From Wikipedia, the free encyclopedia
A solar cell or photovoltaic cell is a device that converts light energy into electrical energy by the photovoltaic effect. Photovoltaics is the field of technology and research related to the application of solar cells as solar energy. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the source is unspecified.
A solar cell fulfils only two functions: photogeneration of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity (simply put, carrying electrons off through a metal contact into a wire or other circuit).
Solar cells have many applications. Individual cells are used for powering small devices such as electronic calculators. Assemblies of cells are used to make solar modules, which may in turn by linked in photovoltaic arrays. These generate a form of renewable energy, particularly useful in situations where electrical power from the grid is unavailable such as in remote area power systems, Earth-orbiting satellites and space probes, remote radiotelephones and water pumping applications. Photovoltaic electricity is also increasingly deployed in grid-tiedelectrical systems.
Applications and implementations
Polycrystaline PV cells laminated to backing material in a PV module
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Solar cells are often electrically connected and encapsulated as a module. PV modules often have a sheet of glass on the front (sun up) side , allowing light to pass while protecting the semiconductor wafers from the elements (rain, hail, etc.). Solar cells are also usually connected in series in modules, creating an additive voltage. Connecting cells in parallel will yield a higher current. Modules are then interconnected, in series or parallel, or both, to create an array with the desired peak DC voltage and current.
The power output of a solar array is measured in watts or kilowatts. In order to calculate the typical energy needs of the application, a measurement in watt-hours, kilowatt-hours or kilowatt-hours per day is often used. A rule of thumb commonly used is that peak power times 20% gives average power, equating to one kW peak producing 4.8 kW·h per day.
