Solar technology is in the market for more than 50 years, but it is still an innovative technology providing cheap, efficient and green electricity to homes, businesses and industries. Large solar energy systems are capable of providing electrical power to remote areas. Therefore, this renewable energy technology is still progressing to meet the power demands.
What is PV Technology?
Photovoltaic cells, also known as solar cells, convert energy of the sun into electricity. Photovoltaic is a combination of two words, i.e. photo that means light and volt relates to electricity. PV cells combine with electrical configuration to form modules and arrays for providing power to electrical loads, operate motors and charge batteries. A photovoltaic system can produce AC power for appliances with an appropriate power conversion equipment. It can also interconnect or operate in parallel with a utility grid.
Symbol of Photovoltaic Cell
Operation of a Photovoltaic Cell
A photovoltaic or solar cell is a thin semiconductor wafer, typically silicon, composed of an electric field formed with doped P-type (positive) and N-type (negative) material. The two materials contact to form a PN junction. When the sunrays strikes the PV cell, electrons gain momentum and result in current flow when the PV cell forms an electrical circuit with the electrical load, such as a tool or light. The output power or current of a solar cell is directly proportional to the sunlight intensity striking the cell surface, and depends on the efficiency and surface area of a solar cell.
Operation of a Typical PV or Solar Cell
Solar Cells, Modules and Arrays
Photovoltaic cells connect in an electrical configuration to produce high power levels and currents. Solar cells connected together electrically and sealed in a support frame or structure are termed as a photovoltaic module. Similarly, multiple modules assemble to form a photovoltaic array. Arrays and modules are connected in series or parallel combination to produce desired current ad voltage.
PV Cell, Module and Array
Advantages of Solar or PV Cells
Compared to the conventional technologies of power generation, solar or PV cells provide many advantages. The costs of producing electricity will reduce largely because sunlight is a free resource and it requires only initial installation costs of a PV system. A solar system is capable of providing power to remote areas by interconnecting with utility grids. If the PV system is producing surplus electricity, it is possible to send it to the utility grid without wasting it. Most importantly, the use of green renewable energy for producing electricity will eliminate the harmful pollutants and carbon dioxide from the environment.
Working of a PV System
A solar or photovoltaic system is a combination of many components and circuits used to generate electrical power. Compared to conventional power generation system, the equipment used for a PV system is different. However, it operates on the same electrical principles and standards.
Typically, when a photovoltaic module exposes to sunlight, it generates electricity. However, a PV system requires many other components to control, conduct, convert, store and distribute the electrical energy generated by the PV array. Some of the major components that are specifically required for producing electricity using solar panels include an electrical power inverter, battery, controller, supplementary energy sources and electrical loads or appliances. These components may vary depending on the operational and functional requirements of the PV system. Furthermore, there are other hardware components referred as the balance of system (BOS) that include surge protection and overcurrent devices, wiring and equipment for power processing. A typical PV system with its components is shown in the figure below:
A PV System with its Components
PV systems often use batteries to store electrical energy generated by the array and utilize that stored energy when required to drive electrical loads. Such situations may occur when the weather is cloudy or at night when sunlight is not available. A system also use batteries to obtain maximum power point of an array for supplying stable voltages to electrical loads. Such systems use battery controller for protecting battery from over charging or discharging.
PV System Performance Parameters
The maximum power produced by a PV array or module measured in peak watt rating determines its performance. Certain factors and conditions determine the performance of a PV array including power output calculation, design and assembly degradation, electrical performance characterization, operating temperatures, and environmental conditions.
The parameters that define the performance criteria include power output, energy output and conversion efficiency. Output power is the average power or peak power produced by the PV array and measured in watts. Output energy is the generated amount of energy in specific time and measured in watt-hour. The ratio of output energy from the array to input energy from the sun determines the conversion efficiency.