[MetroMPG]

Regardless of where you place the turbine, the end result will be a net energy loss. There's no free lunch.

The exception would be a turbine which is somehow shielded from the airflow (and where the shield does not negatively affect aerodynamics) but which can pop up into the airflow for the purpose of decelerating. Think: aerodynamic regenerative braking.

Not very efficient, of course (compared to electro mechanical or hydraulic regen).