KERSKinetic Energy Recovery SystemBy: Akheel Ahamed1OX09ME004Guide: C.V. Raja ReddyProfessor ,Mechanical DeptT.O.C.E
KERS - Introduction• The acronym KERS stands for Kinetic Energy RecoverySystem. The device recovers the kinetic energy that ispresent in the waste heat created by the car’s brakingprocess. It stores that energy and converts it into powerthat can be called upon to boost acceleration.• Basically, it’s working principle involves storing theenergy involved with deceleration and using it foracceleration. That is, when a car breaks, it dissipates a lotof kinetic energy as heat. The KERS stores this energy andconverts this into power, Upto 80 BHP for 6.67 secs or400 kj of energy can be stored.
KERS - History• In development since 90’s . It was first introduced to thegeneral public through the 2009 series of Formula onemotor sport.• KERS builders, Flybrid Systems demonstrated a workingFormula One-spec device at the Autosport Internationalshow. (24kg , 400kj energy capacity, power boost-60kw).• FIA introduced KERS in 2009 GP series to IncreaseOvertaking and also as defensive tool to block faster car• But many F1 teams Opposed it , as it was an Expensivesystem, so it was banned in 2010 season• But with improvements and increase in manufacturersfor KERS it was reintroduced in 2011.
KERS - History• In the parallel Universe of Stock/Commercial cars manyhybrid manufactures like Honda and Toyota developedsimilar, but less powerful system (23 kw) in Civic andPrius.• At the 2011North American International Auto Show,Porsche unveiled a RSR variant of their Porsche 918concept car which uses a flywheel-based KERS• A motorcycle racing company called KTM Racing, secretlytested this kinetic energy system in their vehicle, but theywere banned as that system was illegal and unstable formotorcycles.
Basic Elements of KERSIn essence a KERS systems is simple, you need a componentfor generating the power, one for storing it and another tocontrol it all. Thus KERS systems have three maincomponents:1. The MGU (Motor/Generator Unit)2. The PCU (Power Control Unit)3. The batteries/flywheel. (Power Storage Unit)
Basic Elements of KERS1. MGU (Motor/Generator Unit):• Its a single unit which has both motor-generator rotorcoils wound around a single rotor, and both coils sharethe same outer field coils working in two modes.• The MGU both creates the power for the batteries whenthe car is braking, then return the power from thebatteries to add power directly to the engine, when theKERS button is deployed.
Basic Elements of KERS2. Power Control Unit ( PCU )It serves two purposes, to invert & control the switching ofcurrent from the batteries to the MGU and to monitor thestatus of the individual cells with the battery.
Basic Elements of KERS3. Power Storage Unit (Flywheel/Batteries)• It stores power for immediate usage and gives power asand when required. Flywheel used in Mechanical KERSand Batteries are used in Electrical KERS.
Types of KERSThe KERS can be divided in the way they convert theenergy and how that energy is stored within the vehicle.Depending on this, KERS has two types:1. Mechanical Kinetic Energy Recovery System2. Electrical Kinetic Energy Recovery System
Mechanical KERS• The concept of transferring the vehicle’s kinetic energyusing flywheel energy storage was postulated byphysicist Richard Feynman in the 1950.• The mechanical KERS system has a flywheel as theenergy storage device and it does away with MGUs byreplacing them with a transmission to control andtransfer the energy to and from the driveline.
Electrical KERS• In electrical KERS, braking rotational force is captured byan electric motor / generator unit (MGU) mounted tothe engines crankshaft.• This MGU takes the electrical energy that it convertsfrom kinetic energy and stores it in batteries. The boostbutton then summons the electrical energy in thebatteries to power the MGU which in turn powersboosts the driveline
Advantages of Mechanical KERSOver Electrical KERS• In electrical KERS , energy has to be converted twice ,where as in Mechanical no need of conversion. Henceelectrical energy conversion efficiency is 31- 34 % whereas in mechanical KERS its 70%• Lithium-ion batteries take 1-2 hours to chargecompletely due to low specific power hence not good forF1 , so they use Super Capacitor.• Chemical batteries heat up during charging process andcould cause the batteries to lose energy over the cycle orworse even explode.• Energy lose in Electrical KERS is more , Whereas not somuch in Mechanical KERS
KERS in Formula One• KERS was introduced by the International AutomobileFederation (FIA) with a view to increase overtakingduring Formula One Grand Prix races, as the boostbutton provides extra power. In effect, the KERS has alsobeen used to act as a defensive tool to block a faster car,inhibiting overtaking.• In the 2009 season KERS was not a huge success, thesystem had a FIA cap on the amount of energy thatcould be re-used, only 400kJ could be stored, whichwhen used for 6.7s per lap, the car gained some 80hp.Thus although a 0.3s boost to lap times was achieved,the system was ultimately limited in its potential toimprove lap times
KERS in Formula One - Features• A flywheel made of steel and carbon fibre that rotated atover 60,000 RPM inside an evacuated chamber. andcasing featured containment to avoid the escape of anydebris.• The flywheel was connected to the transmission of thecar on the output side of the gearbox via several fixedratios, a clutch and a Continuously Variable Transmission• 80 BHP developed for 6.67 secs per lap reducing thecircuit time by 3 – 4 secs, which can used all at a time oras and when required 60 kW power transmissions ineither storage or recovery. 400 kJ of usable storage (afteraccounting for internal losses).A total system weighs25kg.
KERS in Road Cars• Transport Buses in Sverdon, Switzerland (1950)• Honda Civic Hybrid(2002)• Ford Escape Hybrid(2005)• Jaguar XF sedan (Prototype)• Porsche 918 RSR variant concept car (2011)
Advantages of KERS• Reduced CO2 Emissions/Pollutants• Enhanced Performance• Environmentally Sound• High power capability• Light weight and small size with Long system life• Completely Safe and a Truly Green Solution• High efficiency Storage and Recovery
Limitations of KERS• Only one KERS for car which has only one brakingsystem.• 60 kw is the maximum input and output power of theKERS system.• The energy recovery system is functional only when thecar is moving.• The recovery system must be controlled by the sameelectronic control unit.• If in case the KERS is connected between the differentialand the wheel the torque applied to each wheel must besame.• It is very costly. Engineers are trying hard to make itmore cost effective.
Conclusion• It’s a technology for the present and the future becauseit’s environment-friendly, reduces emissions, increasesefficiency and is highly customizable and modifiable.Adoption of a KERS may permit regenerative braking andengine downsizing as a means of improving efficiencyand hence reducing fuel consumption and CO2emissions.• The KERS have major areas of development in powerdensity, life, simplicity, effectiveness and first andforemost the costs of the device. Applications are beingconsidered for small, mass-production passenger cars, aswell as luxury cars and Trucks.
References• Presentation on KERS by Harsh Gupta.• Kinetic Energy Recovery System by means of FlywheelEnergy Storage by Cibulka, J.• Towards Sustainable Racing by Simon Watkins , RMITUniversity.• Shell Engineering• Formula One• Torotrak• WikiPedia• http://www.oxbridgewriters.com/essays/engineering/kers.php