How practical is this ambition? And what will be the challenges?
[0] https://ukcop26.org/one-sun-declaration-green-grids-initiative-one-sun-one-world-one-grid
It's just extending stuff that's already happening and helping developing nations get cheaper power by working together. Just common sense really.
Yes in the end it'll end up with a massive amount of infrastructure just due to scale, but our global power infrastructure is already mind bogglingly massive.
Unless you can solve that, the scope will be limited.
The European one is quite impressive and grows at a fair pace: https://en.wikipedia.org/wiki/Synchronous_grid_of_Continenta...
Physically interconnecting distant grids (the Intergrid (?!)) may be possible thanks to new ways such as HVDC. See https://en.wikipedia.org/wiki/Australia-Asia_Power_Link
However maintaining grid stability (at each and every moment: volume consumed = volume produced) and therefore regulating physical parameters (such as tension, electric curent...) in in real time (they all are to stay nearly the same everywhere) may be major challenges. A classical problem is: overload on a segment, you have to cut it, overloading another one... and such a cascade can bring the whole thing down in tens of seconds.
The costs are enormous, and there isn't enough political will to get it done. For most countries, investing that money into renewables provides is a better return.
https://spectrum.ieee.org/lets-build-a-global-power-grid is a good read.
I think we're still going to have liquid fuels for a while, and they might be better to use as energy storage if we can create them from excess solar and wind power.