How gravity batteries could change the world

We had a cuckoo clock with gravity batteries when I was a kid. Back then we called them weights.

I work in the electricity industry on policy issues and it always shocks non-technical people that we are never more than 0.2 seconds from a full grid blackout. They never really understand the way the traditional grid depends on multiple layers of security margin and how intermittent renewables reduce that dramatically. We desperately need storage as that is the only way that grid can be truly carbon free. The only issue is how much it will cost.

The amount of maintenance required for a mechanical system like this is an absolute nightmare. Just ask any elevator technician. Pumping water back up to an elevated reservoir only has 1 moving part per pump.

Make a functional prototype(produces energy) and then calculate realistic maintenance costs. It better be seismic resistant too.

The demonstrator plant in the video: 15 meters height of the tower looks like the 50 tons weight only can move around 11 meters? That means that this system that cost £1 million to build can store 1.5 kWh! I hope you are all very impressed by this cutting edge technology. A li-ion battery with that capacity weigh less than 10kg and cost $200! So even if the 50 years claimed life of the tower comes true, it will still be 1000 times more expensive than a single Li-ion battery you can carry with one hand. This is a scam to trick investors that for some reason didn't pay enough attention in school during science class. So can it be used for short bursts of power then?: The "fast" drop, shown in the video, the weight drops at around 1m per second, so it can supply a burst power of 491kW for 11 seconds. However the claim in the video says that peak power is only 250kW, so that means there are losses of around 50% in the system, which is both ways btw, i.e. for going up and going down so in reality, a 5 kg $100 Li-ion battery is enough to replace this device and the tower has a combined cycle efficiency of only 25%, like Hydrogen fuel cell energy storage, but you don't even have waste heat here as a byproduct!! That is maybe still enough to make this useful at a local electricity distributer to mediate fluctuations, however to deliver 250kW for an hour, you'll need a weight 327 times heavier and the company is even suggesting a 20MW system running for 8 hours which would mean 327*8*80=208,000 times bigger than the demonstrator plant and it would need 4 times the amount of energy in, as you can recover per cycle, so highly wasteful, as I already mentioned. To continue the "number of homes" analogy in the video, it would mean 3 towers like this per home!. Youtube commenters and politicians alike: if you ever hear about this again, dismiss it immediately, it is a scam, in the literal sense, not only meaning sketchy or overly optimistic. This company knows very well that this can't possibly work. They are only out to pocket public money, to then just disappear when they get them!

I thought of this 40 years ago told a lot of people the big money power company’s blew me off. You could drill dry wells and do the same thing for individual homes.

Sorry. This cannot work. I ran the numbers a few months ago in a discussion forum. Here is what I posted last April: The issue is the achingly low energy density per foot print unit area or construction cost. Digging a shaft would either have to be done through very sturdy soil (costly) or require bracing so that the pit does not collapse (also costly). If you compare with a well known hydro facility like the Hoover dam, and consider the figures, you can see how off the whole concept is. Hoover dam water head: 180 m Flow: 3300 tonne per second Installed power: 2 GW Active capacity: 19.554 km³ Reservoir area: 640 km² Cost: $49 million in 1931; reportedly the equivalent of $684 million in 2020 dollar This means, in the absence of replenishment, that Hoover dam could produce those 2 GW for about 6 million seconds, or almost 70 days, before the level gets too low. For the record, Los Angeles reportedly consumes 22000 GWh of electrical energy per year, which roughly translates to an average of 2.5 GW (but seemingly would peak at 7.8 GW) The largest solar farm in the world is in India, and has a 2.2 GW capacity (and covers over 56 km²) This happens to be a nice figure because it is essentially the same as Hoover dam. So, assuming that one does not have anything besides a very poorly flowing river but with a 180 m head, but with adequate reservoir capacity both uphill and downhill (about 10 km² area, if scaled from the lake Mead) and the equivalent of the Hoover dam power station that can be reversed to pump up the water, one would have a pair of solar farms of ~2 GW, one to power the actual day consumption, one to power the reversible hydraulic system during ‘charging-up’, and rely on the hydro reservoir to provide the power during night time, for an essentially constant 2 GW power production. (Of course, there are variations during a day, more power needed at certain time than others, but let’s just assume that it is regulated and balanced for simplicity’s sake). The final footprint for such an installation is around 132 km², 85% of which is solar farm. Interestingly, Los Angeles, as a city, covers 1302 km². Evidently, putting installations covering 1/10 the surface area of a city to power it will likely be done by finding suitable locations, which could be somewhat distant; high power transmission lines can allow the solar farm from not even be located close to the “hydraulic battery”, nor to the city itself. Now, let’s scale this down to this ‘crane and weight’ scheme. They were talking about 7000 blocks 30 tonnes each. They want to have a 100 m head. They want to use this operating for 8 hours (too low in my opinion, but let’s use their numbers). That means they would be dealing with 7.3 tonnes per second. 100 m 7.3 t compared with Hoover dam’s 180 m and 3300 t. So, their concept would be 0.123% of Hoover dam capacity, and you would need 814 such installations to compare. The cost for the structure of a building is reportedly between $35 and $50 per square foot – this value is for building that actually gets built, probably having somewhat distributed floor weight; this gravity battery would on the other hand be top heavy when fully charged, that probably means it would cost more, structurally, but let’s go with $50 and call it optimistic for now. The cost for digging a basement is reportedly $10 to $20 per square foot – but since a basement is only partly underground, the cost for a deeper well will be more expensive, as machinery will have to be lowered and soil brought up, etc. Interestingly, googling “cost for digging deep foundations” brings something that mentions ‘between $25 to $50 per square foot’, so apparently it costs essentially as much going up as digging down. So, you have this tower (or underground shaft) that will be housing 210000 tonne of blocks, and move them over 100 m height difference – the equivalent of 30 stories. Assume that you have 30 stories used as storage (i.e. story 1 blocks would be stored at level 31 when ‘high’, and blocks low at 30 would be hoisted to level 60) and we have a 60 story building. 7000 blocks distributed over 30 stories means 233 blocks per level, or 7000 tonne per level. Soil has a density of 2.65; concrete is 2.4. Let’s assume the density of the blocks would be around 2.5, as we have to take into account overall gaps, and the machinery to move them around, the tracks and so on. 7000 tonnes therefore mean 2800 m³. With 3 m height, we have 933 m² ‘foot print’ – essentially 10000 square feet. Time 60 ‘stories’, we have an equivalent of 600000 square feet. At $50 per square feet, that is $30 million. Only for the structure. To scale this back to Hoover dam proportion, we multiply by 814 – $24.4 billion. 35 times the cost to build Hoover dam. Again, only for the structure. No tracks, no lift, no power system. It does not matter if it is made part of an existing building or stand on its own; it would require its own structure to keep that weight up. That is why this project is ridiculous. It can never be cost competitive.

A promising alternative is bouyancy power. Instead of lifting something in the open air, lower a bouyant object like a big baloon in liquid. Releasing the object makes it float up and that force can be used. It allows for using a lot less space.

I still did not heard in this animation movie how exactly making weights solid instead of just pumping water makes it cheaper? Heavy lifts/elevators generally are quite expensive machines, while a water container is much simpler device, with the pump and pipes being the elements which require most service.

We have this with pumped hydro and systems that use a weight and a water tank to force water out by gravity in an Accumulator.

As others have mentioned, just pump water instead of lifting weights. Turbines placed at the bottom of mine shafts would generate the electricity. Pumps would get the water back up to the surface. Mine shafts could have curves in them, but appropriately sized pipes would snake their way down to the turbines and pumps. All you need is the desired height. Also, pumped water shafts are somewhat impervious to ground water infiltration since you would already have the pumps at the bottom of the shaft. Appropriate lining, as required for sections of the shaft would keep water infiltration rate under control. At the surface, place a large pond to accumulate all the pumped water. Above that water, place your solar panels. This could be an opportunity for profitable cheap hilly land in Pennsylvania, with lots of conveniently placed abandoned coal mines and mine shafts. Valleys in those mountains would become the ponds for storage. Solar and wind turbines, if appropriate, would span the tops of the hills. GitRDone!

Water bag batteries are my favorite. You use excess power to pump water into a giant bladder, when you need power, you open a valve in the bladder and use a combination of having a slope and progressively smaller tubes leading to a tiny nozzle that shoots the water into a turbine , which spins and generates power. Its basically a different kind of gravity battery

Use tidal energy to raise water to a height...and let it out all day and night... ( Tidal is available only at specific times)..the water stored at a height can be continuously tapped.

I've thought of this independently since I was a kid. I just wonder how much weight/space was needed to be practical

I want something like this in my back yard. I would lift weights and carry them up the stairs into a large bin. I'd get a workout and also get some free electricity.

I've worked heavy industrial for years, and the maintenance on this would very high along with a higher than acceptable failure rate.

let's say we need to store enough energy to then produce 50 MW for 12 hours (at night). probably enough for a small town. 50 MW * 3600 * 12 = 2160 GJ - we need to store such energy. Now let's calculate the mass of the load if the lifting height is, say, 100m. E = mgh , h = 100m, then m = Е(g * h) = 2160 ГДж/(10 m/s^2 * 100m) = TWO MILLIONS TONS ... For a rough estimate - this is about a cube concrete 100 x 100 x 100 meters :)

Here is another idea: Abandoned strip mines can be half a mile deep. They look like an upside-down cake. The deep part of the mine is narrow. The part of the mine at the surface with the earth is wide. So, put turbines and pumps at the bottom of the mine. An appropriately sized catch water basin for the pumps at the bottom. Build a "pool" structure towards the top of the cake close to the surface. That pool is supported on a foundation around the circumference of the bottom of one of the top layers of the cake. The pool is as many feet in depth as you want for your potential energy storage. Solar supported and placed above the pool. At the center of the top circle of the cake, you build a cone section that goes lower than the bottom of your pool. That is to set up a center of gravity for all that weight of water. A column structure going down to the bottom of the mine supports that center of the pool. In the space between the bottom of the mine and underneath the pool structure you put your electric power plant and underground high voltage transmission out. Now, drop water to the turbines, pump it up for storage. Rinse and repeat. But, actually, there is a cheaper way to do the above with strip mines. You can spend a lot less money in the building of the pool of water over the mine. That is, that pool that is just hiding the previously ugly carved out strip mine. It could just be very shallow. The reason for that is that it would limit the weight that you would need your structure to support. For energy production, you're just interested in the height of the water column from the surface of the pool to the bottom of the strip mine. Then, if you have land adjoining your strip mine, dig appropriately around the mine to build a pond/lake to any volume you desire for your "water battery". That additional adjoining pond is cheaper, since the land itself supports that water weight. That section of water is also connected to the shallow part over the strip mine. By doing so, not only do you get a nice new lake for lake front living, but you have energy storage in the form of potential energy between the lake and the turbines and now you don't have to look at the ugly strip mine on your land. P.S. I'm a retired Electrical Engineer. All we need in this world is some imagination. Come on people. Get it done. There is always a way.

If the top of the tower was able to rotate and you placed a vertical sail or blades atop it, the wind could gently rotate the weight array and add even more potential energy via centrifugal force.

This is the more advanced concept after hydropower plant. Water may be evaporated and smeared out to soil and its specific gravity is only 1. If we use concrete with 2.5, then it saves space much. Also this system is more controllable in frequently varying power condition. However it may be more expensive than the hydro power plant in large scale.