CHAPTER ONE

INTRODUCTION

1.1              Background of Study

Solar energy is one of the most important energy sources that have been gaining increased attention in recent years. The amount of energy supplied to the earth in one day by the sun is sufficient to power the total energy needs of the earth for one year. Solar energy is clean and free of emissions, since it does not produce pollutants or by products harmful to nature. The conversion of solar energy into electrical energy has many applications fields.

Solar to electrical energy conversion can be done in two ways; solar thermal; and solar photovoltaic. Solar thermal is similar to conventional AC electricity generation by steam turbine excepting that instead of fossil fuel; heat extracted from concentration of solar ray is used to produce steam and a part is stored in thermally insulated tanks for using during intermittency of sunshine or night time. Solar photovoltaic use cells made of silicon of certain types of semi-conductor materials which convert the light energy absorbed from incident sunshine into DC electricity. To make up for intermittency and night time storage of the generated electricity into battery is needed.

1.2              Statement of Problem

One of the problems faced in solar power system is over charging of the batteries. This occurs if the system is not automatic and hence cannot switch off the charging unit when the battery is fully charged. A maximum power charge controller solves this by automatically switching off the charging circuit when the battery is fully charge.

1.3              Motivation

Solar energy is found abundantly and freely in nature. However, most of it is not fully harnessed. My interest in harnessing solar energy is the interest in power electronics and power system which was a significant motivation behind my decision to develop a solar charge controller.

1.4              Aims and Objective

The aims and objectives of this project is to construct a maximum power charge controller and a charge controller that will be able to limit the rate at which electric current is added to or drawn from electric batteries.

1.5              Project Limitation

Even though this project is construction of maximum power charge controller. However, it has some limitations. Firstly a charge controller can’t serve as the main source of electricity, it works with the help of the solar panel and received electricity and serve as a voltage regulator for your appliances. Also the inverter does not have a fly back converter circuit therefore the output from the inverter cannot be used to recharge the inverter.

1.6              Methodology

The resources used in this project was gotten from online research using the Internet, other projects written on or related to the topics, experiments and text books. From the resources collected the fig 1.1 below is a simple block diagram of a maximum power point charge controller followed by explanations of the basic blocks of the system.

                                    Figure 1.1 Block Diagram of the system

. A detailed block diagram of the system is shown in Figure: 1.1 which consists of following major components:

 a) Solar panel

b) Battery

c) Charge Controller

d) Maximum Power Point Tracker

e) DC-DC converter

A brief description of each of the system components is given below,

1.6.1    Solar Panel

A solar panel is a packaged connected assembly of photovoltaic cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. Solar panels use light energy photon from the sun to generate electricity through the photovoltaic effect. Electrical connections are made in series to achieve a desired output voltage and or in parallel to provide a desired current capability.

1.6.2    Battery

Electrical storage batteries are commonly used in PV system. The primary functions of a storage battery in a PV system are:

1) Energy Storage Capacity and Autonomy: to store electrical energy when it is produced by the PV array and to supply energy to electrical loads as needed or on demand.

2) Voltage and Current Stabilization: to supply power to electrical loads at stable voltages

and currents, by suppressing or smoothing out transients that may occur in PV system.

3) Supply Surge Currents: to supply surge or high peak operating currents to electrical loads or appliances.

1.6.3    Charge Controller

A charge controller or charge regulator limits the rate at which electric current is added to or drawn from electric batteries. It prevents overcharging and may prevent against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk. It may also prevent completely draining ("deep discharging") a battery, or perform controlled discharges, depending on the battery technology, to protect battery life.

In simple words, Solar Charge controller is a device, which controls the battery charging from solar cell and also controls the battery drain by load. The simple Solar Charge controller checks the battery whether it requires charging and if yes it checks the availability of solar power and starts charging the battery. Whenever controller found that the battery has reached the full charging voltage levels, it then stops the charging from solar cell. On the other hand, when it found no solar power available then it assumes that it is night time and switch on the load. It keeps on the load until the battery reached to its minimum voltage levels to prevent the battery dip-discharge. Simultaneously Charge controller also gives the indications like battery dipdischarge, load on, charging on etc.

1.6.4    Maximum Power Point Tracker

The maximum power point tracker (MPPT) is now prevalent in grid-tied PV power system and is becoming more popular in stand-alone systems. MPPT is a power electronic device interconnecting a PV power source and a load, maximizes the power output from a PV module or array with varying operating conditions, and therefore maximizes the system efficiency.

1.6.5    DC-DC Converter

DC-DC converters are power electronic circuits that convert a dc voltage to a different dc

voltage level, often providing a regulated output. The key ingredient of MPPT hardware is a switch-mode DC-DC converter. It is widely used in DC power supplies and DC motor drives for the purpose of converting unregulated DC input into a controlled DC output at a desired voltage level.

1.7              Project Layout

This project is written in Five Chapters; Chapter One which contains the Introduction, Statement of Problem, Motivation, Aims and Objectives, Methodology, Project Limitation. Chapter Two contains the Literature Review, Chapter Three details the Installation of the System, and Chapter Four provides Testing and Result, Chapter Five gives the Conclusion and some Recommendation.

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