Photovoltaics

From Wikipedia, the free encyclopedia

Nellis Solar Power Plant at Nellis Air Force Base in the USA. These panels track the sun in one axis.

Photovoltaic SUDI shade is an autonomous and mobile station in France that replenishes energy for electric vehicles using solar energy.

Solar panels on the International Space Station

Photovoltaics (PV) is a method of generating electrical power by converting solar radiationinto direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cellscontaining a photovoltaic material. Materials presently used for photovoltaics includemonocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, andcopper indium gallium selenide/sulfide. Due to the increased demand for renewable energysources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years.

Solar photovoltaics is a sustainable energy source.^[1] By the end of 2011, a total of 67.4 GW had been installed, sufficient to generate 85 TWh/year.^[2] And by end of 2012, the 100 GW installed capacity milestone was achieved.^[3] Solar photovoltaics is now, after hydro and wind power, the third most important renewable energy source in terms of globally installed capacity. More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building (either building-integrated photovoltaics or simply rooftop).

Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics has declined steadily since the first solar cells were manufactured,^[4] and the levelised cost of electricity (LCOE) from PV is competitive with conventional electricity sources in an expanding list of geographic regions. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries.^[5] With current technology, photovoltaics recoup the energy needed to manufacture them in 1 to 4 years.^[6]

Contents 1 Solar cells 2 Current developments 3 Economics 4 Applications 4.1 Power stations 4.2 In buildings 4.3 In transport 4.4 Standalone devices 4.5 Rural electrification 4.6 Solar roadways 4.7 Floatovoltaics 4.8 Plug in solar 5 Advantages 6 Disadvantages 7 See also 8 References

Solar cells[edit]

Solar cells produce electricity directly from sunlight

Average solar irradiance, watts per square metre. Note that this is for a horizontal surface, whereas solar panels are normally mounted at an angle and receive more energy per unit area. The small black dots show the area of solar panels needed to generate all of the world's energy using 8% efficient photovoltaics.

Solar cell productions by region^[7]

Main article: Solar cell

Photovoltaics are best known as a method for generating electric power by using solar cells to convert energy from the sun into a flow of electrons. The photovoltaic effect refers to photons of light exciting electrons into a higher state of energy, allowing them to act as charge carriers for an electric current. The photovoltaic effect was first observed byAlexandre-Edmond Becquerel in 1839.^[8][9] The term photovoltaic denotes the unbiased operating mode of a photodiode in which current through the device is entirely due to the transduced light energy. Virtually all photovoltaic devices are some type of photodiode.

Solar cells produce direct current electricity from sun light which can be used to power equipment or to recharge a battery. The first practical application of photovoltaics was to power orbiting satellites and other spacecraft, but today the majority of photovoltaic modulesare used for grid connected power generation. In this case an inverter is required to convert the DC to AC. There is a smaller market for off-grid power for remote dwellings, boats,recreational vehicles, electric cars, roadside emergency telephones, remote sensing, andcathodic protection of pipelines.

Photovoltaic power generation employs solar panels composed of a number of solar cellscontaining a photovoltaic material. Materials presently used for photovoltaics includemonocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, andcopper indium gallium selenide/sulfide.^[10] Copper solar cables connect modules (module cable), arrays (array cable), and sub-fields. Because of the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years.^[11][12][13]

Cells require protection from the environment 

Photovoltaics

From Wikipedia, the free encyclopedia

Nellis Solar Power Plant at Nellis Air Force Base in the USA. These panels track the sun in one axis.

Photovoltaic SUDI shade is an autonomous and mobile station in France that replenishes energy for electric vehicles using solar energy.

Solar panels on the International Space Station

Photovoltaics (PV) is a method of generating electrical power by converting solar radiationinto direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cellscontaining a photovoltaic material. Materials presently used for photovoltaics includemonocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, andcopper indium gallium selenide/sulfide. Due to the increased demand for renewable energysources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years.

Solar photovoltaics is a sustainable energy source.^[1] By the end of 2011, a total of 67.4 GW had been installed, sufficient to generate 85 TWh/year.^[2] And by end of 2012, the 100 GW installed capacity milestone was achieved.^[3] Solar photovoltaics is now, after hydro and wind power, the third most important renewable energy source in terms of globally installed capacity. More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building (either building-integrated photovoltaics or simply rooftop).

Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics has declined steadily since the first solar cells were manufactured,^[4] and the levelised cost of electricity (LCOE) from PV is competitive with conventional electricity sources in an expanding list of geographic regions. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries.^[5] With current technology, photovoltaics recoup the energy needed to manufacture them in 1 to 4 years.^[6]

Contents 1 Solar cells 2 Current developments 3 Economics 4 Applications 4.1 Power stations 4.2 In buildings 4.3 In transport 4.4 Standalone devices 4.5 Rural electrification 4.6 Solar roadways 4.7 Floatovoltaics 4.8 Plug in solar 5 Advantages 6 Disadvantages 7 See also 8 References

Solar cells[edit]

Solar cells produce electricity directly from sunlight

Average solar irradiance, watts per square metre. Note that this is for a horizontal surface, whereas solar panels are normally mounted at an angle and receive more energy per unit area. The small black dots show the area of solar panels needed to generate all of the world's energy using 8% efficient photovoltaics.

Solar cell productions by region^[7]

Main article: Solar cell

Photovoltaics are best known as a method for generating electric power by using solar cells to convert energy from the sun into a flow of electrons. The photovoltaic effect refers to photons of light exciting electrons into a higher state of energy, allowing them to act as charge carriers for an electric current. The photovoltaic effect was first observed byAlexandre-Edmond Becquerel in 1839.^[8][9] The term photovoltaic denotes the unbiased operating mode of a photodiode in which current through the device is entirely due to the transduced light energy. Virtually all photovoltaic devices are some type of photodiode.

Solar cells produce direct current electricity from sun light which can be used to power equipment or to recharge a battery. The first practical application of photovoltaics was to power orbiting satellites and other spacecraft, but today the majority of photovoltaic modulesare used for grid connected power generation. In this case an inverter is required to convert the DC to AC. There is a smaller market for off-grid power for remote dwellings, boats,recreational vehicles, electric cars, roadside emergency telephones, remote sensing, andcathodic protection of pipelines.

Photovoltaic power generation employs solar panels composed of a number of solar cellscontaining a photovoltaic material. Materials presently used for photovoltaics includemonocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, andcopper indium gallium selenide/sulfide.^[10] Copper solar cables connect modules (module cable), arrays (array cable), and sub-fields. Because of the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years.^[11][12][13]

Cells require protection from the environment 

sumber;

http://en.wikipedia.org/wiki/Photovoltaics

Transistor

From Wikipedia, the free encyclopedia

For other uses, see Transistor (disambiguation).

Assorted discrete transistors. Packages in order from top to bottom: TO-3, TO-126, TO-92, SOT-23.

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems. Following its development in the early 1950s, the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things.

Contents   [hide]  1 History 2 Importance 3 Simplified operation 3.1 Transistor as a switch 3.2 Transistor as an amplifier 4 Comparison with vacuum tubes 4.1 Advantages 4.2 Limitations 5 Types 5.1 Bipolar junction transistor (BJT) 5.2 Field-effect transistor (FET) 5.3 Usage of bipolar and field-effect transistors 5.4 Other transistor types 6 Part numbering standards / specifications 6.1 Japanese Industrial Standard (JIS) 6.2 European Electronic Component Manufacturers Association (EECA) 6.3 Joint Electron Devices Engineering Council (JEDEC) 6.4 Proprietary 6.5 Naming problems 7 Construction 7.1 Semiconductor material 7.2 Packaging 8 See also 9 Directory of external websites with datasheets 10 References 11 Further reading 12 External links

History[edit]

Main article: History of the transistor

A replica of the first working transistor.

The thermionic triode, a vacuum tube invented in 1907, propelled the electronics age forward, enabling amplified radio technology and long-distance telephony. The triode, however, was a fragile device that consumed a lot of power. Physicist Julius Edgar Lilienfeld filed a patent for a field-effect transistor (FET) in Canada in 1925, which was intended to be a solid-statereplacement for the triode.^[1][2] Lilienfeld also filed identical patents in the United States in 1926^[3] and 1928.^[4][5] However, Lilienfeld did not publish any research articles about his devices nor did his patents cite any specific examples of a working prototype. Because the production of high-quality semiconductor materials was still decades away, Lilienfeld's solid-state amplifier ideas would not have found practical use in the 1920s and 1930s, even if such a device had been built.^[6] In 1934, German inventor Oskar Heil patented a similar device.^[7]

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948.

From November 17, 1947 to December 23, 1947,John Bardeen and Walter Brattain at AT&T's Bell Labs in the United States, performed experiments and observed that when two gold point contacts were applied to a crystal ofgermanium, a signal was produced with the output power greater than the input.^[8] Solid State Physics Group leader William Shockley saw the potential in this, and over the next few months worked to greatly expand the knowledge of semiconductors. The term transistorwas coined by John R. Pierce as a portmanteau of the term "transfer resistor".^[9][10]According to Lillian Hoddeson and Vicki Daitch, authors of a biography of John Bardeen, Shockley had proposed that Bell Labs' first patent for a transistor should be based on the field-effect and that he be named as the inventor. Having unearthed Lilienfeld’s patents that went into obscurity years earlier, lawyers at Bell Labs advised against Shockley's proposal because the idea of a field-effect transistor that used an electric field as a "grid" was not new. Instead, what Bardeen, Brattain, and Shockley invented in 1947 was the first point-contact transistor.^[6] In acknowledgement of this accomplishment, Shockley, Bardeen, and Brattain were jointly awarded the 1956 Nobel Prize in Physics "for their researches on semiconductors and their discovery of the transistor effect."^[11]

In 1948, the point-contact transistor was independently invented by German physicists Herbert Mataré and Heinrich Welker while working at the Compagnie des Freins et Signaux, a Westinghouse subsidiary located in Paris. Mataré had previous experience in developing crystal rectifiers from silicon and germanium in the German radar effort during World War II. Using this knowledge, he began researching the phenomenon of "interference" in 1947. By witnessing currents flowing through point-contacts, similar to what Bardeen and Brattain had accomplished earlier in December 1947, Mataré by June 1948, was able to produce consistent results by using samples of germanium produced by Welker. Realizing that Bell Labs' scientists had already invented the transistor before them, the company rushed to get its "transistron" into production for amplified use in France's telephone network.^[12]

Philco surface-barrier transistor developed and produced in 1953

The first high-frequency transistor was the surface-barrier germanium transistor developed by Philco in 1953, capable of operating up to 60 MHz.^[13] These were made by etching depressions into an N-type germanium base from both sides with jets of indium sulfate until it was a few ten-thousandths of an inch thick. Indium electroplated into the depressions formed the collector and emitter.^[14][15] The first all-transistor car radio that was produced in 1955 by Chrysler and Philco, used these transistors in its circuitry and also they were the first suitable for high-speed computers.^{[16][17][18][19]}

The first working silicon transistor was developed at Bell Labs on January 26, 1954 by Morris Tanenbaum.^[20] The first commercial silicon transistor was produced by Texas Instrumentsin 1954.^[21] This was the work of Gordon Teal, an expert in growing crystals of high purity, who had previously worked at Bell Labs.^[22] The first MOS transistor actually built was by Kahng and Atalla at Bell Labs in 1960.^[23]

In March 2013 American researchers at Stanford University announced they had built a transistor out of DNA and RNA molecules.^[24]

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