“MODELING AND ANALYSIS OF DC-DC CONVERTER FOR RENEWABLE ENERGY SYSTEM” Final report file

“MODELING AND ANALYSIS OF DC-DC CONVERTER
FOR RENEWABLE ENERGY SYSTEM”
A Project Submitted in Partial Fulfillment of the Requirement for the Award of the Degree
of
BACHELOR OF TECHNOLOGY
IN
ELECTRICAL ENGINEERING
Submitted By
ABHISHEK KUMAR CHAURASIA (213502)
KAUSHAL MOURYA (213506)
DHIRENDRA KUMAR BIND (213512)
Under the Supervision of
Mr. J.P LAL
Assistant Professor
Department of Electrical Engineering
Uma Nath Singh Institute of Engineering & Technology
VEER BAHADUR SINGH SINGH PURVANCHAL UNIVERSITY
JAUNPUR, INDIA
[2013-2017]

CERTIFICATE
This is certified that project entitled “MODELING AND ANALYSIS OF DC-DC
CONVERTER FOR RENEWABLE ENERGY SYSTEM” submitted by
ABHISHEK KUMAR CHAURASIA (213502), KAUSHAL MOURYA (213506),
DHIRENDRA KUMAR BIND (213512) of B.Tech 4th year, Electrical
Engineering, faculty of Engineering & Technology, VBS Purvanchal University
Jaunpur for the award of the degree of Bachelor of Technology, is a bonfide record
of work carried out by them under Guidance of Mr. J.P. Lal.
The content of this project has not been submitted to any other university or institute
for the award of any degree or diploma.
-------------------------- ---------------------------- -------------------------------
Dr. Ashok Srivastava Mr. Satyam Upadhyay Mr. J.P. Lal
(H.O.D , E.E) ( Project Co-ordinator) (Project Guide)
Place: Jaunpur
Date :--------------
DEPARTMENT OF ELECTRICAL ENGINEERING
VEER BAHADUR SINGH PURVANCHAL
UNIVERSITY

SELF ATTESTATION
This is certifying that, we have personally worked on the dissertation
entitled, “MODELING AND ANALYSIS OF DC-DC CONVERTER
FOR RENEWABLE ENERGY SYSTEM” a case study and obtained
during genuine work was done and collected by me.
Any other data and information in this report, which has been collected
from outside agency, has been duly acknowledged.
----------------------------------------------------------
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i
ACKNOWLEDGEMENT
On the submission of my thesis entitled “Modeling and analysis of DC-DC converter for
renewable energy system” I would like to extend my gratitude and sincere thanks to my
co-ordinator Mr. Stayam Upadhayay, (Asst. professor) and Mr. J.P. Lal (guide) Dept.
of Electrical Engineering for her constant motivation and support during the course work..
We would also like to thank Mr. Ashok Srivastava (Head of the Department, Electrical
Engineering) for providing us with resources and facilities as and when needed.
I truly appreciate and value her esteemed guidance and encouragement in the beginning.
I also deeply appreciate my parents and friends for their consistent support throughout.
Without my family’s sacrifice and support, this work would not have been possible. I
would like to affirm my indebtedness to my parents and my younger sister for care, support,
and encouragement.
I would like to thank all others who have consistently encouraged and gave me moral
support, without whose help it would be difficult to finish this project guide.
Last but not the least. We would like to thank all the staff members of Department of
Electrical Engineering who have been very cooperative with us.

ii
ABSTRACT
In recent years, there has been lots of emphasis put on the development of renewable
energy. While considerable improvement on renewable energy has been made, there
are some inherent limitations for these renewable energies. For example, for solar
and wind power, there is an intermittent nature. For the fuel cell, the dynamics of
electro-chemical reaction is quite slow compared to the electric load. This will not
be acceptable for modern electric application, which requires constant voltage of
constant frequency. This work proposed and evaluated a new power circuit that can
deal with the problem of the intermittent nature and slow response of the renewable
energy.
The proposed circuit integrates different renewable energy sources as well as
Energy storage. By integrating renewable energy sources with statistical tendency to
compensate each other, the effect of the intermittent nature can be greatly reduced.
This integration will increase the reliability and utilization of the overall system .It
can provide the extra energy required by load or absorb the excessive energy
provided by the energy sources, greatly improving the dynamics of overall system.
By using fuel cell we generate power for the load where solar and wind energies are
used for the constant maintenance of power. In this we are using buck-boost
choppers to step up and step down power to desired value. Rectifier converts ac to
dc, inverter converts dc to ac for load. In our project we are maintaining constant
power at load by using renewable energy. A software simulation model is developed
in Matlab/Simulink.

iii
TABLE OF CONTENTS
Acknowledgement I
Abstract II
Table of contents III
List of tables V
List of figures VI
List of abbreviations VIII
List of symbols IX
CHAPTER-1 INTRODUCTION 1-10
1.1 Introduction 1
1.2 The importance of energy storage 4
1.3 Emerging technology 4
CHAPTER-4 LITERATURE REVIEW 11-12
2.1 Overview 11
CHAPTER-3 RENEWABLE ENERGY SOURCES 13-35
3.1 Wind Power 13
3.2 Parts of wind turbine 15
3.3. Generator 18
3.3.1. Types of generator 18
2.3.2 Permanent magnet synchronous generator 18
3.4. Solar cell 19
3.4.1 History 20
3.4.2 PV Cell 21
3.4.3 PV Module 22
3.4.4 PV array 22
3.4.5 Working of PV cell 23

iv
3.4.6 Applications 25
3.5 Fuel cell 25
3.5.1 Fuel cell technology 27
3.5.2 Working of fuel cell 27
3.5.3 Classification 28
3.5.4 Electrolysis Mechanism 30
3.6 Concept of HDGS 32
3.7 Field of applications 32
3.8 Storage Technology 33
3.8.1 Pressurized storage tank 33
3.8.2 Advantage of Hydrogen fuel cell 34
3.8.3 Issues of Hydrogen fuel cell 34
CHAPTER-4 DC-DC CONVERT 36-39
4.1 Types of DC-DC converters 36
4.1.1 Buck converter 36
4.1.2 Boost converter 37
4.1.3 Buck-Boost converter 37
4.2 Modes of buck –boost converter 38
4.3 Field of application 39
CHAPTER-5 METHODS & MATERIALS 40-43
5.1 Research objective 40
5.2 Working 41
5.3 Brief description of block used 42
CHAPTER-6 SIMULATION & RESULT 45-50
6.1 Dc-dc converter without transformer (dc source only) 45
6.2 Dc-dc converter without transformer (using renewable energy sources) 47
6.2.1 Simulink diagram of solar cell 47
6.2.2 Simulink diagram of wind turbine 48

v
6.3 Dc-dc converter with transformer 49
6.3.1 Simulation diagram 50
6.4 Design parameters 51
CHAPTER -7 CONCLUSION AND FUTURE SCOPE 52
7.1C Conclusion 52
7.2 Future scope 52
REFERENCES 53-54
LIST OF TABLES
Table.No Name of Tables Page No.
3.1 Classification of fuel cell 30
6.1 Design Parameters 51

vi
LIST OF FIGURES
Figure.
No.
Name of the Figures Page No.
1.1 Annual investment in new renewable energy capacity 1
1.2 Renewable energy nameplate capacity 2
1.3 Price range of renewable electricity by technology 3
1.4 Global growth of renewables through to 2011 10
3.1 Wind power capacity in leading country 14
3.2 Part of wind turbine 15
3.3 Characteristics of wind turbine 17
3.4 Solar Panel 20
3.5 Structure of PV cell 22
3.6 Photovoltaic system 23
3.7 Working diagram of solar cell 24
3.8 Characteristics of photovoltaic cell 25
3.9 Fuel cell 28
3.10 Working of hydrogen fuel cell 29
3.11 Characteristics of fuel cell 33
4.1 Circuit diagram of buck converter 36
4.2 Circuit diagram of boost converter 37
4.3 Circuit diagram of buck-boost converter 38
5.1 Block diagram of typical renewable energy system 41
6.1 Circuit diagram of transformerless dc-dc converter 45
6.2 Input voltage waveform 45
6.3 Switching pulse for mosfets 46
6.4 Output voltage waveform 46
6.5 Output current waveform 46
6.6 Dc-dc converter without transformer 47

vii
6.7 Output current and voltage of solar cell 48
6.8 Stator current in ampere 49
6.9 Driving pulses 50
6.10 Output voltage & current with transformer 51

viii
LIST OF ABBREVIATIONS
PV Photo Voltaic
MPPT Maximum Power Point Tracking
DC Direct Current
MATLAB MATrix LABoratory
Fig Figure
PMSG Permanent Magnet Synchronous
Generator
MPP Maximum Power Point

ix
LIST OF SYMBOLS
G Solar irradiation in W/m2
Pw extracted power from the wind,
ρ air density
R blade radius (m), (it varies between 40-60 m)
Vw wind velocity (m/s)
Cp the power coefficient
λ speed ratio
β blade pitch angle (deg.)
F frequency
Φ flux
t number of turns

Chapter-1 INTRODUCTION
MODELING AND ANALYSIS OF DC-DC CONVERTER FOE RENEWABLE ENERGY SYSTEM 1
CHAPTER -I
1.1 INTRODUCTION
Due to the environmental problem, e.g., climate change, and political and economical reasons,
e.g., less dependence on the foreign energy import, high oil price, renewable energy has attracted
enormous attention. Investment worldwide in renewable energy has gone from below $10 billion
in 1995 to over $70 billion in 2007, shown in Fig. 1. Since 2000, renewable electricity installations
in the U.S., excluding hydro power, have nearly doubled, and in 2007 [1] ,there is 33 GW of
installed capacity. Wind power and solar power are the fastest growing renewable energy sectors.
Fig. 1.1. Annual investment in new renewable energy capacity

2007, wind capacity installations grew 45% and solar PV grew 40% from the previous year . Fig.
2 shows the increase of renewable energy from 2000 to 2007.
Fig. 1.2. Renewable electricity nameplate capacity (MW) and percent cumulative increase from
previous year.
As great advance in renewable energy has been made, the price for electricity produced with
renewable energy drops. The national average electricity price is about 10 cents per kWh. From
Fig. 3, the price for certain kinds of renewable energy is lower than 10 cents per kWh. As the cost
of conventional energy resources is increasing year, the trend in the cost of renewable technologies
is encouraging, making renewable energy an economical means of power generation in the near
future. Renewable energy technologies not only can solve the climate change and reduce the

dependence on foreign energy import, it is also suitable for distributed power generation. In remote
areas, where there are no transmission lines or the cost of building new transmission lines is high,
renewable energy can provide power without expensive and complicated grid infrastructure.
Fig. 1.3. Price range of renewable electricity by technology
Distributed power generation system has several advantages.
• It can reduce or avoid the necessity to build new transmission/distribution lines or upgrade
existing ones.
• It can be configured to meet peak power needs.
• It can diversify the energy sources and increase the reliability of the grid network.
• It can be configured to provide premium power, when coupled with uninterruptible power
supply (UPS).
• It can be located close to the user and can be installed in small increments to match the
load requirement of the customer.

1.2 The Importance of Energy Storage
In spite of the advances made in renewable energy, there are some inherent problems. One is the
intermittent nature. The output power from renewable energy sources is not constant. Another
problem is slow response compared with electric load. Electric loads may change their power
demand in very short time. However, it takes much longer time to change the output power from
renewable energy sources. A unique feature of renewable energy application is that renewable
energy sources are operated in their optimal operating points. Since the cost of implementing
renewable energy sources is high, it is desirable to get as much power as possible from the
renewable energy sources. Maximum power points is tracked during the operation. Therefore, the
power output from these sources tends to be constant, no matter how much the load power is. This
concept is like hybrid vehicles. The engine, which provides power to a electric motor, is operated
at its optimal operating point, no matter how much power the electric motor requires. The
difference between the power coming from the engine and the power required by the motor is
compensated by energy storage.
1.3 Emerging technologies
Other renewable energy technologies are still under development, and include cellulosic
ethanol, hot-dry-rock geothermal power, and marine energy. These technologies are not yet
widely demonstrated or have limited commercialization. Many are on the horizon and may have
potential comparable to other renewable energy technologies, but still depend on attracting
sufficient attention and research, development and demonstration (RD&D) funding.
There are numerous organizations within the academic, federal, and commercial sectors
conducting large scale advanced research in the field of renewable energy. This research spans
several areas of focus across the renewable energy spectrum. Most of the research is targeted at
improving efficiency and increasing overall energy yields. Multiple federally supported research
organizations have focused on renewable energy in recent years. Two of the most prominent of
these labs are Sandia National Laboratories and the National Renewable Energy
Laboratory (NREL), both of which are funded by the United States Department of Energy and

supported by various corporate partners. Sandia has a total budget of $2.4 billion while NREL has
a budget of $375 million.
• Enhanced geothermal system
Enhanced geothermal systems (EGS) are a new type of geothermal power technologies that
do not require natural convective hydrothermal resources. The vast majority of geothermal
energy within drilling reach is in dry and non-porous rock. EGS technologies "enhance"
and/or create geothermal resources in this "hot dry rock (HDR)" through hydraulic
stimulation. EGS and HDR technologies, like hydrothermal geothermal, are expected to be
baseload resources which produce power 24 hours a day like a fossil plant. Distinct from
hydrothermal, HDR and EGS may be feasible anywhere in the world, depending on the
economic limits of drill depth. Good locations are over deep granite covered by a thick
(3–5 km) layer of insulating sediments which slow heat loss. There are HDR and EGS
systems currently being developed and tested in France, Australia, Japan, Germany, the
U.S. and Switzerland. The largest EGS project in the world is a 25 megawatt demonstration
plant currently being developed in the Cooper Basin, Australia. The Cooper Basin has the
potential to generate 5,000–10,000 MW.
• Cellulosic ethanol
Several refineries that can process biomass and turn it into ethanol are built by companies
such as Iogen, POET, and Abengoa, while other companies such as the Verenium
Corporation, Novozymes, and Dyadic International are producing enzymes which could
enable future commercialization. The shift from food crop feedstocks to waste residues and
native grasses offers significant opportunities for a range of players, from farmers to
biotechnology firms, and from project developers to investors.
• Marine energy
Marine energy (also sometimes referred to as ocean energy) refers to the energy carried
by ocean waves, tides, salinity, and ocean temperature differences. The movement of water
in the world's oceans creates a vast store of kinetic energy, or energy in motion. This energy
can be harnessed to generate electricity to power homes, transport and industries. The term

marine energy encompasses both wave power – power from surface waves, and tidal
power obtained from the kinetic energy of large bodies of moving water. Reverse electro-
dialysis (RED) is a technology for generating electricity by mixing fresh river water and
salty sea water in large power cells designed for this purpose; as of 2016 it is being tested
at a small scale (50 kW). Offshore wind power is not a form of marine energy, as wind
power is derived from the wind, even if the wind turbines are placed over water.
The oceans have a tremendous amount of energy and are close to many if not most
concentrated populations. Ocean energy has the potential of providing a substantial amount
of new renewable energy around the world.
• Experimental solar power
Concentrated photovoltaics (CPV) systems employ sunlight concentrated onto
photovoltaic surfaces for the purpose of electricity generation. Thermoelectric, or
"thermovoltaic" devices convert a temperature difference between dissimilar materials into
an electric current.
• Floating solar arrays
Floating solar arrays are PV systems that float on the surface of drinking water reservoirs,
quarry lakes, irrigation canals or remediation and tailing ponds. A small number of such
systems exist in France, India, Japan, South Korea, the United Kingdom, Singapore and
the United States. The systems are said to have advantages over photovoltaics on land. The
cost of land is more expensive, and there are fewer rules and regulations for structures built
on bodies of water not used for recreation. Unlike most land-based solar plants, floating
arrays can be unobtrusive because they are hidden from public view. They achieve higher
efficiencies than PV panels on land, because water cools the panels. The panels have a
special coating to prevent rust or corrosion. In May 2008, the Far Niente Winery in
Oakville, California, pioneered the world's first floatovoltaic system by installing 994 solar
PV modules with a total capacity of 477 kW onto 130 pontoons and floating them on the
winery's irrigation pond. Utility-scale floating PV farms are starting to be
built. Kyocera will develop the world's largest, a 13.4 MW farm on the reservoir above
Yamakura Dam in Chiba Prefectureusing 50,000 solar panels. Salt-water resistant floating

farms are also being constructed for ocean use. The largest so far announced floatovoltaic
project is a 350 MW power station in the Amazon region of Brazil.
• Solar-assisted heat pump
A heat pump is a device that provides heat energy from a source of heat to a destination
called a "heat sink". Heat pumps are designed to move thermal energy opposite to the
direction of spontaneous heat flow by absorbing heat from a cold space and releasing it to
a warmer one. A solar-assisted heat pump represents the integration of a heat
pump and thermal solar panels in a single integrated system. Typically these two
technologies are used separately (or only placing them in parallel) to produce hot water.
In this system the solar thermal panel performs the function of the low temperature heat
source and the heat produced is used to feed the heat pump's evaporator. The goal of this
system is to get high COP and then produce energy in a more efficient and less expensive
It is possible to use any type of solar thermal panel (sheet and tubes, roll-bond, heat pipe,
thermal plates) or hybrid (mono/polycrystalline, thin film) in combination with the heat
pump. The use of a hybrid panel is preferable because it allows to cover a part of the
electricity demand of the heat pump and reduce the power consumption and consequently
the variable costs of the system.
• Artificial photosynthesis
Artificial photosynthesis uses techniques including nanotechnology to store solar
electromagnetic energy in chemical bonds by splitting water to produce hydrogen and then
using carbon dioxide to make methanol. Researchers in this field are striving to design
molecular mimics of photosynthesis that utilize a wider region of the solar spectrum,
employ catalytic systems made from abundant, inexpensive materials that are robust,
readily repaired, non-toxic, stable in a variety of environmental conditions and perform
more efficiently allowing a greater proportion of photon energy to end up in the storage
compounds, i.e., carbohydrates (rather than building and sustaining living cells).
However, prominent research faces hurdles, Sun Catalytix a MIT spin-off stopped scaling
up their prototype fuel-cell in 2012, because it offers few savings over other ways to make
hydrogen from sunlight.

• Algae fuels
Producing liquid fuels from oil-rich varieties of algae is an ongoing research topic. Various
microalgae grown in open or closed systems are being tried including some system that
can be set up in brownfield and desert lands.
• Solar aircraft
An electric aircraft is an aircraft that runs on electric motors rather than internal
combustion engines, with electricity coming from fuel cells, solar
cells, ultracapacitors, power beaming, or batteries.
Currently, flying manned electric aircraft are mostly experimental demonstrators, though
many small unmanned aerial vehicles are powered by batteries. Electrically powered
model aircraft have been flown since the 1970s, with one report in 1957. The first man-
carrying electrically powered flights were made in 1973.
• Solar updraft tower
The Solar updraft tower is a renewable-energy power plant for generating electricity from
low temperature solar heat. Sunshine heats the air beneath a very wide greenhouse-like
roofed collector structure surrounding the central base of a very tall chimney tower. The
resulting convection causes a hot air updraft in the tower by the chimney effect. This
airflow drives wind turbines placed in the chimney updraft or around the chimney base to
produce electricity. Plans for scaled-up versions of demonstration models will allow
significant power generation, and may allow development of other applications, such as
water extraction or distillation, and agriculture or horticulture. A more advanced version
of a similarly themed technology is the Vortex engine which aims to replace large physical
chimneys with a vortex of air created by a shorter, less-expensive structure.
• Space-based solar power
For either photovoltaic or thermal systems, one option is to loft them into space,
particularly Geo-synchronous orbit. To be competitive with Earth-based solar power
systems, the specific mass (kg/kW) times the cost to loft mass plus the cost of the parts
needs to be $2400 or less. I.e., for a parts cost plus rectenna of $1100/kW, the product of
the $/kg and kg/kW must be $1300/kW or less. Thus for 6.5 kg/kW, the transport cost

cannot exceed $200/kg. While that will require a 100 to one reduction, SpaceX is targeting
a ten to one reduction, Reaction Engines may make a 100 to one reduction possible.
1.4 GROWTH OF RENEWABLES
Fig.1.4 Global growth of renewables through to 2011
From the end of 2004, worldwide renewable energy capacity grew at rates of 10–60% annually for
many technologies. In 2015 global investment in renewables rose 5% to $285.9 billion, breaking
the previous record of $278.5 billion in 2011. 2015 was also the first year that saw renewables,
excluding large hydro, account for the majority of all new power capacity (134GW, making up
53.6% of the total). Of the renewables total, wind accounted for 72GW and solar photovoltaics

56GW; both record-breaking numbers and sharply up from 2014 figures (49GW and 45GW
respectively). In financial terms, solar made up 56% of total new investment and wind accounted
for 38%.
According to a 2011 projection by the International Energy Agency, solar power generators may
produce most of the world's electricity within 50 years, reducing the emissions of greenhouse gases
that harm the environment. Cedric Philibert, senior analyst in the renewable energy division at the
IEA said: "Photovoltaic and solar-thermal plants may meet most of the world's demand for
electricity by 2060 – and half of all energy needs – with wind, hydropower and biomass plants
supplying much of the remaining generation". "Photovoltaic and concentrated solar power together
can become the major source of electricity", Philibert said. n 2014 global wind power capacity
expanded 16% to 369,553 MW. Yearly wind energy production is also growing rapidly and has
reached around 4% of worldwide electricity usage, 11.4% in the EU, and it is widely used in Asia,
and the United States. In 2015, worldwide installed photovoltaics capacity increased to
227 gigawatts (GW), sufficient to supply 1 percent of global electricity demands. Solar thermal
energy stations operate in the USA and Spain, and as of 2016, the largest of these is the 392
MW Ivanpah Solar Electric Generating System in California

Chapter- 2 LITERATURE REVIEW
MODELING AND ANALYSIS OF DC-DC CONVERTER FOR RENEWABLE ENERGY SYSTEM 11
CHAPTER -II
LITERATURE REVIEW
2.1 Overview
Due to high demand of energy and limited availability of conventional energy, non-conventional
sources become more popular among researchers. A lot of research work is going on to enhance
the power efficiency of non-conventional sources and make it more reliable and beneficial.
Hybrid generation system uses more than one source, so that we can extract energy from different
sources at the same time which enhances the efficiency. From the working of PV /Wind hybrid
system is understood, different topologies that can be used for the hybridization of more than one
system and also about advantages and disadvantages of hybrid system. From and basic details of
PV cell, PV module, PV array and their modeling are studied. Also, the behavior of PV modules
at varying environmental conditions like solar irradiation and temperature are studied. Behavior
of PV module during partial shading condition and also how it’s bad effects can be minimized is
explained in. Different MPPT techniques, their advantages and disadvantages and why MPPT
control is required is explained in .The wind energy system, its working and also techniques to
extracts the maximum power from the wind energy system is understood from. From study about
different type of bi-directional converters, their working and how to use them in battery charging
and discharging is carried out.
The concept of multi-port DC-DC converter has been discussed in several papers. Sachin Jain and
Vivek Agarwal and A. Di Napoli, et al.connect different renewable energy sources in parallel
across a common DC bus. Another method to connect different sources is by using series
connection. In this work, the AC voltage produced by the wind turbine is rectified by a
uncontrolled rectifier. This DC voltage is connected in series with the DC voltage of PV
generators. The combined DC voltage is the input to the PWM voltage source inverter to provide
power to AC loads. Another method of integrating sources is by adding the flux in the multi-
winding transformer. In this circuit, there are two current-source input stage circuits, three-winding
coupled transformer and a common output stage. These components are connected around the
transformer. Magnetic flux addition is used to transfer power to the load. However, the above
topologies are uni-directional and suitable for low power application. For renewable energy

Chapter- 2 LITERATURE REVIEW
application, the circuit has to be bi-directional to integrate energy storage. Also the circuit has to
be for high power application. Another version uses two sets of half-bridge circuits where the
number of switches is reduced. Based on two-port topologies, a three port circuit, consisting of
three sets of full-bridge circuits was proposed by M. Michon, J. L. Duarte, et al. H. Tao, A.
Kotsopoulos et al. improved this circuit by duty ratio control to increase the soft-switching
operation range and designed the controller to regulate the load voltage and the input power from
renewable energy source.

Chapter-3 RENEWABLE ENERGY SOURCES
CHAPTER-III
RENEWABLE ENERGY SOURCES
The following subsections will describe several examples and show the importance of energy
storage in renewable energy applications.
3.1. Wind Power
Wind is the motion of air masses produced by the irregular heating of the earth’s surface by sun.
These differences consequently create forces that push air masses around for balancing the
global temperature or, on a much smaller scale, the temperature between land and sea or between
mountains. Wind energy is not a constant source of energy. It varies continuously and gives
energy in sudden bursts. About 50% of the entire energy is given out in just 15% of the operating
time. Wind strengths vary and thus cannot guarantee continuous power. It is best used in the
context of a system that has significant reserve capacity such as hydro, or reserve load, such as a
desalination plant, to mitigate the economic effects of resource variability. The power extracted
from the wind can be calculated by the given formula:
Pw=0.5ρπR3Vw3Cp(λ,β)
Where,
Pw = extracted power from the wind,
ρ= air density, (approximately 1.2 kg/m3 at 20¤ C at sea level)
R = blade radius (in m), (it varies between 40-60 m)
Vw = wind velocity (m/s) (velocity can be controlled between 3 to 30 m/s)
Cp = the power coefficient which is a function of both tip speed ratio (λ), and blade pitch angle,
(β)(deg.)
Power coefficient (Cp) is defined as the ratio of the output power produced to the power
available in the wind.

Fig.3.1 Wind power capacity in leading country
A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical
energy. If the mechanical energy is then converted to electricity, the machine is called a wind
generator, wind turbine, wind power unit (WPU), wind energy converter (WEC), or aerogenerator.
Wind turbines can be separated into two types based by the axis in which the turbine rotates.
Turbines that rotate around a horizontal axis are more common. Vertical-axis turbines are less
frequently used.

3.2 PARTS OF WIND TURBINE
Fig.3.2 Parts of Wind Turbine
Anemometer: Measures the wind speed and transmits wind speed data to the controller.
Blades: Most turbines have either two or three blades. Wind blowing over the blades causes the
blades to "lift" and rotate.
Brake: A disc brake which can be applied mechanically, electrically, or hydraulically to stop the
rotor in emergencies.
Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour
(mph) and shuts off the machine at about 65 mph. Turbines cannot operate at wind speeds above
about 65 mph because their generators could overheat.
Gear box: Gears connect the low-speed shaft to the high-speed shaft and increase the rotational
speeds from about 30 to 60 rotations per minute (rpm) to about 1200 to 1500 rpm, the rotational
speed required by most generators to produce electricity. The gear box is a costly (and heavy) part
of the wind turbine and engineers are exploring "direct-drive" generators that operate at lower
rotational speeds and don't need gear boxes.
Generator: Usually an off-the-shelf induction generator that produces 60-cycle AC electricity.

High-speed shaft: Drives the generator. Low-speed shaft: The rotor turns the low-speed shaft at
about 30 to 60 rotations per minute.
Nacelle: The rotor attaches to the nacelle, which sits atop the tower and includes the gear box,
low- and high-speed shafts, generator, controller, and brake. A cover protects the components
inside the nacelle. Some nacelles are large enough for a technician to stand inside while working.
Pitch: Blades are turned, or pitched, out of the wind to keep the rotor from turning in winds that
are too high or too low to produce electricity.
Rotor: The blades and the hub together are called the rotor.
Tower: Towers are made from tubular steel (shown here) or steel lattice. Because wind speed
increases with height, taller towers enable turbines to capture more energy and generate more
electricity.
Wind direction: This is an "upwind" turbine, so-called because it operates facing into the wind.
Other turbines are designed to run "downwind", facing away from the wind.
Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine
properly with respect to the wind.
Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into
the wind as the wind direction changes. Downwind turbines don't require a yaw drive, the wind
blows the rotor downwind.
Yaw motor: Powers the yaw drive
Fig. 3.3 shows the characteristics of wind turbines for different wind speeds (v). The X-axis is the
rotor speed of the wind turbine, while the Y-axis is the power extracted by the wind turbine. It can
be seen that for a given wind speed, there is one operating point, where the power output is
maximum. For example, if the wind speed is v1, the rotor speed of the wind turbine is controlled
to be so that the power from the wind turbine is maximum. This is the optimal operating point at
which the wind turbine is controlled to operate. This is called maximum power tracking.

Fig. 3.3 Characteristics of wind turbines
There are two dynamics encountered in the wind power application. Firstly, if the wind speed is
constant, the load power is changed, for example, from 1000 W to 500 W.
Since the wind turbine is producing 1000 W, if there is no energy storage, the rotor speed had to
be reduced such that the output power from the wind turbine is 500W. However, it may take longer
time for the wind turbine to adjust its rotor speed because of mechanical dynamics. Also if the
rotor speed is changed, the operating point of the wind turbine would not be optimal, wasting the
capability of the wind turbine. However, if there is energy storage installed in this system, the wind
turbine can still produce 1000 W while the load power is 500 W. This extra 500 W will go to the
energy storage. Therefore, with energy storage, the wind turbine can be operated at its optimal
operating point even if the load requires different power. Another dynamics is that the wind speed
changes while the load power is constant. For example, when the wind speed changes from v1 to
v2, the power from the wind turbine increases. If there is energy storage, this extra power will go
into the energy storage while the same power is supplied to the load. Therefore, with the energy
storage, the load can be supplied constant power even if the wind speed is not constant.

3.3 GENERATOR
The shaft of the wind turbine is mechanically coupled to the rotor shaft of the generator, so that
the mechanical power developed by the wind turbine (by kinetic energy to mechanical energy
conversion) is transmitted to the rotor shaft. This rotor structure has a rotor winding (either field
or armature). In both the cases, we get a moving conductor
in a stationary magnetic field or a stationary conductor in moving magnetic field. In either case,
electric voltage is generated by the generator principle.
3.3.1 TYPES OF GENERATORS
Generators can be basically classified on the type of current. There are alternating current
generators and direct current generators. But in either case, the voltage generated is alternating.
By adding a commutator, we convert it to direct current. So for convenience, we go for alternating
current generator.
In the AC generators, we can further classify them based on the rotor speed. There are synchronous
generators (constant speed machine) and asynchronous generators (variable speed machine or the
induction machine).
Another classification is based on the magnetic field. The magnetism can be done by either
permanent magnet or an electro-magnet. In order to reduce the supply requirement, we go for the
permanent magnet synchronous generator (PMSG) for the power generation using wind energy.
An induction motor running with negative slip can operate as an induction generator. But this
generator is not self-exciting and this has to be excited by a source of fixed frequency. It already
needs an exciter for stator. So this machine has to be fed by two supplies and hence it is called
doubly fed induction machine or generator.
So doubly fed induction generator (DFIG) and permanent magnet synchronous generator (PMSG)
are suitable for wind power generation. We are using PMSG in our work.
3.3.2 PERMANENT MAGNET SYNCHRONOUS
GENERATOR
A synchronous machine generates power in large amounts and has its field on the rotor and the
armature on the stator. The rotor may be of salient pole type or cylindrical type.

In the permanent magnet synchronous generator, the magnetic field is obtained by using a
permanent magnet, but not an electromagnet. The field flux remains constant in this case and the
supply required to excite the field winding is not necessary and slip rings are not required. All the
other things remain the same as normal synchronous generator.
The EMF generated by a synchronous generator is given as follows :
Where,
F is the frequency
Φ is the flux
t is the number of turns
3.4 SOLAR CELL
A solar cell (photovoltaic cell or photoelectric cell) is a solid state electrical device that converts
the energy of light directly into electricity by the photovoltaic effect. The energy of light is
transmitted by photons-small packets or quantums of light. Electrical energy is stored in
electromagnetic fields, which in turn can make a current of electrons flow.
Assemblies of solar cells are used to make solar modules which are used to capture energy from
sunlight. When multiple modules are assembled together (such as prior to installation on a pole-
mounted tracker system), the resulting integrated group of modules all oriented in one plane is
referred as a solar panel. The electrical energy generated from solar modules, is an example of
solar energy. Photovoltaics is the field of technology and research related to the practical
application of photovoltaic cells in producing electricity from light, though it is often used
specifically to refer to the generation of electricity from sunlight. Cells are described as
photovoltaic cells when the light source is not necessarily sunlight. These are used for detecting
light or other electromagnetic radiation near the visible range, for example infrared detectors, or
measurement of light intensity.

Fig.3.4 Solar panel
3.4.1 HISTORY
The development of solar cell technology began with the 1839 research of French physicist
Antoine-César Becquerel. Becquerel observed the photovoltaic effect while experimenting with a
solid electrode in an electrolyte solution when he saw a voltage develop when light fell upon the
electrode. The major events are discussed briefly below, and other milestones can be accessed by
clicking on the image shown below.
• Charles Fritts - First Solar Cell: The first genuine solar cell was built around 1883 by Charles
Fritts, who used junctions formed by coating selenium (a semiconductor) with an extremely thin
layer of gold. The device was only about 1 percent efficient.

• Albert Einstein - Photoelectric Effect: Albert Einstein explained the photoelectric effect in 1905
for which he received the Nobel Prize in Physics in 1921.
• Russell Ohl - Silicon Solar Cell: Early solar cells, however, had energy conversion efficiencies of
under one percent. In 1941, the silicon solar cell was invented by Russell Ohl.
• Gerald Pearson, Calvin Fuller and Daryl Chapin - Efficient Solar Cells: In 1954, three American
researchers, Gerald Pearson, Calvin Fuller and Daryl Chapin, designed a silicon solar cell capable
of a six percent energy conversion efficiency with direct sunlight. They created the first solar
panels. Bell Laboratories in New York announced the prototype manufacture of a new solar
battery. Bell had funded the research. The first public service trial of the Bell Solar Battery began
with a telephone carrier system (Americus, Georgia) on October 4 1955.
3.4.2 PV CELL
Photovoltaic cell is the building block of the PV system and semiconductor material such as silicon
and germanium are the building block of PV cell. Silicon is used for photovoltaic cell due to its
advantages over germanium. When photons hit the surface of solar cell, the electrons and holes
are generated by breaking the covalent bond inside the atom of semiconductor material and in
response electric field is generated by creating positive and negative terminals.
When these terminals are connected by a conductor an electric current will start flowing. This
electricity is used to power a load.
Fig.3.5 Structure of PV cell

3.4.3 PV MODULE
A single cell generate very low voltage (around 0.4), so more than one PV cells can be connected
either in serial or in parallel or as a grid (both serial and parallel) to form a PV module as shown
in fig.3.6. When we need higher voltage, we connect PV cell in series and if load demand is high
current then we connect PV cell in parallel. Usually there are 36 or 76 cells in general PV modules.
Module we are using having 54 cells. The front side of the module is transparent usually buildup
of low-iron and transparent glass material, and the PV cell is encapsulated. The efficiency of a
module is not as good as PV cell, because the glass cover and frame reflects some amount of the
incoming radiation.
3.4.4 PV ARRAY
A photovoltaic array is simply an interconnection of several PV modules in serial and/or parallel.
The power generated by individual modules may not be sufficient to meet the requirement of
trading applications, so the modules are secured in a grid form or as an array to gratify the load
demand. In an array, the modules are connected like as that of cells connected in a module. While
making a PV array, generally the modules are initially connected in serial manner to obtain the
desired voltage, and then strings so obtained are connected in parallel in order to produce more
current based on the requirement.
Fig.3.6 Photovoltaic system

3.4.5 HOW IT WORKS
Solar cells, which largely are made from crystalline silicon work on the principle of
Photoelectric Effect that this semiconductor exhibits. Silicon in its purest form- Intrinsic Silicon-
is doped with a dopant impurity to yield Extrinsic Silicon of desired characteristic (p-type or n-
type Silicon). Working of Solar cells can thus be based on crystalline structure of Intrinsic and
Extrinsic Silicon. When p and n type silicon combine they result in formation of potential
barrier. These and more are discussed below.
Fig. 3.7 Working diagram of solar cell
When light, in the form of photons, hits solar cell, its energy breaks apart electron-hole pairs
(Photoelectric effect). Each photon with enough energy will normally free exactly one electron,
resulting in a free hole as well. If this happens close enough to the electric field, or if free electron
and free hole happen to wander into its range of influence, the field will send the electron to the N
side and the hole to the P side. This causes further disruption of electrical neutrality, and if an
external current path is provided, electrons will flow through the path to the P side to unite with
holes that the electric field sent there, doing work for us along the way. The electron flow provides
the current, and the cell's electric field causes a voltage.

Silicon is very shiny material, which can send photons bouncing away before energizing the
electrons, so an antireflective coating is applied to reduce those losses. The final step is to install
something that will protect the cell from the external elements- often a glass cover plate. PV
modules are generally made by connecting several individual cells together to achieve useful levels
of voltage and current, and putting them in a sturdy frame complete with positive and negative
terminals.
Fig.3.8 shows the characteristics for solar photovoltaics . The X-axis is the terminal voltage of the
photovoltaic cell while the Y-axis is the power output of the cell. It can be seen that for a given
solar irradiance, there is one point, where the output power is maximum. The power electronics is
controlled such that the terminal voltage of the solar photovoltaic is the voltage where the optimal
operating point is. Just like wind turbine, the dynamics of the load and the photovoltaics require
the usage of energy storage if we want to operate the solar photovoltaic in its optimal operating
points. Then energy storage will provide the deficit power and absorb the excessive power of the
system.
Fig.3.8 Characteristics of photovoltaic

3.4.6 APPLICATION
Solar cells are often electrically connected and encapsulated as a module. Photovoltaic modules
often have a sheet of glass on the front (sun up) side allowing light to pass while protecting the
semiconductor wafers from abrasion and impact due to wind-driven debris, rain, hail, etc. Solar
cells are also usually connected in series in modules, creating an additive voltage. Connecting cells
in parallel will yield a higher current; however, very significant problems exist with parallel
connections. For example, shadow effects can shut down the weaker (less illuminated) parallel
string (a number of series connected cells) causing substantial power loss and even damaging the
weaker string because of the excessive reverse bias applied to the shadowed cells by their
illuminated partners. Strings of series cells are usually handled independently and not connected
in parallel, special paralleling circuits are the exceptions. Although modules can be interconnected
to create an array with the desired peak DC voltage and loading current capacity, using
independent MPPTs (maximum power point trackers) provides a better solution. In the absence of
paralleling circuits, shunt diodes can be used to reduce the power loss due to shadowing in arrays
with series/parallel connected cells.
3.5. FUEL CELL
Basically, a fuel cell is a device that converts directly the chemical energy stored in gaseous
molecules of fuel and oxidant into electrical energy. When the fuel is hydrogen the only by‐
products are pure water and heat. The overall process is the reverse of water electrolysis. In
electrolysis, an electric current applied to water produces hydrogen and oxygen; by reversing the
process, hydrogen and oxygen are combined to produce electricity and water (and heat).
A fuel cell can be seen with profit as a “chemical factory” that continuously transforms fuel energy
into electricity as long as fuel is supplied. However, unlike internal combustion engines that can
be regarded as factories as well, fuel cells rely on a chemical reaction involving the fuel, and not
on its combustion.
During combustion, molecular hydrogen and oxygen bonds are broken and electrons reconfigure
into molecular water bonds at a picoseconds length scale. There is no possible way to “catch up”
these free electrons and the net energy difference between molecular bonds in products vs.
reactants can only be recovered in the most degraded form of energy, i.e. heat. A Carnot cycle

involving the transformation of heat into mechanical and electrical energy is then involved in
conventional methods for generating electricity: these successive steps of transformation of energy
severely limit the overall efficiency of the process (which is by definition the product of the
efficiency of the different steps).
In a fuel cell the direct conversion of the chemical energy of covalent bonds into electrical energy
is made possible by the spatial separation of the hydrogen and oxygen reactants by the electrolyte.
The electron transfer necessary to complete the bonding reconfiguration into water
molecules occurs over a much longer length scale. This allows direct collection of electrons as a
current in fuel cells and leads to fuel efficiencies two to three times higher than in internal
combustion engines (depending on the fuel cell technology).
Unlike batteries, there is no chemical transformation of any component of the fuel cell device
during operation and it can generate power without recharging, as long as it is being fed with fuel.
The unit fuel cell structure called the membrane electrode assembly (MEA) typically consists of
an electrolyte in contact on its both sides with two electrodes, one negative electrode (anode) and
one positive electrode (cathode). Fuel is continuously fed to the anode side and oxidant is
continuously fed to the cathode side.
Fuel cell reactants are classified as fuels and oxidants on the basis on their electron donor and
electron acceptor properties. Oxidants mainly include pure oxygen and oxygen‐ containing gases
e.g. air, or halogens e.g. chlorine. Fuels include pure hydrogen and hydrogen‐containing gases,
e.g. methanol, ethanol, natural gas, gasoline, biogas, diesel, etc.
In the most straightforward case, i.e. the hydrogen fuel cell the combustion of hydrogen into water
is split into two electrochemical reactions occurring at the anode and cathode, respectively, which
are termed as the two half‐cell reactions:
H2 = 2 H+
+ 2 e‐
½ O2 + 2 H+
+ 2 e‐
= H2O
Combination of the two half‐cell reactions gives the overall combustion reaction:
H2 + ½ O2 → H2O

Fig.3.9 Fuel Cell
3.5.1 FUEL CELL TECHNOLOGY
A fuel cell is a galvanic cell that efficiently converts chemical energy to electrical energy and
useful heat. Stationary fuel cells can be used for backup power as well as distributed power.
Modularity of fuel cells makes them useful for almost any portable application that typically uses
batteries. Fuel cells have proved to be very effective in the transportation sector from personal
vehicles to marine vessels.
3.5.2 Working of Fuel Cell
Figure 3.10 shows the basic working principle of a hydrogen fuel cell. It consists of two electrodes
separated by an electrolyte. When hydrogen gas, in channels, flows to the anode, a catalyst (usually
platinum based) causes the hydrogen molecule to split into protons and electrons. These electrons
follow an external circuit to the cathode, whereas the protons get conducted through the electrolyte.
This flow of electrons through the external circuit is the produced electricity that can be used to
do work.

Fig.3.10 Working of hydrogen fuel cell
3.5.3 Classification of Hydrogen Fuel Cells
In this section, we will be discussing the classification criterion of hydrogen fuel cells
followed by a detailed description of each hydrogen fuel cell. Table 1 provides us with the
classification of the types of hydrogen fuel cells that are currently in use and development.
Fuel cells are usually classified depending on the electrolyte that is used in them, with one
exception: the direct methanol fuel cell in which methanol is directly fed to the anode in
the course of the reaction. Methanol acts as a fuel in these types of fuel cells eliminating
the need to reform the fuel to hydrogen. Fuel cells can also be classified on the basis of
operating temperature for the fuel cell. Alkaline fuel cells, Polymer electrolyte membrane
fuel cell, direct methanol fuel cell and Phosphoric acid fuel are low temperature fuel cells:
the operating temperature is below 220 o
C. Molten carbonate fuel cells and Solid oxide fuel
cells are high temperature fuel cells, with an operating temperature of around 600-1000 o
C.
Table 1: Classification of fuel cells

Fuel Cell Type Operating System Output Efficiency Application
Temperature
(o
C)
53-58% Backup Power,
Polymer 50-100 1kW – 250Kw
(transportation) Portable Power,
Transportation,
Electrolyte 25-35% (stationary)
Small
Distributed,
Generation
Direct Methanol 60-90 1W – 100W 25-35% Small Portable
Power
Alkaline 90-100 10kW – 60% Military, Space
100kW
Phosphoric Acid 150-200 50kW – 1MW >40% Distributed
Generation
Large
Distributed
Molten Carbonate 600-700 1kW – 1MW 45-47%
Generation,
Electric
Utility.
Auxiliary
Power,
Solid Oxide 600-1000 1kW – 3MW 35-43%
Large
Distributed
Generation,
Electric
Utility

Water is electrolysed in an electrochemical cell to produce hydrogen and oxygen. Water
electrolysis was one of the main means of hydrogen production before the steam reforming
process was introduced.
Water can be electrolysed by passing direct current (DC) through it in the presence of a suitable
electrolyte, causing positively charged hydrogen ions to migrate to the negatively charged cathode,
where they reduce to form hydrogen. Similarly, oxygen is formed at the positively charged anode.
Chemically inert conductors such as platinum are used as electrodes to avoid unwanted reactions
and the production of impurities in the hydrogen gas.
Anode: 2 H2O O2 + 4 H+
+ 4 e-
Cathode: 4 H+
+ 4 e-
2 H2
Overall reaction: 2 H2O 2 H2 + O2
Three different process versions have been developed for electrolytic water dissociation:
• Alkaline water electrolysers are in use commercially for long times. Alkaline electrolysers
work at atmospheric or low pressure (0-8 bar) or at pressure (up to 30 bar).
• Proton Exchange Membrane (PEM) electrolysers (reverse reaction of PEM-fuel cell) use
an organic membrane instead of alkaline aqueous solution, which leads to a significant
volume
• Reduction PEM electrolysers exhibit higher efficiency while
• Operating at significantly higher current densities when compared to the advanced alkaline
electrolysers (but system costs are still very high, see below). Mitsubishi Corporation is
developing a ‘High-pressure Hydrogen Energy Generator’ (HHEG), which is based on a
proton exchange membrane stack in a high pressure vessel, which stores high-compressed
hydrogen generated by electrolysis. The advantage of the system is that it produces high-
pressure hydrogen by itself without the
need for further compression.
High-temperature steam electrolysis operates between 700 and 1000o
C, using oxygen ion-
conducting stabilised ZrO2-ceramics as an electrolyte (reverse reaction of Solid Oxide Fuel Cell).
The water to be dissociated is entered on the cathode side as steam, which forms a steam hydrogen
3.5.4 ELECTROLYSIS MECHANISMS

mixture during electrolytic dissociation (Winter and Nitsch 1988). The dissociation of steam
theoretically requires less electrical energy than the dissociation of water. The energy required for
water evaporation can be supplied by thermal energy and thus allows the use of various energy
sources. The driving force for the development of the high-temperature electrolysis process in the
1980s was to use waste heat from high temperature nuclear reactors for hydrogen production, but
most research activities were reduced significantly since then. Because of the improvements in
Solid Oxide Fuel Cell technologies, there is a new interest in this technology, which can be
combined with high temperature solar heat. Solid Oxide Fuel Cells (SOFC) used in electrolysis
mode, called Solid Oxide Electrolyser Cells (SOEC), have the potential to become an efficient
electrolyser technology.
Fig.3.11 shows the characteristics for fuel cells. It can be seen that there is a point where the
efficiency is maximum. This is the operating point at which we want to operate the fuel cell. At
this operating point, the output power from the fuel cell is fixed. If the load power is changed, the
energy storage will compensate the power difference without changing the output power of the
fuel cell
Fig. 3.11 Characteristics of fuel cell

3.6 Concept of Hybrid Distributed Generation System
Hybrid distributed generation system (HDGS) has gained attention in recent years. This system
integrates different kinds of renewable energy sources to increase the overall stability and
utilization .A secure supply based on only one renewable energy source requires a substantial
energy storage. The reason is that the renewable energy is not available during some period of
time. For example, the photovoltaic cells produce zero power during the night or little power
during the cloudy day.
Wind energy may not be available if the wind speed is under certain speed, under which the wind
turbine cannot extract energy from the wind. If the system has to provide the power to load during
the time when renewable energy source produces little power, the only way is to use the power
from the energy storage. If two or even more different renewable energy sources are integrated,
the storage capacity requirement would be greatly reduced, since the fluctuations of these
two renewable energy sources may have a statistical tendency to compensate each other.
For example, solar power is high during the day, while the wind power is high at night. Combining
these two sources will approximately produce a constant power to the load during the entire day.
Another example of HDGS is the integration of photovoltaics and fuel cell. Since the output power
of photovoltaics depends on the solar irradiance. Solar irrandiance varies during the day. In order
to have a constant power output, the output power of fuel cell is adjusted according to the output
power of photovoltaics. In this way, the total power from the photovoltaics and the fuel cell will
be the same even though the solar irradiannce is not constant. Therefore, a combination of
photovoltaic and fuel cell forms a good pair for HDGS application.
3.7 Fields of application
Electrolysis is scaleable from few Nm3
/h to several 10,000 Nm3
/h, so that it can be used for
decentralised on-site hydrogen production as well as for large scale centralised hydrogen plants.
On-site hydrogen production can use existing electrical infrastructure and has the advantage that
no additional infrastructure for hydrogen distribution is required. Due to their flexibility in
operation (start and stop on demand) electrolysers can support the load management in the
electricity grid and thus facilitate the integration of fluctuating energy sources.

Because of the additional high temperature heat requirements from a nuclear reactor or a solar
thermal facility, early process design studies for a high temperature steam electrolysis process
assumed a hydrogen production capacity of several 10,000 Nm3
/h (Dönitz 1988). A Solid Oxide
Electrolyser Cell will be scaleable over a broad capacity range, thus also allowing the decentralised
hydrogen production.
3.8 STORAGE TECHNOLOGY
In the development of fuel cell vehicles, hydrogen storage is “the biggest remaining research
problem” according to the January
2003 Office of Technology Policy report, Fuel Cell Vehicles: Race to a New Automotive
Future. Current hydrogen storage systems are inadequate to meet the needs of consumers in a
fuel cell vehicle Existing and proposed technologies for hydrogen storage include
Physical storage: pressurized tanks for gaseous hydrogen and pressurized cryo-tanks for liquid
hydrogen;
• Reversible hydrogen uptake in various metal-based compounds including hydrides,
nitrides, and imides;
• Chemical storage in irreversible hydrogen carriers such as methanol;
• Cryo-adsorption with activated carbon as the most common adsorbent; and
• Advanced carbon materials absorption, including carbon nanotubes, alkali-doped carbon
nanotubes, and graphite nanofibers.
3.8.1 Pressurized Tank Storage
Pressurized tanks of adequate strength, including impact resistance for safety in collisions, have
been made of carbon-fiber wrapped cylinders. Compressed gas storage in such tanks has been
demonstrated at a pressure of 34 MPa (5,000 psi) with a mass of 32.5 kg and volume of 186 L,
sufficient for a 500-km range. Note, however, that this tank volume is about 90% of a 55-gallon
drum, rather large for individual automobiles. So while the 6 wt% goal can be achieved, tank
volume is problematic. Pressures of 70 MPa (10,000 psi) have been reached, and in 2002 Germany
certified Quantum Technology’s
10,000 psi on-board storage tank. A footnote in the OTP report cited above says, “The Toyota and
Honda vehicles available for lease in late 2002 use hydrogen stored in high-pressure containers.

However, their range will be less than optimal because hydrogen’s low density does not permit a
sufficient amount to be stored (unlike CNG [compressed natural gas], which has a higher energy
density for the same volume).”
Low temperature storage of liquid hydrogen does not appear to be suitable for normal vehicle
use, although research on this possibility is being conducted at a low level by several automobile
manufacturers.
Furthermore, “a liquid hydrogen storage system loses up to 1% a day by boiling and up to 30%
during filling, as well as requiring insulation to keep the hydrogen at 20 K.”
3.8.2 Advantages of Hydrogen Fuel Cell
• Efficiency
Fuel cells combine many of the advantages of both internal combustion engines (ICE) and
batteries. Thanks to the direct conversion of chemical energy into electrical energy, fuel cells are
2‐3 times as efficient as ICEs for vehicle propulsion: the net electrical efficiency of a PEMFC
ranges between 40 and above 50% in a driving schedule, which is favorably compared to the 21‐
24% efficiency range of ICEs “from well to wheel”, i.e. accounting for the type of fuel used and
its entire life cycle. Now if we add in the calculations the reforming process of gasoline and
methanol or the use of compressed hydrogen in the calculations the efficiencies are 33, 38, and
about 50%, respectively.
Interestingly, the fuel cell efficiency does not drop for small systems because it does not depend
on its size: unlike gas turbines for example that suffer from scale effects, small fuel cell devices
are quite as efficient as larger ones. Accounting for energy losses in ancillaries the efficiency is
somewhat lowered but is in any case higher than conventional systems.
3.8.3 Issues of Hydrogen Fuel Cell
There are three main barriers remaining to widespread adoption of the fuel cell technology:
• Cost
• Durability
• Lack of hydrogen infrastructure

The lack of hydrogen infrastructure has long been considered the biggest obstacle in particular for
introduction of fuel cell vehicles, although this question resembles the classic chicken‐and‐egg
problem (there are no FCVs because there are no hydrogen fuelling stations, but there are no
hydrogen fuelling stations because there is no demand for hydrogen as fuel for FCVs…).
Establishing the necessary infrastructure for hydrogen production, transport and distribution would
require significant capital investment, but there is no absolute impediment, since hundreds of
hydrogen refuelling stations already exist in the U.S.A., Japan, and Europe. Obviously, legislation
and standards are however still missing. In a recent paper published by General Motors, it is
projected that consumers will not have to pay significantly more for hydrogen than gasoline in the
longer term and also that the key challenge remains matching scale and timing of hydrogen
investment with actual hydrogen demand

Chapter-4 DC-DC CONVERTER
CHAPTER-IV
DC-DC CONVERTER
DC-DC converter is an electrical circuit whose main application is to transform a dc voltage
from one level to another level. It is similar to a transformer in AC source, it can able to step
the voltage level up or down. The variable dc voltage level can be regulated by controlling
the duty ratio (on-off time of a switch) of the converter.
There are various types of dc-dc converters that can be used to transform the level of the
voltage as per the supply availability and load requirement. Some of them are discussed
below.
4.1 TYPES OF DC-DC CONVERTER
1. Buck converter
2. Boost converter
3. Buck-Boost converter
4.1.1 Buck converter:
The functionality of a buck converter is to reduce the voltage level. The circuit diagram of
the buck converter is manifested in figure 4.1
Fig.4.1 circuit diagram of buck converter
When the switching element is in state of conduction the voltage appearing across the load is
Vin and the current is supplied from source to load. When the switch is off the load voltage
is zero and the direction of current remains the same. As the power flows from source side to
load side, the load side voltage remains less than the source side voltage. The output voltage

is determined as a function of source voltage using the duty ratio of the gate pulse given to
the switch. It is the product of the duty ratio and the input voltage
4.1.2 Boost converter:
The functionality of boost converter is to increase the voltage level. The circuit configuration
of the boost converter is manifested in figure 4.2.
Fig.4.2. Circuit diagram of boost converter
The current carried by the inductor starts rising and it stores energy during ON time
of the switching element. The circuit is said to be in charging state. During OFF
condition, the reserve energy of the inductor starts dissipating into the load along with
the supply. The output voltage level exceeds that of the input voltage and is dependent
on the inductor time constant. The load side voltage is the ratio of source side voltage
and the duty ratio of the switching device.
4.1.3 Buck-Boost converter:
The functionality of a buck-boost converter is to set the level of load side voltage to either
greater than or less than that of the source side voltage. The circuit configuration of the buck-
boost converter is manifested in figure 4.3.

Fig.4.3. Circuit diagram of buck-boost converter
When the switches are in the state of conduction, the current carried by the inductor starts
rising and it stores energy. The circuit is said to be in charging state. While the switches are
in the OFF state, this stored energy of the inductor is dissipated to the load through the diodes.
The output voltage can be varied based on the On-time of the switches. The buck-boost
converter acts as both buck and boost converters depending on the duty cycle of the switches.
For the duty ratio less than 50% it acts as a buck converter and for the duty ratio exceeds than
50% it acts as boost converter.
As the voltage can be stepped both up and down, we use buck-boost converter for our
convenience in our work.
4.2 Modes of Buck Boost Converters
There are two different types of modes in the buck boost converter. The following are the two
different types of buck boost converters.
Continuous conduction mode.
Discontinuous conduction mode.
Continuous Conduction Mode
In the continuous conduction mode the current from end to end of inductor never goes to zero.
Hence the inductor partially discharges earlier than the switching cycle.
Discontinuous Conduction Mode
In this mode the current through the inductor goes to zero. Hence the inductor will totally
discharge at the end of switching cycles.

4.3 Applications of Buck boost converter
It is used in the self-regulating power supplies.
It has consumer electronics.
It is used in the Battery power systems.
Adaptive control applications.
Power amplifier applications.

Chapter-5 MATERIAL AND METHODS
CHAPTER-V
METHOD AND MATERIALS
5.1 Research Objective:
In this work, a new kind of multi-port DC-DC power converter will be proposed in order to
integrate different renewable energy sources and energy storage effectively and economically. The
proposed circuit will be analyzed, modeled, designed, controlled, and simulated. Certain issues
related to practical application will be discussed to verify the usefulness of the propose circuit.
They will include the stability of the circuit under different operating points, how to start this
circuit without external assistance, how to manage the power flow between the source, the load
and the energy storage, how to control to circuit to regulate or control the load voltage while
keeping the input power from the renewable energy sources almost constant under the influence
of the dynamic load, how to maintain a fixed load voltage under the influence of the variation of
input voltage of renewable energy sources, and how to integrate current-source like renewable
energy sources.

5.2 WORKING:
A block diagram of a typical renewable energy system is shown below.
Fig 5.1 Block diagram of a typical renewable energy system
Figure5.1 shows the integration of several renewable sources like wind, solar, fuel cell etc to a
common low voltage dc bus. There is a battery connected to store energy during surplus of power
and delivers energy when needed.

The basic model to describe the dynamics of an Renewable energy system with Hydrogen storage
(RESHS) is shown in fig.5.1 It integrates sub-models of the electrolyser, the fuel cell, the batteries,
the power interfaces (buck and boost converters) and the storage system. Interdependency issues
(hydrogen consumption cannot exceed production) are taken into account. Special attention is
given to the characterization of the system’s major components in the transient state, and use
simple and realistic assumptions to describe the behaviour for short and long-term operation of the
RESHS. During periods of excess load demand over the input renewable resources, a
fuel cell operating on stored hydrogen would provide a balance of power To ensure a proper flow
of power between the system elements, the available energy from different sources are coupled to
a low voltage DC bus. A direct connection of DC bus to the electrolyser is not suitable because it
lacks the ability to control the power flow between renewable input source and the electrolyser
.Therefore, a power conditioning system, usually a DC-DC converter is required to couple the
electrolyser to the system bus. High-frequency (HF) transformer isolated, DC-DC converter is
suitable for this application due to their small size, light weight and reduced cost.
5.3 BRIEF DESCRIPTION OF BLOCK USED
PHOTO VOLTAICS:
“Photovoltaic” is a marriage of two words: “photo”, meaning light, and “voltaic”, meaning
electricity. Photovoltaic technology, the scientific term used to describe what we use to convert
solar energy into electricity, generates electricity from light. We use a semi-conductor material
which can be adapted to release electrons, the negatively charged particles that form the basis of
electricity.
WIND TURBINES
A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical
energy. If the mechanical energy is then converted to electricity, the machine is called a wind
generator, wind turbine, wind power unit (WPU), wind energy converter (WEC), or
aerogenerator.
RECTIFIERS:

Rectifiers are used to convert the AC which periodically flows in reverse direction to DC. Which
flows only in one direction is known as rectification. In this the rectifiers converts
the AC supply which is produced from the wind turbines in to DC.
REGULATORS:
Regulators are used to regulate the output voltage which is produced from the renewable energy
systems.
DC TO DC CONVERTERS:
DC-DC Converters are developed to maximize the energy harvest for pv system and wind turbines
are called power optimizers. The boost converter is used to step up the voltage when the input
voltage lower than the output voltage and the buck converter is used to step down the voltage
.These to are operated based on the requirement.
ELECTROLYSER:
Electrolysis process takes place in this electrolyser. By providing energy from a battery, water can
be dissociated in to diatomic molecules of hydrogen and oxygen. The hydrogen which is produced
from this electrolysis process is stored in the storage. The long-term excess energy with respect to
load demand has been sent to the electrolyser for hydrogen production and then the fuel cell has
utilized this stored hydrogen to produce electricity when wind and solar energies are insufficient.
The DC power required by the electrolyser system is supplied by the DC-DC converter.
Electrolysis of water is the best way to produce eco-friendly hydrogen because:
(i) Water on earth is abundant
(ii) Hydrogen is provided from abundant renewable energy Sources.
(iii) Oxidation of Hydrogen for the production of electrical energy (in fuel cells)
(iv) Produces only water when it is recycled.
(v) The stored hydrogen is fed to a fuel cell to produce electricity.
FUEL CELL:

Fuel cell is a device that converts the chemical enercy from a fuel into electricity through a
chemical reaction of positively charged hydrogen ions with oxygen or another oxidizing agent.
BATTERIES:
The electricity which is produced from these sources are stored in the battery. Here the battery is
for storing purpose.
INVETERS:
Inverters are used for many applications, as in situations where low voltage DC sources such as
batteries, solar panels or fuel cells must be converted so that devices can run off of AC power.
DC BUS:
To ensure a proper flow of power between the system elements, the available energy from different
sources are coupled to a low voltage DC bus. A direct connection of DC bus to the electrolyser is
not suitable because it lacks the ability to control the power flow between renewable input source
and the electrolyser. Therefore, a power conditioning system, usually a DC-DC converter is
required to couple the electrolyser to the system bus. High-frequency (HF) transformer isolated,
DC-DC converter is suitable for this application due to their small size, light weight and reduced
cost.

Chapter-6 RESULTS AND DISCUSSIONS
CHAPTER-VI
RESULTS AND DISCUSSIONS
6.1 DC-DC CONVERTER WITHOUT TRANSFORMER (dc source only)
Fig 6.1 Circuit diagram of Transformerless DC- DC converter
Simulation Result:
Fig 6.2 Input voltage waveform (X axis-Time(sec),Yaxis- Amplitude)

Fig 6.3 Switching pulse for mosfet’s (X axis-Time(sec),Yaxis-Amplitude)
Fig 6.4 Output voltage waveform (X axis-Time(sec),Yaxis- Amplitude)
Fig.6.5 Output current waveform (X axis-Time(sec),Yaxis-Current (Amp))

6.2 DC-DC CONVERTER WITHOUT TRANSFORMER(using renewable
energy sources)
Fig.6.6 DC-DC Converter without Transformer
6.2.1 Simulation diagram of solar cell:

Simulation Result of Solar cell:
Fig 6.7 . Output current & voltage of solar cell
6.2.2 Simulink diagram of wind turbine

Simulation Result of wind turbine:
Fig 6.8 Stator current in ampere
6.3 DC-DC CONVERTER WITH TRANSFORMER
SIMULATION DIAGRAM

Simulation result:
Fig 6.9 Driving Pulses(X axis-Time(sec),Y axis-Amplitude)
Fig. 6.10 Output voltage and Current(X axis-time , Yaxis- amplitude)

Table 6.1 Design Parameters
6.4 DESIGN PARAMETERS

Chapter-7 CONCLUSION AND FUTURE SCOPE
CHAPTER-VII
CONCLUSION AND FUTURE SCOPE
7.1 CONCLUSION
This project portrays a comparative analysis of DC-DC Converters for Renewable Energy System.
The electrolysis method which increases the hydrogen production and storage rate from wind-PV
systems.
It has been proved that DC-DC converter with transformer has the desirable features for
electrolyser application. The converter operates in lagging PF mode for a very wide change in load
and supply voltage variations, thus ensuring ZVS for all the primary switches. The peak current
through the switches decreases with load current.This paper portrays a comparative analysis of
DC-DC Converters for Renewable Energy System . The simulation and experimental results show
that the power gain obtained by this method clearly increases the hydrogen production and storage
rate from wind-PV systems. It has been proved that
DC-DC converter with transformer has the desirable features for electrolyser application.
Theoretical predictions of the selected configuration have been compared with the MATLAB
simulation results. The simulation and experimental results indicate that the output of the inverter
is nearly sinusoidal. The output of rectifier is pure DC due to the presence of LC filter at the output.
It can be seen that the efficiency of DC-DC converter with transformer is 15% higher than the
converter without transformer.
7.2 FUTURE SCOPE
• In the near future wind energy is going to be the most promising source of electrical energy
generation. Thus it is outmost importance to stabilize the wind energy conversion system
from fluctuating voltages and power following which wind energy could be utilized
maximum.
• Comparative performance analysis of transformer can be made using different control
strategy.
• Stability analysis will be made using modern control techniques.

REFERENCES
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REFERENCES
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