Past exam of the short options paper shared by Prelims and Parts A and B of the physics course of the University of Oxford / 2018 / S19 / 2 / b / Solution

Regenerative braking in an electric vehicle converts part of its mechanical kinetic energy back into electrical energy stored in a battery, rather than dissipating it all in friction brakes. An industrial recuperative heat exchanger transfers heat from a hot exhaust stream to incoming process fluid, reducing the required new heat input.

Both recover energy that would otherwise be rejected, while remaining subject to conversion losses and limits on the usefulness of the recovered form. Neither is a source of net energy over a complete cycle.