Exercise equipment for electrical energy generation- A Report

i

EXERCISE EQUIPMENT

FOR ELECTRICAL

ENERGY GENERATION

ii

ABSTRACT

The intention of this project is to design a renewable energy source based

around a piece of exercise equipment. The energy expended in a typical

workout at the gym is usually wasted in the mechanics of the equipment. This

project harnessed the mechanical energy of the machine and converted it to

electrical energy using a generator-based system. The exercise equipment,

attached to the shaft of the generator. Thus produced electrical energy is used in

powering a piece of equipment such as lamp or a computer while exercising.

This report will introduce the project and present all applicable information

regarding the design, development, and the final product.

This project will help one develop engineering skills while learning about

a clean way of generating electricity. The modern challenge faced with the

global energy situation is the growing energy demand and the strong

dependence on unsustainable fossil fuels. Another concurrent issue is the

adverse health and socio-economic implications of adult obesity. This Human

Power Generation project, which uses metabolized human energy to generate

electrical power, could potentially address both these challenges.

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TABLE OF CONTENTS

CHAPTER NO: TITLE PAGE NO.

ABSTRACT v

LIST OF FIGURES ix

LIST OF TABLE xi

LIST OF GRAPH xii

1 INTRODUCTION 1

1.1 THE ENERGY CHALLENGE 2

1.2 SYSTEM DESIGN OVERVIEW 4

2 DESIGN OF OVERALL PROJECT 6

2.1 BLOCK DIAGRAM 6

2.2 PROJECT METHODS 9

2.3 PRIME MOVER 10

2.3.1 BICYCLE AND PULLEY 11

2.4 ALTERNATOR 13

2.4.1 ALTERNATOR COMPONENTS 14

2.4.2 CHARACTERSISTICS AND

LIMITATION 17

2.5 VOLTAGE REGULATOR 18

2.5.1 ZENER DIODE REGULATOR 20

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2.6 RECTIFIER 22

2.6.1 THREE PHASE DIODE RECTIFIER 23

2.6.2 RECTIFIER OUTPUT SMOOTHING 25

2.6.3 RECTIFIER OPERATION 27

2.7 BATTERY 28

2.7.1 BATTERY CHARGER 30

2.7.2 CHARGING AND DISCHARGING

PROCESS OF BATTERY 31

2.8 INVERTER 32

2.8.1 MOSFET POWER INVERTER 33

2.8.2 WORKING OF MOSFET POWER

INVERTER 36

2.9 STEP-UP TRANSFORMER 39

2.10 ADDITIONAL SOURCE FOR THE

BATTERY 41

2.10.1 DIODE RECTIFIER FOR POWER

SUPPLY 41

2.10.2 SINGLE PHASE FULL WAVE

RECTIFIER 43

3 LITERATURE REVIEW 45

3.1 A BRIEF HISTORY OF HUMAN POWER

GENERATION 45

3.2 THE POTIENTIAL OF HUMAN POWER 47

3.3 CALORIES TO WATTS 49

3.4 MODERN APPLICATIONS 50

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4 IMPLEMENTATION AND RESUSLT 53

4.1 KEY REQUIREMENTS 53

4.2 ELECTRICAL SCHEMATIC DIAGRAM 54

4.3 ELEMENT SPECIFICATION 55

4.4 PROJECT ANALYSIS 55

4.5 RESULT 57

5 CONCLUSION 58

REFERENCES

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LIST OF FIGURES

FIGURE NO: TITLE PAGE NO.

1.1 PICTORIAL REPRESENTATION OF

OVERALL DESIGN 4

2.1 BLOCK DIAGRAM OF OVERALL

PROJECT DESIGN 6

2.2 PRIME MOVER SETUP FOR ALTERNATOR 11

2.3 AC GENERATOR PICTORIAL AND

SCHEMATIC DRAWING 14

2.4 TYPES OF ROTORS USED IN ALTERNATOR 16

2.5 ALTERNATOR WITH VOLTAGE REGULATOR 18

2.6 ZENER DIODE REGULATOR 20

2.7 THREE PHASE AC FULL WAVE RECTIFIER 23

2.8 THREE PHASE AC INPUT, HALF AND FULL WAVE

RECTIFIED DC OUTPUT WAVEFORMS 24

2.9 RECTIFIER OUTPUT SMOOTHING GRAPH 25

2.10 RC FILTER RECTIFIER 25

2.11 RECTIFICATION CIRCUIT 27

2.12 BLOCK DIAGRAM OF INVERTER 33

2.13 SCHEMATIC DIAGRAM OF MOSFET INVERTER 33

2.14 STEP-UP TRANSFORMER 39

2.15 SINGLE-PHASE FULL WAVE RECTIFIER WITH

FILTER CAPACITOR 41

2.16 BLOCK DIAGRAM OF REGULATED

POWER SUPPLY 42

2.17 OPERATION DURING POSITIVE HALF CYCLE 43

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2.18 OPERATION DURING NEGATIVE HALF CYCLE 43

2.19 FULL WAVE BRIDGE RECTIFIER WITH

CAPACITOR FILTER 44

4.1 SCHEMATIC DIAGRAM OF OVERALL DESIGN 54

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LIST OF TABLES

TABLE NO. TITLE PAGE NO.

3.1 ENERGY CONSUMPTION RATES OF COMMON

HUMAN ACTIVITIES 48

3.2 MAXIMUM POWER GENERATION CAPABILITY

FOR SOME HUMAN ACTIVITIES 48

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LIST OF GRAPHS

GRAPH NO. TITLE PAGE NO.

1.1 FOSSIL FUEL CONSUMPTION OF DIFFERENT

COUNTRIES 3

4.1 VOLTAGE Vs SPEED 56

4.2 CURRENT Vs SPEED 57

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CHAPTER - 1

INTRODUCTION

The field of energy conservation is becoming an increasingly

notable subject of research among the scientific community today. The

intention of this project is to build a straight forward human powered

generator from a used bicycle and to use it to power light bulbs,

blenders, cell phones, laptops, and other small appliances. This project

will help one develop engineering skills while learning about a clean

way of generating electricity.

Over the past decade, scientists and engineers around the world

have been designing unprecedented energy-harvesting systems, drawing

power from a variety of sources. One of the most creative and unlimited

sources available is the kinetic energy produced from human exercise.

Although recent designs of energy-harvesting exercise equipment have

been introduced into the market, these systems are costly and do not

produce a noticeable output of power. These systems need to be

improved and designed for maximum power output, cost-efficiency, and

marketability. Engineered to be used for retrofitting an existing exercise

machine, this project includes an efficient yet controllable power storage

and distribution system.

The objective of this project is to design a renewable energy

source based around a piece of exercise equipment. Also, people who

are interested in minimizing environmental impacts and those who want

to preserve the environment will use this type of electrical energy

generation thereby reducing the emission of CO2 to the atmosphere.The

energy expended in a typical workout at the gym is usually wasted in the

mechanics of the equipment. This project harnessed the mechanical

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energy of the machine and converted it to electrical energy using a

generator-based system. The exercise equipment will be attached to the

shaft of the generator. Thus produced electrical energy is used in

powering a piece of equipment such as lamp or a computer while

exercising.

1.1 THE ENERGY CHALLENGE

The world’s energy consumption is at an all time high with the

demand continuously increasing. This situation brings up several

challenges that need to be addressed.

Depletion due to finite availability of non-renewable energy

sources, e.g. fossil fuels

Environmental pollution, e.g. with coal use in power plants

Increasing population, especially in developing countries

which lack resources for clean energy.

Global warming with the related climate changes and

adverse implications

These challenges have been reason for much controversy in the

developed world; however, recent investigations have also shown a

much more basic challenge of availability in the less developed parts of

the world.

Data from the World Bank obtained as recently as 2014 estimated

that about 25.9% of the world’s population (greater than 1.81 billion

people) has no access to electricity. Larger numbers include those that

have very limited access to electricity. Further, most countries with the

lowest values for percent of population with electricity also have low

values of urban population percentage.

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In terms of meeting the energy demand, data shows the high

dependence the world has overall on fossil fuels. Fossil fuels are known

to be non-renewable, having formed over millions of years of

decomposition of prehistoric biological forms such as plant matter and

the dinosaurs. The rate at which modern society is consuming these

resources is far quicker, however, risking the depletion of this resource.

Furthermore, the manner in which the resource is consumed is known to

produce pollutants (e.g. Carbon Monoxide (CO)) and green house gases

(e.g. Carbon Dioxide (CO2)) in our environment. Carbon Dioxide

emissions have been steadily growing through the combustion of fossil

fuels as needed in transportation, power generation and otherwise. One

of the main reasons why this is a critical problem is that the world

heavily depends on these fossil fuels currently to feed its energy

demands. Fig 1.1 illustrates the level and trends of fossil fuel use as

compared to total energy consumption over time in a few countries and

the world overall .

Fig 1.1 Fossil fuel consumption of different countries

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Statistics shown here illustrate how the world on average depends

majorly on fossil fuels to supply energy. The trend in this parameter is

also of concern as the value has been stable around 80% for the past 15

years. The United States shows a slow decline but is still above the

world average. The trend of the most populous countries, China and

India, can also cause distress as the fossil fuel dependence is increasing

at a rapid rate over time. In the case of China, the value has superseded

that of the United States as of 2006. Therefore, it is established that with

the various energy challenges faced today, renewable energy sources

must be seriously investigated. Particularly, the feasibility of low-cost,

low maintenance and simple methods of providing energy to remote

areas should be studied. Such technology could not only help provide an

alternative to fossil fuel in developed countries, but also serve the

growing needs of developing countries in a responsible way.

1.2 SYSTEM DESIGN OVERVIEW

Fig 1.2 Pictorial representation of overall design

We designed and constructed an entirely unique electric

generation system that fuses both form and function into a cost-effective

and convenient solution. Using a stationary bicycle to generate

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electricity and charge a 12 volt battery, we obtain an output power of

approximately 60 watts – plenty of power for lights, an amplifier, an

iPod charger, and any unforeseen additional loads the student group may

attach later. The system provides about 5 hours of fully-loaded use, and

requires the equivalent for charging.

The system is comprised of several subsystems that will work

collectively to efficiently produce the desired 50 to 150 watts of power.

The first subsystem is the mechanical connection which is will

transfer the kinetic energy from pedaling to the generator.

The second subsystem is the electrical generator. This

subsystem transfers the rotational movement created when

bicycle is in use to the rotor of a generator which will in turn

output an AC voltage.

The third subsystem is the rectifier, which convert AC power

to DC. The fourth subsystem,thebattery and the battery

charger.

The Charge Controller adjusts the output to a single lead acid

battery to optimize the use of the generated energy. This

component will play a major factor in the efficiency of the

system.

The fifth subsystem is the inverter which convert the 12V DC

to 12 V AC.

A sixth subsystem is the step up transformer which step up the

12V AC to 230V AC supply.

The seventh and final subsystem is the additional power

supply for the battery when bicycle is not in use, which

consistsof single phase AC supply, rectifier and a step down

transformer.

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CHAPTER- 2

LITERATURE REVIEW

2.1 A BRIEF HISTORY OF HUMAN POWER GENERATION

In 1817 Baron von Drais invented a walking machine that would

help him get around the royal gardens faster: two same-size in-line

wheels, the front one steerable, mounted in a frame which you straddled.

The device was propelled by pushing your feet against the ground, thus

rolling yourself and the device forward in a sort of gliding walk. The

machine became known as the Draisienne or hobby horse

The next appearance of a two-wheeled riding machine was in

1865, when pedals were applied directly to the front wheel. This

machine was known as the velocipede ("fast foot"), but was popularly

known as the bone shaker, since it was also made entirely of wood, then

later with metal tires, and the combination of these with the cobblestone

roads of the day made for an extremely uncomfortable ride.

In 1870 the first all metal machine appeared. (Previous to this

metallurgy was not advanced enough to provide metal which was strong

enough to make small, light parts out of.) The pedals were still attached

directly to the front wheel with no freewheeling mechanism. Solid

rubber tires and the long spokes of the large front wheel provided a

much smoother ride than its predecessor. The front wheels became

larger and larger as makers realized that the larger the wheel, the farther

you could travel with one rotation of the pedals.

Pedaling History has on display even the recent history of the

bicycle in America that we are more familiar with: the "English 3-speed"

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of the '50s through the '70s, the 10-speed derailleur bikes which were

popular in the '70s (the derailleur had been invented before the turn of

the century and had been in more-or-less common use in Europe since),

and of course the mountain bike of right now. There are also many

oddball designs that never quite made it, including the Ingo.

1980-1991 A Los Angeles based company called Luz Co.

produced 95% of the world's solar-based electricity. They were forced to

shut their doors after investors withdrew from the project as the price of

non-renewable fossil fuels declined and the future of state and federal

incentives were not likely. The chairman of the board said it best: "The

failure of the world's largest solar electric company was not due to

technological or business judgment failures but rather to failures of

government regulatory bodies to recognize the economic and

environmental benefits of solar thermal generating plants”. Solar energy

history played a big part in the way society evolved and will continue to

do so. There is a renewed focus as more and more people see the

advantages of solar energy and as it becomes more and more affordable.

Human power has been instrumental in helping solve problems

since ancient times. For example, all tools have historically been human

powered. It is believed that the first human powered device to generate

rotary motion was the potter’s wheel, around 3,500 B.C.E. Later,

devices such as Archimedes� screw allowed efficient transfer of water

from one level to another. The Chinese, after 200 C.E., were found to

use hand cranks to aid in textile manufacturing, metallurgy and

agriculture. After the mid-15th century, the technique of incorporating

flywheels to produce smooth motion proliferated, allowing devices such

as the spinning wheel to gain popularity in Europe.

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Cranks and pedal power became one of the most efficient means

of coupling human power to applications. In the 19th century, the

bicycle’s use of pedals allowed an efficient means of self-transportation.

In parallel with the invention of the electric dynamo in the 19th century,

it is speculated that pedal power was used to generate electric power as

early as then. However, with the burgeoning of the industrial revolution

in the 19th century and forward, human society found other ways of

powering their engineered applications.

Particularly, the availability of cheap and plentiful electricity,

powerful motors and disposable batteries can be attributed to the

decrease in popularity of using human strength. Also, the ethical

implications of having humans produce energy as punishment, as seen in

some prison mills, further diminished the popularity of human sourced

power. It would take until the latter half of the 20th century for science

to seriously reinvestigate this resource.

2.2 THE POTENTIAL OF HUMAN POWER

When the energy intake of humans is considered, a large potential

seems apparent. Considering the standard 2000kcal of daily

consumption (97W of power in, on average), humans take in about

8.368MJ or 2324Wh of energy every single day. This is approximately

the same amount of energy stored in the typical car battery (2400Wh) .

However, the expenditure of energy for common tasks is relatively high

as well as seen in Table 2.1 Also; Table 2.2 shows some values for

maximum power that can be captured as a result of human activity.

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Table 2:1 Energy Consumption Rates of Common Human Activities

Activity Power Consumed (w)

Sleeping 81

Sitting 116

Swimming 582

Sprinting 1630

Table 2.2 Maximum Power Generation Capability for some Human

Activities

Activity Maximum Human Power (w)

Pushing button 0.64

Squeezing handle 12

Rotating crank 28

Riding bike >100

Hence, the available energy that can be captured over a short

period of time is in reality quite limited. To replace just one of the

largest capacity coal power plants in the United States (Arizona Public

Service Co, Palo Verde, AZ) would require approximately the

population of 2 New York City metro areas to be riding human power

generating bicycle :

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The obvious impracticality of this figure shows why the scope

thus far in human power generation has been limited to lower power

applications such as consumer electronics

Producing 1800 watts for a few seconds should be within the

range of the best power lifters and perhaps for up to a minute.

Remember 1 watt means applying a force of 1 newton through a

distance of 1 meter in 1 second. So if you lifted 1 kg, that's 9.8 newtons

of force, about 10newtons, for 1 meter in 1 second, that would be 10

watts. So lifting 180 kg, 1 meter high in 1 second would be 1800 watts.

The best power lifters can do squats of several times their body weight

for 1 rep. Let's say the power lifter weighed 100 kg, about 220 lbs. He

might be able to do 3 times his weight for a single rep. That would be

300 kg. But remember he's actually raising his own weight as well. So

he's actually lifting 4 times his weight, 400 kg for this one rep. For a

male of average height, he might be raising this over a distance of 1

meter. So doing 1800 watts of power for one minute would be like

giving this power lifter a weight of only 60 kg (for a total weight of 180

kg) and doing squats with this light weight for the high number of reps

of 1 per second over one minute. This would be possible for a weight so

much lighter than their usual 1 rep maximum weight.

2.3 CALORIES TO WATTS

First keep in mind that Watts and Calories are two different units

of measurement that can't be directly converted back and forth. However

if you use Watt-Hours instead of just "Watts" you then have a way to

convert to calories. Here are the steps: Convert Watt-Hours to Watt-

Seconds (Joules), then convert Joules to Calories, then adjust Calories

with human body efficiency factor. So for this example let's assume that

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you provide pedal power to a 100 Watt television for one hour. Since

one Joule is equal to one Watts X Seconds you perform dimensional

analysis and get:

100Watt-hours X (3600 seconds / 1 Hour) = 360,000 J

Now use the conversion factor:

1 cal = 4.184 J to convert Joules to Calories

360,000 J / 4.184 = 86,042 Calories

When you look at the label of Oreo cookies or other food items at

the store, the term "Calories" is really (kilo-Calories). So you divide by

1000 to get 86 Calories. Assuming that your body is about 25% efficient

when cycling you divide by 0.25: Calories burned running a 100 Watt

Television for 1 hour = 86 / 0.25 = 344 which is about equivalent to one

piece of pizza.

2.4 MODERN APPLICATIONS

Today, human power has made sort of a comeback with many

applications where it can be of use and the reason to investigate

alternative energy. A novel feeling of empowerment is recognized when

people are able to do things for which they had to rely on machines

previously. So much so, that the idea of powering solely from human

energy exists as a technical challenge. For example, the American

Society of Mechanical Engineers (ASME) holds the Human Powered

Vehicle Challenge (HPVC) competition annually for encouraging higher

education students to construct and compete with single-driver

prototypes power by the driver alone. Further, the Royal Aeronautical

Society has various challenges for the Kramer’s prizes in human

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powered flight. The end goal of this initiative is to qualify such an

endeavor to be a competitive sport, possibly a part of the Olympics.

Human power has also been found to be uniquely good at

providing energy generation in isolated situations. For example, the

development of hand-operated axial flux generators which can be useful

for dismounted soldiers, search and rescue operation in case of natural

disasters, relief workers in remote regions and field scientists. The study

demonstrates how 60W can be maintained from the generator for

different applications while maintaining a lightweight design for

portability. Further, provides a good example of applying human power

in remote areas of developing countries. In 1991, at the time of the

study, many rural parts of India lacked any access to electricity. Further,

fossil fuel or solar/wind energy generation required skill in operation

and maintenance along with monetary resources that were unavailable.

Human energy was determined to be simple, dependable, required

low capital, and reliable for the application of desalinating local water.

The successful implementation of a pedal powered system in the rural

area produced a sustainable 100W to power the desalination system.

This let clean water be available to the people locally, avoiding the need

to walk 2km daily as done previously. This localized generation of

electricity has also made human power an excellent method for micro-

power generation.

Theoretical analyses have been done to show that brisk walking

motion can produce up to 5-8W, adequate for basic wearable computing.

Recent research shows the performance of three methods to perform this

extraction. Summary of current progress in piezoelectric generator

technology shows power generation capabilities of up to 8400μW.

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Further, small-scale electromagnetic generators are a little harder to

manufacture but can produce power in the order of mW. The

development of a electrostatic generator which uses microball

movement induced by low frequency human motion to generate at least

40μW. Such output power may seem relatively negligible but it has

potential in partially or completely removing the need for batteries,

making portable designs lighter, smaller and longer lasting. This is

especially promising for applications such as implantable and wearable

electronics, ambient intelligence, condition monitoring devices, and

wireless sensor networks.

Hence, it is seen that human power generation has multiple

applications in modern society. It can be useful when users are isolated

as possible with natural disaster, military deployment or being in a

remote area. It also provides for an intuitive, easy to implement and

relatively low cost design which is particularly useful in rural areas of

developing nations where skill in operating equipment and investment

capital is limited. Acquisition of energy via no deliberate human effort is

also possible which could be useful for various novel portable

electronics applications. Furthermore, it can allow for power generation

to be done socially, removing the feeling of deliberate effort while

increasing the power output significantly. The thought of using human

energy as an alternative and renewable energy source is gaining

popularity to the level that businesses have formed around converting

exercise equipment such as stationary bikes and ellipticals to electricity

generators.

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CHAPTER -3

DESIGN OF OVERALL PROJECT

3.1 BLOCK DIAGRAM

A simple block diagram of the overall project design is shown in

Fig 3.1

Fig 3.1 Block diagram of overall project design

The basic design for the bicycle powered generator is to have a

bicycle on a fixed stand, and then when the bicycle is pedaled, the

spinning motion of the rear tire is used to produce mechanical energy

directly into a generator. The kinetic energy from the exercising machine

is given to the alternator through chain and belt drive. The belt is

directly coupled to the alternator, so while exercising alternator also

rotate.

DC supply is given to the alternator using a battery, thus the rotor

produce flux. While exercising, the alternator starts to rotate and

produce three phase AC supply.

The three phase AC supply is convert into DC through a three

phase bridge rectifier. The rectified DC supply is given to the voltage

regulator. Voltage regulator regulates the voltage to 12V. This 12V is

used to charge battery and the same DC supply is fed to an inverter. The

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inverter is made is made with MOSFET and driver circuit. The output of

the inverter is 12V AC supply with a frequency of 50 Hz. This AC

supply is step up to 230 V by using step up transformer.

When the exercise machine is not used, the main supply is used to

charge the battery. For that charging step down transformer and bridge

rectifier is used. The output of the transformer is 12V AC. This 12 V AC

is converted to DC by using diode bridge rectifier. The output from the

diode rectifier is directly connected to the battery. So the battery also

charges while the exercise machine is not in use. In our project, we are

using a 40 W incandescent lamp as load.

This project has various different design paths to complete our

product while meeting the majority objectives. This means we will have

to implement and compare our different designs to insure the best

product based on our set of objectives. These paths have changed as we

progressed through our project, and there were a few foreseen methods

that we expand upon in the design section.




directly into a generator. Alternator is the device by which mechanical

energy is converted into electrical energy. It is D.C. generator for

generating D.C. voltage at output. Rectifier circuit It is a device which

converts A.C. voltage into D.C. voltage. Some A.C. harmonics produced

by D.C. generator with pulsating modulation of waves which is not in

regular modulation, so for getting regular modulation of waves, rectifier

circuit is used Filter circuit at the output of rectifier.

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DC voltage is not in pure form some A.C. components are in

there so for purification of it, Shunt capacitor filter circuit is used. Filter

is a circuit which minimizes of removed the undesirable A.C.

component of the rectifier output & allows only the D.C. component to

reach at output. Charging circuit It is the circuit which is used for

charging the discharged battery. Voltage limiting circuit:- It is also

called as voltage regulator circuit. Here, for voltage regulation of output

voltage, zener diode is used.

Voltage regulator is the circuit which eliminates or reduced

variations in the D.C. output voltage or rectifier and filter circuit are

called Voltage Regulator. Battery It is the source of D.C. voltage. It is

the device where we want to store the D.C. voltage or it gives the D.C.

source whenever we want. Inverter we are using electronic inverter. The

function of electronic inverter is to convert D.C. to A.C. In our project

we are generating 12 volt D.C. supply to convert 12 volt D.C. to 230

volt A.C. with the help of electronic inverter unit.

The function of inverter is to take the 12 volt D.C. and switching

the 12 volt D.C. and give the step-up transformer convert 12 volt

switching supply to 230 volt A.C. supply. It is most common part of

inverter. If an AC voltage is produced, a full bridge rectifier will be

necessary to produce the DC voltage. This DC voltage can then be used

immediately or stored via a battery array.

The first decision is selecting a bill of materials for each design

path. This will help determine the ultimate product affordability. We

must decide whether to use an alternator or dynamo to convert the

bicycles mechanical energy to AC or DC, respectively. While an

alternator is easier to find and purchase with many functioning units

17

available in scrap yards, they also tend to be less efficient in the output

of DC power compared to a dynamo.

Another design factor that must be implemented and compared is

the coupling of the bicycle wheel to either the alternator or dynamo

rotor. One option is to use two contacting wheels to connect the two

components. This option is a bit simpler to implement and take very

little upkeep to maintain; however, the efficiency of the contact is

relatively low due to slippage losses and frictional losses. A more

efficient yet expensive design would be to have the wheel and the

alternator/dynamo be connected via a rotary belt, similar to a car belt

system. There are bound to be various other obstacles and design

methods to be implemented as the project progresses, and will be

observed and recorded as they occur.

3.2 PROJECT METHODS

This project has various different design paths to complete our

product while meeting the majority objectives. This means we will have

to implement and compare our different designs to insure the best

product based on our set of objectives. These paths have changed as we

progressed through our project, and there were a few foreseen methods

that we expand upon in the design section.




directly into a DC voltage. If an AC voltage is produced, a full bridge

rectifier will be necessary to produce the DC voltage. This DC voltage

can then be used immediately or stored via a battery array. If a constant

DC voltage is required by the using a voltage regulator may be

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necessary to change the varying DC voltages produced from the varying

bicycle speed to a constant DC voltage for certain utilities or battery

array.

The first decision is selecting a bill of materials for each design

path. This will help determine the ultimate product affordability. We

must decide whether to use an alternator or dynamo to convert the

bicycles mechanical energy to AC or DC, respectively.

While an alternator is easier to find and purchase with many

functioning units available in scrap yards, they also tend to be less

efficient in the output of DC power compared to a dynamo. Another

design factor that must be implemented and compared is the coupling of

the bicycle wheel to either the alternator or dynamo rotor. One option is

to use two contacting wheels to connect the two components.

This option is a bit simpler to implement and take very little

upkeep to maintain; however, the efficiency of the contact is relatively

low due to slippage losses and frictional losses. A more efficient yet 15

expensive design would be to have the wheel and the alternator/dynamo

be connected via a rotary belt, similar to a car belt system. There are

bound to be various other obstacles and design methods to be

implemented as the project progresses, and will be observed and

recorded as they occur.

3.3 PRIME MOVER

All generators, large and small, ac and dc, require a source

of mechanical power to turn their rotors. This source of mechanical

energy is called a prime mover. Prime movers are divided into two

classes for generators-high-speed and low-speed. Steam and gas turbines

are high-speed prime movers, while internal-combustion engines, water,

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and electric motors are considered low-speed prime movers. The type of

prime mover plays an important part in the design of alternators since

the speed at which the rotor is turned determines certain

characteristics of alternator construction and operation.

Fig 3.2 Prime Mover Setup for Alternator

3.3.1 BICYCLE AND PULLEY

A bicycle is designed to convert human energy into mechanical

energy for transportation purposes. The mechanical energy is then

translated into electrical energy through the use of a drive train turning a

motor. To maximize the efficiency of both conversions is essential to

obtaining the maximum power output. The first conversion is from

human energy or muscle energy into mechanical energy.

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The bicycle is an efficient and robust method to convert between

the two types of energy. It is an efficient design that provides seating for

the user as well as pedals and drive train that are easily activated. There

are few moving parts and the simplicity of design is proven.

Pedaling is the most efficient way of utilizing power from human

muscles. Pedal power enables a person to drive devices at the same or

higher rate as that achieved by hand cranking, but with far less effort and

fatigue. The human musculature is concentrated in our legs and the

bicycle set-up allows for harnessing the maximum output.

The stationary power generation on bicycles has been skipped

over in past research but with the rising cost of other power generation,

reliance on human power generation will become more important;

furthermore, the bicycle is a universal symbol of transportation in all

types of countries especially developing ones. We can find bicycles

everywhere and the robustness of the simple mechanical system makes

the learning curve essentially zero.

The rotational nature of the bicycle drive train or more

specifically the pedals is a steady style of movement. The constant

driving of the pedals become more constant when reaching the drive

train since there is rotational inertia to smooth out any subtle changes in

the speed. The rear wheel therefore becomes an ideal prime mover for

electrical generation; we would need to connect an alternator and rear

wheel though either direct contact or a belt system. The user is able to

start softly and increase the resistance as momentum is gained.

When the bicycle stabilizes and gains more speed, then the user

down-shift thereby increasing perceived resistance and outputs more

power. The same approach can be used by the user of our stationary

21

power generation set-up. This factor comes into play further when

developing the motor for the bicycle design.

A pulley is a wheel on an axle that is designed to support

movement of a cable or belt along its circumference. Pulleys are used in

a variety of ways to lift loads, apply forces, and to transmit power.

Round belts Round belts are a circular cross section belt designed to run

in a pulley with a 60 degree V-groove. Round grooves are only suitable

for idler pulleys that guide the belt, or when (soft) O-ring type belts are

used.

3.4 ALTERNATOR

Here the alternator is used to charge the battery and to power the

electrical system when the bicycle is pedaling. The last practical option

to implement for the bicycle system was to use a standard car alternator.

This seems to be the most reasonable motor for the design, as car

alternators are widely available worldwide for relatively low costs when

purchased as a used part.

An alternator is an electrical generator that converts mechanical

energy to electrical energy in the form of alternating current. For reasons

of cost and simplicity, most alternators use a rotating magnetic field with

a stationary armature. Occasionally, a linear alternator or a rotating

armature with a stationary magnetic field is used. In principle,

any AC electrical generator can be called an alternator, but usually the

term refers to small rotating machines driven by automotive and other

internal combustion engines. An alternator that uses a permanent

magnet for its magnetic field is called a magneto. The alternator consists

of two main parts, rotor and the stator.

22

3.4.1 ALTERNATOR COMPONENTS

A typical rotating-field ac generator consists of an alternator and a

smaller dc generator built into a single unit. The output of the alternator

section supplies alternating voltage to the load. The only purpose for the

dc exciter generator is to supply the direct current required to maintain

the alternator field. This dc generator is referred to as the exciter. A

typical alternator is shown in fig 3.3 view A; figure 3.3, view B, is a

simplified schematic of the generator.

Fig 3.3 AC generator pictorial and schematic drawings.

23

The exciter is a dc, shunt-wound, self-excited generator. The

exciter shunt field (2) creates an area of intense magnetic flux between

its poles. When the exciter armature (3) is rotated in the exciter-field

flux, voltage is induced in the exciter armature windings. The output

from the exciter commutator (4) is connected through brushes and slip

rings (5) to the alternator field. Since this is direct current already

converted by the exciter commutator, the current always flows in one

direction through the alternator field (6). Thus, a fixed-polarity magnetic

field is maintained at all times in the alternator field windings. When the

alternator field is rotated, its magnetic flux is passed through and across

the alternator armature windings (7).

The armature is wound for a three-phase output, which will be

covered later in this chapter. Remember, a voltage is induced in a

conductor if it is stationary and a magnetic field is passed across the

conductor, the same as if the field is stationary and the conductor is

moved. The alternating voltage in the ac generator armature windings is

connected through fixed terminals to the ac load.

There are two types of rotors used in rotating-field alternators.

They are called the turbine-driven and salient-pole rotors.

As you may have guessed, the turbine-driven rotor shown in

Fig 3.4 , view A, is used when the prime mover is a high-speed turbine.

The windings in the turbine-driven rotor are arranged to form two or

four distinct poles. The windings are firmly embedded in slots to

withstand the tremendous centrifugal forces encountered at high speeds.

24

Fig 3.4 Types of rotors used in alternators

The salient-pole rotor shown in figure 3.4, view B, is used in low-

speed alternators. The salient-pole rotor often consists of several

separately wound pole pieces, bolted to the frame of the rotor.

If you could compare the physical size of the two types of rotors

with the same electrical characteristics, you would see that the salient-

pole rotor would have a greater diameter. At the same number of

revolutions per minute, it has a greater centrifugal force than does the

turbine-driven rotor.

To reduce this force to a safe level so that the windings will not be

thrown out of the machine, the salient pole is used only in low-speed

designs.

25

3.4.2 CHARACTERISTICS AND LIMITATIONS

Alternators are rated according to the voltage they are designed to

produce and the maximum current they are capable of providing. The

maximum current that can be supplied by an alternator depends upon the

maximum heating loss that can be sustained in the armature. This

heating loss (which is an I2R power loss) acts to heat the conductors, and

if excessive, destroys the insulation. Thus, alternators are rated in terms

of this current and in terms of the voltage output - the alternator rating in

small units is in volt-amperes; in large units it is kilovolt-amperes.

Once the finger poles and shaft are removed, the coil of the rotor

can be rewound with thinner wire more times. From Farraday’s

equation, , we find that as N (number of turns)

increases, ε (electromagnetic force) increases proportionally. With the

higher EMF, we produce more power from less rotor rotations. In other

words, with a rewrapped rotor we can produce more power with lower

RPMs. While more current will be produced at lower RPMs this is

because the EMF is much bigger, which in turn will give the users

another problem, the EMF-produced resistance. An EMF in a motor is

not a problem until you are the one actually supplying the rotation of the

shaft. A higher EMF means the user will experience a higher resistance

in their pedaling. This ―inductance hump� of starting to pedal will tire

the user greatly if a full field is being produced by the stator. To resolve

this issue a few different ideas were implemented to reduce the pedaling

resistance in the alternator.

26

3.5 VOLTAGE REGULATOR

A voltage regulator circuit for an alternator includes voltage

responsive circuitry having a zener diode. The regulator will maintain a

pre-determined charging system voltage level. When the system voltage

decreases the regulator strengthens the magnetic field and thereby

increases the alternator output voltage. When the system voltage

increases the regulator weakens the magnetic field and thereby decreases

the alternator output voltage.

Fig 3.5 Alternator with voltage regulator

Zener diodes are especially used on applications with sensitive

electronic components. These can prevent major damage caused by

voltage peaks due to sudden discharges. In 12V systems, Zener diodes

with a voltage range 24V - 32V are used and in 28V systems the range is

36V - 44V.

When ac generators are operated in parallel, frequency and

voltage must both be equal. Where a synchronizing force is required to

27

equalize only the voltage between dc generators, synchronizing forces

are required to equalize both voltage and speed (frequency) between ac

generators. On a comparative basis, the synchronizing forces for ac

generators are much greater than for dc generators. When ac generators

are of sufficient size and are operating at unequal frequencies and

terminal voltages, serious damage may result if they are suddenly

connected to each other through a common bus. To avoid this, the

generators must be synchronized as closely as possible before

connecting them together.

The output voltage of an alternator is best controlled by regulating

the voltage output of the dc exciter, which supplies current to the

alternator rotor field. This is accomplished as shown in Fig 2.5, by a

zener diode regulator of a 28 volt system connected in the field circuit of

the exciter. The zener diode regulator controls the exciter field current

and thus regulates the exciter output voltage applied to the alternator

field.

The only difference between the dc system and the ac system is

that the voltage coil receives its voltage from the alternator line instead

of the dc generator. In this arrangement, a three phase, step down

transformer connected to the alternator voltage supplies power to a three

phase, full wave rectifier. The 28 volt, dc output of the rectifier is then

applied to the zener diode voltage regulator. Changes in alternator

voltage are transferred through the transformer rectifier unit to the zener

diode. This controls the exciter field current and the exciter output

voltage. The exciter voltage antihunting or damping transformer is

similar to those in dc systems and performs the same function.

28

The DC output voltage from the half or full-wave rectifiers

contains ripple superimposed onto the DC voltage and that as the load

value changes so to does the average output voltage. By connecting a

simple zener stabilizer circuit as shown below across the output of the

rectifier, a more stable output voltage can be produced.

3.5.1 ZENER DIODE REGULATOR

Zener Diodes can be used to produce a stabilized voltage output

with low ripple under varying load current conditions. By passing a

small current through the diode from a voltage source, via a suitable

current limiting resistor, the zener diode will conduct sufficient current

to maintain a voltage drop of output voltage.

Fig 3.6 Zener Diode Regulator

In the Fig 3.6, the resistor, RS is connected in series with the zener

diode to limit the current flow through the diode with the voltage

source, VS being connected across the combination. The stabilized output

voltage Vout is taken from across the zener diode. The zener diode is

connected with its cathode terminal connected to the positive rail of the

DC supply so it is reverse biased and will be operating in its breakdown

29

condition. Resistor RS is selected so to limit the maximum current

flowing in the circuit.

With no load connected to the circuit, the load current will be

zero, ( IL = 0 ), and all the circuit current passes through the zener diode

which in turn dissipates its maximum power. Also a small value of the

series resistor RS will result in a greater diode current when the load

resistance RL is connected and large as this will increase the power

dissipation requirement of the diode so care must be taken when

selecting the appropriate value of series resistance so that the zener’s

maximum power rating is not exceeded under this no-load or high-

impedance condition.

The load is connected in parallel with the zener diode, so the

voltage across RL is always the same as the zener voltage, ( VR = VZ ). There

is a minimum zener current for which the stabilization of the voltage is

effective and the zener current must stay above this value operating

under load within its breakdown region at all times. The upper limit of

current is of course dependent upon the power rating of the device. The

supply voltage VS must be greater than VZ.

One small problem with zener diode stabilizer circuits is that the

diode can sometimes generate electrical noise on top of the DC supply

as it tries to stabilize the voltage. Normally this is not a problem for most

applications but the addition of a large value decoupling capacitor across

the zener’s output may be required to give additional smoothing.

Then to summarize a little. A zener diode is always operated in its

reverse biased condition. A voltage regulator circuit can be designed

using a zener diode to maintain a constant DC output voltage across the

load in spite of variations in the input voltage or changes in the load

30

current. The zener voltage regulator consists of a current limiting

resistor RS connected in series with the input voltage VS with the zener

diode connected in parallel with the load RL in this reverse biased

condition. The stabilized output voltage is always selected to be the

same as the breakdown voltage VZ of the diode.

3.6 RECTIFIER

Rectifier is an electrical device that converts alternating

current (AC), which periodically reverses direction, to direct

current (DC), which flows in only one direction. The process is known

as rectification. Physically, rectifiers take a number of forms,

including vacuum tube diodes, mercury-arc valves, copper and selenium

oxide rectifiers, semiconductor diodes, silicon-controlled rectifiers and

other silicon-based semiconductor switches. Historically, even

synchronous electromechanical switches and motors have been used.

Early radio receivers, called crystal radios, used a "cat's whisker" of fine

wire pressing on a crystal of galena (lead sulfide) to serve as a point-

contact rectifier or "crystal detector".

Rectifiers have many uses, but are often found serving as

components of DC power supplies and high-voltage direct current power

transmission systems. Rectification may serve in roles other than to

generate direct current for use as a source of power.

Because of the alternating nature of the input AC sine wave, the

process of rectification alone produces a DC current that, though

unidirectional, consists of pulses of current. Many applications of

rectifiers, such as power supplies for radio, television and computer

equipment, require a steady constant DC current (as would be produced

by a battery). In these applications the output of the rectifier is smoothed

by an electronic filter

Rectifier circuits may be single

the most common number of phas

domestic equipment are single

very important for industrial applications and for the transmission of

energy as DC (HVDC

3.6.1 THREE PHASE DIODE RECTIFIER

Single-phase rectifiers are commonly used for power supplies for

domestic equipment. However, for most industrial and high

applications, three-phase

phase rectifiers, three

circuit, a full-wave circuit using a center

wave bridge circuit.

Fig 3.7

31

). In these applications the output of the rectifier is smoothed

electronic filter (usually a capacitor) to produce a steady current.

Rectifier circuits may be single-phase or multi-phase (three being

the most common number of phases). Most low power rectifiers for

domestic equipment are single-phase, but three-phase rectification is


HVDC).

HREE PHASE DIODE RECTIFIER

phase rectifiers are commonly used for power supplies for

domestic equipment. However, for most industrial and high

phase rectifier circuits are the norm. As with single

phase rectifiers, three-phase rectifiers can take the form of a half

wave circuit using a center-tapped transformer, or a full

7 Three phase AC full-wave rectifier

). In these applications the output of the rectifier is smoothed

(usually a capacitor) to produce a steady current.

phase (three being

es). Most low power rectifiers for

phase rectification is


phase rectifiers are commonly used for power supplies for

domestic equipment. However, for most industrial and high-power

rectifier circuits are the norm. As with single-

phase rectifiers can take the form of a half-wave

tapped transformer, or a full-

rectifier

Fig 3.8 Three phase AC input, half and full

For a three-phase full

average output voltage is

32

phase AC input, half and full-wave rectified DC output

waveforms

phase full-wave diode rectifier, the ideal, no

average output voltage is

......(2.1)

wave rectified DC output

the ideal, no-load

3.6.2 RECTIFIER OUTPUT SMOOTHING

Rectifiers are normally used in circuits that require a steady

voltage to be supplied.To provide a steady DC output. The raw rectified

DC requires a smoothing

be smoothed so that it can be used to power electronics circuits without

large levels of voltage variation.

Fig 3

Producing steady DC from a rectified AC supply requires a

smoothing circuit or

a reservoir capacitor

the rectifier. There is still an

supply frequency for a half

where the voltage is not completely smoothed.

33

RECTIFIER OUTPUT SMOOTHING



DC requires a smoothing capacitor circuit to enable the rectified DC to


large levels of voltage variation.

Fig 3.9 Rectifier Output Smoothing Graph

roducing steady DC from a rectified AC supply requires a

filter. In its simplest form(Fig 3.10) this can be just

reservoir capacitor or smoothing capacitor, placed at the DC output of

the rectifier. There is still an AC ripple voltage component at the power

supply frequency for a half-wave rectifier, twice that for full

where the voltage is not completely smoothed.

Fig 3.10 RC-Filter Rectifier



capacitor circuit to enable the rectified DC to


roducing steady DC from a rectified AC supply requires a

this can be just

or smoothing capacitor, placed at the DC output of

voltage component at the power

rectifier, twice that for full-wave,

34

For a given load, a larger capacitor reduces ripple but costs more

and creates higher peak currents in the transformer secondary and in the

supply that feeds it. The peak current is set in principle by the rate of rise

of the supply voltage on the rising edge of the incoming sine-wave, but

in practice it is reduced by the resistance of the transformer windings. In

extreme cases where many rectifiers are loaded onto a power

distribution circuit, peak currents may cause difficulty in maintaining a

correctly shaped sinusoidal voltage on the ac supply.

To limit ripple to a specified value the required capacitor size is

proportional to the load current and inversely proportional to the supply

frequency and the number of output peaks of the rectifier per input

cycle. The load current and the supply frequency are generally outside

the control of the designer of the rectifier system but the number of

peaks per input cycle can be affected by the choice of rectifier design.

A half-wave rectifier only gives one peak per cycle, and for this

and other reasons is only used in very small power supplies. A full wave

rectifier achieves two peaks per cycle, the best possible with a single-

phase input. For three-phase inputs a three-phase bridge gives six peaks

per cycle. Higher numbers of peaks can be achieved by using

transformer networks placed before the rectifier to convert to a higher

phase order. To further reduce ripple, a capacitor-input filter can be

used. This complements the reservoir capacitor with a choke (inductor)

and a second filter capacitor, so that a steadier DC output can be

obtained across the terminals of the filter capacitor.

The regulator serves both to significantly reduce the ripple and to

deal with variations in supply and load characteristics. It would be

possible to use a smaller reservoir capacitor and then apply some

35

filtering as well as the regulator, but this is not a common strategy. The

extreme of this approach is to dispense with the reservoir capacitor

altogether and put the rectified waveform straight into a choke-input

filter.

The advantage of this circuit is that the current waveform is

smoother and consequently the rectifier no longer has to deal with the

current as a large current pulse, but instead the current delivery is spread

over the entire cycle. The disadvantage, apart from extra size and

weight, is that the voltage output is much lower – approximately the

average of an AC half-cycle rather than the peak.

3.6.3 RECTIFIER OPERATION

Fig 3.11 rectification circuit

36

• Two diodes are connected to each stator lead. One positive the

other negative.

• Because a single diode will only block half the the AC voltage.

• Six or eight diodes are used to rectify the AC stator voltage to

DC voltage.

• Diodes used in this configuration will redirect both the positive

and negative polarity signals of the AC voltage to produce DC voltage.

This process is called ‘Full - Wave Rectification’.

At first you can see current pass through to the rectifier as it goes

to the battery. In the second, you can see the return path. Now, current

passes through to the rectifier however, this time current has the

opposite polarity. In second circuit you can see the new return path.

Even though it enters the rectifier at a different location, current goes to

the battery in the same direction.

3.7 BATTERY

Battery is essential to supply DC power for the alternator rotor

and for the storage of generated power. An electric battery is a device

consisting of one or more electrochemical cells that convert stored

chemical energy into electrical energy. Each cell contains a positive

terminal, or cathode, and a negative terminal, or anode. Electrolytes

allow ions to move between the electrodes and terminals, which allows

current to flow out of the battery to perform work. Battery we used is

12V, 10 Ah rating.

The battery is a two-terminal device that provides DC supply to

the inverter section when the AC mains are not available. This DC is

then converted into 220V AC supply and output at the inverter output

37

socket. It is pertinent to state that lead-acid batteries used in automobiles

are very good for this purpose as they provide good quality power for a

long duration and can be recharged once the power stored in them are

consumed. The backup time provided by the inverter depends on the

battery type and its current capacity

Primary (single-use or "disposable") batteries are used once and

discarded; the electrode materials are irreversibly changed during

discharge. Common examples are the alkaline battery used

for flashlights and a multitude of portable devices.

Secondary (rechargeable batteries) can be discharged and recharged

multiple times; the original composition of the electrodes can be restored

by reverse current. Examples include the lead-acid batteries used in

vehicles and lithium ion batteries used for portable electronics.

The battery was selected based on the amount of time we wanted

to operate the system at full load. As mentioned in the specifications, we

wanted to be able to power the lights. Fulfilling the 12 V DC battery

requirements, we found a unit from Universal Battery with 18 Ah. If the

battery is discharged to 50% at most, this battery leaves us with 9 Ah.

Our load of lighting, music, and an iPod charger uses about 20

watts, but with an alternative appliance connected (e.g. phone), the total

power consumed could be estimated at 25 watts. With a 12 VDC battery

and a 25 W load, we have about 2 A of current, which gives us about 4.5

hours of use at full load – this is consistent with our design

specifications. The exact battery we selected is UB12180 (12V 10Ah).

An electric battery is a device consisting of one or more electrochemical

cells that convert stored chemical energy into electrical energy. Each cell

contains a positive terminal, or cathode, and a negative terminal,

38

or anode. Electrolytes allow ions to move between the electrodes and

terminals, which allows current to flow out of the battery to perform

work.

A lead-acid battery charger is most popular though it will very

large size than others battery type. But them have advantage are : cheap,

easy to buy and long life if correctly uses.

3.7.1 BATTERY CHARGER

A battery charger is a device used to put energy into a cell or

(rechargeable) battery by forcing an electric current through it. Lead-

acid battery chargers typically have two tasks to accomplish. The first is

to restore capacity, often as quickly as practical. The second is to

maintain capacity by compensating for self discharge.

In both instances optimum operation requires accurate sensing of

battery voltage. When a typical lead-acid cell is charged, lead sulphate is

converted to lead on the battery’s negative plate and lead dioxide on the

positive plate. Over-charge reactions begin when the majority of lead

sulphate has been converted, typically resulting in the generation of

hydrogen and oxygen gas. At moderate charge rates, most of the

hydrogen and oxygen will recombine in sealed batteries. In unsealed

batteries however, dehydration will occur. The onset of over-charge can

be detected by monitoring battery voltage.

Over charge reactions are indicated by the sharp rise in cell

voltage. The point at which over-charge reactions begin is dependent on

charge rate, and as charge rate is increased, the percentage of returned

capacity at the onset of over-charge diminishes. For overcharge to

coincide with 100% return of capacity, the charge rate must typically be

less than 1/100 amps of its amp- hour capacity. At high charge rates,

39

controlled over-charging is typically as quickly as possible. To maintain

capacity on a fully charged battery, a constant voltage is applied. The

voltage must be high enough to compensate for self discharge, yet not

too high as to cause excessive over-charging.

3.7.2 CHARGING AND DISCHARGING OF BATTERY

Charging a lead acid battery is a matter of replenishing the

depleted supply of energy that the battery had lost during use. This

replenishing process can be accomplished with several different charger

implementations: “constant voltage charger”, “constant current charger”

or a “multistage" constant voltage/current charger. Each of these

approaches has its advantages and disadvantages that need to be

compared and weighed to see which one would be the most practical and

realistic to fit with our requirements.

Constant voltage charging is one of the most common charging

methods for lead acid batteries. The idea behind this approach is to keep

a constant voltage across the terminals of the battery at all times.

Initially, a large current will be drawn from the voltage source, but as the

battery charges and increases its internal voltage, the current will slowly

fold and decays exponentially.

When the battery is brought up to a potential full charge, which is

usually considered around 13.8V, the charging voltage is dropped down

to a lower value that will provide a trickle charge to maintain the battery

as long as it is plugged into the charger.

The best characteristic of this method is that it provides a way to

return a large bulk of the charge into the battery very fast. The drawback

is that to complete a full charge would take a much longer time since the

current is exponentially decreased as the battery charges. A prolonged

40

charging time must be considered as one of the issues to this design.

Constant current charging is another simple yet effective method for

charging lead acid batteries.

A current source is used to drive a uniform current through the

battery in a direction opposite of discharge. This can be analogous to

pouring water into a bucket with a constant water flow, no matter how

full the bucket is. Constant current sources are not very hard to

implement; therefore, the final solution would require a very simple

design.

There is a major drawback to this approach. Since the battery is

always being pushed at a constant rate, when it is close to being fully

charged, the charger would force extra current into the battery, causing

overcharge. The ability to harness this current is the key to a successful

charger. By monitoring the voltage on the battery, the charge level can

be determined, and at a certain point, the current source would need to

be folded back to only maintain a trickle charge and prevent

overcharging.

When the battery is connected to the external load, the chemical

changes take place in reverse direction, during which the absorbed

energy is released as electrical energy and supplied to the load. Thus the

12V DC output of the battery is fed to the MOSFET inverter.

3.8 INVERTER

The inverter should be chosen so that its input voltage matches

that of the storage battery. Fortunately, most inverters are designed to

operate at about 12V in order to function with standard lead-acid

batteries.

41

Inverter is a small circuit which will convert the direct current

(DC) to alternating current (AC). The power of a battery is converted in

to ‘main voltages’ or AC power. This power can be used for electronic

appliances like television, mobile phones, computer etc. the main

function of the inverter is to convert DC to AC and step-up transformer

is used to create main voltages from resulting AC.

Fig 3.12 Block diagram of inverter

In the block diagram battery supply is given to the MOSFET

driver where it will convert DC to AC and the resulting AC is given to

the step up transformer from the step up transformer we will the get the

original voltage.

3.8.1 MOSFET POWER INVERTER

This is the power inverter circuit based MOSFET RFP50N06. It is

a simple circuit inverter that converts DC current into AC current, from

12V DC to 220V AC with output power of 100W. Inverter circuit is

typically used for emergency lighting, since the power output is small,

which is about 5W only. The following diagram is an inverter circuit

which will give you 220V AC 50Hz with maximum power of 100W.

The inverter capable to handle loads up to 100 W, it’s depended on your

power inverter transformer.

Fig 3.13

This circuit will provide a very stable Output AC Voltage.

Frequency of operation is determined by a pot and is normally set to 50

Hz. The RFP50N06 FETs are rated at 10 Amps and 12

is required for coo

parallel connection to get more power. It is recommended to have a

“Fuse” in the Power Line and to always have a “Load connected”, while

power is being applied

be approximately 10 Amps per 100 watts of output. The Power leads

must be heavy enough wire

When utilizing N

across a load, the drain terminals of the high side MOSFETs are often

connected to the highest voltage in the system. This creates a difficulty,

as the gate terminal must be approximately 10V higher than the drain

terminal for the MOSFET to conduct. Often, integrated circuit devices

known as MOSFET drivers are utilized to achieve this difference

through charge pumps or bootstrapping techniques. These chips are

42

Schematic diagram of MOSFET inverter



FETs are rated at 10 Amps and 12 Volts. Heat sink

is required for cooling the MOSFETs. Add some MOSFETs with



power is being applied. The Fuse should be rated at 32 volts and should

oximately 10 Amps per 100 watts of output. The Power leads

must be heavy enough wire to handle this high current draw.

When utilizing N Channel MOSFETs to switch a DC voltage




minal for the MOSFET to conduct. Often, integrated circuit devices



Schematic diagram of MOSFET inverter



Volts. Heat sink

d some MOSFETs with



The Fuse should be rated at 32 volts and should

oximately 10 Amps per 100 watts of output. The Power leads

Channel MOSFETs to switch a DC voltage




minal for the MOSFET to conduct. Often, integrated circuit devices



43

capable of quickly charging the input capacitance of the MOSFET

quickly before the potential difference is reached, causing the gate to

source voltage to be the highest system voltage plus the capacitor

voltage, allowing it to conduct.

There are many MOSFET drivers available to power N Channel

MOSFETs through level translation of low voltage control signals into

voltages capable of supplying sufficient gate voltage. Advanced drivers

contain circuitry for powering high and low side devices as well as N

and P Channel MOSFETs. In this design, all MOSFETs are N Channel

due to their increased current handling capabilities.

To overcome the difficulties of driving high side N Channel

MOSFETs, the driver devices use an external source to charge a

bootstrapping capacitor connected between Vcc and source terminals.

The bootstrap capacitor provides gate charge to the high side MOSFET.

As the switch begins to conduct, the capacitor maintains a potential

difference, rapidly causing the MOSFET to further conduct, until it is

fully on. The name bootstrap component refers to this process and how

the MOSFET acts as if it is “pulling itself up by its own boot strap”.

Main components are:

IC LT4013 is basically made up of two D-type flip flop modules

and set/reset asynchronous toggle inputs. As the name suggests, the IC is

primarily used as a bistable for toggling the output stage of a particular

circuit, and it is fundamentally incorporated in most electronic circuits.

IC 4001is the most commonly used Complementary Metal Oxide

Semiconductor (CMOS) chip. It comes in a 14 pin Dual Inline Package

(DIP). It has small notch on one side which is identified as pin 1.It

consists of 4 independent NOR gate in a single chip. Each gate has 2

44

inputs and 1 output. Working voltage range of IC is from 5V to 15V. It

can deliver approx.10mA at 12V but this can be reduced as power

supply voltage reduces.

IC LM4001 along with IC4013 and the transistor form a voltage

controlled oscillator of which the frequency is adjusted with the

25Kohmpot. The 13 volt Zener stabilize supply voltages and limit

signals, while the 36 volt Zener limit spikes from the transformer.

3.8.2 WORKING OF MOSFET POWER INVERTER

The AC input supplies a 220V AC, 50Hz from the public supply.

This is connected to the charger circuit where it is rectified to DC

voltage and through the relay switch to the output of the inverter to

bypass the inverter when there is public electric power supply while the

battery is charging.

This inverter uses a 0 – 12 V/1Amp triggering transformer and a

regulator to sense the AC mains supply. When the AC mains supply is

available, this supply is given to the primary winding of the triggering

transformer to give 12V AC supply at the secondary winding. It is then

rectified by bridge rectifier and input to filter capacitors which convert

the 18V supply to 12V DC supply. The 12V supply stays constant even

when there is a change in the AC mains supply and the inverter is

informed about the availability of the AC mains supply.

The Oscillator, a pulse width modulator PMW IC SG 3524 to

generate the 50Hz frequency required to generate AC supply by the

inverter.

45

The battery supply is connected to the IC SG 3524 through the

inverter ON/OFF switch. The flip-flop converts the incoming signal into

signals with changing polarity such that in a two-signal with changing

polarity, the first is positive while the second is negative and vice versa.

This process is repeated 50times per second to give an alternating signal

with 50Hz frequency at the output of SG3524. This alternating signal is

known as "MOS Drive Signal ".

The MOS drive signals are given to the base of MOS driver

transistor which results in the MOS drive signal getting separated into

two different channels. The transistors amplify the 50Hz MOS drive

signal at their base to a sufficient level and output them from the emitter.

The 50Hz signal from the emitter of each of the transistor is connected

to the gate G of all the MOSFETS in each of the MOSFET channel,

through the appropriate resistance.

The battery charger hen the inverter section receives AC mains

supply, it stops operation but the charger section in the inverter starts its

operation. In this mode, the inverter transformer works as a step down

transformer and output 12V at its secondary winding.

During the charging, MOSFET transistors at the output section

works as rectifier with the drain working as the cathode while the source

works as the anode. The center-tapping of the transformer receives

positive supply and the MOSFET source 'S' receives negative supply

from the battery. The center-tapping is connected to the positive terminal

of the battery and the MOSFET source S is connected to the negative

terminal with a shunt resistance. Thus, when the inverter receives AC

mains supply, inverter transformer and MOSFET together work as a

charger and charge the battery.

46

The change over section is used to switch ON the inverter when

the AC mains supply is OFF and to switch OFF the inverter when the

AC mains supply returns (ON).

During changeover, when the inverter receives AC mains supply,

it stops drawing the battery supply and the AC mains supply at the

inverter input is directly sent to the inverter output socket. This is done

using a one, two-pole relay.

The AC output gives a 220V AC, 50Hz either directly from the

input when the AC mains supply is available or from the inverter circuit

action on the battery when the AC mains supply is not available.

Computers and other household appliances are connected to this output.

The AC input to this device was fused with a 5A fuse to protect

the transformer as well as the rectifying circuit in case of over voltage,

and high current which could flow into the transformer.

This AC is given to the step up transformer of the secondary coil

from this coil only we will get the increased AC voltage , this AC

voltage is so high; from step up transformer we will get the max voltage.

Zener diode will help avoid the reverse current.

The generated AC is not equal to the normal AC mains or house

hold current. You cannot use this voltage for pure electric appliances

like heater, electric cooker etc. Because of the fast switching of

MOSFETs heat is dissipated which will effect the efficiency, use heat

sink to remove this problem.

The output voltage of the inverter was a square wave, filtered by a

2µF/400V capacitor connected across the output terminals to remove the

unwanted harmonics and leaving smooth sine waveform output voltage.

47

Thus a 12 V AC output voltage is transferred to the primary of

transformer; it is stepped up to 230V.

3.9 STEP-UP TRANSFORMER

The output of the inverter is 12V ac supply with a frequency of

50 Hz . This Ac supply is step up to 230 V by using step-up transformer.

The Voltage Transformer can be thought of as an electrical component

rather than an electronic component.

Fig 3.14 Step-Up Transformer

A transformer basically is very simple static (or stationary)

electro-magnetic passive electrical device that works on the principle of

Faraday’s law of induction by converting electrical energy from one

value to another. On a step-up transformer there are more turns on the

secondary coil than the primary coil.

The transformer does this by linking together two or more

electrical circuits using a common oscillating magnetic circuit which is

produced by the transformer itself. A transformer operates on the

principals of “electromagnetic induction”, in the form of Mutual

Induction. Mutual induction is the process by which a coil of wire

magnetically induces a voltage into another coil located in close

proximity to it. Then we can say that transformers work in the “magnetic

48

domain”, and transformers get their name from the fact that they

“transform” one voltage or current level into another.

Transformers are capable of either increasing or decreasing the

voltage and current levels of their supply, without modifying its

frequency, or the amount of electrical power being transferred from one

winding to another via the magnetic circuit.

A single phase voltage transformer basically consists of two

electrical coils of wire, one called the “Primary Winding” and another

called the “Secondary Winding”. We will define the “primary” side of

the transformer as the side that usually takes power and the “secondary”

as the side that usually delivers power. In a single-phase voltage

transformer the primary is usually the side with the higher voltage.

These two coils are not in electrical contact with each other but

are instead wrapped together around a common closed magnetic iron

circuit called the “core”. This soft iron core is not solid but made up of

individual laminations connected together to help reduce the core’s

losses.

The two coil windings are electrically isolated from each other but

are magnetically linked through the common core allowing electrical

power to be transferred from one coil to the other. When an electric

current passed through the primary winding, a magnetic field is

developed which induces a voltage into the secondary winding .The

output of the transformer is 230 V, 50 Hz ,single phase AC, which is

fed to the load.

3.10 ADDITIONAL SOURCE FOR THE BATTERY

When the exercise machine is not in use, the main supply is used

to charge the battery.

bridge rectifier is used

Fig 3.15: Single phase f

The power supply consists of a Step down transformer (230V,

50Hz/12V) which steps down the voltage to 12V AC. This is converted

to DC using a Bridge rectifier. The ripples are removed using a

capacitive filter and it is then regulated to +12 V us

setup.

3.10.1 DIODE RECTIFIER FOR POWER SUPPLY

The purpose of a power supply is to take electrical energy in one

form and convert it into another. There are many types of power supply.

Most are designed to convert high voltage AC mains elect

suitable low voltage supply for electronic circuits and other devices such

as computers, fax machines and

Singapore, supply from 230V, 50Hz AC mains is converted into smooth

DC using AC-DC power supply. A power s

into a series of blocks, each of which performs a particular function.

A transformer first steps down high voltage AC to low voltage

AC. A rectifier circuit is then used to convert AC to DC. This DC,

49

TIONAL SOURCE FOR THE BATTERY


to charge the battery. For that step down transformer and single phase

bridge rectifier is used.

Single phase full-wave rectifier with filter




capacitive filter and it is then regulated to +12 V using a resistor diode

DIODE RECTIFIER FOR POWER SUPPLY



Most are designed to convert high voltage AC mains elect


as computers, fax machines and telecommunication equipment. In


DC power supply. A power supply can by broken down





For that step down transformer and single phase

wave rectifier with filter capacitor




ing a resistor diode



Most are designed to convert high voltage AC mains electricity to a


telecommunication equipment. In


upply can by broken down




50

however, contains ripples, which can be smoothened by a filter circuit.

Power supplies can be ‘regulated’ or ‘unregulated’.

A regulated power supply maintains a constant DC output voltage

through ‘feedback action’. The output voltage of an unregulated supply,

on the other hand, will not remain constant. It will vary depending on

varying operating conditions, for example when the magnitude of input

AC voltage changes.

Main components of a regulated supply to convert 230V AC

voltage to 12V DC are shown below.

Fig 3.16 Block diagram of regulated power supply

Power supplies are designed to produce as little ripple voltage as

possible, as the ripple can cause several problems. For Example

In audio amplifiers, too much ripple shows up as an

annoying 50 Hz or 100 Hz audible hum.

In video circuits, excessive ripple shows up as “hum” bars

in the picture.

In digital circuits it can cause erroneous outputs from logic

circuits.

51

3.10.2 SINGLE PHASE FULL-WAVE RECTIFIER

In many power supply circuits, the bridge rectifier is used. The

bridge rectifier produces almost double the output voltage as a full wave

center-tapped transformer rectifier using the same secondary voltage.

The advantage of using this circuit is that no center-tapped transformer

is required.

During the positive half cycle (Fig 3.17), both D3 and D1 are

forward biased. At the same time, both D2 and D4 are reverse biased.

Note the direction of current flow through the load. During the negative

half cycle (Fig 3.18) D2 and D4 are forward biased and D1 and D3

are reverse biased. Again note that current through the load is in the

same direction although the secondary winding polarity has reversed.

Fig 3.17 Operation during positive half cycle

Fig 3.18 Operation during negative half cycle

52

The load and ground connections are removed because we are

concerned with the diode conditions only. In this circuit, diodes D1 and

D3 are forward biased and act like closed switches. They can be

replaced with wires. Diodes D2 and D4 are reverse biased and act like

open switches. We can see that both diodes are reverse biased, in

parallel, and directly across the secondary winding. The peak inverse

voltage is therefore equal to Vm.

The voltage obtained across the load resistor of the full-wave

bridge rectifier described above has a large amount of ripple. A

capacitor filter may be added to smoothen the ripple in the output, as

shown below.

Fig 3.19 Full wave Bridge rectifier with capacitor filter

The rectifier circuits discussed above can be used to charge

batteries and to convert AC voltages into constant DC voltages. Full-

wave and bridge rectifier are more commonly used than half-wave

rectifier.

53

CHAPTER-4

IMPLEMENTATION AND RESULT

4.1 KEY REQUIREMENTS

The safety test is the most crucial aspect of the test plan and each

stage of the design must pass the safety test before moving on. The

safety is important to three elements of the design. The project is

designed for people who use this on a daily basis and safety evaluations

need to ensure nothing will compromise the user’s safety. After all,

something healthy such as exercising should not turn into something

unhealthy. The second element of the safety test is for the servicing of

the design. This means that the project should not discharge or bring

harm to the person working on the design. This project is being

developed to save the user energy and money..

The efficiency of each component needs to be as high as possible.

The method of determining efficiency was different for each subsystem.

For the generator, it requires high conversion efficiency from

mechanical energy into electrical energy. The microprocessor needs to

have the least amount of processing time as possible and this means

streamlining the code as much as possible but maintaining the basic

functional requirements. A high efficiency is required for each

component to get the maximum result from the entire design which will

translate into more energy and more money saved.

The implementation capabilities apply mainly to the aesthetics

and marketability of the design. The design needs to be compact enough

to be used at home next to the elliptical but also durable enough to be

used regularly at popular fitness centers.

54

55

4.2.1 DIAGRAM EXPLANATION

The circuit consist of a bicycle powered 120VA alternator

and then when the bicycle is pedaled, the spinning motion of the rear tire

is used to produce mechanical energy directly into a alternator. DC

supply is given to the alternator using a battery, thus the rotor produce

flux. While exercising, the alternator starts to rotate and produce three

phase AC supply. The output is connected to the rectifier.

The three phase AC supply is convert into DC through a three

phase diode bridge rectifier. Diode used is IN4007.The rectified DC

supply is given to the voltage regulator. Voltage regulator regulates the

voltage to 12V. Zener diode is used as voltage regulator.

This 12V is used to charge battery and the same DC supply is fed

to an inverter. The inverter is made is made with MOSFET and driver

circuit. The output of the inverter is 12V AC supply with a frequency of

50 Hz. This AC supply is step up to 230 V by using step up transformer.

Secondary of the transformer is directly connected to the load.

When the exercise machine is not used, the main supply is used to

charge the battery. For that charging step down transformer and bridge

rectifier is used.

The output of the transformer is 12V AC. This 12 V AC is

converted to DC by using diode bridge rectifier. Filter circuit also

provided for eliminating ripples.

The output from the diode rectifier is directly connected to the

battery. So the battery also charges while the exercise machine is not in

use. In our project, we are using a 40 W incandescent lamp as load.

56

4.3 ELEMENT SPECIFICATIONS

Our design will provide all of the following:

Bicycle: A stationary bicycle with belt and pulley

arrangement

Alternator: 120VA, 12V, 10A, 300 rpm alternator

Rectifier: Three phase bridge rectifier. Diode used IN4007

Battery: 10Ah 12VDC deep cycle lead acid battery for

compatibility, convenience, and cost.

Single phase 230V AC supply, step down transformer and

rectifier provide additional source for the battery.

Step down transformer : 230V to 12V AC single phase

transformer

Rectifier: Single phase full wave rectifier. Diode use

In4007

Inverter: 100W MOSFET inverter with 12V AC output.

Step-up transformer: 12V to 230V AC single phase

transformer

Load : 40W 230V incandescent bulb is connected as load.

4.4 PROJECT ANALYSIS

The time the light takes to turn on is dependent on both speed of

the bicycle and the voltage the regulator is adjusted. The initial

generated light has a blinking behavior, which stabilizes to an

unwavering beam as more power is generated and available to the

regulator and light.

57

Fig 4.2 Voltage Vs Speed

The fig 4.2 shows the relation between speed and the voltage The

voltage coming out of the alternator depends on two variables: the

amount of current flowing through the field coil (i.e. the strength of the

magnetic field) and the speed at which the alternator’s field is rotating.

The alternator has a regulator that tries to keep the voltage across the

battery at a steady 12.8V (the optimal voltage to recharge 12V batteries).

It does this by regulating the amount of current flowing to the field coil.

Once the alternator is self-sustaining, the only current flowing to

the field originates from the alternator itself. If the output voltage is too

high, the regulator lowers the current flowing to the field coil. If the

output voltage is too low, the regulator increases the current flowing to

the field coil. Simply put, as long as the alternator can maintain at least

12.8 V across the battery, making the pulley spin faster or slower will

have absolutely no effect on the power output. The output voltage of the

alternator with the RPM proves to be completely unchanging as

expected, due to the regulation of the alternator’s controller. The zener

diode was connected to the alternator which regulated the output voltage

to 12.8 V, shown in Fig 4.2

0

2

4

6

8

10

12

14

50 100 150 200 250 300

Volta

ge(V

)Speed (rpm)

VOLTAGE Vs SPEED

58

Fig 4.3 Current Vs Speed

The current of the alternator with the speed of the cycle (similar to

alternator speed) is shown in the Fig 4.3 .The output current is minimum

until around 300 rpm. Once that rpm rate is surpassed, the output current

increase according to the load connected

4.5 RESULT

We construct innovative exercise equipment for generating

electricity. By using bicycle, alternator, inverter, battery, step up and

step down transformer, rectifier circuit and incandescent lamp. We

successfully take the 230 V single phase 50 Hz output supply and it is

used to light 40W incandescent lamp. When the exercise machine is not

used, the main supply is used to charge the battery. So the battery also

charges while the exercise machine is not in use. So provide a

continuous supply.

0

2

4

6

8

10

12

50 100 150 200 250 300Cu

rren

t(A)

Speed (rpm)

CURRENT Vs SPEED

59

CHAPTER 5

CONCLUSION

We design and implement an innovative exercise equipment

(stationary bicycle) to generate electrical power for the house

appliances. Energy storage is deemed necessary and important within

renewable energy systems to ensure stability of the system. Coupling

pedal driven generation and storage will drastically increase reliability of

the smart system. These models vary in complexity and accuracy and

therefore the model chosen must match the application for which it is

needed. It will be very helpful for the rural areas.

In this day where the world is challenged to be more responsible

in its sourcing of electrical power, the method of human power

generation could be a solution that also helps mitigate the issue of

obesity and overweight. If additional design and study of this concept

proves it effective in energy use reduction, localized energy delivery and

sustainability education, it could efficiently answer the three great

challenges; source of electrical power, reducing the emission of CO2 to

the atmosphere and the issue of obesity

60

REFERENCES

[1] ABS Alaskan. (2006). DC to AC Power Inverters. Retrieved December4, 2006, from http://www.absak.com/basic/inverters.html.

[2] Adeyanju, A. Y. (2003). Design and Construction of a 750Watts Inverter, Unpublished B.Tech Thesis, LAUTECH, Ogbomoso, Nigeria.

[3] Allan, C. (1997). The Principle of Computer Hardware 2nd Edition, Oxford Science Publication, New York.

[4] Cyders, T. and Kremer, G. G., 2008, “Engineering Around the World: Driving Local Economics in Africa with HumanPower,” ASME Paper no. IMECE2008-67696, Proceedings of the ASME 2008 International Mechanical Engineering Congress and Exposition (IMECE2008), Vol. 9: Engineering Education and Professional Development, pp. 181-187.

[5] Dean T, The Human-Powered Home: Choosing Muscles Over Motors. New Society Publishers, 2008

[6] Free Plans To Build your own Bicycle Generator Pedal Power Station,” MNS Power. [Online]. Available: http://www.pedalpowergenerator.com/. [Accessed: 7-Jun-2012].

[7] Ganiyu, S. (2004). Design and Construction of a 1KVA Power Inverter, Unpublished B.Tech Thesis, LAUTECH, Ogbomoso.

[8] Gerard, J., 2008 “The Green Gym,” Fitness Matters,American Council on Exercise, Vol. 14, pp. 12-14

[9] Hughes, E. (1998). Electrical Technology, Longman Scientific Technological Book Series, London, 6th Edition.

[10] Human Powered Vehicle Challenge (HPVC) – Engineering Competitions -ASME - ASME,” American Society of Mechanical Engineers (ASME). [Online]. Available:http://www.asme.org/events/competitions/human-powered-vehicle-challenge-(hpvc). [Accessed: 21-Jun-2012].

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[11] Hutchison, F. H., 2007 “Facts About Electricity,” Clean- Energy.us: News and Facts about Coal Gasification. http://www.clean-energy.us/facts/electricity.htm

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[14] Paul Denholm, Erik Ela, Brendan Kirby, and Michael Milligan," The Role of Energy Storage with Renewable Electricity Generation", Technical Report NREL / TP-6A2- 47187

[15] Paul ides J.H, J. W. Jansen, L. Encica, E. A. Lomonova, and M. Smit, “Power from the people: Human-powered small-scale generation system for a sustainable dance club,”IEEE Industry Applications Magazine, vol. 17, no. 5, pp. 20–26, 2011

[16] Ravi N and H. V. K. Shetty, “Some aspects on design and development of human operated generator for desalination plant,” Electric Machines and Power Systems, vol. 19, no. 4, pp. 439–58, Jul. 1991.

[17] Suleiman, D. (2000). Design and Construction of a 500Watts Inverter, Unpublished B.Tech Thesis, LAUTECH, Ogbomoso, Nigeria.

[18] Texas State Campus Recreation. Calories to Kilowatts: Department of Campus Recreation: Texas State University. Texas State University. [Online] [Cited: March 2, ]]2010.] http://www.campusrecreation.txstate.edu/c2k/Calories‐to‐Kilowatts.html.

[19] Theraja, A. K. and Theraja, B. L. (1997). A text book of Electrical Technology, 22nd Edition, S. Chan and Co. Ltd, Delhi.

Exercise equipment for electrical energy generation- A Report

Engineering

wave rectifier

design of overall project

energy challenge

electrical power

electrical energy generation

human power generation

phase diode rectifier

mechanical energy