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posted by janrinok on Saturday January 28 2023, @12:52AM   Printer-friendly
from the that's-heavy dept.

Scientists Propose Turning Abandoned Mines Into Super-Efficient Gravity Batteries:

As the world comes to terms with the realities of climate change, the pressure to adopt more renewable energy is unavoidable. However, the sun isn't always shining, and the wind isn't always blowing. Worst of all, our ability to store that energy for the cold, still nights is still woefully inadequate. There may be a solution, and it's not a fancy new technology—it's a new take on something decades old. A team from the International Institute for Applied Systems Analysis (IIASA) has developed a plan to create a network of super-efficient gravity batteries that could store tens of terawatt-hours of power.

Humanity has been harnessing small amounts of energy from gravity for centuries—technically, the pendulum clock is a primitive gravity battery. In the 20th century, scientists developed pumped-storage hydroelectricity, which uses elevated water reservoirs to store gravitational potential energy. Several of these facilities exist around the world now, but most areas don't have enough water or the right terrain to make it work. The IIASA proposal for Underground Gravity Energy Storage (UGES) would use something we already have in spades: abandoned mine shafts.

A UGES stores energy when it's plentiful—for example, when the sun is shining on a solar power plant. A heavy container of sand or rocks would be suspended in the previously abandoned mine shaft with an electric motor raising it to the top. As long as the bucket remains at the top of the shaft, the energy isn't going anywhere. When power generation drops, the grid can harvest power from the UGES by letting the vessel drop back down. The UGES would use regenerative brakes on the cabling, similar to the way electric cars extend their range when you apply the brakes. Unlike batteries, all of which lose power via self-discharge over long periods, sand always has the same mass, and we're not going to run out of gravity.


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  • (Score: 3, Funny) by Tork on Saturday January 28 2023, @01:03AM

    by Tork (3914) Subscriber Badge on Saturday January 28 2023, @01:03AM (#1289016)
    "Yo mama's so fat the streetlights in her hometown burn brighter!"
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  • (Score: 2) by optotronic on Saturday January 28 2023, @02:48AM (1 child)

    by optotronic (4285) on Saturday January 28 2023, @02:48AM (#1289026)

    This would be cool if it's practical. I don't know enough about mine shafts to know whether they're deep enough, straight enough, and large enough for this to make economic sense.

    • (Score: 3, Funny) by Anonymous Coward on Saturday January 28 2023, @03:03AM

      by Anonymous Coward on Saturday January 28 2023, @03:03AM (#1289029)

      Show me a piano falling down a mineshaft and I'll show you A-flat Minor.

  • (Score: 4, Informative) by Barenflimski on Saturday January 28 2023, @03:13AM (8 children)

    by Barenflimski (6836) on Saturday January 28 2023, @03:13AM (#1289030)

    I think its fairly clear that these scientists have never seen the inside of a mine.

    They're not a vacuum. They're straight, only in the most modern of modern, very few that are deep enough, mines.

    The reality is that mines follow the ore. You're typically following a slope of X degrees. The lucky miners found ore streaks less than vertical.

    I'm all for them proving this out without drilling new mine shafts.

    • (Score: 2, Insightful) by Anonymous Coward on Saturday January 28 2023, @03:31AM (2 children)

      by Anonymous Coward on Saturday January 28 2023, @03:31AM (#1289033)

      A deep mine I heard about did have a vertical shaft to get down to ore level...but it was very small, just big enough for the escape ladder. The main entrance to the mine was a spiral tunnel that was big enough for vehicles to drive in, the spiral surrounded that central shaft.

      • (Score: 2) by istartedi on Sunday January 29 2023, @01:44AM (1 child)

        by istartedi (123) on Sunday January 29 2023, @01:44AM (#1289145) Journal

        Anybody remember the Chilean mine rescue? It was a huge news story in 2010. The mine was a spiral [wikipedia.org] as you describe, with no central shaft AFAIK. Even though they had the spiral road in the mine, they couldn't get drilling equipment down there so they had to drill new shafts straight down to rescue the miners. All 33 got out but I'm sure there was some PTSD.

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        • (Score: 0) by Anonymous Coward on Sunday January 29 2023, @02:30AM

          by Anonymous Coward on Sunday January 29 2023, @02:30AM (#1289150)

          Continuing OT:

          Guessing the reason the US spiral mine had the central shaft with ladder was OSHA, or similar regulation. Sounds like Chile doesn't have that safety regulation?

          The mine I heard about (I'm the GP) was pretty deep, perhaps a mile (1.6km). While it might be reassuring to have the central escape route, I'm not sure that I'm able to climb that far on a ladder. I probably average 0.1 hp (75 watts) for a long time on a bicycle (some sort of average fitness for a boomer). If all the power went into lifting myself that would be 3300 ft-lbs/min. Over my weight of 180 lbs = 18.3 ft/min average. If there was 5000 feet to climb that would take nearly 300 minutes or 5 hours.

          Better carry some water, even if the extra weight will slow me down. Or, hope that rescuers drop a harness and hoist me out.

    • (Score: 3, Interesting) by khallow on Saturday January 28 2023, @04:36AM (2 children)

      by khallow (3766) Subscriber Badge on Saturday January 28 2023, @04:36AM (#1289038) Journal
      Seems like they'd have better luck with old rail cars loaded with said sand on a rail on the side of a moderately sloped hill.

      I'd say that the vast majority of those mines would be so unsafe, they couldn't be made into viable gravity storage. You'd probably have better luck digging your own holes.
      • (Score: 3, Funny) by acid andy on Saturday January 28 2023, @06:36AM

        by acid andy (1683) on Saturday January 28 2023, @06:36AM (#1289049) Homepage Journal

        You'd probably have better luck digging your own holes.

        ...with a solar powered digger while the sun in shining. Then you drop all the earth you dug out back into the hole (using the generation vessel) when it's dark and you've got your electricity supply! Repeat. :)

        --
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      • (Score: 3, Touché) by Runaway1956 on Saturday January 28 2023, @09:21AM

        by Runaway1956 (2926) Subscriber Badge on Saturday January 28 2023, @09:21AM (#1289059) Journal

        If only there were a substance which could be induced to fall in whichever direction we wanted . . . you know, kinda like water in pipes. Plumbers and pipefitters are all the time forcing water to flow whichever way they want it to flow. Alas, there is no such substance, so we'll have to wait for straight mines to evolve.

    • (Score: 2) by quietus on Saturday January 28 2023, @08:12AM

      by quietus (6328) on Saturday January 28 2023, @08:12AM (#1289054) Journal

      Just checked: the local, now abandoned, mine here had/has 2 straight shafts of 800+ meters deep, with a diameter of 5-6 meters. It has to be said though, in line with khallow's comment, that *maintaining* these shafts doesn't come for free. (These shafts were freeze-drilled i.e. the surrounding material was frozen, then cut away. What I can gather is that the shaft was maintained that way too: by keeping the surrounding meters frozen.)

    • (Score: 1, Funny) by Anonymous Coward on Sunday January 29 2023, @08:48AM

      by Anonymous Coward on Sunday January 29 2023, @08:48AM (#1289165)

      I think its fairly clear that these scientists have never seen the inside of a mine.

      Are they also assuming a spherical mass of sand? 😉

      Seriously, it should be obvious the amount of energy stored isn't going to be enough for anything other than niche purposes. After all, the mines don't need to use that much electricity[1] to lift tons of ore out.

      Maybe the scientists used ChatGPT for this proposal.

      [1] See also: https://www.omnicalculator.com/physics/potential-energy [omnicalculator.com]

  • (Score: 2, Interesting) by Anonymous Coward on Saturday January 28 2023, @10:54AM

    by Anonymous Coward on Saturday January 28 2023, @10:54AM (#1289063)

    Keeping the shafts pumped out will use a lot of energy.

  • (Score: 4, Informative) by fraxinus-tree on Saturday January 28 2023, @04:23PM (1 child)

    by fraxinus-tree (5590) on Saturday January 28 2023, @04:23PM (#1289087)

    Sorry to say it, but no elevator is 100% efficient. As a matter of fact, the elevator in the building I used to live some time ago ran the electricity meter in the same unpleasant direction no matter where it went and how much people were inside. But well, an industrial one could be made better - as far as I understand applied mechanics and EE - as much as 70% efficient in both directions. Expensive, but possible.

    Then, the scale:

    1000 metric tons of weigth? Show me your ropes/cables/chains/whatever. I won't ask about the spools. Maybe geared rails? But whatever, for a 1000m deep shaft this amounts to 2.2MWh stored. For a 10-hour night this amounts to 220 kW or about 200 energy-efficient homes. And a machine like this will need much more maintenance, compared to batteries.

    Won't do.

    • (Score: 4, Insightful) by VLM on Saturday January 28 2023, @04:32PM

      by VLM (445) Subscriber Badge on Saturday January 28 2023, @04:32PM (#1289088)

      Either profoundly naive or an investment scam

      Why not both? The above quote is corporate greenwashing in a nutshell. Its 2023, if its being advertised as green, its a scam by default.

      Another hilarity is most mines I'm aware of are not exactly in urban environments. Gonna have a lot of "fun" trying to run power cables 50 miles out into the middle of nowhere to store entire KWh of energy LOL.

      You can "back of the envelope" estimate a tenth of a MWh per electric car, so your mine is the equivalent of 20 e-cars backfeeding the grid. That's a "moderately large shopping center" around here, and the storage is mere feet away from the demand.

      People already pay for chargers to charge, so the cultural dynamics of still paying to charge but now it sometimes discharges or similar nonsense might be tricky, also batteries have a limited cycle life and incredibly high cost leading to each cycle costing a lot. But, maybe if they skimmed 1% off of 100 cars, nobody would notice...

      Another hilarious engineering comparison is again to about one sig fig a MWh of gas is about thirty gallons, at least thermally. Figure you'd have to burn 100 gals to generate an electrical MWh at the outlet. So the entire rube goldberg contraption in the middle of nowhere is equivalent to only 220 gals of gas. The capex of installing power lines to the mine, and the environmental impact of installing and maintaining those lines, would exceed just burning gas in a generator every night.

  • (Score: 5, Informative) by istartedi on Saturday January 28 2023, @07:19PM (1 child)

    by istartedi (123) on Saturday January 28 2023, @07:19PM (#1289109) Journal

    I always thought it would be cool to build something like that if I were out in the middle of nowhere and living off the grid. I ran the calcs at some point, and it came out quite impractical even with a fairly tall tower. We kind of get fooled in to thinking it could do something because the old grandfather clocks used weights; but time-keeping is a surprisingly low energy application. Even with high efficiency LED lights, you soon find yourself hefting some fairly heavy weight for a fairly short burn time, and forget about the fridge, the washing machine, or a heater.

    I think a big mine shaft might actually work well--for one or possibly two houses.

    Yes, pumped storage works but that's because dams are holding back a huge *volume*. That's the key word there. Volume. Even though you're using something much more dense as your weight in a mine shaft, you can't match the volume of a decently sized reservoir, and that density advantage gets washed out by the numbers fairly quickly.

    I'm not going to bother re-running the calcs. I've been down this road, and I'm pretty sure it's going nowhere.

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    • (Score: 2) by Reziac on Sunday January 29 2023, @02:49AM

      by Reziac (2489) on Sunday January 29 2023, @02:49AM (#1289153) Homepage

      Nonsense. Such a scheme is perfectly practical, so long as it's powered by the flow of venture capital or government subsidies. Problem solved!

      --
      And there is no Alkibiades to come back and save us from ourselves.
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