Geothermal may beat batteries for energy storage • Hacker News Board

Re: Geothermal may beat batteries for energy storage

#11

Post by martin_a » Tue, Oct 11, 2022, 10:58 AM UTC

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.

I saw a video like a month ago on YouTube where somebody pumped something like 250 liters of water on his roof (7 meters elevation, if I remember correctly) and let it run through a homebuild generator.

The power capacity of that setup was like that of an AA battery, if I remember correctly.

You need huge amounts of water and lots of height difference.

Re: Geothermal may beat batteries for energy storage

#12

Post by Someone » Tue, Oct 11, 2022, 11:01 AM UTC

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…

If you then use the lithium ion to produce heat, things start looking less favorable for it.

Also, I think the “geothermal” part of this means your ‘battery’ gets partly charged for free.

Re: Geothermal may beat batteries for energy storage

#13

Post by CorrectHorseBat » Tue, Oct 11, 2022, 11:03 AM UTC

VilleOr wrote: post #6

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?

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.

Surprisingly it's about 50/50 radioactive decay and heat left over from the forming of the solar system: https://en.m.wikipedia.org/wiki/Earth%27s_energy_budget#Eart...

Re: Geothermal may beat batteries for energy storage

#14

Post by HPsquared » Tue, Oct 11, 2022, 11:10 AM UTC

VilleOr wrote: post #6

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?

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.

Re: Geothermal may beat batteries for energy storage

#15

Post by prox » Tue, Oct 11, 2022, 11:17 AM UTC

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.

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)

Re: Geothermal may beat batteries for energy storage

#16

Post by Retric » Tue, Oct 11, 2022, 11:18 AM UTC

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…

Using batteries for the grid requires roughly the same amount of batteries as EV’s do. A 100kWh battery pack for a car * 1,000 charge cycles / 25 years = 4,000 kWh of battery per year * ~290 million cars. That’s enough to store almost 1/3 of all current electricity used in the US while ignoring busses and farm equipment etc.

Of course actual cost depends on how much storage we need and future battery prices but adding something like 20-50$/month on future electricity bills gets offset by both cheaper electricity from solar and wind and less excess generating capacity. In that context large scale batteries seem like a perfectly reasonable solution.

Which is supported by many current grid scale PV instillations including them so they can avoid a AC>DC step when charging the batteries and then sell during peak demand at a premium.

Re: Geothermal may beat batteries for energy storage

#17

Post by newyankee » Tue, Oct 11, 2022, 11:19 AM UTC

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.

Re: Geothermal may beat batteries for energy storage

#18

Post by Schroedingersat » Tue, Oct 11, 2022, 11:25 AM UTC

Someone wrote: post #12

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…

If you then use the lithium ion to produce heat, things start looking less favorable for it. Also, I think the “geothermal” part of this means your ‘battery’ gets partly charged for free.

Counter point is if you have work (or high grade heat) you can use it to move heat rather than just thermalising it.

Re: Geothermal may beat batteries for energy storage

#19

Post by jillesvangurp » Tue, Oct 11, 2022, 11:28 AM UTC

Someone wrote: post #12

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…

If you then use the lithium ion to produce heat, things start looking less favorable for it. Also, I think the “geothermal” part of this means your ‘battery’ gets partly charged for free.

This article is about storing energy generated using renewables in reservoirs; not about tapping into geothermal energy.

The issue with geothermal is not that the energy isn't there but that getting to it involves a lot of expensive infrastructure. It's cost effective in some parts of the world and not really cost effective (relative to cheaper solutions) in other parts of the world.

Using this instead would mean having to drill much less deep (so it's cheaper). You are sill throwing away more than half of the energy you put in though. Geothermal has similar inefficiencies except you get the energy that needs to put in for free. Not so with this solution: you have to generate the energy yourself.

Re: Geothermal may beat batteries for energy storage

#20

Post by swayvil » Tue, Oct 11, 2022, 11:28 AM UTC

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.