Regenerative Braking

In the event of application of a brake almost always due to friction, energy is lost. If a part of that energy is recovered, it helps in improving fuel economy of a vehicle or of any other machine that consumes petroleum products as fuel, ranging from airplanes to oil drilling rigs. This is the basic concept of Regenerative Braking.

Every timethe car'sbrakes are applied, energy is wasted.Physics tells us that energy is a conserved quantity hence neither it can be created nor it can be destroyed. So,in the event of a car slowing down, the kinetic energy that was associated with its propelling forward will go somewhere. Most of it simply dissipates to the surroundings as heat and becomes useless. That energy, which could have been used to do meaningful work, goes essentially to waste. If a part of that energy can be recovered, it will be a great mileage booster and will help in improving the fuel economy of a vehicle or any machine that consumes petroleum products.

Motorized transportation manufacturers have always had to deal with braking systems. One annoying aspect of friction-based technologies is that all of the kinetic energy leaves the system once the motion has to come to a stop. However, wouldn’t be really practical if we transfer this energy somewhere else?  This is the basic idea behind regenerative braking. Regenerative braking is an energy recovery mechanism that slows down a moving vehicle or object by converting its kinetic energy into a form that can be either used immediately or stored until needed.

Automotive engineers have given this problem a lot of thought and have come up with a kind of braking system that can recapture much of the car's kinetic energy and convert it into electricity, so that it can be used to recharge the car's batteries.

In a regenerative braking system, the motor is run backwards to use the vehicle's momentum as the mechanical energy that puts the motor into reverse. Momentum is the property that keeps the vehicle moving forward once it's been brought up to speed. Once the motor has been reversed, the electricity generated by the motor is fed back into the batteries, where it can be used to accelerate the car again after it stops. Sophisticated electronic circuitry is necessary to decide when the motor should reverse, while specialized electric circuits route the electricity generated by the motor into the vehicle's batteries. In some cases, the energy produced by these types of brakes is stored in a series of capacitors for later use. In addition, since vehicles using these kinds of brakes also have a standard friction braking system, the vehicle's electronics must decide which braking system is appropriate at which time. Because so much is controlled electronically in a regenerative braking system, it's even possible for the driver to select certain presets that determine how the vehicle reacts in different situations. For instance, in some vehicles a driver can select whether regenerative braking should begin immediately whenever the driver's foot comes off the accelerator pedal and whether the braking system will take the car all the way to 0 mph (0 kilometers per hour) or will let the car coast slightly.

Regenerative braking is used in vehicles that make use of electric motors, primarily fully electric vehicles and hybrid electric vehicles. One of the more interesting properties of an electric motor is that, when it's run in one direction, it converts electrical energy into mechanical energy that can be used to perform work (such as turning the wheels of a car), but when the motor is run in the opposite direction, a properly designed motor becomes an electric generator, converting mechanical energy into electrical energy. This electrical energy can then be fed into a charging system for the car's batteries. Trolley cars were among the first vehicles to use regenerative braking technology.

In automobile systems, an AC motor is used to transfer energy from the car’s battery into the motion of the wheels. However, once the brakes are activated, the motion of the car’s wheel will reverse. This effectively transform the systems from a motor into a generator, with the new motion causing the current  flow in the opposite direction, therefore charging the battery! Even with an efficiency of only around 20%, the extra energy can be used to allow hybrid engines to have better mileage or allow electric cars to go farther

Regenerative braking systems are controlled by regenerative braking controllers. The regenerative braking controllers monitor how fast the vehicle is moving and how much torque is able to generate electricity to be fed back into the batteries. This information allows the controller to decide  if the speed is too high for the regenerative braking system to handle in which case the old-fashioned friction braking system will take over.

Regenerative braking is implemented in conjunction with anti-lock braking systems (ABS), so the regenerative braking controller is similar to an ABS controller, which monitors the rotational speed of the wheels and the difference in that speed from one wheel to another. In vehicles that use these kinds of brakes, the brake controller not only monitors the speed of the wheels, but it can calculate how much torque -- rotational force -- is available to generate electricity to be fed back into the batteries. During the braking operation, the brake controller directs the electricity produced by the motor into the batteries or capacitors. It makes sure that an optimal amount of power is received by the batteries, but also ensures that the inflow of electricity isn't more than the batteries can handle.

The most important function of the brake controller, however, may be deciding whether the motor is currently capable of handling the force necessary for stopping the car. If it isn't, the brake controller turns the job over to the friction brakes, averting possible catastrophe. In vehicles that use these types of brakes, as much as any other piece of electronics on board a hybrid or electric car, the brake controller makes the entire regenerative braking process possible.

There's a general movement in the automotive industry toward so-called brake-by-wire systems where many of the functions of brakes that have traditionally been performed mechanically will be performed electronically. Hybrids and electric cars will probably be early adopters of these brake types. At present, different automotive engineers have come up with differing circuit designs to handle the complexities of regenerative braking; however, in all cases, the single most important part of the braking circuitry is the braking controller.

In summation, regenerative breaking is an ingenious technology that uses creative ways to recover power. In fact, these machines have been found powerful enough to convince companies and organizations such as Tesla and the New Delhi metro to implement them in their products!