Photovoltaic (PV) materials convert sunlight and convert it into electricity. PV technology was developed at Bell Labs in the 1950's and it's primary application was powering satellites in space.
Photovoltaic us the sun's energy to produce electricity and do not produce any of the harmful toxic emissions that fossil fuels produce. Sunlight is a widespread energy source, and the amount of energy that reaches the earth is greater then we need. PV can get energy from the sun anywhere in the world, even under cold conditions.
Edmund Becquerel first noted the PV effect in 1839, when he recorded the appearance of a voltage when lighting two identical electrodes in a weak conducting solution. The first PV cells were made out of crystalline silicon by Bell Labs in 1954.
The photovoltaic cell is the basic part of PV technology. It produces direct current (DC) electricity like a battery. Groups of cells are joined together to make a module and modules are joined to form an array. These cells can provide energy ranging from a few milliwatts (mW), like in a calculator, to several megawatts (MW), the size of a large power plant.
The most common semi-conducting material used for PV cells is single crystal silicon. These are the most efficient type of PV cells and can convert up to 25% of solar energy directly into electricity. They are very durable and have long life, as proved in their many space related applications.
Silicon cells however are expensive and slow to produce. So, reachers have been hard at work trying to develop alternatives to silicon cells. These include poly-crystalline silicon cells, concentrating collectors, and "thin film" cells. Poly-crystalline silicon cells are less expensive to make then silicon cells, however they are less efficient (15-17%). Collectors concentrate light from a large area onto a small PV cell using lenses and reflectors. These can only be used, however, in areas with very little cloud cover, and in these areas efficiencies of up to 35% have been reached. "Thin films" (0.001-0.002mm thick) of uncrystallized silicon are inexpensive and can be easily put on materials like glass and metals.
Photovoltaic power has applications in three main fields. Consumers products, remote power, and utility generation.
Consumer productes unlcude solar powered claculators and solor watches. These use "thin film" silicon. Research using these methods include battery chargers and solar powered walkway lights.
Remote power applications is the major market for photovoltaic power. For remote locations, such as communities and cottages in North America, not on regular electric grids, PV cells in conjunction with batteries are the least expensive way pf providing electricity. This can also include tele-communications, water pumping, and navigational power supplies.
Last, we have the use of suplying energy to electirc transmission grids. This is done in two ways; through arrays of PV modules in a central location working like a regular power plant, or by arrays of PVs on the roofs of houses and buildings.
Photovoltaics produce a far smaller impact on the enviroment then regular methods of energy generation. It uses no fuel other then the sun, it requires no water cooling, it gives off no air or water pollutants and represents no radioactive threat.
The only real negative environmental impact are they potentially toxic chemicals used to manufacture the cells. These chemicals are made in a facility where proper disposal of any toxic wastes should bring down the risk of any contamination. A cells useful life is generally around 30 years. Most of the toxic materials in these cells can be recyled and should not bring any disposal problems.
Photvoltaics is a very healthy alteritive for generating electricity. PV cells are cost effective, and reliable. Research on bringing the cost of manufacting down even more and how much the world wants to get rid of the negitive enviromental problems that come with other forms of energy, will determine the future of photovoltaics.
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