Gravity energy storage

Preface. This is interesting, but not commercial. And as my book “When trucks stop running” explains, trucks are the basis of civilization, and can’t run on electric batteries or overhead wires. Even if they could, I explained why a 100% renewable energy grid was impossible, especially because you need 30 days of storage to ride out seasonal shortages of wind and solar. And even if I were wrong, oil decline is likely to begin with 10 years, so we’ll be stuck with whatever solutions are commercial at the time.



Deign, J. 2019. Energy vault funding breathes life into gravity storage.

The speculative field of gravity-based energy storage got a boost recently with news of a strategic investment and new patents.

Swiss-U.S. startup Energy Vault, one of the most high-profile gravity storage players to date, secured financial backing from Cemex Ventures, the corporate venture capital unit of the world’s second-largest building materials giant, and a pledge to help with deployment through Cemex’s “strategic network.”

Meanwhile, the University of Nottingham and the World Society of Sustainable Energy Technologies confirmed the filing of patent applications for a concept called EarthPumpStore, which uses abandoned mines as gravity storage assets.

Implementing the technology across 150,000 disused open-cast mines in China alone could deliver an estimated storage capacity of 250 terawatt-hours , the University of Nottingham said in a press note.

MY NOTE: well whoop-dee-doo. China generates 16.2 trillion terawatt-hours (TWh) a day. That’s 64 billion times more than all of the open-cast mines can provide. Better start digging more holes!

The announcements indicate growing interest in a class of energy storage concepts that appear seductively simple but have yet to gain widespread acceptance.

Most gravity storage concepts are based on the idea of using spare electricity to lift a heavy block, so the energy can be recovered when needed by letting the weight drop down again.

In the case of Energy Vault, the blocks are made of concrete and are lifted up by cranes 33 stories high. EarthPumpStore, meanwhile, envisages pulling containers filled with compacted earth up the sides of open-cast mines.

Gravity is also the force underpinning pumped hydro, the most widespread and cost-effective form of energy storage in the world. But pumped hydro development is slow and costly, requiring sites with specific topographical characteristics and often involving significant permitting hurdles.

The proponents of newer gravity storage options claim that installation and deployment of their technology is quicker, easier and cheaper.

The University of Nottingham, for example, estimates EarthPumpStore would cost about $50 per installed kilowatt-hour, compared to $200 for pumped hydro and $400 for battery storage.

The university also said EarthPumpStore could achieve a round-trip efficiency of more than 90 percent, compared to between 50 percent and 70 percent for pumped hydro, plus an energy storage density up to eight times higher. Other sources have made similar claims. 

In 2017, for example, a study by Imperial College London for the gravity storage technology developer Heindl Energy concluded that Heindl’s concept could achieve a levelized cost of storage of $148 per megawatt-hour, compared to $206 for pumped hydro.

“Based on the given data, gravity storage is most cost-efficient for bulk electricity storage, followed by pumped hydro and compressed air energy storage,” the research concluded. 

Given gravity storage’s apparent simplicity and cost-effectiveness, it is curious that the concept hasn’t taken off. One of the first companies to emerge with a gravity-based idea was Advanced Rail Energy Storage (ARES), a Santa Barbara-based firm that was founded in 2010.

ARES plans to hoist railcar-based weights up a hillside, and in 2016 finally got U.S. Bureau of Land Management approval for a proposed 50-megawatt, 12.5-megawatt-hour project in Nevada. At the time, ARES was expecting the project to be up and running in early 2019.

However, as of last August the company was still securing permits and pushed its go-live date back to 2020. Other gravity storage hopefuls seem to be making equally slow progress, although last year saw two U.K. companies getting funding.

Energy SRS, a collaboration of five U.K. firms and the University of Bristol, got £727,000 (about $922,000 at today’s exchange rate) from the government research and innovation body Innovate U.K.

The funding was for a prototype, which Energy SRS is hoping to scale up by 2020. Meanwhile, another startup, Gravitricity, got a separate Innovate U.K. grant, of £650,000 ($824,000 today), to build a 250-kilowatt prototype of its mineshaft-based gravity concept.

Gravitricity is also aiming for full-scale implementation next year.

Daniel Finn-Foley, principal analyst at Wood Mackenzie Power & Renewables, said concerns over the safety, scalability and round-trip efficiency of lithium-ion batteries could lead to growing interest in alternatives such as gravity storage.

“It could be a key technology in the long term as states continue to mandate carbon-free energy,” he said. “I doubt the 100 percent vision will be solved by dropping lithium-ion batteries everywhere, so seeing new technologies emerge will be key.”

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9 Responses to Gravity energy storage

  1. jeorge says:

    The desperation is setting in eh? What’s next, floating paddle board generators covering every tributary?

  2. NJF says:

    “China generates 16.2 trillion terawatt-hours (TWh) a day.”

    More in the range of 6 TWh a year.

    A good rule of thumb is the average person in a developed country uses 3-5 MWh a year.

    • The 3 – 5 MWh/year per person is not too far off but: 4,000,000 Wh*1,400,000,000 people is 5.6*10^15 Wh/year for China. (5.6*10^15 Wh/year)/(365.25 days/year)=1.53*10^13 Wh/day, or 1.53 terawatt hours/day. She is off by a factor of a trillion, you are off by a factor of about a thousand. So I guess you win. In her defense though, taking her 64 billion times 250 TWh is about right.

      • NJF says:

        I just copied that figure from the website. Should have ran them myself.

        Also you forgot to move the decimal place for Terrawatt hours. 15.3 TWh not 1.53.

  3. The “trillion of terawatts” per day claim is indeed incorrect. But it might as well be correct because it will take trillions of watts of energy to build the system in those 10s of thousands of open pit mines, and even then, those systems will only store the energy. There’s no mention of where the energy will be generated that will then be stored in the gravity storage facilities. And, never forget, delta E = q – w . There is always a big energy loss when it goes from the solar panel, to the wire, to the motor pulling the heavy thing up the side of the mine, to then be reconverted into electricty again, and then sent to the ultimate user, who then runs a vacuum cleaner where most of the energy is lost as waste heat ….

  4. EnterpriseSpaceShip says: are off by a factor of about a thousand. So I guess you win..

    Also you [too] forgot to move the decimal place for Terrawatt hours. 15.3 TWh not 1.53.


    Humans became so saturated with fossil fuels supplies, decimals, units and orders of magnitude – no longer matter…

    Whether Gravity Storage is an energy sink more than hydrogen or more than reflective mirrors in space – no longer matter…

    What humans burn of fossil fuels daily and how that impacts their continuity – has become unfathomable, anyway…

    Hollywood needed not to create an image of Russians, Arabs and other oil-rich nations as greedy, selfish and good for nothing, but leaving them to their natural senses, pricing their finite fossil fuels – freely.

    Look what is happening now after removing in humans that natural sense of scarcity – nobody understands what is going on…

    Bravo Steve Aldrich.

    Viva fossil fuels!

    Hollywood wins. Humanity lost.

    • NJF says:

      It matters in the sense that it can subtract legitimacy from an argument.

      But even the right numbers are staggering. Gravitational-based power is rounding error compared to chemical energy. Nuclear energy is staggering in density and is definitely the best zero-carbon energy source, but the actual availability of fissile substances is extremely low, almost the lowest of any element in the crust. Plus they’re only good for power plants, and do little to none to substitute transportation applications or petrochemical production.

  5. Holleyman says:

    Next we implement peace on earth and everyone can use Gooble Boxes to generate electricity

  6. Red says:

    FF addiction is terminal. Quick back of the envelope stuff. One barrel of oil equals 22,000 human hours of labour approx. 98 million barrels per day times 22,000 = 1.98 trillion hours divided by 8 billion people is drum roll please 247 hrs per day per person. Take away the oil we’re going to need a few more bodies to do the work daily. Feel free to tighten the numbers. See if you can get it down to a 12 hour work day for every body on the planet.