Chevy engineers spent a lot of time and effort to design the Volt to be as "pointy" as possible to reduce air drag... But you still need POWER to PUSH the Volt through the air. Faster you go... More POWER required.
If you are suggesting that you can put little windmills all over the Volt to recharge the battery... Windmills adds drag. It's like trying to pick your self up by pulling on your shoelaces. No matter how hard you pull on your shoelaces you can't lift your self off the ground.