KInetic Energy Recovery System (KERS)

KERS
Kinetic Energy Recovery System
By: Akheel Ahamed
1OX09ME004
Guide: C.V. Raja Reddy
Professor ,
Mechanical Dept
T.O.C.E

KERS - Introduction
• The acronym KERS stands for Kinetic Energy Recovery
System. The device recovers the kinetic energy that is
present in the waste heat created by the car’s braking
process. It stores that energy and converts it into power
that can be called upon to boost acceleration.
• Basically, it’s working principle involves storing the
energy involved with deceleration and using it for
acceleration. That is, when a car breaks, it dissipates a lot
of kinetic energy as heat. The KERS stores this energy and
converts this into power, Upto 80 BHP for 6.67 secs or
400 kj of energy can be stored.

KERS - History
• In development since 90’s . It was first introduced to the
general public through the 2009 series of Formula one
motor sport.
• KERS builders, Flybrid Systems demonstrated a working
Formula One-spec device at the Autosport International
show. (24kg , 400kj energy capacity, power boost-60kw).
• FIA introduced KERS in 2009 GP series to Increase
Overtaking and also as defensive tool to block faster car
• But many F1 teams Opposed it , as it was an Expensive
system, so it was banned in 2010 season
• But with improvements and increase in manufacturers
for KERS it was reintroduced in 2011.

KERS - History
• In the parallel Universe of Stock/Commercial cars many
hybrid manufactures like Honda and Toyota developed
similar, but less powerful system (23 kw) in Civic and
Prius.
• At the 2011North American International Auto Show,
Porsche unveiled a RSR variant of their Porsche 918
concept car which uses a flywheel-based KERS
• A motorcycle racing company called KTM Racing, secretly
tested this kinetic energy system in their vehicle, but they
were banned as that system was illegal and unstable for
motorcycles.

Basic Elements of KERS
In essence a KERS systems is simple, you need a component
for generating the power, one for storing it and another to
control it all. Thus KERS systems have three main
components:
1. The MGU (Motor/Generator Unit)
2. The PCU (Power Control Unit)
3. The batteries/flywheel. (Power Storage Unit)

1. MGU (Motor/Generator Unit):
• Its a single unit which has both motor-generator rotor
coils wound around a single rotor, and both coils share
the same outer field coils working in two modes.
• The MGU both creates the power for the batteries when
the car is braking, then return the power from the
batteries to add power directly to the engine, when the
KERS button is deployed.

2. Power Control Unit ( PCU )
It serves two purposes, to invert & control the switching of
current from the batteries to the MGU and to monitor the
status of the individual cells with the battery.

3. Power Storage Unit (Flywheel/Batteries)
• It stores power for immediate usage and gives power as
and when required. Flywheel used in Mechanical KERS
and Batteries are used in Electrical KERS.

Types of KERS
The KERS can be divided in the way they convert the
energy and how that energy is stored within the vehicle.
Depending on this, KERS has two types:
1. Mechanical Kinetic Energy Recovery System
2. Electrical Kinetic Energy Recovery System

Mechanical KERS
• The concept of transferring the vehicle’s kinetic energy
using flywheel energy storage was postulated by
physicist Richard Feynman in the 1950.
• The mechanical KERS system has a flywheel as the
energy storage device and it does away with MGUs by
replacing them with a transmission to control and
transfer the energy to and from the driveline.

Electrical KERS
• In electrical KERS, braking rotational force is captured by
an electric motor / generator unit (MGU) mounted to
the engines crankshaft.
• This MGU takes the electrical energy that it converts
from kinetic energy and stores it in batteries. The boost
button then summons the electrical energy in the
batteries to power the MGU which in turn powers
boosts the driveline

Advantages of Mechanical KERS
Over Electrical KERS
• In electrical KERS , energy has to be converted twice ,
where as in Mechanical no need of conversion. Hence
electrical energy conversion efficiency is 31- 34 % where
as in mechanical KERS its 70%
• Lithium-ion batteries take 1-2 hours to charge
completely due to low specific power hence not good for
F1 , so they use Super Capacitor.
• Chemical batteries heat up during charging process and
could cause the batteries to lose energy over the cycle or
worse even explode.
• Energy lose in Electrical KERS is more , Whereas not so
much in Mechanical KERS

KERS in Formula One
• KERS was introduced by the International Automobile
Federation (FIA) with a view to increase overtaking
during Formula One Grand Prix races, as the boost
button provides extra power. In effect, the KERS has also
been used to act as a defensive tool to block a faster car,
inhibiting overtaking.
• In the 2009 season KERS was not a huge success, the
system had a FIA cap on the amount of energy that
could be re-used, only 400kJ could be stored, which
when 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 to
improve lap times

KERS in Formula One - Features
• A flywheel made of steel and carbon fibre that rotated at
over 60,000 RPM inside an evacuated chamber. and
casing featured containment to avoid the escape of any
debris.
• The flywheel was connected to the transmission of the
car on the output side of the gearbox via several fixed
ratios, a clutch and a Continuously Variable Transmission
• 80 BHP developed for 6.67 secs per lap reducing the
circuit time by 3 – 4 secs, which can used all at a time or
as and when required 60 kW power transmissions in
either storage or recovery. 400 kJ of usable storage (after
accounting for internal losses).A total system weighs
25kg.

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 braking
system.
• 60 kw is the maximum input and output power of the
KERS system.
• The energy recovery system is functional only when the
car is moving.
• The recovery system must be controlled by the same
electronic control unit.
• If in case the KERS is connected between the differential
and the wheel the torque applied to each wheel must be
same.
• It is very costly. Engineers are trying hard to make it
more cost effective.

Conclusion
• It’s a technology for the present and the future because
it’s environment-friendly, reduces emissions, increases
efficiency and is highly customizable and modifiable.
Adoption of a KERS may permit regenerative braking and
engine downsizing as a means of improving efficiency
and hence reducing fuel consumption and CO2
emissions.
• The KERS have major areas of development in power
density, life, simplicity, effectiveness and first and
foremost the costs of the device. Applications are being
considered for small, mass-production passenger cars, as
well as luxury cars and Trucks.

References
• Presentation on KERS by Harsh Gupta.
• Kinetic Energy Recovery System by means of Flywheel
Energy Storage by Cibulka, J.
• Towards Sustainable Racing by Simon Watkins , RMIT
University.
• Shell Engineering
• Formula One
• Torotrak
• WikiPedia
• http://www.oxbridgewriters.com/essays/engineering/ke
rs.php

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