unless they are getting their CO2 from capturing it out of the atmopsphere, I see this as a way to dirty up wind and solor even more than they already are from their manufacturing.
It's a closed loop system, so it doesn't seem particularly dirty to me, presuming the energy to run it will come from the renewable source that it's storing. The materials used to make it (steel, quartzite, PVC) don't seem too troubling.
Seems a bit cleaner than chemical batteries at first glance.
Spadacini adds: “The system is totally closed. We don’t consume any CO2, it’s just the working fluid that goes back and forth… for the life of the system, over 25 years. So we have no emissions in the atmosphere.”
So yes, it's a closed system