Kinetic Energy Recovery System - Brief

October 11, 2017 | Author: Naveen | Category: Brake, Hybrid Vehicle, Transmission (Mechanics), Clutch, Vehicles
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Basics in Kinetic energy recovery systems and its various applications...


1 Kinetic Energy Recovery System

A Seminar on



Department of Mechanical engineering Session 2013-14



U.I.E.T., K.U.K.

Dept. of Mechanical Engineering



2 Kinetic Energy Recovery System CHAPTER-1 INTRODUCTION

CHAPTER-2 KERS & REGENERATIVE BRAKING 2.1 KERS dissimilar from Regenerative Braking



5-7 7


3.1 Mechanical KERS


3.2 Electro-mechanical KERS


3.3 Hydraulic KERS


3.4 Electronic KERS




4.1 KERS in Formula1












5.1 Abstract


5.2 Introduction


5.3 KERS Bicycle Working


5.4 Design Requirement


5.5 Bill of Material


5.6 Fabrication Process


U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

3 Kinetic Energy Recovery System





1. INTRODUCTION KERS means Kinetic Energy Recovery System and it refers to the mechanisms thatrecover the energy that would normally be lost when reducing speed. The energy is stored in a mechanical form and retransmitted to the wheel in order to help the acceleration. Electric vehicles and hybrid have a similar system called Regenerative Brake which restores the energyin the batteries.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. U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

4 Kinetic Energy Recovery System

There are principally two types of system - battery (electrical) and flywheel (mechanical). Electrical systems use a motor-generatorincorporated in the car’s transmission whichconverts mechanical energy into electrical energy and vice versa. Once the energy has been harnessed, it is stored in a battery and released when required.

Mechanical systems capture braking energy and use it to turn a small flywheel which can spin at up to80,000 rpm. When extra poweris required, the flywheel is connected tothe car’s rear wheels. In contrast to an electrical KERS,themechanical energy doesn’t changestate and is thereforemore efficient.

There is one other option available - hydraulic KERS, where braking energy is used to accumulate hydraulic pressure which is then sent to the wheels when required.

2. KERS ®ENERATIVE BRAKING Since kinetic energy is the energy of motion, you could probably guess that cars create lots of it. Capturing some of that kinetic energy for the sake of fuel efficiency in a hybrid car is a little tricky, but regenerative braking is one common method employed by many automakers. On a non-hybrid car during a routine stop, mechanical braking slows and then stops the vehicle. For instance, if your vehicle has disc brakes, the brake pads clamp down on a rotor to stop the car. If your car has drum brakes, the brake shoe pushes the brake lining material outward U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

5 Kinetic Energy Recovery System toward the brake drum surface to slow or stop the car. In both cases, most of the kinetic energy in the spinning wheels is absorbed by the pads or the drums, which creates heat. On a hybrid car that uses regenerative braking, the electric motor is used to slow the car. When the motor is operating in this mode, it acts as a generator to recover the rotational kinetic energy at the wheels, convert it into energy and store it in the car's batteries. When the driver of the hybrid car takes his or her foot off of the accelerator pedal, the resistance provided by the generator slows the car first and then the mechanical brake pads can be applied to finish the job. Of course, the mechanical brake pads can also be engaged immediately in an emergency braking scenario. The car uses the energy stored in the battery to power the electric motor which drives the car at low speeds. Depending on the type of hybrid, the electric motor can either work alone to move the car or it can work in concert with the car's gasoline-powered engine. So regenerative braking, coupled with eco-friendly driving techniques like slow starts and slower overall vehicle speeds, is an important feature on some of the most fuel-efficient vehicles on the road today. Regenerative brakes may seem very hi-tech, but the idea of having "energy-saving reservoirs" in machines is nothing new. Engines have been using energy-storing devices called flywheels virtually since they were invented. The basic idea is that the rotating part of the engine incorporates a wheel with a very heavy metal rim, and this drives whatever machine or device the engine is connected to. It takes much more time to get a flywheel-engine turning but, once it's up to speed, the flywheel stores a huge amount of rotational energy. A heavy spinning flywheel is a bit like a truck going at speed: it has huge momentum so it takes a great deal of stopping and changing its speed takes a lot of effort. That may sound like a drawback, but it's actually very useful. If an engine (maybe a steam engine powered by cylinders) supplies power erratically, the flywheel compensates, absorbing extra power and making up for temporary lulls, so the machine or equipment it's connected to is driven more smoothly. U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

6 Kinetic Energy Recovery System The heavy metal flywheel attached to this engine helps to keep it running at a steady speed. Note that most of the heavy metal mass of the flywheel is concentrated around its rim. That gives it what's called a high moment of inertia: it takes a lot of energy both to make it spin fast and slow down. It's easy to see how a flywheel could be used for regenerative braking. In something like a bus or a truck, you could have a heavy flywheel that could be engaged or disengaged from the transmission at different times. You could engage the flywheel every time you want to brake so it soaked up some of your kinetic energy and brought you to a halt. Next time you started off, you'd use the flywheel to return the energy and get you moving again, before disengaging it during normal driving. The main drawback of using flywheels in moving vehicles is, of course, their extra weight. They save you energy by storing power you'd otherwise squander in brakes, but they also cost you energy because you have to carry them around all the time. Advanced transmissions that incorporate hi-tech flywheels are now being used as regenerative systems in such things as formula-1 cars, where they're typically referred to as kinetic energy recovery systems (KERS).

2.1 KERS dissimilar from Regenerative Braking Traditional hybrids acquire electrical energy from braking in a similar way that electrical KERS equipped vehicles do but the difference lies in how the energy is reused. While KERS quickly reinjects the energy back into the powertrain to provide additional power boost in conjunction with the engine, the traditional hybrid saves the energy to power the electric power train. KERS is different from traditional hybrids in that the stop start functionality is not a prime goal of the system. KERS work very well in conjunction with engine mounted Stop/Start systems, or it can be engine mounted and used for stop start functionality. The KERS hybrid system cannot be "charged" by the engine directly, which is the requirement that has led to its name, "KERS". U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

7 Kinetic Energy Recovery System

3. TYPES OF KERS Advanced transmissions that incorporate hi-tech flywheels are now being used as regenerative systems in such things as formula-1 cars, where they're typically referred to as kinetic energy recovery systems (KERS). The types of KERS that have been developed are: 3.1. Mechanical KERS 3.2. Electro-mechanical KERS 3.3. Hydraulic KERS 3.4. Electronic KERS U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

8 Kinetic Energy Recovery System

Of the three types of KERS units – mechanical, electrical and hydraulic – Formula 1 teams have decided to go for the mechanic one. The reasons behind this choice are quite logical: less weight, better weight distribution, increased power boost and improved fuel economy.

3.1 Mechanical KERS The mechanical KERS system has a flywheel as the energy storage device but 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 end up as kinetic energy of a rotating flywheel through the use of shafts and gears. Unlike electronic KERS, this method of storage prevents the need to transform energy from one type to another. Each energy conversion in electronic 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 roadwheels, a continuously variable transmission (CVT) is used, which is managed by an electrohydraulic control system. A clutch allows disengagement of the device when not in use. As Li-ion batteries are still an expensive emerging technology, plus they have associated risks, recycling and transport problems. The attraction of flywheel KERS is obvious, however no team have raced such a system in F1. Flywheels can effectively replace the Li-ion batteries with in a typical KERS system, the flywheel being mated to a second MGU to convert the power generated by the primary MGU on the engine into the kinetic to be stored in the flywheel. Williams are believed to have just such a system. However the simper flywheel solution is connect the flywheel system via a clutched and geared mechanism.

3.2 Electro-mechanical KERS In electro-mechanical KERS energy is not stored in batteries or super-capacitors, instead it spins a flywheel to store the energy kinetically. This system is effectively an electromechanical battery. There is limited space in a racecar so the unit is small and light. Therefore, the flywheel spins very fast to speeds of 50,000 - 160,000 rpm to achieve sufficient energy U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

9 Kinetic Energy Recovery System density. Aerodynamic losses and heat buildup are minimized by containing the spinning flywheel in a vacuum environment. The flywheel in this system is a magnetically loaded composite (MLC). The flywheel remains one piece at these high speeds because it is wound with high strength fibers. The fibers have metal particles embedded in them that allows the flywheel to be magnetized as a permanent magnet. The flywheel will perform similarly to an MGU. As the flywheel spins, it can induce a current in the stator releasing electricity or it can spin like a motor when current flows from the stator. This flywheel is used in conjunction with an MGU attached to the gearbox which supplies electrical energy to the flywheel from the road and returns it to the gearbox for acceleration at the touch of a button. Not all flywheels used in the electro-mechanical KERS are permanent magnets. Instead, these systems use two MGUs, one near the flywheel and another at the gearbox. Some systems use flywheels and batteries together to store energy.

3.3 Hydraulic KERS A further alternative to the generation and storage of energy is to use hydraulics. This system has some limitations, but with the capped energy storage mandated within the rules the system could see a short term application. Separate to the cars other hydraulic systems, a hydraulic KERS would use a pump in place of the MGU and an accumulator in place of the batteries. Simple valving would route the fluid into the accumulator or to the pump to either generate or reapply the stored power. Hydraulic accumulators are already used in heavy industry to provide back up in the event of failure to conventional pumped systems.

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

10 Kinetic Energy Recovery System

Fig 3.1.Carbon Fibre Hydraulic Accumulator

Using filament wound carbon fibre casing, an accumulator of sufficient capacity could be made light enough to fit into the car. They might be capped in terms of practical storage with in the confines of an F1 sized system, but McLaren had prepared just such an energy recovery system back on the late 90s, but it was banned before it could race. With the relatively low FIA cap on energy storage, just such a system could be easily packaged, the hydraulic MGU would be sited in the conventional front-of-engine position and the accumulator, given proper crash protection fitted to the sidepod. Saving space would be minimal control system (equivalent to the PCU) as the valving to control the system could be controlled by the cars main electro hydraulic system. McLaren have recently been quoted as saying the 2011 KERS would be more hydraulic and less electronic giving rise to speculation that a hydraulic storage system could be used. An older technology than that of the kinetic steering wheels and batteries to create KERS for trucks: A hydraulic fluid. The HLA (Hydraulic Launch Assist) developed by Eaton is located between the transmission and the back axis of the truck. When the driver steps on the brake, it uses the movement of the wheels to compress hydraulic fluid, thus reducing the truck’s speed. When the truck accelerates again, the energy returns to the wheels. This is a hydraulic recovery system. U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

11 Kinetic Energy Recovery System The principle behind hydraulic KERS units, by contrast, is to reuse a vehicle’s kinetic energy by conducting pressurized hydraulic fluid into an accumulator during deceleration, then conducting it back into the drive system during acceleration.

Fig. 3.2 HLA (Hydraulic Launch Assist)

This system can save up to 30% on fuel in trucks that make numerous stops such as garbage trucks. In addition brakes have a larger life span, five times more than a simple dieselelectric hybrid, which increases the weight of the truck by about half a ton. But there are some fundamental problems here as well. One is the relatively low efficiency of rotary pumps and motors. Another is the weight of incompressible fluids. And a third is the amount of space needed for the hydraulic accumulators, and their awkward form factor. None of this matters too much in, say, heavy commercial vehicles but it makes this option unsuitable for road and racing cars.

3.4 Electronic KERS In electronic 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 U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

12 Kinetic Energy Recovery System electronic 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 ofbatteries; they run cooler and are debatably more efficient.


4.1 KERS in Formula1 U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

13 Kinetic Energy Recovery System The FIA (Federation InternationaleL"Automobile) have authorized hybrid drivetrains in Formula 1 racing for the 2009 racing season. The intent is to use the engineering resources of the Formula 1 community to develop hybrid technology for use not only in motorsport but also eventually in road vehicles. The hybrid systems specifications have been kept to a minimum, especially the type of hybrid system. This was done purposely to lead to the study and development of various alternatives for electrical hybrids which has been met with success. The Flybrid Kinetic Energy Recovery System (KERS) was a small and light device designed to meet the FIA regulations for the 2009 Formula One season.

Fig 4.1 Schematic Assembly Of KERS in a F1 car

The key system features were:

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

14 Kinetic Energy Recovery System 

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 the CVT

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 liters

The layout of the device was tailored exactly to meet the customer's requirement resulting in a truly bespoke solution that fitted within the tight packaging constraints of a F1 car. The mechanical KERS system utilises flywheel technology developed by Flybrid Systems to recover and store a moving vehicle’s kinetic energy which is otherwise wasted when the vehicle is decelerated.

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

15 Kinetic Energy Recovery System Fig 4.2 Flybrid Kinetic Energy Recovery System

Fig 4.3 A KERS flywheel

With a focus on safety, the FIA have specified a limit on both the power rating of the hybrid system at 60kW and the quantity of energy transfer per lap at 400kJ. This translates into an extra 85bhp for just under seven seconds, which makes overtaking another vehicle on the track easier and the race much more interesting. Thus although a 0.3s boost to laptimes, the system was ultimately limited in its potential to improve laptimes. Thus no team could create a competitive advantage from a more powerful system. Then the weight of the system created issues, At a time when the wider front slick tires demanded an extreme weight distribution of up to 49% weight on the front axle, the 25+Kg of a KERS system mounted behind the Centre of gravity, the handicapped teams being able to push weight forwards. Most teams dropping or not racing their system cited weight as the main reason for its loss. The 60kW/400kJ limits in Formula 1 will not apply to road cars. Road cars will safely have more power and energy transfer due to their larger weight when compared with racecars, which will provide them with significant benefits. There is more than one type of KERS used in motorsports. The most common is the electronic system built by the Italian company MagnetiMarelli, which is used by Red Bull, Toro Rosso, Ferrari, Renault and Toyota. Although races have been won with this technology, KERS was removed from the 2010 Formula 1 season due to its high cost.

4.2 Ferrari The HY-KERS vetturalaboratorio (experimental vehicle) is an example of how Ferrari is approaching the development of hybrid technology without losing sight of the performance traits and driving involvement that have always exemplified its cars. Weighing about 40 kg, the compact, tri-phase, high-voltage electric motor of the HYKERS is coupled to the rear of the dual-clutch 7-speed F1 transmission. It operates through one of the transmission’s two clutches and engages one of the two gearbox primary shafts. Thus power is coupled seamlessly and instantaneously between the electric motor and the V12. The U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

16 Kinetic Energy Recovery System electric motor produces more than 100 hp as Ferrari’s goal was to offset every kilogram increase in weight by a gain of at least one hp.

Fig. 4.4 Ferrari VetturaLaboratorio HY-KERS Under braking the electric drive unit acts as a generator, using the kinetic energy from the negative torque generated to recharge the batteries. This phase is controlled by a dedicated electronics module which was developed applying experience gained in F1 and, as well as managing the power supply and recharging the batteries, the module also powers the engine’s ancillaries (power steering, power-assisted brakes, air conditioning, on-board systems) via a generator mounted on the V12 engine when running 100 per cent under electric drive. It also incorporates the hybrid system’s cooling pump.This experimental vehicle thus maintains the high-performance characteristics typical of all Ferraris while, at the same time, reducing CO2 emissions on the ECE + EUDC combined cycle by 35 per cent.

4.3 Volvo Volvo is experimenting with a Formula 1 style drive system which is claimed to cut fuel consumption by up to 20 per cent. The Swedish car maker is about to start road trials using a vehicle fitted with a kinetic energy recovery system, or KERS. Volvo is using the technology not only to improve performance but also to aid fuel economy. It uses a flywheel fitted to the rear axle which captures energy from the car under braking. The flywheel spins at up to 60,000rpm and when the car moves away the stored energy is released to drive the rear wheels via a special transmission. Volvo says that when allied to U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

17 Kinetic Energy Recovery System stop/start systems which switch off a car's engine when it comes to rest in traffic, the Flywheel KERS reduces fuel urban fuel consumption by some 20 per cent.

Fig 4.5 Volvo Flywheel KERS System Layout Volvo aims to develop a complete system for kinetic energy recovery. Tests in a Volvo car will get under way in the second half of 2011. This technology has the potential for reducing fuel consumption by up to 20 per cent. What is more, it gives the driver an extra horsepower boost, giving a four - cylinder engine acceleration like a six-cylinder unit. They claim that the system can have the effect of adding an extra 80 horsepower to an engine which could significantly improve acceleration. They are not the first manufacturer to test flywheel technology, but nobody else has applied it to the rear axle of a car fitted with a combustion engine driving the front wheels. The Swedish carmaker expects cars with flywheel technology to reach the showrooms within a few years if the tests and technical development go as planned.

4.4. Jaguar 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 U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

18 Kinetic Energy Recovery System 20 percent. The consortium, which includes automakers like Ford and engineering firms like Prodrive, sees a market for flywheel hybrids among luxury automakers. During braking, a small continuously variable transmission (CVT) mounted on the rear differential transfers the kinetic energy to a flywheel. When the driver applies the accelerator, the flywheel returns the energy through the CVT to the wheels, providing a boost of 60 kilowatts for around 7 seconds. The flywheel spins at up to 60,000 rpm.

Fig. 4.6 Jaguar Land Rover developing a flywheel-hybrid system Jaguar is testing its purely mechanical flywheel system, which reportedly weighs 143 pounds, in an XF sedan. Jaguar says it is superior to battery-electric hybrid systems because flywheels are smaller, cheaper and more efficient. Instead of converting kinetic energy into electricity that is stored in a battery, the CVT transfers the energy directly to the flywheel and then back to the wheels.

4.5 Porsche At 2011 North American International Auto ShowPorsche 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. U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

19 Kinetic Energy Recovery System

Fig. 4.7Porsche 918 RSR Concept Car The electric motors are not powered by a set of batteries, as in a traditional hybrid, rather they take their power from an inertial flywheel mounted where the passenger seat would be on a road car and spinning at up to 36,000rpm. That's spun up by momentum when the car brakes and, when the driver hits a button, that momentum is converted to give an acceleratory boost.

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

20 Kinetic Energy Recovery System

5. OUR PROJECT 5.1 Abstract: Kinetic Energy Recovery System (KERS) is a system for recovering the moving vehicle's kinetic energyunder braking and also to convert the usual loss in kinetic energy into gain in kinetic energy.When riding a bicycle, agreat amount of kinetic energy is lost while braking, making start up fairly strenuous. Here we used mechanical kineticenergy recovery system by means of a flywheel to store the energy which is normally lost during braking, and reuse itto help propel the rider when starting. The rider can charge the flywheel when slowing or descending a hill and boostthe bike when accelerating or climbing a hill. The flywheel increases maximum acceleration and nets 10% pedal energysavings during a ride where speeds are between 12.5 and 15 mph.

5.2Introduction KERS is a collection of parts which takes some of the kinetic energy of a vehicle under deceleration, stores this energyand then releases this stored energy back into the drive train of the vehicle, providing a power boost to that vehicle. Forthe driver, it is like having two power sources at his disposal, one of the power sources is the engine while the other isthe stored kinetic energy. Kinetic energy recovery systems (KERS) store energy when the vehicle is braking and returnit when accelerating. During braking, energy is wasted because kinetic energy is mostly converted into heat energy orsometimes sound energy that is dissipated into the environment. Vehicles with KERS are able to harness some of thiskinetic energy and in doing so will assist in braking. By a proper mechanism, this stored energy is converted back intokinetic energy giving the vehicle extra boost of power.There are two basic types of KERS systems i.e. Electrical andMechanical. The main difference between them is in the way they convert the energy and how that energy is storedwithin the vehicle. Battery-based electric KERS systems require a U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

21 Kinetic Energy Recovery System number of energy conversions each withcorresponding efficiency losses. On reapplication of the energy to the driveline, the global energy conversion efficiencyis 31–34%. The mechanical KERS 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 efficiencyof an electric system. This design of KERS bicycle was motivated by a desire to build a flywheel energy storage unit as a proof of concept.On a flat road, the cyclist can maintain a fixed cruising speed to get from point to point. Globally all roads are flat withimpediments such as intersections, cars, and turns that force the cyclist to reduce speed, then accelerate.

Fig.5.1 Flywheel KERS Bicycle

A flywheel can temporarily store the kinetic energy from the bicycle when the rider needs to slow down. The energystored in the flywheel can be used to bring the cyclist back up to cruising speed. In this way the cyclist recovers theenergy normally lost during braking. In addition to increased energy efficiency, the flywheel-equipped bicycle is morefun to ride since the rider has the ability to boost speed.The flywheel bicycle model is shown in figure 5.1.

5.3KERS Bicycle Working: A crank wheel connected to the rear wheels always rotates the clutch plate, connected in the flywheel axle. This isbeing achieved by using chain transmission at a specified gear ratio, crank to clutch sprocket helps us to increase theoverall speed of flywheel. Now at a time when a U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

22 Kinetic Energy Recovery System speed reduction is required, clutch is applied which makes the contactbetween the clutch and flywheel. Then the flywheel starts rotating, also the speed of bicycle is decreased. Thus aregenerative braking system is achieved. On course energy is stored in flywheel. In case the brake has to be appliedfully then after flywheel rotations clutch is disengaged and the brake is applied. Now when we again rides the bicycleduring which we would apply clutches at this time as rear wheel rotation is lesser compared to flywheel the energy getstransmitted from the flywheel to the wheels. Now also we can reduce the overall pedaling power required in course ofoverrides by having clutch fully engaged. We can reduce overall pedaling power by 10 per cent. Also situation arisessuch as traffic jam, down climbing a hill where we do not intend to apply brake fully. For such cases we can apply oursmart braking system which would allow us to decelerate and allow us to boost acceleration after this during normalriding and distance that can be covered by pedaling can also improve. During normal rides situations may arise we need to reduce the speed without braking fully such as traffic jams takingturns etc. we can store the energy that would normally be wasted due to speed reduction by the application of clutch. When the clutch is engaged that time due to initial engage the flywheel rotation consumes energy which would result inspeed reduction thus a braking effect. After some instances the energy is being stored in the flywheel this can bereused by the engage of clutch plate and energy transfer from the flywheel occurs whenever the rotation is high enoughto rotate rear wheel. Thus if sudden braking then applied we can disengage the flywheel connections so that flywheelenergy is not wasted and going to take ride the speed of rear wheel is null and hence engage would help in returning theenergy from the flywheel to rear wheel. While riding downhill we always use braking for allowing slowdown. This isthe best case where we can store maximum amount of energy in our flywheel. The flywheel can be engaged for fulldownhill ride and after all for some distance we need not ride the bicycle which would be done by the flywheel. This isthe main advantage area of KERS bicycle. During long drive the engage can be made full time. This will help inreducing the overall pedaling effort. It has been found that the pedaling power can be reduced by 10 per cent duringlong drives. Also this would help in avoiding pedaling effort at some points of ride. The complete KERS bicycle isshown in figure 5.2 below. U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

23 Kinetic Energy Recovery System

Fig. 5.2 KERS Bicycle

5.4Design Requirements: There are many requirements that need to be met to produce a product that is both feasible and optimal. There are alsosome constraints, both geometric and engineering that also need to be satisfied.

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

24 Kinetic Energy Recovery System Fig. 5.3 Rear Assembly

Fig. 5.4 Flywheel Assembly

The following list describes theserequirements and constraints:  Store energy while braking This is the main requirement and the overall objective of the device and must be suitable to meet the rider’s needs.  Return energy to start up Once the energy is stored in the device, it is necessary to have a simple way to release this energy back to theuser in positive way. This can be accomplished with an innovative chain drive system.  Must fit on a bicycle U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

25 Kinetic Energy Recovery System This is one of the most difficult constraints to achieve and most important because we are dealing with suchconfined spacing. The objective is to fit the flywheel and accessories in the bicycle.  Light weight The importance of having a light weight design is driven by the rider’s desire to have a bicycle that is moremaneuverable and more portable. This is also a direct trade off with how much energy can be stored in theflywheel.  Good stopping range The stopping range is important because this product needs to be usable in real life situations. This componentcan be optimized to have the shortest stopping distance using dynamic analysis.  Good stopping force The force required to stop is dependent on the stopping range and the comfort levels of    

the rider. It is alsorelated to the possible flywheel features. Inexpensive and affordable This product must be able to make a profit and be desirable. Safe to user and environmentally friendly Safety is always a very important aspect whenever there is a consumer product. Economical The product economical and the products for this design must be cheaply available. Reliable It is important to have a product that is reliable and this requirement will affect the

normal bicycling process and must be easy to use.  Manufacturability In order to make anything economical, it needs to be manufacturability, hence the important of having a product that can be made easily and cheaply.  Aesthetically pleasing This is not a requirement that needs to be taken heavily, but the design should always have nice look about it, because looks will persuade the rider.  Modular Having a device that can be adapted to existing bicycles is essential to be added to the existing ones so that it’seasier to adopt. This also can reduce other types of manufacturing costs.  Should not hinder normal riding To have a successful accessory for a bicycle, the ride should not feel a noticeable change in the riding performance or in the normal riding motion. A device that impedes the normal riding experience would beconsidered undesirable. U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

26 Kinetic Energy Recovery System  Controlled release The energy that is released back to the user must be done in a safe and manageable fashion. This can be a consideration after the prototype is completed.

5.5 Bill of Material S.NO. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

PART NAME Bicycle with gears Flywheel Chain ring Chain ring adapter Sprocket spacer Spacer Washer Chain ring nut & bolt Hub body Structural tube Bearing Axle tab Axle Sprocket Lock ring Flange nut

NO. OF PARTS 1 1 1 1 1 4 5 1 2 2 2 1 1 1 1

5.6 Fabrication Process: A. Frame Modification The frame modification is the first part of the fabrication that has to be done. The frame has to be modified by addingsteel tube. One end has to be welded at the handle end and the other at the rear wheel centre. The frame should haveenough strength so as to carry the flywheel and the additional forces that comes to play. The modification should nothinder normal riding. Also the modified frame should have enough space in order to accommodate flywheel and clutchassemblies. This is shown in figure 5.5 below.

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

27 Kinetic Energy Recovery System

Fig. 5.5 Frame Modified

B. Flywheel The flywheel has to be bored centrally in order to place a ball bearing so that flywheel can rotate over the axle. Alsoflywheel has to be selected so that the selected weight does not affect the bicycle physics and riding performance of therider. The performance of KERS system mainly depends upon the flywheel selection. For clutch accessories thereshould be provisions in the flywheel which is used to deliver and release energy from flywheel. The works done onflywheel is shown in figure 4 below.

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

28 Kinetic Energy Recovery System

Fig. 5.6 Works on Flywheel C. Clutch A clutch has to be provided so as to control the power delivery and release from the flywheel. This can be achieved byproviding a clutch plate that is linearly moved to and fro by applying a lever mechanism incorporated with a springassembly for providing return mechanism. Linear clutch movements have to be made possible. For this purpose twocylindrical rods can be used. One end of the each rod was variably cut. This variable length is female part of another. One part of this is fixed near the frame side. This can be achieved by welding the part. Another part is made rotatory. This part can be rotated by applying force on it from lever via cable. This moves only partially over fixed one and firstly this is hold in position by a spring arrangement. D. Axle The axle has to be made so as to carry the flywheel and clutch units. The flywheel can be inserted after bearing is addedto it and if variable diameter is provided on axle within midpoint the flywheel can be made to be inserted from one end and it automatically locks in the middle of the axle over which it rotates. Also the clutch units sequentially clutch plate and the fixed and moving rods along with its mechanism can be mounted over the axle. The provision for axle placement is provided in the modified frame. The axle should withstand the forces coming to play. U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

29 Kinetic Energy Recovery System

E. Sprocket Two sprockets have to be used. The gear ratio is to be taken in to account here. One sprocket with higher number ofteeth is to be selected and other having lesser number of teeth. The larger sprocket is to be placed at the rear wheel endand smaller sprocket at the axle end. This is to ensure that we can provide larger flywheel rotations so that energy storage increases.

Fig. 5.7 Two spockets

The flowchart of the fabrication process is shown in the figure below.

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

30 Kinetic Energy Recovery System


Dept. of Mechanical Engineering

31 Kinetic Energy Recovery System By adopting the cheaper and lighter flywheel system (the ideal solution if it could be made to fit into the no-refueling era cars), a more powerful boost, and limiting the number of activations in a race it would cover all the bases it needs to. It would be affordable for the all the teams, deliver performances as well as being a more interesting race variable. The sidepod solution is quite unique, and has given us a new envelope to try to drive performance to the rear of the car. We need to keep thinking out-of-the-box. Compared to ten or 20 years ago, it's really quite staggering what can be delivered given the restrictions we have now – it's a tribute to imaginative thinking.

Thus we are coming to the end of the elaborate study of KERS going through their advantaged limitation relevance and finally to the modification. To sum up this report we have gone through sophisticated concept which will surely be much raved in coming days. Also it would be a great showcase of technology which could have a major impact on the car industry in years to come. In the future the technology could also be used on buses, trains, and wind power generation.

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

32 Kinetic Energy Recovery System


1. 2. 3. 4. 5. 6. 7.

8. Siddharth K. Patil., “Regenerative Braking System in Automobiles”, International Journal of Research in Mechanical Engineering&Technology vol.2, pp.45-46,2012

U.I.E.T., K.U.K.

Dept. of Mechanical Engineering

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