“ perfect for capturing the energy of heavy weights being dropped down a shaft”
Well if carbon capture takes off, there will be plenty of weight that can usefully be put underground…
The deepest metal mine in Europe, unused since 2022, is set to host a giant underground gravity battery. Pyhäsalmi Mine, located 450 kilometers north of Helsinki in Finland, runs deep into the Earth – 1,444 meters, or around 0.9 miles, to be precise. With its copper and zinc deposits depleted, Pyhäsalmi has a lot of vertical …
I don't want to sound like one of those "Oh, I already invented that" type of guys, but it did occur to me several years ago that those vast, disused open-cast mines could be sub-divided using a steel framework into hundreds of "lift shafts", each containing a gravity battery.
However, such a scheme would take a long time to recoup its investment cost—although its relatively simple mechanical and electrical construction means that it would probably enjoy a very long lifespan.
Wow, how much power could Google generate by dropping everyone's laptops down a tunnel every time Google Drive is updated? I would have had to throw down my Windows 7 PC, my Windows 8 PC, and my Windows 10 PC's so would new software upgrades create energy? Is this the new world?
I feel like cooling carbon dioxide to at least -80° to solidify it so that it can be dropped would probably take more energy than the battery would be able to generate.
CSS is a pipe dream, usually pointed to by industralists to say "look, it's so easy *and* we wouldn't have to sacrifice anything!". It's been "coming soon™" for the past few decades.
Pedant alert: if your uranium is sufficiently enriched as to sustain a chain reaction, it doesn't stay in a big pile for much more than microseconds. If it isn't enriched yet, then it isn't much use as a store of energy.
What you want is a number of smaller piles, depending on the level of enrichment. Citing Wikipedia: "The critical mass for lower-grade uranium depends strongly on the grade: with 20% U-235 it is over 400 kg; with 15% U-235, it is well over 600 kg."
Possibly a good point. There'd be no need to haul the weight back up. Just store it down there when it reaches the bottom and only haul up the cable/hook ready for the next load making it even more efficient. The people working down shuffling the heavy drums into the storage areas can go down during periods of high demand, thus assisting in the generation of power and can stay there until the power cost of bringing them back up falls to off-peak rates. Trebles all round! :-)
IIRC, there was an issue of Bob Burden's Flaming Carrot comic in which a mad scientist was "harvesting cellulite from socialites" to convert into a new high explosive. I don't recall if the Mystery Men (who later received a film adaptation, though it wasn't very faithful to the source material) were featured.
Nice.
I pictured a similar theme for a Judge Dredd plot.
Van cruising Mega City One with guys on foot coming up behind some it's heavier citizens and tasering them. The vans meeting up at an old warehouse where a fitted out container lorry houses their "collecting machine."
The title? "The Fat Farmers" of course.
《Even body fat (38MJ/kg) has a higher energy density than coal (24-35MJ/kg) does; we only really use it because it was the easiest thing we could find in the 1800s.》
During the 19th century as at any time, the poor were emaciated with no body fat to burn but I am sure the industrial revolution would have shoved them into the furnaces, which it did metaphorically, if they had been a bit chubbier.
Petroleum would be roughly the same energy density I imagine fat ~ triglyceride (glycerol + 3 fatty acids) ~ 3 alkane molecules.
I think the unusual geology of the british isles meant coal was always going to be the driver of their industrial revolution. And I suspect its also pretty difficult to make steel with lard (to replace coke.)
You jest, but a few years ago there was a leisure centre somewhere in the UK that was using waste heat from a neighbouring crematorium to heat the swimming pool. I think the scheme stopped after some public outrage (personally I thought it was an OK idea, but the way people reacted you'd think they'd proposed using ashes from the crem to top up the kids' sandpit)
That'll likely be my local pool, Abbey Stadium in Redditch although there may be others. The morons who write and read the Daily Mail branded the plan "sick" back in 2011 when it was first cooked up (fnarr fnarr), but despite a few moaners there was no local outcry, and as far as I know, living in the area, it's still functioning. At the planning stage was expected to save 40% on the leisure centre's gas use.
The only downside is that they've missed a trick, of a dot matrix sign above the pool "Heat in your swimming session courtesy of the late Robert Smythe", although I'm confident that the reality is that around 90% of the heat is actually from the mains gas used by the crematorium burners, rather than the recently deceased.
I'd imagine you have to use the mine soon after it's stopped. Putting complex mechanical things into disused mines is probably not a very good idea. In order for a mine to be a safe working environment, you need pumps to keep the water out and circulate the air. After all you're going to need to maintain the motors - although at least they're at the top. So I'm sure it's not an insurmountable problem, but you're also going to need to inspect the structural integrity of the shaft every so often.
Mines deteriorate (and bits of them fill up with water) when they're not being used. So there's going to need to be a certain amount of re-commissioning.
Also the idea that the US has half a million ex mines, "with many suitable for this", is ludicrous. I'm sure there are hundreds of thousands of tiny amateur built mines from the 19th Century scattered about the place, but ones with shafts large enough for this kind of thing are likely to be much rarer. And I'd guess that ones also in a fit state to be used without major ongoing maintenance are even rarer.
MW IS NOT A UNIT OF ENERGY STORAGE.
If this is 2MW for 30 seconds it's not much use. If it's 2MWh then it's barely worth doing compared to battery storage.
Give us a value in MWh or Joules. Barrels of Oil Equivalent. Or reword it to it reducing a maximum of 2MW of power.
Come on, Register, you used to call out other publications for this sort of crap. Be better.
Agree - it's awful reporting.
2MWh would be ~7e12 J
500m drop, that's 5kJ per kg, you want about 15 thousand tons.
Granite is about 2.6-2.7 times as dense as water, call it three and that's 5 thousand cubic metres of rock...
I rather hope they're using train cars and rails so that they can have a few weights on the cables at all times, and just scoot them off to the side at the top and bottom.
But even 2MWh is worth doing - this is a battery, it's just not a chemical one. It has different properties and different costs (many of which have already been paid for by the mining operation).
Of course the key here is that they have the main shaft available for a future project as well...
"The advantages of Gravistore include low cost and longevity, which make the system an attractive option for repurposing inoperative mines. Initial costs are minimal because the basic infrastructure (i.e., the mine itself) is already built. Gravitricity also asserts the Gravistore system can function for decades without significant maintenance challenges and store more than 20 MWh."
Steady on, I think that's a bit unfair. We accidentally missed off the hours in megawatt-hours. It's now fixed.
We're a small team that's trying to do a lot, and we're gonna sometimes slip up. We try our best not to, but it happens. And when we do mess up, we try to fix it ASAP. Dropping us a note directly helps us get an update out faster.
I think awful is a bit harsh.
C.
Wish I could give you more than one upvote.
Apparently, this thing has "1000s of tonnes" of mass according to their webpage. (having been inside a mere 150 tonne crane, I have to say 'yeah, right', but assuming their marketing droids have any decency then it is at least 1000 tonnes.) m g h says that 1 kg m = 9.81 Joules. So 1000 tonnes is 9810 kJ/m and so at 1444m you have 14 GJ = 4 MWh per 1000 tonnes. Probably more like 2MWh after the efficiency of the gearbox and motor
14 GJ = About the same as 3 tonnes of TNT apparently. So your lump of mass is going to turn into 3 times its weight in TNT if you drop it. :D (well, ok, air resistance. But still a bloody great bang. And in an eathquake zone.)
Living next to what used to be a major ship building area, I can testify that very large lumps of steel being dropper, even from a relatively low height, makes a very loud noise!
There's little to no actual shipbuilding here now, but still an industrial riverside economy of ship repair and other maritime stuff that still involves lifting heavy lumps of steel which, thankfully quite rarely, get dropped nowadays.
《Come on, Register, you used to call out other publications for this sort of crap. Be better.》
Isn't there an el Reg unit for energy (work?) UK politics abounds in inspiration.
Even the "old money" outside the US is sufficiently obscure to serve - foot-pound.
The power unit foot-pound-second could be a Liz or a Truss ~ Boris' successor (second) certainly put the boot (foot) into the pound.
The unit of energy would be 1 Truss x 50 days or 1 Lettuce = roughly 5.9MJ (1.3558J/fps×50d×24h/d×60m/h×60s/m.)
All heat as cannot see a feasible means of extracting any useful work from this unit of power although dropping current and former UK PMs down 0.9km mine shafts to extract useful work is an idea whose time may have come.
Yes, we made an error. It happens. We try to avoid them. If software has bugs, articles have mistakes. We try to fix them as soon as we can, and prevent them in the first place.
It should be - and now is - MWh. It's now corrected. Don't forget please to email corrections@ if you spot anything wrong so we can sort stuff out ASAP.
C.
Do you have a source for the 2MWh figure or have you simply changed the unit?
As it happens, I reckon it IS about 2MWh based on the weight and drop, but I haven't found a source for that.
It was an error, but it was not really your error. Your source The Herald also says "2 Megawatts of Storage", as do other news outlets, so I assume it must have been in the press release.
The complaints here are just a general lament at the media's misuse/conflation of scientific terms, especially power vs energy. It's not just the Reg, it's everyone. But the Reg used to be better.
The Reg used to be better than the other sites. I've been here quite a long time now.
One thing that still sets it apart though is its excellent forum, where one can get called a Boring Prat by some Anonymous Coward
https://www.oed.com/search/dictionary/?scope=Entries&q=Enshittification
This post has been deleted by its author
If you use electricity to split water into hydrogen and oxygen the bubbles will rise. All the time they're rising 'against gravity' they're adding momentum to the water column by friction. A 'down' return pipe is needed. At the top you'll get a fountain of water and bubbles. Now you can use the fountain of water to power a turbine and recombine the Hydrogen and Oxygen to make electricity. Now send those electrons down to the bottom and repeat. Power with no emissions and no dependencies on nature. My invention described 25 years ago.
That article about your invention... are you aware of Betteridge's law of headlines?
Interesting variation on the water wheel; extracting energy from gravity.
Should be possible to build a simple proof of concept model that attempts to power a toy motor (eg. Scalextric).
Trouble will be scaling the thing up, which is probably also the problem here; it is relatively easy to build a gravity motor that can power a light bulb or tv for a few hours, but scale it to 1000’s of homes…
"Interesting variation on the water wheel; extracting energy from gravity."
No - there is no extraction of energy going on here.
The water wheel relies on mass flow of water down a hill, with the return trip being made by solar energy driving evaporation, cloud formation and finally rain.
You could consider a long pipe going down to a geothermal vent on the sea floor, but there are almost certainly better ways of extracting that energy.
Gravitational potential energy - because the water is being lifted by an external force (solar energy) and then we capture some of that energy on the return trip.
The described mechanism doesn't actually allow for energy to be extracted.
I was going to say the same.
"2 megawatts of storage capacity, enough to power roughly 1,500 homes"
2 Megawatts is a peak output, not a storage capacity. 2 megawatts powering 1500 homes would mean that each home consumes 1.3kW each on average (or 32kWh per day); high for Europe, but maybe reasonable for the USA.
But if it's running at 2 megawatts, how long can it run for? That's what gives the storage capacity.
On the other hand, if it has a storage capacity of 2 Megawatt-hours, then it doesn't mean anything to say it could power N homes, unless you say how *long* it can power them for. Using the same figures as above, it could power 1500 homes for 1 hour, or 3000 homes for 30 minutes, etc.
Now, if they told us the *weight* of this gravity device, we could work it its capacity. To get 2MWh of potential energy, you need a weight of 1384 tons lifted through 530 metres (ignoring conversion losses)
Yeah, we know, we know, we accidentally left off the hours in megawatt-hours. W is the rate of energy being transferred or transformed, and Wh is a quantity, we get it.
Sometimes articles have mistakes. We try to fix those ASAP. Please don't forget to email corrections@ to get our attention straight away - we check that constantly and comments only when we have time.
C.
When you look at the maths the amount of energy stored in even an extremely substantial mass at a substantial height is pretty pathetic compared to any chemical battery.
The efficiency isn't particularly great either.
Works out OK-ish as an idea if you have space for a massive pumped storage gravity battery but anything else is usually an exercise in futility.
You can get a 2MWh lithium battery into a standard 40ft container for a relatively tiny amount of money, or you can mess around building a massive gravity one for multiples of the price in construction & operation for a horrible ROI compared to almost any other use of the site.
The idea with "gravity batteries" is that they're really cheap to build - as long as someone else already dug the massive hole.
It's a mineshaft, mothballed less than two years ago.
Nearly all the necessary equipment is already installed, it "just" needs maintaining and the lift filling with something heavy.
The maintenance isn't free, but it's well understood and pretty cheap.
If you like devastating science based put downs you'll enjoy this article on why almost all gravity batteries are useless.
"...A kilometer deep shaft with a massive elevator full of two meters of sand worked by a couple of the biggest winches ever built and it’s only as much as a third [as much storage] of a Tesla Megapack that’s 29 feet long and 8.5 feet tall..."
https://cleantechnica.com/2024/01/16/gravity-storage-101-or-why-pumped-hydro-is-the-only-remotely-real-gravity-storage/
Interesting...all the articles on gravity based storage have been removed today.
Wonder if someone got the lawyers onto them
Still, we have archive. Org
https://web.archive.org/web/20240116065953/https://cleantechnica.com/2024/01/16/gravity-storage-101-or-why-pumped-hydro-is-the-only-remotely-real-gravity-storage/
The assumption most people make is that there can only be one mass.
And that gravity storage must be the complete solution to all mankind's needs.
Having mining winches over an existing mineshaft, which likely has a rail system top and bottom already, makes it a reasonable thing to consider in a variety of places. You certainly don't "tip sand out and push it around" as is suggested in the article, you lower a mass onto a rail cart and then push *that* away, whilst the next mass is only a few tens of metres above, ready to drop onto the next cart... And at the top you lift it onto a rail cart, and push that away...
Rail carts are very efficient, we've spent a couple of centuries optimising those.
It's not a months long continuous generation facility, but it also doesn't suffer from losses by holding energy for a long time - though it would likely want to look at shorter cycling to make maintenance worthwhile (and there will be maintenance).
The more options we have the better, and whilst this clearly isn't going to become a dominant storage mechanism there is some value to using infrastructure which already exists to try different things.
Pumped hydro has a couple of really BIG advantages, and one really BIG disadvantage.
- The disadvantage first... it's very dependant on local geography and preferably the previous existence of two convenient lakes.
- The biggest advantage is that it has some external energy supply, which should really boost efficiency.
- The other is that noone really complains about a really big pile of water on the ground, as opposed to various towers or similar for less realistic storage proposals.
So yes, if you want lots of storage then a substantial height pumped hydro is the best "gravity storage", but if you don't have the geography then you either import, or you use what you have - and if you have local mines, then some of those might be able to provide useful storage in that area.
One of the biggest issues, which the article mentions and then ignores, is that whilst pumped hydro probably gets free energy from additional rain... any water ingress to a mine needs to be pumped out...
Put an exercise bike into every household. Equip it with an inverter. Plug every one into a wall socket. BOOM, everybody is responsible for putting 1 kWhr into the wall, per person, per day.
The BBC did a show where they got a warehouse full of cyclists to power a house. IIRC it went well until they tried to use the oven
What they needed afterwards -->
Wasn't there a Top Gear segment where James tried to charge a car using an office building's revolving doors?
Munroe's What If? 2 has a bit on whether a cyclist could power a toaster. You wouldn't want to try.
A cyclist could power an EZ Bake Oven, though. Those used a 100W light bulb, and that's feasible for a human. Of course it's a ridiculously inefficient system, though if you need the exercise anyway then it's not really wasted¸ I suppose. "Yes, I did 10 miles on the stationary bike, and baked a little cake for afterward."
I give it a year before they discover their "invention" is not efficient (massive drag losses everywhere with WAY too many moving parts) and their longevity is actually shit even compared to batteries.
The energy density of their storage solution is absolutely abysmal and likely even just having large tanks at the bottom and a few pipes for water would be a better and more efficient solution. But selling pumped hydro as new or "innovative" isn't as easy.
The ideas for this bullshit have been around for eons, it's never gone anywhere and will never go anywhere. It's one of those things where a the engineers involved at some point should have been given a slap to the face and told: No! Your ideas are bad and you should feel bad!
For pumped-water gravitational-potential storage it would have the advantage of a safer failure mode than "store it on top of a hill" — water flooding the mine is nicer than water flooding the surrounding countryside. But the disadvantage of higher installation and maintenance costs (plumbing up and down a hill is easier than doing it up and down a mineshaft) on what is already a marginal storage solution probably makes it economically infeasible, I'd guess.
If the goal is efficient storage of energy, then it's clearly not going to work.
If the goal is efficient extraction of cash from venture capitalists that don't understand science and will speculatively invest in any green energy scheme, then it will probably work extremely well for as long as they can string along the investors.
A lot of mines fill up with water . So either you have lost some efficiency through bouyancy and friction drag moving weights in water .. and have a short lifetime of any equipment because the whole thing is going to be running in often corrosive acidic water.
And in many mines below the water table you have to spend constant energy pumping water out, lifting it up against gravity. Water which naturally reaches the bottom of the mine shaft without you extracting energy as it falls.
Physics wins. Or chemistry.