I mean, I suppose the purpose of these batteries are about seasonal rather than hourly differences.. but assuming you want to use them for something like coupling to a PV array and doing hourly trading:
The alternative isn't selling at a loss, it's using technology with higher round trip efficiency.
Say you have two batteries, both 1MW/4H systems, one lithium at 95% efficiency, one this CO2 thing at 80% effiency. In the highly volatile SE4 spot region in the Scandinavian grid, if you traded in 2019 you'd have made $80K USD with the CO2 battery, $155K USD with the Lithium one (assuming you traded perfectly).
A tigher efficiency envelope lets you exploit many smaller 10-20% cost gaps, rather than having to sit for many days to wait for gaps in the 30-40% range.
Not to say that Lithium would have a higher ROI over all than this technology, just to say that round trip efficiencies have significant impact on revenues here.
Here is where you're wrong: you're thinking in terms of 4 to 1 power to storage. A CO2 battery can have a very large storage for 1MW. It could potentially have a storage of 40 hours. You keep charging it for months, and then release it all when there is a week long lull of wind and solar production.
Such short bursts of energy are typical for Li-Ion batteries, but quite atypical for other forms of energy. It's the same principle as with the flow batteries.
The alternative isn't selling at a loss, it's using technology with higher round trip efficiency.
Say you have two batteries, both 1MW/4H systems, one lithium at 95% efficiency, one this CO2 thing at 80% effiency. In the highly volatile SE4 spot region in the Scandinavian grid, if you traded in 2019 you'd have made $80K USD with the CO2 battery, $155K USD with the Lithium one (assuming you traded perfectly).
A tigher efficiency envelope lets you exploit many smaller 10-20% cost gaps, rather than having to sit for many days to wait for gaps in the 30-40% range.
Not to say that Lithium would have a higher ROI over all than this technology, just to say that round trip efficiencies have significant impact on revenues here.