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The History of Solar Energy

Believe it or not, the active use of solar energy by humans dates back to the seventh century BCE when leases of glass or used to concentrate the sun’s rays in order to make a fire.  Greek and Roman citizens, the third century BCE, used convex mirrors to concentrate sunlight in order to light torches. There are even claims that bronze shields where used by the Greek navy to light enemy ships on fire, though no definitive evidence of this has ever been uncovered.

By the four century CE, the basics of passive solar design were being used by the Romans in the construction of their bathhouses.  These structures used large south facing windows in order to allow maximum solar warming.  In fact, the practice became so common but by the sixth century CE, Emperor Justinian embodied the right of all Romans to have access to the sun in the law. Similar south facing architecture has been observed in several cultures of the northern hemisphere.

Like many scientific disciplines, advances in solar technology slowed to a crawl during the dark ages.  The science would not see the light of day again (pun intended) until the 18th century when Swiss scientist Horace de Saussure built the first saw were collector in 1767. It became popular in the 1830s, when it was used by Sir John Herschel for cooking during a trip to South Africa.

In 1816, the utilization of solar energy took a tremendous leap forward when Robert Sterling invented a heat engine.  The design of that engine is used today in solar thermal applications such as Dish-Sterling concentrated solar collectors.

Following the work of Sterling, Edmond Becquerel became the first scientist to discover the photovoltaic effect, the underlying principle of photovoltaic cells (aka solar cells). Following Becquerels work, it was observed that Selenium had photovoltaic properties. This quickly led to the understanding that semiconductors (elements halfway between metals and nonmetals on the periodic table, were capable of producing electricity when exposed to light.  The first actual solar cells were developed by Charles Fritts in 1883.

Following the work of Fritts, several important advances where made that impacted solar energy production. First, Wilhelm Hallwachs found that combinations of copper and cuprous oxide showed photoelectric properties. This was the first step in advancing materials science for photocells. The next big discovery was a deeper understanding of the photoelectric effect by Albert Einstein in 1905.  Both of these discoveries were shortly followed by the understanding, in 1914, that it was possible to develop a barrier to the flow of electrons in photovoltaic devices.

While all this work was ongoing in the field of active solar energy, World War II helped to ignite new interest in passive solar design.  The interest was driven by energy shortages that resulted from the war and was spurred on by glass makers the published manuals on how to build a solar house.

True photovoltaic technology was first developed at Bell Labs, the famous laboratory of AT&T that was the birthplace of so many great ideas in modern technology, in 1954. The invention was the first silicon PV cell that was capable of powering an everyday electric device. In 1956, the first thoughts of using PV cells to create satellites were floated by William Cherry to RCA Labs. This suggested was followed two years later by the development of the Vanguard I satellite, which used silicon n-on-p cells to power its radios.

The 1960s and 70s saw refinement of PV technology and the development of alternatives to silicon, such as selenium and cadmium. It was also the time period when the first commercially successful PV companies were founded. In 1977, the U.S. Department of Energy launched the Solar Energy Research Institute, which later became the National Renewable Energy Laboratory (NREL) in 1991.

The year 1981 witnessed the building of the first solar powered aircraft called the “Solar Challenger.” The aircraft used over 16,000 solar cells to fly from France to England across the English Channel.  This feat was followed in 1982 by the first successful test drive of a solar powered car over a long distance.  The “Quiet Achiever” travel over 2800 miles from Sydney to Perth, in Australia, in about 20 days time.

Solar technology continued to improve throughout the 1980s as material science and production methods improved. The decade witnessed the development of Lepcon and Lumeloid, which provided vastly cheaper methods for producing solar panels.

In 1994, a gallium-indium solar cell became the first to pass 30% efficiency. In 1999, the total installed PV capacity in the world exceeded 1 gigawatt. This was followed in 2000 by the installation of more than 65,000 solar cells on the International Space Station. The next year, The Home Depot began selling residential solar power systems in three stores in California, a program that expanded to 61 stores the next year, evidencing that demand for solar technology was growing among consumers.

The first decade of the new millennium saw the implementation of solar incentives, such as feed-in-tariffs, by a number of governments across the globe. Removal of those subsidies in 2010, a result of the financial crisis, saw the failure of a number of large solar manufactures that relied on government subsidies to fund the expensive early days of solar production. Despite the loss of many subsidies, solar installations around the world continued to increase through 2012. Between 1985 and 2011, the cost of electricity from solar dropped from nearly $7 per watt to just over $1 per watt.

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