It really depends on how much air resistance there is in the car to begin with. The more resitance the more likely it is to convert some back into energy. His design looks inefficient to begin with so I think there is a chance to capture energy here. Say you had a flat cross-section with 100% reistance and then compared it to a flat cross-section with a hole in it where a turbine was mounted. You would both reduce air resistance to some extent and increase energy capture by driving the air past the turbine. But the less resistance you have to start with in the body design, the more likely you are to add resistance by adding on a turbine.
In order to analyze the inefficiency of that contraption you have to compare his vehicle with an identical one where the turbine has been removed.
The turbine-less car will consume less energy for the same trip, not more as he claims.