Solar Electric 101
Turning the Sun’s Rays Into Electricity
Solar cells, also known as photovoltaic (PV) cells, are primarily made from the element silicon, which is a semiconductor. Photons from sunlight strike the cells and knock electrons into a higher state of energy. The PV cells have multiple electric fields that essentially force the electrons to move in a certain direction. This movement of electrons, called a current, is guided by metal contacts on the PV cell into conductors (wires).
The first practical application of photovoltaics was to power orbiting satellites and other spacecraft. During the energy crisis in the 1970s, photovoltaic technology gained recognition as a source of power for non-space applications. Since then, solar cells have increased in efficiency and durability. Silicon solar cells currently have conversion efficiencies of 10 to 20%.
PV cells are electrically connected to each other inside an aluminum frame with a tempered glass front, called a module. Modules are electrically connected to each other in multiples to create arrays. Arrays are mounted to roofs, the ground, or installed on poles. For maximum production, it is important that there is full sun on the array. PV modules produce the most energy when they are perpendicular to the angle of the sun.
Photovoltaic systems can either be stand alone (off grid) or grid connected (grid-tied). In a grid-tied system, the PV cells produce power in parallel with the electrical utility (your local power company). Utilities use a power grid to connect and distribute electricity to its customers. Off grid systems require batteries to store electricity for use as a constant power source.
Today, solar power is considered by many to be the most abundant, reliable, and cleanest of all known energy sources.