What is Regenerative braking system in Electric vehicles
It is a type of braking method by which the mechanical energy from the load is converted into electrical energy and it is regenerated back into the line is known as regenerative braking the motor operates as a generator
- It is the way of slowing a vehicle by using the motor as a brake
- In case of normal braking the energy is wasted, but in this case the motor act as a generator and returns some of it to the overhead wires as electricity
- Vehicle is primarily powered from the electrical energy generated by the generator, which burns gasoline
- Energy is stored in a battery and it is used by an electric motor that provides motive force to the wheels
- In regenerative braking a good amount of kinetic energy is used to charge the battery using the same principle as an alternator
In this braking method, the kinetic energy is converted into electrical energy which could be used immediately or it can be stored and use when it is needed. The electricity generated during the braking is fed back into the supply system but in case of hybrid electric vehicles the energy is stored in a battery or bank of a capacitor to use later
Need for Regenerative braking system
During city traffic at low speed stop and go traffic where little deceleration is needed. Regenerative braking can provide the majority of the total braking force and it will highly improve the fuel economy. The regenerative braking system has provided better fuel economy at a higher speed too.
Basic Elements of the system
Major four elements which are needed for the Regenerative braking system
- Energy storage unit (ESU)
- Continuously variable transmission (CVT)
- Controller
- Regenerative brake controller
Energy storage unit
It has two important function
- To recover and store braking energy
- Excess engine energy will be absorbed during a light load operation
How to select effective energy storage
- High energy transfer rate
- Small space requirement
- High storage density
The devices which can be used to store the regenerative energy
- Electrochemical battery
- Flywheel
- Compressed air
Batteries
The kinetic energy of the car is used to generate electricity which is then used to recharge batteries and with the regenerative braking traditional braking is also used to make sure the car has better-stopping power, so not all of the kinetic energy can be converted some of it is lost and another loss is due to resistance as the energy travels from wheel to axle
When the brake pedal is depressed the battery will receive charge which will slow down the vehicle quickly if we apply the brake further then the conventional brake is applied the motor/generator produces AC it would be converted to DC which is used to charge the battery
Flywheel
In the flywheel the translational energy of the vehicle is transferred into rotational energy, the advantage of using this technology is that more of the forward inertial energy of the car can be captured than in batteries because it can use energy at short intervals of braking and acceleration which is not possible by batteries
Continuously variable transmission (CVT)
Storage unit requires a transmission which can handle both torque and speed demands in a steeples manner and it could control the energy flow to and from the vehicle wheels
Controller
The ON-OFF engine control system is used which means that the engine is on until the energy storage device is charged and decoupled, it will stop when the energy storage unit charge falls below its minimum requirement
Brake controllers
Brake controllers are used to controlling brakes remotely while the braking operation takes place the brake controllers directs the produced electricity by the motor to batteries or capacitor
The major role of the brake controller is to decide if the motor is capable to produce the force needed to stop the car if not then the conventional brake is used
Advantages of Regenerative braking over conventional braking
- Energy conservation
- Wear reduction
- Low fuel consumption
- Braking is not a total loss
- Driver safety is enhanced