What is Regenerative Braking? And what problems Regenerative Braking technology are expected to solve? Regenerative Braking is a way of dealing with energy problems, especially when cars brake every small distance as the result of city congestion. Successive braking and acceleration can also reduce fuel efficiency. During braking, a lot of kinetic energy is wasted as heat energy. There are many ways that have been used in an attempt to conserve energy and reuse it, such as Hydraulic Power Assist and Flywheels.

Regenerative Braking is newly implemented in road cars, but its patent was granted in 1902 by Martin Kubierschky of Berlin, Germany (US Patent 714,196: Regenerative system). Regenerative Braking was already used in electrical railways since 1930 and helped reduce CO2 emissions. Regenerative Braking also improves braking components lifespan, as it reduces the wear and tear on each traditional braking component that may be used simultaneously with the Regenerative Braking technology [1].

Regenerative Braking repurposes electric motor in an electric or hybrid car as electric generators. During normal use, the motor will be drawing electricity from the battery. As the brake is depressed, the electric motor reverses this process and send electricity back to the battery, thus recharging it which increases efficiency.

Figure 1. Regenerative Braking Process [2]

Brakes have come a long way, from using drum brakes to disc brakes and even technology such as Anti-lock Braking System which results in an even safer brake. Traditional brakes are safe, but also wasteful            as the underlying principle is to lose kinetic energy by converting it into heat energy or sometimes noise. Regenerative Braking hope to recapture some of the kinetic energy that is else wasted when using traditional brakes[3].

This is not to say that Regenerative Braking will replace traditional brakes, but Regenerative Braking and traditional brakes will both work side by side. Regenerative Braking only works with wheels that are connected to the motor, and thus decreasing its capability to capture in real-wheel or front-wheel only cars. Regenerative Braking also don’t have the same instant brake that traditional brake does, as its efficiency naturally decreases at low speeds as it is limited by the capacity of the battery and the capability of the motor.

Regenerative Braking uses the vehicle’s momentum to put the electrical motor into reverse. Once the motor has been reversed, the electricity then will be fed into the batteries. In some cases, the energy produced by Regenerative braking is stored in a series of high-voltage capacitors for later use. In addition, since vehicles using these kinds of brakes also have a traditional braking system, the braking controller must decide which braking system is appropriate at which time. Because the usage controlled electronically in a regenerative braking system, it's even possible for the driver to select options that determine how the brakes are used for different instances. 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 km/h or will let the car coast slightly[4].

The automotive industry has been developing brake-by-wire systems where many of the functions of brakes that have traditionally been performed mechanically will be performed electronically, thus giving more chance for regenerative brakes to be built side by side with traditional brakes in newer vehicles that implements brake-by-wire. Hybrids and electric cars will probably be early adopters of these brake types with complex circuitry and brake controllers[5].

Brake controllers are electronic devices that can control brakes remotely, deciding when braking begins, ends, and how quickly the brakes need to be applied which can be adjusted at the factory and/or according to each driver’s preference.

In vehicle which Regenerative braking is implemented in conjunction with anti-lock braking systems, 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, thus simplifying the installation if the vehicle did have ABS sensors installed. Negative torque applied to the rear wheels can cause a car to become unstable. Since regenerative braking is a source of negative torque, traction control system can limit regenerative braking if the rear wheels start to slip[6].

The energy output of a conventional car is only about 20 percent, with the remaining 80 percent of its energy lost by being converted to heat through friction. Regenerative braking may be able to capture as much as half of that wasted energy and put it back to work. This could reduce fuel consumption by 10 to 25 percent[7].

Hybrid cars may sometimes be hard to recharge as they will need to be recharged as often or at some instances more due to smaller capacity. Regenerative braking will provide a better solution as to enable the electric part of the hybrid be recharged by the internal combustion engine, thus making hybrid cars requiring less recharging instances and providing the internal combustion engine a way to save its leftover 80 percent energy[8].

Some motors are better suited to doing regen than others. There are hundreds of different types of motors in existence, but only five are commonly used in automotive traction applications: Series DC, Permanent Magnet DC, Separately Excited DC, Permanent Magnet Synchronous, and AC Induction. The Permanent Magnet DC and Separately Excited DC types are both well-suited to regen, but the Separately Excited DC loses its effectiveness due to it being brushed[9].

With all the motors that are available for regenerative braking, surely this technology will become a standard in most of modern cars in time.

 

Kontributor : Michael  (ARE Semester 1 2017/2018)

 

 

References

[1]C. Woodford, "How do regenerative brakes work?", Explain that Stuff, 2017. [Online]. Available: http://www.explainthatstuff.com/how-regenerative-brakes-work.html. [Accessed: 27- Oct- 2017].

[2]C. Lampton, "How Regenerative Braking Works", HowStuffWorks, 2017. [Online]. Available: https://auto.howstuffworks.com/auto-parts/brakes/brake-types/regenerative-braking.htm. [Accessed: 27- Oct- 2017].

[3]J. Laukkonen, "Can Regenerative Braking Recover Lost Energy?", Lifewire, 2017. [Online]. Available: https://www.lifewire.com/can-regenerative-braking-recover-lost-energy-534816. [Accessed: 27- Oct- 2017].

[4]B. Berman, "Regenerative Braking", HybridCars, 2017. [Online]. Available: http://www.hybridcars.com/regenerative-braking. [Accessed: 14- Dec- 2017].

[5]"Information about Brake by Wire Systems", Brakebywire.com, 2017. [Online]. Available: http://www.brakebywire.com/. [Accessed: 14- Dec- 2017].

[6]C. Lampton, "How Regenerative Braking Works", HowStuffWorks, 2017. [Online]. Available: https://auto.howstuffworks.com/auto-parts/brakes/brake-types/regenerative-braking2.htm. [Accessed: 27- Oct- 2017].

[7]C. Lampton, "How Regenerative Braking Works", HowStuffWorks, 2017. [Online]. Available: https://auto.howstuffworks.com/auto-parts/brakes/brake-types/regenerative-braking5.htm. [Accessed: 14- Dec- 2017].

[8]S. Gable, "What is Regenerative Braking in a Hybrid Car?", ThoughtCo, 2017. [Online]. Available: https://www.thoughtco.com/how-does-regenerative-braking-work-85465. [Accessed: 27- Oct- 2017].

[9]J. Jenkins, "Charged EVs | A closer look at regenerative braking", Chargedevs.com, 2017. [Online]. Available: https://chargedevs.com/features/a-closer-look-at-regenerative-braking/. [Accessed: 27- Oct- 2017].