carbon dioxide the future of 2020?

[brad__34]

im involved in replacing the current R22 refrigeration system in Harrods shopping centre, london After much consideration into replacement refrigerants ive started to wonder if perhaps replacing nessercery fixures and fittings to make the project "future proof" would be an option? However it would seem, at an enormous cost and work load.
Has anyone delt with a job of this scale involving C02. Would it all be worth it? and if so could they share some feedback.
Thanks

[Brian_UK]

Working in Harrods eh? Oh boy, I don't envy you at all.

Been there some years ago and it was a right pain.

[NoNickName]

co2 is now state of the art for large supermarkets, where LT and MT are used. The mostly used compressor lay out is cascade, having LT stage with subcritical CO2.
Other applications of CO2 are for driers and heatpumps, with transcritical CO2 circuit.
These days, water boilers are appearing, again with transcritical CO2, having discharge temperature in excess of 130/140°C, and water cooled gas cooler.
From an energetical point of view, it is not worth it, because the COP of CO2 subcritical is approx the same of R404a for LT applications in comparable applications. HC, especially R290, has higher COP for Evap T of -35°C.

Different story for T-critical: no other refrigerant will give you energy at that temperature.
Also, CO2 is very cheap, almost free, and can be freely released in the atmosphere in case of emergency or for vacuuming.