The sun provides the energy to sustain life in our solar system. In one year, the earth receives enough energy from the sun to meet its energy needs for nearly a year. Photovoltaic is the direct conversion of sunlight to electricity, it is a beautiful alternative source of energy to conventional sources of electricity for many reasons it is safe, silent, non – polluting, renewable, highly modular in that their capacity can be increased incrementally to match with gradual load growth, it is reliable with minimal failure rates and projected service lifetimes of about 20 to 30 years. It requires no special training to operate, it contains no moving parts, it is extremely reliable and it’s virtually maintenance free, and can be installed almost anywhere.
A photovoltaic system is a complete set of interconnected components for converting sunlight into electricity by photovoltaic process including array, balance of system and load. The intensity of sunlight that reaches the earth varies with time of the day, season, location and the weather condition, the total energy on a daily or annual basis is called Irradiation and indicates the straight of sunshine. Irradiation is expressed in Whm – 2 per day or KWh.m-2 per day. Different geographical regions experience different weather patterns, so the site we live is a major factor that affects the photovoltaic system design, the orientation of the panels, finding the number of days of autonomy where the sun does not shine in the sky and choosing the best tilt angle of the solar panels.
Photovoltaic panels collect more energy, if they are installed on a tracker that follows the movement of the sun although it is an expensive process; for this process they are usually fixed in a particular position with an angle called the tilt angle B. This angle varies according to seasonal variation, for instance, in summer the solar panel must be more horizontal while in the winter, it is placed at a steeper angle.
In this project, the various components of a photovoltaic system and factors affecting its design for the purpose of domestic use is explained. Then a residence model with medium energy requirements in one of the offices in Pure and Applied Physics Department, Ladoke Akintola University of Technology, Ogbomoso is taken as a study case. The design procedures of the photovoltaic system will be provided in ascending manner.
1.1 SYSTEM DESCRIPTION
Photovoltaic system is considered of a variety of equipment in addition to the photovoltaic array, a balance of system that wired together to form the entire fully functional system capable of supplying electric power and these components are:
- Photovoltaic Cells: Represent the fundamental power conversion units, they are made from semi – conductor materials and convert sunlight energy to electricity. Individual photovoltaic cells are usually quite small, producing around 1 to 2 watt of power. To increase the power output of a photovoltaic cells, they have to be connected together to form modules, modules are connected in parallel and series to form larger parts/units called Panels and Arrays to produce electric power that meets any electric need.
- A storage Medium: Battery bank which is involved in the system to make the energy available at night or at days of autonomy (sometimes called dark days) when the sun is not providing enough radiation the standard batteries that are used in solar system are lead – acid batteries because of their high performance; long life and cost effectiveness.
- A Voltage Regulator or Charge Controller: Is an essential part of nearly all power system that change batteries, the basic function of a controller is to block reverse current and prevent battery from getting overcharged. Some controllers also prevent battery over discharging, electrical overload, display battery status and the flow of power.
- An Inverter: Is device that changes a low d.c voltage to usable a.c voltage. It is one of the solar energy. Systems main element is the solar panel generate d.c voltage. Inverters are different by the output wave format, output power and installation type. It is also called power conditioner because it changes the form of the electric power. There are two types of output wave format: Modified Sine wave (MSW) and Pure Sine wave (PSW). The MSW inverters are economical and efficient, while the pure sine wave inverters are now sophisticated with high end performance and can operate virtually any type of load. There are two types of inverters that can be installed, the stand alone installation and grid connection installation.