Indeed, the cooling infra needed for cryo makes the price per watt go up by unreasonable amounts per unit length.
Also your cryo liquid should ideally be something that doesn't do the following things:
1. Leaks — shouldn't cause asphyxiation risk to humans who need to fix the leak. 2. Broken cable due to disaster – coolant doesn't turn into explosives when in contact with high voltage high current electricity.
However, UHV DC electricity in tunnels could be financially attractive and safe if you can cool the tunnels properly (no superconducting cryo)
> However, UHV DC electricity in tunnels could be financially attractive and safe if you can cool the tunnels properly (no superconducting cryo)
AC transformers are so much cheaper than DC converter stations that I don’t think this will ever be true. At the distances HVDC has a distinct advantage at, you wouldn’t be building tunnels. HVDC is mostly useful for grid ties between unsynchronized grids.