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Europe's deepest mine to become giant gravity battery

independent.co.uk

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Re: Europe's deepest mine to become giant gravity battery

#71

Post by ZeroGravitas »

pfdietz wrote: post #36
jcrawfordor wrote: post #10

Earlier quoted context omitted.

You might be surprised how few sites are suitable for pumped hydro and how costly it is to build. I can easily see this being both cheaper and more efficient. Most pumped hydro installations outside of northern Europe end up requiring large dams to create a big enough impoundment uphill. A direct weight solution should have better conversion efficiency as well, Gravitricity quotes 80% which is on the high end of pump…

You might be surprised at the enormous numbers of sites that are potentially suitable for pumped hydro, if you go looking for them in areas with vertical relief. https://re100.eng.anu.edu.au/global/ "ANU has identified 616,000 potential sites around the world." (note that not all countries are included in this because of lack of geographical elevation data) A place like Nevada has an enormous surfeit of opportunities…

I doubt any pumped storage project can beat solar and battery hybrid projects these days, especially in sunny places like Nevada.

People get very laser focused on the storage part, but energy you generate is entirely fungible with energy that you've stored so pumped hydro needs to compete with generation too.

edit: looking further into this to try to put some rough numbers on it, the 5 years it'll take to dig the holes means in this particular case I wouldn't be too surprised if batteries alone could beat it by the time it connects to the grid in 2031.

Re: Europe's deepest mine to become giant gravity battery

#72

Post by danbruc »

Someone wrote: post #68
GuB-42 wrote: post #25

Isn't there a better article? - 2 MW of energy MW is a unit of power not energy, maybe they mean 2 MWh, but if that's the case, it is a joke. That's like 30 Teslas cars, or half of a Tesla Megapack, which is a shipping container sized battery. 2 MW of power is not that big either, that's about what you get from a typical wind turbine. - 70TWh of energy At least, we have a proper unit, but I wish they tell us a bit mo…

> At least, we have a proper unit, but I wish they tell us a bit more about how they got a number 7 orders of magnitude larger than the previous one. The 70TWh isn’t for this mine, but globally. FTA: “A study last year by the International Institute for Applied Systems Analysis (IIASA) estimated that gravity batteries in abandoned underground mines could store up to 70TWh of energy – enough to meet global electricity…

Which again is nonsense as stated. The average world energy consumption is about 3 TW and gravity storages produce exactly zero and can meet no demand at all. 70 TWh would be enough to store about one day of global electricity consumption, for example to smooth out solar and wind.

Re: Europe's deepest mine to become giant gravity battery

#73

Post by Faaak »

danans wrote: post #59
mhandley wrote: post #31

Dry sand has a mass of 1600kg/m^3 Potential energy, U = mgh. So the energy required to raise 1m^3 of sand 1400m is 1600 x 1400 x 9.8 = 22MJ = 6.1kWh I've no idea how large their mine galleries are, but lets say they're 3m wide x 2m high - in 500m of gallery, we can store 3000m^3 of sand, so that's 18MWh. I'm sure they've got a lot more space than that, but it just gives some idea of how much sand you're talking about…

> Potential energy, U = mgh. So the energy required to raise 1m^3 of sand 1400m is 1600 x 1400 x 9.8 = 22MJ = 6.1kWh If you lowered 10 m^3 of sand (61kWh of potential energy), to generate the minimum 100kW power to participate in grid stabilization markets, you'd have to drop that 16000kg of sand for 61kWh/100kW = 0.61hr = 2196 sec. 1400 meters in 2196 seconds is 0.64 m/sec. That seems reasonable, but you'd need a lo…

I've participated in grid stabilization in Switzerland (ancillary services), and 100kW is absolutely nothing. As far as I recall, 10 years ago, the minimum needed to become a participant was 10MW

Re: Europe's deepest mine to become giant gravity battery

#74

Post by RugnirViking »

bluenose69 wrote: post #8

The phrase "2 MW of energy" makes no sense based on units. Shouldn't writers (and editors) be required to at least take high school physics or chemistry?

to be fair they might be somewhat confused by marketing copy. I've worked on installations like this, and its not uncommon for capacities to be specified as something like 50MW battery (4 hours). sometimes the number of hours is written in a different place to the base output capacity. I think it started because originally the idea is that the battery is some number of hours multiple of the production of a generating asset, like on-site wind. In fact capacity payments and stuff in some countries (read: subsidies) can be different based on the number of hours of the battery

Re: Europe's deepest mine to become giant gravity battery

#75

Post by shellfishgene »

XorNot wrote: post #13

Huh...this is literally the "heavy weight" sort of gravity battery rather then pumping water. I'm...not really convinced this is going to be viable. 2MWh (which is what I assume the article means) is not a lot of power at all (about 40 days of my roof top solar production) - and that's with "the deepest mine in Europe". The basic problem is that your heaviest, cheapest weight is concrete or stone which is only about…

I agree. Keeping a 1.4 km long chain of elevators with buckets of sand running, with as little friction as possible, in a hard to access mineshaft, probably with high humidity, and sand everywhere, sounds like a very expensive operation.

Re: Europe's deepest mine to become giant gravity battery

#76

Post by 15457345234 »

XorNot wrote: post #40
kibwen wrote: post #20

Earlier quoted context omitted.

I'm not sure that the density of the material itself really matters much; having the weight take up less space doesn't really reduce the overall power of the system very much (the weight is probably not occupying a very large portion of the shaft's height). That said, lead is also dirt-cheap and is more than 11x denser than water. Gravity batteries are cool. They don't make a lot of economic sense by themselves, but…

The heavier you make your counterweight, the more strength you need in your cables. The problem is that you could solve this by say, lowering a small pallet of whatever to the bottom of the shaft and moving it sideways out of the way - trading "power" for "energy storage". But if you extend that idea you wind up at "pump a liquid" as the obvious way to do it, since that has essentially no limit on flow-ability. The o…

> 1000kg of lead at 1500m high is about 4kWh of potential energy. 1000kg of Lead-Acid batteries is about 25 kWh of potential energy. I suppose you could put the batteries on a cable for the extra 4kWh but I suspect the complexity isn't worth it.

That's just so well said. Should be the top comment every single time this dumb idea is surfaced.

I'm convinced now people are pulling stunts like this just to make renewables look bad.

Re: Europe's deepest mine to become giant gravity battery

#77

Post by TheOtherHobbes »

danbruc wrote: post #72
Someone wrote: post #68

Earlier quoted context omitted.

> At least, we have a proper unit, but I wish they tell us a bit more about how they got a number 7 orders of magnitude larger than the previous one. The 70TWh isn’t for this mine, but globally. FTA: “A study last year by the International Institute for Applied Systems Analysis (IIASA) estimated that gravity batteries in abandoned underground mines could store up to 70TWh of energy – enough to meet global electricity…

Which again is nonsense as stated. The average world energy consumption is about 3 TW and gravity storages produce exactly zero and can meet no demand at all. 70 TWh would be enough to store about one day of global electricity consumption, for example to smooth out solar and wind.

That's why these projects are called batteries, not generators.

The nuke and fossil lobbies make a big deal out of how renewables are intermittent, and this is one of many practical ways to fix that.

Re: Europe's deepest mine to become giant gravity battery

#78

Post by squirtle24 »

mhandley wrote: post #31

Dry sand has a mass of 1600kg/m^3 Potential energy, U = mgh. So the energy required to raise 1m^3 of sand 1400m is 1600 x 1400 x 9.8 = 22MJ = 6.1kWh I've no idea how large their mine galleries are, but lets say they're 3m wide x 2m high - in 500m of gallery, we can store 3000m^3 of sand, so that's 18MWh. I'm sure they've got a lot more space than that, but it just gives some idea of how much sand you're talking about…

Thinking out loud here, but why sand and not water? Yes, water is only 1000kg/m^3, but probably much easier to transfer around using pumps and pipes. Water can make good use of the horizontal space within the mine, unlike sand. (The graphic in the article shows them using conveyor belts or trucks to move the sand horizontally which seems silly.) Thus the mine could basically be a mini pumped hydro power station, build a new reservoir at the top and use the mine as the bottom reservoir, then pump water water between the two.

Re: Europe's deepest mine to become giant gravity battery

#79

Post by usrusr »

usrusr wrote: post #41
GuB-42 wrote: post #25

Isn't there a better article? - 2 MW of energy MW is a unit of power not energy, maybe they mean 2 MWh, but if that's the case, it is a joke. That's like 30 Teslas cars, or half of a Tesla Megapack, which is a shipping container sized battery. 2 MW of power is not that big either, that's about what you get from a typical wind turbine. - 70TWh of energy At least, we have a proper unit, but I wish they tell us a bit mo…

Part of me certainly hated myself for not stopping to read right there. But it's an interesting approach despite the bad writing: if you fill a 1400m shaft with a dense chain of buckets (my term, they seem to call them vessels) you'll need a surprising low amount of mass throughput for a given amount of power flowing in/out. Because there is just so much in transit at any given point in time. A naive implementation w…

PS: what was up with my mind when I wrote this? (second paragraph) Some serious confusion about throughput and power: power and mass throughput are obviously the same at a given shaft height, the advantage of a chain with less gaps/more vessels in transit at the same time is that you don't need much speed to achieve throughput.

Still, the approach of stacking many copies of the same loop design, with a well designed handover mechanism remains the way to go, instead of one big elevator trying to achieve throughput by faster travel. The key core idea is that the structure that carries the upper parts of the whole thing is already there (all the ground that hasn't been dug into)

Re: Europe's deepest mine to become giant gravity battery

#80

Post by effie »

Another completely misleading article on gravity batteries. All the solid weight stuff is bunk, probably designed to suck out money from naive investors / corrupt state officials. Moving solid weights gives only a very small electric power, so building the proposed solid weight batteries gives units of MW at most, which is uneconomical. Unless it transports a large lake of water up and down a hill like in pumped-storage hydroelectric plants, and can provide tens or hundreds of MW. Such installations are very expensive to build today, because all the low-hanging fruit options seem to have been already built.
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