What is Regenerative Braking System and Types ?

Regenerative Braking System is a term that is seen in new vehicles. It is a new technology that enables an electric vehicle's kinetic energy to convert back to electrical power during deceleration or downhill running. The converted electrical energy is stored in devices like batteries, ultracapacitors, and high speed-flywheel to extend the driving range to 10%.

A regenerative braking system is a method to increase the driving range of hybrid electric vehicles by minimizing fuel consumption. Many vehicle manufacturers focus on energy recovery by electric machines as generators, stored in batteries.

Types of Regenerative Braking System

Regenerative Braking System is an energy conversion method by which energy is converted and stored for further uses like extended range and as a generator too.

There are multiple methods of energy conversion in regenerative braking systems including spring, flywheel, electromagnetic and hydraulic. But the most commonly used type is the electromagnetic System.

• Electromagnetic

In this system, the shaft of the vehicle is connected to an electric generator that uses magnetic fields not to rotate the shaft, slowing the vehicle and generating electricity.

In gas-powered vehicles, the electricity is used to power vehicles electronics or sent to the battery for later use in the vehicle.

In electric vehicles or hybrid-electric vehicles, the electricity that is generated is sent to batteries, to recharge.

• Flywheel

In this system, the kinetic energy of the vehicle is collected to spin a flywheel which is connected to the drive shaft through the transmission and gearbox. The spinning flywheel can provide torque to the shaft by giving a power boost to the vehicle.

• Electro-magnetic Flywheel

This is a hybrid model of electromagnetic and flywheel regenerative braking systems which generates power by electromagnetic system methods. The energy is stored in the flywheel then the batteries, the flywheel behaves as a mechanical battery where electrical energy can be stored and recovered. Due to longevity, electric flywheel batteries are the more cost-effective electric storage method.

• Spring

This system is typically/commonly used on human-powered vehicles such as bicycles or wheelchairs where a coil or spring is winded, but during braking the cycle the energy is stored in the form of elastic potential where it can be returned to assist the driver while climbing up the hill or run over through terrain.

• Hydraulic

The hydraulic braking system slows the vehicle by creating/generating electricity which is used to compress the fluid. Nitrogen gas is mostly used as the working fluid. This system has the longest energy storage capability than any other system because the compressed fluid does not dissolve energy over time. Compressing gas with a pump is a slow process and limits the power of the system.

How does Regenerative Braking System Work?

The Regenerative Braking System work principle is increasingly seen in new vehicles and now starting to become more widely available with improved gas efficiency and performance.

When you step on the vehicle's brake, the discs and the brake pads produce friction as they meet each other and create kinetic energy and release heat to the environment.

This system recovers some kinetic energy that turns into heat and converts it to electricity. Here, the motor drives the wheel while accelerating or cruising but the wheel drives the motor while decelerating. The two-way energy flow allows the motor to behave as a generator, counter the rotation of wheels and generate electricity to recharge the battery of the electric vehicle.

There are 2 ways in which regeneration occurs:-

• When the driver applies the brake.

• When the driver releases the accelerator pedal while cruising.

In both ways, the system generates electricity to change the battery. The driver can see the effect on the infotainment system where the energy flow from the wheel is seen.

The amount of electricity generated by the system is proportional to the level of braking force, which means the stronger the braking force, the greater the electric current. The amount of energy that the system has captured is dependent on the speed and duration of the brake applied by the vehicle.

While braking, the system allocates part of the braking force to regenerate energy and the rest of the conventional braking system. In this way, the system achieves two objectives slowing down the car and recharging the battery for better efficiency and greater electric driving range.

What are the Uses of a Regenerative Braking System?

Every year new electric vehicles or hybrid models are increasingly regenerative braking systems with improving amounts of energy. The latest regenerative braking system can recover up to 70% of the kinetic energy or else lost during the braking.

Depending on the owner's driving skills, a regenerative braking system can add up to hundreds of miles of extra range which reduces trip to fuel pump for hybrids and pure electric vehicles to plug in the power grid.

The Advantages and Disadvantages of Regenerative Braking System

• Advantages:-

Hydraulic brakes generally waste energy by turning kinetic energy into heat, whereas regenerative braking gives energy to the vehicle's batteries and provides an extra driving range.

Regenerative Braking System gains recaptured energy which can really add the range liberally and regularly so that electric vehicle drivers know every mile of battery range counts.

The more use of regenerative brakes, the less use of traditional friction brakes which means fewer service center trips. With this system, electric vehicles can go around 100,000 miles between services.

• Disadvantages:-

The most common is effectiveness at a lower speed.

In slow-moving or in day-to-day traffic the system cannot save much energy and resend to the battery.

This braking system may not have the same stopping power as normal brakes, it requires harder on the brake pedal.

How does a Regenerative Braking System Provide Electricity to the Electric Vehicle?

We know that a regenerative braking system turns kinetic energy into electricity and by the reverse process drives the car forward. In an electric car, the battery powers the motor and generate torque to rotational force and then to the wheels. Electrical energy from the battery becomes mechanical energy which rotates the wheels.

By regenerative braking, the energy from the wheels reverses the direction of electricity from the motor to the battery. Removing the foot from the accelerator or applying the brake helps to activate regenerative braking.

The electric motor acts as a generator and also helps to slow the vehicle because energy is consumed by the wheels and rotates the shaft in an electric motor.

FREQUENTLY ASKED QUESTIONS:-

• What motors are used in regenerative brakes?

In a single-stage electric braking system, braking and regeneration are achieved using a single-stage bi-directional DC/AC converter that is used to drive a BLDC motor.

• Who invented the regenerative brake?

In 1886, Sprague Electric Railway & Motor Company,  founded by Frank J. Sprague, came up with two important inventions: a heat-resistant motor with fixed brushes and a moving brake.

• Where are regenerative brakes used?

Adaptive braking is a special system used in electric vehicles to capture the energy that the vehicle has due to its motion or, in other words, its energy that would have been wasted when the vehicle slows down or stops during braking.

• Why is it called regenerative braking?

Regenerative braking is a way to recover lost energy in the process of slowing down the car and use it to recharge the car's battery. In a normal car, braking only dissipates energy - but with regenerative braking, some extra energy can be harnessed.

READ MORE:-

• Why Do Electric Vehicle Batteries Explode?
• What are Electric Power Steering and its Types?
• Internal Combustion To Electric Motor Conversion
• How an Electric Vehicle works?