Photovoltaics literally means “light electricity.” Most people know this technology as “solar panels.” Solar panels are made up of photovoltaic cells or PV cells, which convert sunlight directly into electricity. These cells are actually thin wafers of silicon. The common name for silicon is glass, which is made by melting down quartz beach sand. This melted silicon is then re-crystallized into cylinders of crystalline silica. These tubes are then cut as thinly as possible into wafers. When one of these wafers is hit by a particle of sunlight, or photon, an electron belonging to one of the silicon atoms is energized and breaks free from the atom. This electron joins others, freed in the same process and together they flow to the end of the cell. These electrons then join other flowing electrons from other cells that are wired together to form the solar panel. This flow of electrons is what we know as electricity.

If a photovoltaic system produces more electricity than is needed at any given moment, the surplus can be stored for later use nearby where it was generated, or it can be traded to the electric company. Batteries are commonly used to store surplus energy. Or the surplus can be use to split water molecules which then get stored as hydrogen. (See section on Hydrogen.) If the electricity is going to be traded to the electric company, it needs to be the same type of electricity that is already in the grid.

Electricity comes in two forms, direct current (DC) and alternating current (AC). PV cells generate DC electricity and batteries store DC electricity. The electricity that comes across the wires and into our homes for appliances and lights is called AC. An inverter can be used to change DC electricity generated by photovoltaics into AC. This AC electricity can then be used in the way we are used to, or if there is extra it can go out onto the wires for others to use. Alternatively, special DC appliances do exist for use without the inverter.

Photovoltaics are a great way to produce clean electricity from the sun, especially for remote locations, such as camps in the deep woods, or on islands, or in places not reached by the electric grid. Solar panels are also being used in isolated locations like road signs, remote weather stations, and communication towers. Because these systems are becoming more affordable they are being installed on the tops of city buildings, and roofs of regular homes. These locations then become small power plants using the sun’s energy.