UWE Bristol Engineering showcase 2015

Dharmesh Hirapara
BEng Mechanical Engineering
Regenerative Braking System
The idea came in 1970’s when energy crisis caused researchers to study about the feasibility and practicality of implementing
hybrid power along with regenerative braking systems, which have the potential to improve the fuel economy of vehicles
operating under urban driving conditions. Urban driving condition refers to excessive use of brakes during the city driving. The
increase in price of petroleum-based fuel in the past few years has also given rise to various research and development efforts
for energy conservation. However, reduced fuel consumption and therefore operating cost and reduced gaseous emissions
including primarily carbon dioxide (hence global warming) are the major driving forces behind commercial considerations of
such systems.
Energy storage by flywheel systems
The benefit of using flywheel technology is that more of the forward
inertial energy of the car can be engaged even during relatively short
intervals of braking and acceleration. In case of batteries they are not
able to accept charge at these rapid intervals, thus more energy is lost to
the friction. The electric battery has had its demerits. One of the demerits
of the electric battery is the inherent losses that accompany the energy
transformations, due to which, the transfer efficiency can be quite low.
The other demerits are that, they have a low specific power (power per
unit weight of storage system), a low storage efficiency which diminishes
which each charge/discharge cycle and lack of required service life span.
These reasons contribute to a limited range for battery electric vehicle
(BEV) due to which, hybrid electric vehicles (HEVs) have become fairly
more successful as they use an internal combustion engine, with its
relatively high specific energy and power, to supplement the battery.
There has been ongoing research into other electrochemical batteries like
Li-ion and NiMH etc., for better performance for these applications.
Kinetic energy recovery system (KERS)
The moving bodies have energy in the form of kinetic energy be. To move any object, work has
to be done. Energy is supplied by burning the fuel in car engines or from other sources such as
electric batteries and solar power. Now as natural resources like petroleum are depleting and
the cost keeps on fluctuating, so under these circumstances we need to fully utilize the
available energy to get maximum output. During driving or any operation involving braking,
energy is wasted. To save that energy from being wasted, kinetic energy recovery was
introduced in 1970’s. Initially energy is stored with the help of flywheel. Kinetic storages, also
known as Flywheel Energy Storages (FES), are used in many technical fields. The working
principle is based on inertial mass, which is accelerating to a very high rotational speed and
maintaining the energy in the system as rotational energy because of inertia of the body,
obeying newton’s first law of motion. Newton’s first law of motion sates that a body continues
is state of rest or motion unless an external force in applied on it. Inertia is the ability of the
body to resist change in its state of rest or motion. The energy is converted back as the
flywheel slows down the releasing the stored energy. Available performance comes from
moment of inertia effect and operating rotational speed.
Project Supervisor
Farid Dailami
Project summary
The idea of regenerative braking system is based on
kinetic energy recovery system. The aim of both
systems is to conserve and use energy. Regenerative
energy system can be used where excessive braking is
required to save the energy being lost in the process.
In efforts to produce greener cars numerous
processes have been examined that effect fuel
consumption. One of the processes is braking. The
traditional braking wastes energy because it kills the
momentum that the engine has built up. However,
with the process of regenerative braking, this energy
effectively finds a new home. Instead of being lost as
heat in the brakes, the energy is used to drive an
alternator, which allows the energy to be partially
recovered and stored in a battery.
Project Objectives
• To understand the idea, concept and elements of
regenerative braking system. And study the
advantages of regenerative braking system.
• To understand and study the need and importance
of regenerative braking system. .
• To understand and study the applications of
regenerative braking system.
• Compare conventional braking systems, dynamics
braking systems, frictional braking systems, and
regenerative braking system.
• Develop and study the current and further scope
for development of regenerative braking system.
Project Conclusion
The regenerative braking systems are better option
than other conventional form of braking systems as it
can operate at high range of temperature.
Various results evaluated from the studies conclude
that almost 30 per cent of the energy can be
recovered by the regenerative braking. Therefore, the
regenerative braking systems have a wider scope in
the transportation sector.
Regenerative brakes should be used with mechanical
brakes to provide good braking as well as
conservation of energy. The regenerative braking
system is significantly better at recovering energy and
stopping compared to the conventional braking
system as the mechanical braking system stops
significantly faster, but no energy is recovered