> The tried-and-true grid-scale storage option—pumped hydro [--> https://spectrum.ieee.org/a-big-hydro-project-in-big-sky-cou... ], in which water is pumped between reservoirs at different elevations—lasts for decades and can store thousands of megawatts for days.
It looks like the article text is using the wrong unit for energy capacity in these contexts. I think it should be megawatt-hours, not megawatts. If this is true, this is a big yikes for something coming out of the Institute of Electrical and Electronics Engineers.
> big yikes for something coming out of the Institute of Electrical and Electronics Engineers.
Besides the unit flub, there's an unpleasant smell of sales flyer to the whole piece. Hard data spread all over, but couldn't find efficiency figures. Casual smears such as "even the best new grid-scale storage systems on the market—mainly lithium-ion batteries—provide only about 4 to 8 hours of storage" (huh, what, why?). I could also have used an explanation of why CO2, instead of nitrogen.
> provide only about 4 to 8 hours of storage" (huh, what, why?)
Because the most efficient way to make money with a lithium ion battery (or rather the marginal opportunity after the higher return ones like putting it in a car are taken) is to charge it in the few hours of when electricity is cheapest and discharge it when it is most expensive, every single day, and those windows generally aren't more than 8 hours long...
Once the early opportunities are taken lower value ones will be where you store more energy and charge and discharge at a lower margin or less frequently will be, but we aren't there yet.
Advertising that your new technology doesn't do this is taking a drawback (it requires a huge amount of scale in one place to be cost competitive) and pretending it's an advantage. The actual advantage, if there is one, is just that at sufficient scale it's cheaper (a claim I'm not willing to argue either way).
Power plants are often described in terms of (max) power output, i.e., contribution to the grid. So, I can see how it might confuse a writer to then also talk about storage inadvertently.
But also, the second paragraph already describes the 100 MWh vs MW nuance.
It is not a nuance in an article that focuses on storage from the supposed premier professional association. As an engineer I would expect typical energy content (median/average) of the top 10 hydro pump projects and also some discussion about the availability of suitable sites. I think one should strive for at least high school level physics. There is no need to push out texts that can be easily surpassed by any current llm.
If 1 watt is 1 joule per second then, honestly, what are we doing with watt-hours?
Why can’t battery capacity be described in joules? And then charge and discharge being a function of voltage and current, could be represented in joules per unit time. Instead its watt-hours for capacity, watts for flow rate.
Watt-hours… that’s joules / seconds * hours? This is cursed.
I believe it's just a matter of intuitively useful units. There's simply too many seconds in a day for people to have an immediate grasp on the quantity. If you're using a space heater or thinking about how much power your fridge uses kilowatt hours is an easy unit to intuit. If you know you have a battery backup with 5 kilowatt hours of capacity and your fridge averages 500 watts then you've got 10 hours. If you convert it all to watt seconds the mental math is harder. And realistically in day to day life most of what we're measuring for sake of our power bill, etc. is stuff that's operating on a timetable of hours or days.
It is not more cursed than km/h (1 m/s = 3600 m/h = 3.6 km/h)
Both those units are more convenient than their SI equivalent and their "cursedness" come from the hour/minute/second time division.
If we had decimal time, as it was initially proposed with the metric system, we wouldn't have this problem, but we weren't ready to let go of hours/minute/second.
A watt of power multiplied by a second of time has an agreed upon name called joule, but a watt second is also a perfectly valid SI name.
A watt is a joule of energy divided by a second of time, this is a rate, joule per second is also a valid name similar to nautical mile per hour and knot being the same unit.
Multiplication vs division, quantity vs rate, see the relationship? Units may have different names but are equivalent, both the proper name and compound name are acceptable.
A watt hour is 3600 joules, it’s more convenient to use and matches more closely with how electrical energy is typically consumed. Kilowatt hour is again more directly relatable than 3.6 megajoules.
Newton meter and Coulomb volt are other names for the joule. In pure base units it is a kilogram-meter squared per second squared.
Of course it can be. Nobody does it in practice because it's inconvenient.
Watts = volts * amps and the people working with batteries are already thinking in terms of voltage and amperage. It'd be painful to introduce a totally new unit and remember 1 watt for an hour is 3.6kj instead of... 1 watt-hour.
Not every area is as messed up as the Colorado river watershed...
All users (states) were given an allotment which, when it was set, was more than what would ever be the yearly supply.
From the outset it was essentially a free for all. Everyone was happy, they kinda got what they asked. It's just that they were all living in a paper reality
I should have explained in my original comment why I think those sentences are wrong. I'll do so now.
> pumped hydro [...] can store thousands of megawatts for days.
You can't "store" a megawatt – because you can only store energy, not power.
But another interpretation is, if you actually store thousands of megawatts (i.e. gigawatts) for days, then at the very least, 1 GW × 1 day = 24 GW⋅h. If we take "a few" to mean 3, then 3 GW × 3 day = 216 GW⋅h. I'm not sure there exists a large enough pumped hydro plant in the world that stores 216 GW⋅h of energy. So I think the article meant to say, "store a few gigawatt-hours to be released over a period of a few days".
> Media reports show renderings of domes but give widely varying storage capacities—including 100 MW and 1,000 MW.
Once again, you can't store megawatts of power, full stop. You can store megawatt-hours of energy. The linked article at Bloomberg said that a project in China is building 600 MW of wind power, 400 MW of solar power, and 1 GW⋅h of energy storage – which is the correct unit.
The round-trip efficiency comparison (60-75% vs lithium-ion's ~90%) is interesting but somewhat misleading without context. For grid-scale storage, the relevant question isn't efficiency in isolation - it's lifecycle economics including capex, degradation, and replacement cycles.
Lithium-ion has superior efficiency but degrades significantly after 5,000-7,000 cycles, typically reaching 80% capacity in 7-10 years. If CO2 batteries can maintain performance for 20+ years with minimal degradation (which the article suggests), the lower efficiency becomes less relevant. You're trading 15-25% energy loss for potentially 2-3x longer operational life and no lithium supply chain dependencies.
The real breakthrough is duration-flexible storage. Lithium-ion economics break down beyond 4-hour discharge rates because you're paying for both energy capacity and power capacity. CO2 systems decouple these - the turbine size determines power output, the storage tank size determines duration. That makes them ideal for seasonal storage patterns where you might charge for days during high renewable production and discharge slowly over weeks during winter lulls.
What's missing from the article: what's the round-trip efficiency at different discharge rates? Does efficiency drop significantly when discharging over 12 hours vs 4 hours? That would determine whether these make sense for daily solar smoothing vs weekly wind intermittency vs seasonal storage.
I think it is generally polite to flag when you are using an LLM to write your comment, some people tire of reading the same style of writing over and over - even if the content of your comment is interesting!
Oh good point; I wouldn't have noticed if you didn't point it out. The last ~5 comments from yoan9224 are all in 4-paragraph format. A few comments before that are in 3-paragraph format. They all look suspiciously uniform in writing style, and very mechanical.
The system actually sort of uses the atmosphere as an ambient heat sink (when compressing) or heat source (when expanding).
I wonder if that heat could be stored in a more sensible way, e.g. as heated water in a tank near the bubble. This could improve the efficiency figures at short repeating patterns (charding at high noon, discharging through the night).
As far as I understand they do try to keep the heat around for the next decompression. As of course they need it.
But I could not find what type of heat storage they use.
Ultimately they "only" seem to need to store it for 12h, right?
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.
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.
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.
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.
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.
> For example I expect recycling costs to be significantly worse for the Li-Ion.
I think there's a good argument for the opposite.
Recycling costs for Li-Ion once we are doing it at scale should be significantly negative. There are valuable materials you get to extract, they aren't in that complex a blend to extract them from, and there's a lot of basically the same blend. The biggest risk in this claim is, I think, the implicit claim that we won't figure out how to extract the same materials from the earth much cheaper in the meantime cratering the end of life value of batteries - but in that event the CO2 battery technology is underwater anyways and the chemical batteries win on not wasting R&D costs.
By contrast while there's some value in the steel that goes into building tanks and pumps and so on, the material cost if a much lower fraction of the cost of the device. Most of the cost went into shaping it into those complex shapes. I don't know for sure what the cost breakdown of the CO2 plant looks like but if a lot of the cost is something else it's probably something like concrete or white paint that actually costs money to dispose of.
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.
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%....
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
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.
I wonder how much Google is factoring in the implicit cooling cycle? Because any pressurized gas energy storage is either including some advanced heat storage or is just venting the heat created during compression (the ancient Huntorf facility in Germany is infamous for that, super wasteful)
Usually you want to keep the heat and put it back into the compression medium during decompression and hope that losses from the heat storage aren't too big, but when you have a cooling use case nearby, you can use that low intensity heat to compensate heat storage losses, or even overcompensate. When you consider how much of the power input of a datacenter is typically used for cooling, compressed gas storage could be useful even if there was zero electric recovery (just time-shifting the power consumption for cooling to a time with better energy availability)
I'm sort of thinking out loud here but could you have two batteries running simultaneously but on opposite cycles, so while one is cooling the other is heating? Obviously it wouldn't be 100% efficient but it might reduce some wasted energy.
The heat and cold are created by the compressing or decompressing the CO2 (our any other gas). If one battery is heating while the other needs heat that would imply that one is charging while the other discharges, which is rarely useful in normal operation
If Google is colocating these with data centers, even low-grade heat that would otherwise be a loss could still be useful, or at least reduce how much active cooling the DC needs
Isn't this effectively neutral over time? Heat generated during compression, lost during decompression, so basically using the air as a heat storage medium?
I think what he's saying is you can boost efficiency if you compress a cooler gas. So if you could capture the "cold" that you get from discharging the device, and use it to pre-cool the air for the next cycle (or use it for the data centers cooling system) , it would be much more efficient.
Yes. A large radiator would handle both. I assume they just store the heat because hot water will be a lot more efficient at reheating the co2 than night time air and a pool with an insulated cover is not hard to construct.
>The company uses pure, purpose-made CO2 instead of sourcing it from emissions or the air, because those sources come with impurities and moisture that degrade the steel in the machinery.
So no environmental advantages. It's supposedly 30% cheaper than lithium-ion, but BYD cars have sodium-based based batteries on the road right now which CATL says will end up being 10-20$/kwh (10x cheaper than current batteries).
So what's the actual advantage of this ? I think it's just lucky to land just at the right time where batteries aren't cheaper enough yet.
> 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
Lambdaone is differentiating between the costs to store energy (measured in kWh or Joules) and the costs to store energy per time (which is power, measured in Watts). If you want to store the whole excess energy that solar panels and wind turbines generate on a sunny, windy day, you need to have a lot of power storage capability (gigawatts of power generated during peak power generation). This can be profitable even if you only have a low energy storage capability, e.g. if you can only store a day worth of excess solar/wind energy, because you can sell this energy in the short term, for example in the next night, when the data centers are still running, but solar panels don't produce power. This is what batteries give you -- high power storage capabilities but low energy storage capacities.
Of course, you can always buy more batteries to increase the energy storage capacities, but they are very expensive per energy (kWh) stored. In contrast, these CO2 "batteries" are very cheap per energy (kWh) stored -- "just" build more high pressure tanks -- but expensive per power (Watts) stored, because to store more power, you need to build more expensive compressors, coolers etc. This ability to scale out the energy storage capability independently of the power storage capability is what Lambdaone was referring to with the decoupling.
For what is this useful? For shifting energy over a larger amount of time. Because energy storage costs of batteries are so high, they are a bad fit for storing excess energy in the summer (lots of solar) and releasing it in the winter (lots of heating). I'm not sure if these "CO2" batteries are good for such long time frames (maybe pressure loss is too high), but the claim most certainly is that they can shift energy over a longer time frame than is possible with batteries in an economically profitable fashion.
Pumped hydro is just not a valid comparison. I wish people would understand that already… it’s only good for long term storage in certain key geographical regions. Its use case is very limited.
You don’t want to used pumped hydro for short term storage because the rapid cycling will drive up the maintenance costs. You actually hear about hydro power plants talking about installing batteries to reduce wear.
In these discussions please keep in mind that frequency regulation, short term and long term shortage are different applications with different needs. The costs for pumped hydro are generally reported with their target application in mind. It’s not as applicable to dedicated short term storage and certainly not applicable to frequency regulation.
I would posit that they hope Wright's Law will take hold; the components can be optimised and the deployment standardised. Also it looks as if most of the stuff can be made within the US or EU, dodging tariffs.
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?
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...
[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.
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.
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.
The gotcha will be the “poor” round trip efficiency, in comparison to other storage technologies.
It’d be interesting to see if there’s any loss of efficiency with increasing storage duration too (relating to boil-off of the cryogenic side of the storage ?) because this would impact the economics of charging too.
I just get the feeling lithium/sodium ion for electricity and big piles of sand/dirt for heat are going to more-or-less win the energy storage race.
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.
If you think this is simple, wait until you learn about oceans and forests do!
Trees are literally CO2 based solar batteries: they take CO2 + solar energy and store it as hydrocarbons and carbohydrates for later use. Every time you're sitting by a campfire you're feeling heat from solar energy. How much better does it get that free energy storage combined with CO2 scrubbing from the atmosphere!
When you look at the ocean, it's able to absorb 20-30% of all human caused CO2 emissions all with no effort on our behalf.
Unfortunately, these two solution are, apparently, "too good to be true" because we're increasingly reducing the ability of both to remove carbon. Parts of the Amazon are not net emitters of CO2 [0] and the ocean has limits to how much CO2 it can absorb before it starts reach its limit and become dangerously too acidic for ocean life.
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.
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.
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.
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.
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.
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.
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.
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.
I have two solar panels that can generate around 960w/hr. Both panels cost around $400 ($200x2). Cheap.
Storing that energy is quite expensive. an Anker Solix 3800, which is around 3.8kwh, costs $2400 USD. To store 10kwh would cost $7200 USD (which gets us more than 10kwh).
If that cost asymmetry can come down then it becomes feasible to use solar power to provide cheap/local electricity in poor countries at a house scale.
The YouTuber Will Prowse has an excellent site where he tracks his most recommended batteries (and other equipment like inverters) at any time. The prices are always changing, and there are new products all the time so check on the his list any time you are looking to buy:
Like the other commenter said, batteries are a lot cheaper if you are willing to shop around. His top recommended budget battery today is a 4x your Anker Solix's capacity, and around 1/4th the price. You can find many 5kWh server rack batteries for under $1000 now.
Here's a quote I got for a solar install in the Philippines this week:
51.2v 314ah cells (15kwh battery)
16x 580-590w solar panel
Installed for 310k PHP = $5,275
I've also specced out 15-16kwh batteries using the Yxiang design for around the price of your Solix. The problem in the US is regulatory and a particularly predatory tradesman market at the moment.
Is that "regulatory" the problem or is it the solution? We'll know more 20 years from now, looking back at fire incident statistics.
(yes, I'm leaving it open if regulation makes a difference or not - for all we know it could even make a negative difference, helping companies that are better at regulation than at safety. But if I had to bet, I know where my money would be)
Are you saying you bought an electric car with functional 84kwh pack for less than 3 grand? If so I think the outlier is you. That is a better deal than I have seen.
I was really excited about them and was disappointed to see the project fail.
It seems using pure CO2 and scaling up to a massive size are significant boosts to this type of technology (in addition to the heat mitigation along the way).
"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."
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.
We need anything that scales quickly, safely, and cheap. Just getting us through the duck curve would be a tremendous win for energy.
https://en.wikipedia.org/wiki/Duck_curve
We need every approach that's viable. Batteries are part of the solution, and will be in future. But I don't see why we we should assume they're better in every way than this approach
A principle in engineering is that for any market niche, only a few, or even one, technology persists. The others are driven to extinction as they can't compete. It's the equivalent of ecology's "one niche, one species" principle.
There are far more technologies going for the hours scale storage market than will survive. Sure, explore them. But expect most to fail to compete.
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".
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.
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.
Hell, even week will do a lot, you can start importing energy from areas that have currently better renewables conditions over night, even preemptively for a period of bad weather
I don't understand. Why is a duration of months preferable? What is the benefit above storing energy beyond say peak-to-peak? I suppose you can flatten out seasonal variation, but that's not nearly as big of a problem.
This site finds optimal combinations of solar, wind, batteries, and a long term storage (in this case, hydrogen), using historical weather data, to provide "synthetic baseload". It's a simplified model, but it provides important insights.
Go there, and (for various locations) try it with and without the hydrogen. You'll find that in a place at highish lattitude, like (say) Germany, omitting hydrogen doubles the cost. That's because to either smooth over seasonal variation in solar, or over long period drop out of wind, you need to either greatly overprovision those, or greatly overprovision batteries. Just a little hydrogen reduces the needed overprovisioning of those other things, even with hydrogen's lousy round trip efficiency.
Batteries are still extremely important here, for short duration smoothing. Most stored energy is still going through batteries, so their capex and efficiency is important.
You can also tweak the model to allow a little natural gas, limiting it to some fixed percentage (say, 5%) of total electrical output. This also gets around the problem. But we utimately want to totally get off of natural gas.
I suspect thermal storage will beat out hydrogen, if Standard Thermal's "hot dirt" approach pans out.
We desperately need mass energy storage. Everyone gets excited about renewable generation, but it is counterproductive without investing 5x-10x what we spend on generation in improved transmission and storage. It would be better to build 1/10th the amount of solar we do and pair it with appropriate energy storage than it is to just build solar panels. This is a crisis that almost nobody seems to talk about but is blindingly obvious when you look at socal energy price maps. The physics simply doesn't work without storage!!
> 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.
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%.
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?
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.
As always, diversity in the energy ecosystem is a huge plus. Time and time again we see that 'one size fits all' is simply not true so I'm a fan of alternative approaches that use completely different principles. This enables the energy ecosystem to keep exploring the space of possibilities efficiently. I hope this continues to be developed.
> Time and time again we see that 'one size fits all' is simply not true
Do we though? It feels like we're still in the stage where we're just trying to figure out what the best solution is for grid-scale storage, but once we do figure it out, the most efficient solution will win out over all the others. Yes, there may be some regional variation (e.g. TFA mentions how pumped hydro is great but only makes sense where geography supports it), but overall it feels like the world will eventually narrow things down to a very small number of solutions.
The point I was making isn't that we are or aren't actually narrowing down our options, it is that diversity of options is important. We have artificially limited diversity in our energy ecosystem and the rapid adoption of solar/wind/etc shows that. We could have been here decades ago if we actually encouraged diversity and exploration of alternate energy instead of actively discouraging it. Now that it is impossible to hold wind/solar back they are dominating. We should learn from that and encourage exploring diverse options in storage. Luckily I don't think storage has nearly the pushback that generation has had so I think it will be easier for many options to enter and find their niche.
I seem to recall from an article I read about this technology a few years ago that it's efficient partly because when the gas is compressed, they are able to store the heat that is produced, and then later use the stored heat for expanding the gas.
That seems important. I wish we knew how. I found an article that did mention the heat was "stored", with no further detail. The animation down on this page suggests it's stored in water somehow: https://energydome.com/co2-battery/
I don’t know much about chemistry, but is there a reason why they are using CO2 as the gas medium instead of something else? I was thinking ambient air would be readily available, and you don’t have to worry about suffocating people if it ruptures. Is CO2 particularly efficient to compress?
The fluid in high pressure storage is a liquid, making the storage much cheaper. Liquid N2 (most of air) would require over 40 times more pressure or cold temperatures. Purifying out CO2 or any gas is generally a negligible cost.
I’m new to the idea of grid‑scale energy storage technologies, but this was a really clear and interesting introduction to how CO₂ batteries could help with long‑duration renewable energy storage. It’s exciting to see new approaches that might make solar and wind power more reliable and affordable. Thanks for sharing!
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.
Correct, going from cold compressed liquid co2 though. For supercritical CO2 one would then heat up the gas and use it as a working fluid to turn the turbines further.
If you could reuse the same turbine, one could store excess solar/wind energy in the compressed gas form, and then fire up a natural gas or biomass gasification reactor and then feed the heat into the system to produce more electricity on demand.
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.
I wonder how does it compare to hoisting a concrete (or something heavy) block up a pulley system as an energy store? When you need the energy you let it slide down pulling some steel cable that turns a generator, or multiple cables into multiple generators. Or even a cascade of concrete blocks at different heights as a space saver.
Good point. I was thinking more about areas without much water and a large field of poles each hoisting several blocks. Sort of wind turbines but without the blades.
...and even dangling heavy objects in the air and dropping them. (The creativity devoted to LDES is impressive.) But geologic constraints, economic viability, efficiency, and scalability have hindered the commercialization of these strategies.
I have one concern: what if the container bursts? CO2 is heavier than air, and a sudden pressure decrease will cool it down further, so it'll hug the ground. What would be a safe distance for the people around the plant to live without the risk of being asphixiated in an accident?
The article mentions
> 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.
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.
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]
> 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.
It might function as a kind of cogeneration-style buffer, but CO₂ still gets emitted in manufacturing and maintenance — and I’m not sure the volumetric efficiency is all that compelling.
Still, if we ever end up with rows of these giant “balloons,” the landscape might look unexpectedly futuristic.
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.
Sure, some people have proposed that, but if you calculate how much has to be lifted to get 20 MW stored (or so), it gets pretty ridiculous pretty quickly. Like "Lift the largest aircraft carrier 20 meters" silly. You have some pretty severe size/mass issues.
It makes more sense to use water + a dam, but then again, we like to use water for things besides energy storage, and we're talking about a _lot_ of water.
This gas bag is effectively the same as water+dam, except the pressure is from the tanks and the compressor creates it, vs pumping uphill to create pressure.
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.
Been hearing about this project for years, nice to see that it's gaining traction! Only question is that if they use captured Co2 initially or if they have to produce it.
Peacetime technology from people who ignore the shooting war next door. Do you really want to build your energy system on huge soft targets? This looks much more vulnerable than solar arrays or battery installations to small-to-medium warheads (i.e anything from $500 FPV drones with an RPG round to $100k middle strike drones with 100 kg of payload).
It could be made much less vulnerable by dividing the gas storage balloon structures into a set of multiple smaller structures, ideally with some further internal partitioning so a single punctured surface does not release all the gas in that structure. Everything else is as 'hard' or 'soft' as any other piece of industrial plant, and can be hardened further by putting it inside a reinforced building or set of buildings, internal redundancy etc.
Customers will evaluate the risks. Thermal power plants are an easy target too, and oil and gas pipelines. And the oil tankers, according to the news of the last weeks. By the way, nobody cares about oil spills anymore. I guess all those ships were sailing empty /s
> The problem is that even the best new grid-scale storage systems on the market—mainly lithium-ion batteries—provide only about 4 to 8 hours of storage.
This isn't the first time I've seen this sort of claim this week about batteries.
If you're a journalist writing these words, stop doing that, and consider your life choices. Ask your boss for tuition assistance to put you through a 7th grade summer-school science class on matter and energy.
If you're a journalist writing these words in an ostensibly technical engineering journal? Christ. I don't even know where to begin.
> And in 2026, replicas of this plant will start popping up across the globe.
> We mean that literally. It takes just half a day to inflate the bubble. The rest of the facility takes less than two years to build and can be done just about anywhere there’s 5 hectares of flat land.
Gotta love the authors comitment to the bit. Wow, only half a day you say? And then just between 1 to 2 years more? Crazy.
> The tried-and-true grid-scale storage option—pumped hydro [--> https://spectrum.ieee.org/a-big-hydro-project-in-big-sky-cou... ], in which water is pumped between reservoirs at different elevations—lasts for decades and can store thousands of megawatts for days.
> Media reports show renderings of domes but give widely varying storage capacities [--> https://www.bloominglobal.com/media/detail/worlds-largest-co... ]—including 100 MW and 1,000 MW.
It looks like the article text is using the wrong unit for energy capacity in these contexts. I think it should be megawatt-hours, not megawatts. If this is true, this is a big yikes for something coming out of the Institute of Electrical and Electronics Engineers.
> big yikes for something coming out of the Institute of Electrical and Electronics Engineers.
Besides the unit flub, there's an unpleasant smell of sales flyer to the whole piece. Hard data spread all over, but couldn't find efficiency figures. Casual smears such as "even the best new grid-scale storage systems on the market—mainly lithium-ion batteries—provide only about 4 to 8 hours of storage" (huh, what, why?). I could also have used an explanation of why CO2, instead of nitrogen.
> provide only about 4 to 8 hours of storage" (huh, what, why?)
Because the most efficient way to make money with a lithium ion battery (or rather the marginal opportunity after the higher return ones like putting it in a car are taken) is to charge it in the few hours of when electricity is cheapest and discharge it when it is most expensive, every single day, and those windows generally aren't more than 8 hours long...
Once the early opportunities are taken lower value ones will be where you store more energy and charge and discharge at a lower margin or less frequently will be, but we aren't there yet.
Advertising that your new technology doesn't do this is taking a drawback (it requires a huge amount of scale in one place to be cost competitive) and pretending it's an advantage. The actual advantage, if there is one, is just that at sufficient scale it's cheaper (a claim I'm not willing to argue either way).
7 replies →
i think it had something to do with CO2 can be made into supercritical state relatively easily, not for nitrogen or other common gases.
2 replies →
I'm sat here thinking: why not compressed or liquefied air?
1 reply →
> only about 4 to 8 hours of storage" (huh, what, why?)
Or it's just so obvious - to them! that it doesn't need to be mentioned, which then doesn't make it an ad.
Lithium ion battery systems are expensive as shit, and not that big for how much they cost.
Because CO2 is a magic word. It can open free money doors. Or at least it used to.
Power plants are often described in terms of (max) power output, i.e., contribution to the grid. So, I can see how it might confuse a writer to then also talk about storage inadvertently.
But also, the second paragraph already describes the 100 MWh vs MW nuance.
It is not a nuance in an article that focuses on storage from the supposed premier professional association. As an engineer I would expect typical energy content (median/average) of the top 10 hydro pump projects and also some discussion about the availability of suitable sites. I think one should strive for at least high school level physics. There is no need to push out texts that can be easily surpassed by any current llm.
If 1 watt is 1 joule per second then, honestly, what are we doing with watt-hours?
Why can’t battery capacity be described in joules? And then charge and discharge being a function of voltage and current, could be represented in joules per unit time. Instead its watt-hours for capacity, watts for flow rate.
Watt-hours… that’s joules / seconds * hours? This is cursed.
I believe it's just a matter of intuitively useful units. There's simply too many seconds in a day for people to have an immediate grasp on the quantity. If you're using a space heater or thinking about how much power your fridge uses kilowatt hours is an easy unit to intuit. If you know you have a battery backup with 5 kilowatt hours of capacity and your fridge averages 500 watts then you've got 10 hours. If you convert it all to watt seconds the mental math is harder. And realistically in day to day life most of what we're measuring for sake of our power bill, etc. is stuff that's operating on a timetable of hours or days.
16 replies →
Plenty of people use Joules or rather kilojoules or megajoules or even gigajoules for various purposes.
Watt hours is saying, how long will my personal battery pack last me that powers my 60 W laptop? Which is also fine in that context.
1 Wh = 3600 Ws = 3600 J
It is not more cursed than km/h (1 m/s = 3600 m/h = 3.6 km/h)
Both those units are more convenient than their SI equivalent and their "cursedness" come from the hour/minute/second time division.
If we had decimal time, as it was initially proposed with the metric system, we wouldn't have this problem, but we weren't ready to let go of hours/minute/second.
4 replies →
It's easier to figure out for people that measure power in watts and time in hours ... 1 kW for 1 hour is 1 kWh.
That camel's nose was already in the tent with the mAh thing in phone/etc batteries, now with electric vehicles we're firmly in kWh land.
Not to mention that's what the power utilities used all along ...
A watt of power multiplied by a second of time has an agreed upon name called joule, but a watt second is also a perfectly valid SI name.
A watt is a joule of energy divided by a second of time, this is a rate, joule per second is also a valid name similar to nautical mile per hour and knot being the same unit.
Multiplication vs division, quantity vs rate, see the relationship? Units may have different names but are equivalent, both the proper name and compound name are acceptable.
A watt hour is 3600 joules, it’s more convenient to use and matches more closely with how electrical energy is typically consumed. Kilowatt hour is again more directly relatable than 3.6 megajoules.
Newton meter and Coulomb volt are other names for the joule. In pure base units it is a kilogram-meter squared per second squared.
5 replies →
Of course it can be. Nobody does it in practice because it's inconvenient.
Watts = volts * amps and the people working with batteries are already thinking in terms of voltage and amperage. It'd be painful to introduce a totally new unit and remember 1 watt for an hour is 3.6kj instead of... 1 watt-hour.
Don’t stay there: EVs are even reporting consumption in terms of kWh/100km or kWh/100miles instead of just average kW.
6 replies →
Yep, it's stupid from a units consistency pov. A bit like using calories instead of joules.
But on the other hand we also use hours for measuring time instead of kiloseconds...
2 replies →
California found out pumped hydro isn't so "tried and true" when it was shut down during a drought due to lack of water behind the dam.
Not every area is as messed up as the Colorado river watershed...
All users (states) were given an allotment which, when it was set, was more than what would ever be the yearly supply.
From the outset it was essentially a free for all. Everyone was happy, they kinda got what they asked. It's just that they were all living in a paper reality
I should have explained in my original comment why I think those sentences are wrong. I'll do so now.
> pumped hydro [...] can store thousands of megawatts for days.
You can't "store" a megawatt – because you can only store energy, not power.
But another interpretation is, if you actually store thousands of megawatts (i.e. gigawatts) for days, then at the very least, 1 GW × 1 day = 24 GW⋅h. If we take "a few" to mean 3, then 3 GW × 3 day = 216 GW⋅h. I'm not sure there exists a large enough pumped hydro plant in the world that stores 216 GW⋅h of energy. So I think the article meant to say, "store a few gigawatt-hours to be released over a period of a few days".
> Media reports show renderings of domes but give widely varying storage capacities—including 100 MW and 1,000 MW.
Once again, you can't store megawatts of power, full stop. You can store megawatt-hours of energy. The linked article at Bloomberg said that a project in China is building 600 MW of wind power, 400 MW of solar power, and 1 GW⋅h of energy storage – which is the correct unit.
I'm old enough to remember when IEEE Spectrum was a respected technical publication.
The round-trip efficiency comparison (60-75% vs lithium-ion's ~90%) is interesting but somewhat misleading without context. For grid-scale storage, the relevant question isn't efficiency in isolation - it's lifecycle economics including capex, degradation, and replacement cycles.
Lithium-ion has superior efficiency but degrades significantly after 5,000-7,000 cycles, typically reaching 80% capacity in 7-10 years. If CO2 batteries can maintain performance for 20+ years with minimal degradation (which the article suggests), the lower efficiency becomes less relevant. You're trading 15-25% energy loss for potentially 2-3x longer operational life and no lithium supply chain dependencies.
The real breakthrough is duration-flexible storage. Lithium-ion economics break down beyond 4-hour discharge rates because you're paying for both energy capacity and power capacity. CO2 systems decouple these - the turbine size determines power output, the storage tank size determines duration. That makes them ideal for seasonal storage patterns where you might charge for days during high renewable production and discharge slowly over weeks during winter lulls.
What's missing from the article: what's the round-trip efficiency at different discharge rates? Does efficiency drop significantly when discharging over 12 hours vs 4 hours? That would determine whether these make sense for daily solar smoothing vs weekly wind intermittency vs seasonal storage.
I think it is generally polite to flag when you are using an LLM to write your comment, some people tire of reading the same style of writing over and over - even if the content of your comment is interesting!
Oh good point; I wouldn't have noticed if you didn't point it out. The last ~5 comments from yoan9224 are all in 4-paragraph format. A few comments before that are in 3-paragraph format. They all look suspiciously uniform in writing style, and very mechanical.
1 reply →
The system actually sort of uses the atmosphere as an ambient heat sink (when compressing) or heat source (when expanding).
I wonder if that heat could be stored in a more sensible way, e.g. as heated water in a tank near the bubble. This could improve the efficiency figures at short repeating patterns (charding at high noon, discharging through the night).
As far as I understand they do try to keep the heat around for the next decompression. As of course they need it. But I could not find what type of heat storage they use. Ultimately they "only" seem to need to store it for 12h, right?
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.
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.
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.
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.
3 replies →
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.
> For example I expect recycling costs to be significantly worse for the Li-Ion.
I think there's a good argument for the opposite.
Recycling costs for Li-Ion once we are doing it at scale should be significantly negative. There are valuable materials you get to extract, they aren't in that complex a blend to extract them from, and there's a lot of basically the same blend. The biggest risk in this claim is, I think, the implicit claim that we won't figure out how to extract the same materials from the earth much cheaper in the meantime cratering the end of life value of batteries - but in that event the CO2 battery technology is underwater anyways and the chemical batteries win on not wasting R&D costs.
By contrast while there's some value in the steel that goes into building tanks and pumps and so on, the material cost if a much lower fraction of the cost of the device. Most of the cost went into shaping it into those complex shapes. I don't know for sure what the cost breakdown of the CO2 plant looks like but if a lot of the cost is something else it's probably something like concrete or white paint that actually costs money to dispose of.
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.
1 reply →
I'm seeing round trip efficiencies around 75%.
That's not terrible.
These things would probably pair well with district heating and cooling.
That is shockingly good. EIA reports existing grid scale battery round trip is like 82% which do not have moving parts.
https://www.eia.gov/todayinenergy/detail.php?id=46756
1 reply →
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.
"I am seeing" as in do you use CO2 batteries at home or something?
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
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.
5 replies →
Sodium batteries will take 15 years to overtake LFPs cost. Stop gargling on hype please.
9 replies →
Lithium supply is limited. So an alternative based on abundant materials is interesting for that reason I guess?
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.
5 replies →
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.
6 replies →
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.
Different solutions for different needs.
It's good for engineers and planners to have multiple solutions available that provide better fit to their prerogatives and needs.
We don't need one solution to do it all. We need plural ones.
I agree with you: the real test isn't whether it's 30% cheaper today, but whether it holds its economics over 20–30 years at scale
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.
lithium yearly discharge is in single digit %, what a nonsense argument.
3 replies →
I wonder how much Google is factoring in the implicit cooling cycle? Because any pressurized gas energy storage is either including some advanced heat storage or is just venting the heat created during compression (the ancient Huntorf facility in Germany is infamous for that, super wasteful)
Usually you want to keep the heat and put it back into the compression medium during decompression and hope that losses from the heat storage aren't too big, but when you have a cooling use case nearby, you can use that low intensity heat to compensate heat storage losses, or even overcompensate. When you consider how much of the power input of a datacenter is typically used for cooling, compressed gas storage could be useful even if there was zero electric recovery (just time-shifting the power consumption for cooling to a time with better energy availability)
> Because any pressurized gas energy storage is either including some advanced heat storage or is just venting the heat created during compression
https://energydome.com/co2-battery/ diagram has water as the heat storage. Tanks of water get efficient at energy storage due to square-cube scaling.
I'm sort of thinking out loud here but could you have two batteries running simultaneously but on opposite cycles, so while one is cooling the other is heating? Obviously it wouldn't be 100% efficient but it might reduce some wasted energy.
The heat and cold are created by the compressing or decompressing the CO2 (our any other gas). If one battery is heating while the other needs heat that would imply that one is charging while the other discharges, which is rarely useful in normal operation
1 reply →
Why would you be charging one battery while discharging another? That would just be wasting energy.
If Google is colocating these with data centers, even low-grade heat that would otherwise be a loss could still be useful, or at least reduce how much active cooling the DC needs
Isn't this effectively neutral over time? Heat generated during compression, lost during decompression, so basically using the air as a heat storage medium?
I think what he's saying is you can boost efficiency if you compress a cooler gas. So if you could capture the "cold" that you get from discharging the device, and use it to pre-cool the air for the next cycle (or use it for the data centers cooling system) , it would be much more efficient.
1 reply →
Yes. A large radiator would handle both. I assume they just store the heat because hot water will be a lot more efficient at reheating the co2 than night time air and a pool with an insulated cover is not hard to construct.
>The company uses pure, purpose-made CO2 instead of sourcing it from emissions or the air, because those sources come with impurities and moisture that degrade the steel in the machinery.
So no environmental advantages. It's supposedly 30% cheaper than lithium-ion, but BYD cars have sodium-based based batteries on the road right now which CATL says will end up being 10-20$/kwh (10x cheaper than current batteries).
So what's the actual advantage of this ? I think it's just lucky to land just at the right time where batteries aren't cheaper enough yet.
To cite and expand on lambdaone below [1]:
> 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
Lambdaone is differentiating between the costs to store energy (measured in kWh or Joules) and the costs to store energy per time (which is power, measured in Watts). If you want to store the whole excess energy that solar panels and wind turbines generate on a sunny, windy day, you need to have a lot of power storage capability (gigawatts of power generated during peak power generation). This can be profitable even if you only have a low energy storage capability, e.g. if you can only store a day worth of excess solar/wind energy, because you can sell this energy in the short term, for example in the next night, when the data centers are still running, but solar panels don't produce power. This is what batteries give you -- high power storage capabilities but low energy storage capacities.
Of course, you can always buy more batteries to increase the energy storage capacities, but they are very expensive per energy (kWh) stored. In contrast, these CO2 "batteries" are very cheap per energy (kWh) stored -- "just" build more high pressure tanks -- but expensive per power (Watts) stored, because to store more power, you need to build more expensive compressors, coolers etc. This ability to scale out the energy storage capability independently of the power storage capability is what Lambdaone was referring to with the decoupling.
For what is this useful? For shifting energy over a larger amount of time. Because energy storage costs of batteries are so high, they are a bad fit for storing excess energy in the summer (lots of solar) and releasing it in the winter (lots of heating). I'm not sure if these "CO2" batteries are good for such long time frames (maybe pressure loss is too high), but the claim most certainly is that they can shift energy over a longer time frame than is possible with batteries in an economically profitable fashion.
[1] https://news.ycombinator.com/item?id=46347251
What an excellent explanation, thanks
Even if sodium-ion really gets to $10–20/kWh, you still have degradation, cycle limits, fire risk, and a practical lifetime that's maybe 10–15 years
If it is barely cheaper than lithium, it's much more expensive than traditional pumped storage.
Yeah, it's expensive to build, but then cheap to run for decades.
It's nice that we explore alternatives but this just seems like investor bait
Pumped hydro is just not a valid comparison. I wish people would understand that already… it’s only good for long term storage in certain key geographical regions. Its use case is very limited.
You don’t want to used pumped hydro for short term storage because the rapid cycling will drive up the maintenance costs. You actually hear about hydro power plants talking about installing batteries to reduce wear.
In these discussions please keep in mind that frequency regulation, short term and long term shortage are different applications with different needs. The costs for pumped hydro are generally reported with their target application in mind. It’s not as applicable to dedicated short term storage and certainly not applicable to frequency regulation.
4 replies →
AFAIU, pumped storage can only be built in very few locations around the globe.
1 reply →
Pumped hydro is not viable in most areas of the world. This is.
> So what's the actual advantage of this ?
I would posit that they hope Wright's Law will take hold; the components can be optimised and the deployment standardised. Also it looks as if most of the stuff can be made within the US or EU, dodging tariffs.
[dead]
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?
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.
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.
6 replies →
Fantastic detail, thank you.
>cubic inch
>cm
>oz
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.
The gotcha will be the “poor” round trip efficiency, in comparison to other storage technologies.
It’d be interesting to see if there’s any loss of efficiency with increasing storage duration too (relating to boil-off of the cryogenic side of the storage ?) because this would impact the economics of charging too.
I just get the feeling lithium/sodium ion for electricity and big piles of sand/dirt for heat are going to more-or-less win the energy storage race.
The funniest part is that the "implicit cooling cycle" might be more valuable for grid alignment than raw efficiency
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.
It has nothing whatsoever to do with sinking CO2.
2 replies →
It’s a battery not a sequestration technology.
If you think this is simple, wait until you learn about oceans and forests do!
Trees are literally CO2 based solar batteries: they take CO2 + solar energy and store it as hydrocarbons and carbohydrates for later use. Every time you're sitting by a campfire you're feeling heat from solar energy. How much better does it get that free energy storage combined with CO2 scrubbing from the atmosphere!
When you look at the ocean, it's able to absorb 20-30% of all human caused CO2 emissions all with no effort on our behalf.
Unfortunately, these two solution are, apparently, "too good to be true" because we're increasingly reducing the ability of both to remove carbon. Parts of the Amazon are not net emitters of CO2 [0] and the ocean has limits to how much CO2 it can absorb before it starts reach its limit and become dangerously too acidic for ocean life.
0. https://www.theguardian.com/environment/2021/jul/14/amazon-r...
Not nearly just Brazil: https://awpaadelaide.com/2025/08/10/who-is-clearing-indonesi...
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.
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.
CO2 is extremely dangerous in high concentrations because the body reacts and switch off the breathing.
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.
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.
5 replies →
> 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.
2 replies →
Company says safe limit is 70 meters, about 200 feet.
Easy to build infra and other stuff that far away, especially in locations where this is meant to be used.
There are many aspects of safety
1. If the puncture is due to hurricanes, etc, the danger is non existent. The hurricane will blow away the co2 in no time.
2. If the puncture is due to wear and tear, then the leak will be concentrated and localized. It could naturally diffuse.
CO2 meters can be installed around the unit for indication.
Oxygen masks can be placed around the facility for emergency use.
The dangers are very much mitigatable.
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.
So .. significantly less dangerous than a corresponding volume of natural gas, which is also unbreathable but also flammable/explosive?
Why is that a relevant comparison? Is anyone gathering natural gas in giant balloons near habitations or workplaces?
3 replies →
> People will also need to stay back 70 meters or more until the air clears, he says.
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.
2 replies →
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.
I suppose the people working at the plant will be wearing detectors and/or these will be placed at strategic locations in the area.
I have two solar panels that can generate around 960w/hr. Both panels cost around $400 ($200x2). Cheap.
Storing that energy is quite expensive. an Anker Solix 3800, which is around 3.8kwh, costs $2400 USD. To store 10kwh would cost $7200 USD (which gets us more than 10kwh).
If that cost asymmetry can come down then it becomes feasible to use solar power to provide cheap/local electricity in poor countries at a house scale.
There are way cheaper options than the Anker Solix 3800. Here are some options, in no particular order:
- $3,300: 10 kWh with 2x EG4 WallMount Indoor 100Ah.
- $3,110: 14 kWh with 1x WallMount Indoor 280Ah.
- $2,690: 10 kWh with 1x Deye RW F10.2 B
- Will Prowse's YouTube channel has reviewed several battery builds that are >10 kWh and near $2,000, but they're DIY assembly.
Batteryhookup has batteries for $40/kWh :) just put together a off grid setup for a friend and 8kwh cost $400 in parts!
1 reply →
And still much more than the cost of the solar panels, which was GP's point.
2 replies →
The YouTuber Will Prowse has an excellent site where he tracks his most recommended batteries (and other equipment like inverters) at any time. The prices are always changing, and there are new products all the time so check on the his list any time you are looking to buy:
https://www.mobile-solarpower.com
Like the other commenter said, batteries are a lot cheaper if you are willing to shop around. His top recommended budget battery today is a 4x your Anker Solix's capacity, and around 1/4th the price. You can find many 5kWh server rack batteries for under $1000 now.
Here's a quote I got for a solar install in the Philippines this week:
51.2v 314ah cells (15kwh battery) 16x 580-590w solar panel
Installed for 310k PHP = $5,275
I've also specced out 15-16kwh batteries using the Yxiang design for around the price of your Solix. The problem in the US is regulatory and a particularly predatory tradesman market at the moment.
Is that "regulatory" the problem or is it the solution? We'll know more 20 years from now, looking back at fire incident statistics.
(yes, I'm leaving it open if regulation makes a difference or not - for all we know it could even make a negative difference, helping companies that are better at regulation than at safety. But if I had to bet, I know where my money would be)
Western storage options are very expensive.
We are starting to see Chinese options pop up but not sure if I would install them yet.
https://www.docanpower.com/eu-stock/zz-48kwh-50kwh-51-2v-942...
Wait that Anker Solix 3800 costs more than my 84kwh battery containing _car_ (3.8 kwh x 22 batteries)? Something not right.
Are you saying you bought an electric car with functional 84kwh pack for less than 3 grand? If so I think the outlier is you. That is a better deal than I have seen.
The batteries in MWh range cost around 160 EUR/kWh all in. Including grid connection and BOP.
People have been experimenting with compressed gas energy storage for a long time. This one may finally have legs.
First thing I thought of was a startup from years ago, mildly surprised no one has mentioned it:
https://en.wikipedia.org/wiki/LightSail_Energy
I was really excited about them and was disappointed to see the project fail.
It seems using pure CO2 and scaling up to a massive size are significant boosts to this type of technology (in addition to the heat mitigation along the way).
"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."
And I suppose the whole thing is a closed system? Which means, none of the CO2 would be released to the outside?
Not intentionally during normal operation. I'm sure those things are gonna leak like hell, but still, it's just CO2 so it's not as bad.
Yes. If the CO2 was just released you would have to pay the energy cost to extract it from the atmosphere again.
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.
We need anything that scales quickly, safely, and cheap. Just getting us through the duck curve would be a tremendous win for energy. https://en.wikipedia.org/wiki/Duck_curve
Batteries already solve that.
https://blog.gridstatus.io/caiso-solar-storage-spring-2025/
We need every approach that's viable. Batteries are part of the solution, and will be in future. But I don't see why we we should assume they're better in every way than this approach
A principle in engineering is that for any market niche, only a few, or even one, technology persists. The others are driven to extinction as they can't compete. It's the equivalent of ecology's "one niche, one species" principle.
There are far more technologies going for the hours scale storage market than will survive. Sure, explore them. But expect most to fail to compete.
3 replies →
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".
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...
The point is that's already a well-served market. These competitors are like alternative semiconductors going up against silicon.
Oh: pumped hydro is not a "months" storage technology. The capex per unit of storage capacity is far too high.
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.
> What we need is a storage technology with a duration of months
Actually, having expandable, highly re-usable tech like this is much better when the capacities are in terms of hours.
This storage, combined with say 2.5x solar panel installation, could essentially provide power at 1x day and night.
Yes, and we have that. It's called Li-ion batteries.
6 replies →
Hell, even week will do a lot, you can start importing energy from areas that have currently better renewables conditions over night, even preemptively for a period of bad weather
I don't understand. Why is a duration of months preferable? What is the benefit above storing energy beyond say peak-to-peak? I suppose you can flatten out seasonal variation, but that's not nearly as big of a problem.
To see the importance, go to https://model.energy/
This site finds optimal combinations of solar, wind, batteries, and a long term storage (in this case, hydrogen), using historical weather data, to provide "synthetic baseload". It's a simplified model, but it provides important insights.
Go there, and (for various locations) try it with and without the hydrogen. You'll find that in a place at highish lattitude, like (say) Germany, omitting hydrogen doubles the cost. That's because to either smooth over seasonal variation in solar, or over long period drop out of wind, you need to either greatly overprovision those, or greatly overprovision batteries. Just a little hydrogen reduces the needed overprovisioning of those other things, even with hydrogen's lousy round trip efficiency.
Batteries are still extremely important here, for short duration smoothing. Most stored energy is still going through batteries, so their capex and efficiency is important.
You can also tweak the model to allow a little natural gas, limiting it to some fixed percentage (say, 5%) of total electrical output. This also gets around the problem. But we utimately want to totally get off of natural gas.
I suspect thermal storage will beat out hydrogen, if Standard Thermal's "hot dirt" approach pans out.
We desperately need mass energy storage. Everyone gets excited about renewable generation, but it is counterproductive without investing 5x-10x what we spend on generation in improved transmission and storage. It would be better to build 1/10th the amount of solar we do and pair it with appropriate energy storage than it is to just build solar panels. This is a crisis that almost nobody seems to talk about but is blindingly obvious when you look at socal energy price maps. The physics simply doesn't work without storage!!
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.
> 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.
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%.
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/
1 reply →
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.
1 reply →
Heat from compression is stored in a thermal energy storage system. Most likely something like a sand container.
they do say
> Energy Dome expects its LDES solution to be 30 percent cheaper than lithium-ion.
That's hardly a number.
30% cheaper than batteries from when? today? two years ago?
huge difference, 30% cheaper than lithium batteries feels like a pitch deck number from years ago to me
As always, diversity in the energy ecosystem is a huge plus. Time and time again we see that 'one size fits all' is simply not true so I'm a fan of alternative approaches that use completely different principles. This enables the energy ecosystem to keep exploring the space of possibilities efficiently. I hope this continues to be developed.
> Time and time again we see that 'one size fits all' is simply not true
Do we though? It feels like we're still in the stage where we're just trying to figure out what the best solution is for grid-scale storage, but once we do figure it out, the most efficient solution will win out over all the others. Yes, there may be some regional variation (e.g. TFA mentions how pumped hydro is great but only makes sense where geography supports it), but overall it feels like the world will eventually narrow things down to a very small number of solutions.
The point I was making isn't that we are or aren't actually narrowing down our options, it is that diversity of options is important. We have artificially limited diversity in our energy ecosystem and the rapid adoption of solar/wind/etc shows that. We could have been here decades ago if we actually encouraged diversity and exploration of alternate energy instead of actively discouraging it. Now that it is impossible to hold wind/solar back they are dominating. We should learn from that and encourage exploring diverse options in storage. Luckily I don't think storage has nearly the pushback that generation has had so I think it will be easier for many options to enter and find their niche.
I seem to recall from an article I read about this technology a few years ago that it's efficient partly because when the gas is compressed, they are able to store the heat that is produced, and then later use the stored heat for expanding the gas.
That seems important. I wish we knew how. I found an article that did mention the heat was "stored", with no further detail. The animation down on this page suggests it's stored in water somehow: https://energydome.com/co2-battery/
A better understanding of the science in the system: https://news.ycombinator.com/item?id=44685067 (162p/153c)
I don’t know much about chemistry, but is there a reason why they are using CO2 as the gas medium instead of something else? I was thinking ambient air would be readily available, and you don’t have to worry about suffocating people if it ruptures. Is CO2 particularly efficient to compress?
Air is no good because it has moisture in it. When you decompress it, it becomes ice, blocking and breaking pipes.
They never mention what advantage CO2 has over any other gas, like plain air?
The fluid in high pressure storage is a liquid, making the storage much cheaper. Liquid N2 (most of air) would require over 40 times more pressure or cold temperatures. Purifying out CO2 or any gas is generally a negligible cost.
I’m new to the idea of grid‑scale energy storage technologies, but this was a really clear and interesting introduction to how CO₂ batteries could help with long‑duration renewable energy storage. It’s exciting to see new approaches that might make solar and wind power more reliable and affordable. Thanks for sharing!
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.
It looks from the diagram that a turbine is the energy extraction mechanism? As you'd expect.
Correct, going from cold compressed liquid co2 though. For supercritical CO2 one would then heat up the gas and use it as a working fluid to turn the turbines further.
If you could reuse the same turbine, one could store excess solar/wind energy in the compressed gas form, and then fire up a natural gas or biomass gasification reactor and then feed the heat into the system to produce more electricity on demand.
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.
I wonder how does it compare to hoisting a concrete (or something heavy) block up a pulley system as an energy store? When you need the energy you let it slide down pulling some steel cable that turns a generator, or multiple cables into multiple generators. Or even a cascade of concrete blocks at different heights as a space saver.
Probably extremely poorly, as that's basically pumped hydro on _tiny_ scale. The amount of mass/water that fits into storage lakes is insane
Good point. I was thinking more about areas without much water and a large field of poles each hoisting several blocks. Sort of wind turbines but without the blades.
The article does address that.
...and even dangling heavy objects in the air and dropping them. (The creativity devoted to LDES is impressive.) But geologic constraints, economic viability, efficiency, and scalability have hindered the commercialization of these strategies.
I have one concern: what if the container bursts? CO2 is heavier than air, and a sudden pressure decrease will cool it down further, so it'll hug the ground. What would be a safe distance for the people around the plant to live without the risk of being asphixiated in an accident?
The article mentions > 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: 70 meters
> or more
I guess it just depends on how much oxygen you really need.
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?
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.
I thought it was ozone depletion, not greenhouse effects, that led to the fluorinated gas phaseout?
1 reply →
It's easy to liquefy, so it has a density advantage over air, and would be bad if released but not super bad.
Suffocation seems like the most relevant concern in the event of a catastrophic leak.
1 reply →
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
> 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.
It might function as a kind of cogeneration-style buffer, but CO₂ still gets emitted in manufacturing and maintenance — and I’m not sure the volumetric efficiency is all that compelling.
Still, if we ever end up with rows of these giant “balloons,” the landscape might look unexpectedly futuristic.
Would this be effective at smaller volumes? Could it get down to say the size of a washing machine for use at home?
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.
Also, parasitic losses in engines tend to be proportionally lower as the engines get bigger.
Compare the thermal efficiency of marine diesel engines to their automotive equivalents, for instance.
The turbines would have to spin at very high speeds at those sizes to be efficient.
Wasn't there a plan to use concrete blocks as energy storage medium by pulling them up a little bit at a time when there is surplus power?
Sure, some people have proposed that, but if you calculate how much has to be lifted to get 20 MW stored (or so), it gets pretty ridiculous pretty quickly. Like "Lift the largest aircraft carrier 20 meters" silly. You have some pretty severe size/mass issues.
It makes more sense to use water + a dam, but then again, we like to use water for things besides energy storage, and we're talking about a _lot_ of water.
This gas bag is effectively the same as water+dam, except the pressure is from the tanks and the compressor creates it, vs pumping uphill to create pressure.
The real question for me isn't the physics so much as ops over 20–30 years: maintenance, leakage, real-world efficiency after thousands of cycles
> 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.
Aren’t CATL already producing sodium-ion batteries for about 60% the cost of lithium-ion for equivalent capacity?
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.
Been hearing about this project for years, nice to see that it's gaining traction! Only question is that if they use captured Co2 initially or if they have to produce it.
There's remarkably little about the costs, given that's the main claim going for it vs the estabilished alternatives.
Had to wade thru miles of marketing muck to get to the tech talk.
So much potential! Get my CocaCola on the line! Heck give me Heineken too!
Peacetime technology from people who ignore the shooting war next door. Do you really want to build your energy system on huge soft targets? This looks much more vulnerable than solar arrays or battery installations to small-to-medium warheads (i.e anything from $500 FPV drones with an RPG round to $100k middle strike drones with 100 kg of payload).
It could be made much less vulnerable by dividing the gas storage balloon structures into a set of multiple smaller structures, ideally with some further internal partitioning so a single punctured surface does not release all the gas in that structure. Everything else is as 'hard' or 'soft' as any other piece of industrial plant, and can be hardened further by putting it inside a reinforced building or set of buildings, internal redundancy etc.
No reason this couldn't be put underground, except cost.
Customers will evaluate the risks. Thermal power plants are an easy target too, and oil and gas pipelines. And the oil tankers, according to the news of the last weeks. By the way, nobody cares about oil spills anymore. I guess all those ships were sailing empty /s
Of course they care about oil spills - this is why all the oil tankers in the last weeks were attacked when empty.
I ain't got time for this. Give me a paper, some numbers, and a plant flow diagram.
I just plant trees. Have a ton of land in NY, just doing my part.
Thunderf00t!! Get in here!
> The problem is that even the best new grid-scale storage systems on the market—mainly lithium-ion batteries—provide only about 4 to 8 hours of storage.
This isn't the first time I've seen this sort of claim this week about batteries.
If you're a journalist writing these words, stop doing that, and consider your life choices. Ask your boss for tuition assistance to put you through a 7th grade summer-school science class on matter and energy.
If you're a journalist writing these words in an ostensibly technical engineering journal? Christ. I don't even know where to begin.
More blowing up than taking off
no mentioning of storage overhead? how much energy being wasted for each charging and discharging cycle?
https://energydome.com/co2-battery/ states 75% efficient.
> And in 2026, replicas of this plant will start popping up across the globe.
> We mean that literally. It takes just half a day to inflate the bubble. The rest of the facility takes less than two years to build and can be done just about anywhere there’s 5 hectares of flat land.
Gotta love the authors comitment to the bit. Wow, only half a day you say? And then just between 1 to 2 years more? Crazy.
After the five years of planning approvals and grid connection approvals, of course.
Trees?