> 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.
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.