LOVELY PROFESSIONAL UNIVERSITY

REGENERATIVE BREAKING SYSTEM

CAPSTONE PROJECT

AMIT KUMAR MISHRA, YOGESH THUWAL & SUNIL KUMAR 4/25/2012

Under of the Research Supervisor of Er. Praveen Kumar

Designation: Asst. Professor

Lovely Professional University

Phagwara, Punjab.

LOVELY PROFESSIONAL UNIVERSITY

REGENERATIVE BREAKING SYSTEM

CAPSTONE PROJECT

AMIT KUMAR MISHRA, YOGESH THUWAL & SUNIL KUMAR

4/25/2012

Under of the Research Supervisor of Er. Praveen Kumar

Designation: Asst. Professor

Lovely Professional University

Phagwara, Punjab.

CERTIFICATE

This is to certify that AMIT KUMAR MISHRA, YOGESH THUWAL & SUNIL

KUMAR Registration no. 10807466, 10810462 & 10806948 resp. has completed capstone

project titled, “REGENERATIVE BREAKING SYSTEM” under my guidance and

supervision. To the best of my knowledge, the present work is the result of her original

investigation and study. No part of the dissertation has ever been submitted for any other

degree at any University.

The dissertation is fit for submission and the partial fulfilment of the conditions for the award

of degree of programme B.tech (M.E)

Signature and Name of the Research Supervisor

Designation

School

Lovely Professional University

Phagwara, Punjab. Date :

DECLARATION

We, AMIT KUMAR MISHRA, YOGESH THUWAL & SUNIL KUMAR students of

B.TECH under Department of MECHANICAL ENGINEERING of Lovely Professional

University, Punjab, hereby declare that all the information furnished in this capstone project

report is based on my own intensive research and is genuine.

This report does not, to the best of our knowledge, contain part of our work which has been

submitted for the award of our degree either of this university or any other university without

proper citation.

Date: 25-04-2012 Amit Kumar Mishra (10807466) Yogesh Thuwal (10810462) Sunil kumar (10806948)

ACKNOWLEDGEMENT

We owe a great many thanks to a great many people who helped and supported us during this

working period.

Our deepest thanks to Assistant professor, Mr. Praveen Kumar, the Guide of the project for

guiding and correcting various documents of mine with attention and care. He has taken pain

to go through the project and make necessary correction as and when needed.

A heart full thanks and appreciation to the helpful people at LPU for their support.

Finally, we would like to express my deepest gratitude to my parents and family, without

whom we are nothing, to provide us great opportunities, everlasting support, big

encouragement and lots of love.

TABLE OF CONTENTS

1. ABSTRACT

2. INTRODUCTION

TRADITIONAL BRAKING SYSTEMS

REGENERATIVE BRAKING SYSTEM

3. REGENERATIVE BRAKING IN DC SYSTEMS

PRINCIPLE

BRAKING AND SAFETY

4. ENERGY IT RECOVERS

5. HOW DOES IT WORK?

6. WHEN DOES IT WORK?

7. CONSTRUCTION

8. WORKING OF MODEL

9. CALCULATION OF RPM

10. BENEFITS:

11. BARRIERS:

12. SUCCESS FACTORS:

13. ECONOMIC CRITERIA

14. APPLICATION

15. REGENERATIVE BREAK IN CYCLE?

16. SUMMARY

17. REFERENCES

CONTENTS

S.

No.

TOPIC PAGE NO.

1 INTRODUCTION 1

2 REGENERATIVE BRAKING IN DC SYSTEMS 2

3 ENERGY IT RECOVERS 3

4 CONSTRUCTION 4

5 WORKING 7

6 WORKING OF MODEL 7

7 CALCULATION 8

8 BENEFITS 9

9 BARRIERS: 11

10 SUCCESS FACTORS 12

11 ECONOMIC CRITERIA 12

12 APPLICATION 13

13 REGENERATIVE BREAK IN CYCLE 15

14 SUMMARY 17

15 REFERENCES 19

List of figures

Fig no:

Title

Page no:

Fig 1 Connection diagram

4

Fig 2 Tyre of medium size

5

Fig 3 One motor – AC : 0.3amp, 220 Volts,9500 rpm

5

Fig 4 One stepper DC motor

6

Fig 5 LED‟s

6

Fig 6 One 12mm pulley

7

Fig 7 2008 BMW M3 uses regenerative braking

13

Fig 8 Regenerative braking in trains

13

REGENERATIVE BRAKES

1. ABSTRACT

In the effort to produce greener cars numerous processes have been examined that effect fuel

consumption. One process is braking – since, traditional braking wasted 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.

2. INTRODUCTION

Traditional Braking Systems

In a traditional braking system, pressing on the brake pedal causes a pair of brake pads in

each wheel to come into contact with the surface of a brake rotor. This contact produces

friction, slowing down and eventually stopping the vehicle. The friction itself produces heat

as an energy as a by product. Automotive engineers and designers generally perceive heat as

a loss. This is the reason why, especially in high performance cars, brake cooling systems

such as air dams are employed to dissipate heat from the brakes so that they can quickly

regain their efficiency.

Regenerative Braking System

In a battery-powered electric vehicle, regenerative braking is the conversion of the vehicle‟s

kinetic energy into chemical energy stored in the battery, where it can be used later to drive

the vehicle.

“Braking” because it also serves to slow the vehicle.

“Regenerative” because the energy is recaptured in the battery where it can be used again.

The kinetic energy stored in a moving vehicle is related to the mass and speed of the vehicle

by the equation

E = ½mv². ------------------- (1)

If car is twice as heavy it has twice the kinetic energy and if it is moving twice as fast it has

four times the kinetic energy.

Any time your car slows down the kinetic energy stored in the vehicle has to go somewhere.

There is always some kinetic energy consumed by the rolling resistance, mechanical friction,

and aerodynamics of your car. These bits of energy go into heating the road, the surrounding

air, and various spinning parts in your car. But the vast majority of the kinetic energy is

converted into heat by your brake pads when you stomp on the brakes

In the world of automobiles, the faster you want to accelerate; the more power is required to

overcome the air resistance and drag. Regenerative braking is a way to save and store some

of these energies used to move the car. Regenerative braking can help to keep these losses to

a minimum and can even help to increase fuel efficiency.

So Regenerative Braking can be use in the wasted energies in a traditional braking set up, but

this energy can also be stored for use later on in batteries or capacitors. This essentially

recharges electric cars while on the move to further boost their driving range, but is now

being adaptive to boost petrol car green credentials and even act as a performance boost for

sporting models. There are a number of different ways of doing this, but the most common is

where electric motors are used as generators to produce the electricity under braking loads.

Reversing the power delivery process, to power generation, Pneumatics, hydraulics or

rotating flywheels can also be used.

3. Regenerative braking in DC systems

In DC supply systems (1,5 and 3 kV) high recovery rates are only achievable under

favourable conditions.

Principle:

The energy put into accelerating a vehicle and into moving it uphill is “stored” in the vehicle

as kinetic and potential energy. In vehicles with electric traction motors a great part of this

energy can be reconverted into electric energy by using the motors as generators when

braking. The electric energy is transmitted “backwards” along the conversion chain and fed

back into the catenary. This is known as regenerative braking.

Braking and safety

Braking safety requires installation of additional brakes besides regenerative brakes, for two

reasons:

Braking power of 3-phase AC motors is of the same order as power installed for

traction. Additional braking power is therefore indispensable and provided by

mechanical (e.g. disk brakes) or other dissipative brakes. Typically brakes are

blended, i.e. when the driver brakes, first the regenerative brakes are apply, if more

power is needed especially in unforeseen situations additional brakes are applied.

4. Energy it recovers

Unfortunately, “your mileage may vary” applies to regenerative as well. The amount of

energy you can recover depends on how and where you drive. The energy conversion

efficiencies from chemical to electrical (battery), DC current to AC current (inverter),

electrical to mechanical (motor), and torque to force (transmission and wheels) are all quite

high and work just as efficiently returning energy into the battery. The bigger problem is

aerodynamic losses and higher speeds and rolling friction of the tires. These both act to slow

the car, but the energy dissipated cannot be recovered. Even though the battery-to-wheel

conversion efficiency is pretty good (up to 80%), the energy makes a full circle back into the

battery and it gets converted twice for a net efficiency of at most 80% * 80% = 64%.

5. How does it work?

Due to the simplicity of the AC induction motor‟s single moving part, the vehicle does not

experience the engine compression braking of a traditional internal combustion engine.

Instead, the advanced algorithms in the motor controller give it complete control of the motor

torque for both driving and regenerative braking. A torque command is derived from the

position of the throttle pedal. The motor controller converts this torque command into the

appropriate 3-phase voltage and current waveforms to produce the commanded torque in the

motor in the most efficient way. The torque command can be positive or negative. When the

torque serves to slow the vehicle then energy is returned to the battery and we have

regenerative braking!

The motor and controller can deliver the torque command at any operating speed, including 0

mph. This means that we can regen the car to a complete stop.

But as a practical matter, the kinetic energy of a slowly moving car is low enough that very

little energy is put back into the battery as the car comes to a stop. In fact, the last little bit of

slowing the vehicle down generates such a small amount of energy that it does not even cover

the fixed losses in the inverter and motor.

6. When does it work?

There are a number of goals and restrictions when using regenerative braking.

Safety: Negative torque applied to the rear wheels can cause a car to become unstable.

Since regen braking is a source of negative torque, use of the traction control system

to limit regen if the rear wheels start to slip.

Performance: Regenerative braking can enhance the driving experience in ways not

available with a traditional internal combustion engine (ICE). Reasion is having that

instant positive and negative torque command right at your toes really make you feel

in control.

7. Construction

Requirements:-

Plywood

Wires

Fevi-quick

Nail

Scissor

Markers

Connection diagram:-

Fig:1 connection diagram for regenerative system

Parts USED

Fig:2 Tyre of medium size

Fig 3 One motor – AC : 0.3amp, 220 Volts,9500 rpm

Fig 4 One stepper DC motor

Fig 5 LED‟s

Fig 6 One 12mm pulley

One steel shaft

Ball bearings

Battery 9 volts

8. WORKING

In the above model the working is as follows:

Firstly, we start our Motor and a belt is connected between motor and pulley.

This pulley is mounted on shaft and tyre is arranged on this shaft.

Tyre is moving simultaneously with pulley arrangement.

When we apply brake that is mounted on stepped motor, when this brake is come in

contact with the tyre.

Results, in breaking of tyre and movement of motor (stepped) in opposite direction

and produce electricity.

This electricity can used in glowing LED‟s or battery.

9. CALCULATION OF RPM

Given Data:

FORMULA USED :

RPM OF PULLEY =(RPM OF MOTOR * DIA OF MOTOR)/(DIA OF PULLEY)

= (9500*0.025)/(0.12)

RPM OF PULLEY =1978

As, tyre is mounted on Pulley shaft

therefore, For dia. 0.25 m for tyre

RPM OF TYRE =(RPM OF PULLEY * DIA OF PULLEY)/(DIA OF TYRE)

=(1978*0.12)/0.25

RPM OF TYRE =949

10. Benefits

Wear of mechanical brakes

The use of regenerative brakes reduces wear and maintenance of mechanical brakes.

It may also be possible to reduce the complexity, weight and cost of mechanical

brakes. Since regenerative braking works without friction, no wearing parts are

present.

reduced CO2 emissions

The advantages of regenerative braking are clear-cut as effectively, drivers can enjoy

„something for nothing‟. They will notice no difference to regular braking and yet

enjoy better fuel economy, reduced CO2 emissions and able to save energy.

The regenerative braking technology employed in Delhi Metro Rail Corporation

(DMRC) is different from Calcutta Metro and several other metros worldwide, which

employ conventional rheostat braking system, where kinetic energy of the de-

accelerating Rolling Stock is dissipated into heat energy. The energy recovered not

only remains unutilised but contribute additionally to the heat load, which has to be

extracted by air-conditioning, resulting into additional expenditure.

The choice made

by DMRC for using regenerative braking technology displays the environmental

consciousness of its Management. DMRC is expected to earn carbon credit for

effecting reduction in Green House Gases reduction. DMRC has projected a

conservative estimate of 51250 MWhrs of annual energy saving on account of

regenerative barking on all trains of its existing network. This saving of electrical

energy translates into 41000 Certified Emission Reductions or in other words saving

of 41000 tons of CO2 from being injected into atmosphere.

Effectively the electric motor works in reverse during the process of

regenerative braking. The motor acts as the generator to recharge batteries

with the energy that would normally be lost. This reduces the reliance on fuel,

boosting economy and lowering emissions.

Contribution of the technology to protection of the environment :

The effects of regenerative braking on air quality depend mainly on the

way the electricity is produced. In general, the introduction of

regenerative braking on electric trains and subway trains will have no

direct effect on the local air quality. However, lowering the electricity

demand will lower the emission of air pollutants, like NOx, SO2 and

particulate matter in power generation, if power generation is based on

fossil fuels.

For diesel powered locomotives, hybridization can have a positive

direct effect on air quality, depending on the usage pattern.

Locomotives used solely on a marshalling yard can achieve very high

reductions in emissions, due to frequent need for braking. However,

the reduction in local air pollution will be limited when the locomotive

is used in long-haul freight trains.

Regenerative braking is used on hybrid gas/electric automobiles to recoup some of the

energy lost during stopping. This energy is saved in a storage battery and used later to

power the motor whenever the car is in electric mode.

Regenerative braking systems will soon be vital in the sport of motor racing. All cars

must become hybrid by 2013 according to regulations by the FIA with regenerative

braking used alongside a kinetic energy recovery system.

11. Barriers:

Since the technology is relatively new, it is inherently going to be more prone

to malfunction than the standard old disc brakes that have served for decades.

Here are the two most common problems that are being reported.

Funny "Feel"

Many drivers report a funny or strange feel in the resistance of their brake pedal when

engaging the brake. Others report feeling an actual acceleration before they begin to

decelerate. The funny feel in the brake's pedal resistance can be due to air in the brake

lines. However, it should only be a one-time occurrence.

Pedal to the Floor

There have been reports of drivers applying the brake pedal, only to find it goes all the way to

the floor. There is no resistance, and the vehicle does not slow down or stop. Many times, if

the driver again tries to engage the brake a couple of seconds later, the brake engages as

normal. This can be a very scary experience. Some drivers have never gotten the brake to

engage and when they needed them and, thinking quickly, used the emergency brake to safely

stop the vehicle. Some have also been told when the vehicle was taken to the shop that the

malfunction was due to air in the brake lines.

Low voltage

Due to the low voltage in DC systems (1,5 or 3 kV) transmission losses are high. This

reduces the probability of having vehicle braking and vehicle accelerating close enough to

each other to allow for an effective transmission considerably. Without additional technology

to improve the situation, substantial recovery rates can only be achieved in dense suburban

networks.

Voltage limits

It may happen that during break the voltage increases beyond the limits foreseen by the

standards. In this case voltage is automatically cut off and no recovery is possible.

Insufficient braking power

The power of regenerative brakes is roughly the same as the one installed for traction. For

many situations (trains running late, bad track conditions, unexpected stop signals) this is not

sufficient. In this case regenerative brakes are blended with dissipative brakes or completely

replaced by them.

Generally, EMUs have a better regenerative braking performance than loco-hauled trains,

since more axles are powered. The higher the motor power and the more axles are powered,

the more energy may be recovered

12. Success factors:

Inverter units for substations

By installing thyristor inverters in substations of DC systems, a feeding back of recovered

braking energy into the public mains becomes a possibility. This can considerably increase

recuperation rates in suburban or regional DC systems.

Energy storage

On-board or stationary energy storage are another way of enhancing recuperation rates in DC

systems.

Automatic train control

Automatic driver-less systems offer the possibility of introducing a timetable which is

optimised for regenerative braking by synchronising the acceleration and braking phases of

subsequent trains.

13. Economic criteria

Vehicle - fix costs: low

Recuperation is a common feature in modern stock with no additional costs. If on-

board storage technologies are implemented to raise recuperation rates, vehicle fix costs are

very high.

Vehicle - running costs: significant reduction

Reduced energy costs and maintenance costs through reduced wear in mechanical

brakes.

14. Application

2008 BMW M3 uses regenerative braking

Regenerative braking in trains

Fig 7

Employing regenerative braking in trains can lead to substantial CO2 emission

reductions, especially when applied to full stop service commuter trains (8 – 17%) and to

very dense suburban network trains (~ 30%).

When regenerative braking is employed, the current in the electric motors is reversed,

slowing down the train. At the same time, the electro motors generate electricity to be

returned to the power distribution system. Regenerative breaking is a mature technology.

It can be more easily applied to AC powered trains than to DC powered systems. In DC

powered railway systems usually higher investment costs are needed.

Railway systems working with AC power can implement regenerative braking with

almost no additional costs. Also the implementation of regenerative braking in diesel

powered locomotives poses no obstacle. Virtually all locomotives are diesel-electric, so

the capacity to do regenerative braking is available.

Regenerative braking is a mature technology. Within Europe, there is still a

considerable difference between countries in the share of rolling stock that is

equipped with regenerative braking, but the share is relatively high already.

Regenerative breaking is relatively standard in new trains.

It is also used in major new high-speed trains. For example the new N700 series of the

Shinkansen in Japan, which became operational in February 2009, uses regenerative

braking. However, friction brakes are still needed as backup in the case that the

regenerative brakes fail. It is possible to use regenerative braking on these high speed

trains because most cars have their own electric motors, this is in contrast to trains in

which only the locomotive has electric motors.

15. REGENERATIVE BREAK IN CYCLE?

“is it worth the effort and expense to put regenerative braking on an electric bicycle?”.

regenerative braking system has to be able to recover 10% of whatever the capacity of your

battery is, over the time it normally takes you to discharge the battery completely.

Taking 16 Amp-hour, 37 Volt lithium polymer battery system as our example. It has a

total usable energy of about 500 Watt-hours. A typical energy use for one our our EMD units

on a bicycle is about 15 Wh per mile. So the range with 500 Watt-hours “in the tank” would

be 33 miles.

So, what would it take for a regen system to recover 10% of that, or 50 Watt-hours, thereby

extending our range by 3.3 miles?

The obvious source for recovering energy would be stopping at stop signs or traffic lights.

Assume a total weight of bike plus rider of 220 lbs (100 kg), moving at about 16 mph

(25 km/h), it's a simple physic problem to calculate the energy available to be

recovered by slowing the bike to zero mph. It works out to about 2400 Joules.

A Joule is a tiny unit. 3600 Joules make one Watt-hour. So 2400 Joules is .67 Watt-

hours. So how many stops would it take from 16 mph to recover 50 Watt-hours at .67

Watt-hours per stop? The answer is 75.

we can't recover 100% of the kinetic energy because all real systems are less than

100%efficient. A reasonable efficiency would be more like 75%. If we factor that in, we can

only recover .67 times .75, or .50 Watt-hours per stop.

Now were talking 100 stops to recover 10% of the energy in the battery.

If we divide 100 stops into 33 miles, that's an average of 1742 feet between stops for the

entire 33 miles. A typical city block is about 500 feet, so that corresponds to a full stop every

3 city blocks. In a congested urban area that might happen. More typically stops will be

further apart.

Also, under such conditions bicyclists often don't stop completely at intersections, but rather

roll through at low speed. A third or more of the energy that would be returned to the battery

is instead retained as momentum.

This is more efficient than regenerative braking since retained momentum doesn't incur

mechanical and electrical losses.

There's another factor here we haven't considered. If we have 1800 Joules (2400 Joules at

75% efficiency) that can be recovered, we have to put them somewhere. We put them in the

battery.

Batteries are always designed to be charged at a certain maximum rate. Charge them above

the designed rate, and they will suffer from a shortened service life. In the case of our 16Ah

lithium ion polymer battery, we recommend charging at no more than 3 Amps to maximize

life. Three Amps at 37 Volts, is 111 Joules per second. If we have 1800 Joules to put in the

battery, it will take 1800 divided by 111 or 16.2 seconds to do so. Taking 16 seconds to stop

from 16 miles per hour, is a very slow stop.

A more typical, but still relaxed stop, would be 3 or 4 seconds. If we've got four seconds at

111 Joules per second charge rate, we can only put 444 Joules or .12 Watt-hours into the

battery per stop.

Taking this new number into account, we would need 416 stops to get 50 Watt-hours back.

That's 418 feet average between stops over 33 miles. More than 1 stop per city block.

At a more reasonable 2000 feet average between stops, we will stop 87 times in 33 miles and

recover 10.5 Watt-hours of energy, or 2.1% of the battery's total energy. That corresponds to

7 tenths of a mile of added range.

The newest battery technology on the market, lithium iron phosphate, sometimes

abbreviated as LiFePO4 has the ability to be rapid charged. A bicycle sized LiFePO4

battery can absorb 1800 Joules in 3 or 4 seconds. The trade-off is that you lose about

25% capacity compared to the same weight in lithium ion polymer batteries. Still,

LiFePO4 has other advantages, such as extremely long life, so it is a reasonable

alternative.

With LiFePO4, 87 stops will recover 44 watt-hours. That's still less than 10%, though it's not

too bad at a bit less than 9 %.

16. SUMMARY

Sort of range that can be gained from this feature

The typical stated range gain for regenerative braking is about 10%. AC Propulsion states as

high as 30%, US Electrical measured as high as 20+%, Toyota RAV4 owners report as high

as 25%. This would obviously be more effective in city driving rather than highway where

little braking occurs.

Regenerative braking is possible on a series wound DC-motor

Yes, but it is difficult and can be dangerous to implement. Some controllers, such as the

ZAPI H2 have regen abilities built in but some have questioned the controller's reliability.

Early 90's Soleq brand EV's were DC and had regen built in.

Regen is possible on a Permanent Magnet DC motor

Regenerative braking is easier with a permanent magnet motor because the magnets do not

need to be energised. Regenerative braking is achieved by having the controller reverse the

terminals to the motor so that current flows in the opposite direction. Since these motors are

also brushed they suffer from the same advanced timing problems when used at voltages

greater than 96V. Typically though PM motors are smaller anyway and therefore run with

neutral timing and lower voltages. Thus many motorcycles and small EVs run regen using

PM motors at less than 96V.

Hybrid gas/electric automobiles now use a completely different method of

braking at slower speeds. While hybrid cars still use conventional brake pads

at highway speeds, electric motors help the car brake during stop-and-go

driving. As the driver applies the brakes through a conventional pedal, the

electric motors reverse direction. The torque created by this reversal

counteracts the forward momentum and eventually stops the car.

But regenerative braking does more than simply stop the car. Electric motors

and electric generators (such as a car's alternator) are essentially two sides of

the same technology. Both use magnetic fields and coiled wires, but in

different configurations. Regenerative braking systems take advantage of this

duality. Whenever the electric motor of a hybrid car begins to reverse

direction, it becomes an electric generator or dynamo. This generated

electricity is fed into a chemical storage battery and used later to power the car

at city speeds.

17. REFERENCES

http://www.mathworks.com/products/simulink/

http://www.seminarprojects.com/Thread-design-and-fabrication-of-

regenerative-braking-system#ixzz1d6mijsQQ

www. siucautomotive.com

http://opensiuc.lib.siu.edu/auto_pres/

http://www.transportation.anl.gov/software/PSAT/index.html

http://www.saabnet.com/tsn/press/041203.html