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Post on 14-Jun-2015
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IntroductionConventional Breaking SystemRegenerative Breaking & Its WorkingKinetic Energy Recovery System(K.E.R.S)Discharge mode of K. E. R. SBenefits of Regenerative Breaking SystemLimitations of Regenerative Breaking
SystemConclusionReference
What are brakes?A brake is a device that
decelerates a moving object /
prevents an object from
accelerating.
Brakes use friction to convert
kinetic energy into heat
Guiding principle- kinetic energy
increases quadratic ally with
velocity -K = mv2 / 2
When the brake is pushed the
caliper containing piston pushes
the pad towards the brake disc
which slows the wheel down.
Convectional braking system Conventional braking
systems use friction
to counteract the
forward momentum of
a moving car.
As the brake pads rub
against the wheels,
excessive heat energy
is created.
This heat energy
dissipates into the air,
wasting up to 30% of
the car's generated
power
Regenerative braking
Regenerative braking technology funnels the energy created by
the braking process back into the system in the form of charging
the battery for further use
In a regenerative braking system the energy normally lost in the
braking process is transferred to the generator from the rotating
axel and then transferred to the battery, thus saving energy
How does it work
The system that drives the vehicle does the majority of the braking. When
the driver steps on the brake pedal of an electric or hybrid vehicle, these
types of brakes put the vehicle's electric motor into reverse mode, causing it
to run backwards, thus slowing the car's wheels. While running backwards,
the motor also acts as an electric generator, producing electricity that's then
fed into the vehicle's batteries.
Vehicles driven by electric
motors use the motor as a
generator when using
regenerative braking: it is
operated as a generator
during braking and its
output is supplied to an
electrical load; the
transfer of energy to the
load provides the braking
effect.
Many modern hybrid and
electric vehicles use this
technique to extend the
range of the battery pack.
v v
Motor
IC Engine
Generator Battery
Wheel
WheelMotor
Transmission
IC Engine
Generator Battery
Wheel
Wheel
Motor
Transmission
IC Engine
Generator Battery
Wheel
Wheel
Scenario 1: Low speed - Power is provided by electric motor using energy supplied by the DC battery
Scenario 2: Braking – Kinetic energy is converted to electric energy during regenerative braking by electric motor and supplied to battery.
Scenario 3: High speed – Power is provided by IC engine and electric motor via generator. Generator also charge battery during high speed.
Over view
Kinetic energy recovery system
The device recovers the
kinetic energy that is
present in the waste
heat created by the car’s
braking process.
The concept of
transferring the
vehicle’s kinetic energy
using Flywheel energy
storage was postulated
by physicist Richard
Feynman in the 1950s
How does K. E.R. S work
When the driver brakes most of the kinetic energy is still
converted to heat energy but a portion is treated differently
and is stored up in the car.
When the driver presses his boost button that stored
energy is converted back into kinetic energy
The mechanical KERS system utilises flywheel technology
to recover and store a moving vehicle’s kinetic energy
which is otherwise wasted when the vehicle is decelerated.
Flywheel of K. E . R. SMade of steel and carbon
fibre which rotates at over
60,000 RPM.
60 kW power transmission in
either storage or recovery
400 kJ of usable storage
Discharge mode of K. E. R. S
During this stage when the driver pushes the boost button
the flywheel acts as a propulsion motor and discharges the
energy to the wheels
The Flywheel rotor is decelerated during boost discharge
mode and the energy is converted back.
Flywheel acts as a generator and sending energy back to
electric motor, which works as propulsion motor.
Benefits of regenerative braking
Reduction of pollutionIncrease in engine lifeBreaking is not total lossWear Reduction
Reduction in pollutionRailway vehicle – 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 systems
Regenerative brakes have been able to improve the performance of engines.
This has been exhibited in the Motor sport industry –The system used by F! cars
is called K. E. R. S (Kinetic Energy Recovery System)
Increase engine efficiency
Breaking is not total lossConventional brakes apply friction to convert a vehicle’s kinetic energy into heat. In energy terms, therefore, braking is a total loss: once heat is generated, it is very difficult to reuse. The regenerative braking system, however, slows a vehicle down in a different way.
Wear ReductionAn electric drive train also allows for regenerative breaking which increases Efficiency and reduces wear on the vehicle brakes.
Limitations of regenerative braking system The regenerative braking effect drops off at lower speeds,
therefore the friction brake is still required in order to bring
the vehicle to a complete halt.
The friction brake is a necessary back-up in the event of failure
of the regenerative brake.
Most road vehicles with regenerative braking only have power
on some wheels (as in a 2WD car) and regenerative braking
power only applies to such wheels, so in order to provide
controlled braking under difficult conditions (such as in wet
roads) friction based braking is necessary on the other wheels
Conclusion The energy efficiency of a conventional brake is only about 20 percent, with the remaining 80 percent of its energy being converted to heat through friction. 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. This reduces fuel consumption by 10 to 25 percent. Hence regenerative braking plays an important role in fuel consumption and also in the field of speed
Thank you
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