPS for line fail to Generator support (15 second type power support).

    For home solar--probably not so much.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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