Recuperation recycles the energy normally lost during braking by storing and then using it for acceleration or starting, so saving fuel and cutting emissions.
When you're trying to save energy while driving it makes sense to recover it where you can. One way we've done this is to raise the alternator voltage when slowing down and braking. This increases battery charging and helps the car slow down. The alternator load is then reduced when accelerating to lighten the burden on the engine and cut fuel consumption. Recuperation is a feature of some of our BlueMotion cars.
Article source: www.volkswagen.co.uk