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I.                    Definition 

Photovoltaics, or PV for short, is a technology that converts light directly into electricity. It is best known as a method for generating solar power by using solar cells packaged in photovoltaic modules.     

II.        PV system 

A photovoltaic system consists of 4 main components: _ Photovoltaic modules/solar panels which are packaged solar cells: Solar cells are made primarily of silicon, a semiconductor. When sunlight strikes the solar cells, or photovoltaic modules, a relatively high percentage of sun’s rays is absorbed into the silicon material. This energy activates and loosens electrons, allowing them to flow freely. Incorporated into the solar cells are electrodes, a networked grid that forces the freed electrons to flow in the designated direction, creating an electrical current. _The inverter: changes the Direct Current (DC) received from the modules into Alternating Current (AC) to power TVs, appliances and other household equipment. _Solar power monitor: displays immediate and cumulative readouts on electricity generation, power consumption and C02 reduction level. _Electric meter: The solar electric system connects to the utility grid thru a standard breaker. The utility meter tracks the net power usage and spins backward when you create more electricity than you use. 

III.               PV applications 

PV has worldwide applications. The first practical application of PV was to power orbiting satellites and other spacecraft and pocket calculators, but today the majority of PV modules are used for grid connected power generation. As electricity is always one of the most necessary energy in daily life as well as industry, PV has been applied in various fields of life and has proved high efficiency. 

PV in buildings

PV solar panels on a house’s roof Building-integrated photovoltaics (BIPV) are increasingly incorporated into new domestic and industrial buildings as a principal or ancillary source of electrical power, and are one of the fastest growing segments of the PV industry. Typically, an array is incorporated into the roofs or walls of a building. Alternatively, an array can be located separately from the building but connected by cable to supply power for the building. Where a building is at a considerable distance from the public electricity supply (or grid) – in remote or mountainous areas – PV may be the preferred possibility for generating electricity, or PV maybe used together with wind, diesel generators and/or hydroelectric power. 

PV in transport

PV on the International Space Station  Nuna 3 PV powered car PV is being used increasingly to provide auxiliary power in boats and cars. Recent advances in solar cell technology have shown the cell’s ability to administer significant hydrogen production, making it one of the top prospects for alternative energy for automobiles. 3.      PV in standalone devices  Solar powered parking meter PV has been used for many years to power calculators and novelty devices. Solar power remote fixed devices have seen increasing use recently, due to increasing cost of labour for connection of mains electricity or a regular maintenance programme. In particular, some common uses are parking meters, emergency telephones and temporary traffic signs. à Nowadays, electricity generated using PV method is still more expensive than usual electricity; therefore it has not become popular in household life. However, in the situation that the Earth’s environment is getting worse and worse, human has to thoroughly control any kind of pollutions; a pollution-free power like solar power will soon find its position in daily life as well as industry.        

IV.     Bibliography:
 http://en.wikipedia.org/wiki/Photovoltaics_in_transport http://en.wikipedia.org/wiki/Photovoltaic_system http://en.wikipedia.org/wiki/Photovoltaics#Applications_of_PV http://solar.sharpusa.com/files/popup3d.asp?title=Solar&file=/files/solar.swf&type=1&height=500&width=700