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INTRODUCTION
Kinetic energy recovery system(KERS) is an automotive system for recovering a vehicle’s kinetic energy under braking.KERS was introduced in 2009 series of formula one motor sport. It is an energy saving device fitted to engines to store wasted energy and convert it to useful form of energy. During braking, kinetic energy of a vehicle is wasted as it is converted in to heat and sound energy that is dissipated in to the environment. ”Energy cannot be created or destroyed, but can be converted endlessly”, this is the basic principle of KERS.Its working principle involves storing energy wasted during braking and use it for acceleration. It not only recover wasted energy but also assist in braking.For a driver, having KERS is like having two power sources, one is the engine and the other is stored kinetic energy. It can store up to 8BHP for 6.67sec. There are three main components in KERS system, a component for generating power, storing it and converting it.Depending on the way they convert energy and how it is stored in s system, it is classified in to two types, mechanical and electrical. Mechanical KERS uses flywheel while electrical KERS uses battery to convert and store energy. KERS have wide range of applications in modern world, it can be implemented in bikes, cars, bicycle etc.
LITERATURE REVIEW
DholakiyaUtsav M et al [1] describes about different types of KERS (Kinetic Energy Recovery System). It actually refers to a technology that is used to recover the kinetic energy of any object that is lost while retardation.KERS is a collection of parts which takes some of the kinetic energy of a vehicle under deceleration, stores this energy and then releases this stored energy back into the drive train of the vehicle, providing a power boost to vehicle. It is having a very wide range of applications in today’s world of advanced technologies as it is applicable in bicycles, bikes, cars as well as any other rolling application that has a variation in speed because of deceleration, as these all are it is commercial and practical application.
Pottabattininaveen et al [2] describes about Kinetic Energy Recovery Systems (KERS), which is one of the most significant technical introductions for the Formula One Race. Formula One have always lived with an environmentally unfriendly image and have lost its relevance to road vehicle technology. This eventually led to the introduction of KERS. It is an energy saving device fitted to the engines to convert some of the waste energy produced during braking into useful form of energy. The system stores the energy produced under braking in a reservoir and then releases the stored energy under acceleration.
Alberto. Borettiet al [3] also named the mechanical KERS as M-KERS and electrical KERS as E-KERS and by his research, it was founded that M-KERS on the rear non-motored wheels, the thermal engine powering the front wheels has to supply 0.31 MJ/km for a 1 ton vehicle of standard rolling and aerodynamic resistances covering a modified version of the new European driving cycle.
Kevin Ludlum et al [4] displayed a fairly simple design with implementation of a kinetic energy recovery system with a nonegligible increase in the efficiency of a bicycle. Also reasoned to use a flywheel that, flywheel has environmental impact only at its time of production, and has the potential to heavily outweigh those costs through its use. Bikes do not have the pollution problems, cars and other modes of transportation have, but they can serve as a good analogy for how a kinetic energy recovery system can increase the efficiency of a vehicle.
U. Mugunthan et al [5] have been performed an overdrive test to observe the efficiency of bicycle. It has been found out that the flywheel supplies an energy with which the cycle could move forward by 10% of the given input. Depending upon the input given, the efficiency varies. But only 10% can be obtained by this principle. This system when installed in vehicles would save a greater amount of energy lost during the braking of the vehicle. This energy can be stored and can be reused when needed. It is more efficient when compared to the conventional braking system. We would conclude that, this recovery system has to be developed further and has a wide range of research which can be conducted in the future.
KINETIC ENERGY RECOVERY SYSTEM
The KERS acronym for Kinetic Energy Recovery System is a system that utilizes the Kinetic Energy that is lost while retardation. This is an efficient system as it utilizes the energy lost within the system. This system converts the loss of kinetic energy to gain in kinetic energy and this gain is utilized in the engine power. This system is a kind of regenerative braking system. Energy is conserved when using this system as energy lost in braking is utilized. The following session describes this system in detail.
KERS is a collection of parts which takes some of the kinetic energy of a vehicle under deceleration, stores this energy and then releases this stored energy back into the drive train of the vehicle, providing a power boost to vehicle. KERS has a very wide range of applications in today’s world of advanced technologies. As it is applicable in bicycles, bikes, cars as well as any other rolling application that has a variation in speed because of deceleration, as these all are it is commercial and practical application. KERS system used in the vehicles satisfies the purpose of saving a part of the energy lost during braking and it can be operated at high temperature range and are efficient as compared to conventional braking system. The results from some of the test that he conducted show that around 30% of the energy delivered can be recovered by the system. The use of more efficient systems could lead to huge savings in the economy of any country. Here we are concluding that the topic KERS got a wide scope in engineering field to minimize the energy loss
CHAPTER 4
COMPONENTS OF KERS
The KERS system consist of three main components, a component for generating power, one to store it and another to control it
The components of KERS system are
• The motor generator unit (MGU)
• The PCU (power control unit)
• The batteries/flywheel
1 MOTOR GENERATOR UNIT
The MGU consist of motor and generator coupled together.
Figure 4.2 Motor Generator Unit
This unit consists of a motor and a generator unit. A singe rotor is provided around a single rotor that uses a single rotor that is wound around the rotor coils of the motor and generator. Thus they share the same outer field coils and so the magnets work in two modes. This unit creates charge for battery when the car is braking and this power is returned to engine to obtain additional power using the KERS button.
4.2 POWER CONTROL UNIT
This unit is used to invert current from the batteries to the MGU. This cell also monitors the individual cells in the battery. This function is essential as the efficiency of battery will be reduced when one cell starts to fail. Failing cells can cause overheating of the system and thus cooling of the PCU system is needed.
WORKING PRINCIPLE
“Energy cannot be created or destroyed, but it can be endlessly converted”, it is the basic principle of kinetic energy recovery system.During braking, kinetic energy of a vehicle is wasted as it is converted in to heat and sound energy that is dissipated in to the environment. By using a KERS system this wasted energy can be captured and used to give extra power to the engine. When a car is moving it has kinetic energy, during braking this energy is converted to heat and sound. The KERS system captures this energy and stores it in storage device (Batteries/Flywheel). When the driver presses boost button, the stored energy is given back to engine by the electric alternator/motor.
TYPES OF KERS
Depending on how the energy is stored and how they convert energy, KERS can be classified in to two, mechanical and electrical. Mechanical KERS uses a flywheel whereas electrical KERS uses battery.
6.1. ELECTRICAL KERS
Electrical KERS uses an electric motor/generator unit (MGU) to capture the kinetic energy that is being wasted while braking. MGU is mounted on one end of engine crankshaft. The main function of this unit is to charge the batteries under braking and release this energy during acceleration. It converts kinetic energy to electrical energy and stores it in batteries, when the driver presses boost button it converts the stored electrical energy back to kinetic energy and is given to the engine. Most of the electrical KERS systems uses lithium ion battery to store energy. The main challenged faced by using lithium ion battery is that it gets hot, so an additional ducting is required in the car.
With this system when brake is applied the electric motor mounted to the crankshaft captures a small portion of rotational force or kinetic energy that is being released. It then converts kinetic energy to electrical energy and stores it in high voltage batteries. When accelerator is pressed the stored electric energy is converted back to kinetic energy and is used to drive the car.
MECHANICAL KERS
Mechanical KERS was invented by IanFoley. This system uses a flywheel to store energy and it uses transmission to control and transfer energy instead of MGU in electrical KERS. Mechanical KERS has more efficiency compared to electrical system, since it requires less number of energy conversions. It has efficiency twice that of electrical systems.
This system uses a huge storage reservoir to store mechanical energy and it is independent of the gear box. While braking the captured kinetic energy is used to turn the flywheel and when more energy is required it is coupled to the flywheel
ADVANTAGES OF MECHANICAL KERS OVER ELECTRICAL KERS
• Efficiency losses are observed in battery based hybrid systems due to large number of energy conversions occurring within the system
• On reapplication in an electric system the global energy conversion is 31-34%
• Using a mechanically operating flywheel the various energy conversions can be easily eliminated and the global energy conversion is nearly 70% that is more than nearly twice that of electric application.
ADVANTAGES AND LIMITATIONS OF KERS
The advantages are:
• High power capability
• Long system life of upto 250,000 kms
• Completely safe
• A truly green solution
• Low embedded carbon content
• Low cost in volume manufacture
The limitations are:
• 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.
CHAPTER 8
CONCLUSION
The KERS is environment friendly system. It utilizes the energy that is produced within the vehicle and supplies this energy to the engine so that extra power is gained. It has reduced emissions and production cost. It is customizable and modifiable. It utilizes the idea of regenerative braking and so it consumes less fuel and thus reduced Carbon dioxide emission. It has a wide range of application in the field of manufacturing of trucks, buses, passenger and luxury cars.