Photovoltaic Technology

          CHAPTER I

INTRODUCTION

1. Project Overview

Photovoltaic is a technology that generates a direct current voltage and producing power in watt (W).  The power is come from the semiconductor material when it illuminated by photons.  In general, the photons are come from the light.  As long the light is shinning, the power from the semiconductor will be generated.  When the light is stop shinning, the electricity from the semiconductor will be stop produced by the semiconductor device.  The recent technology semiconductor material to produce electricity is solar array module.

Enhanced interest in solar energy utilization is prompted after the world energy crisis associated with the 1973 Middle East war.  This interest was further fueled by world apprehensions concerned with nuclear wastes, nuclear safety handling, green house gases and global warming issues [1].  These considerations make solar energy the ultimate strategic choice as a source of world energy [2].

As a result of current day satellite technology, designers now have a more or less clear picture about solar energy intensity distribution world wide [3].  Solar energy research emphases over the past three decades were concentrated on two main aspects of the solar energy technology.  The first is concerned with solar energy direct heat production.  The second is involved with solar energy electricity production.  Encouraging results have been obtained.  However, and after thirty years, conversion efficiencies of about 20 % are not up to the initial expectations on one hand and below economic considerations to make the solar power technology is an economically competitive source compared with energy sources on the other hand.

To make the solar power technology is the first priority electricity source choose by the consumer, all researches now are consider to concentrate to store the energy generated by the solar system by using a batteries bank or using capacitors bank [2].  Result from extensive researches in storage technology so far; fall short from producing a new generation practical a storage method using battery which is better which is based on (charge/Weight)x cost.  The good electrical storage batteries are using lead acid battery or the nickel-cadmium battery.

Working on the consumption of a particular solar cell with some fixed conversion efficiency, concerning on the optimum condition for extracting the maximum amount of electric charge from the solar panel that can be stored in the battery is very important.

Therefore, the purpose of this project is to develop a relatively simple electronic solar charge control circuit that can automatically distribute the electric current produced by a photovoltaic solar panel in an optimum condition to extract the maximum charging current as stable as possible depending on the light intensity.

1. Problem Statement

Energy from the solar system can be stored in the electric energy storage like a battery by using transferring the charge from the solar module to electrical storage.  The problem that always faced in designing the battery charger circuit is to know when to determine the full charge voltage point and to produce the battery charger circuit which is secure during charging process.

        Once the battery is fully charged, the exceeded charging current has to be dissipated somehow.  The dissipated current will generate heat and gasses which causes lacks on battery performance.  The essence of good charging is to be able to detect when the reconstitution of the active chemicals is completed and stop the charging process before any damage occur.  At the same times to maintain the cell temperature within its safe limits.  In order to detect the cut off point which is normally called float voltage setting is the simplest way to overcome the problem in maintaining the cell temperature in the battery.  The battery temperature and switching time are the extremely need to be considered in order preserving the battery life.

If over charging condition is occur on the battery which is normally comes from error in determining the cut off point or from rising in temperature around the battery or in the cell itself, the temperature signal or resettable fuse can be used to turn off or disconnect the charger when danger sign appear to avoid damaging the battery.

1. Objective of Project

The main objectives of the project are;

1. To design SCC circuit using Pulse Width Modulation (PWM) technique as a controlled pulse charger method.
2. To design SCC circuit using fast switching devices to overcome overcharging problem on the rechargeable battery.
3. To simulate the SCC circuit.
4. To develop and construct practical SCC circuit which has 12 volts, 0.5 amps input and output from the battery after fully charge is 12 volts, 7.2 amps hour.

1. Scope of Project

The primary aim of the project is design and develops a SCC circuit for solar power system.  The scopes of the project are;