EnergyVault gravitational energy storage - Page 1
Forum section: electronics / general

author: AlbertL
author_rank: Regular Contributor
timestamp: January 22, 2022, 11:46:31 pm
content: Raising and lowering concrete blocks; apparently comes in two flavors:

author: ejeffrey
author_rank: Super Contributor
timestamp: January 23, 2022, 02:43:19 am
content: The energy density works out pretty bad for this. That's why it's normally done with water and reservoirs where you can have a tremendous volume. I have a hard time imagining this would ever beat batteries on any metric.

author: f4eru
author_rank: Super Contributor
timestamp: January 24, 2022, 10:27:17 pm
content: It's just simply hopeless.

author: dmills
author_rank: Super Contributor
timestamp: January 28, 2022, 03:08:07 pm
content: Two lakes, a set of turbines and a set of big pumps, that's the way you use GPE for energy storage, and that version works just fine.I am not sure, but they may even use the turbines as the pumps when power is cheap?I think concrete blocks would need an AWFUL lot of cycles on the system before just making an equivalent amount of CO2 in a CCGT wasn't greener.

author: voltsandjolts
author_rank: Unknown
timestamp: January 28, 2022, 03:46:10 pm
content: Quote from: f4eru on January 24, 2022, 10:27:17 pmhttps://gravitricity.com/

author: station240
author_rank: Unknown
timestamp: January 28, 2022, 05:33:47 pm
content: Making a huge number of new concrete blocks for this storage system is just nuts.Cement production is very CO2intensive, and then you add the gravel you have to mine/process.Plus you've going to crack blocks moving them around all the time, resulting in having to replace them for safety reasons.Makes the other idea with railcars hauling containers up/down hill and filled with something look positively mainstream. As at least you could use concrete from demolition sites, dirt, garbage or anything cheap or waste.

author: ejeffrey
author_rank: Super Contributor
timestamp: January 28, 2022, 06:32:18 pm
content: Using concrete for the weight really creates a huge CO2 deficit you have to overcome before it is even CO2 negative, but the bottom blocks need enormous strength. A lightweight box filled with gravel or other cheap fill isn't going to be strong enough to hold up the tower. The blocks at the bottom aren't doing much for you in terms of energy storage but you need to have them and they have to be strong and stable. Building a high load capacity skyscraper is expensive it turns out. It would be much better to use a natural cliff and lift the blocks up and down. Unfortunately natural cliffs aren't particularly stable for the same reason the tower would have problems. So you really want a natural hill with modest slope. Unfortunately that makes the crane not work particularly well, better to have some sort of ground based conveyance up the hill, like some rolling carts filled with gravel. Gravel is kind of annoying to load and unload without wasting a lot of the energy you hope to store, so its probably better to use something like water that is cheap and easy to move. Of course then the moving carts can just be replaced with a pipe.Another way to look at it is this: if a battery short circuits it overheats and catches on fire. If you drop a rock from the top of a skyscraper, how much does it heat up when it hits the ground? Not much. The energy density difference for feasible gravitational storage is enormous. The only way to compensate for that is to have a truly enormous volume of ballast. A lake or reservoir can meet this requirement much better than anything we can practically build.

author: Gyro
author_rank: Super Contributor
timestamp: January 28, 2022, 06:53:14 pm
content: Quote from: voltsandjolts on January 28, 2022, 03:46:10 pm12000 Tonnes running up and down a 300m mineshaft does sound like a decent amount of energy storage.

author: uer166
author_rank: Super Contributor
timestamp: January 28, 2022, 07:25:38 pm
content: Quote from: Gyro on January 28, 2022, 06:53:14 pmDoes it?That is 10764316800 Joules, which is 2990.088 kWh, which is just under 30 Tesla Model S packs. Something tells me 30 of those packs is much, much cheaper than the 12kT conveyance mechanism. Or another way: this is equivalent to asingleTesla Megapack, which is the size of one shipping container. It seems like all this stuff sounds cool and great until you do some minimal napkin math.Edit, I think I'm off by a factor of m->ft conversion. So it's more like 3 Megapacks, and 90 Teslas, but the general message stands

author: ejeffrey
author_rank: Super Contributor
timestamp: January 28, 2022, 07:34:12 pm
content: Its 30 MJ or 9 MWhr, so more like 90 model S cars or 3 megapacks, but the point is still similar. Using deep mineshafts makes more sense than stacking bricks, but it's really hard to find any way other than hydroelectric where gravity storage can reach a scale where they are better than batteries. For a few megawatts hours batteries are fine. If your storage tech doesn't scale to GWhr it's pretty much going to be fighting a losing battle against batteries.

author: uer166
author_rank: Super Contributor
timestamp: January 28, 2022, 09:40:53 pm
content: Well, I'm sure stacking bricks is better than circulating current in superconducting coils, or spinning fidget spinners really,reallyfast! It seems like thermal storage is one of the most promising alternatives to batteries, scales okay as well, lots of moving parts though. 1 m^3 of water over a 100C is approx. equal to one Model S pack, more if it's a phase change system. Turbines and heat pumps sure seem to be a pain though.

author: ejeffrey
author_rank: Super Contributor
timestamp: January 28, 2022, 10:10:01 pm
content: Yeah, thermal storage seems like a reasonable option for longer term storage than batteries can accommodate. It's been fairly well studied in the context of concentrated solar thermal but could be implemented as stand alone storage. They usually use some type of molten salt at ~550 C as the storage mechanism, the energy density can be quite high. Making an insulated tank that loses < 1%/day is totally feasible. The main problems are that the efficiency is low and the capital cost of the turbine/generator is somewhat expensive (same as a thermal plant because that is what it is).The traditional problem with pumped hydroelectric is that every location with the right configuration for hydroelectric power already has it. But there has been some renewed interest in off-river pumped hydroelectric storage recently, I'd guess some combination of that + thermal storage + batteries will be able to handle most of our storage needs

author: rob77
author_rank: Super Contributor
timestamp: January 28, 2022, 10:26:24 pm
content: 3.7 millions cubic meters of water in the upper lake (that's 3.7 million tons) , 425meters of elevation difference, 735MW of installed power, yearly production ~ 200GWh , built in 1982.replacing the water with concrete blocks is just trying to re-invent a wheel using a square shape instead of a circle.Edit: adding a link to a time lapse of draining the upper lake in 2017 during a maintenance.

author: ejeffrey
author_rank: Super Contributor
timestamp: January 28, 2022, 11:54:04 pm
content: To be fair, that only works when your geology supports it. There are several US midwestern and southern states that are each bigger than many european countries and have a total elevation span less than that, much less having locations for the upper and lower reservoirs that are acceptably close to each other.

author: rob77
author_rank: Super Contributor
timestamp: January 29, 2022, 12:34:46 am
content: Quote from: ejeffrey on January 28, 2022, 11:54:04 pmagree, can't be done anywhere.. but you still have many locations where it's possible and would be a much better option. for locations where pumped hydro is not feasible, there are other options much better than 12kiloton worth of concrete blocks hanging on ropes. even pumped electrolyte battery storage is much better than those concrete blocks hanging on ropes. pumped electrolyte can be scaled by size of the tanks.. for the concrete blocks you need to replicate the whole setup to scale it. not talking about maintenance costs.. steel cables, cogs and pulleys wear out after some time especially under heavy loads coming from those concrete blocks.

author: voltsandjolts
author_rank: Unknown
timestamp: February 01, 2022, 11:37:18 am
content: Quote from: rob77 on January 29, 2022, 12:34:46 amEverything wears out.Heck, some battery storage grid balancers catch fire before they are even commisionedWhat is the long term cost of batteries at grid scale?...we don't know yet. Ask in 20 years.I like the solutions that use basic principles and engineering, easy to build, predicatable installation and maintenance costs with minimal rare earth materials.This also enables cost-effective solutions for less developed countries which they can implement themselves, so they don't have to depend on foreign technologies.Pumped hydro is a great solution when you have the geology, although I don't know how efficiency compares to other options.Molten metal batteries sounded interesting but seems to have gone nowhere since 2014

author: Marco
author_rank: Super Contributor
timestamp: February 01, 2022, 11:45:10 am
content: I think pulling deep water concrete spheres vacuum is the most promising gravitational storage technology (it's not compressed air storage). You can sink it filled with fresh water and pump to a bladder to avoid salt water corrosion of the pump. Near infinite locations available at generally much greater effective height difference than with on shore reservoir pumped hydro.

author: f4eru
author_rank: Super Contributor
timestamp: February 02, 2022, 08:35:50 am
content: The main problem with deep underwater vacuum technology is that it exists only in Powerpoint-Lala-LandNobody found out yet how to solve it's many problems in reality.For example: how to anchor the sphere to the bottom ?Ha, I know! You just need 2x the pumped water mass in concrete blocks. Duh.Meanwhile, here on earth :https://de.wikipedia.org/wiki/L%C3%BCnerseewerkBuilt 1958.Head is nearly a kilometer. Water arrives downstairs with 100 bars, at a speed of 500km/h generating 230MW.Very impressive.BTW :https://professional.hydropower.org/page/map-pumped-storage-tracking-tool

author: voltsandjolts
author_rank: Unknown
timestamp: February 02, 2022, 12:48:58 pm
content: Quote from: f4eru on February 02, 2022, 08:35:50 amEvery solution at some point was or is, only a concept in Powerpoint-Lala-Land, as you put it. So that's a mute point.Also, in this context it'snot entirely trueeither.But I agree thatif you have the geology, pumped hydro looks like a very good option.

author: Gyro
author_rank: Super Contributor
timestamp: February 02, 2022, 01:06:18 pm
content: Quote from: f4eru on February 02, 2022, 08:35:50 amThe UK one, 288MW...https://www.electricmountain.co.uk/Dinorwig-Power-StationI once went on the tour, but it didn't include the surge pond at the top of the vertical shaft. I bet that's a sight to see when they shut the valves!

author: f4eru
author_rank: Super Contributor
timestamp: February 02, 2022, 02:35:56 pm
content: Quote from: voltsandjolts on February 02, 2022, 12:48:58 pmInteresting.Butr looking at the numbers, it's not really tempting:https://www.iee.fraunhofer.de/en/topics/stensea.html#1665982880- quite bad efficiency (why only 72% ? seems to be without the cable-to-shore losses)- 23 000 tons of concrete for 12 000 tons of water displaced -> my guesstimate was exactly on point ! Too much...- nightmarish maintenanceIt would be really intersting in comparison to have numbers on a typical concrete usage for pumped hydro...

author: Marco
author_rank: Super Contributor
timestamp: February 02, 2022, 03:45:15 pm
content: You might be able to get away with an anchor made as a container with a small amount of virgin concrete filled with rubble.If the the costs work out so you can have one pump/generator per sphere maintenance is easy, decouple it from the anchor and do maintenance at the surface.

author: ejeffrey
author_rank: Super Contributor
timestamp: February 02, 2022, 04:43:25 pm
content: It's an interesting concept, but I'm generally skeptical of cost estimates for anything involving deep sea construction. There are also proposals to do artificial pumped hydro using deep mineshafts, essentially the on-land version of this concept with similar issues.Available geology for conventional pumped hydroelectric is certainly an issue, but there have been some recent research showing that there may be a fair a bit of potential (ha!) untapped resources for closed loop systems using existing lakes:https://www.sciencedirect.com/science/article/pii/S2542435120305596It still doesn't work everywhere, but possibly in enough locations that when combined with more HVDC transmission it could cover most of our needs.

author: voltsandjolts
author_rank: Unknown
timestamp: February 02, 2022, 04:52:49 pm
content: Quote from: f4eru on February 02, 2022, 02:35:56 pmSame ball park as pumped hydro:https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricityQuote

author: rob77
author_rank: Super Contributor
timestamp: February 03, 2022, 01:02:28 am
content: Quote from: f4eru on February 02, 2022, 02:35:56 pmdon't have the exact numbers, but the efficiency of a lake to store water is much better than a bunch of spheres.. and in the lake you don't have to enclose the water from the top. furthermore the concrete lining of the lake doesn't have to take the pressure of a 750m water column.. so it's much less concrete.maintenance will be insane in the depth of 750m ... there is no such thing as "ok sending a technician down"... saturation diving takes time and is expensive.pumped hydro you can drain the upper lake and the shafts and then use conventional technology for the maintenance , you take you everyday cranes, trucks, dudes in hard hats...and i would be curious what kind of turbine are they using.. the say 12200 cubic metres will last 4.5 hours.. that's less than 1 cubic meter per second with the head of 750m - that would be a pelton wheel considering the head and flow.

author: voltsandjolts
author_rank: Unknown
timestamp: February 03, 2022, 10:42:11 am
content: Quote from: rob77 on February 03, 2022, 01:02:28 amNope.Read the post right above yours, the numbers are right there.

author: Marco
author_rank: Super Contributor
timestamp: February 03, 2022, 01:52:47 pm
content: Quote from: rob77 on February 03, 2022, 01:02:28 amHow reliable can you make machinery to make a sphere slightly boyant, decouple it from the mooring and winch it to the surface? If you can make that reliable enough at low enough cost, it becomes viable to do the only significant maintenance at the surface.

author: AlbertL
author_rank: Regular Contributor
timestamp: February 03, 2022, 05:32:22 pm
content: Here are a couple of surge tanks in action:Quote from: Gyro on February 02, 2022, 01:06:18 pm

author: Gyro
author_rank: Super Contributor
timestamp: February 03, 2022, 05:45:01 pm
content: Impressive, thanks.P.S. I found a video showing just how fast the valves at Dinorwig actually open and close!...

author: rob77
author_rank: Super Contributor
timestamp: February 03, 2022, 06:22:53 pm
content: Quote from: Marco on February 03, 2022, 01:52:47 pmask the marine salvage companies how easy it is to lift and sink 25000 tonsand the biggest problem with your suggestion is that you hardly make a 25000 ton concrete ball buoyant when the inner volume is 12200 cubic meters , your math doesn't add up. whole point of that sphere is to stay put on the seabed without anchoring.

author: rob77
author_rank: Super Contributor
timestamp: February 03, 2022, 06:37:16 pm
content: Quote from: voltsandjolts on February 03, 2022, 10:42:11 ami was not talking about the efficiency of energy storage... i was talking about the efficiency of concrete usage... the sphere is 25000 tons of concrete and stores 12200 tons of water... that 2:1 concrete to water by mass... when building a artificial lake you need far far less concrete than the mass of stored water.

author: Marco
author_rank: Super Contributor
timestamp: February 03, 2022, 08:20:53 pm
content: Quote from: rob77 on February 03, 2022, 06:22:53 pmShips have a little more compromises against sturdiness. You can't just put a bubble of air in it and lift it up.QuoteIt has to survive the pressure, nothing more. Mooring can stay down, mooring doesn't need maintenance.Come to think of it though, how much maintenance does a concrete sphere even need? Will it really be so difficult to make a re-usable seat for the pump assembly which doesn't wear out any time soon? Just lift the pump assembly, do the maintenance and change the rubber seal at the surface and seat it on the sphere again when done?

author: rob77
author_rank: Super Contributor
timestamp: February 04, 2022, 04:24:55 am
content: Quote from: Marco on February 03, 2022, 08:20:53 pmyou somehow ignored the point related to buoyancy of a 25000 ton sphere with a 12200 cubic meter cavity... how exactly will you make it buoyant ? you would need to attach another cavity of 12800 cubic meters... or do you think you could inflate the concrete ball to make it buoyant ?"just lift the pump assembly" is in the same ballpark as "just make it buoyant" ... 750m water column vs vacuum , that's a serious force the pump assembly must cope with... do you think it's easy to dismantle something like that especially in a depth of 750meters and "just lift it" ?maintenance will be definitely needed, things break and wear out.

author: Marco
author_rank: Super Contributor
timestamp: February 04, 2022, 11:07:11 am
content: Why would you leave it vacuum to lift the pump assembly? Just let it flood through a bypass.

author: voltsandjolts
author_rank: Unknown
timestamp: February 04, 2022, 05:18:33 pm
content: Quote from: rob77 on February 04, 2022, 04:24:55 amBe sensible sir, of course you would not raise the concrete sphere for maintenance.

author: rob77
author_rank: Super Contributor
timestamp: February 05, 2022, 04:59:18 pm
content: Quote from: voltsandjolts on February 04, 2022, 05:18:33 pmyes exactly that was my point ! you can't lift the concrete sphere for maintenance and you can't dive to 750m for maintenance either ! but the tech submerged to 750 meters needs to be maintained to keep it running.

author: rob77
author_rank: Super Contributor
timestamp: February 05, 2022, 05:16:54 pm
content: Quote from: Marco on February 04, 2022, 11:07:11 ameither you don't understand or trolling....you have assembly which must withstand vacuum against the pressure of 750m water column. it means it must be sealed and fastened well... all clear right ? hope you follow me.now imagine how would you remove such a assembly from the concrete ball in a depth of 750m.a) you can't fish it out with a hook... "plop" and it's out like cork from a bottle... doesn't work like that , it's has those seals and fasteners.b) you can't dangle a wrench on a 750m rope and release the fasteners with your tongue at the right angle... doesn't work that way.c) you could send down saturation divers - it takes roughly a week do to down and week to come back up, probably even longer. divers live in a steel tank/submarine in the depth and breathing helium-oxygen... expensive as hell to have anything done by saturation divers. and as far as i know 700m is the current depth record for such a work.d) you could develop and build some specialized robot submarines controlled through cables from barges/ships above (wireless doesn't work under water except very long waves) - also expensive as hell and doable only during calm seas.i know that you have a solution for every impractical idea some startup comes up with , but real life is a bit more complicated

author: Marco
author_rank: Super Contributor
timestamp: February 05, 2022, 06:02:14 pm
content: The pump assembly will weigh a couple tons and the moment you pull vacuum a 10 m2 lid will get forced down with around 10 extra ton. I don't think it's all that natural to assume you need pre-strain on the seal to hold back the water, I assumed simple guide pins would be enough. With some robot to clean the seal seat.

author: voltsandjolts
author_rank: Unknown
timestamp: February 05, 2022, 07:58:24 pm
content: Quote from: rob77 on February 05, 2022, 05:16:54 pmeither you don't understand or your trolling....I played a very small part in aprojectwhich placed a multi-megawatt electrically driven turbine compressor at a water depth of >200m and it’s been down there, running since 2016. In comparison, pumping water out of these concrete bell jars is child’s play. Of course, you would not go this route if geology allowed other means of pumped storage. Maybe the volume of concrete is abhorrent. Maybe the numbers won't add up inreality. But to dismiss it out of hand because of these nonsense maintenance issues (which are solvable BTW) is short sighted and lacks the imagination required for creating new technologies.

author: rob77
author_rank: Super Contributor
timestamp: February 07, 2022, 07:54:13 am
content: Quote from: voltsandjolts on February 05, 2022, 07:58:24 pmcool project and amazing reliability! , but compressing natural gas can't be compared to pumping sea water at 75atmospheres of pressure.what was the cost of the pump assembly ? it sure makes economical sense when pumping natural gas, but let's be realistic.. we're talking about 5MW of pumped hydro with similar cost for the pump assembly (of course manufacturing at large scale would bring the cost down a bit).btw.. the numbers from that reality you linked are terrifying...lifetime 20 years... what ?? why ? concrete lasts much longer ! why only 20 years thenprobably the maintenance issues i'm talking about are the reason of the short lifetime ?so we'll end up with concrete spheres on seabed everywhere ? are we creating "new technology" to be cleaner while leaving crap behind ? manufacturing concrete creates a lots of CO2, abandoning concrete structures is definitely not "green".furthermore all calculations are based on assumption of having 2 cycles per day ? i don't think we have lows on the grid 12 hours apart long enough to charge a pumped hydro twice a day... so probably we should double the cost per kWh in their calculations.

author: voltsandjolts
author_rank: Unknown
timestamp: February 07, 2022, 10:51:36 am
content: Quote from: rob77 on February 07, 2022, 07:54:13 amCorrect, it can't. Subsea natural gas compression is much more complex.Hydrocarbon reservoirs don't produce nice clean gas ready to pipe to consumers. If you’re lucky it's a condensate mix with minimal hydrogen sulphide, so hydrogen metal embrittlement isn't a big problem over the long term. Regardless, the multi-phase flow needs to be separated into gas and liquid before the compressors. The gas passes through the turbine compressor while the liquid goes through a centrifugal pump. Then they are mixed again into the export line. All these pressure and temperature changes means hydrate formation can spoil the fun, so mitigations for that need to be designed in. Then throw in some magnetically levitated bearings because you’re aiming for decades long operational life in harsh media. So, yeah, pumping some sea water is much simpler.QuoteSubsea gas compression is a relatively new technology with only a handful in actual operation. The complexity and costs are high.QuoteThe cost of a water turbine, relatively well understood technology would be much less. Is it economically viable? Neither you nor I know at this time.QuoteAh, your terrified. That explains the lack of logical thoughtQuoteCalm down and think logically. The document did not say 20 year life for the concrete. You're right, concrete can and does last many decades in sea water, particularly in benign seabed conditions.The pump/generator and controls package would likely need replaced several times in that timespan.QuoteHumans have produced ahorrific amount of concrete, and with it a horrific climate-changing amount of carbon dioxide. The question is whether the CO2 required for the production of these spheres is less than they save over their lifetime. Demand for concrete globally will continue and likely increase, so hopefully we can find new ways toproduce it more sustainably.I am just making the point that your responses are generally emotive with little to no effort in the understanding of technical detail. Please use reddit for such shallow discussions, not an engineering forum. Subsea pumped hydro may or may not be a viable solution for grid energy balancing. There may be better solutions, but it has enough merit to warrant investigation.

author: rob77
author_rank: Super Contributor
timestamp: February 07, 2022, 02:10:26 pm
content: Quote from: voltsandjolts on February 07, 2022, 10:51:36 amyes i'm illogical irrational so we must support this impractical startup and let the governments waste taxpayer money. abandoning investment after 20 years and creating negative impact is terrifying...Quote from: voltsandjolts on February 07, 2022, 10:51:36 amand we're again back to the impractical and expensive (probably even impossible) maintenancethe very point everyone is fighting against... i was thinking logically and logic says either needs to be maintained (back to the initial problem) or abandoned after 20 years.Quote from: voltsandjolts on February 07, 2022, 10:51:36 ami said "abandoning concrete structuresis definitely not green" - you excluded 1 word and literally changed the whole meaning.... so you're reacting to your fabricated sentence while pretending it's mine ? ... i think you should move over to reddit

author: voltsandjolts
author_rank: Unknown
timestamp: February 07, 2022, 02:48:40 pm
content: Quote from: rob77 on February 07, 2022, 02:10:26 pmSo, your main argument against this idea is difficulty of maintenance. I suppose I can forgive that, as my judgement is based on a career which for the most part has been in subsea and subterranean engineering. You perhaps don't have the benefit of that, I mean, seeing the difficult engineering challenges that can be overcome when the finances are viable. Sure, there are challenges in fitting a subsea turbine in a retrievable package, for maintenance or replacement from a vessel. But I've seen similar challenges end successfully. So I don't see it as unsurmountable. You do.QuoteThat was not an intentional miss quote, in fact I don't think it means much.Neither creating or abandoning concrete structures (in the way we manufacture cement today) is sustainable.But the point is that with maintenance of the turbine package, the concrete structure is not abandoned.

author: rob77
author_rank: Super Contributor
timestamp: February 07, 2022, 04:52:49 pm
content: Quote from: voltsandjolts on February 07, 2022, 02:48:40 pmi'm not saying it's impossible - i said "impractical, expensive andprobably evenimpossible maintenance"... and the fact they're presenting the solution with a lifetime of only 20years and don't mention anything about maintenance is very trangefor the maintenance you would need high accuracy in a depth of 750m. you say you have experience in sub-sea stuff... then you know you need expensive ROVs (or divers) to aid the operations.. expensive sea-cranes , insurance, weather must be good to perform such a lift. so it's definitely expensive.you say it's not a problem, so try to get a quote for such a operation and share the resultsreleasing ~ 20 bolts in a depth of 750m and lifting a several ton assembly from that depth , then lowering it back down 750m while placing it accurately into the hole and fasten those bolts. and let's not forget the electrical connections as well. ( 18-20 bolts is what seems they have on the prototype, final might be even more)i just hope the representatives of the governments considering this solution will ask the questions about maintenance and lifespan before investing into it.

author: voltsandjolts
author_rank: Unknown
timestamp: February 07, 2022, 05:41:51 pm
content: Quote from: rob77 on February 07, 2022, 04:52:49 pmOK, it's your turn for a misquote, I said I don't see it as anunsurmountableproblem.Of course, like all grid-scale engineering, it's expensive. Like a700km subsea interconnectoror a£9Bn offshore windfarm.QuoteI am sure they will since the real question is the economic viability and that takes time to assess. Not a job for a 10min rant on eevblog like batteriser was.

author: f4eru
author_rank: Super Contributor
timestamp: February 09, 2022, 08:14:51 am
content: Quote from: Marco on February 03, 2022, 08:20:53 pmA concrete structure needs regular maintenance, especially when subjected to salt water.Under extreme pressure salt water, the salt and water will penetrate deeply and quickly.

author: voltsandjolts
author_rank: Unknown
timestamp: February 09, 2022, 09:58:11 am
content: https://newscenter.lbl.gov/2013/06/04/roman-concrete/Quote

author: voltsandjolts
author_rank: Unknown
timestamp: May 31, 2025, 12:18:12 pm
content: Waking a thread that's been sleeping for 3 yearsQuote from: voltsandjolts on February 02, 2022, 12:48:58 pmSo, 3 years ago theFraunhofer Institute built a 10 foot concrete sphereto test the idea of storing energy in spheres on the ocean floor. They're still plugging away at it now, and are going to launch a 30 foot sphere off the coast of california.https://www.popularmechanics.com/science/energy/a64930513/concrete-batteries-energy/QuoteHmm, from 10ft sphere in 2022, to 30ft sphere in 2026.The 330Ft sphere seems a long way off.

author: Marco
author_rank: Super Contributor
timestamp: June 01, 2025, 09:44:28 pm
content: It's completely dependent on net zero with renewables to become economical, so kind of hard to find funding.

author: Someone
author_rank: Super Contributor
timestamp: June 02, 2025, 12:04:48 am
content: Quote from: Marco on June 01, 2025, 09:44:28 pmStorage doesnt care what the source of energy [or arbitrary commodity] is, all thats needed is enough variation in wholesale price relative to the cost of the storage. As people move energy use away from piped gas with its inherent storage mechanisms to electricity the "peaking" in the electricty demand will increase and make electricity storage more valuable.

author: Marco
author_rank: Super Contributor
timestamp: June 02, 2025, 02:06:09 pm
content: Nuclear doesn't need storage on this scale, just some batteries to give it time to adjust power.This is competing for multiday renewable storage. Don't think it could compete for dunkelflaute or seasonal storage though, which is a problem. If you build week/month storage for renewables any way with a different technology, is there room for this?

author: voltsandjolts
author_rank: Unknown
timestamp: June 02, 2025, 03:28:51 pm
content: IIUC Nuclear is base load, normally max'd out. The variation is the bit on top of the base load.

author: nctnico
author_rank: Super Contributor
timestamp: June 02, 2025, 04:41:38 pm
content: Quote from: Marco on June 02, 2025, 02:06:09 pmI don't think so. According to the article linked a few posts before, the world wide capacity is less than 1TWh using the concrete spheres. To put that into perspective: the UK, Netherlands and Germany project needing a combined storage of 200TWh by 2050. This is very doable when using hydrogen. The Netherlands alone (which is a very tiny country compared to the UK and Germany) has a best case capacity for storing over 250TWh of hydrogen.

author: Marco
author_rank: Super Contributor
timestamp: June 02, 2025, 04:57:08 pm
content: Quote from: voltsandjolts on June 02, 2025, 03:28:51 pmIt is what you design it to be.https://snetp.eu/wp-content/uploads/2020/05/SNETP-Factsheet-7-Load-following-capabilities-of-nuclear-power-plants.pdfThey can modulate enough to handle everything, with batteries.

author: johansen
author_rank: Super Contributor
timestamp: June 02, 2025, 11:53:18 pm
content: Quote from: voltsandjolts on May 31, 2025, 12:18:12 pmyeah that's going to be a monster with trouble transporting. however, and this is a probably a bad idea.. you could 3 d print it.. in the water. big plastic tarp and let the weight of the concrete start to sink it.as for the maintenance, you don't even have to bolt the pump assembly to the tank. a flange on top will be compressed shut the moment you start pumping water out of the tank.if you had an individual power cable for each unit long enough to reach the surface, you don't need to cut the power cable underwateror, a power cable long enough such that you tow the pump sideways towards shore, and lift it as you do. (no wastage on the cable length with such a scheme.