off grid pv system

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Bahir Dar University Institute of Technology School of Computing and Electrical Engineering Electrical and Computing Engineering(Power and Control Stream) Design Of Off-grid Pv System For Bata Veterinary Clinic Members: Berhan Teshale [268/01] Rediet Tsegaye[1067/01] Supervisor: Mr. Teketay .M February 2014

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  • Bahir Dar University

    Institute of Technology

    School of Computing and Electrical Engineering

    Electrical and Computing Engineering(Power and Control Stream)

    Design Of Off-grid Pv System For BataVeterinary Clinic

    Members:

    Berhan Teshale [268/01]

    Rediet Tsegaye[1067/01]

    Supervisor:

    Mr. Teketay .M

    February 2014

    http://www.university.comFaculty Web Site URL Here (include http://)School of Computing and Electrical Engineering (include http://)http://www.authorname.comhttp://www.authorname.comhttp://www.supeAbebervisorname.com

  • Declaration of Authorship

    We, Berhan Teshale and Rediet Tsegaye, declare that this thesis titled, Title Of Your

    Thesis and the work presented in it are our own. We confirm that:

    This work was done wholly or mainly while in candidature for a bachelor degree

    at this University.

    Where any part of this thesis has previously been submitted for a degree or any

    other qualification at this University or any other institution, this has been clearly

    stated. Where we have consulted the published work of others, this is always

    clearly attributed.

    Where we have quoted from the work of others, the source is always given. With

    the exception of such quotations, this thesis is entirely our own work. We have

    acknowledged all main sources of help.

    Authors:

    Berhan Teshale

    Rediet Tsrgsye

    Date: 17/02/2014

    Supervisor:

    Mr. Teketay.M

    P. Manager:

    Edmeyalem.G

    Date: 17/02/2014

    It is approved that this thesis has been written in compliance with the formatting rules

    laid down by the school of the university.

    Examining Committe Members Signature Date

    1. Chairman

    2. Examiner 1

    3. Examiner 2

    i

  • ii

    Abstract

    Energy is one of the most important requirements for this world to function properly.

    Its availability and regular supply are of paramount interest. As we are all aware,

    energy and fuel prices are rising day by day and the negative effects of global warming

    are more and more visible. The electrification of rural areas using solar energy is very

    economical compare to other Forms of rural electricity supply such as diesel generators

    or grid extension. The rural Electrification involves the power supply to remote houses

    or villages, electrification of the health care facilities, power supply for water supply

    treatment and irrigation etc. This paper focuses on solar home PV system in rural

    area.

  • Acknowledgements

    We would like to express our sincere and firm gratitude and pay a lot of thanks to

    our honorable thesis advisor Mr., Teketay M Department of Computing and Electrical

    Engineering for his constant supervision to carry out the thesis and that make us to

    create a good knowledge and confidence. He extended his helping hand by providing

    us encouragement, inspiration, facilities and valuable feedback throughout the course of

    this thesis..

    iii

  • Contents

    Declaration of Authorship i

    Abstract ii

    Acknowledgements iii

    List of Tables vi

    Abbreviations vii

    1 Introduction 1

    1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

    1.1.1 Photo voltaic system . . . . . . . . . . . . . . . . . . . . . . . . . . 2

    1.1.2 Rural Electrification in Ethiopia. . . . . . . . . . . . . . . . . . . . 3

    1.1.3 Rural Electrification in Ethiopia using Solar PV. . . . . . . . . . . 4

    1.2 Problem of statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

    1.3 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

    1.3.1 General objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

    1.3.2 Specific objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

    1.4 Expected outcome And Significant of the project . . . . . . . . . . . . . . 7

    1.5 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    1.5.1 Load demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    1.5.2 Size the PV modules . . . . . . . . . . . . . . . . . . . . . . . . . . 9

    1.5.3 Battery sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

    1.5.4 Inverter sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

    1.5.5 Solar charge controller design . . . . . . . . . . . . . . . . . . . . . 11

    2 Review of literature 13

    2.0.6 Off-grid pv system . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

    2.0.7 Off-grid pv system in Ethiopia . . . . . . . . . . . . . . . . . . . . 14

    2.0.8 Grid-connected system . . . . . . . . . . . . . . . . . . . . . . . . . 15

    2.0.9 Grid-connected system in Ethiopia . . . . . . . . . . . . . . . . . . 16

    3 System description and over all operation 18

    4 Design and analysis 20

    iv

  • Contents v

    4.0.10 Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

    4.0.11 Photo voltaic array sizing . . . . . . . . . . . . . . . . . . . . . . . 23

    4.0.12 Panel inclination . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

    4.0.13 Battery sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

    4.0.14 Inverter Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

    4.0.15 Charge controller . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

    4.0.16 Selection criteria of cable . . . . . . . . . . . . . . . . . . . . . . . 35

    4.0.17 Balance-of-System (BOS) Requirements . . . . . . . . . . . . . . . 37

    4.1 Result and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

    4.1.1 HOMER Optimization Results . . . . . . . . . . . . . . . . . . . . 38

    5 Conclusion and Recommendation 42

    5.0.2 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

    5.0.3 Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

    6 Bibliography 44

  • List of Tables

    4.1 Load wattages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

    4.2 Ratted wattages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

    4.3 Adjestement factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

    4.4 energy per day . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

    4.6 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

    4.7 Inclination and zenieth angle of north western Ethiopia . . . . . . . . . . 30

    4.8 Inverter spesification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

    4.9 Net present cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

    4.10 Anualized cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

    vi

  • Abbreviations

    PV photo voltaic

    SHS solar home system

    KW kilo watt

    PSH sun shine hour

    DC direct current

    AC alternating current

    MW Mega watt

    Wp Peak power

    NGO Non Governmental Organization

    LED Light Emitting Diode

    SHS Solar Home System

    KWH Kilowatt Hour

    STC Standard Test Condition

    MPPT Maximum Power Point Traking

    MOSFET Metal Oxide Field Effect Transistor

    Amp-Hour Ampere Hour

    DF Derating Factor

    Voc Open circuit voltage

    Ib design current

    In Nominal current

    Cf Correction factor

    Df Diversity factor

    Iz Cable Current Capacity

    Vref Reference Voltage

    Ish Short circuit current

    vii

  • Abbreviations viii

    Iadj Adjustable current

    NOCT Normal Operating Temperature

    EEPCo Ethiopian Electric Power Corporation

    EBCS Ethiopian Building Construction Standard

    MDG Millennium Development Goal

    Hz Harze

  • Chapter 1

    Introduction

    1.1 Background

    Sunlight is the most abundant energy source available to man. It provides us with heat

    to keep us warm, light by which to see, and energy for plants to grow [1]. Dr. David

    Goodstein, a professor of physics at the California Institute of Technology said, The

    total amount of sunlight that falls on the planet is 20,000 times the amount of fossil fuel

    power we are using now. Theres plenty of energy from sunlight.

    In [1] Solar energy is one of the most attractive sources of sustainable energy. It is an

    important clean, cheap and abundant available renewable energy. Alternative energy

    source like solar energy were undermined until fuel price started to rise significantly in

    the last few year. In addition, high initial cost of PV generator was a limiting factor for

    those users to utilize such renewable and clean energy source. Even through this solar

    technology May have a higher starting cost than that of conventional fossil fuel, the low

    maintenance and operation cost and the ability to operate without fuel make the solar

    powered systems cheaper to keep. One of the most resourceful and suitable renewable

    energies that is used in the rural non electrify area is solar power. Solar power or solar

    energy is technology of gaining operational energy from the light of sun. In [1] various

    type of solar system currently available are categorized as follows as follows, Photo bio-

    logic system, Chemical system, Photovoltaic system, and Thermal system.

    Photo biologic system

    Photosynthesis is the oldest and most widespread method of using the solar system .

    in this process, nitrogen and nutrients, needed for the continuation of plants life, are

    1

  • Chapter 1. Introduction 2

    absorbed. the biologic energy stored in the plant is retrieved by burning the wood or

    preparing fuel such as alcohol and the output of this process is between 0.25 to 0.5

    percent and such fuel are rarely used due to their low output [1]. Chemical system

    In [1] named the other type of solar energy systems as chemical solar system that are

    categorized three two groups:

    1. Photo chemical system in which the solar radiation is used in chemical process.

    2. Heliothermic system in which the sun is used as thermal resource. Both groups are

    used in synthesis which needs thermal and radiant.

    Thermal system

    In [1] express that thermal system is now considered as the most economical solar sys-

    tem. This type of system can be categorized as follows:

    1 Cooling and heating systems

    2 Water heating systems

    3 Drying and cooking systems

    4 Desalinating systems

    5 Pumping systems

    6 Electricity generating systems

    7 Green area making systems

    1.1.1 Photo voltaic system

    One of the most common methods currently available for turning sunlight into useful

    energy is by the use of photo voltaic, or solar, cells. Photovoltaic comes from the Greek

    word photo meaning light and volt referring to electricity (Photo watt). Solar cells

    convert light to direct current (DC) electricity by means of the photoelectric effect[3].

    The electricity produced by solar cells may directly power DC machines, be converted

    by an invert er to AC power for use by AC machines or devices, or be used to charge

    batteries. Solar cells have no moving parts and require minimal maintenance beyond

    periodic cleaning of the light-absorbing surface. The phenomenon of the conversion of

    light energy to electrical energy was first discovered by the French physicist Alexander

    Edmond Becquerel in 1839 (Lenardic). In 1905, Albert Einstein made comprehensive

    theoretical studies about photo voltaic technology. He won the Nobel Prize in physics

    in 1921 for his services to Theoretical Physics, and especially for his discovery of the

  • Chapter 1. Introduction 3

    law of the photoelectric effect. Up through the mid-twentieth century, photo voltaic

    technology was limited primarily to scientific research. Bell Laboratories developed the

    first practical silicon-based solar module in 1954 (Chodos). This silicon solar cell, devel-

    oped by Chapin, Fuller, and Pearson, had an energy conversion efficiency of 6 percent

    (Chapin). In 1963, Sharp Corporation successfully began to mass-produce the first so-

    lar cells (Sharp). Early solar cell use was constrained primarily to remote applications

    where no other source of reliable and practical electricity was available. These early ap-

    plications included buildings far from the electrical grid, call boxes on distant highways,

    and space stations and satellites in earth-orbit. The markets interest in early solar cell

    technology was dampened by its low electrical conversion efficiency. Over the last 50

    years, solar cell efficiency has increased while the production costs have decreased [3].

    1.1.2 Rural Electrification in Ethiopia.

    In Rural areas women and children spent their time in searching of fire wood and the

    urban poor also spend a large amount of their income to satisfy their energy demand

    [3]. Ethiopia has a very low amount of electricity generation from hydro and diesel

    generator but this generated amount also will not fully operated due to constraints on

    fuel and maintenance costs of diesel generator [4]. As most of the people live in rural

    areas, the development of these areas is a key for the whole country development. The

    government is taking actions to promote the electrification. For example, in 1996 invest-

    ment proclamation the private investors are allowed to import all types of equipment

    related to electricity production, transmission and distribution free of tax and custom

    duties [4]. There are two main reasons for the low level of electrification. These are

    economic resource constraints and low level of technological advancements. In the rural

    area, the relatively high cost of transmission and distribution due to the mountainous

    and scattered rural settlements makes it costly and the people are unable to pay for the

    electricity and installation [5] [6] . Rural energy problem in Ethiopia will be the cause of

    slow growth and poverty unless actions are taken to overcome this problem. [6]. Educa-

    tion, health, and rural road building programs are considered the main areas for building

    the necessary infrastructure for poverty mitigation. The development of modern energy

    in Ethiopia has got a considerable finance but the rural energy sector does not get a

    fair share of this allocation. One of the main problems for the national energy policy

  • Chapter 1. Introduction 4

    of Ethiopia is there is no organized responsible body for rural electrification except grid

    electricity and petroleum products. Without institutional and managerial structures

    and controls, it is impractical to realize that the stated solutions for the problems of

    rural electrification like mini and micro-hydropower and PV systems [6].

    1.1.3 Rural Electrification in Ethiopia using Solar PV.

    Ethiopia has 15 percent electricity grid coverage with a production of less than 100MW

    of power [7] and its electricity production is mainly from hydro power supplemented

    with diesel. There is a large demand of electricity in rural areas of Ethiopia that could

    be supplied by small scale PV systems. Even though the power requirement for the

    rural population is mainly for grinding cereals and water pumping it plays an important

    role in lighting of homes and schools, vaccination refrigeration and public communica-

    tion centers and for other small electricity consumer appliances. In order to see the

    performance of solar PV under Ethiopian climatic condition two small scale PV stand

    alone systems were installed at Addis Ababa University and it shows PV can be used as

    energy sources [5]. An estimate shows that PV power system demand of 2 Wp can be

    used for light, 10 Wp for light and music for 4 hours per day, 50 Wp and 100 Wp can

    be used for little cinema or a health station with refrigerators [8].

    Ethiopia has a large population with a rapidly growing economy and very low level of

    electrification [9]. Photovoltaic systems are cost-effective and reliable means to increase

    access not only to electricity but also to information and communication through mobile

    devices. PV is already an important source of power for the mobile network in Ethiopia

    it will also be important for of energizing social institutions such as schools, clinics and

    water supply [9]. The large domestic market, increasing disposable incomes, and growing

    technical workforce should enable Ethiopia to develop a sustainable PV manufacturing

    and distribution industry. Its sizable domestic market should also enable it to position

    itself as the regional solar energy hub. It is estimated that a local manufacturing and

    service industry for PV systems can create 50,000 full time skilled jobs by 2020. This,

    however, requires conceptual transformation for the sector the existing sector set up

    is inadequate to achieve this vision. Policy and regulatory issues must be resolved and

    sector development support must be adequately provided. Since new industries are con-

    stantly faced with new challenges the key is to have a strong institution to address them

  • Chapter 1. Introduction 5

    effectively as they appear [2].

    Such an institution could be the rural electrification support unit within the Ministry

    of Water and Energy. This unit must be truly capable and empowered; flexible in its

    operations; and be able to work with industry actors [10]. It should first work to improve

    the policy and regulatory environment, and then attract resources to provide adequate

    sector development support. Today, PV systems have an important use in areas re-

    mote from an electricity grid where they Provide power for water pumping, lighting,

    vaccine refrigeration, electrified livestock fencing, telecommunications and many other

    applications. However, with the global demand to reduce carbon -dioxide emissions, PV

    technology is also gaining popularity as a mainstream form of electricity generation[11].

    Photovoltaic modules provide an independent, reliable electrical power source at the

    point of use, making it particularly suited to remote locations. However, solar PV is

    increasingly being used by homes and offices to provide electricity to replace or supple-

    ment grid power, often in the form of solar PV roof tiles. The daylight needed is free,

    but the cost of equipment can take many years before receiving any payback. However,

    in remote areas where grid connection is expensive, PV can be the most cost effective

    power source[12].

    Nearly all of the about 80 percentof Ethiopians living in rural areas have no access to

    electricity. Excellent solar conditions enable attractive small off-grid PV systems for ru-

    ral population. Their todays energy budget allows short payback periods of only about

    2 to 4 years [12]. As a consequence of high oil prices, even larger PV systems are very

    competitive to diesel generators and village power supply, respectively. Highly economic

    solar systems, available to rural population, generate additional purchasing power and

    open new financial capabilities for sustainable rural development [13].

    Installations of photovoltaic (PV) systems have shown high growth rates around the

    world [14]. Nevertheless, most PV markets need considerable governmental support to

    reach parity with prevailing electricity supply. On the other side, highly economic but

    still small PV markets exist like in Ethiopia, for instance. A sustainable market devel-

    opment of such markets often dominated by small off-grid PV solutions has to consider

    several key success factors for rural electrification. Similar success patterns have been

    observed around the world: adequate system design, training of installers and end-users,

    financing, service and institutional cooperation [15-17].

  • Chapter 1. Introduction 6

    1.2 Problem of statement

    Our current industrial society works only with conventional energy sources like coal, oil,

    natural gases or uranium [11]. Meanwhile, we will have two big problems with them:

    They produce several kinds of pollution s. If we do not care, Atmospheric pollution,

    climate change or nuclear waste can endanger our living condition on the earth.

    After several years the limited energy source will become exhausted, which will not

    guarantee our energy supply in the future.

    On the opposite side, the renewable energy sources use natural flows. These renewable

    energy sources only use a small part of the flow that is why they cannot damage natural

    surroundings. One of these natural resources is solar power and there are several ways

    to use it. One of them is to produce electricity [16]. Solar energy can be used instead of

    fossil fuel or diesel. The decision as to what type of source of energy is utilized in each

    case must be made on the basis of economic, environmental and safety consideration

    [13]. Because of the desirable environment and safety aspect is widely believed that

    solar should be utilized of other alternative energy forms, because it can be provided

    sustainability without harming the environment. Most of our country rural areas do not

    have electric access by the basis of economic aspects, geographical topology and other

    problems like dispersedly populated area [10]. This problem in fact, the energy crisis is

    believed to the most series problem in our rural area. Ethiopia, beside to persisting food

    in security, it suffering from energy underutilized result of studies and recent data on

    the energy requirement of the country indicates that the energy consumption increase in

    proportional to the gross national products. One of the possible remedy for overcoming

    energy crisis is by increasing the use of renewable energy source such as solar energy [15].

    Our project purposely focuses on to eradicate this type of problem by using solar energy.

    1.3 Objectives

    1.3.1 General objective

    The objective of our project is to design Off-grid photovltaic system for veterinary clinic

    in remote area of the our country.

  • Chapter 1. Introduction 7

    1.3.2 Specific objective

    I To sizing PV system

    I To sizing battery

    I To specify invert er controlling

    I To design battery charger controlling

    1.4 Expected outcome And Significant of the project

    Solar PV based rural electrification is becoming a common phenomenon in Ethiopia,

    where people are settled in a scattered pattern which created problems for grid elec-

    trification. Both government and non-governmental organization are involved in the

    process. Solar Energy Foundation (Stiftung Solar energies), a charitable nongovernmen-

    tal organization established in 2006 by Dr. Harald Schtzichel, with main aims of poverty

    alleviation in developing countries by promoting the use of renewable energy, especially

    solar energy. This organization is working in rural electrification mainly in Ethiopia by

    using model projects [8]. The rural people of our country are highly dispersed, so in

    order to electrify and fulfill their electrical power demand, modular and flexible power

    source system preferable. Therefore solar PV system is significantly important. In ad-

    dition it is important with respect to

    I Environmental impact

  • Chapter 1. Introduction 8

    I Reducing cost etc.

    Designing and implementing solar PV from easily available solar energy for rural

    area could alleviate the problem of electrical power scarcity.

    1.5 Methodology

    The project began with a literature review of solar photovoltaic systems. This was fol-

    lowed by a simple prefeasibility study to obtain an idea of the amount of energy that will

    be generated by the system, estimate the total space (area) required for the installation

    of the system and access the economics of the whole project. A draft procedure for the

    design of grid- off systems for rural clinic was prepared which will be updated from time

    to time until a standard procedure is developed which can be used to replicate the design

    of large-scale grid-off solar PV systems in other institutions. The draft procedure com-

    prises the following steps; Numerous optimal sizing methodologies for grid-off systems

    have been developed including analytical solutions and numerical method approaches.

    Which claims that can bring the price of grid-off systems to economic viability at todays

    fuel prices.

    1.5.1 Load demand

    The first step in designing a solar PV system is to find out the total power and energy

    consumption of all loads that need to be supplied by the solar PV system as follows:

    Calculate total Watt-hours per day for each appliance used: Add the Watt-hours needed

    for all appliances together to get the total Watt-hours per day which must be delivered

    to the appliances.

    Calculate total Watt-hours per day needed from the PV modules: To get the optimum

    output wattages from PV generator by consideration of inverter and wire efficiency. This

    quantity is used as a power adjustment factor when current is changed from dc to ac.

    The efficiency of the inverter selected for this application is assumed to be 0.9 and wire

    efficiency o.5.

    Calculate total Energy demand per day: The amount of energy each appliance requires

    per day is determined by multiplying each appliances adjusted wattage by the number

  • Chapter 1. Introduction 9

    of hours used per day.

    The Sum of the energy per day determines the total energy demand required by the

    appliances per day.

    Calculate Total amp-hour demand per day: The battery storage subsystem is sized inde-

    pendently of the photovoltaic array. In order to size the battery bank the total electrical

    load is converted from watt-hours to amp-hours. Amp-hours are determined by dividing

    the total energy demand per day by the battery bus voltage.

    Calculate maximum ac power requirement: The sum of the rated wattages for all appli-

    ances gives maximum ac power.

    1.5.2 Size the PV modules

    The size of the photovoltaic array is determined by considering the available solar insu-

    lation, the tilt and orientation of the array and the characteristics of the photovoltaic

    modules being considered.

    Assessment of the solar radiation data for the location from various institutions such as

    the Ethiopia metrology which helps to estimate the amount of electricity generated.

    Obtain a suitable place that can be used for the solar module

    ]Calculate required array output per day: The watt-hours required by the load are ad-

    justed (upwards) because batteries are less than 100 percent efficient. Dividing the total

    energy demand per day by the battery round trip efficiency determines the required

    array output per day.

    Selected PV module max power voltage at STC x 0.85. Maximum power voltage is ob-

    tained from the manufacturers specifications for the selected photovoltaic module, and

    this quantity is multiplied by 0.85 to establish a design operating voltage for each mod-

    ule (not the array) to the left of the maximum power voltage and to ensure acceptable

    module output current.

    Calculate Energy output per module per day: The amount of energy produced by the

    array per day during the worst month is determined by multiplying the selected photo-

    voltaic power output at STC by the peak sun hours at design tilt (5hour).

    Number of modules required to meet energy requirements: the required output per day

  • Chapter 1. Introduction 10

    by the module energy output at operating temperature determines the number of mod-

    ules required to meet energy requirements.

    Number of modules required per string: the battery bus voltage by the module design

    operating voltage, and then rounding this figure to the next higher integer determines

    the number of modules required per string.

    Number of string in parallel: the number of modules required meeting energy require-

    ments by the number of modules required per string and then rounding this figure to

    the next higher integer determines the number of string in parallel.

    Nominal rated array output: Multiplying the number of modules to be purchased by the

    nominal rated module output determines the nominal rated array output. This number

    will be used to determine the cost of the photovoltaic array.

    1.5.3 Battery sizing

    The battery type recommended for using in solar PV system is deep cycle battery. Deep

    cycle battery is specifically designed for to be discharged to low energy level and rapid

    recharged or cycle charged and discharged day after day for years. The battery should

    be large enough to store sufficient energy to operate the appliances at night and cloudy

    days. To find out the size of battery by considering the following factors:

    The location where batteries are stored should be designed to minimize fluctuations in

    battery temperature. For this application the design temperature is assumed to be 25

    degrees C.

    The battery storage system is designed to provide the necessary electrical energy for a

    period equivalent to 3 days without any sunshine.

    The allowable depth- of-discharge is for concerning of life time of battery.

    ]The required battery capacity is determined by first multiplying the total amp-hours

    per day by the days of storage required and then dividing this number by the allowable

    depth of discharge.

    Once the required number of amp-hours has been determined, batteries or battery cells

    can be selected using manufacturers information.

  • Chapter 1. Introduction 11

    ]The number of batteries in parallel or battery cells needed to provide the required bat-

    tery capacity by the amp-hour capacity of the selected battery.

    The number of batteries in series is needed to provide the necessary dc system voltage

    is determined by dividing the battery bus voltage by the selected battery or battery cell

    voltage (taken from manufacturers information) Battery voltage.

    The total rated capacity of selected batteries is determined by multiplying the number

    of batteries in parallel by the amp-hour capacity of the selected battery.

    Based on the selected batteries, the kWh or energy capacity is determined by first mul-

    tiplying the total amp-hour capacity times the battery bus voltage and then dividing

    this number by 1000.

    1.5.4 Inverter sizing

    An inverter is used in the system where AC power output is needed. The input rating of

    the inverter should never be lower than the total watt of appliances. The inverter must

    have the same nominal voltage as your battery.

    For stand-alone systems, the inverter must be large enough to handle the total amount

    of Watts you will be using at one time. The inverter size should be 25-30 percent bigger

    than total Watts of appliances. In case of appliance type is motor or compressor then

    inverter size should be minimum 3 times the capacity of those appliances and must be

    added to the inverter capacity to handle surge current during starting.

    1.5.5 Solar charge controller design

    Initially, a maximum power point tracking (MPPT) charge controller was planned for

    use in this project. MPPT charge controllers are generally switched mode DC-DC con-

    verters which vary the switching duty cycle to regulate the RMS output voltage to match

    the charging voltage of the battery, while maintaining the input voltage at the maxi-

    mum power point. However, all MPPT controllers researched were priced in the range

    of 200400. Therefore, a less expensive solution had to be found.

    Instead of using MPPT controller, the controller in this project was designed using two

    LM317 voltage regulators, a TLV2304IP dual comparator; two N-channels STD95NH02L

  • Chapter 1. Introduction 12

    power MOSFET chips, a two blocking diode and 9V battery. The comparator detects

    when the battery is fully charged by comparing the terminal voltage to a regulated 28.4

    V reference. When the battery terminal voltage exceeds 28.4, the comparator sends

    a low signal to the gate of a charging MOSFET between the battery and the solar

    panel, opening the circuit to prevent overcharging. Similarly, the comparator detects

    when the battery is at its lowest allowable state of charge by comparing its voltage to

    a regulated 21.5 V reference. When the battery terminals are at this minimum voltage,

    the comparator sends a low signal to the gate of a MOSFET connected between the

    battery terminals and the inverter, opening the circuit and disconnecting the load. See

    the figure below the control circuit connects to the other subsystems. Although at full

    charge the terminal voltage is about 28 volts, the battery must charge to 28.4 V to over-

    come its charging resistance, caused by internal pressure within the charging battery cell.

    .

  • Chapter 2

    Review of literature

    he first PV systems were installed in Ethiopia in the mid 1980s - these systems were

    installed for rural home lighting and for school lighting [11]. The largest of these was a

    10.5kWp system installed in 1985 in Central Ethiopia which served 300 rural households

    through a micro grid in the village. This system was later upgraded to 30kWp in 1989

    to provide power for the village water pump and grain mill. PV installations in the

    early days were mainly project based government and NGO action and systems were

    provided as grant to users. Project based installations are still important, particularly

    for institutional systems (schools, health centers, and water pumps)[13]. However, both

    government and NGOs now realize that only market based interventions will enable

    wider dissemination and also sustainability; they now combine project (grant) based

    actions with market mechanisms and focus on market and capacity development. It is

    estimated that a total of some 5.3MWp of PV is now in use in Ethiopia. The main

    area of application for PV is now off-grid telecom systems (particularly for mobile and

    land mine network stations) which account for 87 percent of total installations. PV

    systems are also used in social institutions including health stations, schools and for

    water pumping. Some thirty thousand residential customers are also electrified with PV

    in rural areas [13].Photovoltaic systems can be grouped into two main groups; namely

    off-grid systems and grid-connected systems.

    13

  • Chapter 2. Literature review 14

    2.0.6 Off-grid pv system

    Off-grid PV systems, as the name implies, are systems that are not connected to the

    public electricity grid. These systems require an energy storage system for the energy

    generated because the energy generated is not usually required at the same time as it

    is generated. In other words, solar energy is available during the day, but the lights

    in a stand-alone solar lighting system are used at night so the solar energy generated

    during the day must be stored for use in the night. They are mostly used in areas

    where it is not possible to install an electricity supply from the mains utility grid, or

    where this is not cost-effective or desirable. They are therefore preferable for developing

    countries where vast areas are still frequently not supplied by an electrical grid. Off-grid

    systems are usually employed in the following applications; consumer applications such

    as watches and scientific calculators, industrial applications such as telecommunications

    and traffic signs and remote habitations such as solar home systems and water pumping

    applications[12]. A typical off-grid system comprises the following main components:

    Solar PV Modules: these convert sunlight directly to electricity.

    Charge Controllers: manage the charging and discharging of the batteries in order to

    maximize their lifetimes and minimize operational problems.

    Battery or Battery Bank: Stores the energy generated by the PV modules.

    Invert er: converts the DC current generated by the solar PV modules to AC current

    for AC consumer load.

    2.0.7 Off-grid pv system in Ethiopia

    The outlook for the solar electricity sector in Ethiopia is for rapid increase in installation

    for off-grid applications and later for grid connected applications. Off-grid applications

    will be dominant in the short term but grid connected PV may become important in

    the medium and long term. Short term plans that have direct relevance for the PV

    sector include plans to disseminate more than 3 million PV home systems and plans

    to increase mobile ownership to 40 million[11]. In 2005 off-grid PV solar home systems

    (SHS) in Ethiopia consist of a 10 Wp PV module, charge and remote controller, 18 Ah

    gel lead acid battery, two 50 lm/W LED lamps and one plug for a radio or tape recorder

    was done. Commonly two kerosene lamps are used by one family plus optionally one

  • Chapter 2. Literature review 15

    radio or tape recorder powered by dry cell batteries [13]. Off-grid telecom applications

    now account for 87 percent of the total installed PV capacity in Ethiopia [10]. Strong

    growth is foreseen in the coming ten years for this segment due to the drive for universal

    access to mobile connectivity (the plan is for 90 percent mobile network coverage and for

    40million mobile users by 2015 ). This will result in doubling of installed PV capacity

    by 2015 then again doubling by 2020. This will be public sector driven demand and is

    highly likely to be realized [16]. Off-grid residential applications will be an important

    segment of the demand for PV in the medium to long term. The demand for this seg-

    ment of the market will be mainly private sector driven and will depend on policies and

    regulations in place. Existing government plans for 3 million solar lanterns and home

    systems is expected to spur rapid growth increasing installed capacity by tenfold in the

    next five years. Off-grid institutional applications will also be important in the short

    term [15].

    2.0.8 Grid-connected system

    Grid-connected systems are systems connected to a large independent grid usually the

    public electricity grid and feed power directly into the grid. These systems are usu-

    ally employed in decentralized grid-connected PV applications and centralized grid-

    connected. Decentralized grid-connected PV applications include rooftop PV genera-

    tors, where the PV systems are mounted on rooftops of buildings and incorporated into

    the buildings integrated system. In the case of residential or building mounted grid

    connected PV systems, the electricity demand of the building is served by the PV sys-

    tem and the excess is fed into the grid; their capacities are usually in the lower range of

    kilowatts [15]. A typical grid-connected PV system comprises the following components:

    Solar PV Modules: these convert sunlight directly to electricity.

    Invert er: converts the DC current generated by the solar PV modules to AC current

    for the utility grid.

    Main disconnect/isolator Switch.

    Utility Grid Central grid-connected PV applications have capacities ranging from the

    higher kilowatts to the megawatt range. Solar PV is currently the fastest growing power

    generation technology in the world with about 38,584MW capacity installed in the year

    2010 [8]. In all, Europe alone contributes about 70 percent of the total installed capacity

  • Chapter 2. Literature review 16

    of PV systems with North America, Japan, China and Australia following in that order

    [2]. The solar PV industry has also seen tremendous improvement in cell efficiencies for

    the various technologies available on commercial scale. This improvement in technology

    and the continuous growth of the PV market has led to drastic reduction in the cost

    of solar PV systems on the global market. The situation on the African continent is

    however not encouraging, with Africa contributing less than 1 percent of the worlds

    installed solar PV systems (installed capacity of 163 MW as at the end of 2010), in spite

    of the huge solar energy potential available to the continent [4] . This is as a result

    of the lack of policy instruments that help promote renewable energy technologies in

    general and also the very high initial capital involved in developing solar PV systems.

    Grid-connected solar PV systems are not that popular in Africa since most solar PV

    applications are employed in off-grid rural electrification projects to rural communities

    (for lighting, educational and health applications) that are far from the national grid [17].

    2.0.9 Grid-connected system in Ethiopia

    Present PV system prices are so low that they are becoming competitive with some

    thermal systems. Grid parity will come later in developing countries because of gener-

    ally lower generation and transmission costs for the grid [17]. However, cost of power

    generation on the grid is rising while PV prices are dropping closing the cost gap. This

    is opening up the market for grid connected PV and governments are now considering

    them as feasible alternatives [13]. For example, the 265MW Aleltu West hydropower

    plant planned to be commissioned in 2019 will cost USD 0.072/kWh (EAPP, 2011).

    Transmission and distribution will add USD 0.04/kWh Increasing delivered cost to USD

    0.12/kWh. In this case PV can reach grid parity if installed cost (Including PV modules,

    inverter, other auxiliary equipment and service charges) declines to USD 3/W4 this is

    very likely to happen in the coming five to ten years [10]. Local production of PV com-

    ponents may lower production costs; and expanding market for PV systems will lower

    costs of distribution and installation. These two together will reduce installed cost for

    PV and cut the length of time required for grid parity.

    Solar PV system includes different components that should be selected according to

    your system type, site location and applications. The major components for solar PV

  • Chapter 2. Literature review 17

    Figure 2.1: Pv demand in Ethiopia

    system are solar charge controller, inverter, battery bank, auxiliary energy sources and

    loads (appliances).

    Module converts sunlight into DC electricity.

    Solar charge controller regulates the voltage and current coming from the PV

    panels going to battery and prevents battery overcharging and prolongs the battery

    life.

    Converts DC output of PV panels or wind turbine into a clean AC current for AC

    appliances or fed back into grid line.

    Battery stores energy for supplying to electrical appliances when there is a de-

    mand.

    Load is electrical appliances that connected to solar PV system such as lights,

    radio, TV, computer,refrigerator, etc.

    The solar panels when exposed to sunlight generate DC electricity.

    The DC power goes to a battery bank for storing, that are used for during rainy

    season and when the sun goes down.

    The DC power goes through a solar inverter which is a critical component in a

    solar energy system. It performs the conversion of the variable DC output of the

    Photovoltaic (PV) module(s) into a clean sinusoidal 50- or 60 Hz AC current that

    is then applied directly to the load.

  • Chapter 3

    System description and over all

    operation

    Solar PV system includes different components that should be selected according to your

    system type, site location and applications. The major components for solar PV system

    are solar charge controller, inverter, battery bank, auxiliary energy sources and loads

    (appliances).

    Solar PV system includes different components that should be selected according to your

    system type, site location and applications. The major components for solar PV system

    are solar charge controller, inverter, battery bank, auxiliary energy sources and loads

    (appliances).

    Converts sunlight in to DC electricity.

    Solar charge controller regulates the voltage and current coming from the PV

    panels going to battery and prevents battery overcharging and over discharging

    prolongs the battery life.

    converts DC output of PV panels or wind turbine into a clean AC current for AC

    appliances or fed back into grid line.

    18

  • Chapter 3. System description and over all operation 19

    Battery stores energy for supplying to electrical appliances when there is a de-

    mand.

    Load is electrical appliances that connected to solar PV system such as lights,

    radio, TV, computer, refrigerator, etc.

    controller.PNG controller.PNG

    Figure 3.1: Charge controller

    The solar panels when exposed to sunlight generate DC electricity. The DC power goes

    to a battery bank for storing, that are used for during rainy season and when the sun goes

    down. In this project battery charge regulator are design by using two LM317 voltage

    regulators, TLV2304IP dual comparator, two N-channels STD95NH02L power MOSFET

    chips, a two blocking diode and 9V battery. The comparator detects when the battery is

    fully charged by comparing the terminal voltage to a regulated 28.4 V reference. When

    the battery terminal voltage exceeds 28.4, the comparator sends a low signal to the gate

    of a charging MOSFET between the battery and the solar panel, opening the circuit to

    prevent overcharging. Similarly, the comparator detects when the battery is at its lowest

    allowable state of charge by comparing its voltage to a regulated 21.5 V reference. When

    the battery terminals are at this minimum voltage, the comparator sends a low signal

    to the gate of a MOSFET connected between the battery terminals and the inverter,

    opening the circuit and disconnecting the load. See the figure below the control circuit

    connects to the other subsystems. The DC power goes through a solar inverter which is

    a critical component in a solar energy system. It performs the conversion of the variable

    DC output of the Photovoltaic (PV) module(s) into a clean sinusoidal 50- or 60 Hz AC

    current that is then applied directly to the load.

  • Chapter 4

    Design and analysis

    4.0.10 Load

    return

    Table 4.1: Load wattages

    Appliance amount wattage hours per day

    Microscope 2 20 4

    Autoclave 1 2000 3

    Fluorescent 4 40 10

    Refrigerator 1 90 12

    Fan 2 60 7

    I Inverter and wire efficiency (decimal). This quantity is used as a power adjust-

    ment factor when current is changed from dc to ac. The efficiency of the inverter

    selected for this application is assumed to be 90 percent and the efficiency of the

    wire selected for this application is assumed to be 95 percent.gnerally 85 pecent.

    I Battery bus voltage. This is nominal dc operating voltage of the system. The bat-

    tery bus voltage for this application is 24 volts. Which corresponds to the required

    dc input voltage for the inverter.

    I ac voltage. The output voltage of the inverter selected for this application is 220

    volts.

    20

  • Chapter 4. Design and analysis 21

    The components (appliances) that the system will power are:

    Microscope (20 watt each, combined rated wattage 40, used 4 hours/ day) Fan

    (rated wattage 60, used 7 hours/day) Autoclave (rated wattage 2000, used 3

    hours/day) Fluorescent (rated wattage 40, used 10 hours/day) Refrigerator (rated

    wattage 90, used 12 hours/day)

    I The rated wattage is listed for each appliance in the above. Note that the rated

    wattage for some appliances may vary from the actual power consumed due to the

    load variation or cycling.

    Table 4.2: Ratted wattages

    appliance rated wattage

    Microscope 40

    Fan 60

    Autoclave 2000

    Fluorescent 40

    Refrigerator 90

    I Adjustment factor. The adjustment factor is related to the efficiency of the in-

    verter and a wire reflects the actual power consumed from the battery bank to

    operate ac loads from the inverter. For this application the adjustment factor is

    0.85.

    I Adjusted wattage. Dividing the rated wattage by the adjustment factor adjusts

    the wattage to compensate for the inverter and wire inefficiency and gives the

    actual wattage consumed from the battery bank.

  • Chapter 4. Design and analysis 22

    Table 4.3: Adjestement factors

    Appliance adjustement facter adjusted watt ages

    Microscope 40/0.85 47

    Fan 120/0.85 141

    Autoclave 2000/0.85 2353

    Fluorescent 160/0.85 188

    Refrigerator 90/0.85 106

    I Energy per day. The amount of energy each appliance requires per day is deter-

    mined by multiplying each appliances adjusted wattage by the number of hours

    used per day.

    Table 4.4: energy per day

    appliance hours per day energy per day

    Microscope 47 * 4 188

    Fan 141 * 7 987

    Autoclave 2353 * 3 7059

    Fluorescent 188 * 10 1880

    Refrigerator 106 * 12 1272

    I Total energy demand per day. The Sum of the Quantities determines the total

    energy demand required by the appliances per day. For this application the total

    energy per day for the load is 11386 watt-hours.

    I Total amp-hour demand per day. The battery storage subsystem is sized inde-

    pendently of the photovoltaic array. In order to size the battery bank the total

    electrical load is converted from watt-hours to amp-hours. Amp-hours are deter-

    mined by dividing the total energy demand per day by the battery bus voltage.

    11386 watt-hours/24 volts = 474.42 amp-hours

  • Chapter 4. Design and analysis 23

    I Maximum ac power requirement. The sum of the rated wattages for all appliances

    is equal to 2410 watts. Note that this is the maximum continuous power required

    and does not include surge requirements. This value is the maximum continuous

    ac power output required of the inverter if all loads were to operate simultaneously.

    The Peak, or surge requirement must also be considered when selecting an inverter.

    I Maximum dc power requirement. The sum of the adjusted wattages, or dc power,

    for all appliances is equal to 2835 watts. This value is the maximum dc input

    power required by the inverter and is necessary to determine wire sizes fusing and

    disconnect requirement. If load management techniques are employed to eliminate

    the possibility of loads operating simultaneously, the inverter maximum output

    requirements may be reduced accordingly.

    Inverter efficiency ......... 85 percent

    Battery bus voltage.......... 24 volts

    Inverter ac voltage ......... 220 volt

    I Total energy demand per day.......11386 watt-hours

    I Total amp-hour demand per ........... 474.42 amp-hours

    I Maximum ac power requirement ....... 2410 watts

    I Maximum dc power requirement ....... 2835 watts

    4.0.11 Photo voltaic array sizing

    The size of the photovoltaic array is determined by considering the available solar insu-

    lation, the tilt and orientation of the array and the characteristics of the photovoltaic

  • Chapter 4. Design and analysis 24

    modules being considered. The array is sized to meet the average daily load require-

    ments for the month or season of the year with the lowest ratio daily insulation to the

    daily load.

    The available insulation striking a photovoltaic array varies throughout the year and is

    a function of the tilt angle and azimuth orientation of the array. If the load is constant,

    the designer must consider the time of the year with the minimum amount of sunlight.

    Knowing the insulation available (at tilt) and the power output required, the array can

    be sized using module specifications supplied by manufacturers. Using module power

    output and daily insulation (in peak sun hours), the energy (watt-hours or amp-hours)

    delivered by a photovoltaic module for an average day can be determined. Then, know-

    ing the requirements of the load and the output of a single module, the array can be

    sized.

    The array is sized to meet the average daily demand for electricity during the worst

    insulation month of the year, which is August in North western Ethiopia. The array

    will face south and because the sun is low in the sky during August will be tilted at an

    angle of 11.78 degrees from the horizontal in order to maximize the insulation received

    during August.

    DESIGN MONTH: August

    DESIGN TILT: 11.78 degrees for maximum insulation during the year.

    I Total energy demand per day: 11386 watt-hours

    I Battery round trip efficiency. A factor between 0.70 and 0.85 is used to estimate

    battery round trip efficiency. For this application 0.85 is used because the battery

    selected is relatively efficient and because a significant percentage of the energy is

    used during daylight hours.

    I Required array output per day: The watt-hours required by the load are adjusted

    (upwards) because batteries are less than 100 percent efficient. Dividing the total

    energy demand per day by the battery round trip efficiency determines the re-

    quired array output per day.

    = ( 11386 watt-hours) / (0.85)

  • Chapter 4. Design and analysis 25

    = 13395.294 watt-hours.

    I Selected PV module max power voltage at STC x 0.85: Maximum power voltage

    is obtained from the manufacturers specifications for the selected photovoltaic

    module, and this quantity is multiplied by 0.85 to establish a design operating

    voltage for each module (not the array) to the left of the maximum power voltage.

  • Chapter 4. Design and analysis 26

    Table 4.6: electrical characteristics

    Model No RDM-100M

    Pmax 100 w watt

    Power Tolerance 10

    Max Volt. 18.80 Volt

    Max Current 5.05 Amp

    Open circuit Voltage 22.3 Volt

    Short circuit Current 5.1 Amp

    Max System Volt 1000 VoltDC

    Cell Size 125 x 125 Mm

    Bypass Diodes -Junction Box 12 Amp

    Max. Series Fuse Rating 12A mp

    Temp coe of Isc +0.04 Percent / C

    of Cells per Module 36 Pcs

    Cell Type Mono-crystalline Silicon

    Temp of Voc -0.38 Percent / C

    Temp of Power -0.47 Percent / C

    NOCT 48 2 C

    Operating Temp -40 +85 C

    STC AM 1.5,1000 W/ m 2, 25 C

    mechanical characteristics

    Dimensions 1200 * 540*30 Mm

    Weight 8.00 Kg

    Junction Box TUV certified, IP65

    Cable Diameter TUV certified 4mm sqr

    Connector compatible to Type 4 (MC4)

    Frame 30mm thickness, Aluminum

    RDM-100M modules are used in this application. The maximum power voltage at STC

    for the RDM-100M Solar is 18.80 volts

    = (18.80 volts * 0.85) = 15.98 volt. Selected PV module guaranteed power output at

    STC: This number is also obtained from the manufacturers specifications for the selected

    module. The above table shows the nominal power output at 1000 watts/meter square

  • Chapter 4. Design and analysis 27

    and 25 degrees C is 100 watts. The guaranteed power output is 90 percent of this value,

    or 90 watts.

    Peak sun hours at optimum tilt: This is obtained from solar radiation data for the design

    location and array tilt for an average day during the worst month of the year. Peak sun

    hours at Latitude + 11.56 degrees for north western Ethiopia in august equal 5.85h.

    I Energy output per module per day: The amount of energy produced by the array

    per day during the worst month is determined by multiplying the selected photo-

    voltaic power output at STC by the peak sun hours at design tilt.

    = (90 watts) * (5.85 hours) = 526.5 Watt-hour.

    I Module energy output at operating temperature: A de-rating factor of 0.90 (for

    moderate climates and non-critical applications) is used in this application to de-

    termine the module energy output at operating temperature. Multiplying the

    de-rating factor (DF) by the energy output module establishes an average energy

    output from one module.

    = (526.5Watt-hour) * (0.90) = 473.85 Watt-hour.

    I Number of modules required to meet energy requirements: Dividing the required

    output per day by the module energy output at operating temperature determines

    the number of modules required to meet energy requirements.

    = (13395.294 watt-hours) / (473.85 Watt-hour) = 28.02 module (28 module)

    I Number of modules required per string: Dividing the battery bus voltage by the

    module design operating voltage, and then rounding this figure to the next higher

    integer determines the number of modules required per string.

    = (24Volt) / (15.98 volt) = 1.5 (rounded to 2 modules).

    I Number of string in parallel: Dividing the number of modules required to meet

    energy requirements by the number of modules required per string and then round-

    ing this figure to the next higher integer determines the number of string in parallel.

    = (28 module) / (2 modules) = 14 modules.

  • Chapter 4. Design and analysis 28

    I Number of modules to be purchased: Multiplying the number of modules required

    per string by the number of strings in parallel determines the number of modules

    to be purchased.

    = (2 modules) * (14 modules) = 28 modules.

    I Nominal rated PV module output: The rated module output in watts as stated by

    the manufacturer. Photovoltaic modules are usually priced in terms of the rated

    module output (dollar/watt). The RDM-100M rated module power is 100 watts.

    I Nominal rated array output: Multiplying the number of modules to be purchased

    by the nominal rated module output determines the nominal rated array output.

    This number will be used to determine the cost of the photovoltaic array.

    = (28) * (100 watts) = 2800Watts.

    4.0.12 Panel inclination

    Selection of a sufficiently sized panel is crucial, to ensure that it generates enough energy

    to replace that used by the load or lost to inefficiency. To aid in these calculations, peak

    sunlight hours are determined, and are defined as the number of hours of peak isolation

    (such as, at solar noon) that would produce the same amount of energy as the variable

    isolation dispersed throughout an entire day. According to weather data taken from [23]

    in north-western Ethiopia august period has low peak sunshine hours, averaging about 5

    peak sunlight hours per day. This means that a solar panel can collect an equal amount

    of energy in 5 hours of peak sunlight as it could throughout the day with varying sunlight.

  • Chapter 4. Design and analysis 29

    Figure 4.1: Solar insulation

    To help the panel maximize its output, the inclination can be adjusted monthly to match

    the Suns zenith angle. To find the zenith angle, the latitude and the daily declination

    angle must be known. Zenith angle is calculated according to the following equation,

    Zenith Angle = Declination Angle - Latitude

    Where negative angles correspond to southern latitudes and south tilting panels. The

    latitude for North-western Ethiopia is 11.56 degrees N. The equation for determining

    the declination angle is as:

    Declination Angle = 23.45 * sin [(360/365)*(284+n)]

    Where the variable n is the day of the year, beginning with n=1 on January first.

    Below (Table) is the table of inclination angles calculated by month for North-western

    Ethiopia.

  • Chapter 4. Design and analysis 30

    Table 4.7: Inclination and zenieth angle of north western Ethiopia

    No Month Days Declination angle Zenith angle

    1 January 15 -21.28 -32.8

    2 February 46 -13.32 -24.9

    3 March 75 -2.46 -14.02

    4 April 106 9.74 -1.82

    5 May 136 19 7.44

    6 June 167 23.35 11.79

    7 July 197 21.378 9.82

    8 August 228 13.5 1.946

    9 September 259 1.881 -9.678

    10 October 289 -9.9 -21.46

    11 November 330 -21.32 -32.88

    12 December 350 -23.36 -34.9

    A zenith angle of -11.78 degrees means that the panel should be tilted 11.78 degrees

    due South. This data matches the data shown in Figure, below, which shows the Suns

    elevation and hour angle by date and time. The tangential axis measures the Suns hour

    angle throughout the day, measured from North, and the radial axis measures the eleva-

    tion angle above the horizon. Note that the orange line represents the Suns location on

    December 21, 2013, when this graph was obtained. The zenith angle is defined as the

    Suns elevation angle above the horizon When its hour angle is 180 degrees, due South.

    The zenith angle in Figure is approximately 35.5.

  • Chapter 4. Design and analysis 31

    path.PNG path.PNG

    Figure 4.2: Suns hour angle

    4.0.13 Battery sizing

    DESIGN TEMPERATURE

    The location where batteries are stored should be designed to minimize fluctuations in

    battery temperature. For this application the design temperature is assumed to be 25

    degrees centigrade.

    I Days of storage desired/required (autonomy). The loss of electricity for the resi-

    dence in this application, although undesirable, would not be catastrophic. Conse-

    quently, the battery storage system is designed to provide the necessary electrical

    energy for a period equivalent to 3 days without any sunshine.

    I Allowable depth-of-discharge limit (decimal). The maximum fraction of capacity

    that can be withdrawn from the battery which specified by the designer. Note that

    the battery selected must be capable of this limit or greater depth of discharge.

  • Chapter 4. Design and analysis 32

    For this application the allowable depth- of-discharge is 0.8.

    I Required battery capacity. The required battery capacity is determined by first

    multiplying the total amp-hours per day by the days of storage required and then

    dividing this number by the allowable depth of discharge limit and battery effi-

    ciency.

    474.42 X (3 / [0.8]) = 1779.075 amp-hours.

    I Amp-hour capacity of selected battery. Once the required number of amp-hours

    has been determined above, batteries or battery cells can be selected using man-

    ufacturers information. Exide 3E120-17 industrial grade batteries were selected

    for this application because of their long cycle life and rugged construction [24].

    Exide 3E120-17s Shows that capacity for a 3 day rate is 1077 amp-hours. Since

    battery capacity may vary with the rate of discharge, the amp-hour capacity that

    corresponds to the required days of storage should be used.

    I Number of batteries in parallel. The number of batteries or battery cells needed

    to provide the required battery capacity by the amp-hour capacity of the selected

    battery.

    1779.075 amp-hours / 1077 amp-hours = 2 (round up from 1.65).

  • Chapter 4. Design and analysis 33

    Figure 4.3: Battery selection

    I Number of batteries in series. The number of batteries needed to provide the nec-

    essary dc system voltage is determined by dividing the battery bus voltage by the

    selected battery or battery cell voltage (taken from manufacturers information).

    24 volts / 6 volts = 4.

    I Total Number of batteries. Multiplying the number of batteries in parallel by the

    number of batteries or battery cells in series, determines the total number of bat-

    teries needed.

    4 x 2 = 8.

    I Total battery amp-hour capacity. The total rated capacity of selected batteries

    is determined by multiplying the number of batteries in parallel by the amp-hour

    capacity of the selected battery.

    2 x 1077 amp-hours = 2154 amp-hours.

    I Total battery kilowatt-hour capacity. Based on the selected batteries, the kWh

    or energy capacity is determined by first multiplying the total amp-hour capacity

  • Chapter 4. Design and analysis 34

    times the battery bus voltage, and then dividing this number by 1000.

    [2154 amp-hours x 24 volts] / 1000 = 51.67 kilowatt-hour.

    4.0.14 Inverter Selection

    The AIMS 3000 W Modified pure Sine Wave Inverter was selected for its output voltage

    220 V, 50 Hz AC and for its low retail price of dollar. I80t has a nominal maximum

    output power of 3000 W, so it can easily supply the 24 DC volt. Additionally, it has

    shutoff features to protect from low or high DC input voltages and high AC currents. See

    the Table below, for the nominal minimum and maximum DC voltages and maximum

    AC current, as provided by the manufacturer.

    Table 4.8: Inverter spesification

    Rated capacity 3000 w

    Model AIMS 4000-221 model

    Nominal voltage 220 volt

    Optimum efficiency 90 percent

    Transfer time Ac to DC: 10 ms (typical)

    Rated current 40 Ampere 50Hz

    Frequency 50 Hz

    Load Current Draw less than 1A(24V)

    Low Battery Alarm 21.5 23V

    Auto Low Battery Shutdown 20.5 22V

    Cooling Fan double

    Certification CE ,RoHS, FCC

    4.0.15 Charge controller

    One problem encountered when designing this control circuit was that that the regu-

    lated outputs needed from the LM317 linear regulators were either above the battery

    voltage or less than 1.5 volts below it. Therefore, to ensure that the input voltage to the

  • Chapter 4. Design and analysis 35

    regulators was high enough above the desired output, a 9 V battery was connected in

    series with the 24 V batteries to supply a nominal input voltage of 33 V to the LM317

    chips. This ensured that the regulated reference voltages would remain constant and

    accurate while allowing for any necessary internal voltage drops within the regulators.

    The 24 V regulators uses an R1 value of 240 Ohms and an R2 value of 3813.5 Ohms,

    which gives a nominal regulated output voltage of 21.5 V, according to the equation:

    Vreg = 1.25*(1+R2/R1) + Iadj*R2

    Obtained from the LM317 datasheet, where Iadj = 100uA.

    The 28.4 V regulators use an R1 value of 240 Ohms and an R2 value of 5113 Ohms,

    which gives a nominal regulated output voltage of 28.4. N-channel STD95NH02L MOS-

    FET transistors are used as switches in this project to connect the battery to the panel

    and to the inverter. These MOSFETs are rated for up to 80 Amps, and a 22 V nominal

    gate-source voltage is used to turn them on. This gate-source voltage is supplied by the

    TLV2304 comparator. The actual output voltage of this comparator is its supply voltage

    (taken from the battery), plus or minus 0 .3 V, according to the datasheet, meaning that

    the gate-source voltage should be within 0.3 V of the battery voltage.

    controller.PNG controller.PNG

    Figure 4.4: Charge controller

    4.0.16 Selection criteria of cable

    We know that solar system is a limited capacity system. Appropriate cable should be

    used to reduce the loss of voltage and to make the system work with optimum efficiency.

  • Chapter 4. Design and analysis 36

    The cables used for wiring the d. c. section of a standalone PV system need to be

    selected to ensure that they can withstand the following :

    Environmental

    I Voltage and

    I Current conditions at which they may be expected to operate.

    I Effects of both current and solar gain.

    Load installation

    I For microscope: P = (2*20) = 40watt

    Where p is demand power and 2 is number of microscope. 20 the value of micro-

    scope

    Current design (Ib) =40/220V

    = 0.1818A

    I Choose the nominal current (In) for rating of protection from the table of EBCS

    In = 6, 10, 16, 20, 25, 32, 40.........

    In Ib

    For microscope In = 6A.

    I The cables current carrying capacity for microscope is:

    Iz = In/CF

    Where CF is correction factor 0.94 @ a temperature of 35c

    = 6/0.94 = 6.38A

    The cable size and rate from EBCS table current carrying capacity depending on

    Iz is 1mm2, 11A, cables are required

  • Chapter 4. Design and analysis 37

    I For refrigerator

    I the design current is

    Ib = p/v

    Ib = 90/220

    = 0.409A

    Figure 4.5: Feeder diagram

    4.0.17 Balance-of-System (BOS) Requirements

    I Fuses fuse holders, switches, and other components should be selected to sat-

    isfy both voltage and current requirements.

    I All battery series branches should contain fuses.

    I Fused disconnects are strongly recommended to isolate the battery bank from

    the rest of the system.

    I Surge protectors are strongly recommended to prevent surge voltage. Surge

    protectors help to protect your system from power surges that may occur if

    the PV system or nearby power lines are struck by lightning. A power surge

    is an increase in voltage significantly above the design voltage.

  • Chapter 4. Design and analysis 38

    I Automatic and manual safety disconnects protect the wiring and components

    from power surges and other equipment malfunctions. They also ensure the

    system can be safely shutdown and system components can be removed for

    maintenance and repair.

    I Array DC Disconnect The array DC disconnect, also called the PV discon-

    nect, is used to safely interrupt the flow of electricity from the PV array for

    maintenance or troubleshooting.

    I DC Disconnect Along with the inverter AC disconnect, the inverter DC dis-

    connect is used to safely disconnect the inverter from the rest of the system.

    I Battery DC Disconnect In a battery-based system, the battery DC discon-

    nects is used to safely disconnect the battery bank from the rest of the system.

    I Equipment Grounding Equipment grounding provides protection from shock

    caused by a ground fault. A ground fault occurs when a current-carrying

    conductor comes into contact with the frame or chassis of an appliance or

    electrical box. All system components and any exposed metal, including

    equipment boxes, receptacles, appliance frames and PV mounting equipment

    should be grounded.

    I Blocking diode- to prevent the reverse current.

    4.1 Result and discussion

    4.1.1 HOMER Optimization Results

    HOMER requires input information in order to analyze the system and to give

    the feasible solutions. The main input to the software is the load. After carefully

    determining the hourly community electric load from the primary load.

  • Chapter 4. Design and analysis 39

    Figure 4.6: primary load

    Table 4.9: Net present cost

    Comp Cap Repl OM Fuel Total

    PV 2,100 655 2,940 0 5,328

    battery 2,000 1,488 2,940 0 6,001

    Converter 195 81 1,023 0 1,284

    System 6,295 5,168 5,892,364 16,611 5,919,553

    Table 4.10: Anualized cost

    Comp Cap Repl OM Fuel Total

    PV 164 51 230 0 417

    battery 156 116 230 0 469

    Converter 15 6 80 0 100

    System 492 404 460,940 0 463047

  • Chapter 4. Design and analysis 40

    Figure 4.7: Cash flow diagram

    Figure 4.8: Monthly statistic

    Having fed the necessary input data given in the earlier section to the software

    the software is run. The resulting list of optimal combinations of realizable setups

    obtained is given in both overall and categorized forms. The above Table shows

    extracted part of the long list from the complete overall table. The extraction is

    based on the contribution made by renewable resources in the realizable set-ups.

    Rural villages in Ethiopia lack modern energy supply and this creates a challenge

    for sustainable development. The energy source of rural community which ac-

    counts more than 83 percent of the countrys population depends on unsustainable

    biomass supply. The use of biomass in traditional way has caused chronic health

    problems such as reparatory and eye diseases. For example the World Bank in

    2008 reported 1.6 to 2 million deaths each year is caused due to poor indoor air

    quality from fuel wood.

  • Chapter 4. Design and analysis 41

    Modern energy supply using PV in rural areas helps to meet millennium develop-

    ment goals (MDG) by transforming the quality and accessibility of schools, health

    center, communication centers and clean water supply and hence improve the so-

    cioeconomic status of the livelihood. Apart from socio economic development, PV

    based rural electrification, which is renewable energy source, can mitigate climate

    change by curbing CO2 emission. This helps us to understand the multidimen-

    sional advantages of rural electrification using PV in rural community. However,

    technology transfer always requires a detail study on the sustainability based on

    cost feasibility and level of technology for the specific literacy level. What makes

    this study special is that it uses an existing PV electrified rural village called BATA

    to study the impact of PV based rural electrification on socio-economic develop-

    ment, climate change and its sustainability on the study area. Different methods

    of attack have been used to study PV based rural electrification by different au-

    thors [Stutenbaumer et al 1999; Fara et al 1998; Kaufman et al 2000; A. Chaurey

    et al 2010; Nieuwenhout et al 2004; K. Muhopadhyay et al 1993]. Problems of

    existing energy systems are identified and new improved model is proposed for

    the village. However, there are several limitations of PV for rural electrification

    which threat the sustainability of PV based rural electrification projects. The high

    investment required is the main problem which limits its affordability by most of

    rural households of Ethiopia. The high technical skill required for installation and

    maintenance is also a problem for the PV project for rural electrification.

  • Chapter 5

    Conclusion and

    Recommendation

    5.0.2 Conclusion

    Regarding the solar energy it is definitively conclusive that there is abundant re-

    source. The feasibility study, which is based on the findings of the potential showed

    a list of possible feasible set-ups according to their Net Present Cost (NPC). The

    level of the renewable resource penetration can be said is closely tied with the net

    present cost. The choice as to which feasible system to pick from the list is linked

    to the choice of whether to consider the renewable resource or the net present

    cost. This decision is left to the policy makers of the country. However, as in the

    quotation given in the Introduction part Engineers shoed persistently press the

    policy makers to consider the utilization of the renewable resource.

    Solar power plants are currently the mere process which can be used in all the

    poor developing countries. So we think that if researchers continue to work hard

    to improve all the processes, in several years, solar energy will be the first renew-

    able energy source. Ethiopian is an example that off-grid PV is a highly attractive

    source of electricity for rural population in developing countries. Very short pay-

    back periods for small PV systems offer high financial savings which can be spent

    for other needs like education. A fast and successful dissemination strategy has to

    include local availability of PV systems, training of solar experts, local solar busi-

    nesses, exchange of information about end users needs and manufacturers, which

    might be achieved by local solar production, adapted appliances, financing schemes

    42

  • Chapter 1. Conclusion and Recommendation 43

    and model projects. Beneficial economics of PV in Ethiopia could generate addi-

    tional purchasing power and PV service jobs in rural regions. Access to electricity

    has the potential for sustainable rural development and a new enlightenment in

    rural areas. For our future, it is now essential to diversify our energy sources. If

    we do not react now and stop or decrease our dependency on fossil fuels the future

    is in danger. When oil and coal resources will be exhausted, there will probably

    have tensions between the countries, maybe war or economic crisis will increase.

    5.0.3 Recommendation

    I Curb the financing problem of PV projects availability of loan facility can be

    a solution. The involvement of microcredit institutions in the village such as

    Amhara credit and saving institution can solve the problem of loan availabil-

    ity.

    I Further study on the carbon saving and sequestration by PV electrification

    can be a source of income by carbon trading and will make such kind of

    projects more sustainable.

    I Technical capacities for installation and maintenance in village can be solved

    by training more villagers in the solar center.

    I Awareness about the technology was also seen a problem in the village and

    different awareness creation method such as billboards, leaflets and special

    trainings can increase the awareness.

  • Chapter 6

    Bibliography

    1 Raoufirad (1985), book of solar energy system, second edition

    2 K.M. Arkesteijn, A.E. Maaskant, Small is beautiful: Solar product and market

    development should be scaled to the actual needs of end-users in the developing

    world, Proceedings 22nd European Photovoltaic Solar Energy Conference, Milan,

    2007, June 3 7

    3 Frances Drake, Yakob Mulugetta (1996), Assessment of Solar and Wind Energy

    Resources in Ethiopia; Solar Energy, Vol. 57, No. 3; 1996.

    4 S.Firth, K. Lomas, A. Wright, R. Wall (2008), Identifying trends in the use of

    domestic appliances from household electricity consumption measurements, En-

    ergy and Building, vol. 40:2008.

    5 Dr. Winfried Hoffmann (18April 2006), PV solar Electricity: status and future.

    Photo Crystal Materials and devices III, 3April2006, Strasbourg, France.

    6 Solar Energy Foundation (SEF, 2009),Rural Electrification with Photovoltaic,

    Sun Connect, 1 November 2009, available on, www.stiftung-solarenergie.org, viewed

    on April 2010.

    7 Getachew Bekele (2009), study into the potential and feasibility of a standalone

    solar wind hybrid electric energy supply system for application in Ethiopia, Stock-

    holm, Sweden.

    8 Ch.Breyer, A.gerlach, M.hlusiak, C.Peters, P. Adelmann, J. Winiecki, H.Schtzechel,

    S.Tsegaye, W.Gashie (2009),Electrifying the Poor: Highly off grid PV system in

    Ethiopia- A basis for sustainable development, Avalibale on, http://www.arcfinance.org/pdfs/news/EthiopiaPaper2009.pdf,

    viewed on March, 2010.

    44

  • Chapter 1. Conclusion and Recommendation 45

    9 Stephan Lacey (2010), Why Investors like solar PV; available at, http://www.renewableenergyworld.com/rea/news/podcast/2010/08/why-

    investors-likesolar- pv, published August 5, 2010, viewed on September 21, 2010.

    10 United Nations, World Population Prospects: The2006 Revision Highlights, UN

    Department of Economic and Social Affairs, Population Division, Working Paper

    No. ESA/P/WP.202, New York, 2007, www.un.org/esa/population/publications/wpp2006

    WPP2006Highlightsrev.pdf

    11 MinistryofWaterandEnergyResourcesofEthiopia(2002), availableonlineathttp :

    //www.mowr.gov.et/index.php.pagenum.

    12 EthiopianRuralEnergyDevelopmentandPromotionCenter, (2007), SolarandWindEnergyUtilizationandProjectDevelopmentScenarios, Countrybackgroundinformation, finalReport,

    1 3D.Y.Goswami, F.Kreith, J.F.Kreider(1999), P rincipleofSolarEngineering, secondedition,BuchananCo., Philadela, PA.

    14 EuropeanPhotovoltaicIndustryAssociation(EPIA), SolarGenerationV 2008 :

    Solarelectricityforoveronebillionpeopleandtwomillionjobsby2020, EPIAandGreenpeace,Brussels, 2008, www.epia.org/publications/epiapublications.html.

    15 J.Merten,X.V allv, P.Malbranche, Sevenkeypointsforsuccessfulruralelectrificationprogrammeswithsolarenergy, Proceedings22ndEuropeanPhotovoltaicSolarEnergyConference,Milan, 2007, June37.

    16 H.Mller,B.Siepker,AwarenessTrainingF inancing : Thewaytoasustainabledisseminationofstand

    alonePV systemsforruralelectrification, Proceedings2ndWorldConferenceonPhotovoltaicSolarEnergyConversion, V ienna, 1998, July, 6

    10

    17 N.Argaw, TheroleofinstitutionsforsustainabledevelopmentofruralcommunitiesusingPV systems, Proceedings2ndWorldConferenceonPhotovoltaicSolarEnergyConversion, V ienna, 1998, July, 6

    10

    18 C.Breyer,A.Gerlach,M.Hlusiak, C.Peters, P.Adelmann, J.Winiecki,H.Schutzeichel, S.Tsegaye, andW.Gashie(2010), ElectrifyingthePoor :

    HighlyEconomicOffGridPV SystemsinEthiopia,ABasisforSustainableRuralDevelopment24thEuropeanPhotovoltaicSolarEnergyConference,Germany, pp.3852

    3860, 21 25September2009.

    19 CentralStatisticsAgency(2007), The2007PopulationandHousingCensusofEthiopia :

    StatisticalReportatCountryLevel, AddisAbaba,Ethiopia2007.

    20 D.Eskenazi,D.Kerner, andL.Slorninski, (1986), Evaluationofphotovoltaicproject, V olume

    II, TechnicalReport,MeridianCorporationFallschurch, V A22041.

    21 C.Breyer,A.Gerlach,M.Hlusiak, C.Peters, P.Adelmann, J.Winiecki,H.Schutzeichel, S.Tsegaye, andW.Gashie(2010), ElectrifyingthePoor :

    HighlyEconomicOffGridPV SystemsinEthiopia,ABasisforSustainableRuralDevelopment24thEuropeanPhotovoltaicSolarEnergyConference,Germany, pp.3852

    3860, 21 25September2009.

    22 TheinitiationofsolartradeinEthiopia(2005 2011)Dr.haraldschutzeichel. 23

    Www.Gaisma.com,BahirDar,EthiopiaSunrise, sunset, dawnanddusktimes, table, BahirDar,Ethiopia

    Sunrise, sunset, dawnanddusktimes, graph,BahirDar,EthiopiaSolarenergyandsurfacemeteorology,BahirDar,Ethiopia

    Sunpathdiagram.

    24 Exide6E95 11s, datasheet, providedbyBatteriesP lus.

    25 NchannelSTD95NH02LMOSFET, datasheet, providedbyFairchildSemiconductor.

  • Chapter 1. Conclusion and Recommendation 46

    26 TLV 2304IPdatasheet, TexasInstruments

    27 LM317datasheet, TexasInstruments.

    28 PhotovoltaicSystemSizingWorksheet, standalonePV sizing,

    29 BookofSocratesKaplans, designandintegrationofpossiblePV configurationtodeterminethemostcosteffectivesolarsystemforhousehold.

    30 AIMS3000WModifiedpureSineWaveInverter, providedbyshenzhen/HongKong.

    Declaration of AuthorshipAbstractAcknowledgementsList of TablesAbbreviations1 Introduction1.1 Background1.1.1 Photo voltaic system1.1.2 Rural Electrification in Ethiopia.1.1.3 Rural Electrification in Ethiopia using Solar PV.

    1.2 Problem of statement1.3 Objectives1.3.1 General objective1.3.2 Specific objective

    1.4 Expected outcome And Significant of the project1.5 Methodology1.5.1 Load demand1.5.2 Size the PV modules1.5.3 Battery sizing1.5.4 Inverter sizing1.5.5 Solar charge controller design

    2 Review of literature2.0.6 Off-grid pv system2.0.7 Off-grid pv system in Ethiopia2.0.8 Grid-connected system2.0.9 Grid-connected system in Ethiopia

    3 System description and over all operation4 Design and analysis4.0.10 Load4.0.11 Photo voltaic array sizing4.0.12 Panel inclination4.0.13 Battery sizing4.0.14 Inverter Selection4.0.15 Charge controller 4.0.16 Selection criteria of cable4.0.17 Balance-of-System (BOS) Requirements

    4.1 Result and discussion4.1.1 HOMER Optimization Results

    5 Conclusion and Recommendation5.0.2 Conclusion5.0.3 Recommendation

    6 Bibliography