[catnipman]

and where will all of that hydrogen come from? and what are the net energy losses from producing it, compressing it to liquefy it, and then transporting liquid hydrogen?

[Yo-Yo]

and where will all of that hydrogen come from? and what are the net energy losses from producing it, compressing it to liquefy it, and then transporting liquid hydrogen?

Right now the vast majority of liquid hydrogen comes from Natural Gas.

[faucetman]

Water and electricity. The electricity can be from any source, but preferably the sun, hydroelectric, or wind.

https://www.energy.gov/eere/fuelcells/hydrogen-production-processes