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Gravity Energy Storage: Alternative to batteries for grid storage

133 points by headalgorithm 6y ago

dzhiurgis 6y ago
Then there’s compressed air under water storage. There have been trials but roundtrip efficiency isn’t great IIRC.
- huhnmonster 6y ago
  There are a bunch of other technologies as well. Huge flywheels [1], which are supposed to be used for very responsive power needs (i.e. grid stabilisation), trains loaded with weights which get pulled up a mountain and released [2], redox-flow batteries and so on. [1]: https://www.energydigital.com/smart-energy/worlds-largest-flywheel-energy-storage-system https://www.energydigital.com/smart-energy/worlds-largest-fl... [2]: https://aresnorthamerica.com/ https://aresnorthamerica.com/
  - timr 6y ago
    Also molten salt: https://www.solarthermalworld.org/news/molten-salt-storage-33-times-cheaper-lithium-ion-batteries https://www.solarthermalworld.org/news/molten-salt-storage-3... People talk about making "personal" molten salt units for the home, which seems a little terrifying.
    - jandrese 6y ago
      I wonder what the local zoning commission has to say about the guy building a personal toxic metal death ray in his backyard?
      - peteradio 6y ago
        That is why I will never live in a HOA neighborhood.
        jandrese 6y ago
        The zoning commission runs at the town/country level, so even if you don't have HOA busybodies you still need to get the permits. The law is usually worded such that if you're doing something abnormal you don't get a "there is no rule that says a dog can't play baseball" loophole, you instead have to bring it up before the county council and justify the project.
  - taeric 6y ago
    Seems the train idea is similar to the old counterbalance system for trollies in Seattle.
    - imtringued 6y ago
      Hydro pump storage works because you don't have to pay for the weights. Building a train is worse than batteries in terms of economics.
- jandrese 6y ago
  Usually when you see compressed air storage solutions they're talking about plugging up an old mineshaft or cave and pumping air in. Doing it under water would seem to have some advantages, like a less catastrophic failure condition and having a ready place to sink all of the heat. Downside is that the water would cool the air much more effectively than solid rock so you lose efficiency.
  - jayd16 6y ago
    Are there any combination solar, hydro, fracking/oil plants? I'm joking but not entirely. Not sure how much water would fit in an oil field but it seems like a natural reservoir one could use.
    - jandrese 6y ago
      The trick would probably be getting your energy back after you've pumped the old oilfield full of water. Most oil fields aren't gushers, especially after they've had most of the oil sucked out of them.
- ed25519FUUU 6y ago
  A lot of these storage technologies have been around for a long time (I have a "Nature" magazine from the 60s that discusses storing excess energy as wind in salt mines and in lakes. This was the 60!). What people underestimate is just how much energy we need to store. Lakes won't do it and neither will salt mines. Gravity certainly won't do it. We need to think much BIGGER.
robbrown451 6y ago
Seems like they'd do it on the edge of a natural cliff to avoid having to build a tower, or maintain an abandoned mineshaft. There aren't big cliffs everywhere, obviously, but where there are, seems like an economical option.
- wedn3sday 6y ago
  Cliffs tend to move a bit, falling slowly over time. There may be more stable cliffs to use, but the ones near where I grew up on the coast have a fairly steady fall rate (a new cm/year).
- imtringued 6y ago
  Drilling holes for energy storage isn't economical at all. Gravitricity is never going to work on a large scale.
  - jeffbee 6y ago
    Yeah, don't do the math on their outrageous claims. Excavating a hole in the ground that's 150m across and 1000m deep represents a monstrous up-front investment of energy. Not to mention the small matter of their 8-megaton piston costing half a billion dollars.
sliken 6y ago
Seems a bit limited and expensive. Pumping water uphill when there's a surplus seems like a no brainer, doubly so when you are already using hydro and hydro production is already tied into the grid. Seems like pretty much the only way to cost effectively bank substantial amounts of energy for 6 months.
- Pfhreak 6y ago
  It's good but not perfect. Dams require a reservoir, which takes land out of use and changes the flow dynamics of a river. It can interrupt wildlife patterns both up and downstream. It introduces some risks of dam failure, and decommissioning a dam requires careful management of built up sediment. Flooded organic matter anaerobically produces methane. It also requires significant space and particular configurations (must be on a river, must be in a hilly or mountainous area, etc.) It also isn't necessarily scalable -- how many more dams can we build? You can build a crane and blocks or drill a big hole in lots and lots of places. So yes, pumped hydro is better than fossil fuels. But also it's not something we can consider to be the ultimate solution to the issue of storage. By all means, let's use it (and we do use it today), but not stop there.
  - sliken 6y ago
    Dams are expensive and have significant side effects. However the duty cycle on a dam is pretty low (they rarely run the turbines at 100%). So there's substantial additional capacity that could be had by pumping water upstream whenever there is a surplus of power.
  - deepspace 6y ago
    I am not sure that this form of storage is comparable to a traditional dam. The fact that blocks of matter need to be physically moved by a crane severely limits the total capacity of the system. The most dense metals are only about 20x as dense as water, so we are not talking about a huge volume of water. The equivalent mass of water can be stored in a tank - no dam required and moved through a pipe - no river required.
    - 6y ago
DeRock 6y ago
Something that doesn't often get brought up in these energy "storage" discussions is the potential for duty cycling existing generation to time shift the duck curve. Eg. California (large solar generation) shares a grid with Washington and British Columbia (large hydro generation). When the sun is shining, hydro reservoirs can be filling, as solar is meeting the demand. When the sun goes down, hydro facilities can duty cycle on and drain the overhead. This requires some flexibility in reservoir levels, as well as the ability to stop/re-spin turbines on a daily cadence. But you eliminate all of the efficiency losses with schemes such as pumped storage (though gain some transmission losses due to the increase length of geographic arbitrage). The same opportunity exists on the East-West axis. The sun is still shining in California after its set on the East coast.
- abfan1127 6y ago
  Its my understanding that some hydro facilities do this. One issue I can think of is the losses of transmitting that much electricity from 1 area to another (1000s of miles away). the losses of transport coupled with the losses of "storage" and "generation" make it more expensive. I don't know the actual costs, just ideas I think about.
  - ebiester 6y ago
    The losses of transport are relatively small, smaller than would be expected: see http://insideenergy.org/2015/11/06/lost-in-transmission-how-much-electricity-disappears-between-a-power-plant-and-your-plug/ http://insideenergy.org/2015/11/06/lost-in-transmission-how-...
  - sdepablos 6y ago
    Not so much with ultra-high-voltage lines. China has been doing it for years because of the really long distances between electricity production and consumption. https://en.m.wikipedia.org/wiki/Ultra-high-voltage_electricity_transmission_in_China https://en.m.wikipedia.org/wiki/Ultra-high-voltage_electrici...
- arawde 6y ago
  It was my understanding that this is more of a seasonal thing than on a day to day basis. That is, during the summer, southern California uses a large amount of electricity for climate control, and so power is transferred along the Pacific DC intertie in a north -> south direction. In the winter, electricity usage in the north is devoted to heating, whereas in the south temperatures are mild. The result is that power is moved back up the intertie from south -> north. In the spring, snowpack melt refills the reservoirs in the hydroelectric system, allowing it to be ready to provide power to the south again once temperatures start to climb.
huhnmonster 6y ago
This article surprised me since funding came from Softbank and not the state government as most does IIRC. Where I see the problem with all these forms of energy storage is that there is no one efficient approach (yet!) and innovation will come mostly from government funding, so governments decide what they see as the best opportunity. This seems like its pretty much hit-or-miss and betting on the wrong thing will arguably speed up the development of it but at the same time, we might end up at a point we could have reached quicker and cheaper had we used a different technology.
amelius 6y ago
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit... > Pumped storage is by far the largest-capacity form of grid energy storage available, and, as of 2020, the United States Department of Energy Global Energy Storage Database reports that PSH accounts for around 95% of all active tracked storage installations worldwide, with a total installed throughput capacity of over 181 GW, of which about 29 GW are in the United States, and a total installed storage capacity of over 1.6 TWh, of which about 250 GWh are in the United States.
nabla9 6y ago
This solution competes against short term storage, (typically tens of minutes, up to hours). Flywheels are commonly used and efficient energy storage for short term. Pumped hydro mentioned in the article is good for long term storage > weeks, months, even seasonal.
fullstackchris 6y ago
Quite a while ago, I thought up of what I though would be a simple system that has a net positive energy output (it already sounds ridiculous, I know, but I just can't see what concept I am missing) that follows this principle. I finally have a relevant article I can share it with here on Hacker News! The gist of the system is as follows: 1. let a hanging weight freefall under gravity to spin a generator. (via a pulley connected to a chain drive or gears etc) 2. The power generated by the generator is stored in a battery 3. The weight is pulled up very slowly back to its drop position using a DC motor that uses power from the battery (the DC motor could be actually the generator itself but likely a specially tuned one for slow lifting will be better) 4. Repeat. The system lifting / reset process requires less energy than the energy produced by the drop, so there will slowly be a net buildup of charge in the battery. Super simple numbers example: PE of a 100kg mass falling 2m: PE = (100kg)(9.8m/s2)(2m) = 1960 J The mass falls at a near g acceleration - I know it won't be exactly g because of the moments of inertia of the generator and generating drive apparatus - but it would be quite close to g. At this acceleration the mass falls for ~0.63s, so the theoretical max power we can hope to extract using the generator is: P = W / t = 1960 J / 0.63s = ~3000 W Even if we consider a horrible electric generator with only 50% efficiency (just to be even more conservative and fair, and to capture any losses we've forgotten), we should hope we can get at least 1500 W from the drop. The "trick" of mine is mentioned in that very slow "reset time" for the weight. That is, use a DC motor to pull the weight up, but give it a long time to do so. In this way, the power used to lift the weight back up to its dropping point is much less than what was produced by letting the weight fall and spin the generator. Using the same numbers from the example above, if we let the lift time be, say 20 minutes (=1200s) and since we know the W of the lift is the same as the drop PE, then the power needed to lift the weight back to its original drop point is: P = 1960 J / 1200s = 1.63 W That means we produced about 1500 W (even with our crappy 50% efficiency generator), and only need ~2 W to reset the system. Assuming you put a nice battery between the generator and the dc motor - you get a net positive storage of energy over time. Does anybody see any glaring issues with such a system and my analysis? I know when anything in physics appears to be a free lunch, something must be wrong. (Though if you consider these long 'cycle' times, it isn't really a free lunch) Perhaps I don't understand exactly how DC motors / generators really draw or produce power in the real world - Physics 101 was a long time ago for me :) The trick to my proposed system, which systems like those in that of the linked article don't do, is my slow reset time. Obviously not feasible for massive applications or load balancing, but a net power storer nonetheless.
orange_tee 6y ago
These ideas are cute but they lack interest from major players. In Europe it seems the big players are betting big on hydrogen. The EU is looking to convert all gas pipelines to be hydrogen proof and for new pipelines to also be hydrogen proof. I know Japan is also very bullish on hydrogen infrastructure. With regards to energy storage, it seems to me the solutions that are most likely to be widely adopted are: batteries, pumped hydro, and hydrogen and the many synthetic hydrocarbons that can be obtained from it. Besides that, improvements to the energy grid can be made to eliminate the need to store as much energy in the first place.
- blue_box 6y ago
  Could you share your resources, please?
  - orange_tee 6y ago
    I got it through word of mouth from people involved in projects, but I did a Google search for you and came up with many public trusted sources: https://ec.europa.eu/info/sites/info/files/hydrogen_europe_-_vision_on_the_role_of_hydrogen_and_gas_infrastructure.pdf https://ec.europa.eu/info/sites/info/files/hydrogen_europe_-... https://hydrogeneurope.eu/hydrogen-storage https://hydrogeneurope.eu/hydrogen-storage https://www.euractiv.com/section/energy/news/gas-grid-operators-unveil-plan-for-european-hydrogen-infrastructure-backbone/ https://www.euractiv.com/section/energy/news/gas-grid-operat... Were we stand in 2021 is that policy is already on the books and funds being distributed for these projects. So hydrogen ready pipelines are definitely getting built. Whether they will prove useful remains to be seen.
    - Hypx 6y ago
      This being explored in the US too: https://www.energy.gov/sites/prod/files/2019/03/f60/fcto-satyapal-verdexchange-jan19.pdf https://www.energy.gov/sites/prod/files/2019/03/f60/fcto-sat... I suspect that utility companies in the US are only a few steps behind European utility companies. This should be a global thing before long.
OliverJones 6y ago
The grid-nerd term for rapid-response capacity delivery is "frequency control ancillary services." It's a real problem in times of heavy load. If a local grid's frequency drops below nominal (60Hz US, 50Hz elsewhere) the regional grid has to disconnect. So without rapid-release stored energy a power generating org has to fire up extra capacity and keep it running to cover transients. Old missile silos might be interesting. But most of them are far from population centers. Pumped storage is still great given the right geography. Northfield Mountain has been running flawlessly for almost half a century, storing about 9 GwH. https://en.wikipedia.org/wiki/Northfield_Mountain_(hydroelectricity_facility) https://en.wikipedia.org/wiki/Northfield_Mountain_(hydroelec... But it takes about ten minutes to spool up. And the fish and boaters in the nearby Connecticut River definitely notice it.
- Florin_Andrei 6y ago
  When the frequency of the generator is not tied to a mechanical property of it (like the spin of a turbine) - e.g. when the source is solar panels and the AC is produced via an inverter circuit, what are the remaining frequency-related issues? I imagine with solar the generator can pretty much pick any frequency it wants, it should not be influenced by load, it could simply stay in sync with the grid no matter what, is that right?
  - bob1029 6y ago
    The problem with inverters is that they have no inertia to impart on the grid. When you have a gigantic spinning turbine, the amount of power it takes to change its speed is immense. This has huge implications for grid stability when we are talking about renewables. The resolution for this is something called a synchronverter: https://en.wikipedia.org/wiki/Synchronverter https://en.wikipedia.org/wiki/Synchronverter
  - beckingz 6y ago
    Most cheaper solar panel inverters are synced to the grid and require the external 60hz wave to output power, resulting in solar panels that will not provide energy without being connected to the grid.
baybal2 6y ago
Excuse me, but the company in the article was debunked as pretty much a scam. You cannot physically make that work economically.
- imtringued 6y ago
  Yeah all of them are questionable. The only one that has even a tiny chance of succeeding is the piston idea. You don't have to pay for the weight and you only have to cut the circumference of the piston out.
  - Animats 6y ago
    The piston idea has a problem. Rock isn't like that. Natural rock does not often come as one big solid piece. It's more like a pile of boulders of different sizes. There are cracks, underground water, rubble, etc.
- pipermerriam 6y ago
  Can you provide a source for this?
  - p1mrx 6y ago
    Here's a sarcastic YouTube video, at least: https://www.youtube.com/watch?v=NIhCuzxNvv0 https://www.youtube.com/watch?v=NIhCuzxNvv0
- jussij 6y ago
  Based on the video found on the Energy Vault web site they seem to be doing some serious engineering in building their prototype: https://energyvault.com/commercial-demonstration-unit/ https://energyvault.com/commercial-demonstration-unit/ As to whether it works, I guess they will know once they've complete the prototype build and done some testing.
  - baybal2 6y ago
    Just do the math. Total amount of energy they store is no more than a TEU container worth of lithium batteries, or few dozens of modern flywheels, or hundred so of plain steel ones.
WalterBright 6y ago
By far the most efficient grid "battery" to reconcile fluctuations in demand & supply is to have a realtime price for electricity. Water heaters, for example, can be equipped with an internet device (at last, a reason for an internet connected water heater!) to monitor the price of electricity and shut off the heater during price spikes. Some "batteries": 1. hot water heater 2. HVAC system 3. EV charging 4. Some lights (like yard lights) can be dimmed or shut off during rate spikes 5. Same for street lighting 6. Computers can switch to low power mode 7. Refrigerators 8. Dryers This is far better than the "rolling blackout" bureaucratic solution. Note that the pump price of gas varies daily. This is the market reconciling constantly shifting supply & demand, and it works great.
- choeger 6y ago
  Heating water with electricity is the literally last thing we should do. That is, once clean electric energy is cheap, we can do it. But we are not there yet. Hence we should at least use heat pumps or similar technology.
  - WalterBright 6y ago
    Meanwhile, there are hot water heaters in use everywhere. That isn't going to change anytime soon. Besides, in many places during peak solar there isn't anyplace to dump the electricity. Electric hot water heaters can take care of that problem, as water will stay hot in one for a couple days (I know from experience).
    - dharmab 6y ago
      A heat pump can approach 500% efficiency and is powered by outdoor ambient air (using direct heating as a fallback). https://www.youtube.com/watch?v=-vU9x3dFMrU https://www.youtube.com/watch?v=-vU9x3dFMrU
      - WalterBright 6y ago
        It still uses electricity, and can be shut off during electric rate spikes, acting just like a "grid battery" without the expense.
ogre_codes 6y ago
I so hate IEEEs broken web-site. Every time someone links to this site I'm irritated by the broken scrolling.
blackrock 6y ago
I wondered if you can use hydrogen instead. Use solar/wind to crack water into hydrogen and oxygen. Compress it to liquefy it. Store this in some temporary storage tanks. Then when you want to make electricity, pipe the hydrogen and oxygen into a fuel cell. Then electricity and pure drinking water comes out. Then you can bottle the pure drinking water and sell it locally for an additional profit. I haven’t analyzed the cost for all the technology and infrastructure. But this idea seems mechanically simpler than the gravity brick idea. Additionally, you can transport the LH and LOX, to other areas if necessary.
- imtringued 6y ago
  Hydrogen works despite the inefficiency because there is an existing gas infrastructure ready to be converted. If we had to build everything from scratch we would be desperate for other solutions.
AndrewDucker 6y ago
If I've just done my maths right then an AA battery is enough to lift 360 metric tons up 1m. Edit: out by a large factor. Should be that many kg, not tons. So lifting trains into the air is going to have its work cut out to match plain old battery technology.
- wmwmwm 6y ago
  I think that’s about a 1000x overestimate - about 1Ah * 1.5v * 3600s = 5400 J - that’d lift 540kgs up a metre (Maybe double that for an alkaline one)
  - AndrewDucker 6y ago
    Thank you.
- kmm 6y ago
  An AA battery holds about 4 watt hours of energy, or 14.4 kilojoule. Dividing by 9.81 m/s^2 times 1 meter, yields about 1.5 metric tons. Not quite 360, but still quite a lot.
thoughtstheseus 6y ago
As an alternative to storage working with large industrial users to adjust their electricity demand in real time can help mitigate some supply/demand imbalances.
flaburgan 6y ago
I always had the feeling that with electricity consumption, smaller is better. What if we all add a few blocks in our corridor which would be lift up during the night and bring back energy during the day? This would get the curve plane and we can follow its usage closely, wanted to reduce our own bill...
- lovemenot 6y ago
  Your intuition is probably not right in this case. Gravity is actually very poor for energy storage. If your home system could lift 100kg over 10m it would store only around 3 Wh. The advantage of these industrial systems is that mass scales by volume, so a little more surface area can deliver a lot more potential energy. And of course the capital investment is much more economic on a centralised system.
  - flaburgan 6y ago
    But isn't that efficiency directly depending of the system itself? I mean the performance of the dynamo which would create the electricity when the weight goes down
    - lovemenot 6y ago
      It's not a question of efficiency. My figures assume 100%, which is certainly too optimistic. No, it's about the energy in any reasonably home-sized system is way too small. About one or two AAA batteries' worth. Though industrial-sized systems can be much better, they too are under-powered, against our needs. Except pumped-hydro.
rocqua 6y ago
https://www.wattisduurzaam.nl/27493/energie-opslaan/reservoirs/crazy-storage-tower-energy-vault-picked-by-world-economic-forum/ https://www.wattisduurzaam.nl/27493/energie-opslaan/reservoi... This is a critique of these ideas. The main points are: - Lifting speed needs to be 40 kph - Minimal height of lowest stacked state limits storage
boringg 6y ago
Soo many different better options. As a member of the energy storage industry I give this a hard pass, this is also old news, costly and not multi functional. Pumped storage makes sense in some specific cases. Look to lithium ion for short time high cycle/fast response, vanadium flow for long duration (expensive currently, large sites), hydrogen potentially and fascinating long duration start up out of Massachusetts (forget the name right now). More tech will come down the pipeline soon. Compressed air possibly but hasn’t really progress much over its existence so far (geological restraints too). My two cents
- rossjudson 6y ago
  The new thing I read there was the use of old abandoned mine shafts, providing up to 1km of vertical distance with a 5000 tonne mass. There are a lot of abandoned mine shafts. Does it work?
- 1958325146 6y ago
  I bet the Massachusetts one you are thinking of is Ambri, which is making a liquid metal battery. https://ambri.com/ https://ambri.com/
  - boringg 6y ago
    It was form energy - will read into ambri though. https://formenergy.com/ https://formenergy.com/
mikewarot 6y ago
I think putting tanks in the bottom of abandoned mineshafts, and filling them through positive displacement pump/motors is the way to go. You get energy as the water goes down, and use it to pump the water back up. The costs are the mine, and the maintenance required to keep the lift working, and the whole thing from collapsing... and two tanks / pools.. one at the bottom, one at the top, piping between the two, and a positive displacement pump, with a motor/generator. All known technologies.
- grizzles 6y ago
  This won't work because of erosion.
  - mikewarot 6y ago
    Erosion of the pump?
  - lxmorj 6y ago
    Nah man you make tanks down there
    - grizzles 6y ago
      There is a reason no one has tried it. What you are proposing would be very expensive. You have to transport the water to them. The large tanks (eg. 10M litres) require ongoing maintenance. You must make sure they don't leak, evaporate too much, make sure the ground in both places won't settle, worry about seismology, etc.
kumarvvr 6y ago
Energy Density of Gravity storage is too small to work with smaller installations. Investment is high. The future of renewable energy is obviously Solar PV, with Wind and other offsetting to some extent, but Solar is predictable, cheap to build and easy to maintain. I really wish there was more thrust into carbon capture and conversion to fuel with Solar power.
8bitsrule 6y ago
The article mentions potentially lifting an 8 million metric ton piston. Let's see: A weight of 8 x 10^9 kg raised 100 meters = a potential energy of 8 x 10^11 kg-m PE x 2.724 x 10^-6 kWh / kg-m = 2.18 x 10^6 kWh (2 GWh) Allowing a little loss that's enough to supply 2000 houses with 1000 kWh each in one month ... or 20,000 houses with 40kWh in 2.5 days.
sthnblllII 6y ago
Several physical and technological factors make Energy Vault completely impractical. Dr Philip Mason explains them here: https://m.youtube.com/watch?v=NIhCuzxNvv0 https://m.youtube.com/watch?v=NIhCuzxNvv0
aaron695 6y ago
This idea is nuts, just watch https://www.youtube.com/watch?v=NIhCuzxNvv0 https://www.youtube.com/watch?v=NIhCuzxNvv0 if you don't understand why. Does no one do fundamentals at school anymore, water is around the same density as concrete (~2.4 times smaller) except you can just use a simple pump. The reason they use concrete in these designs is because if they used water people would say it's stupid. That's literally the reason. It's the same for mineshafts. These concepts are introduced to confuse you. "But pumped hydro requires some very specific geography—two big reservoirs of water" So does concrete. Expect you are building the geography and it'll be around the same size if it stores around the same energy.
mac01021 6y ago
About 10-15 years ago my sister's highschool classmate tried to fund a startup to build mechanisms that would store energy by towing buoys down to the bottom of the ocean. I can't find it on the web now, though. It's an interesting idea compared to other gravity storage solutions because - It's the volume of the buoy rather than the mass that's important - It could be colocated with and hooked up to offshore wind farms to smooth their generation - You don't need to build a super-tall crane or elevated reservoir (but you do have to assemble the thing at the bottom of the ocean which sounds hard) I haven't heard anything about it in ages so it must have turned out not to be practical.
- lxmorj 6y ago
  Probably easier to have a hose and a balloon / reservoir of compressed air.
- colordrops 6y ago
  Why would you need to assemble anything at the bottom of the ocean? Couldn't you set it up above then drop it with the cables attached, assuming it's heavy enough?
  - mdtusz 6y ago
    You wouldn't necessarily need to even drop much more than a mass that weighs more than twice the buoyant force of the buoy with a block to redirect the cable, then have a floating platform that's more buoyant than the sinking buoy. Interesting idea.
- pjc50 6y ago
  The wind/wave people have (re)discovered that the ocean is very good at destroying things. I suspect the amount of energy stored is also disappointingly small, and that you need a buoy the size of a submarine to make a difference.
tillcarlos 6y ago
Youtuber Thunderf00t has a video about it: https://www.youtube.com/watch?v=mmrwdTGZxGk https://www.youtube.com/watch?v=mmrwdTGZxGk Apparently storing energy in concrete blocks has no advantage over water, but brings in a lot of drawbacks (mostly the whole structure being exposed to weather).
- tillcarlos 6y ago
  Just noticed that sthnblllII https://news.ycombinator.com/item?id=25654918 https://news.ycombinator.com/item?id=25654918 has already posted the same answer.

133 points by headalgorithm 6y ago

dzhiurgis 6y ago

Then there’s compressed air under water storage. There have been trials but roundtrip efficiency isn’t great IIRC.

huhnmonster 6y ago
There are a bunch of other technologies as well. Huge flywheels [1], which are supposed to be used for very responsive power needs (i.e. grid stabilisation), trains loaded with weights which get pulled up a mountain and released [2], redox-flow batteries and so on. [1]: https://www.energydigital.com/smart-energy/worlds-largest-flywheel-energy-storage-system https://www.energydigital.com/smart-energy/worlds-largest-fl... [2]: https://aresnorthamerica.com/ https://aresnorthamerica.com/
- timr 6y ago
  Also molten salt: https://www.solarthermalworld.org/news/molten-salt-storage-33-times-cheaper-lithium-ion-batteries https://www.solarthermalworld.org/news/molten-salt-storage-3... People talk about making "personal" molten salt units for the home, which seems a little terrifying.
  - jandrese 6y ago
    I wonder what the local zoning commission has to say about the guy building a personal toxic metal death ray in his backyard?
    - peteradio 6y ago
      That is why I will never live in a HOA neighborhood.
      - jandrese 6y ago
        The zoning commission runs at the town/country level, so even if you don't have HOA busybodies you still need to get the permits. The law is usually worded such that if you're doing something abnormal you don't get a "there is no rule that says a dog can't play baseball" loophole, you instead have to bring it up before the county council and justify the project.
- taeric 6y ago
  Seems the train idea is similar to the old counterbalance system for trollies in Seattle.
  - imtringued 6y ago
    Hydro pump storage works because you don't have to pay for the weights. Building a train is worse than batteries in terms of economics.
jandrese 6y ago
Usually when you see compressed air storage solutions they're talking about plugging up an old mineshaft or cave and pumping air in. Doing it under water would seem to have some advantages, like a less catastrophic failure condition and having a ready place to sink all of the heat. Downside is that the water would cool the air much more effectively than solid rock so you lose efficiency.
- jayd16 6y ago
  Are there any combination solar, hydro, fracking/oil plants? I'm joking but not entirely. Not sure how much water would fit in an oil field but it seems like a natural reservoir one could use.
  - jandrese 6y ago
    The trick would probably be getting your energy back after you've pumped the old oilfield full of water. Most oil fields aren't gushers, especially after they've had most of the oil sucked out of them.
ed25519FUUU 6y ago
A lot of these storage technologies have been around for a long time (I have a "Nature" magazine from the 60s that discusses storing excess energy as wind in salt mines and in lakes. This was the 60!). What people underestimate is just how much energy we need to store. Lakes won't do it and neither will salt mines. Gravity certainly won't do it. We need to think much BIGGER.

robbrown451 6y ago

Seems like they'd do it on the edge of a natural cliff to avoid having to build a tower, or maintain an abandoned mineshaft. There aren't big cliffs everywhere, obviously, but where there are, seems like an economical option.

wedn3sday 6y ago
Cliffs tend to move a bit, falling slowly over time. There may be more stable cliffs to use, but the ones near where I grew up on the coast have a fairly steady fall rate (a new cm/year).
imtringued 6y ago
Drilling holes for energy storage isn't economical at all. Gravitricity is never going to work on a large scale.
- jeffbee 6y ago
  Yeah, don't do the math on their outrageous claims. Excavating a hole in the ground that's 150m across and 1000m deep represents a monstrous up-front investment of energy. Not to mention the small matter of their 8-megaton piston costing half a billion dollars.

sliken 6y ago

Seems a bit limited and expensive. Pumping water uphill when there's a surplus seems like a no brainer, doubly so when you are already using hydro and hydro production is already tied into the grid. Seems like pretty much the only way to cost effectively bank substantial amounts of energy for 6 months.

Pfhreak 6y ago
It's good but not perfect. Dams require a reservoir, which takes land out of use and changes the flow dynamics of a river. It can interrupt wildlife patterns both up and downstream. It introduces some risks of dam failure, and decommissioning a dam requires careful management of built up sediment. Flooded organic matter anaerobically produces methane. It also requires significant space and particular configurations (must be on a river, must be in a hilly or mountainous area, etc.) It also isn't necessarily scalable -- how many more dams can we build? You can build a crane and blocks or drill a big hole in lots and lots of places. So yes, pumped hydro is better than fossil fuels. But also it's not something we can consider to be the ultimate solution to the issue of storage. By all means, let's use it (and we do use it today), but not stop there.
- sliken 6y ago
  Dams are expensive and have significant side effects. However the duty cycle on a dam is pretty low (they rarely run the turbines at 100%). So there's substantial additional capacity that could be had by pumping water upstream whenever there is a surplus of power.
- deepspace 6y ago
  I am not sure that this form of storage is comparable to a traditional dam. The fact that blocks of matter need to be physically moved by a crane severely limits the total capacity of the system. The most dense metals are only about 20x as dense as water, so we are not talking about a huge volume of water. The equivalent mass of water can be stored in a tank - no dam required and moved through a pipe - no river required.
  - 6y ago

DeRock 6y ago

Something that doesn't often get brought up in these energy "storage" discussions is the potential for duty cycling existing generation to time shift the duck curve. Eg. California (large solar generation) shares a grid with Washington and British Columbia (large hydro generation). When the sun is shining, hydro reservoirs can be filling, as solar is meeting the demand. When the sun goes down, hydro facilities can duty cycle on and drain the overhead. This requires some flexibility in reservoir levels, as well as the ability to stop/re-spin turbines on a daily cadence. But you eliminate all of the efficiency losses with schemes such as pumped storage (though gain some transmission losses due to the increase length of geographic arbitrage). The same opportunity exists on the East-West axis. The sun is still shining in California after its set on the East coast.

abfan1127 6y ago
Its my understanding that some hydro facilities do this. One issue I can think of is the losses of transmitting that much electricity from 1 area to another (1000s of miles away). the losses of transport coupled with the losses of "storage" and "generation" make it more expensive. I don't know the actual costs, just ideas I think about.
- ebiester 6y ago
  The losses of transport are relatively small, smaller than would be expected: see http://insideenergy.org/2015/11/06/lost-in-transmission-how-much-electricity-disappears-between-a-power-plant-and-your-plug/ http://insideenergy.org/2015/11/06/lost-in-transmission-how-...
- sdepablos 6y ago
  Not so much with ultra-high-voltage lines. China has been doing it for years because of the really long distances between electricity production and consumption. https://en.m.wikipedia.org/wiki/Ultra-high-voltage_electricity_transmission_in_China https://en.m.wikipedia.org/wiki/Ultra-high-voltage_electrici...
arawde 6y ago
It was my understanding that this is more of a seasonal thing than on a day to day basis. That is, during the summer, southern California uses a large amount of electricity for climate control, and so power is transferred along the Pacific DC intertie in a north -> south direction. In the winter, electricity usage in the north is devoted to heating, whereas in the south temperatures are mild. The result is that power is moved back up the intertie from south -> north. In the spring, snowpack melt refills the reservoirs in the hydroelectric system, allowing it to be ready to provide power to the south again once temperatures start to climb.

huhnmonster 6y ago

This article surprised me since funding came from Softbank and not the state government as most does IIRC. Where I see the problem with all these forms of energy storage is that there is no one efficient approach (yet!) and innovation will come mostly from government funding, so governments decide what they see as the best opportunity. This seems like its pretty much hit-or-miss and betting on the wrong thing will arguably speed up the development of it but at the same time, we might end up at a point we could have reached quicker and cheaper had we used a different technology.

amelius 6y ago

https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit... > Pumped storage is by far the largest-capacity form of grid energy storage available, and, as of 2020, the United States Department of Energy Global Energy Storage Database reports that PSH accounts for around 95% of all active tracked storage installations worldwide, with a total installed throughput capacity of over 181 GW, of which about 29 GW are in the United States, and a total installed storage capacity of over 1.6 TWh, of which about 250 GWh are in the United States.

nabla9 6y ago

This solution competes against short term storage, (typically tens of minutes, up to hours). Flywheels are commonly used and efficient energy storage for short term. Pumped hydro mentioned in the article is good for long term storage > weeks, months, even seasonal.

fullstackchris 6y ago

Quite a while ago, I thought up of what I though would be a simple system that has a net positive energy output (it already sounds ridiculous, I know, but I just can't see what concept I am missing) that follows this principle. I finally have a relevant article I can share it with here on Hacker News! The gist of the system is as follows: 1. let a hanging weight freefall under gravity to spin a generator. (via a pulley connected to a chain drive or gears etc) 2. The power generated by the generator is stored in a battery 3. The weight is pulled up very slowly back to its drop position using a DC motor that uses power from the battery (the DC motor could be actually the generator itself but likely a specially tuned one for slow lifting will be better) 4. Repeat. The system lifting / reset process requires less energy than the energy produced by the drop, so there will slowly be a net buildup of charge in the battery. Super simple numbers example: PE of a 100kg mass falling 2m: PE = (100kg)(9.8m/s2)(2m) = 1960 J The mass falls at a near g acceleration - I know it won't be exactly g because of the moments of inertia of the generator and generating drive apparatus - but it would be quite close to g. At this acceleration the mass falls for ~0.63s, so the theoretical max power we can hope to extract using the generator is: P = W / t = 1960 J / 0.63s = ~3000 W Even if we consider a horrible electric generator with only 50% efficiency (just to be even more conservative and fair, and to capture any losses we've forgotten), we should hope we can get at least 1500 W from the drop. The "trick" of mine is mentioned in that very slow "reset time" for the weight. That is, use a DC motor to pull the weight up, but give it a long time to do so. In this way, the power used to lift the weight back up to its dropping point is much less than what was produced by letting the weight fall and spin the generator. Using the same numbers from the example above, if we let the lift time be, say 20 minutes (=1200s) and since we know the W of the lift is the same as the drop PE, then the power needed to lift the weight back to its original drop point is: P = 1960 J / 1200s = 1.63 W That means we produced about 1500 W (even with our crappy 50% efficiency generator), and only need ~2 W to reset the system. Assuming you put a nice battery between the generator and the dc motor - you get a net positive storage of energy over time. Does anybody see any glaring issues with such a system and my analysis? I know when anything in physics appears to be a free lunch, something must be wrong. (Though if you consider these long 'cycle' times, it isn't really a free lunch) Perhaps I don't understand exactly how DC motors / generators really draw or produce power in the real world - Physics 101 was a long time ago for me :) The trick to my proposed system, which systems like those in that of the linked article don't do, is my slow reset time. Obviously not feasible for massive applications or load balancing, but a net power storer nonetheless.

orange_tee 6y ago

These ideas are cute but they lack interest from major players. In Europe it seems the big players are betting big on hydrogen. The EU is looking to convert all gas pipelines to be hydrogen proof and for new pipelines to also be hydrogen proof. I know Japan is also very bullish on hydrogen infrastructure. With regards to energy storage, it seems to me the solutions that are most likely to be widely adopted are: batteries, pumped hydro, and hydrogen and the many synthetic hydrocarbons that can be obtained from it. Besides that, improvements to the energy grid can be made to eliminate the need to store as much energy in the first place.

blue_box 6y ago
Could you share your resources, please?
- orange_tee 6y ago
  I got it through word of mouth from people involved in projects, but I did a Google search for you and came up with many public trusted sources: https://ec.europa.eu/info/sites/info/files/hydrogen_europe_-_vision_on_the_role_of_hydrogen_and_gas_infrastructure.pdf https://ec.europa.eu/info/sites/info/files/hydrogen_europe_-... https://hydrogeneurope.eu/hydrogen-storage https://hydrogeneurope.eu/hydrogen-storage https://www.euractiv.com/section/energy/news/gas-grid-operators-unveil-plan-for-european-hydrogen-infrastructure-backbone/ https://www.euractiv.com/section/energy/news/gas-grid-operat... Were we stand in 2021 is that policy is already on the books and funds being distributed for these projects. So hydrogen ready pipelines are definitely getting built. Whether they will prove useful remains to be seen.
  - Hypx 6y ago
    This being explored in the US too: https://www.energy.gov/sites/prod/files/2019/03/f60/fcto-satyapal-verdexchange-jan19.pdf https://www.energy.gov/sites/prod/files/2019/03/f60/fcto-sat... I suspect that utility companies in the US are only a few steps behind European utility companies. This should be a global thing before long.

OliverJones 6y ago

The grid-nerd term for rapid-response capacity delivery is "frequency control ancillary services." It's a real problem in times of heavy load. If a local grid's frequency drops below nominal (60Hz US, 50Hz elsewhere) the regional grid has to disconnect. So without rapid-release stored energy a power generating org has to fire up extra capacity and keep it running to cover transients. Old missile silos might be interesting. But most of them are far from population centers. Pumped storage is still great given the right geography. Northfield Mountain has been running flawlessly for almost half a century, storing about 9 GwH. https://en.wikipedia.org/wiki/Northfield_Mountain_(hydroelectricity_facility) https://en.wikipedia.org/wiki/Northfield_Mountain_(hydroelec... But it takes about ten minutes to spool up. And the fish and boaters in the nearby Connecticut River definitely notice it.

Florin_Andrei 6y ago
When the frequency of the generator is not tied to a mechanical property of it (like the spin of a turbine) - e.g. when the source is solar panels and the AC is produced via an inverter circuit, what are the remaining frequency-related issues? I imagine with solar the generator can pretty much pick any frequency it wants, it should not be influenced by load, it could simply stay in sync with the grid no matter what, is that right?
- bob1029 6y ago
  The problem with inverters is that they have no inertia to impart on the grid. When you have a gigantic spinning turbine, the amount of power it takes to change its speed is immense. This has huge implications for grid stability when we are talking about renewables. The resolution for this is something called a synchronverter: https://en.wikipedia.org/wiki/Synchronverter https://en.wikipedia.org/wiki/Synchronverter
- beckingz 6y ago
  Most cheaper solar panel inverters are synced to the grid and require the external 60hz wave to output power, resulting in solar panels that will not provide energy without being connected to the grid.

baybal2 6y ago

Excuse me, but the company in the article was debunked as pretty much a scam. You cannot physically make that work economically.

imtringued 6y ago
Yeah all of them are questionable. The only one that has even a tiny chance of succeeding is the piston idea. You don't have to pay for the weight and you only have to cut the circumference of the piston out.
- Animats 6y ago
  The piston idea has a problem. Rock isn't like that. Natural rock does not often come as one big solid piece. It's more like a pile of boulders of different sizes. There are cracks, underground water, rubble, etc.
pipermerriam 6y ago
Can you provide a source for this?
- p1mrx 6y ago
  Here's a sarcastic YouTube video, at least: https://www.youtube.com/watch?v=NIhCuzxNvv0 https://www.youtube.com/watch?v=NIhCuzxNvv0
jussij 6y ago
Based on the video found on the Energy Vault web site they seem to be doing some serious engineering in building their prototype: https://energyvault.com/commercial-demonstration-unit/ https://energyvault.com/commercial-demonstration-unit/ As to whether it works, I guess they will know once they've complete the prototype build and done some testing.
- baybal2 6y ago
  Just do the math. Total amount of energy they store is no more than a TEU container worth of lithium batteries, or few dozens of modern flywheels, or hundred so of plain steel ones.

WalterBright 6y ago

By far the most efficient grid "battery" to reconcile fluctuations in demand & supply is to have a realtime price for electricity. Water heaters, for example, can be equipped with an internet device (at last, a reason for an internet connected water heater!) to monitor the price of electricity and shut off the heater during price spikes. Some "batteries": 1. hot water heater 2. HVAC system 3. EV charging 4. Some lights (like yard lights) can be dimmed or shut off during rate spikes 5. Same for street lighting 6. Computers can switch to low power mode 7. Refrigerators 8. Dryers This is far better than the "rolling blackout" bureaucratic solution. Note that the pump price of gas varies daily. This is the market reconciling constantly shifting supply & demand, and it works great.

choeger 6y ago
Heating water with electricity is the literally last thing we should do. That is, once clean electric energy is cheap, we can do it. But we are not there yet. Hence we should at least use heat pumps or similar technology.
- WalterBright 6y ago
  Meanwhile, there are hot water heaters in use everywhere. That isn't going to change anytime soon. Besides, in many places during peak solar there isn't anyplace to dump the electricity. Electric hot water heaters can take care of that problem, as water will stay hot in one for a couple days (I know from experience).
  - dharmab 6y ago
    A heat pump can approach 500% efficiency and is powered by outdoor ambient air (using direct heating as a fallback). https://www.youtube.com/watch?v=-vU9x3dFMrU https://www.youtube.com/watch?v=-vU9x3dFMrU
    - WalterBright 6y ago
      It still uses electricity, and can be shut off during electric rate spikes, acting just like a "grid battery" without the expense.

ogre_codes 6y ago

I so hate IEEEs broken web-site. Every time someone links to this site I'm irritated by the broken scrolling.

blackrock 6y ago

I wondered if you can use hydrogen instead. Use solar/wind to crack water into hydrogen and oxygen. Compress it to liquefy it. Store this in some temporary storage tanks. Then when you want to make electricity, pipe the hydrogen and oxygen into a fuel cell. Then electricity and pure drinking water comes out. Then you can bottle the pure drinking water and sell it locally for an additional profit. I haven’t analyzed the cost for all the technology and infrastructure. But this idea seems mechanically simpler than the gravity brick idea. Additionally, you can transport the LH and LOX, to other areas if necessary.

imtringued 6y ago
Hydrogen works despite the inefficiency because there is an existing gas infrastructure ready to be converted. If we had to build everything from scratch we would be desperate for other solutions.

AndrewDucker 6y ago

If I've just done my maths right then an AA battery is enough to lift 360 metric tons up 1m. Edit: out by a large factor. Should be that many kg, not tons. So lifting trains into the air is going to have its work cut out to match plain old battery technology.

wmwmwm 6y ago
I think that’s about a 1000x overestimate - about 1Ah * 1.5v * 3600s = 5400 J - that’d lift 540kgs up a metre (Maybe double that for an alkaline one)
- AndrewDucker 6y ago
  Thank you.
kmm 6y ago
An AA battery holds about 4 watt hours of energy, or 14.4 kilojoule. Dividing by 9.81 m/s^2 times 1 meter, yields about 1.5 metric tons. Not quite 360, but still quite a lot.

thoughtstheseus 6y ago

As an alternative to storage working with large industrial users to adjust their electricity demand in real time can help mitigate some supply/demand imbalances.

flaburgan 6y ago

I always had the feeling that with electricity consumption, smaller is better. What if we all add a few blocks in our corridor which would be lift up during the night and bring back energy during the day? This would get the curve plane and we can follow its usage closely, wanted to reduce our own bill...

lovemenot 6y ago
Your intuition is probably not right in this case. Gravity is actually very poor for energy storage. If your home system could lift 100kg over 10m it would store only around 3 Wh. The advantage of these industrial systems is that mass scales by volume, so a little more surface area can deliver a lot more potential energy. And of course the capital investment is much more economic on a centralised system.
- flaburgan 6y ago
  But isn't that efficiency directly depending of the system itself? I mean the performance of the dynamo which would create the electricity when the weight goes down
  - lovemenot 6y ago
    It's not a question of efficiency. My figures assume 100%, which is certainly too optimistic. No, it's about the energy in any reasonably home-sized system is way too small. About one or two AAA batteries' worth. Though industrial-sized systems can be much better, they too are under-powered, against our needs. Except pumped-hydro.

rocqua 6y ago

https://www.wattisduurzaam.nl/27493/energie-opslaan/reservoirs/crazy-storage-tower-energy-vault-picked-by-world-economic-forum/ https://www.wattisduurzaam.nl/27493/energie-opslaan/reservoi... This is a critique of these ideas. The main points are: - Lifting speed needs to be 40 kph - Minimal height of lowest stacked state limits storage

boringg 6y ago

Soo many different better options. As a member of the energy storage industry I give this a hard pass, this is also old news, costly and not multi functional. Pumped storage makes sense in some specific cases. Look to lithium ion for short time high cycle/fast response, vanadium flow for long duration (expensive currently, large sites), hydrogen potentially and fascinating long duration start up out of Massachusetts (forget the name right now). More tech will come down the pipeline soon. Compressed air possibly but hasn’t really progress much over its existence so far (geological restraints too). My two cents

rossjudson 6y ago
The new thing I read there was the use of old abandoned mine shafts, providing up to 1km of vertical distance with a 5000 tonne mass. There are a lot of abandoned mine shafts. Does it work?
1958325146 6y ago
I bet the Massachusetts one you are thinking of is Ambri, which is making a liquid metal battery. https://ambri.com/ https://ambri.com/
- boringg 6y ago
  It was form energy - will read into ambri though. https://formenergy.com/ https://formenergy.com/

mikewarot 6y ago

I think putting tanks in the bottom of abandoned mineshafts, and filling them through positive displacement pump/motors is the way to go. You get energy as the water goes down, and use it to pump the water back up. The costs are the mine, and the maintenance required to keep the lift working, and the whole thing from collapsing... and two tanks / pools.. one at the bottom, one at the top, piping between the two, and a positive displacement pump, with a motor/generator. All known technologies.

grizzles 6y ago
This won't work because of erosion.
- mikewarot 6y ago
  Erosion of the pump?
- lxmorj 6y ago
  Nah man you make tanks down there
  - grizzles 6y ago
    There is a reason no one has tried it. What you are proposing would be very expensive. You have to transport the water to them. The large tanks (eg. 10M litres) require ongoing maintenance. You must make sure they don't leak, evaporate too much, make sure the ground in both places won't settle, worry about seismology, etc.

kumarvvr 6y ago

Energy Density of Gravity storage is too small to work with smaller installations. Investment is high. The future of renewable energy is obviously Solar PV, with Wind and other offsetting to some extent, but Solar is predictable, cheap to build and easy to maintain. I really wish there was more thrust into carbon capture and conversion to fuel with Solar power.

8bitsrule 6y ago

The article mentions potentially lifting an 8 million metric ton piston. Let's see: A weight of 8 x 10^9 kg raised 100 meters = a potential energy of 8 x 10^11 kg-m PE x 2.724 x 10^-6 kWh / kg-m = 2.18 x 10^6 kWh (2 GWh) Allowing a little loss that's enough to supply 2000 houses with 1000 kWh each in one month ... or 20,000 houses with 40kWh in 2.5 days.

sthnblllII 6y ago

Several physical and technological factors make Energy Vault completely impractical. Dr Philip Mason explains them here: https://m.youtube.com/watch?v=NIhCuzxNvv0 https://m.youtube.com/watch?v=NIhCuzxNvv0

aaron695 6y ago

This idea is nuts, just watch https://www.youtube.com/watch?v=NIhCuzxNvv0 https://www.youtube.com/watch?v=NIhCuzxNvv0 if you don't understand why. Does no one do fundamentals at school anymore, water is around the same density as concrete (~2.4 times smaller) except you can just use a simple pump. The reason they use concrete in these designs is because if they used water people would say it's stupid. That's literally the reason. It's the same for mineshafts. These concepts are introduced to confuse you. "But pumped hydro requires some very specific geography—two big reservoirs of water" So does concrete. Expect you are building the geography and it'll be around the same size if it stores around the same energy.

mac01021 6y ago

About 10-15 years ago my sister's highschool classmate tried to fund a startup to build mechanisms that would store energy by towing buoys down to the bottom of the ocean. I can't find it on the web now, though. It's an interesting idea compared to other gravity storage solutions because - It's the volume of the buoy rather than the mass that's important - It could be colocated with and hooked up to offshore wind farms to smooth their generation - You don't need to build a super-tall crane or elevated reservoir (but you do have to assemble the thing at the bottom of the ocean which sounds hard) I haven't heard anything about it in ages so it must have turned out not to be practical.

lxmorj 6y ago
Probably easier to have a hose and a balloon / reservoir of compressed air.
colordrops 6y ago
Why would you need to assemble anything at the bottom of the ocean? Couldn't you set it up above then drop it with the cables attached, assuming it's heavy enough?
- mdtusz 6y ago
  You wouldn't necessarily need to even drop much more than a mass that weighs more than twice the buoyant force of the buoy with a block to redirect the cable, then have a floating platform that's more buoyant than the sinking buoy. Interesting idea.
pjc50 6y ago
The wind/wave people have (re)discovered that the ocean is very good at destroying things. I suspect the amount of energy stored is also disappointingly small, and that you need a buoy the size of a submarine to make a difference.

tillcarlos 6y ago

Youtuber Thunderf00t has a video about it: https://www.youtube.com/watch?v=mmrwdTGZxGk https://www.youtube.com/watch?v=mmrwdTGZxGk Apparently storing energy in concrete blocks has no advantage over water, but brings in a lot of drawbacks (mostly the whole structure being exposed to weather).

tillcarlos 6y ago
Just noticed that sthnblllII https://news.ycombinator.com/item?id=25654918 https://news.ycombinator.com/item?id=25654918 has already posted the same answer.