History of PV
The first solar cell was created in 1883. It was inefficient by today's standards, turning only one to two percent of sunlight into electricity. The breakthrough in solar cell technology came in 1954 when researchers at Bell Laboratories stumbled across the photovoltaic properties of silicon while experimenting with new transistor technologies. Three years later, PV research began in earnest to develop an independent solar energy source for space technologies. Thanks to continuing research, modern commercial PV cells have improved to 11-15% efficiency.
Historically PVs have been used extensively in areas that are not served by a power grid. As PV prices have dropped and grid energy has become more expensive, PV systems are increasingly used in grid-tied applications.
PV Technology
PV technology uses the electrical properties of materials known as semiconductors to produce electricity. When hit by sunlight, a semiconductor material creates an electrical charge which can then be transferred through a circuit to anything that uses electricity.
In a PV system, these semiconductors are produced in the form of cells, which are then assembled in a structural panel. There are many different types of panels available, and each has its particular advantages. Depending on the amount of electricity needed, these panels can then be connected in an array of any size to provide the electricity needed for a home, office, or larger facility.
A PV cell consists of two thin layers of semi-conducting silicon. Each layer is "doped" or infused with a small amount of another material that prevents all the electrons from being locked in the pure silicon lattice structure.
One layer is doped (usually with phosphorus) so that it has slightly too many electrons, and the other layer is doped (usually with boron) so that it has slightly too few electrons. This difference produces a small electric field between the two layers, which gives the electrons a direction to flow when they get knocked out of place by a photon (packet of light energy).
Solar cells are usually small and only produce a couple of watts of power. To produce usable energy, many cells are strung together to make a module. Multiple modules are connected into an array, which gets connected to a load (like a light bulb). Through the wiring the electrons have a chance to flow through the whole loop back to the layer that lost its electrons in the first place.
The electric current, as this flow is called, has done some work (making light and heat in the light bulb).
Future of PV
The solar energy that hits the earth each day is the only fuel required for a PV system. Because PV uses this natural energy source, it does not require the burning of fossil fuels, which creates myriad environmental problems. Because the sun's energy will never run out, PV is also considered a renewable energy technology.
PV cells and panels can be manufactured and installed at almost any scale. As a result, they are used to power a broad variety of things. At its smallest, PV can power calculators, laptop computers, and other appliances. At its largest, it can power homes, offices, and other buildings that use large amounts of electricity. It can also be connected from these buildings to provide power to the electric grid, increasing the diversity of our collective electricity sources.