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Gravity batteries try to beat chemical ones with winches, weights, mine shafts

sciencemag.org

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Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#231

Post by Dylan16807 »

Youden wrote: post #226
throwaway189262 wrote: post #105

This is an obvious scam if you do the math. Assuming the full scale version delivers peak power for 11 seconds like the prototype, 2MW peak power would be 6 kilowatt hours of energy. That's terrible. We're taking about dropping hundreds, maybe thousands of tons down a mine shaft to get the same amount of power as $700 of lithium batteries you could carry in a backpack. For instantaneous loads you're way better off us…

> This is an obvious scam if you do the math. Reading the rest of your comment, I'm not sure you did the math yourself... > Assuming the full scale version delivers peak power for 11 seconds like the prototype The prototype is a 4-storey tower (i.e. less than 20m). > That's terrible. We're taking about dropping hundreds, maybe thousands of tons down a mine shaft A mine shaft can be expected to be significantly deeper…

> From TFA itself, they estimate they can offer a price of $171/MWh, while Lithium-ion batteries cost $367/MWh.

With absolutely nothing to explain the cost estimate, so you can put away "TFA" thank you.

A system like this with only a single weight is going to be a huge amount of work to set up each unit of capacity.

Also looking up the info I can find, I think they're calculating that rate over a 60 year lifetime.

Edit: Uh, did I say something offensive?

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#232

Post by samatman »

throwaway189262 wrote: post #105

This is an obvious scam if you do the math. Assuming the full scale version delivers peak power for 11 seconds like the prototype, 2MW peak power would be 6 kilowatt hours of energy. That's terrible. We're taking about dropping hundreds, maybe thousands of tons down a mine shaft to get the same amount of power as $700 of lithium batteries you could carry in a backpack. For instantaneous loads you're way better off us…

Well, maybe not rocks in a mineshaft. Probably not rocks in a mineshaft.

But Advanced Rail Energy Storage?[0] Different story, has potential (bad pun, I know). There are some nice synergies, like a system such as this can reuse the generators from a decommissioned coal or natural gas plant.

It can definitely play a part in a broad-spectrum energy policy.

[0]: https://aresnorthamerica.com

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#233

Post by _liww »

throwaway189262 wrote: post #105

This is an obvious scam if you do the math. Assuming the full scale version delivers peak power for 11 seconds like the prototype, 2MW peak power would be 6 kilowatt hours of energy. That's terrible. We're taking about dropping hundreds, maybe thousands of tons down a mine shaft to get the same amount of power as $700 of lithium batteries you could carry in a backpack. For instantaneous loads you're way better off us…

Is anyone trying to implement that gas bag idea? Not one I'd heard of before

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#234

Post by ephbit »

jillesvangurp wrote: post #77
rakoo wrote: post #48

As usual everyone is fixated on price when the real hurdle will be scale. If we're going to replace our existing fossil fuel plants we need at least as much capacity. A quick grep in the article tells me these guys have a plan for a 4MW plant that involves a 1km shaft. That's the same order of magnitude as a single wind turbine, which is already one of the worst ratio of power output per quantity of resource and land…

Your assumption that we need that much storage is simply wrong. This pops up in just about any article on HN mentioning batteries. Somebody will jump to the wrong conclusion that we need to provide massive amounts of battery storage and that therefore we need coal/nuclear/etc. (i.e. really expensive ways to generate energy) because buying so many batteries is obviously stupendously expensive. It's a popular argument…

Sounds like you're mostly unaware of the issue that trying to compensate region, country and sometimes even continent wide lows/peaks would require many gigawatts of transmission capacity in the form of cables in arbitrary directions. Even if the European grid is well interconnected it's painfully far from handling such situations.

And that is not even accounting for the fact that right now only a small proportion of total energy use is transmitted electrically, which means that with future energy generation becoming greener being strongly tied to having more solar/wind (which is also electrical), there will anyway have to be a massive increase in grid capacity.

> Currently, clean energy is the dominant form of energy in many countries already (e.g. Europe, China, parts of the US)

Just not true. Yes, some countries are (Iceland is one of the few) but most European countries are far from what you claim. Maybe you meant energy transmitted as electricity instead of all energy.

See https://ec.europa.eu/eurostat/statistics-explained/index.php...

Quote: > In 2019, renewable energy represented 19.7 % of energy consumed in the EU-27, only 0.3 % short of the 2020 target of 20 %.

> The share of energy from renewable sources used in transport activities in the EU-27 reached 8.9 % in 2019.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#235

Post by rakoo »

SagelyGuru wrote: post #99
chris_engel wrote: post #85

Earlier quoted context omitted.

Hm, you also need to consider that 5 trucks can have a much higher combined output than the 1 truck 5 times as high. The storage might scale this way but not the output when demand is high.

You can make that one truck descend five times faster, giving the same output.

The total available energy in such a system is defined by

    m * g * z
where m is the mass and z is the elevation difference. It doesn't depend on the speed at which it goes down

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#236

Post by xutopia »

lebuffon wrote: post #158

I think this guy is onto something... Liquid metal batteries will be better than gravity storage IMHO. https://www.youtube.com/watch?v=NiRrvxjrJ1U First commercial scale system is going live in 2021 so we shall see how it works out.

I don't understand how that would be feasible... wouldn't the battery need to be kept at a really hot temperature somehow to function?

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#237

Post by rakoo »

yunohn wrote: post #149
lai-yin wrote: post #120

Earlier quoted context omitted.

Sorry but you don't get to discount wind turbines' ecological damage just because no more mining is involved post-construction.

Please link to a source/calculation where a wind turbine uses more resources than a coal plant to build. I mean, you can even do napkin math and see that there’s no way multiple buildings and vast mining infrastructure take less material than a turbine farm.

If you want to take a coal plant, you have to compare it with something that's comparable.

A coal plant is a 1000MW machinery. A wind turbine is in the order of 10MW. Also, turbines have a very low capacity factor so you have to double them to guarantee their output and combine them with storage. So it's 1 coal plant vs 200 turbines at the very least.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#238

Post by Dylan16807 »

Qwertious wrote: post #228
cogman10 wrote: post #212

Earlier quoted context omitted.

Right, and my point is that they aren't going to decommission all backup power until they are at the point where sun/wind/storage can actually be relied on for more than just the good days. We have a long trip to get there, so why worry about a once in 3/5 year event? We wouldn't go a year without fossil fuels and say "Ok, that was it! Demolish all the plants right now!"

Arguably, if a gas plant hasn't run for a year then it'll go bankrupt and shut down pretty soon.

In a system where it's a backup, it shouldn't be both independently owned and have revenue tied only to use.

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#239

Post by ephbit »

VLM wrote: post #196
jillesvangurp wrote: post #77

Earlier quoted context omitted.

Your assumption that we need that much storage is simply wrong. This pops up in just about any article on HN mentioning batteries. Somebody will jump to the wrong conclusion that we need to provide massive amounts of battery storage and that therefore we need coal/nuclear/etc. (i.e. really expensive ways to generate energy) because buying so many batteries is obviously stupendously expensive. It's a popular argument…

The cheapest "energy storage" is bandwidth and demand based billing. The required battery storage cost to guarantee my 3 KW electric clothes dryer could theoretically operate 24x7 when needed after three weeks of cloudy windless weather at midnight is staggering. The alternative is demand based billing and program my dryer to never accept a KWh that costs more than say, seven cents. On a minute by minute basis I don'…

Problem is: how are you going to convince great numbers of people to alter their daily routine that might also be quite synchronized across a country's population?

Like tea time in the UK where apparently millions of people turn on their kettles (2 kilowatts each) in synchrony to get some hot water.

What if they also like to cook something with their stove (another 2 KW) to get a nice dinner, around the same time?

Re: Gravity batteries try to beat chemical ones with winches, weights, mine shafts

#240

Post by mbreese »

zestyping wrote: post #223
mbreese wrote: post #216

Earlier quoted context omitted.

Does that matter though? If it is weak to extract energy with gravity, then it should also be weak to “charge” the system against gravity. The weakness may push these systems to less “instantaneous” loads, but I don’t see why it would necessarily be bad to use gravity storage (as opposed to another mechanical method like pressure). I’d love for someone to explain more though.

Because gravity is so weak, in order to store a meaningful amount of energy, the lifted object has to be very heavy or very high. Building large tall structures is expensive, and we just don't have objects that are dense enough to make the system small.

Okay, so the question isn’t “can you get out what you put in”, but rather “is the amount of energy you can store worthwhile”?
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