High School Physics

How is solar energy converted into electricity?

Solar energy is converted into electricity using photovoltaic (PV) cells or concentrating solar power plants. Photovoltaic cells convert sunlight directly into electricity.

solar energy for home

Individual photovoltaic (PV) cells are combined in modules of about 40 cells to form a solar panel; 10 to 20 solar panels are used to power a typical home.

The panels are usually mounted on the home facing south or mounted onto a tracking device that follows the sun for maximum exposure to sunlight.

Power plants and other industrial locations combine more solar panels to generate electricity.

solar power plants

Concentrating solar power plants collect the heat (energy) from the sun to heat a fluid, which produces steam that drives a generator to produce electricity.

The three main types of concentrating solar power systems are the parabolic trough, solar dish, and solar power tower, which describe the different types of collectors.

Parabolic troughs collectors have a long, rectangular, U-shaped reflector or mirror focused on the sun with a tube (receiver) along its length.

A solar dish looks very much like a large satellite dish that concentrates the sunlight into a thermal receiver that absorbs and collects the heat and transfers it to the engine generator. The engine produces mechanical power, which is used to run a generator converting mechanical power into electrical power.

A solar tower uses a field of flat, sun-tracking mirrors, called heliostats, to collect and concentrate the sunlight onto a tower-mounted heat exchanger (receiver). A fluid is heated in the receiver to generate steam, which is used in a generator to produce electricity.

How does a solar cell generate electricity?

A solar cell, also called a photovoltaic (PV) cell, consists of several layers of silicon-based material.

  • When photons, particles of solar energy from sunlight, strike a photovoltaic cell, they are reflected, pass through, or are absorbed. Absorbed photons provide energy to generate electricity.
  • The top p-layer absorbs light energy. This energy frees electrons at the junction layer between the p-layer and the n-layer.
  • The freed electrons collect at the bottom n-layer.
  • The loss of electrons from the top layer produces “holes” in the layer that are then filled by other electrons.
  • When a connection, or circuit, is completed between the p-layer and n-layer the flow of electrons creates an electric current.

The photovoltaic effect, including the naming of the p-layer and n-layer, was discovered by Russell Ohl (1898–1987), a researcher at Bell Labs, in 1940.

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