Companies Have New Take On Old Energy Storage Tech

According to Spectrum, several companies are poised to make a splash storing energy with gravity. That sounds fancy and high tech at first, but is it, really? Sure, we usually think of energy storage as some sort of battery, but there are many energy storage systems that use water falling, for example, which is almost what this new technology is all about. Almost, since instead of water these new systems move around multi-ton blocks.

The idea itself is nothing new. You probably learned in high school that you have kinetic energy when a rock rolls down a hill, but a rock sitting on a mountain immobile has potential energy. These systems use the same idea. Moving the “rock” up stores energy and letting it fall releases the same energy. The big difference between the systems is what “up” means.

For Swiss company Energy Vault, the 35 metric ton bricks rise into the air manipulated by towers that look like alien construction cranes. To store energy, the crane builds a tower of bricks around itself. When the bricks return to the ground, they form a lower ring around the tower.

Another company, Scotland-based Gravitricity, uses weights up to 5,000 metric tons and moves them up and down very deep mine shafts, an approach shared by several other companies in this field. Some of the systems use the mechanical motion of the weight falling while others use the weight as a piston to drive water through a pretty ordinary generator.

Why not use batteries? According to the post, Energy Vault claims that blocks made of dirt, waste, and polymer are environmentally friendly compared to batteries. The blocks don’t wear out much, either, so operating costs are low since there’s not much to replace frequently as is the case of batteries.

The scale of the weights is hard to imagine. Another company, Gravity Power, claims they could deliver 400 megawatts for 16 hours using an 8 million metric ton piston. There’s no word on how long it takes to bring that piston back to the charged position after the 16 hours, though. A Boeing 757-200, for example, weighs about 100 tons when loaded with fuel and passengers. So imagine 80,000 giant airplanes melted down. It makes Energy Vault’s 35-ton weights seem much more reasonable.

Keep in mind, these systems don’t generate electricity. They store it, so there will be some loss. However, the principle of these is straightforward, the only complication is the scale. We wondered if anyone has used some sort of system like this on a small scale on a project that would have normally used rechargeable batteries? Sounds like a weekend project and if you do it, be sure to let us know.

118 thoughts on “Companies Have New Take On Old Energy Storage Tech

    1. The “trick” with this kind of systems is to use “cheap electricity” (very late at night or very early in the morning, or weekends, eolic, etc) to store energy (to lift the blocks in this case) and to use that stored energy at other times to feed the electric grid during “peak hours”. And the efficiency is never 100 %. There are also hidden costs, maintenance, cost of capital, etc.

      Best regards,

      A/P Daniel F. Larrosa
      Montevideo – Uruguay

        1. I like that description, its quite true as to why companies are investing in it…
          Not the way I’d ever thought about it.

          I’ve always preferred to think about it as if we were just being practical, with all the renewable coming online there is always going to be times with serious excess power on the grid – heck folks have been paid to charge their EV’s to help balance the grid, because its cheaper to pay them pittance than change output state on the big power stations or build these structures (in the short term at least)…

      1. As an aside, your example is on its way to being dated. In many places already, daytime electricity is cheaper. In fact, California has had to pay other states to take it at times. The need to store the excess solar power generated during the day for use in the night is part of what is driving the current energy storage boom.

    2. You’re correct, and that’s the goal.

      One big problem with the current power grid is that we have to use power as it’s generated, and have to generate power when it’s needed.

      It would be more efficient to run the generation systems at a constant level (for fueled systems) or at full capacity when generation is easiest (for solar and wind) and store the excess power that isn’t used immediately. Then when demand exceeds the immediate generation capacity, you release enough of the stored energy to make up the difference.

      With that kind of system, a large number of small generation-and-storage units would be able to cover the surge demand.

      1. I’m no expert in this field, but seems like a very inefficient system, that would rely on a huge surplus during low demand times. Converting electricity, to mechanical loses a lot of energy. Converting back, will lose some too. There is a time factor too. I would think that the weights would need to fall faster, or at least at a more regular rate, than it took to lift them. Take a lot longer to lift them, than to use up any stored energy. But, like wind and solar, it’s better than nothing, and saving the planet from becoming a scorched wasteland.

        1. You have to take into account that todays grids have to dissipate energy that’s not used, ie. you have produced more energy than what the demand is. One common solution is just to convert the excess energy to thermal energy (in essence a large resistor-bank “burning” it off).

          If you instead of just burning off that energy can store it, albeit a bit inefficiently but economically viable it’s a win.

          There are several problems with regulating a grid which I won’t go into, but it all boils down to latencies in how the energy is generated which can mean that to compensate for those latencies you change the frequency of the generated current which in turn affects the power-factor and these days a lot of producers are contractually obliged to provide electricity within strict limits. Another thing to consider is that if the power-factor deviates from the optimal you loose capacity in the grid.

          This also why for example battery-storage is looked on favorably since it can react incredible fast to supply/demand in comparison to traditional generation.

          1. another complication is rectifier-capacitor power supply waveform distortion, it can get very dramatic when you have a whole school full of computers using only the peaks of the sine wave. now multiply that up to an entire region and things get mmmmmm. Interesting.

          2. >that todays grids have to dissipate energy that’s not used,

            No they don’t.

            Some grids have emergency dump loads, but normally they just throttle down.

          1. mechanical storage is probably better in term of loss (better conversion and very low friction loss).
            On the other hand it’s very hard to beat hydro storage in term of capacity.
            So in the end, not one-fits-all situation, both system have their use.

          2. That would be an ideal solution in California. Winter precipitation is no longer being stored as snow for as long each year so it would be very useful to be able to store what’s now falling as rain instead of snow at higher elevations for use later.

            The same structure – pairs of high and low elevation reservoirs up and down the eastern mountains – could be used to store electricity as well. Two birds, one stone, etc.

        2. While the loss in KW/h sounds enormous because the total energy throughput is mind boggling the actual efficiencies of such systems are all well above 75% even exceeding 90% isn’t unusual. Many of them are vastly more energy efficient than chemical batteries, even more so when you consider the maintenance requirements.

          And its far better capture for reuse than just waste it.

        3. You mentioned solar, that’s one of the key parts of these types of storage systems. Use some solar generation capacity to power the storage banks during the day. That energy can be released back into the grid at night when solar doesn’t produce anything.

    3. >> If I drop a 100 lb. weight, and that generates say 100 (Joules) Wont I need 100J to pick it back up?

      Yes, of course you will. In fact, due to conversion losses you’ll need even more.

      But all energy is not created equally, especially when your’e talking about electricity.

      Electricity on the grid is a use-it-or-lose-it proposition. Some electricity is valuable, like power that’s available at 6PM on a weekday when everyone gets home, starts dinner, and turns on their A/C. Some is simply wasted, like electricity that is created at 3AM when all the cars are charged back up, everybody is asleep and almost nothing is using it

      But even at 3AM, there are sources that you can’t really turn off, especially in the era of renewables. There’s still water flowing through hydro dams, even if you shut the turbines off, you’ve still got to keep some minimum flow for river navigation. There’s still wind flowing past the big wind turbines, even if you feather the blades for the night. There’s photoelectric panels that still generate voltage at noon on Sunday, when demand is waaaay down.

      I’m gonna imagine that a nuclear plant could run hard overnight and the incremental cost of generating that power over just percolating along is probably pretty low.

      The idea behind gravity storage is to make a BIG battery, one that can be charged up on cheap, off-peak power that you might have thrown away anyhow, then return that power to the grid when you need it, like early on a weekcday morning when everybody is getting up and cooking breakfast but the sun isn’t high over the solar panels yet.

      The ability to store a little power for later goes a long way to curing one of the biggest problems with the traditional electrical system, the fact that we had to build plants with enough capacity to generate the full peak-load power that would ever be needed, even though you’d only actually use that much power for a few hours a day.

      If you have a little buffer, you can get by with a much smaller – but more efficiently scheduled – generating infrastructure, which is where the real cost is going to be. After all, stacking rocks is cheap compared to spinning another gas turbine.

      1. > one of the biggest problems with the traditional electrical system

        That is not a problem because we needed the spare capacity anyways, for maintenance scheduling and redundancy.

        The real problem in the grid is that we need power plants which can change output rapidly, which means we also need to have a fleet of simple once-through gas turbines and even massive diesel engines on standby.

        Whenever the grid load is expected to drop, all the large and cheap generators start backing out early and the expensive fast power plants turn on, so they can respond to the load variation. Likewise when the grid load is going up, the diesel engines start up and the other generators follow behind. When the supply and demand situation is switching around constantly and rapidly – such as when you have a bunch of wind turbines and solar panels on the grid messing it up – that’s all you’re using. The fast gas turbines and diesels are on all the time, ramping up and down, and the cheap baseload from nuclear, CCGT, even traditional run-of-the-river hydroelectricity have to back off out of the grid when there’s not a long enough stable period for them to operate.

        The further issue is that renewable generators output energy in big surges, such as making half the energy output for the entire week in one day like wind generators, so the real customer for any sort of battery is to smooth this variation so you could actually use the energy for something instead of just crashing the spot market prices every time due to oversupply.

      2. Perhaps the best solution is to pass through the surplus (and its very low cost) to the customers, so they can invest in making good use of it? Most likely thermal storage will be the most economical storage technology for residential, even though it will only handle the large thermal loads like HVAC and hot water.

        1. >so they can invest in making good use of it?

          Texas does this. They offer customers free surplus wind power at night, which the people use mainly to heat pools and have parties, because there’s really no use for it. The point of the scheme is that the federal government pays subsidies for every kWh produced, so the state earns money by wasting electricity.

        2. That would be great, I would build a giant heat reservoir in my back yard with rocks, water and electric heaters, then use that heat during the day to heat the house, rather than running a gas furnace.

          1. I’d probably want to just bury heating elements under the house and heat up the ground beneath. Makes me scowl when I see -2 cents a kW/h instantaneous market pricing (Yeah that’s negative two cents) throughout the night between 12 and 6, and my “time of use” prices still want 8 cents for it. Drive out in the sticks at that hour though and you see plenty of brightly lit greenhouses, so they’re giving someone a deal.

      3. Just some random links:

        * Load following power plant: this (german) page has a nice table how fast certain plant types can adapt to load:

        * for the European grid you can see the net frequency at The interesting point is that you can see the “swing” of usage and the turning on/off of fast power plants. The two lines at 50 Hz are the limits within the value should stay. If it crosses the line, “Primärregelleistung” (primary operating reserve) is added/removed. In theory it could be more messy at 00 and a bit less messy at 15/30/45 minutes due to expiring selling/buying contracts and therefor plants turning off or on.

        * again, Europe. Swissgrid has a nice live data collection at

        * EIA has some nice real time data for the US.

        * We (again, Europeans) have an ongoing discussion about building “immersion heater plant” to create hot water from surplus energy. There exist some “gigant immersion heaters” for used in emergencies.

        * “Trimet Aluminium” is one of the larges aluminum producers in the EU, specially Germany. In total it needs about 1% of the energy produced in Germany at any moment. So this gives two sides: first their load is sometimes used to regulate the power production by turning plants on/off. Second, if Trimet has an emergency problem and fast drops off some plants, there need to be some very quick solutions. “gigant immersion heaters” here you go. Shouldn’t be much different all around the world, of course.

        * And for todays crisis:

    4. Yes, that is correct more “energy” will be needed.

      The trick is for using “excess” energy to lift the weights (or to pump the water up …), “energy” otherwise wasted if there is no consumption.
      Excess energy sourced from solar panels during sunny days, wind generators during windy days, tidal generators at low tides and so on. When it is plentiful of production.

      it is just to store or accumulate energy for further use when little or none is produced.

    5. Actually it takes a bit more to lift it back up. Ultimately, the value is having green energy all the time rather than just when the wind is blowing or the sun is shining, for example.

    6. If you use will it high up in huge containers.gravity creates the energy on the way down.the water gets released in large areas heated by solar or moved by solar back up into large containers.= no energy lost at all.only gained

    1. The debunker compares gravity storage to pumped water storage which requires a mountain to operate. Most mountain energy storage systems do not need to pump the water “up” because rain is free. More important most (convenient) places you can put hydroelectric dams are already in use.

      I could make a video debunking a pumped water storage for the Great Plains by just calculating the cost of constructing the mountain required. How much would it cost to build a Rocky Mountain in Kansas?

      If you need energy storage in the middle of most of the world’s continents you have to build it on a flat ground. So you have to compare gravity storage to lithium batteries or flywheels or pumped air cylinders. On that basis gravity batteries are a pretty good choice.

      Maybe we could make gravity blocks out of the mountains of mine tailings discarded from the enormous mines we need to get all the lithium we need for batteries.

    2. Um, but your debunking video doesn’t really dubunk the idea.

      I actually like Thinderf00ts channel, he’s good at calling shenanigans, and I think his analysis are usually correct, but if you watch the video carefully, he’s not dragging on gravity storage as an idea, he’s saying that the multi-crane block stacking implementation makes no sense.

      As Thunderf00t points out, gravity storage is a real thing that actually works every day in the real world, you just have to do it well.

      To make gravity storage practical you need three things…

      1) a cheap, dense, easy to handle storage media (this keeps the system compact and capital light)

      2) height (this gives you more energy storage per piece handled)

      3) a simple handling strategy (easy handling improves efficiency)

      Most existing systems use water, because water is cheap, and pumps and pipes have few moving parts, but there’s nothing about water that’s magical. It’s just a good medium to make yourself a big pile of gravity.

      Thunderf00t analyzes a complex hammerhead crane system stacking and unstacking truck-sized blocks of concrete. There are height limitations, and handling overhead that cuts into the efficiency of the system.

      Buuuuttt…. a system that uses a few giant weights, lifted by relatively simple fixed winches might have entirely different numbers. True, you have the fixed cost of digging a deep shaft, but once you amortize that cost, you can use that literal gravity well free for years

      1. >he’s saying that the multi-crane block stacking implementation makes no sense.

        Yeah, but that’s the point. The Energy Vault company is either an investment scam or someone’s delusion that enough people took seriously to generate this hype. It won’t work for the reasons mentioned.

        In general, nothing about lifting masses to store energy is false per se, it’s just that the energy density is ridiculously low and the implementations turn out to be much noise for almost nothing, if they have a practical chance of working in the first place.

        Most of the ideas are also relying on mechanisms which in practice would wear out or break much too soon and cost a billion to keep up, such as laying train tracks along a mountainside and driving an electric train up and down – or indeed the construction crane concept. The most viable gravity storage concept is hydroelectric pumping, and even that suffers from certain practical concerns like the danger of flooding up entire counties, or needing a mountain to carve up into an elevated reservoir.

      2. buuuuttt the biggest buuuuttt is that concrete is bloody expensive.(and digging holes too).
        whereas water literally drops from the sky after which you can collect it.
        with normal concrete prices the cost per kwh capacity will be higher than most other storage systems even if the rest of the system works maintenance free and is relatively inexpensive (which i doubt)

        1. there a re two things missing from your but: first: if you have mountains, no need for this setup. only on a flat landscape this makes sense. second: only the block walls need to bee made of concrete, the filling can be rubble.

          1. if you do that you have to uncrwease reinforcements. concrete doesn’t have a lot of tensile strength. All in all it will be a LOT more expensive per weight stored than a pool on top and at the bottom

          1. I meant that you could fill you reservoir for free from a river. a hell of a lot cheaper per ton to fill a basin with water than to make concrete blocks

    3. Was coming to the comments to post exactly that video.

      I know thunderf00t is a physicist and can easily see through this scam, but I figured the staff here would atleast take a solid moment to think about anything that claims provide an unusual yet fantastic energy storage. I realized almost immediately that this was a uselessly inefficient way to store energy when I first heard about it years ago. Water energy storage works but even it has its limitations. This thing is either a scam or somebody’s “I don’t know enough about physics to do the math properly” dream.

      The only way this could be useful is for immediate emergency power. IE a bunch of blocks suspended in towers at a nuclear power plant to provide instant on power during a mains power failure while emergency generators started up. The mains power drops out, a solenoid or magnetically actuated latch let’s go and gravity does the rest. Have a bunch that trigger each other in series as each finishes. But even then a good battery bank would probably do the job better with no moving parts outside of relays.

      1. The pump storage plant at Dinorwic in Wales is now some decades old and was built, by the then Central Electricity Generating Board, for a very specific use case. To wit the sudden peak loads during commercial breaks on TV. There have been a number of documentaries and news items which show the operators in the UK National Grid central control room watching the clock and the TV. When the commentators started to lead to the break they would call for various gas turbine plants to spool up, and turn on Dinorwic. The turbine plants would take minutes whereas Dinorwic, which is a gravity storage system using water and the height difference between two lakes, would take 10s of seconds. I recollect one of the interviewees saying that their aim was to have the extra power available in the time it took a viewer to get up from their couch, walk to the kitchen and switch on the kettle!

        The water is pumped up hill during the night when power is cheap, and the turbine are reversible so they double as pumps. Gravity storage using any medium which has to be lifted or compressed would need to use reversible pumps or winches, which in fact they do. Pumped storage like Dinorwic needs a suitable mountain with a high and a low lake. The tech is the same as for hydro so is readily available. There is another system which may have already come on line in Scotland. Scottish Power are planning large battery sites near Glasgow and Edinburgh to provide local load balancing as well emergency power to hospitals and emergency services.

        My take on this article is that there are other ways of providing storage using gravity which may work better in situations where you already have big holes in the ground such as old mines, and if you don’t have mountains or holes in the ground you could use cranes. Be interesting to see the numbers.

        1. The Dinorwic plant wasn’t originally made for TV bathroom breaks, but for rebooting the grid in case of a massive system failure. If the national grid goes down because of a major solar storm for example, it can provide enough power to work as a stable frequency standard to drive up all the other generators and you can start connecting the loads back on the grid within hours. Otherwise you’d have to start them up gradually one by one, in a nation-wide blackout, and it would take days to get everything back together.

      2. I think you vastly underestimate how much energy is wasted, and the cost of that on current grid systems by several orders of magnitude…

        As you can put up a crane system anywhere, or a pumped water tank system in the basement and roof of every high-rise complex – its easily distributed. Its also damn nearly instant in reaction to demand, and none of these systems are bad efficiency wise, not all created equal, but non of them are vapourware that takes 2000Kw/h to give back 2… You take 2000K of excess and give it back when needed, you going to be getting back at least 1500k and on most of these systems it will be much nearer 1900 than that..

        So yeah the energy density of a crane system isn’t going to shock anybody, but if every little community has a few megawatts of gravity/compressed air store locally its a great grid balancing tool, and allows you to avoid transmission losses when they exceed the conversion losses – which would mean a pretty long distance on the grids, but the world is big enough it can happen. It is also much easier to gain efficiencies if you site such things at the bigger renewable farms- so you don’t have to transform the output to grid voltages and AC first, just directly use the excess DC generated, skipping the transformer losses, and any transmission losses at the time of storage.

        Or in short, its a perfectly valid and viable energy storage tech, it just has to be used in the right way (and compared to other self-contained energy storage techs not treated like it should compare to a nuke). Over its lifetime CAES and Hydro based systems will blow a battery system out of the water for energy throughput, maintenance costs, maintenance energy needs, all while needing nothing even remotely rare material wise. Therefore total efficiencies are going to be great, and its very practical to consider such systems for mass deployment. The crane based systems are in a similar situation though to me seem considerably more awkward.

        1. >if every little community has a few megawatts

          Please calculate how high you would need to lift a cubic yard of dirt to store 1 MWh of energy, or however many cubic yards it would take for how high you CAN lift it. Then come back to say how it is a sensible proposition to have one in “every little community”. (also, define “little”)

          1. I’ll do it for you: 1 cubic meter of loose dry soil – 300.8 kilometers.
            For a more manageable 30 meters, you need 10,000 cubic meters of soil.

            To put it in perspective, this is a chunk of dirt the size of a 7 storey apartment building as wide as it is tall. You would have to lift it up by its own height.

            As for the storage capacity, 1 MWh is approximately enough for 2,000 average British households for 1 hour. If you also include the gas bill in their energy consumption figure, by means of electric appliances and heating, it’s about 11½ minutes.

          2. Or: given an 80 AH 12V lead acid (I know, old technology) battery – about 1kWh
            How much mass do I need to lift 10 meters (height of my house) to equal that battery.
            Assume both are about 90% round trip, charge/discharge.
            You need to do this calculation – it puts all this in perspective.
            And it’s why we need flow batteries.

          3. For the curious, go to Wolfram Alpha and punch in “potential energy of 1000 kg for height of 10 meters”.

            (Spoilers: 27.24 Wh. Probably good for mood lighting.)

          4. Indeed, there are issues with any gravity store – but lets say every high-rise in a city has its grandfather clock style weight tubes built in from now on – they are already going to be rather tall, so you have a good drop in a structure you were building anyway – so the added cost to put it in is very low. Even if you assume each weight can only do 100W total (which makes the size of the weight rather small so a building can and would have more than one of them), now multiply by the number of tall buildings being built, or retrofitable (which in the real skyscraper cities is a stupidly large number). That is easily MW of storage across a nation (heck across a single city even) with no self discharging losses, at almost no cost. For the middle of nowhere type places building a few new ‘water towers’, isn’t much of an issue. If that lets you store efficiently the local renewable sourced excess for the longer term, its a win – its not like space is critically limited in most places on earth, and making your own mini mountain to hold some of the peak renewable excess longer term is still good.

            Yes gravity storage is never going to compete energy density wise with other storage systems, but because it doesn’t self-discharge, comes to full output quickly and done right will vastly outlast the chemical batteries its a valid solution – just not the only one. Like all things its picking the right tools for the job.

            The crane of energy storage makes less sense being rather awkward, until you factor in the key elements
            – the limits on how high it can grow are entirely design based – if the crane type system builds itself the same way tower cranes do you can potentially store years worth of excess energy – as the only limit to how tall it can get is the length of cable (it can’t grow any higher once it can’t pick up new blocks!) and the structural integrity of the blocks its using both as potential energy and its own tower (There are logistical challenges to doing so, I’m yet to be convinced it can really be done, but its definable plausible and actually makes a great deal of sense because of the following point)
            – it doesn’t self discharge, so over the windy and sunny periods you can stockpile and actually still get most of the energy back out even months later. Which if you want to run a grid off more green energy is obviously very useful.

            You will still want other solutions too no doubt, but its got a valid place – in the same way electric cars are for the right user an absolute miracle of efficiency and effectiveness, it still doesn’t mean they are practical or even useable for everyone.

        2. If the large blocks of were attached to a cable inside each offshore wind turbine, when there was excess wind a gear switch could directly wind the weight up. If there was no wind and big grid demand, another gear change and release the brake and generate from the falling weight. Skips the electricity to motor losses in the lift up phase.

          1. Now that is a genius idea, the things are already 30+meter tall towers above sea/ground level… And wide enough to easily fit a rather hefty block of steel, might need a little more structure and redesign inside the towers, but it can’t cost much, or add much maintenance.

          2. Yah, that could use some thought. It could also be a donut weight around the tower I guess. Possibly could also enable blade designs that are more efficient in steady breeze but are poor at self starting.

      1. Thus meeting the “small scale” of Al’s question at the end of his article.
        Another example is the winding of my clock, or watch, every night – a little work once a day provided a useful trickle of energy throughout the day. Although, these clocks were not providing the energy on an as-needed basis, but the idea is the same.

          1. Modern ones only lose about 10% a year. Only slightly faster than alkalines, but alkalines have higher capacity at extremely low discharge rates so they actually last as long as their shelf-life.

            But if you want your clock to run forever, lithium thionyl.

    1. You requested examples of smaller scale gravity energy storage. Weight driven clocks are a good example. On the electrical generation side there are gravity lights that work similarly.

  1. What is really interesting for me about this is that unlike batteries you have a next to zero static storage loss due to self discharge. If we want to create truly long term storage systems that can store excess grid power for months on end mechanical systems like this sound very interesting. They also have the benefit of being able to use previous recycled materials as their weights, thus removing environmental waste from the environment in the process of building them.

  2. Seems like using a reservoir of water would be better. After all, you could pipe in rainwater and get a bit more extra potential energy for free in addition to the water you expended energy to pump up to the reservoir.

    It’d be handy if a water-based gravity system could be built using the hot water discharged from another power plant’s cooling towers. That’d give the water more time to cool down before being discharged into the environment.

    1. Water is good where there is water. But, as the Taum Sauk disaster shows, water can be a problem even where there is plenty of water. I’ve seen one system using electric trains that drive up a mountain and then generate power on the way down.

    2. Stored water hydro generation is in use already around the world, and used to help balance out demand and generation.

      You pump up water to a high level reservoir using excess energy you need to store (as potential energy in the raised water), then you release the water back down, and generate electricity again via hydro generation when you need to generate again.

      Dinorwig in the UK is a well known example of this :

      1. Indeed – there are several pumped storage systems in the UK, and there are plans to expand those to allow more water to be raised by solar and wind generators (which are by their nature variable in how much they produce) as the coal and gas power stations are gradually phased out. Water works extremely well where the topology of the land is suitable. However it’s not that great if you don’t have mountains and lakes.

        (disclosure: I used to work for the company that operates Dinorwig and two other pumped storage schemes in Wales, and now work for the company that operates Cruachan and several hydro generation sites in Scotland)

  3. *rofl*everyone that seen anytime a crane in operation know, that moving strong weight will not work like in the video. I see this epically fail when some little wind is blowing. And all this allthough this big masses have no inertia in the video. All is working simple when you ignore the physics.

    1. When you’re talking in metric the word should be ‘tonne’ and the plural should be ‘tonnes’. Except apparently in American where they have decided to burden their tongues even further.

  4. could a purely electromagnetic solenoid type arrangement, where the solenoid is used to lift a heavy object which is later allowed to lower, be used to store energy electromagnetically using gravity?

  5. “The blocks don’t wear out much, either, so operating costs are low since there’s not much to replace frequently as is the case of batteries”

    yeah……… about that.

    The BLOCKS don’t wear out. Everything ELSE on that mechanical system though does. Cables, pulleys, bearings, axles, gearboxes, generators. Lot’s of steel in the tower and arms that needs frequent inspection and upkeep to keep it in suitable condition. The list can keep going for a while probably but you get the point. The great thing about fully electrical systems like batteries is that NOTHING moves except electrons. Unless you want it to, or there’s an earthquake. There is no mechanical wear. Sure battery cells wear out, but you can replace individual cells if need be. With the massive amount of parallelism in battery banks you can disconnect a single bank and not lose much functionality. Lose one crane in that Energyvault boondoggle and you lose a 6th of your generating power.

    Gravity storage systems are inefficient and very energy inefficient. They might work but I would be VERY surprised if any of them ever become commercially viable enough to compete with other types of systems. They all seem to ignore the very real cost of upkeep and maintenance in their cost per kWh calculations too, and assume they’ll never have to replace anything. Any engineer worth his salt will tell you that while speccing anything to last a full 25 year lifetime of such a product might theoretically be possible, it won’t be cheap. And even then you’ll have cases where it turns out you DO need early replacement.

    1. Bingo! Can you imagine the maintenance cycle for something like this? What happens when something fails unexpectedly? General rule of thumb is the less moving parts the more reliable something is.

      Fyi the reason current batteries are not suitable is the short lifetime. You have to replace the cells every ~5 years. This seems to not improve on that. We need a storage solution that will last ~30 years AND is cheap. Without that, all you have is a toy.

    2. If we for an example were to use lead as our weight. Mainly due to its fairly cheap price and exceptional density.

      Then we could make a comparison between the energy density of lead acid batteries (130 Wh/kg) to the energy density of lifting a weight. (9.82J/m)

      130Wh is in effect 468000 Joules.
      This means that we would need to lift our lead weight some 47.6 km to have equivalent energy storage for the material used.

      This distance is well over twice the high difference between the top of Mt Everest and the Challenger deep in the Mariana trench.

      From a pure material standpoint, it is likely better to just build lead acid batteries, not to mention that its volumetric energy density is also far greater. (batteries don’t need a deep hole under them to function.)

      Though, the main downside with lead acid batteries is that most “cheap” battery packs have 6 cells without any cell balancing, and are so called “maintenance free” batteries that can’t easily have their acid toped up over the years.

      The main failure point of lead acid batteries is after all that an individual cell gets discharged bellow about 1.85 volts, and the buildup of lead sulfide gets sufficiently thick to flake of.

      Lead sulfide takes up more space then lead/lead-oxide, so it has a similar problem as iron and its oxide. Though, a small bit of surface rust doesn’t generate enough force for it to overcome the adhesion to the bulk material. Only when the layer thickness is sufficiently thick to overcome that adhesion does it actually flake off due to shear force.

      And since the layer thickness is proportional to how discharged the cell is, then one can largely avoid the whole problem of the battery flaking to bits if one never discharges it that low. Then the only remaining failures is electrolyte boiling/evaporating off, or good old physical damage. Or the plastic case just crumbling of old age. (one can build the case out of glass, it is a lot less prone to aging, though more expensive.)

      In short, the vast majority of lead acid cells are tortured to death, while Lithium cells are treated as fragile flowers. (mainly since lithium can’t be overcharged, they are a bit more catastrophic in stating their displeasure.)

      But for grid energy storage and UPS systems, lead acid cells are a good candidate, an old fairly boring horse in the race though.

      The main downside of lead acid cells is their self discharge. 3% per month isn’t all that ideal for long term storage. But for 24-48 hour storage that self discharge wouldn’t introduce all that much losses. At that point, charge/discharge efficiency plays a larger roll.

      For longer term storage (weeks to months), looking into compressed air energy storage, or potentially hydrogen is better options due to far lower self discharge. Not to mention that CAES can be build practically anywhere in the world. Suspending large weights would either need good foundations, or good ground for digging a deep hole.

      It quickly becomes a question of material used compared to total energy stored. On top of the basic question of maintenance and storage density.

      1. The:
        “Then we could make a comparison between the energy density of lead acid batteries (130 Wh/kg) to the energy density of lifting a weight. (9.82J/m)

        130Wh is in effect 468000 Joules.
        This means that we would need to lift our lead weight some 47.6 km to have equivalent energy storage for the material used.” part is wrong,

        Lead acid batteries store about 35 Wh/kg, took the “specific power”, not the “specific energy”. Trivial mistake.

        Actual distance to lift for equivalent energy is 12831 meters, or a bit further than the challenger deep. Or about 50% higher than mount Everest. Still a very large distance.

  6. And a second thought occurred. How do you regulate such a system? Seems to me it’s either full power, or nothing when it comes to gravity. Trying to slow the decent just means injecting power into something else (probably friction heating in a brake system) which would bring your efficiency down something awful.

      1. Turbines regulate output by changing their blade pitch.

        How does this one “electrically brake” when it has to regulate its power output at the same time?

        Answer: either through an extremely elaborate gearbox, or by wasting energy.

        1. Some car manufacturers have built Continuously Variable Transmissions able to handle well above 100 kW while still being fairly small.

          It wouldn’t be unreasonable to build something a bit bigger for this application. Or just use a bunch of smaller ones in parallel for some added redundancy in case one breaks.

          CVTs aren’t anything new to be fair, and not that complicated for that matter.
          Efficiency is on par with other gearboxes so wouldn’t be unreasonable for the application.

          1. I wouldn’t go to the auto manufacturers when heavy construction equipment has CVTs now. I thought I heard that some of those supersize quarry dumptrucks had them, but can’t find a ref, just some front end loaders etc.

        2. Regen the power back into batteries which are physically located inside the weight which is being slowed. Then simply deposit the weight/battery directly into your fleet of EVs and off you go. Add enough complexity to go beyond comprehension, and this could be marketable to governments everywhere. No need to calculate anything but the renewable subsidy profit for the here-and-gone renewable energy industry.

  7. Here’s a great rule of thumb. If the product being sold comes with a cutsey little hand drawn astetic video. It’s a lot of ****. Many have already discussed how we have better ideas already in place and this one is terrible.

  8. 1 metric ton 100m up = 1000000 J = 1000 kJ = 1000kWs = 0,27 kWh

    That’s why you usually use lakes – to store A REALLY LOT OF LOTS of water for pumped-storage hydroelectricity. You really need a lot of height and even more mass to store usable ammounts of energy.

    1. For the announced 10-35 MWh capacity you need to lift 40000-120000 metric tons 100m up into the air.

      With ~2 t/m³ for concrete/soil that will be 20000-60000 cubic metres of storage lifted to 100m.
      Let’s say you stack that in 50-150m. So for the small 10MWh storage in a 100m tick layer you need 400m² of storage, or an 25m wide yenga tower, swaying at ~50-150m height.

      For 5MW output (let’s say 6 – as that has 6 arms in operation, half of them on the way down) each downward arm has to generate 2 MW. So each arm needs to “drop” 2 metric tons the full distance of 100m EACH SECOND.
      But just for falling free 100m anything will need 4.5 seconds (even disregarding air resistance).

      So just for the math to sum up each arm will have to drop 10 metric tons every 5 seconds.
      Plus braking delay.
      So more like 50 metric tons every 10 seconds.
      Including precision pickup / placing.
      I guess, someone needs to go back to the drawing board.

    2. Oh cool, so if you built a 100m tower in your own back yard and hung a ton off it, you could spend an hour or so pedalling your ass off on a bicycle winch to run a Raspberry Pi for half the day.

      1. More efficient way to power your Pi than pedalling into an chemical battery, if you build it right at least…
        And if you don’t take the energy out that day its still there next year..

        Though for a Pi you could just pedal as you use – its more than low enough wattage.. call it 10W (which is actually hard to get up to as a sustained draw on a Pi, even a Pi 4) your pro level cyclist can output well over 600W, and a halfway keen regular person should easily keep up 200W and probably peak into the 300-400W range…

        1. You could buy D batteries for the rest of your life to power the Pi for what it cost to put up the tower though. For values of “put up” that imply also lasting 25 years to life.

          1. At least for now – at some point the green movement will manage to ban alkali batteries I don’t doubt… Though I’m not sure if that is really true, a ton isn’t actually all that much to support, I think I’d rather support 3-5 ton at much smaller distance – perhaps the Colin Furze Trebuchet sort of scale… I expect that thing would make a great energy storage medium too..

            Which is really really stupid – in the right places they are the only sane energy storage medium, as they barely self-discharge.

  9. Mine shafts might be free, but keeping them free of water isn’t.
    Pumping the water out to the very bottom is energy intensive.

    Or you could let them flood, but then the buoyancy of the water reduces the gravitational potential energy available quite significantly. Also, water resistance when moving the weights up and down will further reduce the efficiency.

    @THisGuy “to slow the deScent” you can use the back e.m.f. in the generators, depending on how much electrical power you let out of the system. But it will still hurt efficiency.

    1. If you had a mine next to the sea, you might be better off putting a turbine in the bottom, and flooding it deliberately through it, also possibly using air displacement for another turbine.. and pumping it out again when the electricity is cheap. Anyway, you’d use the whole volume of the mine, which I think would be several times greater than the volume you could sweep just in the biggest shaft.

  10. You talking energy and then using watts, which is a unit for power. This can’t work.

    Of course you can use 100 W to charge a system capable of releasing 1000 W. It just takes ten times longer to charge than to discharge (plus whatever gets eaten by the system, which usually is more than zero).

  11. Basically mine shafts are the only viable place to operate such a system, because an old mine shaft needs to be kept free of water (or filled up) or it will collapse and the holes in the soil will propagate up to the ground level, where it can turn into sinkholes.

    The pumping is going on, needs to be kept on, so just lessen the burden.

    But the tower crane system -> .. nothing ..

    1. Does that not depend on the type of mine? I’d imagine a salt mine is what you’d least want to flood, and an ore mine, where veins were worked between areas of solid rock, would be least vulnerable.

    1. With all the praise of this concept, kind of reminds of all the hype given to perpetual motion machines, or over unity devices. Both of which never seem to come all that close to delivering, what the computer models promised…

      Gravity, isn’t always our friend. It’s going to take a whole lot more energy to hoist the blocks, than can ever be hoped to recover in the lowering.

    1. I’ve seen that video before, I always think it would be a great bonus question for a college engineering exam “How many conceptual errors can you see with this scheme – show your work”

  12. Ok, so if we can’t build some sort of oblisk designed to vibrate a certain frequency, attached to some sort mechanical means of generating energy, make a gigantic grid of lightning rods throughout the country, condition the electricity to move these giant blocks up.

  13. Using a lever you can easily stack massive blocks at a fraction of the energy that would be produced. With a 100:1 lever you could lift 100,000 lbs with 1,000 pounds. Drop the 100,000 lbs which is connected to a hydraulic system that generates hydro power. This should be produced at a much smaller scale to perfect obviously, but I think its a wonderful idea.

    1. Just to be clear – The lever doesn’t change the energy total required, but it will allow you to use the low output rate source to charge up a beefy gravity battery that can output all the energy put in much faster. Its no magic energy multiplier, just a force multiplier.

    2. You are forgetting that the lever only lifts it 1/100 as far as you need to lift the lower weight. It’s practically the same as if you cut the 100,000lb into 100 chunks and lifted them all individually.

  14. Gravity Power has almost no surface footprint. The vertical shafts are bored using TBMs. Once the shaft above and below the piston is filled with water it never needs any more water since it is a closed system with no evaporation. Can be sited right next to, or under, solar or wind farms. Pump/turbine also in underground room. Very little maintenance. Very efficient pump/turbines already engineered for conventional pumped storage systems. Almost nothing visible and nothing audible on the surface, so NIMBY avoided.

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