May 16, 2012

How do Photovoltaic Work?

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Photovoltaic is the direct conversion of light into electricity at the atomic level. Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electrical current is resulted that may be used as electricity.

The photoelectric effect was first noted by a French physicist, Edmund Bequerel, in 1839, who discovered that certain materials would produce small amounts of electric current when exposed to light. In 1905, Albert Einstein described the character of light and the photoelectric effect on which photovoltaic technology is based, for which he later won a Nobel prize in physics. The first photovoltaic module was built by Bell Labs in 1954. It was promoted as a solar battery and was often simply a curiosity as it was too expensive to gain widespread use.

In the 1960s, the space industry started to make the first serious utilisation of the technology to provide power aboard spacecraft. Through the space programs, the technology advanced, its trustworthiness was established, and the cost began to decline. In the power crisis in the 1970s, photovoltaic technology gained recognition as a consistent source of power for non-space applications.

Solar cells are made from the same sorts of semiconductor materials, for example silicon, utilized in the microelectronics industry. For solar power cells, a thin semiconductor wafer is specifically treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar power cell, electrons are knocked loose from the atoms in the semiconductor material. If electric conductors are attached to the negative and positive sides, forming an electric circuit, the electrons can be caught in the form of an electric current — that is, electricity. This electricity can then be used to power a load, for example a light or a tool.

A number of photovoltaic cells electrically connected to one another and mounted in a support structure or frame is known as a photovoltaic module. Modules are engineered to supply electricity at a certain voltage, such as a typical 12 volts system. The existing produced is firmly dependent on how much light strikes the module.

Multiple modules can be wired together to form an array. In general, the larger area of a module or array, the more electricity it’s going to be produced. Photovoltaic modules and arrays produce direct-current ( dc ) electricity. They can be connected in both series and parallel electric arrangements to provide any needed voltage and current combo.

Today’s most common PV devices utilize a single junction, or interface, to create an electrical field within a semiconductor such as a PV cell. In a single-junction PV cell, only photons whose energy equals or greater than the band opening of the cell material can free an electron for an electrical circuit. In other words, the photovoltaic response of single-junction cells is limited to the piece of the suns range whose energy is above the band opening of the absorbing material, and lower-energy photons aren’t used.

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