Mohtalim

Ocean currents can power the world, say scientists
http://www.telegraph.co.uk/earth/energy ... tists.html

This is probably an old idea. I wonder what the environmental impacts of slowing huge waterways would be. At least it seems they compared it with dams.

What happens when you're not near an ocean current or even large enough river? Do you hope your neighbors will send you power over their grid and not mess with you? I guess this does work on a small scale too, so could be done as lots of small generators which is also good for reliability.

I suppose something similar could be done in place of wind turbines too?

In the Great Lakes, where they're building the first one, there's more risk of damage from the ecosystem than damage to it. Zebra mussels run rampant, and I'm sure they'd impede the motion of the cylinders.