Solar power refers to the energy created when solar radiation is converted into heat (thermal processes) or electricity (electric processes).

Solar energy describes several energy creation techniques that use the sun’s radiation. It has been used in traditional construction for centuries though in developed countries interest has fluctuated with the the price of fossil fuel.

The traditional use of solar energy as passive heating has influenced the design of homes and public buildings in many parts of the world: the most efficient dwellings historically have been designed, in the northern latitudes, with large windows facing south and small windows in the walls oriented toward the north. This simple building technique has for centuries reduced the need for other sources of energy to generate heat.

The industrial growth and economic prosperity of the West during the 20th century caused a massive abandonment of this type of construction and a simultaneous increase in the use of electricity and fuel to moderate home temperatures. The 21st century could signal a return to this type of passive energy use.

Solar energy is used in several different applications:

• To generate electricity through photovoltaics or solar electric panels. The latter convert heat into electricity.
• To use directly the heat generated: water and building heating, and cooking. The last option is particularly useful in regions of poor countries without traditional power sources.
• In the desalination of marine water for its use in everything from agricultural to industry.
• With the sun, the processes of distillation, evaporation, and photosynthesis all occur naturally. Many craft and industrial processes depend on this application of solar radiation.
• The strength and radiation of the sun varies according to time of day, latitude, atmospheric conditions -which limit it (i.e. “global dimming” is the negative effect of polution on the strength of the sun’s rays)- as well as, the position and inclination of the earth with respect to the sun.

Solar radiation can be used directly or indirectly. Direct radiation originates directly from the solar focus, without intermediary reflectors nor refractors, though it can be reflected and concentrated for use. It can’t be controlled, though it can be used as a passive system, for example, in the orientation and characteristics of a building with respect to the sun.

Among the distinct types of solar technology, the technological industry is focused on the production, commercialization and improvement of two types of electrical generating systems resulting from the collecting of solar rays:

• Photovoltaic solar energy: electricity is produced using semiconductor cells that react to solar radiation to generate electrical impulses. The photoelectric effect is possible thanks to the capacity of electromagnetic radiation to extract electrons from certain materials, mainly metals and semiconductors.
• Solar thermal energy: electricity is produced from a conventional thermodynamic cycle, by means of a fluid that is heated by the sun. The heat produced is transformed into electric power.

• More information about solar energy, in Wikipedia.