This animation shows how windpowered rotor vechicles can go directly downwind or directly upwind, faster than the true wind. To simplfy matters the air mass is reduced to a thin column of air, that moves relative to the ground, and colides with the rotating blade of the rotor.
The only difference between the downwind and the upwind case is the pitch of the blade. In the downwnd case the rotor works as a propeller, turned by the wheels. In the upwind case it works as a turbine, that turns the wheels.