Huge kilometer square kites would be pretty cheap compared to the fuel budget of a ship, and clever routing and control systems can probably mean they reduce fuel consumption 80% for the same travel speed.
Not KM but 822m seems pretty close. I think you’re grossly overestimating the benefit from the kite. Seating’s current website says:
> A 1000m² sail surface to harness the power of the wind and tow ships. Based on modelling and preliminary land-based tests, Airseas estimates that the Seawing system can reduce fuel consumption and greenhouse gas emissions by an average of 20%.
I don’t think better routing will increase that to 80% even if you combine it with next gen tech that knows wave patterns and when a slot will be available to minimize speed and energy loss.
We need a path to remove fossil fuels from ships (& planes). There’s also industrial applications that need high heat that solar can’t really accomplish. Finally, solar & wind need insane battery capacity which when included pushes the economics strongly back in favor of fission and fusion.
We won't see discussions on that until we're serious about cutting fossil fuels.