In a hybrid electric vehicle, explain the primary benefit of regenerative braking in terms of energy recovery and how it directly impacts the demand on the internal combustion engine for propulsion.

Regenerative braking in a hybrid electric vehicle (HEV) recovers kinetic energy, which is the energy of motion. When a driver applies the brakes, instead of dissipating this energy as heat through friction in conventional brakes, regenerative braking uses the electric motor as a generator. The electric motor, which normally uses electricity to turn the wheels and propel the car, can be reversed electronically. In this reversed state, the spinning wheels turn the motor, and this mechanical action generates electrical energy. This generated electricity is then stored, typically in a battery or supercapacitor. This stored electrical energy is a direct replenishment of the energy used to accelerate the vehicle previously. The primary benefit is energy recovery: capturing energy that would otherwise be wasted. This recovered energy directly reduces the demand on the internal combustion engine (ICE) for propulsion because the stored electrical energy can be used to power the electric motor, which then assists in or entirely handles vehicle acceleration. When the vehicle needs to move forward, especially at lower speeds or during initial acceleration, the electric motor can draw power from the stored energy, lessening the need for the ICE to provide all the torque. For instance, during a stop-and-go commute, each braking event can capture energy that would have been lost, and this captured energy can then be used to accelerate away from the next stop, meaning the ICE does not have to burn as much fuel to perform that acceleration. Therefore, regenerative braking improves fuel efficiency by reducing the total amount of energy that must be supplied by burning fuel in the ICE.