Solar energy is radiation from the sun that can be used to produce heat, cause chemical reactions, and generate electricity. The total amount of solar radiation reaching the earth is vastly greater than the world’s current and anticipated future energy requirements.
Solar energy technologies are broadly classified as active and passive. The former include the photovoltaic systems, solar radiation concentration systems, and solar water heating systems; the latter include the utilization of materials with favorable thermal or light-dispersing properties and the orienting of buildings to gain maximum benefit from sunlight.
Solar power is the conversion of solar energy into electricity, either directly using photovoltaic devices, indirectly using solar energy concentration systems, or by a combination of these. Photovoltaic cells convert light into an electric current using the photovoltaic effect. Solar energy concentration systems use lenses or mirrors together with solar tracking systems to focus a large area of sunlight into a small area to obtain an extremely high temperature to produce steam for conventional electric power plants.
Major disadvantages of solar energy have included the high costs of making the solar photovoltaic systems and solar radiation concentration systems, the fact that solar energy cannot be directly utilized at night, and the lower efficiency of solar systems in locations in the far northern and far southern latitudes. However, rapid advances in technology for capturing solar energy, converting it into heat and electricity, and storing it are making it increasingly economical and increasingly competitive with other energy sources, particularly fossil fuels and nuclear energy.