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Regenerative Braking Systems

Regenerative Braking

Regenerative Braking System is a mechanism that reduces vehicle speed by converting some of its kinetic energy into a storable form of energy instead of dissipating it as heat as with a conventional brake. The captured energy is stored for future use or fed back into a power system for use by other vehicles.

A regenerative brake is an apparatus, a device or system which allows a vehicle to recapture and store part of the kinetic energy that would otherwise be ‘lost’ to heat when braking.

Regenerative brakes are most commonly seen in electric or hybrid vehicles.

Regenerative Braking Systems

Applications of Regenerative Braking

  • First of all regenerative brakes were used in these Trolley cars.
  • Hybrid vehicles like the Toyota Prius
  • Fully electric cars, like the Tesla Roadster
  • Formula One race cars
  • Fast Moving Metro Trains
  • Heavy Trucks

Regenerative Braking Overview

Regenerative braking is used to improve the efficiency (fuel economy) of:

    • Electric  and Hybrid Vehicles
    • F1 Cars
    • High Speed Trains
    • Heavy Trucks
    • Lowers Fuel Consumption and Brake Wear
    • Most effective in stop and go situation

Regenerative Braking

Components of a regenerative braking system

Electric Motor as a Generator

When it runs 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.

Brake Controllers

Brake controllers are electronic devices that can control brakes remotely, deciding when braking begins, ends, and how quickly the brakes need to be applied.

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 to ensure the amount of charge going to the battery.

Braking Energy

  • The energy efficiency of a conventional car = 20% the miraculous thing about regenerative braking is that it may be able to capture as much as half of that wasted energy and put it back to work.
  • Can recover ≈ 3200W  if stopped from 20mph rider.
  • Less energy stored the longer the rider brakes

Braking Efficiency

    • The efficiency from regenerative braking is approximately 75-80% efficient, and the 20% loss is due to friction and other dissipative losses.
    • This could reduce fuel consumption by 10 to 25 percent.
    • These efficiencies are necessary due to the extreme difficulty in finding a place to recharge a hybrid.
    • This makes longer trips difficult without relying on the hybrid’s internal combustion engine, which actually cancels out some of the advantage of owning a hybrid.

Regenerative Braking

Toyoto Regenerative Braking

Successful Implementations of Regenerative Braking System

The Delhi Metro saved around 90,000 tons of carbon dioxide (CO2) from being released into the atmosphere by regenerating 112,500 megawatt hours of electricity through the use of regenerative braking kit systems between 2004 and 2007. It is expected that the Delhi Metro will save over 100,000 tons of CO2 from being emitted per year once its phase II is complete through the use of regenerative braking.

Limitations of Regenerative Brake System

  • The regenerative brake can’t be used where greater power is required for stopping, therefore the friction brake is still required in order to bring the vehicle to a complete halt.
  • The amount of electrical energy capable of dissipation is limited by either the capacity of the supply system to absorb this energy or on the state of charge of the battery or capacitors

Scope of Advancements in Regenerative Braking System

  • Develop electronics to use regeneration and storage of energy.
  • Modified electronic circuits to decide the reversal of motor to generator.
  • Remove its dependence from the friction brakes.

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