EnGen Roadshow Demo: Solar Photovoltaics

How It Works

We have a number of solar panels that we demonstrate. The largest is a 3x5 feet 180 Watt panel. It costs $500. Solar panels directly convert sunlight to electricity. Standard solar cells are thin sandwiches of two semiconductors which are made of highly purified silicon.

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These layers make up a large-area p-n junction diode. When a solar cell is exposed to sunlight, photons are incident on the surface, which generates energy. This generated energy allows electrons to be knocked out of their orbits and released. Electric fields in the solar cells pull these free electrons in a directional current. Metal contacts in the solar cell generate electricity from the current. The conversion of sunlight to usable electrical energy is called the Photovoltaic Effect. The current that is produced from solar panels is direct current (DC), similar to that of batteries.

How It Is Used Today

Solar panels are installed on buildings and structures to produce electricity. The electricity they produce is commonly inverted to alternating current (AC) and then fed back into the electrical grid. The utility will buy/trade this electricity from the customer. In 2010, nearly 16 GW of solar PV installations were completed. This is over a 100% growth from 2009.

History

The French physicist A. E. Becquerel was the first to recognize the photovoltaic effect in 1839. Some 44 years later the first photovoltaic cell was built by Charles Fritts. This first cell had an efficiency of 1% and was made of selenium and gold. In 1946 the modern junction semiconductor solar cell was patented by Russel Ohl. Bell Laboratories began to develop the modern cell in 1954 using a diffused silicon p-n junction. The cost was about $250 per Watt, which was prohibitive for use on earth. However, satellites began to use solar panels to produce their power in 1958. Continuing research has led to improvements which has dropped the price per Watt to $1.09 in 2011.

Projects You Can Do At Home

$30 solar house kit
$38 solar car

Additional Information

About.com: inventors.about.com/library/inventors/blsolar3.htm
Wikipedia: en.wikipedia.org/wiki/Solar_cell