CO2 Batteries That Store Grid Energy Take Off Globally

CO2 is in general less dangerous than inert gases, because we have a hypercapnic response - it's a very reliable way to induce people to leave the area, quite uncomfortable, and is actually one of the ways used to induce a panic attack in experimental settings.

If it were, say, argon, it would be much more likely to suffocate people, because you don't notice hypoxia the way you do hypercapnia. It can pool in basements and kill everyone who enters.

That being said it is an enormous volume of CO2, so the hypercapnic response in this case may not be sufficient if there's nowhere to flee to, as sadly happened in the Lake Nyos disaster you cited.

The last section of TFA is called "What happens if the dome is punctured?". The answer: a release of CO2 equal to about 15 transatlantic flights. People have to stand back 70m until it clears.

It would not be good, but it wouldn't be Bhopal. And there are still plenty of factories making pesticides.

> People will also need to stay back 70 meters or more until the air clears, he says.

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.

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'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.

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.

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.

CO2 batteries scale by adding more steel tanks or larger bladders. The expensive components (compressors/turbines) stay the same. Therefore unlike Li-ion, the CO2 battery becomes exponentially more cost-effective as the total required capacity/duration increases.

I'm seeing round trip efficiencies around 75%.

That's not terrible.

These things would probably pair well with district heating and cooling.

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

Lithium supply is limited. So an alternative based on abundant materials is interesting for that reason I guess?

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.

These days CO2 is actually quite commonly used in air-conditioners as a refrigerant, R-744. Fluorinated gases like Freon are being phased out due to being even worse for global warming.

It's easy to liquefy, so it has a density advantage over air, and would be bad if released but not super bad.

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