> Solar panels and wind turbines could generate electricity which would be stored in batteries and then used to drive electric motors propelling the ship. I wo

> Solar panels and wind turbines could generate electricity which would be stored in batteries and then used to drive electric motors propelling the ship. I wonder what the efficiency of a wind turbine + engine would be compared to a sail. Ie. if the wind blows so a ship with a sail moves at 20 mph, how fast could the wind turbine + engine move it?