At first I thought that would be wildly impractical but CO2 goes supercritical at just shy of 90°F and a little over 1kpsi. Those kinds of pressures are pretty well unknown in a substation, but occur all the time in refineries and the like. It's basically just a pressure vessel with a relatively mild heater requirement. Eminently doable. I think we will probably see these deployed in the next few decades. SF6 is an amazing material but really, really horrible as a greenhouse gas.
- It doesn't exist (there is mention of a prototype, but all the images in the article are generic).
- The $3.9M funding ended May 18th https://arpa-e.energy.gov/programs-and-initiatives/search-al... and there doesn't seem to be a related paper (other than this IEEE "maybe" from April)
- The project is (unfortunately) called TESLA: Tough and Ecological Supercritical Line Breaker for AC 2022: https://www.sf6andalternativescoalition.org/wp-content/uploa...