Conference Session
2124
INTEGRATING FLYWHEEL-BASED KINETIC ENERGY RECOVERY
SYSTEMS IN HYBRID VEHICLES
Nathan Harlow (njh35@pitt.edu), Robert Scott Johnson (rsj6@pitt.edu)
Abstract– A concern with current hybrid electric vehicles is
low efficiency. There are multiple ways of conserving the
energy of a vehicle to improve efficiency. This paper will
examine and evaluate the use of flywheel technology as an
effective means of conserving energy in hybrid vehicles.
First, the paper will explain, in detail, the engineering and
mechanics of the flywheel, and will clarify how flywheel
energy storage works and how it can be applied to hybrid
vehicles. The significance and efficacy of using flywheels in
hybrid vehicles will be evaluated. It will then cover the
history behind the development of this technology. The paper
will briefly assess current methods of recovering otherwise
wasted energy and their shortcomings. Each component of
the flywheel-based kinetic energy recovery system will be
described in detail. Next, the advantages and disadvantages
of using flywheel energy storage as opposed to other energy
storage systems will be discussed. The paper will address
the safety concerns of using this system and also talk about
the environmental impacts. Finally, it will conclude with an
explanation of the importance of flywheel technology and an
analysis of its outlook.
the vehicle. This is accomplished by using a flywheel. A
flywheel is a mechanical device that can be used to store
rotational energy. Flywheels are generally large metal discs
that are accelerated to high rotational speeds. The amount of
energy that flywheels are able to store is dependent upon the
weight of the flywheel and how fast it is rotating.ed
KEEPING IT KINETIC
The ability of flywheels to store energy is explained by the
principles of inertia, angular velocity, and kinetic energy.
The equation for the energy (1) stored in a flywheel reads as
follows:
1
𝐸 = 𝐼𝜔2
2
(1) [1]
Where 𝐸 is energy (Joules), 𝐼 is the inertia of the
flywheel (kgm2), and 𝜔 is the angular velocity (rad/sec) of
the flywheel. The equation for the inertia (2) of a flywheel
is:
1
𝐼 = 𝑚(𝑟12 − 𝑟22 )
2
Key Words—conservation of energy, energy storage,
flywheel, hybrid, kinetic energy recovery system
(2) [1]
Where 𝐼 is inertia (kgm2), m is mass (kg), and r1 and r2
are the outer and inner radii (meters), respectively. An
important thing to note about the energy equation is the
relationship between inertia and angular velocity. If the
inertia is doubled, the energy stored is also doubled. If the
angular velocity is doubled, then the energy stored is four
times the original amount. This shows that the angular
velocity of the flywheel has a much greater effect on the
energy of the flywheel than the inertia. With this in mind, it
is more important to maximize the velocity of the flywheel
rather than increasing its mass in order to achieve greater
energy storage.
The materials of the flywheel play a big role in
determining the efficiency of the system. In the past,
flywheels were often made of heavy materials such as steel.
Since the angular velocity affects the energy of the flywheel
more than the mass, it makes sense to decrease the mass,
because any excess mass increases the weight of the vehicle,
requiring more energy to move it, resulting in lower
efficiency. Also, with the flywheel rotating at speeds
exceeding 60,000 rpm, the material needs to be very strong
and durable. For these reasons, flywheels are made of a
carbon fiber filament wound rim that surrounds a steel hub
[1]. The following is a list of system specifications for the
kinetic energy recovery system that has been used in
Formula 1 cars:
A NEW SPIN ON HYBRIDS
Today’s society increasingly depends upon technology and
energy use. Much of our energy is consumed in the form of
transportation and relies heavily upon fossil fuels which are
limited resources that can damage the environment. In the
past decade, a big push has been made to develop efficient
hybrid vehicles to reduce energy consumption, as well as
promote sustainable living. There are several ways of
conserving energy in vehicles and the aim of each way is to
increase the overall efficiency while remaining economical,
practical, and safe.
Currently, the market for hybrid vehicles is largely
comprised of hybrid electric vehicles. These vehicles are
partially or fully powered by electric motors that are
supplied electricity from rechargeable batteries. The
technology that they are built upon is not yet fully developed
and cannot operate to the efficiency that it needs to. While
hybrid electric vehicles lead the market, there continues to
be development in alternative, more efficient hybrid vehicle
technology.
An emerging technology in “green” transportation is the
flywheel-based kinetic energy recovery system. This system
focuses on recovering the energy normally lost during
braking and stores it to be used to assist the acceleration of
University of Pittsburgh
Swanson School of Engineering
February 10, 2012
1
Nathan Harlow
Robert Scott Johnson
 Power 60kW
 System Weight 25 kg
 Flywheel Weight 5 kg
 CVT Weight 5 kg
 Flywheel Diameter 200 mm
 Flywheel Length 100 mm
 Efficiency >70% round trip
 Flywheel Max Speed 64,500 rpm
The total weight of the system is insignificant compared
to the total weight of the vehicle, so the fuel efficiency of the
vehicle is unaffected. A heavier vehicle requires more power
to get going, but the weight of the system does not increase
much with the weight of the vehicle. The flywheel is located
in the rear of the vehicle near the center so that it does not
throw off the balance of the vehicle. It is also small enough
that the gyroscopic forces caused by its rotation do not affect
the vehicle’s handling.
There are some forces that work against the rotation of
the flywheel, such as friction and air resistance. These forces
can pose a problem for the overall efficiency of the system.
To reduce these effects, the flywheel rotates using magnetic
bearings which suspend the axle that the flywheel rotates
around. The flywheel is also put in a vacuum sealed chamber
to eliminate air resistance. A vacuum pump is attached to the
chamber to remove any air that leaks in where the axle exits
the chamber. This information will be expanded upon later
in the paper.
using the electric motor to rotate it to up to 3,000 revolutions
per minute. While this is a relatively low speed compared to
modern day flywheels, it was still able to store a lot of
energy because of its size. The process of charging the bus
took anywhere from 30 seconds to three minutes. The
electric motor was then used as a generator. Powered by the
energy stored in the flywheel, it delivered power to the
wheels and allowed the Gyrobus to travel three to six miles
at 30 to 40 miles per hour. There were obvious problems
with the Gyrobus including the material, weight, and
efficiency. Because the flywheel was made out of steel it
had a large weight and was limited to low speeds. It also
used conventional bearings that created friction and often
broke because of the weight of the flywheel [3].
Since the time of the Gyrobus, flywheel technology has
advanced greatly due to the availability of carbon fiber. As
mentioned before, this allows the flywheels to be smaller
and lightweight making them better suited for vehicles. The
first high-tech flywheels were developed and tested in
Formula 1 cars as a way of recovering energy. This
increased the performance of the cars and gave them a small
boost coming out of turns [4]. Although they have not
reached consumer or public transit vehicles there are several
companies that have been testing and producing systems for
these applications. One of the main leaders in flywheel
technology is Flybrid Systems. They currently develop
KERS for commercial vehicle use. Volvo has been testing a
carbon fiber flywheel-based KERS that they are hoping to
release in the next few years. They claim that it can reduce
fuel consumption up to 20% and offer an extra 80
horsepower during initial acceleration [5].
Advancement of Flywheel Energy Storage
The use of flywheels to store energy is an old process. They
have been used in many things before such as potter’s
wheels, steam engines, manual transmissions, and any pullstart motor. Flywheels have also been used as an option of
managing the power in the electric grid. The supply of
power is not always constant. For example, the use of wind
turbines and solar panels produces power that is not constant
because there is not always wind and the sun is not always
shining. Large batteries have been used in an attempt to
solve this problem but they are made of harmful, expensive
materials. Flywheels are a cheaper alternative to stabilizing
the power grid. They are able to store the energy produced
and can be discharged of that energy at a later time. Beacon,
a company that provides products and services for the
electrical power grid, has opened a flywheel energy storage
plant in Stephentown, New York, that consists of 200
flywheels. This plant can respond to the electrical grid in
four seconds [2].
First attempts to apply these energy storage abilities in
vehicles have been in buses and trains. During the 1950’s in
Switzerland, Zaire, and Belgium, flywheel technology was
incorporated into a vehicle known as the Gyrobus. It was a
passenger bus that carried a three ton rotating steel wheel
that was attached to an electric motor. While the Gyrobus
was at the station, energy would be stored in the flywheel by
Flywheels in Hybrid Vehicles
A kinetic energy recovery system (KERS) is a technology
that requires two things. It requires a method of recovering
and storing the energy of a vehicle and a medium to store
this energy in [1]. The majority of hybrids on the market are
electric hybrids. These vehicles use the electrical approach
to recovering and storing energy. First, the kinetic energy of
the vehicle is transformed into electrical energy via the
electric motor. Then, the electrical energy is converted to
chemical energy and stored in a battery. Finally, the
chemical energy is then converted back into electrical
energy which is used by the motor to create kinetic energy
once again. Each of these steps has losses of energy making
the use of an electrical KERS inefficient [6]. The other
approach to recovering and storing the kinetic energy of a
vehicle is a mechanical approach. The two main methods of
recovering energy mechanically are through the use of
hydraulic pressure and the use of a flywheel.
Recovering energy via hydraulic pressure requires three
main components. The system must have a small dieselmotor powered pump, a hydraulic motor, and an
accumulator. The pump stores energy in the accumulator by
2
Nathan Harlow
Robert Scott Johnson
forcing hydraulic fluid into it, creating pressures of up to 385
kg/cm2. The hydraulic pressure is then released to power the
hydraulic motor when the accelerator is pressed [7].
The mechanical hybrid consists of a rotating flywheel,
continuously variable transmission (CVT), and a connection
to the driveline. With a flywheel-based KERS, the kinetic
energy of the vehicle is directly stored as the kinetic energy
of the flywheel through a series of gears and the CVT. This
decreases the speed of the vehicle and increases the speed of
the flywheel. When the vehicle is ready to accelerate, the
process is reversed and the energy is returned to the vehicle,
increasing the vehicle speed and decreasing the flywheel
speed. Thus, the kinetic energy stored in the flywheel is
inversely related to the kinetic energy of the vehicle. This
change in the ratio of speeds is accomplished through the
use of a Toroidal CVT.
The two rollers that are in the middle of the diagrams
transmit power from the vehicle to the flywheel. They are
rotated to contact the discs in different areas, adjusting the
ratio of vehicle speed to flywheel speed, and are free to spin
against the input and output discs [9]. Because of the
friction created by metal to metal contact, an
elastohydrodynamic traction fluid is used to eliminate this
contact but still allows the discs and rollers to have traction
[1]. When the flywheel is not in use or when the vehicle
comes to a complete stop, a clutch enables the
disengagement of the flywheel from the rest of the system.
The clutch also disengages when the ratio of input power to
output power is too large or too small [6].
As mentioned before, flywheels experience losses in
energy storage due to the friction created by the rotation of
an axle and the surrounding air. For a flywheel-based KERS
to be safe and efficient in hybrid vehicles it is necessary to
eliminate as much of this friction as possible. To do this, the
flywheel must rotate on magnetic bearings as opposed to
conventional ball bearings.
TOROIDAL CVT
CVT’s are necessary in KERS because the ratio between
vehicle speed and flywheel speed changes during braking
and acceleration [6]. As the vehicle slows, the Toroidal
CVT must continuously adjust the ratio between the speed of
the vehicle and the rotation of the flywheel. As opposed to
traditional transmissions that utilize planetary gears to adjust
the ratio, Toroidal CVT’s use a series of discs and rollers to
vary the output to either the flywheel or the vehicle [1]. A
similar method to the toroidal CVT is a pulley-based CVT. It
contains two variable-diameter pulleys, connected by a high
power belt, that can be adjusted to change the input-output
ratio between the car and the flywheel. This produces the
same effect of a toroidal CVT [8]. The illustrations below
demonstrate how the positions of the rollers affect the output
on either side of the CVT.
MAGNETIC BEARINGS
In contrast with conventional bearings that use balls to
reduce
rotational
friction,
magnetic
bearings
electromagnetically suspend a shaft eliminating contact
between the shaft and the bearing. Systems that use
magnetic bearings typically have two radial bearings and a
thrust bearing. The radial bearings consist of two main
parts. They have a stationary component called the stator
and a rotating component called the rotor. The stator is
comprised of a buildup of laminations shaped with poles.
The poles are then wound with coils of wire and an electric
current is passed through the coils to produce an attractive
force on the rotor which fits over the shaft.
FIGURE 2
PICTURE SHOWING THE DESIGN OF A MAGNETIC BEARING [10]
Thrust bearings allow the movement of the axle to be
controlled using electromagnetic forces. A thrust bearing in
combination with two radial bearings allows control of the
axle along five axes [10].
FIGURE 1
ILLUSTRATION OF VARIOUS POSITIONS OF THE TOROIDAL CVT AND THEIR
OUTCOME [9]
3
Nathan Harlow
Robert Scott Johnson
Magnetic bearings offer many advantages to a flywheelbased KERS that could be used in hybrid vehicles. Because
of the air gap created by the levitation, friction between the
shaft and the bearing is eliminated. This increases the ability
of the flywheel to store energy. Other advantages include a
life-span of fifteen to twenty years, ability to operate at high
speeds, and most importantly magnetic bearings are
lubricant free which allows them to operate inside a vacuum
[10].
It is important that the bearings are able to operate inside
a vacuum because the flywheel in a flywheel-based KERS
must rotate at high speeds for maximum efficiency. At such
high speeds friction caused by air resistance is enough to
cause significant energy losses and heat the carbon fiber rim
to its glass transition temperature [1]. To avoid these effects
the flywheel must be enclosed in a vacuum housing. The
housing will ensure that the flywheel is performing under
ideal conditions but will also offer protection to the rest of
the vehicle in case of failure. Because the flywheel is driven
by an axle and must operate in a vacuum, a rotating seal is
used where the axle enters the housing. The rotating seal is
not fully impermeable so a small vacuum pump must
evacuate excess air from the chamber. This is a negligible
amount of energy that the vehicle consumes because it is
only necessary to run the pump for 90 seconds a day [4].
Another approach to this problem is to have the flywheel
operate in a complete vacuum and use magnets to transfer
energy between the flywheel and the shaft connected to the
transmission. Using a complete vacuum eliminates the need
for a vacuum pump and reduces the overall size of the
system. Ricardo, a company that develops flywheel-based
KERS, has taken this approach in their Kinergy system.
They use an array of permanent magnets to transfer the
energy between the flywheel and shaft. There is one magnet
that is attached to the shaft that the flywheel rotates about
and another that is attached to the external shaft. The
magnetic fields of the two magnets interlock with each other
producing an effect similar to that of two gears. This
enables the shaft that is connected to the transmission to
transfer energy to the flywheel without directly entering the
vacuum [4].
that they plan on testing in an Optare Solo city bus. The
system consists of a high speed flywheel that is made of
carbon fiber wound around a steel rim, full toroidal CVT,
and vacuum housing. Rather than take the approach of a
vacuum pump and rotating seal, the developers have chosen
to use a magnetic coupling, as described previously, to rotate
the flywheel. The rollers that control the ratio between
vehicle speed and flywheel speed are adjusted using
hydraulic pistons. The amount at which they are adjusted is
proportional to the torque of the input and output shaft. The
FLYBUS system is designed so that it connects to the
existing transmission of the bus. This allows the option of
affordably retrofitting the system to existing buses.
FIGURE 3
THE FLYBUS SYSTEM ATTACHED TO THE BUS TRANSMISSION. THE
BROWN COMPONENT IS THE FLYWHEEL CHAMBER, BLUE IS THE CVT,
AND GRAY IS THE EXISTING TRANSMISSION [12].
Should anything happen to the actual flywheel module, it is
designed to be easily removed and replaced by a new one.
The system is much cheaper than its electrical counterpart
and because of the stop and start pattern of buses the
FLYBUS system would have a dramatic effect on fuel
consumption of city buses [11].
FLYBUS
ADVANTAGES AND DISADVANTAGES OF USING
FLYWHEEL-BASED KINETIC ENERGY RECOVERY
SYSTEMS
These advancements in flywheel technology have allowed
for the effective use of flywheel KERS in vehicles.
Torotrak, a leader in flywheel technology, in partner with
Ricardo, Optare and Allison Transmission Inc. is developing
a flywheel system, FLYBUS, for use in city buses. There
have already been attempts at creating a hybrid bus but these
have been with the use of electrical technology. These
systems have had very little success because they increase
the cost of the typical bus by about 80-120% and have little
potential to be retrofitted to existing vehicles [11]. This has
led to development of a more appropriate technology.
Torotrak along with its partners have developed a system
Before deciding to implement this new technology, it is
important to consider the advantages and disadvantages of
these systems. A flywheel-based KERS provides a variety
of benefits that increase the viability of this system in
today’s transportation. These advantages include high
efficiency, low fuel consumption, and low cost. Although
the system has a few drawbacks, many problems can be
reduced or outweighed by the benefits.
One advantage of a flywheel-based KERS is its weight. A
concern with the addition of a KERS to a vehicle is that the
weight of the system will increase the vehicle’s fuel
consumption and defeat the purpose of installing it in the
4
Nathan Harlow
Robert Scott Johnson
first place. However, due to the lightweight design of the
flywheel and accompanying components, the additional
weight is insignificant when analyzing fuel efficiency.
Moreover, the system is contained in a small package,
making it easy to incorporate into the rear of a vehicle.
Another advantage is the ability of the flywheel to store
energy efficiently. As mentioned earlier, there is no
transformation to electrical or chemical energy as there is
with an electrical kinetic energy recovery system. This
greatly reduces energy losses in the system. Tests have
proven that flywheel-based KERS can recover and store
over 70% of the vehicle’s energy [1]. The only losses that
remain are those due to friction and air resistance. However,
the magnetic bearings and vacuum chamber mentioned
previously have been developed to minimize these effects.
Energy is transferred from the driveline to the KERS
during the deceleration of the vehicle. When this energy is
given to the flywheel, the flywheel acts as a brake, slowing
down the vehicle as it recovers the energy. Instead of
releasing the energy as heat, the energy is recovered. This
process reduces break wear. As a whole, the flywheel-based
KERS is designed to last the lifetime of the vehicle. In
addition, the system is low maintenance.
Another one of the concerns with a flywheel-based KERS
is safety. The flywheels found in a kinetic energy recovery
system can store up to 400 kJ of energy, which means that
failure while rotating at 60,000 rpm could cause immense
amounts of damage. To address this concern, the flywheel
housing doubles as a containment chamber in case of failure.
Efforts have been made to ensure the safety of the system by
conducting tests of system response time, structural safety of
the components, and crash test safety. These tests have
concluded that flywheel-based KERS are safe and even meet
the strict standards of Formula 1 racing. It is important to
manufacture each and every part of the system to safety
standards and thoroughly test the product before it goes on
the market. Engineers need to make sure that the gyroscopic
forces of the flywheel do not affect the handling of the
vehicle. This technology relies on specific conditions in
order to avoid catastrophic failure. For example, if defective
flywheel housings are put on buses full of people, the
passengers are put in serious danger. An accident using this
technology in early stages of development could terminate
further research and production.
The flywheel-based KERS is not designed to be a standalone source of power for a vehicle like batteries are in
electric cars. It is designed for temporary energy storage that
is to be used frequently and in smaller amounts. Its purpose
is to reduce fuel consumption by providing additional power
during the acceleration of a vehicle. Periods of acceleration,
especially from a stop, are when the efficiency of the vehicle
is at its lowest. This is seen when comparing the gas mileage
of city and highway driving. The miles per gallon of a
vehicle travelling in the city are significantly lower than the
miles per gallon of a vehicle on the highway. The start-stop
pattern of city driving requires constant changes in speed as
drivers move from stoplight to stoplight. The KERS is
implemented to aid the acceleration in order to reduce fuel
consumption and increase fuel efficiency by 10-20% [13].
This also cuts the amount of money spent on fuel for the
vehicles, which is a huge bonus due to rising gas prices.
The biggest benefit of introducing flywheel-based kinetic
energy recovery systems is the low cost of production. In
order to move this technology into regular production
vehicles, it is necessary for the equipment to cost as little as
possible. At a lower cost, vehicles with flywheel-based
KERS will be available to more consumers. The entire
kinetic energy recovery system is projected to cost about
$2000 per vehicle, which is far less than the $8000 required
to produce a hybrid electric vehicle [4]. This cost would
continue to drop as the system is further developed.
As this technology expands into the automotive industry,
it could have a greater influence on sustainability practices.
Although it does not eliminate any environmental problems,
kinetic energy recovery systems are a response to rising oil
prices and environmental concerns. With this in mind,
manufacturers and consumers alike will quickly move to
utilize this technology.
THE FUTURE OF FLYWHEELS
The main proponent that will launch flywheel-based kinetic
energy recovery systems into the automotive industry is the
low cost. One reason why hybrid vehicles have never really
caught on is because it costs so much money to produce
them. In fact, many automotive companies lose money
producing these vehicles. However, flywheel-based KERS
are set to change this with their low cost. Manufacturers
would see this benefit and start the integration of these
systems into their own vehicles. In turn, consumers would be
attracted to these vehicles because they could be sold at
lower prices.
Any vehicle could be designed with a flywheel-based
kinetic energy recovery system, but the area most affected
by this technology would be any vehicle with a start-stop
cycle of driving. This includes a wide variety of vehicles,
both large and small. For example, this technology has
already been tested in FLYBUS, a flywheel hybrid system
developed for buses. Buses run routes that contain frequent
stops, so a KERS could make those routes more efficient.
This extends to all public transportation, such as school
buses, shuttles, and even taxis. The flywheel-based KERS
also has applications in delivery trucks, mail trucks and
garbage trucks that make frequent stops. As for other
vehicles, many smaller city cars could be outfitted with these
systems, which would far outnumber the vehicles in other
categories.
Better yet, it could be possible to retrofit existing vehicles
with a kinetic energy recovery system. This includes the
millions upon millions of cars, trucks, and buses on the
roads today. It could be proven to be cheaper to install a
5
Nathan Harlow
Robert Scott Johnson
https://netfiles.uiuc.edu/mragheb/www/NPRE%20498ES%20Energy%20St
orage%20Systems/Kinetic%20Energy%20Flywheel%20Energy%20Storage
.pdf
[4](December 3, 2011) “Reinventing the wheel.” The Economist. [Online].
Available:
http://www.economist.com/node/21540386 Accessed: 25
January 2012
[5](May 31, 2011) “Volvo shows off KERS flywheel tech.” Autoblog.
[Online]. Available: http://www.autoblog.com/2011/05/31/volvo-showsoff-kers-flywheel-tech-w-video/
[6] Boretti, Alberto. (8 June 2010) “Comparison of fuel economies of high
efficiency diesel and hydrogen engines powering a compact car with a
flywheel based kinetic energy recovery systems.” Sciencedirect. [Online].
Available:
http://www.sciencedirect.com/science/article/pii/S0360319910009663
[7]Johnston, Christopher. (August 11, 2010) “High-Pressure Hybrids: FuelEfficient Hydraulic Vehicles Come of Age.” Scientific American. [Online].
Available:
http://www.scientificamerican.com/article.cfm?id=hydraulichybrid-vehicle
[8]Harris, William. (April 27, 2005) “How CVT’s Work.”
HowStuffWorks.com.
[Online].
Available:
http://auto.howstuffworks.com/cvt.htm
[9]Vivani, Steffani. “Toroidal System.” What Would DaVinci Drive?
[Online]
Available:
http://www.odec.ca/projects/2007/viva7s2/toroidal2.htm
[10]Mraz, Stephen. (September 16, 2004) “Magnetic Bearings Come of
Age.”
MachineDesign.com.
[Online].
Available:
http://machinedesign.com/article/magnetic-bearings-come-of-age-0916
[11]Fuller, John, Atkins, Andrew. (2011) “Hardware Development of
FLYBUS – Flywheel Based Mechanical Hybrid Systems for Bus &
Commercial
Vehicles.”
Torotrak.
[Online].
Available:
http://www.torotrak.com/pdfs/tech_papers/2011/Flybus_Paper_final.pdf
[12](November 16, 2010) “Low-Cost Hybrid System Wins Award For
Heavy Goods Vehicle CO2 Reduction Technology.” Newspress. [Online].
Available:
http://www.newspress.co.uk/public/ViewPressRelease.aspx?pr=25576
[13](6 September 2011) “Flybus to start testing first flywheel hybrid bus.”
Torotrak. [Online]. Available:
http://www.torotrak.com/pdfs/rns/2011/TOR7168%20Flybus%20LCV%20
2011%20FINAL.pdf
[14] Hilton, J., Cross, D. “Flybrid systems: breakthrough technology for
greener driving.” The Royal Academy of Engineering. [Online]. Available:
http://innovationnow.raeng.org.uk/innovations/default.aspx?item=6
flywheel-based KERS in a whole line of buses than replace
each bus with an entirely new model.
The overall energy saved in these groups would make a
huge impact on fuel consumption. By reducing fuel
consumption,
the
flywheel-based
KERS
lowers
environmental impact by decreasing harmful CO2 emissions.
It has been found that the amount of CO 2 emitted during the
manufacturing of one flywheel KERS is made up for within
the first 12,000 km of driving [14]. In addition, as opposed
to a hybrid electric vehicle, a flywheel-based mechanical
hybrid does not have the harmful chemicals to dispose of
that are found in batteries. Sustainability is an increasingly
mentioned term that automobile manufacturers focus on
within the vehicle and outside the vehicle in the
environment.
A TECHNOLOGY OF POTENTIAL
The flywheel-based KERS is certainly a technology of
importance and potential. With some work, this system
could increase the efficiency of hybrid vehicles. It would
reduce fuel consumption, and help preserve the environment.
Lower CO2 emissions may reduce air pollutions in
congested cities. It could be developed by automotive
companies worldwide for a fraction of the cost of other
hybrid vehicles. Flywheel-based KERS would be found in
cities all over the world, in buses, cars, and trucks. Even
current vehicles could be retrofitted with this technology.
The flywheel-based kinetic energy recovery system does
not come without flaws, however. Developments still need
to be made in reducing the forces that act upon the flywheel.
With these forces minimized, the system would have much
higher efficiency and would be able to store energy longer. It
would rival hybrid electric vehicles in efficiency and range.
Until this point is reached, the world will continue to drive
around in gas-guzzling machines.
ADDITIONAL RESOURCES
Leumund. (April 26, 2011) “Flybus flywheel-based mechanical hybrid
system.”
Youtube.
[Online
video].
Available:
http://www.youtube.com/watch?v=BfRmtkKUdMI
REFERENCES
[1]Brockbank, C., & Cross, D. (2008) “Mechanical Hybrid system
comprising a flywheel and CVT for Motorsport & mainstream Automotive
applications.”
Torotrak.
[Online].
Available:
http://www.torotrak.com/pdfs/tech_papers/2009/sae_wc_2009_09pfl0922_kers.pdf
[2]Kaufmann, Rachel. (February 23, 2011) “Upgrading the Electric Grid
with Flywheels and Air.” National Geographic. [Online]. Available:
http://news.nationalgeographic.com/news/energy/2011/2/110223-electricgrid-flywheels-compressed-air/
[3]Ragheb, M. (3 November 2010) “Kinetic Energy Flywheel Energy
Storage.”
UIUC.
[Online].
Available:
ACKNOWLEDGMENTS
First, we would like to thank the Hillman Library for
providing a great place to work. We would also like to thank
Beth Newborg for providing assistance on the paper. Finally,
we would like to thank Ryan Soncini, Matt Castiglia, and
Franklin Preuss for mentoring us about writing technical
papers.
6