Photovoltaics - Solar Electric Cells, producing power from the sun

Photovoltaics
Solar Electric

Additional PV Information
	Frequently Asked Questions
	Cells and Arrays
	Battery Storage and Conversion
	System Components

The ability to produce electricity directly from the sun's energy is a revolutionary development. The technology involved in the production of these silicon cells is complicated and the efficiencies are still not even close to those of thermal solar applications, but these unique energy devices are now seen in places as common as the yard (solar powered lights), the highways (solar powered traffic lights and sign lights), and of course the common calculator.

Photovoltaics is the direct conversion of light into electricity. 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 electric current results that can be used as electricity.
	This diagram illustrates the operation of a basic photovoltaic cell, also called a solar cell. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current -- that is, electricity.
This electricity can then be used to power a load, such as a light bulb or a water pump. A typical four-inch silicon solar cell produces about one-and-a-half watts of electricity in bright noon-time sunshine. Remote locations such as billboards, road signs and other areas where it is cost effective to install solar electric systems with battery backup are becoming more and more common.

Solar cells are made of the same semiconductor materials (usually silicon) used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other.

The basic components of a solar electric array are the photovoltaic panels, battery storage and other sub-assemblies that regulate the storage and release of the sun's electric current.

There is a tendency to dismiss the use of solar-generated electricity because of its relatively high price per kilowatt-hour as compared to traditional sources of energy, especially grid- supplied electricity. However, the issue is not so much what solar electricity costs, but rather what the service it provides is worth to the user.