[HN Gopher] CO2 batteries that store grid energy take off globally
       ___________________________________________________________________
        
       CO2 batteries that store grid energy take off globally
        
       Author : rbanffy
       Score  : 99 points
       Date   : 2025-12-21 15:27 UTC (7 hours ago)
        
 (HTM) web link (spectrum.ieee.org)
 (TXT) w3m dump (spectrum.ieee.org)
        
       | AndrewDucker wrote:
       | No mention of round-trip efficiencies, and claims are that it's
       | 30% cheaper than Li-Ion. Which might give it an advantage for a
       | while, but as Li-Ion has become 80% cheaper in the last decade
       | that's not something which will necessarily continue.
       | 
       | Great if it can continue to be cheaper, of course. Fingers
       | crossed that they can make it work at scale.
        
         | cogman10 wrote:
         | I'm seeing round trip efficiencies around 75%.
         | 
         | That's not terrible.
         | 
         | These things would probably pair well with district heating and
         | cooling.
        
           | 3eb7988a1663 wrote:
           | That is shockingly good. EIA reports existing grid scale
           | battery round trip is like 82% which do not have moving
           | parts.                 ...in 2019, the U.S. utility-scale
           | battery fleet operated with an average monthly round-trip
           | efficiency of 82%, and pumped-storage facilities operated
           | with an average monthly round-trip efficiency of 79%....
           | 
           | https://www.eia.gov/todayinenergy/detail.php?id=46756
        
           | lambdaone wrote:
           | A theoretical study shows 77%, which is in the same ballpark:
           | https://www.sciencedirect.com/science/article/pii/S136403212.
           | ..
           | 
           | A few percent here of there is not that important if the
           | input energy is cheap enough.
        
           | hawk_ wrote:
           | "I am seeing" as in do you use CO2 batteries at home or
           | something?
        
         | Gys wrote:
         | Lithium supply is limited. So an alternative based on abundant
         | materials is interesting for that reason I guess?
        
           | _aavaa_ wrote:
           | Lithium is not that limited, current reserves are based on
           | current exploration. More sources will be found and exploited
           | as demand grows.
           | 
           | And if you want an alternative, sodium batteries are already
           | coming online.
        
             | standeven wrote:
             | It's also very recyclable, so big batteries that reach end
             | of life can contribute back to the lithium supply.
        
             | cogman10 wrote:
             | In fact, the limiting element for Li chemistries is
             | generally the Nickel. Pretty much everything else that goes
             | into these chemistries is highly available. Even something
             | like Cobalt which is touted as unavailable is only that way
             | because the industrial uses of cobalt is basically only li
             | batteries. It's mined by hand not because that's the best
             | way to get it, but because that's the cheapest way to get
             | the small amount that's needed for batteries.
             | 
             | Sodium iron phosphate batteries, if Li prices don't
             | continue to fall, will be some of the cheapest batteries
             | out there. If they can be made solid state then you are
             | looking at batteries that will dominate things like grid
             | and home power storage.
        
               | to11mtm wrote:
               | > Even something like Cobalt which is touted as
               | unavailable is only that way because the industrial uses
               | of cobalt is basically only li batteries.
               | 
               | AFAIR Cobalt is also kinda toxic which is a concern.
               | 
               | But as far as that and
               | 
               | > In fact, the limiting element for Li chemistries is
               | generally the Nickel
               | 
               | Isn't that part of why LiFePO was supposed to take off
               | tho? Sure the energy density is a bit lower but
               | theoretically they are cheaper to produce per kWh and
               | don't have any of the toxicity/rarity issues of other
               | lithium designs...
        
               | cogman10 wrote:
               | > Isn't that part of why LiFePO was supposed to take off
               | tho?
               | 
               | It's the exact reason LFPs are taking off, especially in
               | grid storage scenarios.
               | 
               | The high cycle life combined with the fact that all the
               | materials are easy to acquire and dirt cheap.
        
           | Tade0 wrote:
           | There are over 200 billion tonnes of lithium in seawater,
           | it's just the least economical out of all sources of this
           | element.
           | 
           | There are plenty more, but they're explored only when there's
           | a price hike.
        
             | cogman10 wrote:
             | AFAIK, the brine pits are pretty economical, they just
             | require ocean access.
             | 
             | What I'm somewhat surprised about is that we've not seen
             | synergies with desalination and ocean mineral extraction.
             | IDK why the brine from a desalination plant isn't seen as a
             | prime first step in extraction lithium, magnesium, and
             | other precious minerals from ocean water.
        
               | adgjlsfhk1 wrote:
               | likely a matter of location. desal tends to be on the
               | coast and near cities which tends to be pretty valuable
               | land, making giant evaporation ponds a tough sell.
        
               | namibj wrote:
               | You don't use ponds, you run the desalination to as
               | strong as practical and follow up with either
               | electrolysis or distillation of the brine.
               | 
               | But once summer electricity becomes cheap enough due to
               | solar production increasing to handle winter heating
               | loads with the (worse) winter sun, we can afford a lot of
               | electrowinning of "ore" which can be pretty much sea salt
               | or generic rock at that point.
               | 
               | Form Energy is working on grid scale iron air batteries
               | which use the same chemistry as would be used for
               | (excess/spare) solar powered iron ore to iron metal
               | refining.
               | 
               | AFAIK the coal powered traditional iron refining ovens
               | are the largest individual machines humanity operates.
               | (Because if you try to compare to large (ore/oil) ships,
               | it's not very fair to count their passive cargo volume;
               | and if comparing to offshore oil rigs, and including
               | their ancillary appliances and crew berthing, you'd have
               | to include a lot of surrounding infrastructure to the
               | blast furnace itself.)
               | 
               | It will take coal becoming expensive for it's CO2 before
               | we really stop coal fired iron blast furnaces. And before
               | then it's hard to compete even at zero cost electricity
               | when accounting for the duty cycle limitations of only
               | taking curtailed summer peaks.
        
               | gpm wrote:
               | > What I'm somewhat surprised about is that we've not
               | seen synergies with desalination and ocean mineral
               | extraction.
               | 
               | I think these guys are basically using desalination tech
               | to make lithium extraction cheaper:
               | https://energyx.com/lithium/#direct-lithium-extraction
               | 
               | As I understand it (which is far from perfectly) it's
               | still not using ocean water, because you can get so much
               | higher lithium concentration in water from other sources.
               | But it's a more environmentally friendly, and they argue
               | cheaper, way to extract the lithium from water than just
               | using the traditional giant evaporation pools.
        
               | namibj wrote:
               | Do you know how much magnesium you find with silicon and
               | iron as olivine? It's just the silicon that we haven't
               | yet tamed for large scale mechanical usage that makes
               | them uneconomical to electrolyze.
        
           | namibj wrote:
           | We have 10 years of 2021 global energy production (including
           | oil/coal/gas!) of LFP in the oceans; but yes, sodium
           | batteries are probably cheaper.
        
         | scotty79 wrote:
         | Also sodium batteries are coming to the market at a fraction of
         | the cost.
         | 
         | "We're matching the performance of [lithium iron phosphate
         | batteries] at roughly 30% lower total cost of ownership for the
         | system." Mukesh Chatter, cofounder and CEO, Alsym Energy
        
           | lambdaone wrote:
           | I see this as complementary to other energy storage systems,
           | including sodium ion batteries; each will have its own
           | strengths and weaknesses. I expect energy storage density
           | cost will be _the_ critical parameter here, as this looks
           | best suited to do diurnal storage for solar power systems
           | near out-of-town predictable power consumers like data
           | centers.
        
             | 3eb7988a1663 wrote:
             | Maintenance of the system is my biggest question. Lot of
             | mechanical complexity with ensuring your gas containment,
             | compressors, turbines, etc are all up to spec. This also
             | seems like a system where you want to install the biggest
             | capacity containment you can afford at the onset.
             | 
             | All of that vs lithium/sodium where you can incrementally
             | install batteries and let it operate without much concern.
             | Maybe some heaters if they are installed in especially cold
             | climates.
        
               | namibj wrote:
               | Don't even really need notable heaters if you regulate
               | your thermal vents enough.
        
           | dzhiurgis wrote:
           | Sodium batteries will take 15 years to overtake LFPs cost.
           | Stop gargling on hype please.
        
         | Herring wrote:
         | Efficiency isn't that important if the input cost is low
         | enough. Basically the utility is throwing it away (curtailment)
         | so you probably can too. CAPEX is really the most important
         | part of this.
        
         | TrainedMonkey wrote:
         | AFAIK cost here counts only the manufacturing side. While your
         | conclusion that in the long run economies of scale will
         | prevail, the lifetime costs are probably more than 30%. For
         | example I expect recycling costs to be significantly worse for
         | the Li-Ion.
        
           | namibj wrote:
           | Grid scale LFP with once daily cycling lasts 30 years before
           | the cells are degraded enough to think about recycling.
           | 
           | And those are very low maintenance over that time.
           | 
           | You're probably mostly going to swap voltage regulators and
           | their fans, perhaps bypass the occasional bad cell by turning
           | the current to zero, unscrewing the links from the adjacent
           | cells to the bad cell, and screwing in a fresh link with the
           | connect length to bridge across.
        
         | GeekyBear wrote:
         | It's cheaper, doesn't involve the use of scarce resources, and
         | is expected to have an operational lifetime that is three times
         | longer than lithium ion storage facility.
         | 
         | That's a significant difference.
        
           | namibj wrote:
           | 2021 total world energy production of approximately 172 PWh
           | would require 27.5 billion metric tons of lithium metal at
           | typical 0.16g/Wh of a modern LFP cell; meanwhile, we have
           | approximately 230 billion metric tons of lithium for taking
           | (e.g. as part of desalination plants producing many other
           | elements at the same time from the pre-consecrated brine)
           | from the oceans.
           | 
           | Note that we require only a fraction of a year's worth of
           | energy to be stored, I think less than 5% if we accept energy
           | intensive industry in high latitude to take winter breaks, or
           | even more with further tactics like higher overproduction or
           | larger interconnected grid areas.
           | 
           | And that's all without even the sodium batteries that do seem
           | to be viable already.
        
             | cossatot wrote:
             | Do you think desalinating 10% of the world's ocean water is
             | feasible? What are the energy resources necessary to do
             | that?
        
         | dzhiurgis wrote:
         | Batteries aren't really suited for seasonal storage - they
         | decay when fully charged.
         | 
         | And foreseeable future they provide such huge value for grid
         | stability that it wouldn't make sense economically either.
        
       | readthenotes1 wrote:
       | Does pure-ish CO2 have advantages over regular air or the freon-
       | like substance used in air conditioning?
       | 
       | How much energy us used to purify and maintain the CO2?
        
         | cogman10 wrote:
         | It's pretty cheap to acquire a boatload of and, assuming you
         | don't get it directly from burning fossil fuels, there's really
         | no environmental harms of it leaking into the atmosphere. [1]
         | 
         | [1] https://en.wikipedia.org/wiki/Carbon_capture_and_storage
        
           | zahlman wrote:
           | > CCS could have a critical but limited role in reducing
           | greenhouse gas emissions.[6] However, other emission-
           | reduction options such as solar and wind energy,
           | electrification, and public transit are less expensive than
           | CCS and are much more effective at reducing air pollution.
           | Given its cost and limitations, CCS is envisioned to be most
           | useful in specific niches. These niches include heavy
           | industry and plant retrofits.[8]: 21-24
           | 
           | > The cost of CCS varies greatly by CO2 source. If the
           | facility produces a gas mixture with a high concentration of
           | CO2, as is the case for natural gas processing, it can be
           | captured and compressed for USD 15-25/tonne.[66] Power
           | plants, cement plants, and iron and steel plants produce more
           | dilute gas streams, for which the cost of capture and
           | compression is USD 40-120/tonne CO2.[66]
           | 
           | ... And then for this usage, presumably you'd have to
           | separate the CO2 from the rest of the gas.
        
         | analog31 wrote:
         | It's easy to liquefy, so it has a density advantage over air,
         | and would be bad if released but not super bad.
        
           | 3eb7988a1663 wrote:
           | Suffocation seems like the most relevant concern in the event
           | of a catastrophic leak.
        
             | 1123581321 wrote:
             | It is a necessary risk. Oxygen is dangerous when heat is
             | involved, and its low critical point is harder to work with
             | than co2.
        
         | ajb wrote:
         | These days CO2 is actually quite commonly used in air-
         | conditioners as a refrigerant, R-744. Fluorinated gases like
         | Freon are being phased out due to being even worse for global
         | warming.
        
       | lambdaone wrote:
       | This seems almost too good to be true, and the equipment is so
       | simple that it would seem that this is a panacea. Where are the
       | gotchas with this technology?
       | 
       | Clearly power capacity cost (scaling compressors/expanders and
       | related kit) and energy storage cost (scaling gasbags and storage
       | vessels) are decoupled from one another in this design; are there
       | any numbers publicly available for either?
        
         | zahlman wrote:
         | Well, it isn't going to _sink_ enough CO2 to move the needle:
         | 
         | > If the worst happens and the dome is punctured, 2,000 tonnes
         | of CO2 will enter the atmosphere. That's equivalent to the
         | emissions of about 15 round-trip flights between New York and
         | London on a Boeing 777. "It's negligible compared to the
         | emissions of a coal plant," Spadacini says. People will also
         | need to stay back 70 meters or more until the air clears, he
         | says.
         | 
         | So it's really just about enabling solar etc.
        
           | api wrote:
           | It's a battery not a sequestration technology.
        
           | dmd wrote:
           | It has nothing whatsoever to do with sinking CO2.
        
             | zahlman wrote:
             | I understand this, but it coincidentally _uses_ CO2 and it
             | 's _hard for me to understand_ why the technology would
             | sound  "too good to be true" _without_ imagining such a
             | purpose.
        
         | to11mtm wrote:
         | I don't know _numbers_ but I at least remember my paintball
         | physics;
         | 
         | As far as the storage vessel, CO2 has much lower pressure
         | demands than something like, say, hydrogen. On something like a
         | paintball marker the burst disc (i.e. emergency blow off valve)
         | for a CO2 tank is in the range of of 1500-1800PSI [0].
         | 
         | A compressed air tank that has a 62cubic inch, 3000PSI
         | capacity, will have a circumference of 29cm and a length close
         | to 32.7cm, compared to a 20oz CO2 tank that has a circumfrence
         | of 25.5cm and a length of around 26.5cm [1]. The 20oz tank also
         | weighs about as much 'filled' as the Compressed air tank does
         | empty (although compressed air doesn't weigh much, just being
         | through here).
         | 
         | And FWIW, that 62/3000 compressed air vs 20oz CO2 comparison...
         | the 20oz of CO2 will almost certainly give you more 'work' for
         | a full tank. When I was in the sport you needed more like a
         | 68/4500 tank to get the same amount of use between fills.
         | 
         | Due to CO2's lower pressures and overall behavior, it's way
         | cheaper and easier to handle parts of this; I'm willing to bet
         | the blowoff valve setup could in fact even direct back to the
         | 'bag' in this case, since the bag can be designed
         | pessimistically for the pressure of CO2 under the thermal
         | conditions. [2]
         | 
         | I think the biggest 'losses' will be in the energy around re-
         | liquifying the CO2, but if the system is closed loop that's not
         | gonna be that bad IMO. CO2's honestly a relatively easy and as
         | long as working in open area or with a fume hood relatively
         | safe gas to work with, so long as you understand thermal rules
         | around liquid state [also 2] and use proper safety equipment
         | (i.e. BOVs/burst discs/etc.)
         | 
         | [0] - I know there are 3k PSI burst discs out there but I've
         | never seen one that high on a paintball CO2 tank...
         | 
         | [1] - I used the chart on this page as a reference:
         | https://www.hkarmy.com/products/20oz-aluminum-co2-paintball-...
         | 
         | [2] - Liquid CO2 does not like rapid thermal changes or
         | sustained extreme heat; This is when burst discs tend to go
         | off. But it also does not work nearly as well in cold weather,
         | especially below freezing. Where this becomes an issue is when
         | for one reason or another liquid CO2 gets into the system. This
         | can be handled in an industrial scenario with proper design I
         | think tho.
        
           | lambdaone wrote:
           | Fantastic detail, thank you.
        
           | api wrote:
           | So... it's a compressed air battery but with a better working
           | fluid than air.
           | 
           | I remember wondering about using natural gas or propane for
           | this a long time ago. Not burning the gas but using it as a
           | compressed gas battery. It liquifies easier than air, etc.,
           | but would be a big fire risk if there were leaks while this
           | is not.
           | 
           | Seems neat.
        
             | to11mtm wrote:
             | > Not burning the gas but using it as a compressed gas
             | battery. It liquifies easier than air, etc., but would be a
             | big fire risk if there were leaks while this is not.
             | 
             | FWIW Back in the day, Ammonia was used for refrigeration
             | because it had the right properties for that process; I
             | mention that one because while it's not a fire risk it's
             | definitely a health risk, also it's a bit more reactive
             | (i.e. leaks are more likely to happen)
             | 
             | > Seems neat.
             | 
             | Agreed!
        
             | pfdietz wrote:
             | Except you have to trap and recycle the uncompressed CO2,
             | hence that enormous bag to hold all that gas. Color me
             | skeptical.
             | 
             | With compressed air, you just release the air back to the
             | atmosphere.
        
         | scellus wrote:
         | Thermal energy storage is one gotcha. It will eventually leak
         | away, even if the CO2 stays in the container indefinitely, and
         | then you have no energy to extract.
         | 
         | The 75% round-trip efficiency (for shorter time periods) quoted
         | in other threads here is surprisingly high though.
        
       | scotty79 wrote:
       | "First, a compressor pressurizes the gas from 1 bar (100,000
       | pascals) to about 55 bar (5,500,000 pa). Next, a thermal-energy-
       | storage system cools the CO2 to an ambient temperature. Then a
       | condenser reduces it into a liquid that is stored in a few dozen
       | pressure vessels, each about the size of a school bus. The whole
       | process takes about 10 hours, and at the end of it, the battery
       | is considered charged.
       | 
       | To discharge the battery, the process reverses. The liquid CO2 is
       | evaporated and heated. It then enters a gas-expander turbine,
       | which is like a medium-pressure steam turbine. This drives a
       | synchronous generator, which converts mechanical energy into
       | electrical energy for the grid. After that, the gas is exhausted
       | at ambient pressure back into the dome, filling it up to await
       | the next charging phase."
        
         | vaylian wrote:
         | And I suppose the whole thing is a closed system? Which means,
         | none of the CO2 would be released to the outside?
        
       | alexchamberlain wrote:
       | Would this be effective at smaller volumes? Could it get down to
       | say the size of a washing machine for use at home?
        
         | lambdaone wrote:
         | Very unlikely. All the technologies involved work best at
         | scale; for example, the area-to-volume ratio of the liquid gas
         | storage vessel is a critical parameter to keep energy losses
         | low.
        
       | standardUser wrote:
       | I've been waiting for large-scale molten salt/rock batteries to
       | take off. They've existed at utility scale for years but are
       | still niche. They're not especially responsive and I imagine a
       | facility to handle a mass amount of molten salt is not the
       | easiest/cheapest thing to build.
       | 
       | This sounds better in every way.
        
       | creativeSlumber wrote:
       | what happens if that large enclosure fails and the CO2 freely
       | flows outside?
       | 
       | That enclosure has a huge volume - area the size of several
       | football fields, and at least 15 stories high. The article says
       | it holds 2k tons of co2, which is ~1,000,000 cubic meters in
       | volume.
       | 
       | CO2 is denser than air will pool closer to the ground, and will
       | suffocate anyone in the area.
       | 
       | See https://en.wikipedia.org/wiki/Lake_Nyos_disaster
       | 
       | Edit: It holds 2k tons, not 20K tons.
        
         | tonfa wrote:
         | > People will also need to stay back 70 meters or more until
         | the air clears, he says.
        
           | SoftTalker wrote:
           | Good luck running 70m in a CO2 dense atmosphere. And CO2 hugs
           | the ground it does not float away. It will persist in low
           | areas for quite a while.
           | 
           | Anyone in the local vicinity would need to carry emergency
           | oxygen at all times to be able to get to a safe distance in
           | case of rupture. Otherwise it's a death sentence, and not a
           | particularly pleasant one as CO2 is the signal that triggers
           | the feeling of suffocation.
        
             | cycomanic wrote:
             | It's unlikely that the thing will burst and disperse all
             | CO2 immediately. It's just slightly higher pressure than
             | the outside (that's the whole principle). So you have a
             | slow leak of CO2 to the outside. You don't have to run that
             | fast (or run at all).
             | 
             | The way I understood the quote, the safety distance is when
             | they have to do an emergency deflate (e.g. due to wind).
             | The way they calculate the 70 m is probably based on the
             | volume and how large of a area you cover until the height
             | is low enough that you can still breath.
             | 
             | Generally, because it's leaking to the outside, where there
             | is going to be wind it will not stick around for long time
             | I suspect.
        
         | Hnrobert42 wrote:
         | The last section of TFA is called "What happens if the dome is
         | punctured?". The answer: a release of CO2 equal to about 15
         | transatlantic flights. People have to stand back 70m until it
         | clears.
         | 
         | It would not be good, but it wouldn't be Bhopal. And there are
         | still plenty of factories making pesticides.
        
           | creativeSlumber wrote:
           | Comparing it to X flights maybe correct from a greenhouse
           | emissions standpoint, but extremely misleading from a safety
           | perspective. A jet emits that co2 spread over tens of
           | thousands of miles. The problem here is it all pooled in one
           | location.
           | 
           | Also that statement of 70 meters seem very off, looking at
           | the size of the building. What leads to suffocation is the
           | inability to remove co2 from your body rather than lack of
           | oxygen, and thus can be life threatening even at 4%
           | concentration. It should impact a much much larger area.
        
             | epgui wrote:
             | It's a gas in an open space, it diffuses _very_ quickly.
        
               | ben_w wrote:
               | https://en.wikipedia.org/wiki/Limnic_eruption
               | 
               | I don't know the safety limits for this quantity, I hope
               | the "70 meters" claim was by someone who modelled it
               | carefully rather than a gut check.
        
               | apparent wrote:
               | Seems like it would depend if there was a small tear or a
               | massive breach.
        
               | to11mtm wrote:
               | Yep. When I had to fill CO2 tanks at a paintball shop yes
               | there were times that I had to open a door (I mean we
               | were talking a lot of fills in short time, btw fills had
               | to start with draining the tank's existing volume so I
               | could zero out the scale) but even indoors a door+fan was
               | enough to keep even the nastiest of sale days OSHA
               | compliant.
               | 
               | Also a 'puncture' is very different from the gasbag
               | mysteriously vanishing from existence; My only other
               | thought is that in cold regions (I saw wisconsin
               | mentioned in the article) CO2 does not diffuse quite as
               | fast and sometimes visibly so...
        
           | Animats wrote:
           | > People have to stand back 70m until it clears.
           | 
           | How did they calculate that evacuation distance? CO2 is
           | heavy. That little house about 15m from the bubble needs to
           | be acquired.
           | 
           | The topography matters. If the installation is in a valley, a
           | dome rip could make air unbreathable, because the CO2 will
           | settle at the bottom. People have been killed by CO2 fire
           | extinguishing systems. It takes a reasonably high
           | concentration, a few percent, but that can happen. They need
           | alarms and handy oxygen masks.
           | 
           | Installations like this probably will be in valleys, because
           | they will be attached to wind farms. The wind turbines go in
           | the high spots and the energy storage goes in the low spots.
        
         | jaggederest wrote:
         | CO2 is in general less dangerous than inert gases, because we
         | have a hypercapnic response - it's a very reliable way to
         | induce people to leave the area, quite uncomfortable, and is
         | actually one of the ways used to induce a panic attack in
         | experimental settings.
         | 
         | If it were, say, argon, it would be much more likely to
         | suffocate people, because you don't notice hypoxia the way you
         | do hypercapnia. It can pool in basements and kill everyone who
         | enters.
         | 
         | That being said it is an enormous volume of CO2, so the
         | hypercapnic response in this case may not be sufficient if
         | there's nowhere to flee to, as sadly happened in the Lake Nyos
         | disaster you cited.
        
         | quotemstr wrote:
         | I wonder whether it'd be possible to augment the CO2 with
         | something that would make it more detectable visually and
         | aromatically, like we do natural gas.
         | 
         | Natural gas is naturally odorless and colorless. Therefore, by
         | default, it can accumulate to dangerous levels without anyone
         | noticing until too late. We make natural gas safer by making
         | stink, and we make it stink by adding trace amounts of
         | "odorizers" like thiophane to it.
         | 
         | I wonder whether we could do something similar for CO2 working
         | fluid this facility uses --- make it visible and/or "smell-
         | able" so that if a leak does happen, it's easier to react
         | immediately and before the threshold of suffocation is reached.
         | Odorizers are also dirt cheap. Natural gas industry goes
         | through tons of the stuff.
        
           | amelius wrote:
           | I suppose the people working at the plant will be wearing
           | detectors and/or these will be placed at strategic locations
           | in the area.
        
         | microtherion wrote:
         | Yeah, I was also immediately thinking about the Lake Nyos
         | disaster. But that one released something like 200k tons of CO2
         | in an instant, whereas this facility has 2k tons, which would
         | more likely be released more gradually.
        
       | buckle8017 wrote:
       | So it's a compressed air facility but it's using dry CO2 because
       | it makes the process easier and CO2 is cheap.
       | 
       | Not a carbon sequestration thing, but will likely fool some
       | people into thinking it is.
       | 
       | So the question is, how much does it cost? The article is
       | completely silent on this, as expected.
        
         | to11mtm wrote:
         | > So the question is, how much does it cost? The article is
         | completely silent on this, as expected.
         | 
         | Honestly considering the design overall, I feel like one could
         | make a single use science project version of this on a desk
         | (i.e. aside from the CO2 recharging part) for under 200 bucks.
         | 12oz CO2 tank, some sort of generator and whatever you need to
         | spin it that is sealed, tubing, and a reclamation bag for the
         | used CO2.
         | 
         | And IMO using CO2 makes the rest of the design cheaper; Blow
         | off valves are relatively cheap for this scenario, especially
         | because CO2 gas system pressures are fairly low, and there's
         | plenty of existing infrastructure around the safety margin. And
         | I think even with blow off valves this could be a 'closed'
         | system with minimal losses (although that would admittedly add
         | to the cost...)
         | 
         | I guess I'm saying is the main unknown is how expensive this
         | regeneration system is for the quoted efficiency gains.
        
         | thescriptkiddie wrote:
         | The tanks to hold liquid CO2 will likely be a lot cheaper than
         | compressed air tanks because the required pressure is much
         | lower. But they are going to loose a _lot_ of energy to cooling
         | the gas and reheating the liquid. I would be surprised if the
         | round-trip efficiency is higher than 25%.
        
           | alwa wrote:
           | They claim 75% efficiency AC-AC [0], and they point out that
           | there's no degradation with time. What estimates are you
           | using to arrive at the 25% figure?
           | 
           | [0] https://energydome.com/co2-battery/
        
           | upofadown wrote:
           | The energy used to liquefy the CO2 is the bulk of the energy
           | stored. They don't throw it away afterwards. The the liquid-
           | gas transition is why this works so much better than
           | compressed air.
        
         | riffraff wrote:
         | [delayed]
        
       | laurencerowe wrote:
       | > Energy Dome expects its LDES solution to be 30 percent cheaper
       | than lithium-ion.
       | 
       | Can see how this could scale up for longer storage fairly cheaply
       | but on current trends batteries will have caught up in cost in
       | 2-3 years.
        
         | Smoosh wrote:
         | Aren't CATL already producing sodium-ion batteries for about
         | 60% the cost of lithium-ion for equivalent capacity?
        
           | laurencerowe wrote:
           | Yeah. Maybe this tech will have a place for week-long storage
           | and be a good buffer for wind power but I hard to see the
           | economics working for daily cycling.
        
       | nanomonkey wrote:
       | I'm curious if this method could be used along with super
       | critical CO2 turbine generators. In other words after extracting
       | the energy stored in compressed CO2, if you could then run it
       | through a heat exchanger to bring it up to super critical temps
       | and pressure and then utilize it as the working fluid in a
       | turbine.
        
       | pfdietz wrote:
       | We don't need another few-hours storage technology. Batteries are
       | going to clobber that. What we need is a storage technology with
       | a duration of months. That would be truly complementary to these
       | short term storage technologies.
        
         | newyankee wrote:
         | Had heard a lot about flow batteries few years back. I am
         | guessing they are slowly taking off as well, the trial and
         | error that explains their feasibility , need and ability to pay
         | for themselves in a market like ERCOT is the key.
         | 
         | This is one place where I think by 2030 a clear no of options
         | will be established.
        
         | 2thumbsup wrote:
         | A few hours are sometimes enough to start generators when
         | renewable energy supply decreases. Obviously, the more capacity
         | the better, but costs will increase linearly with capacity in
         | most cases.
         | 
         | Pumped-storage hydroelectricity - where it is feasible - is the
         | only kind of energy storage close to "months".
        
           | pfdietz wrote:
           | The point is that's already a well-served market. These
           | competitors are like alternative semiconductors going up
           | against silicon.
        
           | ifwinterco wrote:
           | You can store energy for months pretty easily as chemical
           | energy. Just get some hydrogen, then join it to something
           | else, maybe carbon, in the right proportion so it's a liquid
           | at room temperature making it nice and easy to both store and
           | transport.
           | 
           | Wait a minute...
        
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