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KINETIC ENERGY RECOVERY SYSTEM

FOR F1 CARS

ABSTRACT:

This paper deals with the design of Kinetic Energy

Recovery Systems (KERS) by means of Flywheel

Energy Storages (FES).Kinetic Energy Recovery

Systems or KERS works on the basic principle of

physics that states, Energy cannot be created or

destroyed, but it can be endlessly converted.

REGENERATIVE BRAKING:

A regenerative brake is a mechanism that reduces

vehicle speed by converting some of its kinetic energyinto another useful form of energy - electric current,compressed air.This captured energy is then stored for

future use or fed back into a power system for use by

other vehicles. For example, electrical regenerative

brakes in electric railway vehicles feed the generatedelectricity back into the supply system .In battery

electric and hybrid electric vehicles, the energy is

stored in a battery or bank of twin layer capacitors forlater use. Other forms of energy storage which may beused include compressed air and flywheels.

Regenerative braking utilizes the fact that an electric

motor can also act as a generator. The vehicle's

electric traction motor is operated as a generatorduring braking and its output is supplied to an

electrical load . It is the transfer of energy to the load

which provides the braking effect.

TYPES OF KERS:

(i) ELECTORNIC KERS :

The key challenge faced by this type of KERS systemis that the lithium ion battery gets hot and therefore an

additional ducting is required in the car. BMW has

used super-capacitors instead of batteries to keep the

system cool.

With this system when brake is applied to the car asmall portion of the rotational force or the kinetic

energy is captured by the electric motor mounted at

one end of the engine crankshaft. The key function ofthe electric motor is to charge the batteries under

barking and releasing the same energy on acceleration.

This electric motor then converts the kinetic energy

into electrical energy that is further stored in the highvoltage batteries. When the driver presses the

accelerator electric energy stored in the batteries is

used to drive the car.

(ii) MECHANICAL KERS :

The system is completely based on a carbon

flywheel in a vacuum that is linked through a CVTtransmission to the differential. With this a huge

storage reservoir is able to store the mechanical energy

and the system holds the advantage of beingindependent of the gearbox. The braking energy isused to turn the flywheel and when more energy is

required the wheels of the car are coupled up to the

spinning flywheel. This gives a boost in power andimproves racing performance. The system consists of

a flywheel connected by a continuously variable

transmission (CVT) to the drivetrain. Moving the CVTtowards a gear ratio that would speed the flywheel upenables it to store energy, while moving towards a

ratio that would slow it down allows it to release

energy. A hydraulic clutch separates the drive if the

flywheels revs exceed the systems limits.

FLYWHEEL ENERGY STORAGE:

Kinetic storages, also known as Flywheel Energy

Storages (FES), are used in many technical fields.While using this technical approach, inertial mass is

accelerating to a very high rotational speed andmaintaining the energy in the system as rotational

energy. The energy is converted back by slowing

down the flywheel. Available performance comes f

rom moment of inertia effect and operating rotationalspeed. Flywheel mass is either mechanically driven

by CVT (Continuously Variable Transmission) gear

unit or electrically driven via electric motor /

generator.

.

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BASIC PRINCIPLES

Stored Energy

Basic principle of kinetic energy storage is madeby rotational energy. While using thiStechnical

approach, inertial mass is accelerating to a very high

rotational speed and maintaining the energy in the

system as rotational energy. Stored energy isproportional to inertia of rotor and is a quadratic

function of revolution speed:

ENERGY STORAGE MODE:

Car is decelerating during recuperative charge mode.

Electric motor works as generator and sending energy

to flywheel storage.

Flywheel rotor is accelerated in recuperative charge

mode.

ENERGY RELEASE MODE:

The acceleration is getting boosted in this mode.

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.

KERS boost simulation - Discharge generator boostmode.

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POTENTIAL IMPACT OF KERS :

Racing with Kinetic Energy Recovery System, a best

case from some basic assumptions :- perfect recovery system- no limitation on torque applied by KERS

during braking

- no limitation on electric motor duty cycle- car speed profile supposed to be same w / wo

KERS- fuel saving proportional to the energy which

has been recovered by KERS, fully independent of the

thermal engine.Realistic assumptions would probablylead to 50 to 60 % of expected fuel savings.

ADVANTAGES:In comparison with other battery storage technologies,

KERS offers:

Cycle durability 90% efficiency of flywheel

(including power electronics) in both directions during

KERS reference duty cycle.

Extensive operating temperature range.

Steady voltage and power level which isindependent of load, temperature and state of charge.

High efficiency at whole working speed range.

No chemistry included, thus no environmentalpollution and great recycling capability.

DISADVANTAGES:

The drawback with Mechanical KERS is that theflywheel will be spinning at high rate and there is a

danger of the flywheel affecting the driver if it

disintegrates and is not properly shielded.

LIMITATIONS OF KERS:

Though KERS is one of the most significant

introductions for Formula One it has some limitationswhen it comes to performance and efficiency.

Following are some of the primary limitations of theKERS:

60 kw is the maximum input and outputpower of the KERS system.

The maximum energy released from theKERS in one lap should not exceed 400 kg.

Energy released from the KERS must remainunder complete control of the driver.

The recovery system must be controlled bythe same electronic control unit that is used

for controlling the engine, transmission,

clutch, and differential.

The energy recovery system must connect atone point in the rear wheel drivetrain.

If in case the KERS is connected between thedifferential and the wheel the torque appliedto each wheel must be same.

KERS can only work in cars that areequipped with only one braking system.

CONCLUSION:

- a perfect 60 kW Kinetic Energy RecoverySystem, with 100 % efficiency, wouldrecover < 3 % of the energy provided by acurrent F1 engine in the same conditions

- for the same lap time, a perfect 60 kWKinetic Energy Recovery System, with noenergy storage limitation, would provide less

than 3 % of fuel consumption improvement

on a current F1 car.

- real world situation, with real world 60kW KERS (not a perfect system), would

provide less than 15 % fuel consumption

improvement with same ICE engine for thesame lap time.

REFERNCE : Cibulka, J. KINETICENERGY RECOVERY SYSTEMBY MEANS

OF FLYWHEEL ENERGY STORAGE.

ADVANCED ENGINEERING 3(2009)1, ISSN

1846-5900

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