In the world today, we are being challenged with the lag of energy that used to generate the electrical power, as the solution the exploration and development of alternative power become a global issue. Some of the alternative power such as solar energy produces the direct current (DC) from the solar panel. Most of the electrical appliances today used the alternating current (AC) as the source. The conversion of energy from DC source to AC source becomes the serious matter. Inverter is the electrical device that has used to convert the DC source to AC source that allow the electrical appliances to run safely, however the power quality issue cannot be separate from inverter, this is because in the market now there are several type of inverter. The type of inverter is classified by the output waveform. The improvement of output wave form to produce the better source and fewer harmonics should be taken as serious matter to avoid the corruption and damage to the electrical device especially for house appliances. This project focuses mainly on designing and constructing a charging system which uses the Sun as the primary source of energy.
Keywords : Battery, Charge Controller, Electricity generation, Inverter, Solar panel.
Renewable energy refers to energy from a source that is continuously replenished by natural processes. The Earth as a resource system has a limited capacity for supporting a growing human population with an intensive exchange of materials and energy with its environment, hence the need for a growing awareness to achieve a more sustainable societal use of materials. The earth receives energy directly from the sun. It is silent, inexhaustible, and non-polluting. The power reaching the earth from the sun is typically about 1000W/m2. The total amount of energy that the earth receives daily is 1353W/m2. About four million tons of the sun's matter is changed into energy every second. The sun is the most readily and widely available renewable energy source capable of meeting the energy needs of whole world. It can provide more power than any fossil fuel on the planet. Solar panels are made up of solar cells which are an array of photovoltaic cells (PV). Any type of equipment used to convert sunlight into energy is considered solar cell or panels. In view of this, we designed a charging system using solar energy innovation that will require low maintenance cost. The basic method for using solar energy is to provide a system that can collect and store energy, the collector (photo voltaic cells) is able to convert the solar radiation into electrical energy which can then be stored as chemical energy in rechargeable batteries. Storage of this energy is necessary for times when the Sun is not shinning and can also be delivered to the electrical power's transmission systems. Photovoltaic is the direct conversion of light into electricity at an atomic level. Some materials exhibit a properly known as the photoelectric effect that cause photons and release electrons. When these electrons are captured, or electric
current that can be used to power a load.
Figure 1: Schematic diagram of a charging system using solar innovation
Solar energy is free and inexhaustible. Solar energy is the use of natural light to provide illumination. It is the technology of obtaining using energy from the light of the sun using semi-conductor materials and this is energy efficient lightening technology. Solar panels are devise that generate power from the sun by converting sunlight into electricity with no moving parts, zero emission and no maintenance that much. They are used in residential, commercial, institutional and light industrial applications.
It is a circuit for converting direct current DC to alternating current AC. In a simple inverter circuit, DC power is connected to a transformer through the center tap of the primary winding. A switch is rapidly switched back and forth to allow current to flow back to DC source following two alternate paths through one end of the primary winding and then the other. The alternation of the direction of current in the primary winding of the transformer produces alternating current AC in the secondary circuit. Early AC to DC converters combined a synchronous AC motor with a commutator so that the commutator reverses its connections to the AC line exactly twice per cycle. This results in AC-in, DC-out. Inverting the connections to a converter results in DC-in and AC-out. Hence an inverter is an inverted converter.
Types of Inverters
- Square Wave Inverter: It has a very high harmonic component and a peak to Root Mean Square (RMS) voltage ratio of 1. Square wave inverter is unsuitable for general use because electronic loads are usually sensitive to peak voltage while resistive loads responds to RMS value and it results in uneven power delivery that is not efficient for running most devices.
- Modified Sine Wave Inverter: It approximates a sine wave and have low enough harmonics that do not cause problem with household.
- Pure Sine Wave Inverter: It produces a nearly perfect sine wave output with less than 3% total harmonic distortion. The waveform produced by these inverters is same as or battery than the power delivered by the utility
- Resonant Inverter: It produces sine waves with LC circuits to remove harmonics from a simple square wave. Typically, there are several series and parallel resonant circuits, each tuned to a different harmonic of the power line frequency this simplifies the electronics but the inductors and capacitors tend to be large and heavy. Its high efficiency makes this approach popular in large uninterruptible power supplies in data centers that run the inverter continuously in an online mode to avoid any switch over transient when power is lost.
- Multilevel Inverter: It synthesizes a desired voltage from several levels of direct current voltage as inputs. The advantage of using multilevel topology includes reduction of ratings of power devices and reduced cost. There are three topologies which are diode clamped inverter, flying capacitor inverter and cascaded inverter.
1.2 CHARGE CONTROLLER
A charge controller prevents overcharging and protect against overvoltage which can reduce the battery performance, life span and may pose a safety risk. The main function a solar charge controller is to charge the batteries, and also prevents the solar panels form overcharging the batteries. Charge regulator electronics is the most sensitive and crucial to assuring stable photovoltaic system operation. Charge regulator malfunctioning result in high maintenance cost including battery replacement. If high current are required, two or more charge controllers can be used.
Types of Charge Controller
- Shunt controllers: These are designed for small system. They prevent overcharging by short circuiting PV array when battery is fully charged. It monitors the battery voltage and switches PV current through transistor when pre-set full charge value is reached. Shunt controllers have limited load handling capability and ventilation requirement.
- Single-stage series controller: This prevents overcharging of battery by switching the panel off when the battery voltage reaches a preset value; Charge Termination Set point (CTSP).
- Diversion controllers: This automatically regulates the charge current depending on the battery's state of charge diverting excess charging current to resistive load. The full array current is allowed to flow when battery is at a low state of charge. As the battery voltage approaches full charge, the controller and the load resistor dissipates some of the array power so that less current flows into the batteries.
- Pulse width modulation (PWM) controllers: They provide a tapering charge by rapidly switching the full charging current on and off when the battery reaches a fully charged state (the preset charge termination set point). The length of the charging current pulse gradually decreases as battery voltage rises reducing the average current into the battery.