kinetic energy recovery system

A SEMINAR ON

KINETIC ENERGY

RECOVERY SYSTEM (KERS)Prepared By:

HARSH GUPTA

Mechanical Engineering- 5th Semester

JSSATE, NOIDA

Supervised by:MR. M NAGARAJ

CONTENTS

KERS- INTRODUCTION BASIC ELEMENTS WORKING PRINCIPLE TYPES OF KERS ELECTRICAL KERS MECHANICAL KERS KERS IN FORMULA ONE CONCLUSION

KERS EXPLAINED

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 that vehicle.

For the driver, it is like having two power sources at his disposal, one of the power sources is the engine while the other is the stored kinetic energy.

WHAT IS KERS?

The acronym KERS stands for Kinetic Energy Recovery System.

Kinetic energy recovery systems (KERS) store energy when the vehicle is braking and return it when accelerating. 

During braking, energy is wasted because kinetic energy is mostly converted into heat energy or sometimes sound energy that is dissipated into the environment.

Vehicles with KERS are able to harness some of this kinetic energy and in doing so will assist in braking.

By a touch of a button, this stored energy is converted back into kinetic energy giving the vehicle extra boost of power.

BASIC ELEMENTS OF KERS

First, a way to store and then return energy to the power train and

Second, a place to store this energy.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: The MGU, the PCU and the batteries/flywheel.

MGU (MOTOR/GENERATOR UNIT)

While a motor-generator set may consist of distinct motor and generator machines coupled together, a single unit motor-generator will have both rotor coils of the motor and the generator wound around a single rotor, and both coils share the same outer field coils or magnets 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.

PCU (Power Control Unit)

It serves two purposes, firstly to invert & control the switching of current from the batteries to the MGU and secondly to monitor the status of the individual cells with the battery. Managing the battery is critical as the efficiency of a pack of Li-ion cells will drop if one cell starts to fail. A failing cell can overheat rapidly and cause safety issues. As with all KERS components the PCU needs cooling.

WORKING PRINCIPLE

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 tries to store this energy and converts this into power, that can be used to boost acceleration.

A standard KERS operates by a ‘charge cycle and a ‘boost cycle’. As the car slows for a corner, an actuator unit captures the waste kinetic energy from the rear brakes. This collected kinetic energy is then passed to a Central Processing Unit (CPU) and onto the storage unit. The storage unit are positioned centrally to minimize the impact on the balance of the car.

TYPES OF KERS

There are two basic types of KERS systems:

Electrical Mechanical

The main difference between them is in the way they convert the energy and how that energy is stored within the vehicle.

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.

The most difficult part in designing electrical KERS is how to store the electrical energy. Most racing systems use a lithium battery, which is essentially a large mobile phone battery.

Batteries become hot when charging them so many of the KERS cars have more cooling ducts since charging will occur multiple times throughout a race.

Super-capacitors can also be used to store electrical energy instead of batteries; they run cooler and are debatably more efficient.

WORKING PRINCIPLE

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.

The kinetic energy of the vehicle ends up as kinetic energy of a rotating flywheel through the use of shafts and gears.

Unlike electrical KERS, this method of storage prevents the need to transform energy from one type to another. Each energy conversion in electrical KERS brings its own losses and the overall efficiency is poor compared to mechanical storage.

To cope with the continuous change in speed ratio between the flywheel and road-wheels, a continuously variable transmission (CVT) is used, which is managed by an electro-hydraulic control system. A clutch allows disengagement of the device when not in use.

Braking at the wheels dissipates the kinetic energy of the vehicle that is therefore completely lost. Conversely, KERS may store the kinetic energy of the vehicle during braking and return it under acceleration.

The system utilises a flywheel as the energy storage device and a Continuously Variable Transmission (CVT) to transfer energy to and from the driveline to the rotating flywheel.

The transfer of the vehicle kinetic energy to the flywheel kinetic energy reduces the speed of the vehicle and increases the speed of the flywheel. The transfer of the flywheel kinetic energy to the vehicle kinetic energy reduces the speed of the flywheel and increases the speed of the vehicle.

The CVT is used because the ratios of vehicle and flywheel speed are different during a braking or an acceleration event. can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios.

ADVANTANGE OF MECHANICAL KERS OVER ELECTRICAL KERS

Battery-based electric hybrid systems require a number of energy conversions each with corresponding efficiency losses. On reapplication of the energy to the driveline, the global energy conversion efficiency is 31–34%. The mechanical hybrid system storing energy mechanically in a rotating fly wheel eliminates the various energy conversions and provides a global energy conversion efficiency exceeding 70%, more than twice the efficiency of an electric system.

ADVANTAGES OF KERS

This potential advantages and features of this technology in the field of automobiles are:

High power capability Light weight and small size Long system life of upto 250,000 kms Completely safe A truly green solution High efficiency storage and recovery Low embedded carbon content Low cost in volume manufacture 

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.

The original CVT based Formula One KERS

FEATURES OF KERS IN F1

The original Kinetic Energy Recovery System (KERS) was a small and light device designed to meet the FIA regulations for the 2009 Formula One season.

The key system features were: A flywheel made of steel and carbon fibre that rotated at over

60,000 RPM inside an evacuated chamber The flywheel casing featured containment to avoid the escape

of any debris in the unlikely event of a flywheel failure 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

60 kW power transmission in either storage or recovery 400 kJ of usable storage (after accounting for internal losses) A total system weight of 25 kg A total packaging volume of 13 litres

FLYWHEEL HYBRID CARS

A consortium led by a Jaguar Land Rover is developing a flywheel-hybrid system that it says boosts performance by 60 kilowatts (about 80 horsepower) while improving fuel efficiency 20 percent. Jaguar is testing its purely mechanical flywheel system, which reportedly weighs 143 pounds, in an prototype XF sedan.

At the 2011North American International Auto Show Porsche unveiled a RSR variant of their Porsche 918 concept car which uses a flywheel-based KERS system that sits beside the driver in the passenger compartment and boosts the dual electric motors driving the front wheels and the 565 BHP V8 gasoline engine driving the rear to a combined power output of 767 BHP.

CONCLUSION

It’s a technology for the present and the future because it’s environment-friendly, reduces emissions, has a low production cost, 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, buses and trucks.

REFERENCE

Wikipedia autosport.com saeindia.org Cross, Douglas. "Optimization of Hybrid

Kinetic Energy Recovery Systems (KERS) for Different Racing Circuits." SAE Digital Library. SAE International. Web. 25 Sept. 2009.

Sorniotti, Aldo, and Massimiliano Curto. "Racing Simulation of a Formula 1 Vehicle with Kinetic Energy Recovery System." SAE Digital Library. SAE International. Web. 25 Sept. 2009.