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Modern History of Solar

As modern understanding of light, thermodynamics and electricity progressed, so did the sophistication of devices for capturing and using the sun’s rays. The first solar collector ever constructed was built by Horace de Saussure. De Saussure applied the scientific method to the investigation of passive solar heating in an effort to determine the highest attainable temperature in a glass solar heat trap.

This device took the concept of passive solar to the next level by not only capturing the sunlight and converting it to heat, but by insulating against heat loss with the use of wood and wool. Temperatures as high as 240 oF were obtained this way, making these contraptions very useful for heating food during expeditions and sea voyages.

>Electricity and the 1800s

The late 1700s and early 1800s were the beginning of humanity’s quest to understand electricity. Though people were well aware that “shocks” could be produced by fish and other aquatic creatures, it was not until 1600 when English scientist William Gilbert began a careful investigation that the difference between magnetism and electricity came to light.

Gilbert named the new phenomenon electricus, and sparked the beginnings of investigation into the properties of electricity. In 1752, Benjamin Franklin conducted his famous kite experiment, proving that lightning was an electrical phenomenon. By 1800, Alessandro Volta have developed the battery, giving scientists are more reliable means of studying electricity. From that point, the study of electricity became the fulltime work of a number of scientific minds such as Ampere, Faraday, Ohm, and Maxwell.

In 1839, the French scientist Alexandre-Edmond Becquerel observed a startling phenomenon. When certain materials are exposed to light, they create an electric current. This event became known as the photovoltaic effect and is underlying principle of photovoltaic solar cells.

Shortly after the discovery of the photovoltaic effect, a number of attempts were made to capture the energy in sunlight and convert it into useful mechanical or electrical energy. In 1883, an American inventor by the name of Charles Fritts described the first solar cells. They were made from selenium wafers and thought they had no practical use, they provided clear evidence that solar energy could be harnessed to create electricity without moving parts or heat.

In 1891, the first solar water heat was created by Clarence Kemp based on principles from the heat box of de Saussure. Kemp’s product was called the Climax and was sold commercially with great success in places like California where sun was abundant and fuel costs were high.

>Materials Science and Advanced Photovoltaics

Advances in materials science during the 20th century meant that some of the obstacles of early “solar cells” could be overcome. Initially photoactive materials had high impedance, which meant that the resistance to the flow of electricity grew quickly as the materials heated up on exposure to sunlight. The result was that early solar materials were incapable of delivering enough current to be practical.

In 1904, Wilhelm Hallwachs found that combining copper and cuprous oxide resulted in a photosensitive material. This opened the door to the production of amalgams of various materials that had high conductivity and lower impedance.

Shortly after the work of Hallwachs, the Polish scientist Jan Czochralski found a way to grow single crystals of silicon. This meant silicon could be combined with other materials and manipulated to produce more effective semiconductors. This occurred in 1918 and in 1954, Daryl Chapin, Calvin Fuller, and Gerald Pearson develop the silicon photovoltaic cells at Bell Labs. The first silicon cell from bell labs was only 4% efficient, which was later increased to 11% efficiency. Current photovoltaic cells are around 40% efficient.

In 1958, the Vanguard I space satellite was the first to use a small photovoltaic system to power its radios for communication with Earth. It was quickly followed by the Explorer III, Vanguard II, and Sputnik-3 launches. Though the silicon solar cell was faltering in commercial venues at the time, it was exceptionally successful in powering satellites.

In 1959, Hoffman Electronics achieves 10% efficiency in photovoltaic cells and also learns how to reduce series resistance significantly. Shortly after in 1960, they achieve 14% efficiency. Of course solar cells are exceptionally expensive at the time and commercial installations are relatively limited.

>Modern Photovoltaics

In the 1970s, the price of photovoltaic cells began to decrease when Dr. Elliot Berman and Exxon Corporation brought the price down from $100 to $20 per watt. At that price, practical application of solar cells became viable. As a result of the decreased cost of photovoltaic arrays, the 1970s saw the installation of small-scale photovoltaic applications throughout the world. By 1977, total photovoltaic manufacturing exceeded 500 kilowatts.

With the 1980s came large-scale application of solar as well as solar powered vehicles. The Solar Challenger was the first solar powered aircraft and flew from France to England with the help of 16,000 solar cells.

In 1982, the first megawatt-scale power plant went online in California. It was developed by ARCO Solar who had just two years early passed the 1 megawatt photovoltaic milestone by manufacturing more than 1 megawatt of PV modules in one year. The success of the 1 megawatt plant in California prompted the U.S Depart of Energy to begin operation of Solar One, a 10 megawatt central-receiver power plant designed to establish if power-tower systems were feasible. It continued operation until 1988.

1982 also say the first solar powered car, the Quite Achiever, travel from Sydney, Australia to Perth, Australia in just 20 days, which was 10 days faster than the first gasoline powered car to make the trip.

ARCO followed up on its success in building the first megawatt-scale PV station by dedicating a 6 megawatt PV station in central California in 1983. In the same year, worldwide production of PVs exceeds 21 megawatts.

The ARCO PV achievement was followed in 1986 by production of the world’s largest solar thermal facility in California. The system used mirrors to concentrate heat onto pipes circulating oil. The oil was then used to produce steam using conventional turbines.

The 1990s saw the advent of “distributed power” when Pacific Gas & Electric installed the first grid-supported PV system in California. The system demonstrated that distributed power was feasible and perhaps preferable to centralized solar power generation.

In 1994, a solar cell was developed by the U.S. government that had an efficiency of 30%. This was followed two years later by the implementation of Solar Two, an upgrade to the Solar One project of the 1980s. Solar Two operated until 1999 and was used to demonstrate that solar energy could be stored to allow for power generation when the sun was not shining. By 1999, total PV capacity in the world reached 1 gigawatt.

The 21st century began with the production of the International Space Station, which relied on two arrays of 32,800 solar cells for power. The year after this accomplishment, Home Depot in the United States began selling solar power systems in California.

In 2001, Japan announced plans to develop a satellite-based solar power system. The system was to beam energy back to an airship 12 miles above the Earth using a laser. The airship would then transmit the power to the surface.

In the late part of the first decade of the 21st century, government initiatives have helped to increase the use of solar in residential and commercial applications. The use of feed-in-tariffs, particularly in the UK, helps to offset the cost of solar installations. This comes at the same time the PV cells reach approximately 40% efficiency for standard applications. The projection is that solar energy will be competitive with traditional forms in less than 50 years, even without government incentives.

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