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Geothermal may beat batteries for energy storage

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Re: Geothermal may beat batteries for energy storage

#21

Post by Schroedingersat »

prox wrote: post #15
moffkalast wrote: post #8

Earlier quoted context omitted.

I wonder if it would be possible to scale down pumped hydro to something the size of a tall water tower. Probably not worth it due to the small height difference and volume, and you'd also lose efficiency due to the smaller turbine, but I still do wonder what the actual figures are like for something like that. Especially in cost per kWh stored compared to lithium.

Big fan of gravity well storage, it seems simple and elegant. https://energyskeptic.com/2019/gravity-energy-storage/ The above link has some numbers (2019 had it bookmarked so maybe it has improved)

That website is full of deranged ramblings which are largely disconnected from reality. Case in point:

> MY NOTE: well whoop-dee-doo. China generates 16.2 trillion terawatt-hours (TWh) a day. That’s 64 billion times more than all of the open-cast mines can provide. Better start digging more holes!

16.2 trillion terawatt hours a day is ~4 million times the total global insolation or 35 billion times total global energy usage. This is more wrong than asserting that a single man on a bicycle generator could produce our entire primary energy worldwide.

Re: Geothermal may beat batteries for energy storage

#22

Post by empyrrhicist »

moffkalast wrote: post #8
jillesvangurp wrote: post #7

Interesting option. It's all about the cost and efficiencies in the end. Converting electricity into heat and then back into electricity is a lossy process that is constrained by the second law of thermodynamics. Basically generating heat is easy and efficient. But converting it back to electricity is typically less than 50% efficient. Basically, it's several energy conversions in one process: you use electricity to…

I wonder if it would be possible to scale down pumped hydro to something the size of a tall water tower. Probably not worth it due to the small height difference and volume, and you'd also lose efficiency due to the smaller turbine, but I still do wonder what the actual figures are like for something like that. Especially in cost per kWh stored compared to lithium.

Water is just too heavy. Pressurized air would be easier.

Re: Geothermal may beat batteries for energy storage

#23

Post by Schroedingersat »

HPsquared wrote: post #14
VilleOr wrote: post #6

Earlier quoted context omitted.

Majority of geothermal enery comes from the decay of radioactive isotopes. It's not renewable, but there will be enough heat for millions of years.

It's not renewable, but exploiting it doesn't reduce the overall output. It's "not depletable", you could say.

At some point you're increasing the conductivity of the crust and mantle.

You have a bunch of bigger problems that come to roost much sooner than this if you're using that much geothermal though,

Re: Geothermal may beat batteries for energy storage

#24

Post by jillesvangurp »

moffkalast wrote: post #8
jillesvangurp wrote: post #7

Interesting option. It's all about the cost and efficiencies in the end. Converting electricity into heat and then back into electricity is a lossy process that is constrained by the second law of thermodynamics. Basically generating heat is easy and efficient. But converting it back to electricity is typically less than 50% efficient. Basically, it's several energy conversions in one process: you use electricity to…

I wonder if it would be possible to scale down pumped hydro to something the size of a tall water tower. Probably not worth it due to the small height difference and volume, and you'd also lose efficiency due to the smaller turbine, but I still do wonder what the actual figures are like for something like that. Especially in cost per kWh stored compared to lithium.

It can work, it's just a cost equation. You need a large amount of mass to get meaningful amounts of energy stored. So pumped hydro is nice because you are basically using natural reservoirs and some cheap pumps and pipes.

A water tower needs to be built first and only stores a limited amount of potential energy. The problem is not the efficiencies but the cost of building a big enough tower. A tower with the same capacity of a pumped hydro reservoir would be insanely expensive. Or alternatively building many thousands of smaller towers that add up to the same capacity would also not be cheap.

There are a few alternative gravity systems being tested out in the form of e.g. big cranes with weights that drive generators, mine shafts with similar systems, etc. Proving they work efficiently is not the issue. It's just scaling their deployment cost effectively.

Re: Geothermal may beat batteries for energy storage

#25

Post by killjoywashere »

empyrrhicist wrote: post #22
moffkalast wrote: post #8

Earlier quoted context omitted.

I wonder if it would be possible to scale down pumped hydro to something the size of a tall water tower. Probably not worth it due to the small height difference and volume, and you'd also lose efficiency due to the smaller turbine, but I still do wonder what the actual figures are like for something like that. Especially in cost per kWh stored compared to lithium.

Water is just too heavy. Pressurized air would be easier.

Joule for joule, pretty sure I'd rather be standing 10 feet from a failed water tower than a failed pressure vessel. 1/2 m*v^2. That squared gets you every time.

Re: Geothermal may beat batteries for energy storage

#26

Post by Schroedingersat »

nullish_signal wrote: post #2

One wonders what the limits of "Thermal Heat" are from small "wells"(???) up to the heat content of the Earth's ore (Heat relative to sea level) How much heat is generated by Earth's gravity onto itself? How "renewable" is Geothermal energy, truly?

The total budget for any given power source is surprisingly close to 100TW.

Geothermal, you'd cool the crust and have to drill far deeper than is possible to exceed 50TW for long.

Wind, if you exceed somewhere in the 1-10W/m^2 you slow down the wind and create turbulence.

Solar, if you use more than ~1% of the land you're radically altering the albedo and habitat (so maybe up to 200TW).

Fossil fuels create GHG and run out quickly.

Nuclear creates enough waste heat in the 100-200TW range to cause as much radiative forcing as GHG does now.

We each get our 10-100kW and that's about it for living on a planet that isn't one giant factory/heatsink.

Re: Geothermal may beat batteries for energy storage

#28

Post by nicoburns »

swayvil wrote: post #20
newyankee wrote: post #17

More the competition the better for the world. I still feel a well designed Lithium Iron Phosphate or Sodium based battery with > 5000 cycles can prove very cost effective if used properly. The high no of cycles reduces the levelized cost of storage significantly. Difficulty is scaling this to beyond 1-2 days at most.

Competition is just a euphemism for fighting. You're saying that more fighting is better. Isn't that crazy? You'd think that fighting would be wasteful and upsetting. That peace would be better. It's a crazy world.

I'm not convinced competition is a euphemism for fighting. Competition can be friendly.

Re: Geothermal may beat batteries for energy storage

#29

Post by Schroedingersat »

newyankee wrote: post #17

More the competition the better for the world. I still feel a well designed Lithium Iron Phosphate or Sodium based battery with > 5000 cycles can prove very cost effective if used properly. The high no of cycles reduces the levelized cost of storage significantly. Difficulty is scaling this to beyond 1-2 days at most.

The interesting thing is when they've been around for 30 years (providing they don't decay too much with time).

A sodium battery with 100 useful cycles and 10 years left in it is great for cycling once a month.

But even without that, if we see costs of $50/kWh then you only need to cycle 300 times to make it more worthwhile than some generation technologies..

Re: Geothermal may beat batteries for energy storage

#30

Post by swayvil »

nicoburns wrote: post #28
swayvil wrote: post #20

Earlier quoted context omitted.

Competition is just a euphemism for fighting. You're saying that more fighting is better. Isn't that crazy? You'd think that fighting would be wasteful and upsetting. That peace would be better. It's a crazy world.

I'm not convinced competition is a euphemism for fighting. Competition can be friendly.

You got any examples of "friendly, nonfighting type competition" in the business world?
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