Eli5 how CO2 batteries work, and why are they better than lithium-ion batteries?

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Eli5 how CO2 batteries work, and why are they better than lithium-ion batteries?

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I think the attraction is that you can scale the amount of storage cheaply once the system’s in place.

The costly / difficult part is the gas compressors and expansion turbines (the hardware that makes the gas a liquid, so it can be stored with very high density and then turns that stored pressure back into electricity when it’s released through the turbines). The cost of that scales with the power required (one setup to power one small city, a bigger but similar to power a large city, a bunch of them to power a country). But it doesn’t change whether you’re storing enough energy to power that city for an hour, a week or a year.

The amount of energy that can be stored is limited only by the size and number of the tanks you put the pressurised / liquified CO2 into. You’ve just built another wind-farm and need to be able to store its output for use on windless days? Add some more relatively inexpensive steel tanks. Another solar farm? More steel tanks.

Round-trip efficiency, as long as it’s not ludicrously bad becomes less relevant when you have large amounts of (more or less free to operate) generation capacity.

So, it’s less efficient than state-of-the-art lithium battery technology – once you’ve built that extra wind turbine or two to cover that loss, you’ve covered it.

It’s arguably much more useful than battery storage, because of the need to store a lot of energy.

Solar doesn’t work at night, wind doesn’t work on calm days. If we are to become dependent upon solar / wind we need to allow for lengthy periods of gloomy weather with little wind, if we want our lights to remain on.

This needs energy storage on a scale way beyond what we can do economically with chemical batteries. There’s a limit to the size of artificial lakes we can build for pumped hydro. But we can make a lot of big steel pressure tanks quite cheaply to store compressed / liquified gas. They don’t wear out, like a chemical battery. As long as they don’t leak, the energy can be stored for an indefinite period.