CO2 batteries that store grid energy take off globally
spectrum.ieee.org319 points by rbanffy a day ago
319 points by rbanffy a day ago
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.
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).
> 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.
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.
There are two types of jobs, the ones which require you to know that a day is about 8.5x10^5 seconds, and those which don't.
True. Otherwise we would be using square meters for measuring gas mileage instead of miles-per-gallon (or litres-per-km) [1].
Well, if you want to be pedantic, it's litres-of-fuel per km-driven. That doesn't cancel as nicely, if you don't drop the annotations.
Arguably, we should probably use kg-of-fuel (or mol) instead of litres-of-fuel anyway.
"litres-of-fuel per km-driven" (Volume/Distance) is still fully reductible to an area: litres is still a volume (1 cubic decimeter) and km is still a distance (1x10⁴ dm) Maybe you meant that the other way around? Distance/Volume (as in Miles/gallon) is an Area⁻¹ (Distance⁻²), which is more difficult to imagine in space.
Now, Kg is a measure of mass (or weight, depending on who you are asking), which throws density into the equation, which is proportional to the temperature, which will vary according to where and when the driving takes place. But since the time and place, and hence the temperature is (allegedly) defined when the fuel consumption was tested, the density is a constant, and as such you can leave it out from the relation.
Mass = V*ρ
(I know, I am being pedantic² :)
If you car was fueled by a fixed pipe which it travelled along, consuming all the fuel in the sections of the pipe that it moved past but no more, what would the cross section of the pipe be?
If a car gets 50 mpg (UK gallons), the fuel consumption is equivalent to a circular string of diameter 0.27 mm.
> miles-per-gallon (or litres-per-km) [1].
The UK is metric except for distance and beer.
So the disgusting ‘miles-per-litre’ is presumably needed too.
Also the UK gallon is different from the US gallon. And the same applies to all the other non-metric fluid measurements such as pints and fluid ounces. Historically the UK gallon was used throughout the former British Empire (Australia, Canada, India, Ireland, Malaysia, New Zealand, South Africa, etc). By contrast, almost nobody ever officially used the US gallon except for the US (and a small handful of highly US-influenced countries such as Liberia).
Each standardised on a different gallon. Prior to that, gallons depended on that you were measuring.
One, a beer gallon, the other a wine gallon. The US still also has 'dry gallons' for things like pints of blueberries.
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.
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.
Don’t stay there: EVs are even reporting consumption in terms of kWh/100km or kWh/100miles instead of just average kW.
What people care about when talking about EVs and consumption is generally how much distance they can cover. If you take away the distance factor and just report power, it becomes meaningless/almost useless.
Many people think of driving in time rather than distance. I'd say it's actually more common to say a city is 3 hours away rather than 200 miles.
What makes kW less useful is really just that most EVs don't advertise their capacity very prominently. But if you knew you had an 80 kWh battery and the car uses 20 kW at freeway speeds, then it's easy to see that it'll drive for 4 hours.
The problem with this is that destinations are a fixed distance away, whereas their time distance is not fixed. In most journeys people want to reach a specific place rather than drive for a given amount of time.
I understand all this but the most important question for me is definitely still "how much distance can I cover on a charge"? That's why I prefer kWh/100km.
Directly reporting required power is still comparable among vehicles: 55kW vs 49kW, eg
Which is definitely less intuitive because it hasn't been introduced to the public, but is interchangeable in the same quirky way we already compare MPG (Distance/Volume) with lt/100KM (Volume/Distance)
Heh. To borrow an idea from xkcd (measuring gas consumption as area): The kWh measures energy, right? And energy is force times distance. So energy divided by distance is force! Let’s all start measuring EV consumption in newtons, folks. It even makes intuitive sense: It correlates well with how hard you need to push the car to get it going at the usual travel speed. But it sucks if you need to figure out how far you can travel on a given charge.
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...
Yeah, if only we would define seconds to be 13.4% shorter than that are, we could have 100ks days. Also, ksecs would be a really convenient unit for planning one's day: a ~15 minute resolution is just right for just about any type of appointment.
Oh, and 1Ms weeks, consisting of 7 working days and 3 off days sound nice too.
One can dream! :-)
Much better to make seconds slightly larger than 2 seconds, and move to a dozenal system throughout. One hour is (1000)_12 novoseconds. A semi-day is (10000)_12.
Oh, we should switch our standard counting system to dozenal a well.
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.
So when I torque all 20 of my car's lug bolts to 120 n-M, I've exerted 2/3 of a W-h? So if it takes me 4 minutes, I'm averaging 10 watts? That's neat. I wonder what the peak wattage (right as the torque wrench clicks) would be; it must depend on angular velocity.
Newton meter as a unit of energy is not the same as the newton meter unit of force for torque.
The energy unit meter is distance moved, while the force unit meter is the length of the moment arm.
This is confusing even though valid, so the energy unit version is rarely used.
You can exert newton meters of force while using no energy, say by standing on a lug nut wrench allowing gravity to exert the force indefinitely unless the nut breaks loose.
Ah! I guess that explains the "f" for "force" in the imperial abbreviation "ft-lbf", to distinguish it from work. I wonder if there's ever been an analogous variant for metric such as "Nmf"...
Hmm, I thought lbf was to distinguish the force unit from the mass unit (1 lbf = G * 1lb mass)
It seems the common thread is that the f means to introduce G, but not exactly. In my own research, the AI summaries are about as sloppy as I've ever seen, due to the vague and often regional differences (with the difference between ft-lb and lb-ft sometimes being described as relevant, as well).
> 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).
It ought to be cheaper at scale. Batteries' cost scales linearly with storage capacity. Cost for a plant like this scales linearly with the storage rate - the compressor and turbine are the expensive part, while the pressure vessels and gas bags are relatively cheap.
The bigger you build it, the less it costs per MWh of storage.
> Energy Dome expects its LDES solution to be 30 percent cheaper than lithium-ion.
Grid scale lithium is dropping in cost about 10-20% per year, so with a construction time of 2 years per the article lithium will be cheaper by the time the next plant is completed
i think it had something to do with CO2 can be made into supercritical state relatively easily, not for nitrogen or other common gases.
I'm sat here thinking: why not compressed or liquefied air?
The basic issue is that they need a phase change at a reasonable temperature. Liquifying air requires much lower temperatures than CO2.
> 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.
I'm old enough to remember when IEEE Spectrum was a respected technical publication.
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
a thermal-energy-storage system cools the CO2 to an ambient temperature
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?
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.
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.
>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.
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.
AFAIU, pumped storage can only be built in very few locations around the globe.
This is mentioned in the article, that you need very specific topography for water pumped storage. Additionally, it can require a lot of space and be quite expensive and time-consuming to build.
> 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.
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.
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.
Also: From what I understand the LFP battery degradation is essentially corrosion that is removed by recycling and you can retrieve 99% of the essential LFP elements and make it into a new battery. So economically we only need to extract the LFP related materials for each human user almost once, instead of oil over and over again.
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.
Do you think desalinating 10% of the world's ocean water is feasible? What are the energy resources necessary to do that?
Think of those numbers as one kind of in extreme case argument.
Another reality is that most of the global grid scale energy usage is not transport via mobile batteries that benefits most from high energy density lithium batteries that pack maximal energy from least weight.
Battery farms don't move, they can use other battery chemistries that are cheaper in resources and weigh a lot more per energy unit than lithium while still powering cities, smelters, processing plants, etc.
As for desalination in general, yes, there will be a lot more of that in coming years, fresh potable water supplies are stretched from a global PoV.
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.
...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%....
> existing grid scale battery round trip is like 82% which do not have moving parts.
This is incorrect for a lot of containerized lithium systems. They have a lot of moving parts in their AC systems - the compressors, the fans, the cooling water pumps.
Lithium cells really don't like to be hot. If you put them next to solar farms in the sun belt or if you discharge them moderately quickly, you'll have to cool them. This cooling system also eats into the overall efficiency, but what's even worse is that its the majority of the maintenance budget.
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.
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
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.
In fact, the limiting element for Li chemistries is generally the Nickel. Pretty much everything else that goes into these chemistries is highly available. Even something like Cobalt which is touted as unavailable is only that way because the industrial uses of cobalt is basically only li batteries. It's mined by hand not because that's the best way to get it, but because that's the cheapest way to get the small amount that's needed for batteries.
Sodium iron phosphate batteries, if Li prices don't continue to fall, will be some of the cheapest batteries out there. If they can be made solid state then you are looking at batteries that will dominate things like grid and home power storage.
> Even something like Cobalt which is touted as unavailable is only that way because the industrial uses of cobalt is basically only li batteries.
AFAIR Cobalt is also kinda toxic which is a concern.
But as far as that and
> In fact, the limiting element for Li chemistries is generally the Nickel
Isn't that part of why LiFePO was supposed to take off tho? Sure the energy density is a bit lower but theoretically they are cheaper to produce per kWh and don't have any of the toxicity/rarity issues of other lithium designs...
> Isn't that part of why LiFePO was supposed to take off tho?
It's the exact reason LFPs are taking off, especially in grid storage scenarios.
The high cycle life combined with the fact that all the materials are easy to acquire and dirt cheap.
> Isn't that part of why LiFePO was supposed to take off tho? Sure the energy density is a bit lower but theoretically they are cheaper to produce per kWh and don't have any of the toxicity/rarity issues of other lithium designs...
LFP cells have long since taken off. Tesla has been making vehicles with LFP battery packs for half a decade now.
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.
AFAIK, the brine pits are pretty economical, they just require ocean access.
What I'm somewhat surprised about is that we've not seen synergies with desalination and ocean mineral extraction. IDK why the brine from a desalination plant isn't seen as a prime first step in extraction lithium, magnesium, and other precious minerals from ocean water.
> What I'm somewhat surprised about is that we've not seen synergies with desalination and ocean mineral extraction.
I think these guys are basically using desalination tech to make lithium extraction cheaper: https://energyx.com/lithium/#direct-lithium-extraction
As I understand it (which is far from perfectly) it's still not using ocean water, because you can get so much higher lithium concentration in water from other sources. But it's a more environmentally friendly, and they argue cheaper, way to extract the lithium from water than just using the traditional giant evaporation pools.
Do you know how much magnesium you find with silicon and iron as olivine? It's just the silicon that we haven't yet tamed for large scale mechanical usage that makes them uneconomical to electrolyze.
likely a matter of location. desal tends to be on the coast and near cities which tends to be pretty valuable land, making giant evaporation ponds a tough sell.
You don't use ponds, you run the desalination to as strong as practical and follow up with either electrolysis or distillation of the brine.
But once summer electricity becomes cheap enough due to solar production increasing to handle winter heating loads with the (worse) winter sun, we can afford a lot of electrowinning of "ore" which can be pretty much sea salt or generic rock at that point.
Form Energy is working on grid scale iron air batteries which use the same chemistry as would be used for (excess/spare) solar powered iron ore to iron metal refining.
AFAIK the coal powered traditional iron refining ovens are the largest individual machines humanity operates. (Because if you try to compare to large (ore/oil) ships, it's not very fair to count their passive cargo volume; and if comparing to offshore oil rigs, and including their ancillary appliances and crew berthing, you'd have to include a lot of surrounding infrastructure to the blast furnace itself.)
It will take coal becoming expensive for it's CO2 before we really stop coal fired iron blast furnaces. And before then it's hard to compete even at zero cost electricity when accounting for the duty cycle limitations of only taking curtailed summer peaks.
Not that it's super relevant to this discussion, but I think the largest individual machines operated would probably have to go to high energy particle accelerators like the LHC at CERN or those operated by Fermi Lab.
Billions of dollars in cost, run 24/7 with virtually no downtime during regular operations, in underground tunnels with circumferences in the tens of miles, and all throughout is actively-coordinated super conductors and beam collimation in a high-vacuum tube attached to absurdly complex, ultra-sensitive, massively-scaled instrumentation (not to mention the whole on-site data processing and storage facilities). Certainly open to bring convinced otherwise, but aside from ISS in pure cost, so far it's my understanding that those are the pinnacle of large-scale machines.
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.
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.
Maintenance of the system is my biggest question. Lot of mechanical complexity with ensuring your gas containment, compressors, turbines, etc are all up to spec. This also seems like a system where you want to install the biggest capacity containment you can afford at the onset.
All of that vs lithium/sodium where you can incrementally install batteries and let it operate without much concern. Maybe some heaters if they are installed in especially cold climates.
from the picture, the compressor and generator located inside the dome. the dome is filled with CO2. maintenance people have to carry oxygen tank, or they die.
Don't even really need notable heaters if you regulate your thermal vents enough.
> Maybe some heaters if they are installed in especially cold climates.
Sodium batteries can operate down to -40C. There are very few places on Earth where they would need a heater.
Sodium batteries will take 15 years to overtake LFPs cost. Stop gargling on hype please.
That seems unlikely since they can use the same factories and the raw material cost is significantly lower.
It's not panacea. Only lithium vs sodium is cheaper and they can use lower grade graphite which is just slightly cheaper (overall 30% reduction). Rest is same while it's a new manufacturing process. Meanwhile 99.99% production is focused and will be continued focused LFP.
That entirely depends on how large the market for stationary storage is going to be. On top of the price, sodium has advantage of being safer and usable in wider temperature range.
Who in their right mind would pay 40% more to pick a dangerous and fussy product just because it's a bit smaller and lighter for their home?
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.
GP wasn't talking about discharge, losing a little energy, they were talking about wear and tear, as in the batteries aging fast while in a highly charged state.
Battery recycling still hasn't really left the "we can do it in a lab" stage.
The supply side for battery recycling hasn’t really taken off yet. Wait another ten or twenty years until large numbers of electric cars reach eol.
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).
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.
> Not burning the gas but using it as a compressed gas battery. It liquifies easier than air, etc., but would be a big fire risk if there were leaks while this is not.
FWIW Back in the day, Ammonia was used for refrigeration because it had the right properties for that process; I mention that one because while it's not a fire risk it's definitely a health risk, also it's a bit more reactive (i.e. leaks are more likely to happen)
> Seems neat.
Agreed!
Maybe use excess power to produce methane via the sabatier reaction, store that, and then burn it in turbines or use it in fuel cells when needed.
It’ll be interesting to see how the economics of these various solutions play out.
Except you have to trap and recycle the uncompressed CO2, hence that enormous bag to hold all that gas. Color me skeptical.
With compressed air, you just release the air back to the atmosphere.
They mention that and say it fits in a huge inflatable tent, which rings true. CO2 is more dense than nitrogen and oxygen which are most of air, and if you're storing it at ambient pressure you don't need a super strong vessel.
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
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.
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.
I understand this, but it coincidentally uses CO2 and it's hard for me to understand why the technology would sound "too good to be true" without imagining such a purpose.
It's a one-time "use" though, it's not consuming CO2, so it's not going to move any needle
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.
It's a gas in an open space, it diffuses very quickly.
Yep. When I had to fill CO2 tanks at a paintball shop yes there were times that I had to open a door (I mean we were talking a lot of fills in short time, btw fills had to start with draining the tank's existing volume so I could zero out the scale) but even indoors a door+fan was enough to keep even the nastiest of sale days OSHA compliant.
Also a 'puncture' is very different from the gasbag mysteriously vanishing from existence; My only other thought is that in cold regions (I saw wisconsin mentioned in the article) CO2 does not diffuse quite as fast and sometimes visibly so...
https://en.wikipedia.org/wiki/Limnic_eruption
I don't know the safety limits for this quantity, I hope the "70 meters" claim was by someone who modelled it carefully rather than a gut check.
It also deflates pretty slowly. I'd guess any breeze would remove the hazard altogether.
> 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.
The distance is likely calculated based on the stored volume and the area you cover until the height is significantly below head height (because as you point out CO2 settles to the bottom). Regarding the little house 15m from the bubble, they are not planning to build this in residential areas, so it's very unlikely that there would be a house within 15m just for operational purposes already.
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?
...huh, yeah, I don't love that either. Seems sketchy.
> putting houses around gas holders was discontinued in the UK.
Phased out during my lifetime. I grew up with them as part of the suburban architecture, e.g. https://www.google.com/maps/place/DUNHAM-BUSH+LIMITED/@50.86...
> 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.
It's unlikely that the thing will burst and disperse all CO2 immediately. It's just slightly higher pressure than the outside (that's the whole principle). So you have a slow leak of CO2 to the outside. You don't have to run that fast (or run at all).
The way I understood the quote, the safety distance is when they have to do an emergency deflate (e.g. due to wind). The way they calculate the 70 m is probably based on the volume and how large of a area you cover until the height is low enough that you can still breath.
Generally, because it's leaking to the outside, where there is going to be wind it will not stick around for long time I suspect.
> It's unlikely that the thing will burst and disperse all CO2 immediately.
This requires the people running this facility, and all the facilities based on it built by unrelated organizations in the future, to not cut engineering corners on the envelope. I don't take this for granted anymore. But as long as you don't get a big rip, then yeah, it'll be hard to build up a dangerous amount. I wonder if a legally mandatory cut and repair trial on the envelope would reduce risk significantly.
Speaking of wind, I also worry about whoever is downwind if there's a big release. I bet 70m is not quite far enough if it's in the wrong direction.
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 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.
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.
Probably extremely poorly, as that's basically pumped hydro on _tiny_ scale. The amount of mass/water that fits into storage lakes is insane
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!
And still much more than the cost of the solar panels, which was GP's point.
GP only has two panels that generate 960 W (I’m going to generously assume NMOT and not STC). That’s hardly anything, and certainly not what I would use to try and charge 10 kWh of battery like they’re suggesting.
But sure, I agree it would help if battery prices came down.
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)
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.
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...
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.
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
> 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.
They are good for about 1000 cycles.
This system can run for decades.
Utility-scale Li-ion batteries are good for an order of magnitude more than that.
"LFP chemistry offers a considerably longer cycle life than other lithium-ion chemistries. Under most conditions, it supports more than 3,000 cycles; under optimal conditions, more than 10,000 cycles."
https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery...
https://iopscience.iop.org/article/10.1149/1945-7111/abae37/...
This is the paper that claims 10,000 cycles under optimal conditions.
But if you read it, they measure Equivalent Full Cycles, and it seems that implies 10000 cycles at partial discharge, not full discharge.
The paper calculates everything at nominal discharge upto 80%. Meaning, the installed capacity has to be 25% more than paper value, leading to increased costs.
Add to that, batteries are complex to manufacture, degrade, lose capacity, etc. You need high level of quality control to actually ensure you are getting good batteries. This means, the cost of QA and expertise increases. They are costly to replace, even at an avg of 3000 cycles (roughly 10 years). Bad cells in one batch accelerate degradation and are difficult to trace out. Batteries operate best at low temperatures, so the numbers may vary based on installed location and climatic conditions.
A turbine and co2 compressor system is dead simple to manufacture, control and maintain. A simple PLC system and some automation can make them run quite well. Manufacturing complexity is low, as there are tried and tested tech. Basically piping, valves, turbines and generators. These things can be reliably run for 30 to 40 years. Meaning, the economics and cost efficiency is wildly different.
With such simplicity, they can be deployed across the world, especially in places like Africa, middle east, etc.
On the whole, batteries are not explicitly superior as such. There are pros and cons on both sides.
You can buy batteries for your home solar systems with ten year warranties.
3000 is still 3x your number.
In evaluating the importance of this, you need to consider not only the time value of money, but also what one might call the "time value of technology". Does it make sense to make the technology long lived when it's improving so quickly? Or do you just replace it in a decade when things are much cheaper? Was "this PC will last 20 years!" ever a selling point?
When evaluating these technologies, you have to look at not just what they cost now, but how rapidly the cost is improving. Batteries are likely improving more quickly than turbines and heat exchangers.
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...
Oh: pumped hydro is not a "months" storage technology. The capex per unit of storage capacity is far too high.
The point is that's already a well-served market. These competitors are like alternative semiconductors going up against silicon.
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.
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.
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
A better understanding of the science in the system: https://newatlas.com/energy/energy-dome-co2-sardinia/
Similar discussion: https://news.ycombinator.com/item?id=44685067 (162p/153c)
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/
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.
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.
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 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.
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
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.
There's remarkably little about the costs, given that's the main claim going for it vs the estabilished alternatives.
Trees?
> 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.
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.
More blowing up than taking off
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.
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
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%.
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.
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?
Heat from compression is stored in a thermal energy storage system. Most likely something like a sand container.
Thunderf00t!! Get in here!
> 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.
I ain't got time for this. Give me a paper, some numbers, and a plant flow diagram.
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!!
I just plant trees. Have a ton of land in NY, just doing my part.
no mentioning of storage overhead? how much energy being wasted for each charging and discharging cycle?
"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?
Yes. If the CO2 was just released you would have to pay the energy cost to extract it from the atmosphere again.
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.
> 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.
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.
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?
The original ones yes. They are already banned - but the next generation of fluorinated refrigerants are apparently ok for the ozone layer but have a greenhouse effect. That's my understanding anyway, I'm far from an expert.
Edited to add: https://en.wikipedia.org/wiki/Kigali_Amendment has some information on this.
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.
It is a necessary risk. Oxygen is dangerous when heat is involved, and its low critical point is harder to work with than co2.
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.
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.