Kinetic Energy Regenerative Braking System - KERBS

Sanjeev Prasad M1VW11MCE09

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OutlineWhy we need brakes?OverviewTopics related to brakingRegenerative BrakingWorking and ElementsTypes of KERBSStorage of EnergyAdvantages and

LimitationsConclusionReferences 2

Why we need brakes ?We need brakes to reduce the speed of

moving objects or stop them.

Formula 1 cars are capable of decelerating from 124-mph to a standstill in only 2.9 seconds.

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Over viewBrakes translate a push of

a pedal to slowing down your car.

Disc or Drum brakes play the part of the brake system that does the actual work of stopping the car. 

Friction between the various mating surfaces results in braking action and slow down of car. 4

Topics related to brakingPascal’s law

“Pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid such that the pressure ratio (initial difference) remains the same”

Hydraulic Press – basic concept for brakesBraking action

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Brake System Components

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Types of BrakesBasically, purpose of brakes is to apply

mechanical resistance i.e. Friction on rotating wheels in order to slow down the car.

The various methods used to apply friction are :Hydraulic Braking System Electromagnetic SystemPumping brakes

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Regenerative braking• Is an energy recovery mechanism which

slows a vehicle or object down by converting its kinetic energy into another form, which can be either used immediately or stored until needed

• The energy can be stored :• electrically by  battery or capacitors bank• mechanically via pneumatics, hydraulics• kinetic energy in rotating flywheels

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Energy transformationFriction Brake:This brake system converts the kinetic energy of vehicle motion into heat

Regenerative Brake:Capturing kinetic energy generated from braking and converting it to electricity, hydraulic pressure or spring force.

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Elements of the KERBS

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Working of KERBS• Vehicle has forward momentum• Auxiliary systems, like Hydraulic cylinders,

Flywheel apparatus, etc. are coupled to wheels• When brakes are applied, the friction between

braking elements and wheel, engages the regenerative system

• The rotors experience opposing torque, this activates the system :• Hydraulic pump used to pressurize fluid and store

in cylinders• Flywheel used to store as rotary motion• Motor/ Generator used to generate electricity and

store in batteries 11

Types of KERBSHydraulic

Hydrostatic Regenerative Braking (HRB) system uses electrical/electronic Components as well as hydraulics to improve vehicle fuel economy

Flywheel assistedEngines have been using energy-storing devices

called flywheels, which are rotating disc, which are considered as “energy storing reservoirs”

Nitilon Springs assistedSpecial purpose Compression springs are used

to store energy as spring force12

Hydraulic KERBSBraking energy is

converted to hydraulic pressure and stored in a high-pressure hydraulic accumulator

When the vehicle accelerates, the stored hydraulic energy is applied to the transmission, hence reducing the fuel to be combusted in the engine

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Flywheel KERBSPackaged inside a

single housing is a shaft mounted flywheel that is connected via a chain/gear to the drive shaft

During braking and coasting, the flywheel spools-up (accelerates as it spins) and absorbs a storehouse of otherwise wasted energy

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Storage of Kinetic Energy• In a Hydraulic KERBS,

• stored as fluid pressure in hydarulic cylinder.• In Flywheel assisted KERBS,

• stored as rotational energy in flywheel.• In Nitilon spring assisted KERBS,

• stored as spring force or potential energy.• Recent development is that a

Motor/Generator is used to convert kinetic energy to electrical energy.

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Regenerative Braking Controllers•  The brake controller makes the entire

regenerative braking process possible.• its monitors the speed of the wheels•  calculate how much torque -- rotational force

-- is available to be fed back• deciding whether the stored energy should be

released immediately or stored temporarily• Special ECU used for the controlling purpose

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ComparisonHydraulic

KERBS5.55 Wh/kg at 250

Bar pressureEnergy efficiency

at 73%Heavy equipmentsLimited power

storageLeakage of

hydraulic fluid

Flywheel KERBSMaximum power

boost of 60 kW for 6.67 seconds

Compact weight and size

Higher efficiencyLower cost Can be used for

small vehicles also17

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Advantage of regenerative breaking • Improves fuel efficiency• Conservation of Energy• Wear reduction• Higher pick up response• Lower emissions• Kinetic energy regenerated can be stored in

form of electricity in batteries, which can be used to power up other auxiliary systems

• Use of KERBS in hybrid and electric vehicles will increase the travel distance

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- For example:

 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 between 2004 and 2007.

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Limitations of regenerative breakingAdded weight of minimum of 25 kilosThe regenerative braking effect drops off at lower

speedsThe friction brake is a necessary back-up in the

event of failure of the regenerative brake.The amount of electrical energy capable of

dissipation is limited by the capacity of the supply system

Under emergency braking it is desirable that the braking force exerted be the maximum

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New braking system technologies

Anti-Lock Brake System (ABS)Traction Control System (TCS)Electronic Stability Program (ESP)Regenerative braking system

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ConclusionIncreased fuel efficiencyThe lower operating and environment costsAll vehicles in motion can benefit from

utilizing regeneration to recapture energy that would otherwise be lost.

As designers and engineers perfect regenerative braking systems, they will become more and more common

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ReferencesCibulka, J. Kinetic energy recovery system by

means of flywheel energy storage Advanced engineering 3(2009)1, ISSN 1846-5900

www.gm.comwww.howstuffworks.comwww.wikipedia.org

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Questions???

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Thank You…

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