CO2 Battery
energydome.com
energydome.com
https://www.latitudemedia.com/news/form-energy-brings-in-mor...
The scale of investment required makes it quite hard for new companies to compete on cost:
https://www.theinformation.com/articles/battery-industry-sca...
I worry the answering that question requires answering this question: whose negative externalities?
What I like that I'm hearing about this CO2 battery, whether true will have to be seen, is that it might rely on off the shelf components, that's great, means the supply chain can be simple, and has longer life in the first place. And that while potentially even cheaper?
If your process gets 90% of the lithium out of the battery, after 7 cycles more than half of the lithium is gone. Therefore Mining can’t stop even when the market doesn’t grow anymore.
We don't know how long that process will go on, but in any case the amount of lithium needed will be a steady state, assuming constant need for batteries. But much more likely we will see ever increasing demand for batteries, just as we do for steel or copper or whatever minerals power our current economy.
/s
Personally of course, I don't think this matters at all: old lithium batteries degrade into salt and don't contain harmful chemicals. There's no real indication we'd ever have a problem dealing with them, even if it was just throwing them all into a big hole till the hole looks enough like a natural lithium source to mine again.
If a product has twice the lifetime then you are going to have half the waste. I'm not sure how that is irrelevant.
For batteries this is definitely true: we're not even close to storing weeks worth of every yet, and the more you can store the more flexible and useful they become.
I am very interested in this question, but those who raise it never have answers about the negative impacts of mining lithium.
For example, the amount of lithium needed for an EV is an order of magnitude less than the amount of steel needed. What is so bad about lithium mining that it's 10x worse than iron mining, pound for pound?
Nobody has ever answered my request for environmental concerns with a concrete environmental lithium mining concern, such as acidification that can sometimes happen with iron mining.
I've researched and researched, found nothing, which leaves me thinking that the worst case scenario for lithium is no worse than the worst case for iron.
Meanwhile, we have such immense documented harms from fossil fuel extraction that nobody ever questions again, or with the same intensity that's reserved for supposedly toxic lithium batteries.
The apparent benefit is massive, so any delay seems to cause massive harm to the environment.
I think we need to flip the question: where is the proof that coal/oil/iron is better for the environment than mining and recycling batteries? (BTW, it's at least 20 years now for grid batteries, with lifetime going up all the time...)
So if an electric car requires 2000 pounds of iron and 50 pounds of lithium, that works out to 4000 pounds of iron ore that needs to be mined and refined, vs 25,000 pounds of lithium ore.
Lithium is also extracted via brine, as opposed to hard rock. Most of the environmental reporting has been on the brine approaches, which currently are in high elevations of South American mountains, and the problem appears to be mostly the use of land and taking that land out of the ecosystem for economic use as drying pools. But the same problem occurs with mining, too!
means recycling of lithium batteries will be a thriving business. (i.e. big difference from recycling of say tires or plastic bottles, more like, pretty successful, recycling of aluminum, and even better than it)
No one made fortune in Li-ion recycling in all those years. Li-ion cells remained disposable.
Spodumene is dispersed among other minerals into rocks and it only forms a few percent at most of those rocks, if not only fractions of a percent.
The rocks must be crushed and spodumene must be separated from the other much more abundant minerals, by flotation or similar mineral concentration techniques, before going further to chemical processing.
So your 670 pounds must be multiplied by a factor like 100, varying from mine to mine.
Some multiplication factor must also be used for the iron ore, which is also mixed with undesirable silicates, but iron oxide may reach up to a few tens of percent of the rock, so the multiplication factor is much smaller.
> The mine sets a chemical-grade specifications benchmark of 6.0% Li2O minimum and 0.8% Fe2O3 maximum.
Spodumene is 0% iron. How much lithium does it contain on a Li2O basis? 8%, I think:
You have: lithium + aluminum + 2(silicon + 3 oxygen)
You want:
Definition: 186.089
You have: (2 lithium + oxygen) / 2 _
You want: %
* 8.0282762
/ 0.12455974
No, as it turns out. The paper linked just before that says that none of the rock is quite that lithium-rich https://pubs.geoscienceworld.org/segweb/economicgeology/arti...:
> The lithium ore zones comprise mainly spodumene, apatite, and quartz, with some ore zones returning upward of 5 percent Li2O.
OTOH, that paper is from 01995, so maybe there are new findings since 30 years ago. It says the reserves there were 4% Li2O. Later in the paper, it explains:
> The hanging-wall lithium zone in the main pegmatite is generally richer (up to 5% Li2O, equivalent to 60–80% spodumene) than the footwall lithium zone
That seems to contradict adrian_b's strong statement:
> Spodumene is dispersed among other minerals into rocks and it only forms a few percent at most of those rocks, if not only fractions of a percent.
It could still be true at other mines.
I do think a plug-in hybrid would be better for when I'm not traveling, but I bought this car specifically for travel.
A 20 gallon tank produces 400 pounds of CO2 for every fill up.
Even manually filling a tank by lifting a series of five gallon containers would seriously reorient the average person's conception of their fuel usage.
If the processes to extract Lithium from recycling become cheap enough to compete with the prices of mined Lithium, then that happens.
Processes still need to be invented/scaled for that to happen: the only real way to deal with damaged or charged cells that I know of is to deep freeze them, shred them, and then defrost them slowly.
But in either case: Lithium is going to end up as waste. Making it cheaper to make cars affordable and the grid more stable means that disposable batteries will be even cheaper.
I don’t know how modern batteries fare in landfills: Most modern solar panels, for example, are relatively clean (mostly aluminum, silicon, copper, wee bits of lead). But not a waste management expert.
https://www.redwoodmaterials.com/news/responding-recovering-...
They've been working hard at recycling, and the biggest challenge at the moment is actually getting old batteries for the process. There's not many in-service batteries reaching end of life yet, so they mostly deal with production scrap.
Round trip efficiency is way worse than lithium, but that might not be meaningful for grid batteries. You just want something that cheaply scales.
"Grid batteries" are also a wide concept, from retired electric car lithium packs to 100-hour-scale batteries like what Form is building. You need 3 types of battery, though the two fast ones may want to be unified: - grid stabilizing/synthetic inertia (1~20 C charge/discharge rate) - day/night PV energy shifting (0.15~0.3 C charge/discharge rate) - multi-day weather pattern smoothing (around the 0.01 C Form Energy is targeting)
Other than that the grid stabilizing kind needing much higher security/criticality due to bugs/errors in it's behavior threatening e.g. the European super grid, they would all benefit from co-locating with large solar farms and being connected on the DC side to share AC-side current capacity of the as-built infrastructure (from the inverter/converter through the lines and nearby transformers).
[0]https://www.pv-magazine-australia.com/2025/03/12/energy-dome... [1]https://energydome.com/energy-dome-inks-a-strategic-commerci...
Once R&D costs are covered, capacity scales with the size of the gas bag. Without competition from EVs or the volatility of resource extraction markets there's a clear path to profit here for 10hr+ grid-scale energy storage.
- Round trip efficiency: how much electricity comes out from electricity going in
- $/kWH capacity: lower is better, how does the battery cost scale as additional energy capacity is added?
- $/kW capacity: lower is better, how does the battery cost scale as additional power capacity is added?
- power to energy ratio: higher is better, to a certain point, but not usually at the expense of $/kWh capacity. If your ratio is 1:100, then you're in range of 4 days duration, which means at most 90 full discharges in a year, which highly limits the amounts of revenue possible.
- Leakage of energy per hour, when charged: does a charged battery hold for hours? Days? Weeks?
These all add up to the $/kWh delivered back to the grid, which determines the ultimate economic potential of the battery tech.
Lithium ion is doing really great on all of these, and is getting cheaper at a tremendous rate, so to compete a new tech has to already be beating it on at least one metric, and have the hope of keeping up as lithium ion advances.
The largest exporter is Australia and the largest importer is China. Were lithium abundant, why does China import most of its lithium?
Australia also exports a billion tons of iron ore to China. Iron ore is everywhere, but easier to mine good ore in Australia and ship it. Shipping is really efficient.
sure, lithium is more abundant than gold or silver but lithium access is not secure. Given that the largest lithium processing facilities by far are in one country (Chile), the supply of lithium is far from secure.
"LFP contains neither nickel[35] nor cobalt, both of which are supply-constrained and expensive. "
[35] pdf https://nickelinstitute.org/media/1987/nickel_battery_infogr...
For buying LFP cells, I would start here: https://diysolarforum.com/
Such as for example the awfully-often mentioned seasonal Europe setup of green summer hydrogen injected into former methane caverns, to be fed to gas turbines in winter.
Though I guess it's hard to measure $/kWh due to usage of natural formations.
Then there's the up-and-coming opportunity for green iron refining (ore to metal), which becomes financially practical when fed with curtailed summer surplus from integrated PV/battery deployments who's entire AC and grid side is undersized vs. PV generation capacity, using day/night shifting with local storage and peak shaving into iron electrolyzers (which would use some of the day/night shifting battery's capacity to increase over-the-year duty cycle of the iron electrolyzers).
For reference we're looking at capex for the electrolyzers (assuming 30% duty cycle average over a year, and zero discount rate over 20 years expected lifespan) around 0.1$/kg iron (metal) and electricity usage around 3 kWh/kg iron (metal).
While there is no leakage as such, the storage vessels might require continuous cooling, unless they are buried deep in the ground and they are very well insulated.
For great enough capacities, so that the costs of the turbo-generator and of the compressor become relatively small, the cost per stored kWh should become significantly lower than for batteries, especially when considering the far longer lifetime.
For small capacities, batteries are certainly preferable, but for very large capacities this should be a very good solution.
A gas-based design seems like it would be better at a small scale - e.g. the facility in the link has a reservoir the better part of a mile away from the turbines, and has a max output of 600 MW or so.
CO2 may actually be a good working fluid for the purpose - cheap, non-toxic except for suffocation hazard, and liquid at room temperature at semi-reasonable pressures. I'm not an expert on that sort of thing, though.
The major advantage over pumped hydro would be you do not need very specific geography to make it happen (90 - 300+m change in elevation)
- What's the energy areal and volumetric density kWh/m2 & kWh/m3 of this storage?
- How did they derive their CapEx savings figures?
- What's the peak charge/discharge rate of an installation?
- Can this storage be up/down-scaled in capacity and rate and by what limiting factors?
One of the few numbers I could find on their site was:
> Our standard frame 200MWh battery requires about 5 he (12 acres) of land to be built.
They also refer to it as a "20MW/200MWh" plant.
They say that they keep CO2 in liquid form at room temperature, then turn it into gas, and grab the energy so released.
* Isn't the gas be very cold on expansion from a high-pressure, room-temp liquid? It could grab some thermal energy from the environment, of course, even in winter, but isn't the efficiency going to depend on ambient temperature significantly?
- To turn the gas into the liquid, they need to compress it; this will produce large amounts of heat. It will need large radiators to dissipate (and lose), or some kind of storage to be reused when expanding the gas. What could that be?
- How can the whole thing have a 75% round-trip efficiency, if they use turbines that only have about 40% efficiency in thermal power plants? They must be using something else, not bound by the confines of the Carnot cycle. What might that be?
1. Decompressing the gas can be used to do work, like turning a turbine or something. It's not particularly efficient, as you mention, but it can store some energy for a while. Also the tech to do this is practically off-the-shelf right now, and doesn't rely on a ton of R&D to ramp up. Well, maybe the large storage tanks do, but that should be all. So it _does_ function and nobody else is doing it this way so perhaps all that's seen as a competitive edge of sorts.
2. The storage tech has viable side-products, so the bottom-line could be diversified as to not be completely reliant on electricity generation. The compressed gas itself can be sold. Processed a little further, it can be sold as dry ice. Or maybe the facility can be dual-purposed for refrigeration of goods.
3. IMO, they're using CO2 as a working fluid is an attempt to sound carbon-sequestration-adjacent. Basically, doubling-down on environmentally-sound keywords to attract investment. Yes, I'm saying they're greenwashing what should otherwise be a sand battery or something else that moves _heat_ around more efficiently.
Heat-based energy storage is always going to be inefficient, since it's limited by the Carnot efficiency of turning heat back into electricity. It's always better to store energy mechanically (pumping water, lifting weights, compressing gas), since these are already low-entropy forms of energy, and aren't limited by Carnot's theorem.
I don't know much about this CO2 battery, but I'm guessing the liquid-gas transition occurs under favorable conditions (reasonable temperatures and pressures). The goal is to minimize the amount of heat involved in the process, since all heat is loss (even if they can re-capture it to some extent).
So, in a hot climate, they need to store it deep enough underground, and cool the liquid somehow below ambient temperature.
Um no, that's unfair. CO2 is an easy engineering choice here. It's easy to compress and decompress, easy to contain, non-flamable, non-corrosive, non-toxic and cheap. It's used in many applications for these reasons.
While CO2 is now a great evil among the laptop class, it has been a miracle substance in engineering for roughly 200 years now.
You can see it in the little animation on their website. It's marked TES (thermal energy storage).
It looks like their RTE is based on a 10 hour storage time. The RTE is going to drop after their sweet spot, but if they're just looking to store excess energy from solar farm for when the sun isn't shining that's probably not a huge problem.
I wonder if something like the paraffin phase transition could be used to limit the temperature of the heat reservoir, and thus the losses during storage.
I am _very_ suspicious the efficiency is anywhere close to 75%.
E.g. if they can use the waste heat for district heating and count that as useful work.
To evaporate something, you need to give it energy (heat). The energy flux through the dome walls is not huge, so CO2 boils away slowly.
> - To turn the gas into the liquid, they need to compress it; this will produce large amounts of heat. It will need large radiators to dissipate (and lose), or some kind of storage to be reused when expanding the gas. What could that be?
Well, you have this giant heatsink called "the atmosphere".
> - How can the whole thing have a 75% round-trip efficiency, if they use turbines that only have about 40% efficiency in thermal power plants?
A quirk of thermodynamics. CO2 is not the _hot_ part, it's the _cold_ part of the cycle.
To explain a bit more, if you confine CO2 and let it boil at room temperature, it will get up to around 70 atmospheres of pressure. You then allow it to expand through a turbine. This will actually _cool_ it to below the room temperature, I don't have exact calculations, but it looks like the outlet temperature will be at subzero temperatures.
This "bonus cold" can be re-used to improve the efficiency of storage or for other purposes.
If this is intended for small-scale to medium-scale on-premise storage then the evaporating CO2 could also serve as the cold side of a building-size AC system for extra efficiency during the high demand portion of the duck curve.
I think there may be quite a market for maintaining hot and cold (and pressurized/liquified) sinks throughout the day/night cycle in highrises or entire cities.
I wonder if they design in flow channels for the heavier CO2 to flow down to safe, unpopulated areas.
Is there an advantage to the domes? IIRC some CAES system are put into old mines, that sort of thing.
Not sure if there's more scattered around the site, but that's on the front page.
Instead, it's compressed gas. Which is fine and possibly the best solution in certain contexts. But, it isn't exactly revolutionary or necessarily preferable to Li-ion most of the time.
So it is much easier to store a high amount of energy than it would be to store that energy in compressed air.
I can't exactly find what sort of specs an installation of a large co2 battery might have, so it may be small beans relatively speaking, but that is still a lot of co2 in a very small area, and I certainly hope that both the engineers and regulators know what they're doing with it.
It also has to be pretty big, which doesn't matter too much other than a critical failure would be more impressive.
They say no leaks, but I'm sure there will be SOME CO2 leakage. Hard to make something like this with gases that doesn't leak at least a little. You could offset that with some CO2 capture via atmospheric distillation.
I'd mostly be wary of what the actual costs and operational experience are. This device has moving parts that a battery doesn't. Looking at their news page, I see announcements of projects and partnerships but I don't think that they have any completed projects running yet. I suspect that their CAPEX comparison, where they show lithium ion batteries as 70% more expensive, may be aspirational rather than demonstrated. There are several companies that have already installed megawatt-scale lithium ion grid storage today: Samsung, BYD, Tesla, Fluence, LG Chem... and many of these projects have published costs and operational experience already.
I'm skeptical of their cost claims. Turbines aren't cheap and compared to batteries, they require significant maintenance. And while you can increase energy storage by increasing the size/number of CO2 tanks, the only way to increase power output (or "charging" speed) is to add more/bigger compressors and turbines.
There's also the issue of volumetric energy density. Wikipedia says that compressed CO2 storage has an energy density of 66.7 watt-hours per liter, though it's unclear if that's before or after turbine inefficiencies.[2] And that's the density in a compressed tank. It doesn't count the volume of the low pressure dome, which is many times larger. For comparison, lithium batteries are 250–700Wh per liter depending on the chemistry. Specific energy (energy per unit mass) is better than lithium ion, but since these are fixed installations, mass isn't a major concern.
Considering their claims are for a theoretical full scale plant, and that the numbers are already worse than batteries (75% efficiency, lower volumetric energy density, $200/kWh), I'm not optimistic. This technology might have niche uses, but I don't see it competing with most lithium battery installations.
That said, I hope I'm wrong. The more energy storage solutions we have, the better our future will be.
1. https://www.energy-storage.news/energy-dome-launches-4mwh-de...
2. https://en.wikipedia.org/wiki/Compressed_carbon_dioxide_ener...
I honestly don't see this really taking off, batteries are too cheap already, people just haven't really realized yet.
You can just order 1kWh of storage as a prismatic LiFePO cell for about $60 and have it delivered in the same week. Battery management and inverters are a solved problem, too, and don't have moving parts either.
It's sort of like arguing for going back to steam engines because we've got a new way to boil water.
A large portion of power comes from new and exciting ways to boil water that turns a turbine ;)
Most fossil fuel plants are water boilers as are all nuclear plants.
There's even some solar power plants that are effectively just water boilers.
The mechanical complexity is what worries me most - CO2 phase changes, compression/decompression cycles, heat exchangers...that's a lot of potential failure points compared to solid-state lithium cells. When researching portable power stations (I used gearscouts to compare $/Wh across different capacities), even budget lithium units are getting surprisingly cost-effective. We're seeing <$0.30/Wh for some models now.
That said, if Energy Dome can achieve reasonable $/kWh at grid scale without the lithium supply chain constraints, the efficiency trade-off might be worth it. The real question is whether the mechanical complexity translates to higher maintenance costs that eat into any capex savings.