Solar energy is a radiant light and heat from the Sun which is harnessed by a range of ever-evolving technologies such as solar heating , photovoltaics , solar thermal energy , solar architecture , molten salt power plants and artificial photosynthesis .  
It is an major source of renewable energy and Its technologies are Broadly caractérisée have Either passive solar or active solar DEPENDING ON ‘How They capture and distribute solar energy or convert it into solar power . Active solar techniques include the use of photovoltaic systems , concentrated solar power and solar water heating to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light-dispersing properties, and designing spaces that naturally circulate air .
The large magnitude of solar energy makes it a highly attractive source of electricity. The United Nations Development Program in its 2000 World Energy Assessment found that the annual potential of solar energy was 1,575-49,837 exajoules (EJ). This is several times larger than the total world energy consumption , which was 559.8 EJ in 2012.  
In 2011, the International Energy Agency said that “the development of affordable, inexhaustible and clean solar energy technologies will make it possible to increase the energy efficiency of an indigenous, inexhaustible and mostly import-independent resource, Increase sustainability , reduce pollution, lower costs of global warming , and keep fossil fuelprices lower than otherwise. need to be widely shared “. 
The Earth receives 174 petawatts (PW) from incoming solar radiation ( insolation ) at the upper atmosphere .  Approximately 30% is reflected by clouds, oceans and land masses. The spectrum of solar light at the Earth’s surface is mostly spread across the visible and near-infrared ranges with a small part in the near-ultraviolet .  Most of the world’s population in areas with insolation levels of 150-300 watts / m², or 3.5-7.0 kWh / m² per day. [ quote needed ]
Solar radiation is absorbed by the Earth ‘s surface, oceans – which cover about 71% of the globe – and atmosphere. Warm air containing evaporated water from the oceans, causing atmospheric circulation or convection . When the air reaches a high altitude, where the temperature is low, the water vapor condenses into clouds, which falls on the earth’s surface, completing the water cycle . The latent heat of water condensation amplifies convection, producing atmospheric phenomena such as wind, cyclones and anti-cyclones .  Sunlight absorbed by the oceans and land masses at an average temperature of 14 ° C.  Byphotosynthesis , green plants convert solar energy into chemically stored energy, which produces food, wood and the biomass from which fossil fuels are derived. 
The total solar energy absorbed by earth’s atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year.  In 2002, this was more energy in one hour than the world used in one year.   Photosynthesis catches approximately 3,000 EJ per year in biomass.  The amount of solar energy reaching the surface of the earth is so vast that it is about to be obtained from all sources of natural resources. mined uranium combined, 
|Yearly solar fluxes & human consumption 1|
|Biomass potential||~ 200|||
|Primary energy use 2||539|||
|Electricity 2||~ 67|||
|1 Energy given in Exajoule (EJ) = 10 18 J = 278 TWh
2 Consumption as of year 2010
The potential solar energy that could be used by humans as a result of the amount of solar energy. can acquire.
Geography affects solar energy potential because they are closer to the equator . However, the use of photovoltaics that can follow the position of the sun can significantly increase the solar energy potential in areas that are farther from the equator.  Solar radiation on the surface of the earth for solar panels to absorb. This limits the amount of energy that solar panels can absorb in one day. Cloud cover can affect the potential of solar panels because of solar cells.
In addition, solar energy can be used for solar panels. Roofs have been found to be suitable for solar cells, as many people have discovered that they can collect energy directly from their homes. Other areas that are suitable for solar cells are not suitable for use in solar plants. 
Solar technologies are characterized by their ability to capture and distribute solar energy, and to enable them to operate at different levels in the world. Although solar energy is primarily concerned with the use of solar radiation for all purposes, all renewable energies, other than Geothermal power and Tidal power , derive their energy directly or indirectly from the Sun.
Active solar technologies use photovoltaics, Concentrated solar power , solar thermal collectors , pumps, and fans to convert sunlight into Useful outputs. Passive solar techniques, with the use of solar thermal devices, and design referencing the position of a building to the Sun. Active solar technologies increase the supply of energy and are considered supply side technologies, while passive solar technologies reduce the demand for alternate resources and the demand for technologies. 
In 2000, the United Nations Development Program , A Department of Economic and Social Affairs, and World Energy Council published an estimate of the potential solar energy that could be used by humans the land that is usable by humans. The estimate has a global energy potential of 1.575-49.837 EJ per year (see table below) . 
|Region||North America||Latin America and Caribbean||Western Europe||Central and Eastern Europe||Former Soviet Union||Middle East and North Africa||Sub-Saharan Africa||Pacific Asia||South Asia||Centrally planned Asia||Pacific OECD|
Quantitative relationship of global solar potential vs. the world’s primary energy consumption :
Source: United Nations Development Program – World Energy Assessment (2000) 
Solar thermal technologies can be used for water heating, space heating, space cooling and heat generation. 
Early commercial adaptation
In 1878, at the Universal Exposition in Paris, Augustin Mouchot successfully demonstrated a solar steam engine, but could not keep it up.
In 1897, Frank Shuman , a US inventor, engineer and solar energy pioneer, built a small demonstration solar engine that worked by reflecting solar energy on square boxes filled with ether, which has a lower boiling point than water, and was fitted internally with black pipes which turn on a steam engine. In 1908 Shuman formed the Sun Power Company with the intention of building larger solar power plants. He, along with his technical advisor ASE Ackermann and British physicist Sir Charles Vernon Boys , [ citation needed ]An improved system using solar energy collectors can be used instead of increasing energy efficiency. Shuman then constructed a full-scale steam engine powered by low-pressure water, enabling him to patent the entire solar engine system by 1912.
Shuman built the world’s first solar thermal power station in Maadi , Egypt , between 1912 and 1913. His plant used parabolic troughs to power at 45-52 kilowatts (60-70 hp ) engine that pumped more than 22,000 liters (4,800 imp gal; 5,800 US gal) of water per minute from the Nile River to adjacent cotton fields. Although the outbreak of World War I and the discovery of cheap energy in the 1930s, the advancement of solar energy, Shuman’s vision and basic design were resurrected in the 1970s with a new wave of interest in solar thermal energy.  In 1916 Shuman was quoted in the media advocating solar energy’s use, saying:
We have proved to be the most profitable product in the world.- Frank Shuman, New York Times, July 2, 1916 
Solar hot water systems use sunlight to heat water. In low geographical latitudes (below 40 degrees) from 60 to 70% of the domestic hot water using temperatures up to 60 ° C can be provided by solar heating systems.  The most common types of solar water heaters are evacuated tube collectors (44%) and glazed flat collectors (34%) generally used for domestic hot water; and unglazed plastic collectors (21%) mainly used to heat swimming pools. 
As of 2007, the total installed capacity of solar thermal water systems was 154 thermal gigawatt (GW th ).  China is the world leader in their deployment with 70 GW th installed as of 2006 and a long-term goal of 210 GW th by 2020.  Israel and Cyprus are the leaders in the use of solar hot water 90% of homes using them.  In the United States, Canada, and Australia, heating swimming pools is the dominant application of solar hot water with an installed capacity of 18 GW th as of 2005. 
Heating, cooling and ventilation
In the United States, heating, ventilation and air conditioning (HVAC) systems account for 30% (4.65 EJ / yr) of the energy used in commercial buildings and nearly 50% (10.1 EJ / yr) of the energy used in residential buildings.   Solar heating, cooling and ventilation technologies can be used to offset a portion of this energy.
Thermal mass is any material that can be used to store heat-heat from the Sun in the box of solar energy. Common thermal materials include stone, cement and water. Historically they have been used in arid climates or warm temperatures to keep cool buildings. However, they can be used in cold weather areas to maintain warmth as well. The size and placement of thermal mass depends on several factors such as climate, daylighting and shading conditions. When properly incorporated, it is necessary to reduce the temperature and the temperature of the room. 
A solar chimney (or thermal chimney, in this context) is a passive solar ventilation system consisting of a vertical shaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated causing an updraft that pulls air through the building. Performance can be improved by using glazing and thermal mass materials  .
Deciduous trees and plants have been promoted as a way of controlling solar heating and cooling. When planted on the southern side of a southern hemisphere, their leaves provide shade during the summer.  Since bare, leafless trees shade 1/3 to 1/2 of incident solar radiation, there is a balance between the benefits of summer shading and the corresponding loss of winter heating. In climates with significant heating loads, deciduous trees should not be planted on the Equator-facing side of a building because they will interfere with winter solar availability. They can, however, be used to provide a degree of summer shading without appreciably affecting winter solar gain. 
Solar cookers use sunlight for cooking, drying and pasteurization . They can be grouped into three categories: box cookers, panel cookers and reflector cookers.  The simplest solar cooker is the box cooker first built by Horace de Saussure in 1767.  A basic box cooker consists of an insulated container with a transparent lid. It can be used effectively and partially at temperatures of 90-150 ° C (194-302 ° F). Panel cookers use a reflective panel to direct sunlight onto an insulated container and reach temperatures comparable to box cookers. Reflector cookers using various concentrating geometry (dish, trough, Fresnel mirrors) to focus on a cooking container. These cookers reach temperatures of 315 ° C (599 ° F) and above but require direct light to function properly and must be repositioned to track the Sun. 
Solar concentrating technologies such as parabolic dishes, troughs and Schefflers can provide process heat for commercial and industrial applications. The first commercial system was the Solar Total Energy Project (STEP) in Shenandoah, Georgia, where a field of 114 parabolic dishes provided 50% of the process heating, air conditioning and electrical requirements for a clothing factory. This grid-connected cogeneration system provided 400 kW of electricity plus thermal energy in the form of 401 kW steam and 468 kW chilled water, and had a one-hour peak load thermal storage.  Evaporation ponds are shallow pools that evaporate dissolved solids through evaporation. The use of evaporation ponds to obtain salt from seawater is one of the oldest applications of solar energy. Modern uses include concentrating brine solutions used in leach mining and removing dissolved solids from waste streams.  Clothes lines , clotheshorses , and clothes racks dry clothes through evaporation by wind and sunlight with electricity. In some states of the United States legislation protects the “right to dry” clothes.  Unglazed transpired collectors (UTC) are perforated sun-facing walls used for air preheating ventilation. UTCs can raise the incoming air temperature up to 22 ° C (40 ° F) and deliver temperatures of 45-60 ° C (113-140 ° F). The short payback period of transpired collectors (3 to 12 years) makes them more cost effective than glazed collection systems.  As of 2003, over 80 systems with a combined collector area of 35,000 square meters (380,000 sq ft) HAD-been installed worldwide, Including an 860 m 2 (9,300 sq ft) collector in Costa Rica used for drying coffee beans and a 1,300 m 2 (14,000 sq ft) collector in Coimbatore , India, used for drying marigolds. 
Solar distillation can be used to make saline or brackish drinking water . The first recorded instance of this 16th-century Arab alchemists.  A large-scale solar distillation project was first constructed in 1872 in the Chilean mining town of Las Salinas.  The plant, which had solar collection area of 4,700 m 2 (51,000 sq ft), could produce up to 22,700 L (5,000 US gal; 6,000 US gal) per day and operate for 40 years.  Individual stilldesigns include single-slope, double-slope, vertical, conical, inverted absorb, multi-wick, and multiple effect. These stills can operate in passive, active, or hybrid modes. Double-slope stills are the most economical for decentralized domestic purposes, while active multiple effects are more suitable for large-scale applications. 
Solar water disinfection (SODIS) involves exposing water-filled plastic polyethylene terephthalate (PET) bottles to sunlight for several hours.  Exposure times vary depending on weather and climate conditions.  It is recommended by the World Health Organization as a viable method for household water treatment and safe storage.  Over two million people in this world use this method for their daily drinking water. 
Solar energy can be used in a water stabilization pond to treat water without chemicals or electricity. A further environmental advantage is that algae grow in such ponds and consume carbon dioxide in photosynthesis, although it may produce toxic chemicals that make the water unusable.  
Molten salt technology
Molten salt can be used as a thermal energy storage method to conserve thermal energy by a solar tower or solar trough of a concentrated solar power plant , so it can be used to generate electricity in bad weather or at night. It was demonstrated in the Solar Two project from 1995-1999. The system is predicted to have an annual efficiency of 99%, with reference to the energy saved by storing heat before turning it into electricity, versus converting heat directly into electricity.    The molten salt mixtures vary. The most extended mixture contains sodium nitrate , potassium nitrate andcalcium nitrate . It is non-flammable and nontoxic, and has already been used in the chemical and metal industries as a heat-transport fluid, so it is possible to use such systems in non-solar applications.
The salt melts at 131 ° C (268 ° F). It is kept liquid at 288 ° C (550 ° F) in an insulated “cold” storage tank. The liquid salt is pumped through solar collectors where the heat is heats it to 566 ° C (1,051 ° F). It is then sent to a hot storage tank. This is so insulated that the thermal energy can be usedfully stored for up to a week. 
When electricity is needed, the hot salt is pumped to a conventional steam-generator to produce superheated steam for a turbine / generator as used in conventional oil, or nuclear power plant. A 100-megawatt turbine would need to tank about 9.1 meters (30 feet) tall and 24 meters (79 feet) in diameter for this design.
Several parabolic trough power plants in Spain  and solar power tower developer SolarReserve use this thermal energy storage concept. The Solana Generating Station in the US has six hours of storage by molten salt. The María Elena plant  is a 400 MW thermo-solar complex in the northern Chilean region of Antofagasta employing molten salt technology.
Solar power is the conversion of sunlight into electricity , Either Directly using photovoltaics (PV), or Indirectly using Concentrated solar power (CSP). CSP systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. PV converts light into electric current using the photoelectric effect.
Solar power is expected to become the world’s largest source of electricity by 2050, with solar photovoltaics and concentrated solar power contributing.  In 2016, after another year of rapid growth, solar generated 1.3% of global power. 
Commercial concentrated solar power plants were first developed in the 1980s. The 392 MW Ivanpah Solar Power Facility , in the Mojave Desert of California, is the largest solar power plant in the world. Other large solar power plants include the 150MW Solnova Solar Power Station and the 100MW Andasol solar power station , both in Spain. The 250 MW Agua Caliente Solar Project , in the United States, and the 221 MW Charanka Solar Park in India, are the world’s largest photovoltaic plants. Solar projects exceeding 1 GW are less than 5 kW, which are connected to the grid using net metering and / or a feed-in tariff. 
Worldwide growth of PV capacity group by MW (2006-2014)
In the last two decades, photovoltaics (PV), also known as solar PV, has evolved from a pure niche market of small scale applications towards becoming a mainstream electricity source. A solar cell is a device that converts light directly into electricity using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the 1880s.  In 1931 a German engineer, Dr. Bruno Lange, developed a photo cell using silver selenide in place of copper oxide .  Although the prototype selenium cells converted less than 1% of incident light into electricity, both Ernst Werner von Siemens andJames Clerk Maxwell recognized the importance of this discovery.  Following the work of Russell Ohl in the 1940s, Gerald Pearson, Calvin Fuller and Daryl Chapin researchers created the crystalline silicon solar cell in 1954.  These early solar cells cost 286 USD / watt and reach efficiencies of 4.5-6 %.  By 2012 available efficiencies exceeded 20%, and the maximum efficiency of photovoltaics research was in excess of 40%. 
Concentrated solar power
Concentrating Solar Power (CSP) systems in the field of sunlight into a small beam. The concentrated heat is then used as a heat source for a power plant. A wide range of concentrating technologies exists; The most developed are the parabolic trough, the concentrating linear fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the Sun and focus light. In all of These systems a working fluid is heated by the Concentrated sunlight, and is used for power generation Then gold energy storage. 
Architecture and urban planning
Sunlight has influenced building design since the beginning of architectural history.  Advanced solar architecture and urban planning methods were first employed by the Greeks and Chinese , who orientated their buildings towards the south to provide light and warmth. 
The relative features of passive solar architecture are related to the Sun, compact proportion (low area area to volume ratio), selective shading (overhangs) and thermal mass .  When these features are tailored to the local climate and environment they can produce well-lit spaces that stay in a comfortable temperature range. Socrates ‘ Megaron House is a classic example of passive solar design.  Reviews The most recent approaches to solar design use computer modeling tying together solar lighting , heating and ventilation systems in an integrated solar design package.  Active solar equipment such as pumps, fans and switchable can complement passive design and improve system performance.
Urban heat islands (UHI) are the most important areas in the world. The higher temperatures result from increased absorption of solar energy by urban materials such as asphalt and concrete, which have lower albedos and higher heat capacities than those in the natural environment. A straightforward method of counteracting the UHI is to paint buildings and roads white, and to plant trees in the area. Using these methods, a hypothetical “cool communities” program in Los Angeles, Los Angeles, Los Angeles, Los Angeles, Los Angeles, Los Angeles, Los Angeles, Los Angeles, Los Angeles, California. costs and healthcare savings. 
Agriculture and horticulture
Agriculture and horticulture seek to optimize the capture of solar energy in order to optimize the productivity of plants. Techniques such as timed planting cycles, tailored row orientation, staggered heights between rows and the mixing of plant varieties can improve crop yields.   While the sunlight is generally considered a plentiful resource, the exceptions highlight the importance of solar energy to agriculture. During the short growing seasons of the Little Ice Age , French and Englishfarmers employed fruit walls to maximize the collection of solar energy. These walls acted as thermal masses and accelerated ripening by keeping plants warm. Early fruit walls were built perpendicular to the ground and facing south, but over time, sloping walls were made to make better use of sunlight. In 1699, Duillier’s Nicolas Fatio even suggested using a tracking mechanism that could pivot to follow the Sun.  Applications of solar energy in agriculture, including pumping water, spraying crops, brooding chicks and drying chicken manure.   More recently the technology has been embraced by vintners, who uses the energy generated by solar panels to power grape presses. 
Greenhouses convert solar light to heat, enabling year-round production and growth in local environments. Primitive greenhouses were first used during Roman times to produce cucumbersyear-round for the Roman Emperor Tiberius .  The first modern greenhouses were built in Europe in the 16th century to keep exotic plants brought back from explorations abroad.  Greenhouses remain an important part of horticulture today, and plastic transparent materials have also been used in polytunnels and row covers .
Development of a solar-powered car has been an engineering goal since the 1980s. The World Solar Challenge is a biannual solar-powered race, where teams from universities and enterprises compete over 3.021 kilometers (1.877 mi) across central Australia from Darwin to Adelaide . In 1987, when it was founded, the winner’s average speed was 67 kilometers per hour (42 mph) and by 2007 the winner’s average speed had improved to 90.87 kilometers per hour (56.46 mph).  The North American Solar Challenge and the Planned South African Solar Challenge are comparable competitions that reflect an international interest in the engineering and development of solar powered vehicles. 
Some vehicles use solar panels for auxiliary power, such as air conditioning, to keep the interior cool, thus reducing fuel consumption. 
In 1975, the first practical solar boat was constructed in England.  By 1995, passenger boats incorporating PV panels began to appear extensively.  In 1996, Kenichi Horie made the first solar-powered cruise of the Pacific Ocean, and the Sun21 catamaran made the first solar-powered cruise of the Atlantic Ocean in the winter of 2006-2007.  There were plans to circumnavigate the globe in 2010. 
In 1974, the unmanned AstroFlight Sunrise airplane made the first solar flight. On April 29, 1979, the Solar Riser made a solar-powered, fully controlled, man-carrying flying machine, reaching an altitude of 40 ft (12 m). In 1980, the Gossamer Penguin made the first piloted flights powered by photovoltaics. This was soon followed by the Solar Challenger, which ran into the English Channel in July 1981. In 1990 Eric Scott Raymond in 21 hops flew from California to North Carolina using solar power.  Developments then turned to unmanned aerial vehicles (UAV) with the Pathfinder(1997) and subsequent designs, culminating in the Helios which set the altitude record for a non-rocket-propelled aircraft at 29,524 meters (96,864 ft) in 2001.  The Zephyr , developed by BAE Systems , is the latest in a line of record-breaking solar aircraft, making a 54-hour flight in 2007, and month-long flights were envisioned by 2010.  As of 2016, Solar Impulse , an electric aircraft , is currently circumnavigating the globe. It is a single-seat plane powered by solar cells and capable of taking off under its own power. The design allows the aircraft to remain airborne for several days. 
A solar balloon is a black balloon that is filled with ordinary air. As sunlight shines on the balloon, the air is heated up and expands causing an upward buoyancy force, much like an artificially heated hot air balloon . Some solar balloons are large enough for human flight, but use is limited to the market share of the area-to-payload ratio is relatively high. 
Solar chemical processes uses solar energy to drive chemical reactions. These processes offset energy that would otherwise come from a fossil fuel source and can also convert solar energy into storable and transportable fuels. Solar induced chemical reactions can be divided into thermochemical or photochemical .  A variety of fuels can be produced by artificial photosynthesis.  The multielectron catalytic chemistry involved in making carbon-based fuels (such as methanol ) from carbon dioxide reduction is challenging; a feasible alternative is hydrogenThe production of protons requires the use of multiple sources of electrons.  Some have considered solar fuel oil plants in coastal areas by 2050 – the splitting of sea water supplying hydrogen fueled by electric power plants and the pure water by-product going directly into the municipal water system.  Another vision involves all human structures covering the earth’s surface (ie, roads, vehicles and buildings) doing photosynthesis more efficiently than plants. 
Hydrogen production technologies have been a significant area of solar chemical research since the 1970s. Aside from electrolysis driven by photovoltaic or photochemical cells, several thermochemical processes have also been explored. One such route uses concentrators to split water into oxygen and hydrogen at high temperatures (2,300-2,600 ° C or 4,200-4,700 ° F). Another approach uses the heat from solar concentrators to drive the steam reformation of natural gas thereby Increasing the overall hydrogen yield Compared to conventional reforming methods.  Thermochemical cycles characterized by the decomposition and regeneration of reactants present another avenue for hydrogen production. The Solzinc process under development at theWeizmann Institute of Science uses 1 MW solar furnace to decompose zinc oxide (ZnO) at temperatures above 1,200 ° C (2,200 ° F). This initial reaction produces pure zinc, which can be reacted with water to produce hydrogen. 
Energy storage methods
Thermal mass systems can store solar energy in the form of heat at home . Thermal storage systems use Generally Readily available materials with high specific heat Capacities Such As water, earth and stone. Well-designed systems can lower peak demand , shift time-of-use to off-peak hours and reduce overall heating and cooling requirements.  
Phase change materials such as paraffin wax and Glauber’s salt are another thermal storage medium. These materials are inexpensive, readily available, and can provide domestically useful temperatures (approximately 64 ° C or 147 ° F). The “Dover House” (in Dover, Mass. ) Was first used by Glauber’s salt heating system, in 1948.  Solar energy can also be stored at high temperatures using molten salts . They are low cost, they have low cost, and have a high specific heat capacity. The Solar Two project uses this method of energy storage, allowing it to store 1.44terajoules (400,000 kWh) in its 68 cubic meters storage tank with an annual storage efficiency of about 99%. 
Off-grid PV systems have traditionally used rechargeable batteries to store excess electricity. With grid-tied systems, excess electricity can be sent to the transmission grid , while standard grid electricity can be used to meet shortfalls. Net metering programs give household systems a credit for any electricity they deliver to the grid. This is handled by ‘rolling back’ the meter when it produces more electricity than it consumes. If the net electricity is below zero, the utility rolls over the kilowatt hour credit to the next month. Other approaches involve the use of two meters, to measure electricity consumed vs. electricity produced. This is less common than the cost of the second meter. Most standard meters in both directions, making a second meter unnecessary.
Pumped-storage hydroelectricity stores energy in the form of water pumped when energy is available from a lower elevation reservoir to a higher elevation. The energy is recovered when it comes to releasing the water, with the pump becoming a hydroelectric power generator. 
Development, deployment and economics
Beginning with the surge in coal use qui accompagné the Industrial Revolution , energy consumption HAS Steadily transitioned from wood and biomass to fossil fuels . The early development of solar technologies starting in the 1860s was driven by an expectation that coal would soon become scarce. However, the development of solar technologies is stagnating in the early 20th century, the economy, and the utility of coal and petroleum . 
The 1973 oil embargo and the 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies.  Deployment strategies focused on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included in the US (SERI, now NREL ), Japan ( NEDO ), and Germany ( Fraunhofer Institute for Solar Energy Systems ISE ). 
Commercial solar water heaters started appearing in the United States in the 1890s.  These systems were used in the 1920s.  As with photovoltaics, solar water heating attracted renewed attention as a result of the crises in the 1970s but interest subsided in the 1980s due to falling petroleum prices. Development in the solar water heating sector progressed steadily throughout the 1990s and increased growth rates by 20% since 1999.  Mostly underestimated, solar water heating and cooling is by far the most GW as of 2007. 
The International Energy Agency has made significant contributions to the world of solar energy. 
The development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will increase countries’ energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, and lower fossil fuel prices. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be widely used. 
In 2011, postponement by the International Energy Agency found That solar energy technologies Such As photovoltaics, solar hot water and solar power Concentrated Could Provide a third of the world’s energy by 2060 if politicians commit to limiting climate change . The energy from the sun could play a key role in de-carbonizing the global economy with efficiencies and imposing costs on greenhouse gas emitters. “The strength of solar is the incredible variety and flexibility of applications, from small scale to big scale”. 
We have proved that we are able to provide the best of the world.- Frank Shuman , New York Times, July 2, 1916 
- Artificial photosynthesis
- Community solar farm
- Copper in renewable energy
- Global dimming
- Green electricity
- List of conservation topics
- List of renewable energy organizations
- List of solar energy topics
- Photovoltaic system
- Renewable heat
- Renewable energy by country
- Soil solarization
- Solar Decathlon
- Solar easement
- Solar energy use in rural Africa
- Solar updraft tower
- Solar power satellite
- Solar tracker
- Timeline of solar cells
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