The solar industry has exploded in the last several decades, as the technology has become more affordable and readily available to the average homeowner. But the technology behind solar isn't anything new. In fact, there is evidence of utilizing solar energy for various purposes that can be traced back to the 7th century B.C. Check out the interesting timeline below to see how we've always harnessed the sun's power for our benefit.
7th Century B.C. Magnifying glass used to concentrate the sun's power to start fires
3rd Century B.C. Greeks and Romans use burning mirrors to light torches
2nd Century B.C. Evidence that the Greek Navy was experimenting with bronze shields reflecting the sun's rays to set fire to ships at sea
20 A.D. Chinese document the use of mirrors to light torches
1st to 4th Century A.D. Roman bathhouses built with South facing windows for warmth
1200s A.D. Anasazi people build South facing cliff dwellings for warmth, demonstrating passive solar design
1767 Swiss scientist Horace de Saussure was credited with building the first solar collector, which was later used by Sir John Herschel to cook food during his South Africa expedition in the 1830s.
1816 Robert Stirling applied for a patent for his economizer. Stirling was a minister by trade, but in his spare time, he built heat engines in his home workshop. This engine was later used in the dish/Stirling system, a solar thermal electric technology that concentrates the sun's thermal energy to produce power
1839 Edmond Becquerel discovers the photovoltaic effect
1860 August Mouchet proposed an idea for solar-powered steam engines. In the following two decades, he and his assistant constructed the first solar powered engines and used them for a variety of applications. These became the predecessors of modern parabolic dish collectors
1873 Willoughby Smith discovered the photoconductivity of selenium
1876 William Grylls Adams and Richard Evans Day discover that selenium produces electricity when exposed to light. They proved a solid material could change light into electricity without heat or moving parts
1880 Samuel P. Langley invents the bolometer, which measures light from stars and the sun's heat rays.
1883 Charles Fritts describes the first solar cells made from selenium wafers
1887 Heinrich Hertz discovers that ultraviolet light altered the lowest voltage capable of causing a spark to jump between two metal electrodes
1891 Clarence Kemp patented the first commercial solar water heater
1904 Wilhelm Hallwachs discovers that a combination of copper and cuprous oxide is photosensitive
1905 Albert Einstein publishes his paper on the photoelectric effect
1908 William J. Bailey invents a solar collector with copper coils and an insulated box (roughly, the present design)
1914 The existence of a barrier layer in photovoltaic devices is noted
1918 Jan Czochralski develops a way to grow single-crystal silicon
1921 Albert Einstein wins the Nobel Prize for his theories explaining the photoelectric effect
1932 Audbert and Stora discover the photovoltaic effect in cadmium sulfide
1947 Passive solar buildings in the US were in high demand, as a result of the scarce energy during WWII. Your Solar House was published, which profiled forty-nine of the nation's greatest solar architects
1953 Dr. Dan Trivich makes the first theoretical calculations of the efficiencies of various materials of different band gap width based on the spectrum of the sun
1954 Daryl Chapin, Calvin Fuller and Gerald Pearson develop the silicon photovoltaic cell at Bell labs. This was the first solar cell capable of converting enough energy to run everyday equipment. The first prototype had 4% efficiency
1955 Western Electric began to sell commercial licenses for silicon photovoltaic (PV) chargers and devices that decoded computer punch cards and tape
1950s Frank Bridgers designs the world's first commercial office building using solar water heating and passive design. This has been operating since that time.
1956 William Cherry approaches RCA labs about developing PV cells for proposed orbiting Earth satellites
1957 Hoffman Electronics achieves an 8% efficient PV cell
1958 U.S. Signal Corps Laboratories fabricates n-on-p silicon PV cells
1958 Hoffman Electronics achieves an 9% efficient PV cell
1958 The Vanguard I space satellite used a small array to power its radios. Later that year, Explorer III, Vanguard II and Sputnik-3 were launched with PV powered systems on board. Despite faltering attempts to commercialize the silicon solar cell in the 50s and 60s, it was used successfully in powering satellites. It became the accepted energy source for space applications and remains so today.
1959 Hoffman Electronics achieves an 10% efficient PV cell. They also learn to use a grid contact, reducing resistance
1960 Hoffman Electronics achieves a 14% efficient PV cell
1960 Silicon Sensors, Inc, is founded and starts producing selenium and silicon PV cells
1962 Bell Telephone Laboratories launches the first telecommunication satellite
1963 Sharp Corporation succeeds in producing practical silicon PV modules
1963 Japan installs a 242 watt array, the world's largest at that time
1964 NASA launches the first Nimbus spacecraft--a satellite powered by a 470-watt PV array
1966 NASA launches the first Orbiting Astronomical Observatory, powered by a 1 kW PV array
1969 The Odeillo solar furnace was constructed in France, featuring an 8-story parabolic mirror
1970s Dr. Elliot Berman, designs a significantly less costly solar cell, bringing price down from $100 per watt to $20 per watt. Solar cells begin to power navigation warning lights and horns on offshore gas and oil rigs, lighthouses, railroad crossings and domestic solar applications began to be viewed as sensible applications.
1972 The Institute of Energy Conversion is established at the University of Delaware to perform research and development on thin-film PV and solar thermal systems, becoming the first laboratory dedicated to PV research and development.
1973 The University of Delaware builds "Solar One," one of the world's first PV powered residences. The system is a PV/thermal hybrid.
1976 The NASA Lewis Research Center starts installing 83 PV power systems on every continent except Australia.
1976 David Carlson and Christopher Wronski fabricate first amorphous silicon PV cells
1977 The US Department of energy launches the Solar Energy Research Institute
1977 Total photovoltaic manufacturing production exceeds 500 kilowatts
1978 NASA's Lewis Research Center dedicates a 3.5kW PV system installed on Papago Indian Reservation, the world's first village PV system. This is used to provide water pumping and residential electricity for 15 homes until 1983 when grid electricity reached the village.
1980 ARCO Solar becomes the first company to produce more than 1 megawatt of PV modules in 1 year
1980 University of Delaware creates the first thin-film solar cell that exceeds 10% efficiency using copper/cadmium sulfide
1981 Paul MacCready builds the first solar-powered aircraft that flies from France to England.
1982 The first PV megawatt-scale power station goes on-line in California
1982 Hans Tholstrup drives the first solar-powered car
1982 The US Department of Energy, along with an industry consortium, begins operating Solar One, a 10-megawatt central-receiver demonstration project.
1982 Worldwide PV production exceeds 9.3 megawatts
1993 Worldwide PV production exceeds 21.3 megawatts
1985 The University of South Wales breaks the 20% efficiency barrier
1986 The world's largest thermal facility, in California, was commissioned.
1986 ARCO Solar releases the G-4000, the world's first commercial thin-film power module
1988 Dr. Alvin Marks receives patents for two solar power technologies he developed: Lepcon and Lumeloid.
1991 President George Bush redesignates the US Department of Energy's Solar Energy Research Institute as the National Renewable Energy Laboratory
1992 University of South Florida develops a 15.9% efficient thin-film PV cell
1992 A 7.5 kW prototype dish system using an advanced stretched-membrane concentrator becomes operational
1993 Pacific Gas & Electric completes installation of the first grid-supported PV system in California, becoming the first "distributed power" effort.
1994 The National Renewable Energy Laboratory completes construction of their research facility, which was recognized as the most energy efficient of all US government buildings
1994 The National Renewable Energy Laboratory develops a solar cell that becomes the first one to exceed 30% conversion efficiency
1999 Construction was completed on 4 Times Square, which incorporated more energy-efficient building techniques than any other commercial skyscraper
1999 Spectrolab Inc develops a PV cell that converts 32.3% of sunlight to electricity\
1999 Cumulative worldwide installed PV capacity reaches 1000 megawatts
2000 Solar production begins production in Ohio at the world's largest PV manufacturing plant with an estimated capacity of producing enough panels to generate 100 megawatts of power
2000 At the International Space Station, astronauts begin installing panels on what will be the largest solar power array developed in space
2000 Sandia National Laboratories develops a new inverter that increases the safety of systems during a power outage
2000 Two new thin-film solar modules break previous performance records
2001-Present Day
Solar has continued to only get more powerful and efficient with every passing year. More affordable parts mean more affordable arrays and more availability to residents and businesses. The average solar panels today hit the efficiency mark of around 25%. It's fascinating to look back through the 20th century and see how solar got where it is today!
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