A solar farm, also known as a solar power plant, is a large-scale installation that uses sunlight to produce electric power. The “farm” part of the name comes from the idea of “harvesting” sunlight, as well as the resemblance of some power plants to fields full of crops. The typical solar farm will use one of two different methods to produce power: photovoltaic cells or concentrated solar thermal energy.
Photovoltaic (PV) solar farms take advantage of the photoelectric effect to convert light into electricity. They usually consist of vast numbers of PV solar cells collected into arrays. Since the amount of energy that can be produced is dependent upon the amount of sunlight that can be collected, a PV solar farm may have tens or hundreds of thousands of solar arrays laid out over large tracts of land. The arrays are usually individually mounted and are programmed to tilt to follow the sun as its angle changes. This movement allows the panels to capture the maximum intensity of sunlight throughout the day. An innovation that will continue to reduce the average cost for solar.
Solar thermal farms harness the power of the sun in a different way. At a thermal solar farm, sunlight is focused using lenses or reflectors at one or more locations, and is used to raise the temperature of a liquid, usually an oil. That liquid will be used to run a more traditional generator, often by boiling water to drive a steam turbine. There is more variation in structure at solar thermal farms than there is for PV farms — some have individual reflectors that each heat its own small area, while others have many mirrors all focused at a single point, often a tower or other elevated location.
Solar farms are usually located in flat areas, as building on level ground eliminates efficiency-reducing shadows. The best locations will also have clear skies and strong sunlight, though excessive heat can reduce the efficiency. Because they take up so much space, many solar farms are built in desert areas to avoid using up arable land. In addition, the intensity of sunlight varies depending on where on Earth the farm is built; locations near the Equator will have stronger light than those closer to the north or south poles, and will thus produce more energy.
Unlike fossil fueled power plants, a solar farm uses a renewable resource to produce electricity. Solar power is therefore usually considered to be better for the environment. In some cases, however, there has been concern over the environmental impact from building the plants, as their setup requires significant resources.