Gravitricity – Fast, long-life energy storage
gravitricity.com
gravitricity.com
We are also working on a seed-round of investment. It's an exciting field with plenty of room for competition. And it's so important for fighting climate change! We need to build this asap. https://www.terramenthq.com/
I note from the website: "Our patented technology is based on a simple principle ..."
I think it's a great idea but I don't see what there is to patent or what IP they could defend ...
edit: oh sorry, I think you meant gravitricity sorry. I'm not sure what they're patenting. Also I don't think their patents are in the US.
I know Pennsylvania and New York both have 20 MW storage systems that takes up a few acres and are relatively cheap per unit of storage.
A weight you can just hang there
A basic thing to understand about electricity storage is that there are very different needs for different kinds of storage. Flywheels from what I understand are for very shortterm storage needs, i.e. balancing out shortterm fluctuations in electricity use vs. generation. But they're unsuitable for any kind of longterm storage, because they loose power over time.
In the long run with a high-solar-high-wind-scenario we'll need some seasonal storage to get us over a couple of weeks in some circumstances. This will need some storage that doesn't loose power over time.
(FWIW I have no idea if these gravitational storage techs will play any role in that, and one can be doubtful about it.)
Basically flywheel cannot store energy for a long time. It needs to be constantly used to be effective.
Megawatts measure the peak discharge rate, not that amount of energy stored.
For a fixed number of dollars of investment, gravity will store far more joules of energy.
I suspect that if the water table is high enough to cause problems, you'd do pumped hydro storage instead.
A lot of solar power is out in the desert where the water table is hundreds or even thousands of feet below surface.
And pumped storage still doesn't work as you'd need surface area for new lakes. Also, not sure if you'd want to pump out huge amounts of ground water for pumped storage, lowering the water table for everyone.
1. So the units are actually modular, i.e., not connected. Aha. If a unit jams, it's annoying but not fatal, as all the units above it continue to be usable.
2. Since the weight units are separate, then the force on the gearing (both wall and unit) is constant and thus the wear and tear is manageable.
3. The max energy stored is when all the weights are horizontal, of course. So there needs to be a transmission line built into the shaft, along with a motor/generator per weight unit. Some cleverness needed so the transmitted power is passed to (and received from) the correct units. The sliding contact where power is transmitted would also be a major possible point of failure.
4. Yeah, that's the downside of separate modular units. Each unit now needs to transmit/receive power.
5. It would seem prudent to build two or more shafts adjacent to each other. So if there is a problem in one shaft, you can go down the other and fix it. Increases reliability significantly.
6. If the units and power transmission are waterproof, water in the shaft isn't too much of an issue. You might lose ~20% of energy storage due to the buoyancy of the water, but that's it. Might save energy not having to constantly pump out the shaft.
7. Right. Definitely need a failsafe mechanism so a unit doesn't plunge down (say, when the motor/generator clutch fails) and take out the units at the bottom.
Cool idea. Good luck with power transmission.
- Regarding jams, failures, etc. These should be extremely rare, but in the event, each unit is designed to "disengage" if needed so it's just dumb weight, and modules adjacent to it will be designed to lift it. Then when the train is above ground, the unit can be swapped out for another one and repaired while the system keeps operating. - Yup failsafe mechanisms will be built in as well. - Yeah each unit has its own motor/generator. A power line will enter through the module's axle.
How about home use? Could it be used small-scale, e.g. as an alternative to Tesla's PowerPack? I've long been curious about distributed energy solutions, from heating (e.g. cogeneration / CHP, heat pumps, geothermal energy, solar+battery for off-grid energy), could this be a low-cost, low-tech, low-maintenance, low-risk alternative to batteries?
An easy calculation shows how low the storage potential is.
Lets take a weight of 500 tones of steel, which would be 63.29 cubic meters.
Now sink those 500 tonnes into a hole a 100 meters deep that would make a rather lowly 0.1362 MWh of storage.
https://www.wolframalpha.com/input/?i=500+*+1000+kilograms+*...
Not sure what the cost of digging a 100 meter hole where you can sink 63 cubic meters of steel in would be, specially since water management is needed too.
I am not convinced that it is worth it.
Lead-acid = 0.14 MJ/kg = 14.3 km
LiFePO4 = 0.58 MJ/kg = 59.1 km
LiNiMnCoO2 = 0.74 MJ/kg = 75.5 km
In the real world, you'd need the rocket itself (which in turn contains the rocket fuel) which adds weight, and you'd have a difficult time controlling power output so the rocket doesn't drift and lengthen/reduce the burn time -- but that's not the point.
The idea is that we want a unit that relates the mass of the fuel with its total energy, and one way to approach that is to consider how long the fuel could offset the force of gravity on that fuel, which gives you a cute unit of measure in terms of time.
Sometimes I wish we lived in an alternative world with fully developed nuclear power. Think about the possibilities. And no global warming! :/
[1] Not accurate, obviously.
Lots of these ideas are popping up right now because it's a very compelling idea which is demonstrated to work. And because climate change is driving massive growth in renewable energy (woot) we will desperately need massive amounts of energy storage in the very new future. The energy storage market is expected to grow massively year over year.
What does it cost to dig and maintain a 1.5km deep shaft?
I found is something around 8000-10000$ per meter. I can buy a whole lot of batteries for that.
This technology just does not scale since mgh always holds true.
Unlike flywheels where you get w^2.
Just making the wheel out of carbon fiber and making them go fast, squares the amount of energy you can store.
But mostly they won't be digging the holes, they will be using shafts left over from earlier mining operations.
https://minewiki.engineering.queensu.ca/mediawiki/index.php/...
Honestly i would have thought it to be more expensive.
At higher depths the ground pressure is enormous and you need a lot of bracing.
Then there is water management, air, transportation of the dug out material...
When there is rock you usually need blasting or gargantuan drills which i am not sure even exists in the required diameter.
https://www.storage-lab.com/gravity-based-storage https://www.osti.gov/biblio/6517343
Maybe if you are lifting the entire city. For perspective, take electric vehicles. Each moving EV is a mass being constantly accelerated at say 0.1G. So the weight in the graviticity system to power those EVs would have to be at least 10% of the mass of all the EVs active in a city.
This would be a really cool element in a sci-fi world
365000 tons × 9.81 m/s2 × 1 m = 1 MWh
which ought to at least be enough to provide short term backup power to the whole building.
https://sipilpedia.com/tecorep-system-high-tech-demolition-s...
But at that point, why wouldn't you just do a classic pumped-storage reservoir?
Furthermore, my most optimistic estimates show that underground solid mass gravity storage could compete with pumped hydro on cost anyways. One reason is that solid mass is about 2.5x heavier than water. If excavation is one of your biggest costs, this density is important.
And the much bigger issue is, you have to constantly pump out water that will inevitably fill the hole. And that only costs you money.
1) Pumps that can pump water 150 meters or a kilometer high are very expensive and require constant expensive maintenance.
2) Where will you pump the water to? Now you have to build huge storage tanks.
3) The water never stops flowing in. Sooner or later you will run out of storage space and your expensive hole will fill up with water.
There is no way, short of fusion that I know of. And fusion is not a valid answer in this context anyway (even if we had the tech for it).
Each unit can be configured to produce between 1 and 20MW peak power, with output duration from 15 minutes to 8 hours.
For reference, 20MW is ~4 large aerogenerators. A single nuclear PWR is 500-1000MW.
It can scale up to provide 1 GW of storage - enough to balance the load of an entire large city.
You'd need 50 of these installations for a single city, for 15 minutes of power, 1000 for the 8 hours.
Dig a very deep hole with a radius of 500 m, with a 500 m granite block that you can raise and lower in it to store and retrieve energy.
When the block is raised, toss trash into the hole. Then when the block is lowered to retrieve energy it also becomes the world's largest trash compactor.
Eventually, you'll get enough trash in the hole that even massively compacted you won't have enough room to make the energy storage from raising the block worthwhile.
You then have to dig another hole and move the block, leaving behind a full landfill that has more trash in it than a normal landfill of that size would have.
And it still does not answer how the construction and running costs are calculated.
Only if those are as low as claimed (which I highly doubt) something like this might be feasible.
This tech just does not scale well.
Digging holes is stupid expensive. Moving giant masses is not trivial and to double the storage capacity you need twice the weight or twice the height.
The energy density is way too low.
The only thing run by weights have been those old grandfather clocks. And even there the weights got replaced by springs and in the end batteries.
This site claims a max weight of 4.5e6 kg. Lake Powell, for example, has a max capacity of 3e13 kg!
So, SEVEN orders of magnitude less mass to move. Sounds competitive.
The country point is interesting, so the market is countries lacking topography suited to hydro plants? How big is that market really?
And considering that pumped hydro is currently the only viable grid scale energy storage mechanism (inb4 but li-on), those countries currently either 1) share a grid with neighboring countries that do have pumped hydro, or 2) forego energy storage altogether and use peaker plants like everyone else. If you do 1 you better trust your neighbors to never go to war with you, otherwise you better have 2.
So the market is: countries lacking topography suited to hydro plants, who currently share energy storage with neighbors who they don't trust, and who for some reason aren't just building peaker plants (which are essentially just normal fossil fuel power plants) and are holding out for a non-extant technology to be developed.
I'm not much of a capitalist myself, but even I can tell that that's a bad investment.
> All obvious places already have them
That is, we’re already practically at max capacity for hydro.
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
Hydro plants are built reversible whenever possible. The ones that aren't ("run of river") are that way because it was impractical to impound storage.
If a hydro site is convertible to reversible, chances are it’s been already. Most sites are not really suitable because regular hydro plants don’t need a lower reservoir or water source and so can be built in locations which don’t have one.
Meanwhile pumped hydro can be built in locations where normal hydro makes no sense because there is no natural downflow or upper reservoir e.g. Taum Sauk.
A hole in the ground can be dug up everywhere, e.g. next to each single PV plant.
But maybe capacity is only part of the story. What about locality? Distributed energy storage may not be as efficient, but it has a lot of other benefits.
There is also the fact that weights are expensive relative to the energy they can store so you have to take them directly from nature (usually via dams or pumping water uphill).
[0] https://web.archive.org/web/2016*/http://www.gcrg.org/bqr/6-...
In some places pumped hydro does make sense of course but you have to compare basically on $/kwh what is the best solution taking into account the local environment. There are no silver bullets here. Which is why a lot of places seem to be ending up with lithium ion batteries, because they are there and can be put in place without a lot of fuss or rearranging of the local environment.
This seems to be one of the key indicators of green pseudoengineering - an obsession with avoiding transporting power. Pylons work. Really. If you can get large amounts of RELIABLE renewable power/storage, with low labour and machine costs, from a large amount of cheap land, land far away from people or crops or even trees, you do not have to worry about the rest. Worry about how to get those labour and machine costs down.
Pylons may work, but you need to pay off everyone owning the land those lines go across. In many areas, they can't build pylons at all because of rampant NIMBYism.
Water is 1 tonne per cubic meter. Steel is 7.9 tonnes per cubic meter. Lead is 11.34 tonnes per cubic meter - which means that in the same amount of space, you can store vastly more energy if you use these metals instead of water.
The initial cost of set up will also vary depending on the metal you use but lead is cheap.
Also, water evaporates etc.
Cost of lead/tonne : USD 1900 (approx) Cost of Uranium/tonne: At least USD 60000 (approx regular uranium) even if you are able to source it.. and then you still have to build containment for this, get permits etc..
For that price, you could get much higher efficiencies if you went for a cheaper metal - even something like Tungsten which is extremely dense will be much cheaper.
But I assume there's structural issues with suspending a few extra tons on your structure.
ARES (rail energy storage) builds a rail-line uphill, for example. Rail cannot handle a very steep slope, but a gentle hill climb will build up potential energy fine.
In the case of vertical-based gravity storage, I'd imagine that lifting blocks to the top of a cliff (or down a valley) would be most efficient.
I mean, Pumped Hydro is gravity storage, and does just that. Pumping water up a mountain and generating energy by dropping it back down. But presumably, we don't want to use water in the Western states (where water is scarce). So Gravity-energy storage WITHOUT water is the goal.
Leading to ~10,000 feet (or nearly 2-miles) of elevation change. From there, you can dig another mile underground, leading to 1-mile (under ground), or -1000 feet elevation, to a peak elevation of 14,000.
If a tower were built on the top of the mountain: you could gain another 2000 feet or so on top: so maybe 16,000 (a 2000 foot tower on top of the mountain peak) to -1000ft (1-mile deep from the bottom of the 4000-ft elevation valley), for a total differential of 17,000 feet.
Ignoring earthquakes and other issues, of course. :-) Just purely from a hypothetical perspective: working with nature and the natural landscape seems like it'd be better than "just" digging a hole.
EDIT: Repurposing abandoned mine shafts might be worthwhile, depending how deep they are.
Gravitational potential energy is (approximately) linear in height. I say approximately because this assumes constant g (which is a good assumption when h is small compared to the radius of the earth, which it is).
And in fact, a consequence of gravity's 1/r^2 nature is that one is only subject to gravitational acceleration from what is beneath them (shells above cancel out), so mine shafts are less efficient than towers (the effect size is small to the depths we can mine).
So adding more height doesn't help, and if that height is underground it could actually hurt net efficiency.
Efficiency in this context refers potential energy stored per unit height. The field is conservative no matter what you build.
If you picture a dense weight like a cannon ball on the end of a string you're right, but if you're digging down n meters, encasing n/2 meters worth of dirt and moving it up and down the free n/2 meters of shaft, the energy storage would indeed be proportional to n^2.
I don't know anything about the field and had the same reaction you did, but considering parent is running a startup in it they're either a lunatic that doesn't know the equivalent of FizzBuzz or there's something we missed on first inspection, and we should charitably assume the latter...
The single shaft vs multiple parallel approach does seem a bit risky in the early days. If there's a 10% failure rate, and you built one shaft, that's a 10% chance of an existential threat to the company. 10 shorter shafts mean one will likely be inoperable.
Of course over the long term worrying about this doesn't make sense. Once you've scaled, 1k large vs 10k small shafts would not matter from this perspective.
Best of luck mate!
There's another thread on this comment page talking about why height is important. Please see this slide in our presentation illustrating it. https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44Yh...
There's hills somewhere in there, and those hills can form energy-storage solutions that can be transmitted across the entire MISO grid.
Bonus points: if you want to build a big battery in Iowa, you can take advantage of excess power in Iowa or Missouri. Building tiny batteries here and there will only lower your efficiency.
There's a reason why a lot of discussion here is on large 100s of MW proposals: because anything smaller won't really be a big win economically. And it shouldn't be too hard to fill up 100s of MW capacity because of the nature of our large and reliable power grids here in the USA.
For example, all the dam failures that have obliterated entire towns.
I'd rather a failure obliterated a bunch of earthworms and voles.
I expect that the voles disagree with me.
I doubt that suspending the weight is the main structural issue. It's the high center of mass when the weight is at the top.
Regarding justifying the cost--obviously depends what the cost is. If it's really just the generator, cabling etc, it might work as a short term load balancer. I saw somewhere about GE investing $X millions to smooth turbine output over 5min intervals.
Nah.
In exchange for nearly doubling the weight of the average 3MW tower, adding enormous complexity, you'd be able to boost power output to 3.02 MW for one hour.
That gets us back to the fundamental problem with gravity storage - it's all mgh. You want to store a lot of energy, you better have a shit-ton of either m, g, or h, and one of those numbers is already tough to change :)
It may seem strange to use energy density in this context but in many ways those are even worse than batteries due to the massive amount of work they require and poor scalability because of all the physical infrastructure and space.
In fact, this exact scheme looks to have been posted to HN in 2014. From my understanding they are looking to re-purpose holes that have already been dug, for the most part, which is a good idea, but if the planned prototypes are only doing 250 kW nameplate with maybe 100 KWH of stored power, there is almost no way it's going to beat a battery plant you can have more or less just built to order already commercially. And said battery plants aren't even remotely good enough at purpose for meaningful energy storage, they're mostly used for what are considered "ancillary services" in the US power markets, like eating or producing reactive power, voltage support, etc, because the modern grid scale inverters can react to grid conditions faster than grid frequencies (50-60 Hz). More rarely they might be scaled big enough to shave the peak off a demand curve for 5-10 minutes to save transmission capacity or congestion.
Keep in mind all this in happening when LNG is basically free except for the cost of moving it, so you can also put in 1-60 MW combined cycle gas plants in short amounts of time with very well understood technology and proven manufacturers.
The McIntosh CAES plant began in 1991 and from my understanding, has been widely viewed as successful. https://www.smithsonianmag.com/innovation/salt-power-plant-m...
That's 110 MWs for 26 hours. Probably not 2.8 GW-hrs of energy storage (they can't sustain 110MWs for all 26 hours), but this plant is probably GW-hr range. I'm pretty sure all of Li-Ion right now is less than 2GW-hrs for the entirety of the USA.
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The 290 MW plant in Huntorf Germany (1978) also is successful.
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There's a 2nd, 300MW+ plant (that's 300MW power for multiple hours. So near GW-hr scale as well). This is the more recent Apex Bethel Energy Center you were badmouthing earlier. Its not fully built yet, but given the history of CAES, I'm optimistic.
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There aren't many CAES plants in the world. But from what I can tell, they are all safe and successful. The one issue is that you need to reheat the air as it leaves the caverns: compressing it underground reduces its temperature. A bit of natural gas is used in this heating process, but not nearly as much as an actual natural-gas plant.
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The "Rail up a hill" project is 50MWs with 12.5 MWhr storage capacity: https://s3.amazonaws.com/siteninja/multitenant/assets/21126/...
50MWs is somewhat small, but there's something to be said about the simplicity and ease-of-deployment of rail energy storage. Those 50MWs were spec'd out with only 7 trains. It isn't too hard to imagine scaling the system up to support more than 7 trains.
I'd love to see people running more of these setups. Especially in places where DC locomotives are cheap (former CIS countries), this could be even more cost effective.
Pumped Hydro energy storage is the #1 energy storage in America, and probably the world. A single plant provides 24GW-hrs of energy storage, dozens of more energy storage than all American utility scale Li-Ion batteries combined.
Bath County is the biggest pumped-hydro battery in the USA (and probably the world), but there are dozens of pumped-hydro plants across the country.
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Turns out that all the water in a lake can hold a huge amount of potential energy through gravity: just pump it up a mountain.
Actual mechanical pumping.
Free as in money, costly in consequences. The whole point of energy storage schemes is to allow us to migrate away from fossil fueled energy.
Efficiency would be low, at about 70% * 60% ~= 40% but capacity would be huge. 1 kg of hydrogen has specific energy of over 140 MW.
We could even capture CO2 as well with that energy and make methan and use normal gas powerplants for retrieving the power :)
Just build double the number of solar panels to account for efficiency loses. Should be cheaper than grid-scale energy storage with 90%+ efficiency.
Pumped is great when you have the geography for it but most countries don't. And building dams is pretty harsh on the environment too, just in different ways than CO2 emmisions.
Germany has enough gas well storage to survive several months. This infrastructure is currently used for natural gas, but it can be repurposed for hydrogen.
I still think that commoditized battery storage will win in the end, but storage cost is not an argument against hydrogen.
For small and medium scale storage you are right. Which is why hydrogen for cars and even trucks is a bad idea.
Hydrogen at 0°C and 100 Bar (~10MPa) has a density of 8.3447 kg/m^3. It has an energy density of 120 MJ/kg. So about 33 kWh/kg. So you end up with 278 kWh/m^3.
Now of course you have to multiply this by the H2->Electricity efficiency. Let's be very pessimistic and take 0.6 or 60%, which is what a gas turbine plant can achieve today.
You end up with 166 kWh/m^3 of usable electricity per cubic meter.
One of many german gas storage facilities https://www.nafta-speicher.de/en/company has a volume of 1.8e9 m^3. That translates into 300 Terawatt-Hours of storage capacity for just this one facility.
It is not a limitation of the large storage facilities, which are just exhausted natural gas wells and work just fine with hydrogen.
The cost of outfitting one such facility with steel pipes that are not subject to hydrogen embrittlement is trivial compared to the cost for the electrolysis units etc.
Note that I am not a big fan of hydrogen at all. But large scale storage is one of its few redeeming qualities.
IIRC there was some study on doing something like that in Germany in the 2000s but I'm not finding references to it now. If you don't have to build the dam (since it already exists), pumping water back up into the reservoir is going to be better in the limited locations you can do that, and given the relatively tiny amount of energy storage vs power production I suspect the economies of scale on that won't change without a preceding sea change in global commitment to fossil fuel retirement.
There is also a better transition path to that as we already are building amazingly good gas turbines that could just as well be burning synthesized or biogas on demand from solar or nuclear over-generation. I sort of suspect that may end up being politically poisonous to the people that would normally be pushing for carbon-neutral storage options.
It would be way more than double the solar panels though. Solar generation is generally maxing at around 25% capacity factor, so replacing an existing fossil fuel generator requires 4x or more the nominal capacity in solar plus whatever efficiency loss in storage, so going with a pure solar + storage replacement of a 1500 MW combustion plant could easily require 12,0000 MW of equivalent generation.
We're comparing energy storage so no matter how much fossil fuel powerplants we replace - it would be x solar panels for energy storage with 80-90% efficiency (for example this gravicity stuff or hydro or batteries) and 2x for methane synthesis.
Reusing abandoned mine shafts could have an advantage. But there is also ample researching showing that the cost of digging from scratch is still worth it. The US Dept of energy even studied it back in the 1980s when they were evaluating underground pumped hydro energy storage. I wrote a white paper on it that's linked from here. see here https://www.terramenthq.com/uphs/
The key thing here is that adding 10x height gives you 10x more PE per weight without extra digging costs (or tower costs assuming the cost per unit of height is constant)
Here's how to think of it: by digging one deep hole instead of many shallow holes (with the same amount of digging) you get (n^2 / 2) instead of (n/2) Potential energy. The average height of all the modules is half the height of the shaft. With one deep shaft, the modules pass through the same excavated volume so they can all go deeper on average.
Edit: reviewed the Terraent slides they indeed plan to literally drive a mile long train vertically into the ground. In which case the quadratic argument stands.
At the cost of significant added complexity. It comes down to drilling cost vs installation/ maintenance cost.
But also, getting your quadratic gain on a mile deep hole requires a mile of weights to lower into it. That's a lot more above ground infrastructure than just the single shaft!
The way our design works, the modular weights are autonomous on a track. So we don't have huge cranes above ground. We just have a track above ground that also runs a mile. That track can be partly or fully buried if desired. It will be enclosed protecting it from weather, and solar can be installed on top to save real-estate.
But yes, these installations are enormous. They might cost around $150M and could provide about 200MW.
- Keeping water out of a hole is a solved problem.
- as discussed in other comments here, adding more height gives you more PE for the same amount of weight so it's a very valuable investment that pays profits over 20-100 years for your one time investment.
https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44Yh...
"We plan to roll out our technology in disused mine shafts worldwide."
There's lots of research showing how the costs work out (see my other comments here)
Pump air into a giant pressure chamber...that's also a super-deep hole with a pulley system...and the weight for the pulley is a flywheel sealed in a vacuum chamber, magnetically levitating to avoid any friction losses. Oh, and the mass for the flywheel? A bunch of batteries.
I didn't do the math but this reeks scam to me
High energy density lithium batteries are currently being commoditized. They are also increasingly able to handle many thousands of cycles. E.g LiFePo4 cells.
The raw materials for batteries are not actually that expensive or rare, so that leaves the manufacturing.
You might think that making something as complex as a battery can never be as cheap as hanging a weight from a rope. But there are examples of very complex products (solar cells, LCD displays) that became incredibly cheap due to mass manufacturing.
A square meter of solar cells, requiring extremely pure silicon and nanometer scale engineering, is now not much more expensive than a square meter of good roofing shingles.
Idea: Could elevators be retrofitted with something like this?
Then they could use/store energy only while going up, and regenerate some of it going down... and take passengers to various floors while doing that!
"The Regenerative Elevator"!
Stores energy going up, regenerates some of it while going down!
Invented here on Hacker News, by yours truly, 9/8/2020!
(Yes, I know, it's a stupid related idea! <g>. But my other related idea was more stupid, and that one was to fill up a U-Haul truck with trash, put a steel cable on it, find a hill, and use the steel cable (in conjunction with the overweighted U-Haul truck and hill!) to drive a motor/generator/winch assembly that uses electricity going up the hill, and regenerates some of it back, going down the hill... <g>)
On a serious note however (for non-passenger elevator energy storage), I think Gravitricity has a good idea, and I wish them much success with it!
I think it would not work so well because they have counterweights to make the up-down operation much easier. If you remove the counterweight, it would store energy, but be prohibitively slow when going up and probably frighteningly fast going down.
Regarding the uhaul, this is not too far off from other people mentioning driving a train uphill and letting it fall downhill to generate electricity. Interesting ideas.
> DC-driven winding-drum elevators—the leading design until the 1930s—use a DC motor in the basement that winds and unwinds the elevator’s steel cable on a steel drum, thus lifting and lowering the car from pulleys atop the elevator shaft. DC drive was the only way to go at the time for a speedy elevator, because only DC could deliver variable-speed operation for smooth starts and stops. The DC motors were also energy efficient, capable of something that has only recently become possible with modern elevator designs: regenerating power when the elevator descends.
https://spectrum.ieee.org/tech-history/dawn-of-electronics/s...
Potentially reaches a storage capacity between 1 and 10 GWh. Lifting a (huge) rock by pumping water underneath.
Obviously, this seems very technically challenging. 500 tonnes is 64 m^3 of iron. We will see if their engineering is good enough to pull off their claimed 171 US$/MWh.
https://www.metalary.com/tungsten-price/
2000 tonnes of tungsten is 60 million USD, of iron is 200k USD.
Lead goes for around $2k/ton, so this might be a more feasible compromise.
Civilian sales look at least possible, I heard of at least one sailboat with a DU keel.
A Tesla model 3, basic model (MSRP ~$38k) has battery capacity of 50 kWh, so we're talking about four Tesla 3's.
I don't think digging a 150m hole is cheaper than four Teslas - and Teslas come with the rest of the car you can use for driving.
I'm sorry, I'm not trying to be pedantic, but what does "gravity is cheap" even mean?
I agree that gravity based energy technologies are mostly junk though. There are two important factors: cheap weights and unlimited scalability. Doing something "cute" such as using a mountain side or old mineshaft is reducing the scalability.
By my calculations you would need to raise 40 tons up 3 meters to store 13.5kWh. Definitely not a home storage revolution!
Now, if the entire house was built on a lift....
You would need to raise the 40 tons up 120 meters, or conversely, you would need to raise 1,600 tons up 3 meters.
AFAIK, the most common is done around hydro dams, by pumping water upstream as a form of energy storage. The infra is already there, but it's not as efficient as systems like Gravitricity. But it costs a negligible amount of money to "activate" energy storage in a pre-existing dam.
You can look at the orgpage about these ideas https://orgpad.com/s/energiewende my father also gave a talk last week about it, there is a recording, which will be posted during the next days.
Disclaimer: I work for the small startup OrgPad, which tries to create a tool for easier decomposition of linear ideas/ content into a network of ideas/ content. An ex-Googler, Pavel Klavík PhD. describes the technology (hint Clojure and ClojureScript) and approaches behind OrgPad in a recent talk https://www.youtube.com/watch?v=4UoIfeb31UU
https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44Yh...
Your pitch deck is impressive. Good luck!
If you drop a steel weight down the same well of cross-section A and height H in the same units the energy stored is 0.08HA(D-H) MJ[2]. Again, H is in meters, and AD > A(D-H), and in order to beat compressed air 0.08H > 10, so your steel weight needs to be 10/0.08 = 125 meters long! That's taller than most of the buildings in downtown San Francisco -- and in order to get any use out of this thing, your hole should be at least twice that deep.
Of course, compressed air has its inefficiencies and complexity, but the feasibility of a metal rod even close to that long seems pretty low to me. Compressed-air caverns use as much as 7.5 MPa, but a purpose-built well could potentially go much higher. Plus you don't have to deal with the damn thing vibrating from Coriolis forces and seismicity.
Now, I know what you're saying -- you're saying, if you're so smart, why don't you do it? -- but there are simply too many huge caverns out there to even think about constructing CAES chambers. There are several GW in service today. And even with that huge resource people wonder if batteries won't simply corner the market. Storage is getting here painfully slow, it seems like, but the competition is very fierce.
1: True isothermal decompression cycles are impossible, so of course I'm approximating by using the ideal gas law.
2: (8000 kg/m^3)(10 m/s^2)/(mega = 1000000) = 0.08
One of the most prominent new startups out there exploring advanced compressed air is hydrostor. Note that they also dig underground :) https://www.hydrostor.ca/technology/
https://www.rechargenews.com/transition/liquid-air-storage-o...
To me it smells like https://www.youtube.com/watch?v=uzV_uzSTCTM and all about patents, marketing and money burning, but I don't know as much as these professors do so maybe I am wrong.
Why would this be better than a set of railway lines down a hill side into a forest pulling up standard goods carriages full of rocks?
You get a forest (which buffers runaway carriages and does all the other lovely forest things) and energy storage on the hill. All using largely commodity items and you can build it anywhere there's a spare slope.
This doesn't involve digging a deep hole in the ground and hope that the earth keeps it level.
A drawback would be the hazards that heavy tension/forces bring with them.
The US Gov has studied plenty of research showing that underground pumped hydro is cost effective and obviates the need for dams. (See my white paper here: https://github.com/syllable-hq/uphs-feasibility-study)
So startups like Gravitricity (and Terrament, my startup) are innovating on what is already well-researched territory.
It's not just not true, it's like, obviously not true. Anybody that took high-school level physics understands gravitation potential energy and it's not a huge leap from there.
UPHS has never been fully built to my knowledge, but it's been well studied and quite a few projects have tried to get funding for it.
U.S. DOE research from 1984: https://www.osti.gov/biblio/6517343.pdf
Projects trying to work on this: https://utilitymagazine.com.au/pumped-hydro-storage-the-futu...
Other proposed projects: - https://www.waterpowermagazine.com/features/featureinvestiga...
- http://www.eaglecrestenergy.com/project-description.html https://www.osti.gov/biblio/6517343.pdf
Climate change is urgent and we need all hands on deck to build as fast and as cheap as possible. May the best designs win asap in this fight!
A lot of the cost goes down when the reactor isn't a practically one-off build, and when you can for example use prefabricated components to "assemble" a power plant quickly.
Some designs go even further, and have power blocks that are essentially something you slap on large railcar, including option that instead of refueling you send back the module while the vendor sends you a freshly-fueled one.
That means that the theoretical maximum is 50x (!) less than 1 nuclear reactor can do in 1 hour (1000 MW for 18 months or 13 140 000 MWh). Put it differently, you'd need to dig 50 of these to output the equivalent of 1 nuclear reactor (and nuclear plants have 2 or more reactors) for one hour.
That's also assuming digging a hole this deep in a stable manner.
[1]. https://www.wolframalpha.com/input/?i=5000+tons+*+9.8m%2Fs%2...
Also, I would assume that 50x of these wells is cheaper than 1x nuclear (especially operational costs). But again, not in the same category.
If it does work, I would imagine the Boring company would be all over this.
and prone to Earth quakes, I would assume.
https://www.quora.com/What-is-wrong-with-Dr-Mills-Hydrino-Th...
"We'll see?" This guy has been milking this since 1991. As Aaronson's article so sardonically points out, there's nothing there to debunk. Every claim that can be made about the "hydrino" can be made with equal weight about the "doofusino," so what's the point?
He's had three DECADES to set up any kind of publicity stunt or get the attention of any number of existing billionaires or just scrape together the resources he needs to build the no-shit this-changes-everything prototype. Or maybe Elon Musk and everyone who knows him is an idiot without vision who think they can make a buck on solar when this guy's world-changing technology is right around the corner this time for really real I promise.
[1] https://en.wikipedia.org/wiki/Brilliant_Light_Power#Criticis...
As I said, Doofusino doesn't NEED to be a rebuttal. THERE IS NOTHING HERE TO REBUT. The proof is in the pudding and Mills has no pudding whatsoever. All he has are his claims about all the magical fairytale things his wonderful technology can do.
I don't care if he says it can braid my hair and create free cheerios on demand because he finally found the right alloy to use in his psychogravitic negamatrix. It's not real until there's proof and he hasn't offered any in thirty years. See you in another thirty, I guess.
There are many experimental papers that show hydrinos exist and have the properties predicted by Mills classical model of the hydrogen atom. https://brilliantlightpower.com/ has many videos of working prototypes producing excess energy. Dark matter exists and interacts gravitationally like baryonic matter but is electromagnetically inert like hydrinos are predicted to be. The expansion of the universe accelerates (Mills predicted in the 1990s). Etc.
Nobody has ever created hydrinos. They are not real. If they were, he would be selling barrels of hydrinos. He will never sell one single hydrino. Because they are not real.
The fact that you continue to sneer tells me you have not seriously examined his claims and merely rely on biased secondary sources. Yelling rubbish more loudly does not an argument make.
Also this does not seem very convoluted, it's using an electric engine pretty directly. If you are actually boring straight down it seems like the failure modes are pretty okay.
Why? Just build more. Keep expanding capacity so the base load covers the peaks and thensome. Push the price of electricity down while keeping it carbon-neutral and crush competition. Get everyone 2c/kwh power. Wouldn't that be more fun?
> the waste problem.
Ehh, it's well managed in Canada and France, I don't see why Americans can't handle it. Just keep it away from fault lines, right? I bet some of those old missile silos would be perfect.
And please enlighten me, how does France manage their nuclear waste problem?
And those hard-to-use fractions aren't going to be a problem for long, pretty sure they are considerably shorter-time risk than the timeframe for cleanup of WW1 battlefields in France (which currently stands at around 700 years).
Demand response, frequently promoted as a way to increase penetration of intermittent renewables, can also be used to reduce the cost of a system composed on high capital cost, low marginal cost dispatchable generators like nuclear. Charge the EV's and run heat pumps to warm thermal storages during the night when demand is lower, say.
Also, it means you have to run your reactors regularly at below 100%, so you still can react on additional demand, which increases further the cost of a very expensive technology.
IIRC that 5% figure I read was wrt EPR and AP1000, presumably older generation LWR's are slower, by how much I'm not sure. France has run older generation PWR's in load-following mode for decades, but I'm not sure which ramp speeds they achieve; fast enough in practice in any case it seems. CANDU reactors in Canada have steam bypass and can apparently ramp at >10%/min.
In any case, my point is that ramp speed is in practice not a technical limitation. Of course you want to run a generator with high capital cost but very low marginal cost at 100% as much as possible, but if you now and then need to ramp (say, if the wholesale price goes negative) you can do it.
> Also, it means you have to run your reactors regularly at below 100%, so you still can react on additional demand, which increases further the cost of a very expensive technology.
To be clear, I'm not advocating a 100% nuclear grid. I'm just pointing out that the "nuclear can't ramp and is thus unsuited for the grid of the future" isn't correct. In particular, I think solar and a moderate amount of storage is very well suited to cover the daily variation in many parts of the world. I also think that dispatchable low-carbon sources (which could be hydro, or nuclear, or something else like geothermal where available, CCS where geological formations for storing CO2 are available, etc.) have a role to play in least-cost deep decarbonized grids. See e.g. https://doi.org/10.1016/j.joule.2018.08.006
AFAIU France primarily uses reactors which are earlier in their fuel cycle for load balancing, and ones which are near the end run with a flatter profile.
Didn't know about specific as it's not really my area, but would running a PWR with very high enrichment level (AFAIK some designs use 93% U-235) allow quick spin down and spin up?
Well.. there are a lot of factors in a reactor design affecting the ability to increase or decrease power quickly. Geometry, fuel/moderator ratio, fuel density, burnable poisons (for flattening the reactivity swing over the fuel cycle), amount of control rods etc etc. Fuel enrichment being only one thing, which in turn affects other things as well (e.g. reactors using highly enriched uranium tend to use different fuel designs than low enriched fuels).
But yes, military reactors for navy ships obviously have very different demands on them than civilian power reactors, and are designed accordingly.
And yes, while US navy reactors use 93% enriched fuel, it's not necessary, e.g. French and apparently Chinese submarines use low enriched fuel (7% for French).
Which "funnily" enough makes it so that the more dangerous reactors remain in use for longer, as the new designs aren't built, despite huge safety improvements (even if you go just for late 1970's self-sealing molten lead/bismuth reactors).
Overcapacity is a problem, especially for low-enriched reactors, but that's why it shouldn't be the only answer.
If you don't know anything about how a grid functions then maybe you should stop shoehorning a single solution to solve every problem when everyone is already aware that a large array of different technologies is necessary for a modern grid.
Energy storage has also been planned for nuclear power plants as starter and emergency power.
Regardless of your thoughts on Nuclear, this is clearly a much simpler device. Also, I suspect the failure modes in this are pretty boring ...
Most people just don't want to accept the fact that when it comes to energy density, nothing compares to nuclear. Nothing even comes close.
I do have high hopes about fusion and molten salt thorium is also up there as something I'd like to be further explored.
But currently nothing up and coming seems to compare to nuclear.
I just did a quick skim of the wikipedia page of that 'hydrino' stuff: https://en.wikipedia.org/wiki/Brilliant_Light_Power#Criticis....
I'm not an expert, but reading those criticisms makes me think this is nothing more than a money grab scheme without delivering anything usable for the past 30 years.
Also, this thread: https://news.ycombinator.com/item?id=24423103