How solar cells work

An artist's rendering of the completed International Space Station shows its full complement of solar panels

(CNN) -- Photovoltaic (PV) cells like those on the International Space Station's solar panels convert light from the sun directly into electricity.

In a PV cell, a semiconductor composed of a thin layer of silicon crystal absorbs photons, or particles of solar energy. The energy of the photons transfers to electrons in the semiconductor. The energized electrons then break free for the silicon atoms and flow in an electric current.

Typical solar cells include a glass cover to keep the weather out, an anti-reflective coating to prevent sunlight from bouncing off, and electrical contacts, or metallic grids that collect photons from the semiconductor and transfer them to an electric circuit.

Simple PV systems power everyday items like calculators and watches. More complicated systems run appliances, houses and spacecraft such as the International Space Station.

When finished, the space station will pack the most powerful solar power plant in space. It will include four sets of giant gold-colored solar wings. Each pair extends 240 feet (72 meters), which is longer than the wingspan of a Boeing 777 and the space station itself.

Composed of more than 250,000 solar cells, the entire collection of solar wings should generate enough energy to power a small neighborhood.

Some of the electricity will either be used immediately, to run life support systems and power scientific experiments, or be stored in batteries for use when the station is not in sunlight.

U.S. Department of Energy diagram of a solar cell

Sources: NASA, U.S. Department of Energy

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NASA
HSF - International Space Station
U.S. Department of Energy

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