5 ms·

There are a bunch of these seemingly questionable ideas out there trying to score funding. A few years ago there was one to run a train up a mountain or create

There are a bunch of these seemingly questionable ideas out there trying to score funding. A few years ago there was one to run a train up a mountain or create a giant compressed gas reservoir underground. It may seem strange to use energy density in this context but in many ways those are even worse than batteries due to the massive amount of work they require and poor scalability because of all the physical infrastructure and space. In fact, this exact scheme looks to have been posted to HN in 2014. From my understanding they are looking to re-purpose holes that have already been dug, for the most part, which is a good idea, but if the planned prototypes are only doing 250 kW nameplate with maybe 100 KWH of stored power, there is almost no way it's going to beat a battery plant you can have more or less just built to order already commercially. And said battery plants aren't even remotely good enough at purpose for meaningful energy storage, they're mostly used for what are considered "ancillary services" in the US power markets, like eating or producing reactive power, voltage support, etc, because the modern grid scale inverters can react to grid conditions faster than grid frequencies (50-60 Hz). More rarely they might be scaled big enough to shave the peak off a demand curve for 5-10 minutes to save transmission capacity or congestion. Keep in mind all this in happening when LNG is basically free except for the cost of moving it, so you can also put in 1-60 MW combined cycle gas plants in short amounts of time with very well understood technology and proven manufacturers.

dragontamer 6y ago
> create a giant compressed gas reservoir underground. The McIntosh CAES plant began in 1991 and from my understanding, has been widely viewed as successful. https://www.smithsonianmag.com/innovation/salt-power-plant-most-valuable-180964307/ https://www.smithsonianmag.com/innovation/salt-power-plant-m... That's 110 MWs for 26 hours. Probably not 2.8 GW-hrs of energy storage (they can't sustain 110MWs for all 26 hours), but this plant is probably GW-hr range. I'm pretty sure all of Li-Ion right now is less than 2GW-hrs for the entirety of the USA. --------- The 290 MW plant in Huntorf Germany (1978) also is successful. -------- There's a 2nd, 300MW+ plant (that's 300MW power for multiple hours. So near GW-hr scale as well). This is the more recent Apex Bethel Energy Center you were badmouthing earlier. Its not fully built yet, but given the history of CAES, I'm optimistic. -------- There aren't many CAES plants in the world. But from what I can tell, they are all safe and successful. The one issue is that you need to reheat the air as it leaves the caverns: compressing it underground reduces its temperature. A bit of natural gas is used in this heating process, but not nearly as much as an actual natural-gas plant. ------------ The "Rail up a hill" project is 50MWs with 12.5 MWhr storage capacity: https://s3.amazonaws.com/siteninja/multitenant/assets/21126/files/original/ARES_Nevada_Technical_Specification_Sheet.pdf https://s3.amazonaws.com/siteninja/multitenant/assets/21126/... 50MWs is somewhat small, but there's something to be said about the simplicity and ease-of-deployment of rail energy storage. Those 50MWs were spec'd out with only 7 trains. It isn't too hard to imagine scaling the system up to support more than 7 trains.
- reincarnate0x14 6y ago
  Indeed; I'm not sure why exactly so few of the CAES plants have been built, it's well understood, has minimal safety problems, and doesn't seem unreasonably expensive. If I had to wager an uneducated guess, workable salt mines may not be located anywhere the power pricing makes sense for long term storage offsetting like that.
  - jbay808 6y ago
    Compressed air storage has very bad efficiency, due to the adiabatic heating and cooling when the pressure changes.
- owenversteeg 6y ago
  Yeah, I have to say I'm actually pretty impressed with the "rail up a hill" thing. Sure, 50MW isn't a ton, but it takes up nearly no space, infrastructure is very simple (5 miles of plain electrified track and that's it!), doesn't even need a crazy grade (7%), and most importantly: locomotives are cheap. IIRC, less than a million bucks for a good DC electric one, used. So you can be up and running pretty cheap and simple. I'd love to see people running more of these setups. Especially in places where DC locomotives are cheap (former CIS countries), this could be even more cost effective.
mNovak 6y ago
Brief reminder that the predominate means of energy storage is literally pumping water up a mountain to flood a valley. On the surface, it's equally zany sounding, but of course the massive storage potential there is the big selling point.
- mc32 6y ago
  Do you mean actual mechanical pumping or are you confounding the water cycle in this which is what most people would call hydro power?
  - dragontamer 6y ago
    https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta... Pumped Hydro energy storage is the #1 energy storage in America, and probably the world. A single plant provides 24GW-hrs of energy storage, dozens of more energy storage than all American utility scale Li-Ion batteries combined. Bath County is the biggest pumped-hydro battery in the USA (and probably the world), but there are dozens of pumped-hydro plants across the country. ------------ Turns out that all the water in a lake can hold a huge amount of potential energy through gravity: just pump it up a mountain.
    - mc32 6y ago
      Thanks for the link and apologies for the skepticism. I didn't know we had systems that basically slosh water from upper to lower during high demand and lower to upper during low demand to even out capacity.
  - wtracy 6y ago
    https://youtu.be/6Jx_bJgIFhI https://youtu.be/6Jx_bJgIFhI https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit... Actual mechanical pumping.
  - Johnythree 6y ago
    That's two separate issues. In many existing hydro systems, the turbines are operated in reverse in order to store power.
foxylad 6y ago
> LNG is basically free Free as in money, costly in consequences. The whole point of energy storage schemes is to allow us to migrate away from fossil fueled energy.
ajuc 6y ago
I'm wondering why we don't use hydrolysis -> store hydrogen -> burn hydrogen -> run a steam turbine for energy storage. Efficiency would be low, at about 70% * 60% ~= 40% but capacity would be huge. 1 kg of hydrogen has specific energy of over 140 MW. We could even capture CO2 as well with that energy and make methan and use normal gas powerplants for retrieving the power :) Just build double the number of solar panels to account for efficiency loses. Should be cheaper than grid-scale energy storage with 90%+ efficiency.
- _ph_ 6y ago
  Hydrogen is difficult and consequently expensive to store. Also, the low efficiency is a problem. Pumped storage hydroelectricity is way more efficient.
  - ajuc 6y ago
    Then combine with carbon from air and store methane. Pumped is great when you have the geography for it but most countries don't. And building dams is pretty harsh on the environment too, just in different ways than CO2 emmisions.
    - _ph_ 6y ago
      Right, I think we will convert any hydrogen produced via electrolysis to methane for better storage. That methane would be completely compatible with the storage/distribution/usage infrastructure which many countries already have in place. I was commenting on the statement, that hydrogen by itself is easily stored.
  - rklaehn 6y ago
    At small scale, this is correct. At very large scale, hydrogen is incredibly easy to store. You can just fill up and old depleted gas well and store terawatt-hours of energy easily. Germany has enough gas well storage to survive several months. This infrastructure is currently used for natural gas, but it can be repurposed for hydrogen. I still think that commoditized battery storage will win in the end, but storage cost is not an argument against hydrogen.

dragontamer 6y ago

> create a giant compressed gas reservoir underground. The McIntosh CAES plant began in 1991 and from my understanding, has been widely viewed as successful. https://www.smithsonianmag.com/innovation/salt-power-plant-most-valuable-180964307/ https://www.smithsonianmag.com/innovation/salt-power-plant-m... That's 110 MWs for 26 hours. Probably not 2.8 GW-hrs of energy storage (they can't sustain 110MWs for all 26 hours), but this plant is probably GW-hr range. I'm pretty sure all of Li-Ion right now is less than 2GW-hrs for the entirety of the USA. --------- The 290 MW plant in Huntorf Germany (1978) also is successful. -------- There's a 2nd, 300MW+ plant (that's 300MW power for multiple hours. So near GW-hr scale as well). This is the more recent Apex Bethel Energy Center you were badmouthing earlier. Its not fully built yet, but given the history of CAES, I'm optimistic. -------- There aren't many CAES plants in the world. But from what I can tell, they are all safe and successful. The one issue is that you need to reheat the air as it leaves the caverns: compressing it underground reduces its temperature. A bit of natural gas is used in this heating process, but not nearly as much as an actual natural-gas plant. ------------ The "Rail up a hill" project is 50MWs with 12.5 MWhr storage capacity: https://s3.amazonaws.com/siteninja/multitenant/assets/21126/files/original/ARES_Nevada_Technical_Specification_Sheet.pdf https://s3.amazonaws.com/siteninja/multitenant/assets/21126/... 50MWs is somewhat small, but there's something to be said about the simplicity and ease-of-deployment of rail energy storage. Those 50MWs were spec'd out with only 7 trains. It isn't too hard to imagine scaling the system up to support more than 7 trains.

reincarnate0x14 6y ago
Indeed; I'm not sure why exactly so few of the CAES plants have been built, it's well understood, has minimal safety problems, and doesn't seem unreasonably expensive. If I had to wager an uneducated guess, workable salt mines may not be located anywhere the power pricing makes sense for long term storage offsetting like that.
- jbay808 6y ago
  Compressed air storage has very bad efficiency, due to the adiabatic heating and cooling when the pressure changes.
owenversteeg 6y ago
Yeah, I have to say I'm actually pretty impressed with the "rail up a hill" thing. Sure, 50MW isn't a ton, but it takes up nearly no space, infrastructure is very simple (5 miles of plain electrified track and that's it!), doesn't even need a crazy grade (7%), and most importantly: locomotives are cheap. IIRC, less than a million bucks for a good DC electric one, used. So you can be up and running pretty cheap and simple. I'd love to see people running more of these setups. Especially in places where DC locomotives are cheap (former CIS countries), this could be even more cost effective.

mNovak 6y ago

Brief reminder that the predominate means of energy storage is literally pumping water up a mountain to flood a valley. On the surface, it's equally zany sounding, but of course the massive storage potential there is the big selling point.

mc32 6y ago
Do you mean actual mechanical pumping or are you confounding the water cycle in this which is what most people would call hydro power?
- dragontamer 6y ago
  https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta... Pumped Hydro energy storage is the #1 energy storage in America, and probably the world. A single plant provides 24GW-hrs of energy storage, dozens of more energy storage than all American utility scale Li-Ion batteries combined. Bath County is the biggest pumped-hydro battery in the USA (and probably the world), but there are dozens of pumped-hydro plants across the country. ------------ Turns out that all the water in a lake can hold a huge amount of potential energy through gravity: just pump it up a mountain.
  - mc32 6y ago
    Thanks for the link and apologies for the skepticism. I didn't know we had systems that basically slosh water from upper to lower during high demand and lower to upper during low demand to even out capacity.
- wtracy 6y ago
  https://youtu.be/6Jx_bJgIFhI https://youtu.be/6Jx_bJgIFhI https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit... Actual mechanical pumping.
- Johnythree 6y ago
  That's two separate issues. In many existing hydro systems, the turbines are operated in reverse in order to store power.

foxylad 6y ago

> LNG is basically free Free as in money, costly in consequences. The whole point of energy storage schemes is to allow us to migrate away from fossil fueled energy.

ajuc 6y ago

I'm wondering why we don't use hydrolysis -> store hydrogen -> burn hydrogen -> run a steam turbine for energy storage. Efficiency would be low, at about 70% * 60% ~= 40% but capacity would be huge. 1 kg of hydrogen has specific energy of over 140 MW. We could even capture CO2 as well with that energy and make methan and use normal gas powerplants for retrieving the power :) Just build double the number of solar panels to account for efficiency loses. Should be cheaper than grid-scale energy storage with 90%+ efficiency.

_ph_ 6y ago
Hydrogen is difficult and consequently expensive to store. Also, the low efficiency is a problem. Pumped storage hydroelectricity is way more efficient.
- ajuc 6y ago
  Then combine with carbon from air and store methane. Pumped is great when you have the geography for it but most countries don't. And building dams is pretty harsh on the environment too, just in different ways than CO2 emmisions.
  - _ph_ 6y ago
    Right, I think we will convert any hydrogen produced via electrolysis to methane for better storage. That methane would be completely compatible with the storage/distribution/usage infrastructure which many countries already have in place. I was commenting on the statement, that hydrogen by itself is easily stored.
- rklaehn 6y ago
  At small scale, this is correct. At very large scale, hydrogen is incredibly easy to store. You can just fill up and old depleted gas well and store terawatt-hours of energy easily. Germany has enough gas well storage to survive several months. This infrastructure is currently used for natural gas, but it can be repurposed for hydrogen. I still think that commoditized battery storage will win in the end, but storage cost is not an argument against hydrogen.