Solar energy is energy from the sun. It supports life on Earth and drives the Earth's weather. Solar energy predominantly arrives in the form of infrared, visible and ultraviolet light, and is either returned back to space or is absorbed. Nearly all of the absorbed energy is converted directly to heat, with a small but important fraction converted to chemical energy, such as in ozone production, photosynthesis or photovoltaic energy production.
Solar energy also broadly describes technologies that utilize sunlight. These technologies are diverse and date back millennia. The
Greeks,
Native Americans and
Chinese warmed their buildings by orienting them toward the sun. In Europe, farmers used elaborate field orientation and thermal mass to increase crop yields during the
Little Ice Age. Modern solar technologies continue to harness the sun to provide water heating, daylighting and even flight.
The utilization of solar energy and solar power spans from traditional technologies that provide food, heat and light to electricity which is uniquely modern. Solar energy is used in a wide variety of applications, including:
Biofuels Biomass Geothermal power Hydro power Solar power Tidal power Wave power Wind power Heat (
hot water,
building heat,
cooking, process heat)
Lighting (
daylighting, hybrid lighting, daylight savings time)
Electricity generation (
photovoltaics,
heat engines)
Transportation (
solar car,
solar plane, solar boat)
Desalination Biomass (wood, biofuel)
Clothes drying Energy from the Sun Many technologies use solar energy. Some classifications of solar technology are active, passive, direct and indirect.
Active solar systems use electrical and mechanical components such as tracking mechanisms, pumps and fans to process sunlight into usable outputs such as heating, lighting or electricity.
Passive solar systems use non-mechanical techniques of controlling, converting and distributing sunlight into usable outputs such as heating, lighting, cooling or ventilation. These techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the sun.
Direct solar generally refers to technologies or effects that involve a single conversion of sunlight which results in a usable form of energy.
Indirect solar generally refers to technologies or effects that involves multiple transformations of sunlight which result in a usable form of energy.
Types of technologies Main article: Passive solar building design Architecture and Urban planning Main articles: Daylighting and Light tube Lighting Main articles: Solar hot water, Solar combisystem, and Solar pond Water heating Main articles: Solar heating, Thermal mass, Trombe wall, and Solar chimney Heating, cooling and ventilation Main article: Photovoltaics Photovoltaics Main articles: Solar thermal energy, Parabolic trough, Solar power tower, Photovoltaic power stations, Solar power plants in the Mojave Desert, and List of solar thermal power stations Cooking Solar chemical processes convert solar energy into
chemical energy. These processes use both light (photochemical) and heat (endothermic) to drive chemical, thermochemical or thermoelectric reactions. Solar chemical reactions can be used to store solar energy or replace energy that would otherwise be required from an alternate source.
Electrochemical cells, commonly known as batteries, convert electrical energy into chemical energy. Solar energy can indirectly be converted into chemical energy in a system involving a photovoltaic to electrochemical cell exchange. A more direct approach involves the use of
photoelectrochemical cells which use light to produce hydrogen in a process similar to the
electrolysis of water. A third approach involves the use of
thermoelectic devices which convert a temperature difference between dissimilar metals into an electric current between those metals. This current can be use to produce hydrogen and oxygen through the electrolysis of water. The solar pioneer Mochout envisioned using the thermoelectric effect to store solar energy for later use during darkness; however, his experiments toward this end never progressed beyond primitive devices.
Solar chemical Main articles: Helios Prototype, Electric boat, and Solar balloon
Solar vehicles Main articles: desalination, Solar still, and Solar water disinfection Desalination and disinfection Main articles: Thermal mass, Thermal energy storage, Phase change material, Rechargeable battery, and Grid energy storage
Energy storage See the articles for individual countries listed at Category:Solar power by country Solar power by country Main article: Deployment of solar power to energy grids Development, deployment and economics ISES: International Solar Energy Society International
NGO supporting renewable and sustainable technologies.
ASES: American Solar Energy Association US organization supporting solar energy, efficiency and sustainable technologies.
SEIA: Solar Energy Industries Association US trade association of solar energy manufacturers, dealers, distributors, contractors
Canadian Solar industry Association ESTIF - European Solar Thermal Industry Federation See also:
Photovoltiac Industry Associations Solar energy research institutes 1973 energy crisis Absorption (electromagnetic radiation) COMES, French Solar Energy Authority
Deployment of solar power to energy grids Energy crisis Energy development Energy storage Energy: world resources and consumption European Union Climate Change Programme Future energy development Green electricity Global dimming insolation List of conservation topics Microgeneration Photoelectric effect Photovoltaics Renewable energy Solar air conditioning Solar balloon Solar car Solar cell insolation)
Solar heating Solar gain Solar ponds Solar power plants in the Mojave Desert Solar power satellite Solar power tower Solar radiation Solar thermal energy Solar tracker Solar updraft tower Sustainable design Timeline of solar energy Trans-Mediterranean Renewable Energy Cooperation (TREC)
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