REGENERATIVE BRAKING SYSTEM

WHAT IS REGENERATIVE BRAKING SYSTEM?

The technique of recharging the batteries while braking is called Regenerative Braking System.  Regenerative Braking System is used in fully electric vehicles and hybrid electric vehicles that use an electric motor.

HISTORY OF REGENERATIVE BRAKING SYSTEM [1]

  • In 1908, a smart car with Regenerative Braking System was Patented by C.J. Paulson.
  • In 1967 American Motors Cooperation (AMC) in cooperation with Gulton Industries developed the “Energy Regeneration Brake” system.
  • This Energy Regeneration from braking was later commercialized by the Japanese and both Ford and Chevrolet licensed it from Toyota for use in their domestic built hybrid vehicles.
  • During the late 2000s an Electronic Control Unit [ECU] used by BMW that engages the alternator during braking.

WHAT IS THE NEED OF REGENERATIVE BRAKING SYSTEM?

  • Using RBS technique, the fuel economy of vehicles can be improved
  • Reduces greenhouse gas emissions.
  • The increased price of petroleum-based fuels has given way to various research and development in energy conservation.
Normal Driving conditions

In the current world where energy and resource management has become very much important and it’s necessary to employ energy in all the form. Vehicles which are in motion have a lot of kinetic energy and when the brakes are applied all the kinetic energy that was propelling the vehicle forward are lost to the environment as heat which decelerates the car. This useful kinetic energy which could have been used to do some work is wasted as heat.

So, a braking system called Regenerative Braking System [RBS] was introduced, it is an energy recovery mechanism where the kinetic energy is converted into electricity which is used to recharge batteries in Electric Vehicles.

Regenerative action during breaking

Recovering the kinetic energy during braking is called Regenerative Braking System and is used in Electric Vehicles and Hybrid Electric Vehicles [HEV] which make use of an electric motor.

The main components of the Electric Regenerative Braking System are

  • Motor/Generator.
  • Engine.
  • Battery.
  • Electronic Control Unit [ECU].

One of the important properties of an Electric Motor is when it runs in one direction, the electrical energy is converted into mechanical energy which can be used to rotate the wheels of the vehicle. But when the motor runs in the opposite direction, it acts as an electric generator which converts mechanical energy into electrical energy. This electrical energy can be fed into the batteries.

REGENERATIVE BRAKING SYSTEM IN FULLY-ELECTRIC VEHICLE:

Regenerative action in EV

During acceleration, the motor draws the energy from the battery to move the wheels. During braking, the power from the battery is cut off by the controller [ECU] which slows down the motion of the vehicle. Hence the motor performs as a generator and the energy flows back to the battery.

REGENERATIVE BRAKING SYSTEM IN HEV

Regenerative action in HEV

When the driver applies a brake on hybrid electric vehicles, the electric motor generates a negative torque, that is in the reverse direction, which makes the motor act like a generator and thus recovering the energy which is stored in the battery, producing electricity which flows into the batteries.

To gauge the regenerative braking system, its effectiveness and efficiency should be seen. Efficiency states how competently the braking system captures the energy lost when the brake is applied. Effectiveness states how size-able impact(difference) the regenerative braking system actually makes.

BENEFITS OF RBS:

For smaller and personal electric vehicles, the regenerative braking system is not as beneficial or effective as in electric cars, still, it has some multitude of returns.

Regeneration occurs only when the brakes are applied and the resultant energy depends on the speed of the vehicle. By using the Regenerative Braking System, the energy usage efficiency can be increased and also driving distance of Electric Vehicles can be improved. This kind of brakes improves the driving range of Vehicles. All-electric vehicles in motion can utilize this advantage of regeneration to re-collect energy that would have been lost.

Some of the other advantages are the reduction in engine wear out, smaller components, increase the performance, increase in the overall efficiency of vehicles, increases the life span the friction braking system.

Some of the disadvantages are friction brakes are needed to stop the vehicle at low speeds, means energy is still wasted. RBS can increase the overall weight, cost of components, manufacturing and installation are high, maintenance required based on the complexity of the design.

Examples of cars with Regenerative Braking System:

  • Toyota Prius
  • Honda Insight
  • Ford Escape Hybrid
  • Tesla Roadster

References:

  1. https://www.slideshare.net/roskumar18/regenerative-braking-system-37394325
  2. https://auto.howstuffworks.com/auto-parts/brakes/brake-types/regenerative-braking.htm