[pbmonster]

> How often does this need maintenance though?

Moving parts in salt water? Frequently.

The positive thing about this design is that maintenance is potentially much easier than on an seafloor mounted turbine: if the tether is long enough, you can just make the craft surface next to a maintenance vessel with a small crane. No divers necessary, and no giant crane platforms like for offshore wind turbines, either.

[Sammi]

> No divers necessary, and no giant crane platforms like for offshore wind turbines, either.

This is critical to the economic viability of the project.

[pbmonster]

It's certainly one advantage.

I still worry about some of the technical aspects. The craft is going to pull it's own tether through the water behind/"under" it while it "flies" loops in the current at a speed faster than the current itself. That must induce quite a bit of drag, right? Especially because that tether is delivering several megawatts of electric power do the anchor, while holding all the mechanical load of that power being generated. That has to be a beefy cable. And the joints where that cable meets the craft and the anchor are moving parts, for all intents and purposes.

I also wonder how much the craft actually resembles a full submarine. Are there ballast tanks and ballast pumps for altitude control? Full set of diving and directional rudders? What happens when any of those fail?

Potential complexity is certainly higher than for an offshore wind turbine.