What is a KERS?

The KERS (Kinetic Energy Recovery System) or Kinetic Energy Recovery System for its acronym in English, is also known as regenerative brake. In the world of competition it became very popular in 2009 as a result of its implementation in the technical regulations of Formula 1, which thus began its path in the direction of hybrid engines.

Today, hybrid technology has reached its peak in the premier class of motorsport with V6 turbo engines that have two types of energy recuperators to form the set called “Power Unit” or “ERS” (Energy Recovery System) .

But the KERS does not only have its application in the competition and not even the races were pioneers in the use of this regenerative braking system, since there was news of a similar system in 1967, when the companies AMC (American Motors Corporation) and Guilton Industries developed it for the Amitron, a three-passenger electric vehicle prototype and only 2,159 mm in length. In addition, this type of technology has its application in many other forms of transport, especially in trains.

Kinetic and electrical energy

We have all heard at some point the phrase: “Energy is neither created nor destroyed, it only transforms.” In essence, this system does the same by being able to convert kinetic energy into electrical energy.

But what is kinetic energy? In physics, this type of energy is the one that a body has a consequence of motion and is defined as the work necessary to accelerate a body of a given mass from rest to the indicated speed. Once the speed is stabilized, said body will maintain its kinetic energy until said speed varies.

On the other hand, electrical energy from a scientific point of view is defined as the existence of a potential difference between two points, which creates an electric current when it comes into contact with an electrical conductor. The good thing about this energy is that it can be transformed into different types of energy: light, thermal or mechanical, so it has multiple practical applications, including those that we are dealing with in this article: those that are capable of moving a vehicle.

How a traditional brake works

Before delving into the operation of the KERS or regenerative brake, let’s remember how a traditional braking system does it. In this case, the brake pads produce friction on the disc (disc brake) or the shoes press the drum (drum brake). In this way, heat energy is generated that is dissipated with the air and is wasted.

Under ideal conditions, the energy required to stop an object is the same as that required to bring it back to the initial speed, although in real life many factors intervene that subtract energy during the process, mainly air resistance, friction of the wheels against the asphalt or the friction of the different mechanical elements of the engine, the suspensions, etc.

But, even with a certain margin of energy loss that is unavoidable, a portion can be harnessed that will reduce effort, fuel consumption and emissions, something that automakers have focused their efforts on for decades.

What is the KERS or regenerative brake

This is where KERS enters the scene, which seeks to reuse part of the energy that is wasted. Thus, once the basic concepts are clear, we can delve into the fundamentals of a system that, in essence, is a device that transforms the kinetic energy that the vehicle has into electrical energy, storing it in capacitors or batteries and using it later to power the different elements of it or even to contribute to its movement or increase its autonomy (electric vehicles). On trains, it directly feeds the power source.

It should be noted that there is a widespread misconception in relation to KERS or any other kinetic energy recovery system: that it recovers the heat energy produced in the brakes when they are actuated.

This is not the case, because what the KERS actually does is take advantage of the moment when the wheels are the ones that promote the movement of the engine and transmission when the driver stops accelerating or braking, since that kinetic energy is not used for force the vehicle forward.

How the KERS or regenerative brake works

To understand how this system works, let’s think of it as an electric motor associated with a battery. This type of thruster can work in two directions. When the current is directed to the electric motor, it makes possible the movement of a coil in the magnetic field, using its energy to move the axis kinetically.As this axis moves, the electricity begins to move in the direction of the battery or the capacitor, recovering the energy.

This process is what we see represented in a basic way on the screen of hybrid vehicles, which tells us when the vehicle uses energy or generates it. In addition, the regenerative brake or KERS allows this energy to be used in auxiliary processes such as heating or air conditioning.

Finally, it is important to point out that the regenerative brake must act together with the traditional brake, since it needs this when the accumulated energy is insufficient to reduce the speed or stop the vehicle. This is due to the fact that it does not act efficiently at low speeds and because its action is limited by the absorption capacity of the system and the batteries.

Why is it called regenerative braking?

Basically, the KERS or regenerative brake allows to reduce the speed of the vehicle, because when acting on the transmission to recover the wasted kinetic energy, it causes a resistance to the advance.

In some cases, especially electric cars, the driver can regulate the holding capacity of the system to simulate the effect of the engine braking of an internal combustion engine. As an example, Hyundai’s cam restraint system allows four modes that offer different levels of interference:

  • Mode 0: the vehicle circulates without any type of retention, so it does not generate energy. The only thing that slows the car in this option is the aerodynamics of the vehicle itself and the friction of the tires in the same way as if you put a gasoline car in neutral driving downhill.
  • Mode 1: it is the option in which less retention is exerted on the motor, producing a small energy to recharge the battery and increasing autonomy. It is very useful on very long and continuous descents where we want to maintain a constant speed.
  • Mode 2: it is the medium level of regeneration, very useful to stop the vehicle gradually in order to face a curve without using the brake pedal.
  • Mode 3: is the strongest level of regeneration, which produces a sudden stop when releasing the accelerator. This mode is very useful to stop the vehicle gradually, selecting it after releasing the accelerator.
    In the case of this system, the driver can select the mode he wants at any time while driving, but it will only work once the accelerator has been released. Some vehicles also have a single pedal system for the accelerator and brake. When the driver steps on the pedal, the car accelerates and, if released, it brakes depending on the intensity with which it is done, thus allowing speed control with a single foot.