Gravity Energy Storage. Who's right and who's wrong?
Gravity energy storage has real potential to provide cheap reliable grid balancing electricity to compliment the ever growing volume of intermittent renewables on our power grids, but only if it's done in the right way. Two companies, Energy Vault and Gravitricity have both taken radically different approaches to the problem. So, who will come out on top?
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Energy vault feels like a crane salesman, a concrete supplier, and a computer animator got together for some beers.
Don't forget a guy from silicon valley.
Don't forget to add: "made by *clever* engineer grad students start-up"!! It works people, they confirm it.
You noticed that right..
It sounds like something as simple as closing the system inside of a silo would have solved 99% of the "debunking" that went on about it.
@@Belthazar1113 As long as that 100% is weather related concerns, possibly. Otherwise, no. Pop quiz! What's the energy potential stored in a concrete block at the bottom of a stack?
Energy Vault appear to be building a Borg cube, keep a close eye on them, is all I'm saying.
Resistance is futile...
You've done the public a good service by following up on these companies' progress. Please do continue to provide videos when there is news to share.
I do believe that pumped hydro is ultimately the answer. It has been a proven technology with far fewer longevity problems than the mechanical wear and tear of wire rope llift systems. Respectfully, Dennis, KV4WM
Yes and it has an impressive effenciency if build big enough.
And you could probably build hundreds of water towers for the cost of one building full of concrete blocks.
Head loss (friction) in the pipes is the problem with hydro. Pulleys are much more efficient.
It obviously has geographical issues though, a lot of countries have nowhere else to put any more hydroelectricity, england for one example really, we dont really have anywhere else to put them, an alternate way of doing what hydro can do is absolutely something worth atleast looking into, since were going to need it for a green revolution.
@@darrennew8211 the problem is you cannot build towers big enough to be very effective. You need a huge amount of water and height to do pimped hydro.
Fair play Dave. I love the fact that you circle back. Keep it going. These progress reports are interesting. Thank you
Cheers Brendan. Much appreciated.
@@JustHaveaThink 🎓
You know he takes this seriously, and has an open mind, and just not gullible, as he takes in account debunker channel input. Much more credible than your typical Tesla fan boy.
@@Freja_Solstheim There is a reason they didn't compare it to hydro. this is so laughable tiny (24.4MWh), nobody would consider to build a hydro this tiny. LCOS scale mostly with size (especially for hydro). Actual average Data from Lazard (same source the imperial college of London uses sometimes): compressed air, pumped hydro, and lithium ion batteries are $128/MWh, $175/MWh, and $414/MWh But that's real data including the cost overrun during construction etc. Meanwhile the calculated number for the "new" tech is the estimate of the enterprise proposing it. I didn't find this Study, but another one for gravitational storage: heindl-energy.com/wp-content/uploads/2018/10/LCOS_GravityStorage-II-Okt-2018.pdf Something a bit more serious, as the stored values are of significance (it's basically a hydro which could be built anywhere, again numbers are estimate (probably optimistic ones)). Page 8 also reveals why we don't just make it all compressed air: compared it's rather inefficient with only 42% of the energy recovered.
@@JustHaveaThink just been reading an article about algae being used in glass panels on buildings which sounds interesting. >Beautifully designed, energy-generating bio-panels that suck up carbon dioxide and pump out biomass for use as fuel or fertilizer - that's the idea behind Mexican startup Greenfluidics and its nanotech-enhanced microalgae bioreactor building panels.
I can't believe that energy vault got as far as it did, at best it was too finicky & the next version isn't much better. The gravitricity mineshaft version looks more promising with a more controlled environment, fewer points of failure, it has a much smaller footprint, regenerative power is proven, and cheaper to implement since the hole is already there.
It is also not very convincing that they present their (final) idea and probably pitch for money without having built a reasonable prototype to test their theory. After "working" on whatever and getting told that the idea will not work, they completely change their concept.
@@Kiboxxx Yes! Their idea crumbled under basic scrutiny (though not before wasting a lot of money) but it's a good idea to never trust a company that only ever presents CGI concepts, proof of concept isn't just important but vital.
But just wait until the rock monsters see that iron ore coming down. The Enterprise may have to tractor beam the ore up before they nibble on it! 🚀
discarded minshafts make for unsexy powerpoint when marketing to investors
@ Evil Otto I disagree. Discarded mineshaft areas are less likely to draw the protest crowds when a company seeks to do something there.
I would like to know the actual number of "vertical mineshafts" available with sufficient depth, no water intrusion and other factors to support this. I think that will limit scale. I would also like to know the levelized cost to develop a virgin site under reasonable conditions, ie no worries about water infiltration. That number would represent a scaleable solution. Anything else I think would be less interesting. We can't rely on old mine shafts for a critical new energy storage technology.
I tried to find this but was unsuccessful. I did find out that there are 500,000 abandoned hardrock mines in the USA. But that doesn't give much further information on how suitable for this project they would be. But 500k is a pretty big number - even if a fraction of these are suitable that's still a lot of sites. I also don't think hardrock mines includes coal mines.
Using a water/air tight shaft lining the water intrusion point become moot. As in my mind Gravitricity would want to keep the shaft as clean and dry as possible. Which means that they would have to use some kind of lining in the drop shaft
It's gonna take a while to get firm numbers, but my findings so far: Considering the worst-case scenario of a reinforced-concrete-lined vertical borehole gravity energy storage system in, say, the Amazon rainforest where the ground is always saturated; seepage rate across a given section of the inevitably-porous concrete is ((groundwater head pressure) -(viscous back-pressure))•(area of section); taking the integral of this function with respect to area will give us a flow rate value in units of volume per unit time. Due to this, out-pumping costs scale with the square of borehole depth, so there is definitely a limit to scalability *in certain biomes*
@@charlesmartin1972 Heavy water seepage just provides an opportunity to build it as pumped storage instead, with the lower reservoir at the bottom of the hole. Shaft cleanliness seems a non-issue with enough slippage space between the weight and the walls. Remember that whomever used the hole for mining was already lifting things and people in and out of the hole. Graviticity doesn't need the hole to be safe for humans and don't need the various side shafts (all except construction and maintenance work of cause). A thin (2 inch) concrete lining like in sewer pipes and manholes would be enough for a hole in regular ground conditions rather than mine shafts. 500m depth could also be a repurposed elevator shaft in an economically failed skyscraper (originally built at prohibitive cost) or an intentional design feature in new skyscrapers where most of the building is making rent income to fund everything.
@@johndododoe1411 the volume occupied by free water represents a loss of gravitational potential energy available to the weights. Also, seepage through the walls is not passing over a turbine and is thus a net efficiency loss
I love that you addressed "Adam Something" video on gravity storage.
Most mine shafts need constant dewatering to remove water ingress. This comes at a high energy cost which has not been factored into levelized-cost callcs
Maybe they plan to operate in flooded holes.
Good point. That natural inflow of water takes off a slice of the potential energy to be stored.
@ Dan Tronics I don’t think energy storage systems of any sort need to be near where demand is. They just need to be somewhere along the grid to take in excess power and feed it back into the grid as needed.
@@janwinders9702 not likely. weight in water is considerably less than in air. Also there will be significant hydraulic drag both lowering and raising the weight
I don't know, find a spot on a hill in the Western US, pump the water up/out let it run down hill. Recover some electric cost with hydro generation. If there is a gully and Hill at the bottom, you will get the water to return underground away from your project and start to turn the desert into grassland.
On a delta height of 360 meters, you get 1kWh/ton. To have 1 GWh of storage, you need 1 million tons of weights to move up and down over 360m. If your weights' density is 5 kg/l, you'll have 200'000 cubic meters of volume, which is roughly a parallelepiped of 100x100x20 meters. This is why storing large amounts of energy with gravity is hard (unless you use water reservoirs): because you need a lot of materials and space.
Yup .. and water flows all by itself so you don’t need to stack it. No question water for long-term storage and batteries for short term is where this is going. Large battery buyers are buying under $150/kWh today, CATL anticipates being under $50/kWh this year for (Sodium batteries if memory serves) .. and we are no where near the limit on battery/performance/price.
Don't forget that installation of the weights allows that the gravity battery can start out in the "Fully charged" position. As long as the modular design has enough modules and energy collection equipment, there is a chance that the gravity battery can keep up with demand. I think it's important to think of the gravity battery as a secondary source of energy when demand requires it's use, or more or less a supplement to existing infrastructure.
@@davidleaman6801 and I think you are and idiot, Sir.
100x100x20 seems doable...
@@solarguy4850 Water is problematic because it's a liquid, it's harder to contain than solids, it can evaporate and couses corrosion, so imo pumped hydro is best built using natural terrain. Good boon for gravity storage is that it doesn't lose capacity over the years, downside being moving parts but pumped hydro has the same problem albiet smaller
If they're planning to build a facility into an old mine, pumped storage with water is still better than moving ore around. Many old mines are full of water --- ground water intrusion is a major engineering concern in most active mines, many of them flood almost as soon as they're decommissioned, and the pumps are shut down. It does seem like an end of life mine already has most of the infrastructure in place for pumped storage.
Most Mines keep a certain area clear of water to make sure the shaft doesn't collapse. And those pumps will run indefinetly.
As you said, you need constant pumping to keep the water out. Pumped hydro can't work if the bottom lake keeps filling on it's own
@@zbarba In most cases, the speed it fills at is slow enough to not be a problem. The capacity is generally very, very large. It would likely be much larger than whatever the surface area tank or lake would be.
@@chuckoneill2023 I find that hard to believe. You get a lot of volume from a reservoir since it is roughly cube or cone shaped. Meanwhile a mineshaft is by design narrow and windy.
@@ruukinen Actually, I think you're confusing a mine with a cave or cavern. Mine shafts are generally cut as straight as possible, for ease of removing the ore. In any case, however straight or crooked the shafts are has little impact on the flow of water. I toured an old below ground iron mine a few years ago. The void left behind by mining out a large deposit was basically the size of a cathedral.
Excellent content delivered in a quiet and understandable manner. Love the fact that Gravitricity is run by engineers too.
I don't like the cube towers, since it's a total electrical energy loss to transport blocks laterally. It doesn't affect the potential energy, but it does drain electrical energy to move the blocks anywhere but up and down. This is a drain on stacked block towers too. Moving blocks closer or further from the tower core is a net loss.
There's a lot more issues with that concept. While the principle is tried and proven as a warehouse system, there has never been a setup like this as far as I am aware with handling weights anywhere near this.
There is also the issue of the embedded energy in the construction.
Not just lost energy... Wayyy too many potential points of failure. A weight suspended on a hoist could be deployed even if there was no energy in the system... Like during a total outtage. But a giant warehouse of weights stored in computer-controlled conveyances by definition requires inputs to operate, so it could never be used as emergency power during outtages. And is just flat out going to break down at some point.
@@patreekotime4578 I can't believe I'm defending this daft design, but all power stations require some power to operate. In this case you would just need to have enough weights ready to drop to ensure there was power to move the weights sideways.
The engineers should be able to design the system in such a way that the blocks that have to travel laterally do that on a small slope configuration ,to reach their destination; by equipping the blocks with temporary rollers, or design the transport railing system with permanent ones.
I like the idea of gravity storage, but I can't see this being useful for mass storage, say to get us through a period of gloomy, windless weather. It would appear that its utility will be for grid balancing.
Yeah, exactly. I see this more as covering overnight demand for a solar farm than holding those weights up waiting for a rainy day.
There's more than one kind of storage issue with renewable sources, and wind and solar have different problems. Despite the "OMG WHAT IF THE SUN STOPS SHINING OR THERE'S A VOLCANO OR A METEOR HITS THE EARTH???" nonsense, there's some very regular, quite predictable variation in both output and demand. So if you can compensate for that expected variation, you can turn either wind or solar into a consistent supply that can handle normal day-to-day variations. And those variations don't need nearly as much storage as saving energy so we can not have interruptions while the asteroid dust cloud blots out the Sun for seventeen years or whatever...
Used for grid balancing. for over 100 years en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
Calculate how much mass you would need. It's enormous. Think mountains.
That really depends on the amount of mass in storage. With sufficient mass reserves to account for worst-case scenarios it should be OK. It's not as if the blocks are evaporating or chemically degrading while they sit in storage, so other than the requirement for 'excess' storage area there shouldn't be many downsides.
Thanks for this Dave! I really appreciate this retrospective format and would love to see more
i gave this some thought, and imagined it could be used out at sea for offshore wind storage. just a few more appendages hanging off a tied together wind farm. could even be the righting ballast and be as deep as where the farm is situated. could even hang freely in some places without a structure to drop it in.
For sure gravitricity is more promising, the only problem - they using old mines. And here we have a problem, because from my knowledge they have a tendency to be flooded by ground water hence changing this ideal system. For safety reasons quite often water is pumped out, but the point is, part of stored electricity will be used to pump out the water, so hopefully balance would be still positive.
You know, that sounds like mines would make a good candidate for pumped hydro... pump the groundwater to the surface on off-peak hours (with a small amount of power used to re-circulate water the seeps back in), then release it through the pumps to and release the water back into the mine and generate power on demand.
@@erininstereo47 well, then you need to store it somewhere, and in a meantime new water come from the ground. So basically more water you have to pump out vs what you could possibly use. I'm not an engineer in this area, it just what come to my mind, probably this company have someone from this area in the team.
Make a video about energy storage in sand. I am sure you've read about the Finnish company that started to use it to warm homes.
Have you been watching "Robert Murray-Smith" latest video no. 1604?
@@sailaway8244 no. I saw a video about it on BBC
@@Whyoakdbi kzhead.info/sun/bKaQZauQZ2d8nqc/bejne.html
I think he did a video on it 2-3 months ago
I recently saw an article on this. Interesting idea. Like this one, I hope it is viable and pans out.
This might be great in a few locations that have pre-existing mine shafts, but not many places do, so it’s like pumped hydro in that regard.
Thank you for this and nice citation -) I am always happy to see engineers initiating projects in the repurposed renewable energy field as most projects therein are not all that renewable and more marketing than fantastic engineering.
Being Scottish Engineers I wouldn't bet against them. They don't tend to be bs merchants. A large part of the Industrial and Scientific revolutions of the 1800's and the British empire is based on the brilliance of Scottish scientists and engineers (and I say that as a wretched Sassenach)
Read "How the Scots Invented the Modern World".
As a scotsman I can assure you there are plenty of BS merchants north of the border, especially when there's a bit of free cash going for research. the fact that someone did something 150 years ago is no predictor of current performance.
I believe Scotland has the highest ratio of patents per capita anywhere in the world.
They could just use Loch Ness (221 m), Loch Morar (310) or other lakes. The north sea could be used (even if water with salt are nasty stuff for any equipment).
@@bknesheim use it for what? Loch ness is 15m above sea level.
I had a memory of doing energy storage using train cars on a slope so did some googling and found "ADVANCED RAIL ENERGY STORAGE". seems like you could do that in more places without the need for an existing mine shaft.
Yes, and you could store more if the mass was stored at the top and bottom, so one rail car could carry multiple lots of rock, rather than a single lot as in this design. However both pale when compared to pumped hydro. Snowy 2 for instance stores 350 GWh. With cheap UHVDC the location of the pumped hydro isn't as critical. Any old mountain by the sea could be pressed into service.
They are building the train cart.energy storage in Nevada. We might see it in 2035.
Remembered seeing that video also. Seems to be easier to install and maintain than either of the two mentioned in this video. And easily scalable also.
In Australia the Fortescue Metals Group is planing a system like that near Port Hedland
Great service from you guys always. Well done keep the projects gong
I can see how Gravitricity's system can be adapted well to decommissioned powerplants, but in the case of mineshaft would it not just be easier to use Hydro, pumping water in and out of the mine? Love these videos by the way. It is nice to see how these technological concepts progresses
Where do you put the water you pump out of the mine?. and how do you stop the empty mine filling with water naturally? if you can solve these then you've invended pumped storage.
@@mralistair737 Creating surface water basins is not expensive per volume at all. In most mine shaft solutions you need solutions to prevent the mines from filling up naturally, through additional pumping of good sealing measures. With heavy block you could indeed have the blocks sink into partially water filled mines, but that would result in complex engineering as well. lifting and lowering a single 50 ton block in a 300 m mine shaft does not give a lot of energy: E=mass*gravity*height=50000*10*300 J = 150 MJ = about = 40 kitchen kettles during 1 hour.
The thing I like that after 50 years, the Gravitricity storage maybe worn out and need replacing but the hole may need just a new lining to stop water intrusion and the new one may be a fraction of the cost of the first!
Thanks for revisiting them! I often find myself thinking about what they've been up to.
Having worked for a couple of engineering startups, the word 'modular' is one of those engineering red flags that investors haven't caught on to yet
You mean small modular reactors won't be a THING?
@@srvq3101 ha, brilliant, exactly. Managed to fool Boris though didn't it
I would've liked to hear more about the energy capacity of such a system. Even if the results are positive it would have a very limited impact given that it has a ceiling already in the amount of existing mines. Even if the weights are heavier they can't possibly compete with the capacity of pumped-hydro.
Also concrete is only twice as dense as water so I bet you could store almost the same energy without all that equipment in plain water... maybe salty water, water isn't scarse, drinkable water is, if you keep it close mantainance would be minimal, you will only need to fill it once, keeping it close avoids evaporation
@@ratgr Water is scarse in some places around the world but not having to transport rock to a location where it is avalible seems a logical option. The perfect combination in my view would be desert based solar panel farm and sand filled weights. Why make concrete if it does not have to be structual.
@@lenrichardson7349 The problem with sand is its corrosiveness, its not a fluid so you cant really pump it normally but you could use a screw pump, It will need more manteinance, and some other mechanical help to avoid dunes, before you recomend sand bags that makes it worse, you'll need some kind of computerized complex mechanical mechanism and wouldn't be able to use the mine in its entirety. Water can be transported from the closest source, either pumped or water trucks, its mostly a one time cost, you only have to make the walls impermiable and the loses should be small, you dont even need this water to be fresh water, you could use salty water, very few places in the world are both far away from a water source and close to a population.
@@aaronlockey6429 the crane-managed block tower idea also had an expensive working prototype, although not to full scale. They had some multi crane tower and some barrels filled with concrete. The new design/3D-animation-concept doesn't have anything real AFAIK, although apparently they have a contract with China somehow. Ironically the closest thing to a prototype for that would be the prototype for gravitricity, specially if they gave up the nonsense of horizontal transport of the weights for no reason. Then it would at least look somewhat credible, although to me it wouldn't be clear whether the return on investment is really superior to just pump-hydro even if in ridiculously small sizes for pump hydro. Like filling the mines themselves with water and pumping it to a ground-level pool. Maybe one could hybridize the water supply system with something like that to some degree, as it has to be pumped up at some point, and has to go down.
I think it's fair to say the energy storage, just like energy production for a sustainable future has to be a multi-faceted approach, often depending on geography and facilities. Just like you wouldn't put solar farms in the high arctic or antarctic or wind farms in a calm area, you'd look at the geography of an area to see what energy storage would be most efficient in each case. If we did things based on studies, data, scientific approach to problem solving for maximum efficiency we could crack the code for 100% renewable energy worldwide, with adequate storage.
Thanks, I love the concept of revisiting previous video subjects to track the progress :)
Thank you. I appreciate that.
in a physically constrained world (like, planet earth?) cost of a system SHOULD be evaluated in Joules, not in USD! Storage tech should be evaluated on: #1 ratio of embodied energy over stored energy #2 efficiency: Eout/Ein and #3 max power output
I think it might be easier to convert between currencies than from joules to money.
Hi Dave, thanks for your wonderful channel. Just wondering if at your next scan of this technology you might be able to include some idea of the output numbers we might get from such systems. How would they stack up against flywheel storage systems for example?
10/10 to review past videos and current developments, most videos are lineal and this really gives a more dedicated insight on any new technologies.
No one system is going to cover all our needs but this does sound like a very simple (relatively) solution which will be one of the many we will require. It's only going to work in shafts that aren't flooded though and that may be a limiting factor.
@@goodcat1982 cost, time and waste, we are facing a £120bn and climbing bill to sort out Sellafield. The French have had to Nationalise EDF because the economics don't stack up. I am not against Nuclear but it has some serious issues that need sorting
It would seem a good plan for the sides of mountains as well. I would point out that we've been using the water cycles for energy for some time with mills that run on river currents. Love your work. You seem to do a much better deep dive into what's going on than others I've seen. Thanks.
Great idea. A variation on the funicular railways that have existed since the 1820's.
but water is free, easy to transport and heavy. and the whole thing can be done with one moving part. huge funiculars have millions of moving parts and youd need to find some niche sites with long steep slopes.
They have (or had) a project in development in California, utilizing the rails on old mining sites. Traction engines were to be used, with concrete weights on cars, controlled by grid software. Back them up the hill to increase stored energy, let them roll down to collect. I think they had already taken it far enough to determine that response times were fast enough for a lot of grid needs, besides just bulk storage. Since they were using existing tracks, installation costs were low. But even if newly constructed, the transmission line install costs would probably be higher than laying the necessary track and setting up the traction engines/ballast cars. Very old tech, but seemed simple, robust, and cost effective.
@@geoffreycahoon2410 but running railways is really expensive. you'd have to have qualified drivers in each of the trains, (sitting around waiting for peak demand) all the maintenance and checks etc. and old railways are really not that steep.. a traction engine is about 2 megawatts, power output, so call it 1.5mw electricity. Absolute peanuts. that's like $200 an hour, at peak times. if you compare it to wind generation that would be $60/h for that much power. '
@@mralistair737 These rail systems aren't generation systems, they're storage systems. Think of a weight at the end of a tether on a cuckoo clock. You use a generation system to raise the weight, and when the generation system isn't raising the weight, you use gravity to generate electricity. Saying you need a driver to run the weight is like saying you need an elevator operator to run an elevator. It's not complicated. And you can assemble a lot of peanuts, plus improve the efficiency of those individual peanuts.
Great to renew my optimism a bit regarding these projects
I think this "update" and "progress" answers some of the questions raised (e.g. the "wind" problem), but possibly only by moving to different problems. It's easy to say that building a 300 meter shaft would cost such and such moneys and produce such and such energy. So first you reuse existing mining shaft, well done, that could be cheap, they are already there. But can you scale this in any way that would have an impact on our needs? How many holes in the ground can you make without destroying water bed? I mean, speaking of which, in how many places you can make holes without it being flooded by the aquifer? Or outgasing, or shifting local weight distribution enough to cause minor earthquakes that crack house walls, like fracking or geotermal sometimes does. I think a geologist can have a field day with this one. Also, there really isn't that much energy stored in the weights, so the output (especially sustained output) numbers always look a bit meh. And I would also like to ask a mechanical engineer how realistic it is to build a resilitient system that works without constant cost in maintenance. I can get that we can build a good cable. Cool. But there's always the moving parts, jugling blocks, constant cycling of stresses.
There is no way to generate of store energy without adverse effects. In the end, our need for energy will outweigh those effects, or we'd need d to do without.
"build a good cable" "cable" in steel wire rope form will not be improving much because it's a field that's been developing more than a century for elevators & cranes. For example, there are 30 factors that determine steel rope life, all well studied. Aramid ("Kevlar") or carbon fibre products could perhaps be developed more though since safety isn't an issue (Aramid was tried for elevators but abandoned when all ropes snapped due to a mistake by engineers during testing).
From my basic understanding, we shouldn't be looking at this in isolation. This is just one way of storing energy that will fill some use cases but not all of them. I believe the future will be a large mix of renewable energy sources and storage (gravity based, flow batteries, thermal salt etc). Combining all of the options will then provide a lot of resilience which will significantly reduce the 'baseload' electricity required from nuclear and gas.
@@timjarrett8777 I agree. But will this cover at least like a bilionth of our storage needs? If not and this is like a humorous curiousity, it's maybe not worth the attention.
@@miroslavhoudek7085 absolutely, but we need to look at scale. BBC report states there are approximately 150000 old mine shafts in the UK. If we assume even 10% of these are appropriate for Gravitricity then that is 15 thousand of these small scale storage options. If we assume 2 MwH per location (which is half of the first storage system they are implementing in North Yorkshire) then that means 2 x 15000 storage, which is 30 gigawatts. I personally would call that a substantial contribution to our energy storage needs.
Great to see that work making progress in Edinburgh - In Scotland the central belt and Ayrshire used to have more than 200 collieries, and presumably many of them would have old mineshafts waiting to be used like this.
Thanks for this! I like the update videos, please keep them coming.
Thanks, will do!
Thanks for this video. Checking back on the progress of these companies is an important accountability move. In the report you cite from the Imperial College of London, the one chart you showed does not mention pumped hydropower storage (PHS). But looking more at that report, I see a number of comparison charts that include PHS and it is shown to be pretty cost-competitive with the Gravitricity proposed method. I'm a bit dubious that Gravitricity's proposal puts things deep underground, a feature at the heart of their plans. The inaccessibility adds some failure modes and repair difficulties. I'd rather bet on an idea like using rails on the side of a mountain that some have mentioned in the comments here. It would have different issues, but seems more likely to remain functional long-term compared to putting the weights deep down in a mine shaft.
Really enjoyed the revisit! I see to many videos that talks about “”cutting edge tech”” but only talk about it once.
Great where there are abandoned mine shafts. I am not convinced that is very common in the world. Good solution for some places though.
Surprisingly there are a LOT of abandoned mines in most areas (I bet there is one within 100 miles of where you live). And even if there isn't, the cost of digging a new shaft is not as expensive as people think. It is certainly less than the cost of putting up a bank of batteries.
Tons of Cobalt mines in the DRC, Nickel in other parts of Africa, coal in the US and Germany. Honestly, this solution would work better for regions that don't have very much aboveground sea level variation. If aboveground is flat, go underground. The Midwest and Great Plains of the US would be perfect for this, and I'm sure the northern provinces of France/Germany would welcome something like this. The Scandinavian countries would probably love to implement this tech
Electricity can be provided into the grid from anywhere. Even if it is a 1000 miles away.
@@SeeNickView I think the problem will be cost. Using abandoned mines saves a lot. DR is probably not going to be at the front or even middle of the pack with adoption of these technologies. France and Germany definitely have the money and will. I do not know enough about midwest USA with respect to available mines. If they do not have then another storage technology would be more applicable. Scandanavian countries have the terrain for pumped hydro so no need for this more expensive solution.
Just throwing out an idea here. Why not build a small scale gravity storage system within the hollow steel tower of every wind turbine that you construct?
This possibly will make tower unstable and prone to collapse during high wind, a special tower need to be built
Something goes wrong with either system and you have to shut both down for repair
People looking to $hit on your idea. I think it's brilliant.
Even through in theory this would work, the amount of energy that you can store in the very narrow shaft will be so little it will not weigh up to the CAPEX and OPEX. There is simply no room for a large, heavy object and the travel is limited as well (compared to mine shafts).
Because once the weight is lifted in that one tower the wind turbine would then be useless… sitting still with blades feathered for possibly days. Not to mention how top-heavy the tower would then be. Of course they could probably disengage and bypass the weight and gear system but gosh all that would be so complex and require so much upkeep.
No flies on you Dave. Another outstanding block of fascinating information
Any moving part system for electricity storage system will be riddled with lot of problems and very high maintenance costs as time goes by. Also losses in charging discharing ratio will keep moving up, like our cars drop mileage as driven more. Best will be some unique chemistry with abundant non-toxic material. Thanks Dave for wonderful follow up video.
It's a fairly simple system built from known components with known longevity. Basically a winch, a motor and some electrical controls to switch direction and possibly convert frequency between winch speed and grid frequency.
@@johndododoe1411 For the system to be robust, the parts have to necessarily be stronger and heavier to withstand wear and tear. The heavier system builds in losses during both, charging and discharging cycles, which again is a huge cost everyday, every hour and every minute. This defeats the purpose of system.
One day I had a brilliant idea, why not support a house with hydraulic jacks and use its enormous weight to store energy? Of course, you would only need to lift a house a few centimeters or inches to store enough energy for the day. But before founding my startup, I tried to get a rough estimate of those centimeters. The daily average electricity usage per household is around 30 KWH in US, or 108000000 Joules. A house weights between 100 to 200 tons, so let's use 150000 KG. Potential Energy = mass * standard gravity * height. or: height = Potential Energy / (mass * standard gravity ) height = 108000000 / (150000 * 10) = 72 m or 236 ft Energy storage using gravity? This is a horrible idea.
I think the average UK usage of electricity is 10 KWH but that's because most of our heat energy comes from mains gas at the moment. But this is a brilliant comment, really puts it into perspective the scale of the problem. Mine shafts is a good local solution I guess but hard to see how it will have a global impact. That's not to say I'm against promoting local solutions. More small hyrdopower plants would be good
How is it brilliant? The math and spelling are both dismal.
I know that the devil is in the details, but this seems to be a really good solution since it doesn't require any of the raw materials needed for grid scale battery storage so both systems could be employed simultaneously without competing for the same resources. Love it! So much better than a coal fired peaker plant. :-)
Yup got to say this one seems logical. It won’t handle all energy storage. But I imagine any one sitting on old mines will be installing these.
@@fritzstauff Well if you already have a cavern down there that you need to stabilize anyhow then it is really about running the numbers if you go for this solution or a more classical approach with water or compressed air as media.
well it does seem a great use for these old mineshafts. however, most mines, once decommisioned will flood when the pumps are turned off, greatly reducing the droplength of the weights... and keeping the pums running isnt really viable...even if somehow they manage to isolate the shaft from rest of the mine...
@@zvezdaster Great point. Any clue how much energy to run the pumps? Also I assume they only run when water is detected. Maybe a decent solar array can neutralize that energy.
@@fritzstauff well that would depend on the geological circumstances, but its safe to say that extraction has to be continuous and at a near fixed rate or level. alternating the pressure on the shaft walls is the surrest way to make it collapse. However when the shaft starts an elevated level, lets say halfway up a mountain you might get the advantage of "dry hight" that you will be able to exploit. also some of such shaft could be sunk on purpose with exit openings at the bottom in mountainous locations. Which was common in old mines in such locations to keep em viable. with modern tech this should be much easier to do..
"Here in Switzerland, where Energy Vault is situated, we have a particular high knowledge of pumpstorage optimisation. Our pumpstorage lakes in the alps typically contain tens to hundreds of millions of cubic meters and will exploit a hight difference of 500 to 1'500 m, thus storing the same amount of energy as tens of millions (!) of 20 tons concrete blocs. I am happy to see that none of the major Swiss power companies or any of its leading employees support this project."
Really interesting and balanced exploration of this issue. Looking forward to the next update
The truly interesting point of lowering a weight into a very deep shaft is that you don't need resets, which are a waste of efficiency. All you need to do is a lot of separate weights on cables, and take turns raising some weights on condition of surplus... whoever is closer to the end of their descent can get re-raised while others higher up descend if energy extraction is needed at the time. If no energy extraction is needed, raise them all. A matrix system like this will be immune to outside weather and can have a much farther travel length than any above ground suspended weight system. Multiple weights also gives redundancy to mitigate failures. Mind you I'm just talking out loud and I'm not an engineer so feel free to take a hot s**t on my point of view if it's needed.
More parallel weights mean more (or bigger) holes more cables and more generator. How could that increase efficiency? You can see in the animation that they plan to have one hole and one lifting/lowering system but multiple weights.
replace the weight with water, since its a mine shaft you can just dump the water so it takes less energy for winding /raising
@@dantronics1682 - that is hydro electricity.
@@dantronics1682 mines need pumps to drain them, else they flood
ERR why not just use water like for the last 100 years en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
I think all these systems need to be balanced with the growth in electricity demand. If a system works according to plan it will only increase demand for that resource until the price equalizes itself with other energy storage alternatives. There is no static market commodity as each part of each energy component is seeking a dynamic equilibrium with other energy components.
There is quite a bit of flexibility in this particular system that could keep costs down. Motors could be of various designs, and with a gear box would not have to be optimized for a particular speed or wide band efficiency (with the exception of very high gear ratios). Gang style cabling could allow for use of a wide range of cable diameters and grades. The ballast could be substituted with anything "heavy," even free material from around the job site (sacrificing a bit of energy density depending on specific gravity). Support structures need to be sufficient, but not standardized. Etc... There isn't a "lithium" equivalent commodity to this system that necessarily creates a choke point. That said, you are 100% correct if this system is deployed as a specific product instead of a general machine concept.
Great work, - (older woman from down under, who learnt to drive in a 1952 Ford Prefect that you had to hold in 2nd gear to keep it engaged)
When it sounds like a rock grinder switching to 1st you're supposed to say "synchroooooomesh !" to your passenger & grin.
Amazing video! Thanks for sharing your insights
Belive that was the video that got me watching your channel. Excited for this :)
Hope you enjoyed it!
I certainly did 😁
Again this kinetic energy storage building idea shows they get energy input from windmills to store for later use. It seems ok. However the process seems quite convoluted and technical, and it might not be all that efficient once the system is actually put into action. We will have to see.
CONSIDER THE FOLLOWING: A massive weight in controlled fall down a decommissioned mine shaft that has been modified with marine grade concrete 💪🏼 and flooded with water 💧 The weight falls as per usual loosing some energy due to water resistance eventually settling at the bottom. The stainless steel cable spinning up a regen dynamo system all the while. When it comes time to reset the system a portion of the used power is allocated to a simple air pump that sends air to the bottom of the shift into a high tension blatter attached to the weight. The air slowly fills into the bag until eventually it is full and becomes buoyant. The weight rises to the top and is reset. A vacuum pump is attached to the top of the sealed area to allow the weight to reset at 100%. If multiple shafts are in line the entire operation can be as smooth as a well balanced 12 cylinder I.C.E.
I like your even-handed style, and the level of technical detail. Solving how we store energy is the key to the future of sustainable energy supply, so let’s hope Gravitricity can get it right and scale up quickly via licensing etc once the full size plant is proven.
It seems to me that the gravitricity process has endless variations. How many old closed mines are in the western US where you would only need a headframe built to use them? And that same principle could be used on steep inclines with rail systems and cables. I have seen many slopes in Colorado that could be utilized to great effect. But the best solutions would be very close to the power source to keep down transmission costs. Where are the good solar and wind opportunities and how many storage sites are available nearby? Pair them up near an end user and you have renewable power 24/7 which is the stumbling block. Smaller more localized grids that can interlock is the real solution. I really like their answer for using gravel instead of solid weights as it could extend the life by reducing weight as they approach end of life means a gradual degradation instead of a sudden shut down as metal fatigues and cables weaken. Just lower the weight by removing gravel to get more years of use. Lower output is better than no output. And just think if ski slopes would build such systems large enough to provide their own power plus enough to power the towns that are nearby. In the off season they would have a source of income as all of the power could be sold on the grid. Just put them in pipelines with tracks inside and avoid the weather issues. No reason they must be totally vertical.
@ Mark I thought of the ski hill idea as well. I’m wondering about the necessity of rails though. Given enough compacting and a ‘sled’ type design at the top and bottom ends of the weights you could simply slide them up and down the hill. Miners use to ‘rawhide’ loads of ore downhill.
Most mines have a significant power requirement to run machinery, lifts, lights etc. Most of the basic infrastructure is already there. Might need some upgrades.
The problem is that people are still thinking about a grid providing energy to customers and talking about grid scale solutions. That makes these problems seem far more complicated and challenging then they will be. Decentralisation is key here. Of both generation and storage. The economics are turning against grid based solutions. The grid has to become a management system instead of a delivery system.
Making concrete adds a lot of carbon to the atmosphere. I wonder how long it would take a gravity/concrete method to make up for for all the carbon created during construction?
remember these are batteries not generators so the answer is never these work on the ends of coal plants too (they would just waste power that way though) the main benefit of batteries is to make up for lulls caused by lacks in the system (renewables not always being actively useful for generating power)
its all cheap cgi to grift taxpayer and AGW cultist money away.
A vessel full of sand etc sounds better imo, even rocks.
@@hynot9175 I think that's the plan. Build the inital concept prooving plant with concrete, and if the physics/effeciency works out, then use more environmentally friendly heavy loads.
Gravitricity evaluated at $0.05/kWh for storage is amazing. Then again the concept is pretty simple and reliable. The fact is you could find a useful location, mine a new shaft, line it with something resilient like steel sleeve and concrete, and use it for 100 years. To add to the efficiency you might even just fill your hollow weights with crushed rock from the hole you mined. The energy to mine would be massively dwarfed by the use of shaft for power storage and release nightly 365 days a year for 100 years. (Concrete dams last 100 years) I could even envision multiple weights stacked with holes for cables for the weights below them. Lift the top one, then lift the next one, and so on and so on. Obviously most of the material would have to be removed or else you wouldn't have movement in the shaft, but many more than one weight would be best.
Cheers for the heads up Boss 👍
That seems the best possible implementation of this idea. Use any cheap sand or rocks you got, the one with highest density to price ratio, put it into a huge strong steel bucket and move it up and down along a vertical hole. The main cost would be the construction of the hole, since they would need many close together for significant storage capacity. They could build the crane + generator first and use it to get all the dirt out with a different bucket for construction, make ridiculously long holes, and then reinstall the crane over the compacted dirt dug out of the hole, to gain extra length. The energy is mass * gravity * length of tunnel. The section of the cables is proportional to the mass, and its length equal to the length of the tunnel, so the amount of cable is proportional to the energy stored, and there's no way to reduce it by making it light but deep or heavy but shallow. So assuming a tunnel 4 meters in diameter with a weight 12 meters long, it's pi*2**2 * 12 = 150m^3 Filled with water: 150 tons of weight (less weight and more problems, not a good option) Filled with dry sand: 1.6*150 = 240 tons Filled with rocks (100% compacted granite or basalt, 2.6-3 t/m**3): about 400 tons Filled with magnetite: 5*150 = 900 tons A tunnel 1km long with magnetite would store E = m*g*l = 8.8GJ = 2450kWh With a low-discharge high capacity liion battery of $100/kWh, that same storage capacity would cost $245 000 It seems quite hard to me to imagine such a tunnel for such a low cost, knowing that The Boring Company was able to make their tunnels for 4M$/km A 100 meter tunnel for $24 500 seems also quite hard to do. Maybe with many close tunnels reusing the same machinery it could be achieved, but it seems hard to me. Like energy, if tunnel boring became cheaper, many many opportunities would arise.
Based
Comparing the costs of energy storage by the two batteries in question, for the energy measured in kWh, is wrong. Are you referring to a metric ton, when you write, for example, 150 tons?
@@franklins6694 Cost of energy storage has units of money / energy. I chose $ / kWh When I write 1ton I mean 1000kg of mass of material
What was the tunnel for? You mean, a hole?
Great video, Dave, and a great idea, to see how projects are getting on. Here in Saarland, Germany, there are many disused deep mines, so perfect location for energy storage. I'm sure the tech. won't cause earthquakes, all nice and smooth. However, the shafts are all full of water, sure the weights aren't bouyant, but would act like plungers. I wonder what the consequences would be? Loss of energy, fountains...
If the shafts are full of water, I wonder if they can be pumped out and used as the lower reservoir for pumped hydro?
@@ericmgodfrey Quidnet Energy wants to use such shafts to pump them full with water under pressure as an alternative energy storage system.
@@ericmgodfrey "I wonder if they can be pumped out and used as the lower reservoir for pumped hydro?" Yes they can. I'm absolutely guaranteeing that.
I like that revisited the topic again. Nice work!
On CBC Radio they call these "Previously enjoyed episodes" (usually The Debaters).
It is an interesting concept especially for long term energy storage.
I love the idea of using this system in decommissioned mine shafts. That's a great re-using of space that's just sitting there unused. I wonder if that would work in, say, old abandoned oil wells? You could set up some renewable energy infrastructure around it, like solar panels or wind turbines, and use the old mine shafts to store any excess energy.
Probably not as oil wells tend to max out at around 3ft diameter and usually more like 18 inch diameter or less and the system seems to expect a 10 ft ish shaft at the small end
@@brianzmek7272 Ah, I didn't know that. Thank you. I'll be honest, science isn't my strong suit. I love learning about it, though.
There's alternatives that use pressurized water; that might be an option. Sorta like pump-storage but in reverse. There might be other reasons why abandoned oil wells don't work though (could be as simple as no useful location).
One problem when using mine shafts is that they fill up with water (often with toxic elements). The pumping of water to keep the mines dry is often a major part of the operational cost and cleaning the water is also a major cost.
@@bknesheim Exactly, plus pumping out the water will cause the water table in that area to drop. The video shows farms surrounding it, I'm sure they wouldn't like their water table dropping and rending their current wells unusable.
Thats unique. Question can you talk about thirsty cement please 🙂.
Do you mean after it's been poured? I've got thin concrete foundation around the edge of my greenhouse, I get the feeling they draw quite a lot of water up out of the nearby ground through wicking which then evaporates, I've been considering removing the soil and painting the concrete to avoid this happening.
@@jamesgrover2005 Do you think that's what was meant? I thought perhaps they were referring to Permeable Pavement. 🤔
Glad you came back around to this concept. Thunderf00t sure did take them to task. I live in an area with abundant wind power, with the highlands of 1500ft is easily harnessed to this purpose. Installing a track that could bring a payload, up and down seems a no brainer. In our case, there is a stone guarry up top next to the windmills. The track could be used to bring loads down. Replacing fossil fueled trucks and generating power on the way down. Anyways, we are burning biomass for electricity generation here in Nova Scotia still. We are still a ways off from having such forward thinking ideas take hold.
One of the problem with mines is that they tend to fill with water and have to be constantly pumped out, which will reduce both efficiency and increase maintenance costs. I could see old strip mines being useful for this as well. An inclined plain should work just as well if slower, and those things are usually big coils going down into the ground. Not as well, as there is friction and they will collect even more water, but it could still be net positive.
That EVRC animation is so frustrating to look at, its literally being animated next to a mountain where a reservoir could be built and water could be pump to at a higher elevation for more energy potential than the building they propose. Its unreal the people making the animation didnt catch such a basic observation
Agreed, very cringe
And the wind turbines in the valley instead of on the ridge
Yes that storage system is horrible. But at this point in the American southwest pumped hydro is probably not a good choice. Being that Lake Powell and Lake Mead are at excessively low levels. 10s of millions of people's water supply is under a serious threat. Should the trends continue it is highly likely that a few cities might cease to be in the coming decades due to lack of water.
The only bad idea is one that isn't voiced. It is very easy to shoot down projects while not suggesting alternatives. Keep up the good work Dave !
Most people don't even realize that storage is an essential part of utilizing intermittent renewables. Many activists that do know tend to wave it away as a non-issue, saying the the grid is the battery. So what we need is more publicity for these efforts and more education on their critical nature if intermittent sources continue to be subsidized and installed.
Sounds like it's moving forward no matter what I think anyway. Keep it green and I'm all for it.
Great video, thanks for the update. I am an Engineer and I think the Gravitricity solution looks much more reasonable and the Energy Vault solution seems overly complex. Two questions: 1) Has Gravitricity considered a hybrid solution where large blocks are staged at ground level and attached and detached to the lift so that you could gain addition capacity without having to drill more holes and add more generators? 2) How deep will the holes be? What is the estimated capacity for a single hole?
( Sorry misspelt ) 1000 meter not meyer.
Isn't that (1) exactly what is shown in the video at 6:25.
Gravitricity's animated video shows multiple block capability: kzhead.info/sun/oMl_m8Z5e3ynZXA/bejne.html There is an online gravity power calculator at omnicalculator that can accept weight and height values and give energy in kWh. I'd include the link but KZhead doesn't allow external URLs. Gravitricity gives weights in the 500 tonne to 5000 tonne range and depths in 150m to 1500m. The max energy storage from that based on theoretical calculations is 20.4MWh.
@@beyondfossil Thanks, I had not seen that video
The Gravitricity system sounded great last year and I'm glad they're making progress. Shame that the government doesn't help and get things like this pushed along. I can see this working really well to balance the over and undersupply of wind and solar.
🤣
Jan klaas, i dont understand your emoji. What is the joke?
why should the govt gets involve?
@@dantronics1682 Because they have the funds to develop key infrastructure that helps society... Much of what we enjoy now was funded by governments.
500 tonnes at 500m is 680kWh. Peanuts
Many mines in the Netherlands have been decommissioned already and most of them are flooded. To lower weights in them seriously pumping is continuously needed. Some of the mines are now in use for diving instructions.
Just ANOTHER problem with deep storage,THANKS for pointing out, VERY important!
Glad to see this kind of videos. Keep up the good work ;-).
Are there any comparisons of these systems vs flywheels? There are a few types of non-battery energy storage proposals going around, but it's hard to find comparisons between them, just for each one against pumped hydro and lithium-ion.
i think flywheels would last not very long, i think they would get damage very often, but yah i like the idea too, every house could have one
a flywheel of that size would be very very dangerous. ... and always losing energy
@@zarthemad8386 i know, but it could be usefull and is easy to build, for safty reasons you could fill the room with water and it will brake by its self if the normal brake will fail
@@zarthemad8386 Flywheels are already in use in some limited applications for rapid response to load. These systems tend to use large banks of smaller flywheels, and losses can be minimized with vacuum chambers and magnetic bearings. These complications are exactly why I'm interested in seeing more data on them.
The problem I have with these gravity concept is you cannot control the amount of power you output onto the grid, it’s either running or not, it would also have to re-sync to the grid each time, they are interesting ideas but I see them as more edge cases for helping the grid
You can with Pumped-storage hydroelectricity which coincidentally is the best and most importantly viable option. Still, it's an edge case solution as it requires a high difference in elevation and a cheap but unsteady source of power, most prominently wind turbines.
@@rot7296 I was referring to these suspended weight systems. They are constant torque, unless they have a complex gear box.
@@reesewebster9149 And I was agreeing and also shitting on those systems.
er, yes you can! with a suitable inverter driving the load motor you can control both the speed and the torque of the system, where torque x speed = power in either quadrant
@@maxtorque2277 are you saying to use a dc motor connected to the weights then use an inverter to connect it to the grid?
thankyou, for doing this update, i quite liked both technologies in the mentioned video, i didnt see the issues with the block tower others' saw. I did however favour the mine shaft, because we need to use and reuse our resources efficiently vrs building new infrastructure when we need to keep as much land free for nature and food production as possible. I think we should start looking into building new buildings underground -at the minimum, theyd be more energy efficient and not take up agricultural and natural resources
Great video as always. Thank you.
After reviewing several hundred comments, it seems clear that gravity storage just does not have the necessary energy density. The exception of Pumped Hydro does not change this fact. Engineering expertise, time and money, should not be wasted on anything below a certain level of energy density. It will never scale.
What kind of energy density do you mean? Weight based, volume based, or something else?
@@SirCutRy I was wondering sort of the same thing. The deepest mine shaft is 1.6 miles down. There must be a theoretical limit to the maximum depth (weight of cables, etc)
If water is the exception, then I think the "exception" is not really *the exception.* Heavier materials certainly would work also. And there is something to be said in support for an elegant, interesting and even beautiful energy storage system. Huge amounts of extra money is spent on *buildings* to make them look beautiful and interesting, after all. One *interesting* idea I had was using lava from, for example, the volcano in Hawaii, funneling the lava into rail car "molds" maybe 4ft x 4ft x 6ft, and generating electricity as they rolled downhill to the ocean. Once they hit the ocean, they could heat sea water to turn a turbine to make electricity. The empty rail cars would be pulled uphill by the cars coming down. The cooled lava blocks could maybe even be sold as retaining wall blocks.
I don't want to diminish the cogency of this assertion. I don't know enough about the engineering stuff to make a good critical statement anyway. However, keep in mind, like in anything connected to economics, there are in diverse investments the cigar store model, where the return on investment may be low, or even below par, but its value comes in downturns of various kinds. These gravity projects have the nice side effect of being potentially more available for lower maintenance given the very likely potential loss of trained personnel after a population crash, in particular, which, for good or bad, seems very likely, and to a very great extent, and likely multiple times, in the next 100 years. We should, I think, be making such investments, and learning more about them, therefore, as they may end up being the only thing remaining humans can do some day.
@@SirCutRy Let's imagine a 100 ton weight 1000 meter above the surface (or along the edge of a 1000 meter deep hole. It really doesn't matter). The potential energy of said weight is roughly 250 kWh. 250 kWh is roughly how much energy a home is using every few days. So let's recap - a 100 million dollar 1000 meter tall building capable of accepting a 100 ton weight at its very top is able to power a home for a few days. Does this seem like a realistic solution?
The mine shaft version looks nice. I wonder if you could use one lift system to make use of multiple shafts to save on overheads. Assuming a site has multiple shafts in close proximity.
Mechanically switching the mechanical system between shafts while holding up the weights at the top will add extra complexity that would be avoided by simply replicating the equipment to provide complete failure redundancy.
I belive the world should open their minds to this kind of alternatives Thanks for the great video
Nice chap, like listening to him, he talks down to earth with no hype which so many seem to do.
One factor I didn't hear you mention is the round trip efficiency. Even though round trip efficiency is included in the levelized cost of storage capacity (LCOSC), I think it merits individual mention since it makes no sense to use a storage system that only returns only half or less of the energy input into the storage system. In this regard gravity storage systems have a very good round trip efficiency. The only points of energy loss is from electricity to rotation of the motor/generator to store energy and then back again to electricity along with some friction losses in the gearbox and pully system. Substantial improvements in efficiency of motor/generators larger than 500 kilowatt and the power electronics to control the motor/generator thanks to the NASA Electrified Aircraft Propulsion program to electrify aircraft from fully electric for very small aircraft of around 10 seats to a turbine/electric hybrid for aircraft for larger aircraft. Motors and power electronics currently in testing at the 1 MW size are able to achieve efficiencies of 96% and 99% respectively. That means that round trip efficiency is in the range of (0.96*0.99*0.96*0.99 = 0.903) 90.3%. Knock another percent or two off for friction in the system and you get round-trip efficiencies of 88%-89%. This is less than the 95% round trip efficiency of lithium-ion batteries, but better than the 80% for both pumped hydro or 70% for compressed air storage (assuming that heat removed during compression stored elsewhere such as in phase-change salts where it can be added back to the high pressure air before being expanded through the turbine.CAES systems without heat storage have such poor round-trip efficiency as to not be a viable large scale energy storage). And an alternative to vertical pits is to take advantage of long slopes where rail lines can be laid and electric trains with cars full of rocks or other high density material (slag?) that take power from or return power to power cables as the train is run up and down the slopes to store and release energy respectively. The advantage of course is that it doesn't need a 500 meter deep hole to exist or to be dug. This can be done with conventional trains with a locomotive with electric motor/generators providing the input power going up the slope and extracts power to "brake" the train going down the hill and a train of railcars filled with heavy stuff. This system has the advantage that it can follow a winding path to adapt to the contours of the slope in order to keep the grade within the friction limits of the wheels of the locomotive on the track. If all cars in the train had traction motors, that slope could be steeper. Alternately a cog railway or a cable system with stationary motor/generators at the top of the slope can allow the slope to be very steep. Such a cable system has been proposed by Advanced Rail Energy Storage (aresnorthamerica.com/). The system consist of a number of individual bins containing "heavy stuff" that travel up and down the slope to store and release energy. A set of motor/generators at the top of the slope drives a cable that runs in a loop along the slope. The individual bins clamp to the cable to go or down the slope. A flat area at the top and bottom allow a number of bins to be queued up on either end. The amount of energy that can be stored is determined by the total number of bins that can be parked at the top of the slope. The total power of a single rail system is determined by the maximum power of the motor/generators with the limit being the number of bins that can fit on the slope at one time. So as to keep the speed of the motor/generators constant at their highest efficiency speed, the number bins that are on the slope at a given time would likely be how the power is adjusted rather than the speed of the bins. The input and output power of the total system can be increase by putting additional tracks on a given slope. With parallel tracks, the flat sections at the top and bottom can be shorter for a given amount of energy storage for the total system. Also note that the maximum power and the total system storage capacity is somewhat decoupled and so can be tuned to a given situation.
I was also thinking of rails on a mountain slope . Probably more efficient than pumped hydro ...
@@richardstubbs6484 Exactly. Why lower cement blocks, roll the fucker. And to the marathon answer above, A simpler way to say it is every energy storage system is 100% efficient. Because the energy you are putting in is excess energy that the grid doesn't want, so currently it all goes to ground.
I think Energy Vault is claiming in the range of 75 to 80% round-trip energy efficiency, so somewhat comparable to lithium-ion battery systems. However, low round-trip efficiency may not be as bad for an energy storage concept as you are saying. As an example, a large-scale hydrogen electrolysis, storage, and fuel-cell facility e.g. in the middle of Europe could make sense, even though RTEE may only be 35%-40% or thereabouts. Here's the thinking. Wind power and PV power are becoming dirt cheap in capital cost. However they need cheaply scalable energy storage, capable of long storage time periods, to cope with intermittency and long periods of unlucky weather. So a centralized large-scale hydrogen facility could absorb excess power capacity and give 35% of it back potentially much later on. Scaling just involves more hydrogen storage tanks. So you build twice or three times as much wind and solar capacity as you need since it is dirt cheap, and rather than wasting the output as is frequently done now by disconnecting turbines from the grid or idling them, you get 35% of the excess energy back to use later. May very well make economic sense, since there would then never be times when wind farms etc are being paid not to generate.
@@erichawthorne2519 Yes, if you are going to otherwise have to divert power to a shunt and turn it into heat or shut down wind or tidal turbines to reduce supply to match demand, any round trip efficiency is better than nothing. And while the cost of wind and solar is dropping, it isn't nothing. Also different storage systems have different costs per kWh of output power. So as long as the extra generating capacity cost something, and the cost per kWh of storage capacity also varies, the round trip efficiency will always be a key factor in determining the optimum combination of energy storage methods to minimize the total cost per kWh of the system when averaged over an entire year. Another factor is the response rate and duration required of the stored energy system. In systems in the US southwest, Australia and other desert climates where solar is going to provide a large percentage of the total renewable power capacity. The energy storage system is going to need to supply 8-14 hours of power with a daily cycle. This would tend to favor systems with moderate storage capacity and fast response rate to keep the grid stable. This is likely where systems with higher round trip efficiency and power response rates in the 1 second range would likely have the advantage. This could be batteries (which don't have to be lithium-ion regardless of what Elon Musk thinks). This is also where potential energy storage would have an advantage. Potential energy storage is nowhere nearly as energy dense as batteries, thus they will have a much bigger footprint to store the same amount of energy. But they make up for that by having the energy storage medium be dirt cheap because it is literally dirt (well rock, but same difference) and an extremely long cycle life. However, for system like solar energy systems at higher latitudes where there is considerable seasonal variation in the length of the day and solar intensity, some form of long duration storage that can bank some of the summer energy for use during the winter will probably improve the cost per kWh of the system when integrated over a full year. Long term storage for seasonal shifting is where systems like power-to-fuel can be the better solution since the net kWh/m3 density is much higher and thus the very large amount of stored energy required for seasonal energy shifting will fit in a much more reasonable volume, even considering the much lower round-trip-efficiency. Hydrogen could be a good storage medium, but methanol might be better since it is a liquid at ambient conditions and so can be stored in simple tanks rather than requiring the expensive high pressure tanks for gaseous storage or complicated and expensive zero-boil off system for long term liquid hydrogen storage. Bottom line is that to optimize an electrical power system where the majority of the power is coming from intermittent sources like wind, solar, tidal, and wave will require a number of different energy storage types working together to meet the demand power on the grid that varies on time scales from seconds to months to energy generation types which also vary in output from seconds to months.
Interesting; but there will be a HORIZONTAL component there, doing NO WORK; ,how much extra loss,if any, will that be ?
well here we go again, apart from dam's and pumped hydro which we've been using for millennia, these new gravity energy storage systems seem a bit cranky, especially when there's better options using common materials for grid level storage liquid air being one of them.
Compressed air stacks up very well in comparison. Hope we get a positive update in the near future.
Depends how you look at it. Compressed air losses pressure as it runs out but a huge gravity battery weight will pull with the same force from too to bottom and you have no compressed air to handle.
Seems like a very promising idea. You would think that US coal mining states like West Virginia, Pennsylvania and Kentucky, with numerous old mine shafts, would be all over this.
Coal states are owned by coal companies who don't want renewables as it cuts into their business. Even if, in economic terms, this is better for the state's economy, the politicians are already owned by the fossil fuel industry.
I agree. The Appalachian mountains now have lots of wind turbines harnessing the wind through the mountain passes and over the ridges, with many coal mines nearby. I think it would be a great area to test this out.
Most coal is removed on horizontal galleries there are not all that many tal vertical shafts compared to the mine area. Also, mines don't stay empty. Ground water eventually getsmin and needs to be pumped.
@@phhowe17 Which would make me think that pumped hydro storage on the surface FROM the old mine shafts would be a good way to go.
@@eaglechawks3933 Yes - Rye Development is working on the 200-MW Lewis Ridge Pumped Hydropower project in a former coal mine in Kentucky
The largest grid battery, Moss Landing in California, can store 1.6GWh. This is the equivalent of 160 Eiffel towers raised to the height of the Eiffel tower.
Yeah I really think batteries just make more sense if you already have the energy in electrical form. Converting it back and forth with mechanical energy has more losses. And they don't involve massive construction projects, just mass manufacturing.
@@DFPercush Losses are not the issue, really. When you'll want to storing energy it will usually be dirt cheap (surplus solar / wind); the grid operator will be glad that you're taking it off their hands. For that reason, hydrogen is becoming a viable option despite the round trip (power grid, hydrogen, compression, and conversion back to electricity) only being around 40% efficient. Fewer losses are obviously better, but construction and operating costs are much more important, not to mention scalability. Fundamentally, Energy vault and Gravitricity suffer from the same problem: it does not scale well.
@@kaasmeester5903 Surplus solar is never going to happen, it's during the day most energy is needed so there will always be a demand for solar. Wind has more potential as it can be harnessed during off-peak times.
@@simonmoore8776 If we're going to rely on renewables for most of our power, we'll have to massively overspec it. So far the numbers look good for using mostly wind and solar, balancing with batteries or hydrogen, picking up shortfalls with hydrogen as well, and relying on gas fired plants a few times a year (or hydrogen generated from gas) for the few longer periodds of low production we can't bridge.
I liked your video from Sep 28, 2021 where retired thermal plants were repurposed to PCM plants using molten&solid aluminum. Since there is no chemistry, the block could run through essentially infinite cycles. I originally thought that it would be great for keeping LFTR plants running at peak efficiency, but now I feel that it would be easy to implement as a bridge storage system in already existing infrastructure.
FYI, kzhead.info/sun/mMiPmr2nnX6Plmw/bejne.html
I think a combination of these concepts would be the answer. Dig a series of large shafts. Line the walls with concrete, then use the same system as the mine shaft. You could build it under a solar or wind farm.
an idea I had that I was happy to see some scientists also looked at is the possibility of using skyscrapers as gravity storage. basically, lots of elevators already have energy-recovery systems built in, so use some section of the elevator and building to carry and store loads. almost all the infrastructure is already in place. may only need something like a kiva robot to move the loads. this would be ideal for big buildings that have multiple elevators, esp office buildings, since one or more of the elevators can be sectioned off (esp at night) to move the loads. (Another option is a two-story elevator, where one booth is just for loads and inaccessable to the public.) truth be told, like most gravity storage systems, I don't know if the economics of this work out, but it does seem really enticing to have energy storage built into local structures by making dual use of capital.
Skyscrapers already have enough physics working against them that adding extra strain and liability is not worth the minimum energy gain
@@thomasreese2816 It's an idea, even if they only used the energy within their own building to power computer banks and energy load. Dump an overpower to the building, and have it ballance its own power needs.
@@onebylandtwoifbysearunifby5475 The maths for this is very easy. Let's say the elevator has a rated capacity of one tonne and the building is 100m high. That equates to 0.28KWh of stored energy. By the time you've overcome frictional losses I'd be surprised if you get 0.1KWh of electricity, which will make about one cup of tea and has a commercial value of about 5 pence. Deduct the cost of all the extra machinery and you rapidly conclude it's a non-starter
@@sammason2300 Frictional losses could be replaced with magnetic forces, so could be analogous to mag-lev trains or regenerative AC motors. New buildings are being built all the time, and such ideas as energy recovery seem a good idea. Maybe a retrofit wouldn't be efficient in this case, but a central tower with a mass suspended as a counterweight to locomotion may be feasible. This tower could also be subsurface, and part of the building's cantilever foundation. The first aeroplane sucked too; i mean 12 seconds? That will never take off.
@@onebylandtwoifbysearunifby5475 Low speed generators are very big and expensive, whilst high speed generators require lossy step-up gearboxes. But my main gripe is the exceptionally low power density. My view is that gravitational storage only makes sense for pumped hydro, and only then if the natural geography already exists. This idea has been around forever. It wasn't commercially viable before so why would it be now?
I really hope that there will be at least one working facility by 2026. Let a thousand of flowers bloom!
I was completely fooled by the animation. Just thought it was made in Switzerland. You Scientists are so smart! Interesting Channel, Thanks! Just keep it dumbed down a little for people like me.
Felicitaciones. Un trabajo muy serio y moderado. Me parece que, efectívamente, la reutilización de antiguos pozos profundos es, posiblemente, la única opción válida para el almacenamiento de energía gravitatoria. A pesar de ello, intuyo que se van a desarrollar nuevos sistemas mucho más eficientes que pondrán en serios aprietos la competitividad de los sistemas de almacenamiento gravitatorio.
I wonder if old mine coal shafts could be used for this system? In Netherlands there still are several up to 1000 meters deep.
Gravitricity is designed to use old coal mine shafts that's the whole point.
@@jasonleahy5543 ah thanks, i tink i lost that in translation. ( i am Dutch) I thought they had to dig special size holes to specific depts
As the system offers long term storage with term independent losses, the tech could offer a tool for the box to cater for seasonal dips.
500 tons moving 500m vertically stores kWh. The weights need to be very cheap and you need lots of storage room if you want to cover seasonal dips
As mentioned in the video it is a short term energy storage system only. That's why they compare it with battery storage systems. Just imagine it would be lifted just once in summer and then lowered in winter again. So you earn money for just 10 minutes per year. But you still have the whole investment and maintenance cost of the facility. Of course you would want to lower your weight as often as possible. Preferably multiple times per day. And that is how they calculate these low LCOE. As seasonal storage you can multiply the LCOE with a factor of at least 300 (depending on their actual assumptions).
@@jonathanedelson6733 I didn't suggest that this technology be solely responsible for covering dips, just that it could help as can hydropower and flow batteries.
@@jonathanedelson6733 Graviticity plans to use scrap iron.
@@eclecticcyclist I was not saying it couldn't work. I was trying to describe the costs involved in making it work. Say you already have the shaft and regen lifting/lowering system, and assume that this system already makes sense for short term cycling. Now you ask 'what is necessary to get 'seasonal energy storage'. Say 'seasonal' storage means charging and discharging 2x per year. Say your shaft is 500m tall, and you use 500 tonne masses. Each mass stores 680kWh. Over the life of the system each mass cycles perhaps 100 times for this 'seasonal' usage, and thus stores 68MWh. The cost of the 500 tonne mass plus the space to store it top and bottom has to be really cheap (my guess, $5-20K) to be worth it for seasonal storage. You are welcome to do more accurate math. Keep in mind that if your 'seasonal energy storage ' is too expensive, then you are probably better off with things like larger solar arrays to provide sufficient off season production. Jon
Thx for your work! :)
There are also bridge-able, narrow, deep canyons. Also since there are surplus high rise office buildings because of telecommuting, surplus elevator shafts could be used with local solar for local night energy needs.
How do these two systems compare with the gravity-based principle of heavy wagons on rail tracks - whether they are pulled up by a motorised unit or winched up?? That system seems very safe in comparison and the only major losses would be wheel-bearing friction and any inefficiency in the power unit. The rails themselves would have minimal frictional loss and air resistance would be negligeable. All you need are some gentle hills - nothing extreme nor any major ugly features on the landscape nor the cost of excavating secure vertical shafts.
You only store / get energy from the difference of vertical height. The horizontal length of the track does not give you any benefits, so it would just require more space for the same effect and you have reduced efficiency due to the friction of the wheels.
it is already done: called regenerative braking.
@@Kiboxxx - true and that is both a given and a good reason for their relative safety! There are plant of locations globally that would suit this application without taking up valuable human or agricultural habitat. Solar panels are great users of space and wind farms have a major visual impact and affect bird-life significantly. This is not meant as necessarily the best or the only solution - just a good one to consider from the gravity perspective. Their visual impact would be quite easily dealt with by running the tracks in a small artificial "ditch".
@@janami-dharmam - So why not use it this way too?
The amount of energy you get from a system is dependent on the 1) Weight of the load being moved up and 2) the Height you achieve. if you push a load straight up (like these guys are doing) then all of the energy you put into the system will go towards building the potential energy in the raised weight (minus any system loss in the motors). But if you push the load up an incline (like on a rail going up hill) then the amount of energy you put raising the load vertically is only a fraction of the over all energy that you put into the system because you have to spend energy counteracting the horizontal force that is pulling you back the track.