MODELING OF HYBRID RENEWABLE ENERGY GENERATION CONSISTING

OF WIND, FUEL CELL AND ULTRA CAPACITOR

MOHAMMAD FATHI

A project report submitted in partial fulfilment of the requirements for the award of the degree of Master of Engineering (Electrical - Power)

Faculty of Electrical Engineering Universiti Teknologi Malaysia

MAY 2011

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To God the Almighty, without whom knowledge without faith is fruitless and to my

lovely parents and my sisters and brother, who do not let me sense me alone.

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ACKNOWLEDGEMENT

First of all, I am greatly indebted to ALLAH SWT to make this project

successful. I would like to acknowledge my supervisor Professor Ir. Dr. Abdullah

Asuhaimi bin Mohd Zin who has given me support and guidance throughout the

period of this research. His patience and perseverance towards the outcome of this

study is of the highest standard. Without him this project could not become a reality.

Last but not least, I would like to thank other Faculty of Electrical Engineering

(FKE) staffs and my family for their motivation and moral supports.

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ABSTRACT

Consider to the finish of fossil fuel and the growth of population, the need of

creating and utilizing new sources of energy is increased. During the past few

decades, scientists have discovered new resources to generate electricity. These kinds

of energy are called renewable energies. Alongside all the benefits of new resources

they have some disadvantages that cannot use them widely. For example, one of the

issues in generating electricity from wind is the variation of wind speed. In the case

of having an ideal generation of electricity, the use of stable and power quality curve

is necessary. But this variation of wind speed sometimes makes a problem in

drawing this curve. In order to solve this problem, this study offered the utilizing of

the wind and fuel cells as renewable energy in a hybrid configuration. This

configuration can solve problems of renewable energy. In this project, the generating

of electricity is hydride from wind turbines and fuel cell. If the speed of wind is not

enough to generate the electricity, the fuel cell would start to generate it. However,

the fuel cell needs the time to arrive nominal value which ultra capacitor start to

generate the electricity in this gap. All the system consists of grid, wind turbine, fuel

cell and ultra capacitor was simulated in MATLAB software. The output of system

should be a stable carve. It means this hybrid system’s generation as a reliable

production is used in all wind speed condition. By using this, the disadvantage of

using wind is reduced and also the power quality of distribution’s grid and electricity

production be improved.

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ABSTRAK

Kekurangan bahan api sejak kebelakangan ini memberi motivasi untuk

mencari sumber tenaga yang baru. Beberapa dekad yang lalu, para ahli saintis telah

mempelajari bagaimana penggunaan sumber tenaga dalam penghasilan elektrik.

Tenaga yang dimaksudkan ialah tenaga yang boleh di perbaharui. Walaupun tenaga

yang boleh diperbaharui mempunyai banyak kebaikan tetapi keburukan yang ada

padanya telah menghalang penggunaan sumber tersebut secara berleluasa.

Contohnya, kepelbagaian kelajuan angin merupakan isu yang besar dalam tenaga

angin. Bagi menghasilkan penjanaan yang sempurna, penghasilan elektrik perlu

dilakukan dalam lengkungan yang tepat. Bagi menyelesaikan masalah tersebut,

penggunaan sumber tenaga secara hibrid telah diperkenalkan dalam projek ini. Dua

sumber tenaga boleh diperbaharui telah digunakan iaitu fuel cell and tenaga angin.

Dalam keadaan tenaga angin tidak mencukupi, tenaga akan dihasilkan daripada fuel

cell. Dengan kata lain, apabila pengeluaran angin berkurangan, tenaga akan mula

dihasilkan daripada fuel cell. Walaubagaimanapun, fuel cell memerlukan masa untuk

mencapai nilai yang nominal yang mana masalah ini dapat diatasi dengan

menggunakan kapasitor sebagai penyimpan tenaga. Sistem yang terdiri daripada

penjana angin, fuel cell dan kapasitor telah di analisis dalam perisian MATLAB.

Keluaran sistem tersebut perlu dalam lengkungan yang tepat. Ini bermakna, dalam

sistem hibrid ini, penjanaan tenaga boleh dalam semua keadaan angin. Oleh yang

demikian, sumber tenaga boleh diperbaharui dapat digunakan secara meluas. Akhir

sekali, jumlah kos penghasilan tenaga elektrik akan semakin berkurangan.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF FIGURES x

LIST OF ABBREVIATIONS

LIST OF SYMBOLS

LIST OF APPENDICES

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xiii

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1 INTRODUCTION 1

1.1 Background of the Study 1

1.2 Significance of Study 3

1.3 Problem statements 4

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1.4 Objective of Study 5

1.5 Scope of Study 5

1.6 Organization of the Report 5

2 LITERATURE REVIEW 7

2.1 Introduction 7

2.2 System description 10

2.2.1 Wind Energy Conversion System 11

2.2.1.1 Advantages 12

2.2.1.2 Disadvantages 13

2.2.1.3 Description of wind turbine characteristics

2.2.2 Fuel Cell (FC)

2.2.2.1 Technology Basics

2.2.2.2 Types of fuel cells

2.2.2.3 Advantages

2.2.2.4 Disadvantages

2.2.2.5 Model Assumptions

2.2.2.6 Model Limitations

2.2.2.7 Applications

2.2.2.8 Stationary power

2.2.2.9 Hydrogen Generation

2.2.3 Storage and Ultra Capacitor

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2.2.3.1 Ultra Capacitor

2.3 Design of the Hybrid System

2.4 Summary

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3 METHODOLOGY 32

3.1 Introduction 32

3.2 Data Collection

3.2.1 Load demand, PD

3.2.2 Generation limit, P max and P min

3.2.3 Wind speed

3.2.4 Wind generator capacity

3.2.5 Maximum allowed delay for generation

3.2.6 FC capacity of generation and H2 storage tank

3.3 System Elements

3.3.1 Wind turbine compound with generator (doubly-fed

induction generation or DFIG)

3.3.2 Fuel Cell (FC)

3.3.3 Ultra Capacitor (UC)

3.4 Assumptions

3.5 Limitations

3.6 Design hybrid system

3.7 The economical assessment of hybrid system by HOMER

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3.8 Summary 49

4 RESULTS 50

4.1 Introduction 50

4.2 Wind Energy Conversion System 51

4.3 Fuel Cell 53

4.4 Ultra capacitor

4.5 Design of the Hybrid System

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56

4.5.1 FC and wind generate (both start t=0s) 57

4.5.2 FC and wind generate with UC (all start t=0s) 58

4.5.3 FC (start t=0s) and wind generate with delay

4.5.4 FC and UC (start t=0) and wind generate with

delay

4.6 Summary

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5 CONCLUSIONS 61

5.1 Introduction 61

5.2 Conclusions 61

5.3 Suggestions for Future Works 62

REFERENCES 64

APPENDX A 66

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xii

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Wind-Fuel Cell hybrid energy system 9

2.2 Two different of wind turbine model 12

2.3 Wind speed, scaled data daily profile 14

2.4 The Wind Turbine and the Doubly-Fed Induction Generator System15

2.5 Fuel Cell 17

2.6 Basic fuel cell components 17

2.7 The exhaust of fuel cell after generating electricity is water 20

2.8 PEM fuel cell system block diagram 22 2.9 Classical equivalent model for the UC unit 29

3.1 Flow Chart for Project’s Methodology 33

3.2 The Block diagrams of wind turbine and drive train 37

3.3 The Simulink model of the wind turbine 38

3.4 The Simulink model of the drive train connect to wind turbine 38

3.5 Block diagram of doubly fed induction generator 39

3.6 Block diagram of Fuel Cell 42

3.7 Dynamic model of solid oxide Fuel cell (SOFC) 43

3.8 Block diagram of FC and its inverter before connect to grid 44

3.9 Simulink equivalent model for the UC unit 45

3.10 Block diagram of UC and its inverter before connect to grid 45

3.11 Schematic picture of Hybrid generation consist of

wind turbine, FC and UC 47

3.12 Connections of three elements of system 48

4.1 The result of wind turbine and generator if the wind

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at the time t=0 be 1pu 51

4.2 The voltage and current output of wind turbine in volt

and ampere unit 52

4.3 The RMS value of voltage and current output of wind

turbine in volt and ampere unit 52

4.4 The value of generation from FC 53

4.5 The voltage and current of FC in volt and ampere unit 54

4.6 Power generated by UC in t=0s 55

4.7 The voltage and current of FC in volt and ampere unit 55

4.8 The RMS value of voltage and current of UC in volt and ampere unit 56

4.9 Generating result of wind and FC when all start from t=0s 57

4.10 Generating result of wind, FC and UC when all start from t=0s 58

4.11 Generating result of wind and FC when FC start at t=0s and

wind start at t=0.4s 59

4.12 Generating result of wind, FC and UC when FC and UC

start at t=0s and wind start at t=0.4s 59

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LIST OF ABBREVIATIONS

FC - Fuel Cell

UC - Ultra Capacitor

NREL - National Renewable Energy Laboratory’s

WT - Wind Turbine

PEM - Proton exchange membrane or Polymer Exchange Membrane

DFIG - Doubly fed induction generation

IG - Induction Generator

MCFC - Molten Carbonate

SOFC - Solid Oxide Fuel Cell

AFC - Alkaline Fuel Cell

PAFC - Phosphoric acid Fuel Cell

DMFC - Direct Methanol Fuel Cell

ESR - Equivalent series resistance

EPR - Equivalent parallel resistance

PF - Power Factor

VSC - Voltage-sourced converters

IEEE - The Institute of Electrical and Electronics Engineers

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LIST OF SYMBOLS

푃 - Mechanical output power of turbine

퐶 - Performance coefficient of the wind turbine

휆 - Tip speed ratio of the rotor blade tip speed to wind

훽 - Blade pitch angle ( )

휌 - Air density (kg/푚 )

A - Turbine swept area (m )

푣 - Wind speed ( )

푛 - Hydrogen produced (moles/sec)

휂퐹 - Faraday efficiency=96.5푒(. . )

휂푐 - Number of electrolyzer cells in series

푖 - Electrolyzer current

F - Faraday constant (CK/mol)

T - Temperature of operation

z - Number of moving electrons

i0 - Exchange current

En - Nernst voltage

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α - Charge transfer coefficient C - Capacitance [F]

CUC-total - The total UC system capacitance [F]

EPR - Equivalent parallel resistance [Ω]

ESR, R - Equivalent series internal resistance [Ω]

EUC - The amount of energy released or captured by the UC bank [Ws]

ns - The number of capacitors connected in series

np - The number of series strings in parallel

R UC-total - The total UC system resistance [Ω]

푉 - The initial voltage before discharging starts [V]

푉 - The final voltage after discharging ends [V]

Tm - Shaft mechanical torque

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A Feasibility of hybrid renewable energy

types consist of Wind, Fuel Cell with

CHP, Diesel Generator and Battery under

Alaska condition

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CHAPTER 1

INTRODUCTION

1.1 Background of Study

With the developed of world, it seemed the energy was the main part for

improving economic and social development and also it drives a good living standard.

Due to increased access to electricity, it will improve opportunities for industrial

development and enhances health and education. Renewable Energy (RE) has a great

potential to contribute to development of national sustainable energy infrastructures in

many countries in the world. Hybrid Renewable Energy is a combination of more than

one type of energy in one system. For instance, Fuel cell and wind can become one

hybrid type of Renewable energy generation. A hybrid energy system based on such

alternative technologies has been proven to be a feasible solution for stand-alone

power generation at remote locations, where the cost of grid extension is prohibitive

and the price of fossil fuels increase drastically. Moreover, the hybrid systems such as

wind/diesel are now proven technologies and are an option to supply small electrical

loads at remote locations as reported by Zhang Hongyi et al. , Lundsager and Bindner

[1].

2

A wind system alone cannot satisfy the load requirement for 24 hours.

Stand-alone diesel generator sets are generally expensive to operate and maintain

especially at low load levels. In simple system, the diesel runs continuously to

cover the difference between the load demand and the wind energy, as a result

the diesel generator runs sometimes under light-load conditions. Due to low

efficiency of the generator at light load, the fuel saving potential is limited. Wind and

diesel have complementary characteristics namely, capital cost of diesel is lower

compared with wind turbine system, maintenance requirements of wind are less

compared to diesel, and diesel energy is available all the time where as the availability

of wind energy is dependent on the wind. Battery technology has reached a very

suppurate stage; size, cost and disposal are the constraining factors for its use in remote

stand-alone applications. Recent advancements in Fuel Cell (FC) and electrolyzer

technology have opened up the option for using hydrogen as an energy storage

medium [2] .

Some studies are reported about design, optimum combination and analysis

of hybrid renewable energy power generations with energy storage. The overall

goal is to identify the current availability of commercial hybrid renewable energy

systems and its components by using Homer software. Inputs to HOMER will

perform an hourly simulation of every possible combination of components

entered and rank the systems according to user-specified criteria, such as cost of

energy (COE, US$/kWh) or capital costs. Furthermore, HOMER can perform

“sensitivity analyses” in which the values of certain parameters (e.g., solar

radiation or wind speed) are varied to determine their impact on the system

configuration [3]

Standalone diesel generating system utilized in remote islands has long been

practiced in Alaska. Because of high fluctuation diesel price, such a system is seemed to

be uneconomical, particularly in the long run if the supply of electricity for rural areas

only depends on such diesel generating system. Here the potential use of hybrid

3

Wind/Fuel cell (FC)/Battery /diesel energy system was analyzed in remote areas.

National Renewable Energy Laboratory’s (NREL) HOMER software was used to

present the techno economic feasibility of hybrid Wind/Fuel cell (FC) /Battery/diesel

energy system. The investigation verified the impact of wind/ FC penetration and battery

storage on energy production, cost of energy and number of operational hours of diesel

generators for the given hybrid configuration. Emphasis has also been placed on

percentage fuel savings and reduction in carbon emissions of different hybrid systems.

At the end, suitability of utilizing hybrid Wind/Fuel cell (FC)/Battery /diesel energy

system over standalone diesel system would be discussed mainly based on different load

demand, wind speed, FC and diesel prices . In order to determine the economic and

technical feasibility of a wind/fuel cell/diesel system, computer modeling of the different

power system options have to be done [4].

1.2 Significance of Study

This project needs to be solved. Notice to this case that it should feed all demand

loads with different types of generation with enough power, reliable voltage and

frequency in our grid. Thus for having a reliable power system, it needs to assess our

system in two status. First of all before start to design each system it is necessary to have

an economical assessment. It is mean that, if it was assumed to make a power plant for

generating electricity. In this case it’s so important the low cost of production. In the

other word, the electricity generation in new power plant should not be more expensive

in compare to normal generation on that place. Second of all, the new planned system

should be able to work in normal and abnormal condition. It means this new system

capable to work in practical state. Thus this system has to assess from technical

viewpoints. Each parts has own characteristics for having a best work points.

4

The disadvantages of these renewable types are:

In wind turbine: the wind speed is variable and sometimes it stops to blow.

Fuel cell: cannot supply load in long duration and takes time to start to generate

power.

For having a good quality of electricity, should not have any interruption or

blackout for delivering electricity to consumers.

1.3 Problem statements

The problem statements of this project are:

a) The disadvantages of these renewable types.

In wind turbine: the wind speed is variable and sometimes it stops to blow

Fuel cell: cannot supply load in long duration and takes time to start to generate

power

b) For having a good quality of electricity, should not have any interruption or

blackout for delivering electricity to consumers

5

1.4 Objective of Study

The objectives of this study are:

1) To generate a system consisting of wind, FC and UC.

2) This system should generate power demand (active power) by the best output

(sustain generation and fast starting) and deliver this power to grid.

1.5 Scope of Study

The scope and limitation of the study are as follow:

1) Handling of the modeling of wind turbine (WT), Fuel Cell (FC) and Ultra

Capacitor (UC) to generate a good quality and quantity of power for deliver to

grid.

2) Integrated these three different types to get better results.

3) The simulation by using MATLAB 7.0 Simulink for technical part and using

HOMER software to do economical assessment.

1.6 Organization of the Report

This thesis is divided into five chapters. The first chapter is the significance of

the study, followed by chapter 2, which discuss about the literature review and previous

study. Chapter 3 describes about the methodology of the system. The results and

6

discussions will be discussed in Chapter 4. The last chapter provides the conclusion of

the study.

64

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1020

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PV-WEC hybrid system", Solar Energy, 2003

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