[ClumsyPilot]

"if you scaled up the bitcoin system linearly so it provided as much transaction capacity as Visa ... it would require a number of times more power than the entire world produces"

This is a complete fantasy - power consumption is driven by the desire to secure the network, it is not related to transaction volume.

There is an argument that power consumption would have to be significant because attacking the network has to be cost- prohibitive, and there are people working on POS and similar approaches.

Etherium is actually attempting to scale, their talks are very interesting .