HISTORY OF SOLAR ENERGY

We have always used the energy of the sun as far back as humans have existed on this planet. As far back as 5,000 years ago, people "worshipped" the sun. Ra, the sun-god, who was considered the first king of Egypt. In Mesopotamia, the sun-god Shamash was a major deity and was equated with justice. In Greece there were two sun deities, Apollo and Helios. The influence of the sun also appears in other religions - Zoroastrianism, Mithraism, Roman religion, Hinduism, Buddhism, the Druids of England, the Aztecs of Mexico, the Incas of Peru, and many Native American tribes.In 1767, Swiss scientist Horace de Saussure built the world's first solar collector, which was used years later by Sir John Herschel to cook food during his South African expedition in the 1830s. Meanwhile, on September 27, 1816, Robert Stirling applies for a patent for his economiser at the Chancery in Edinburgh, Scotland. This engine is later used in the dish/Stirling system, a solar thermal electric technology that concentrates the sun's thermal energy to produce electric power. In 1839, Alexandre-Edmond Becquerel, a French physicist, discovered the so-called photovoltaic effect,[7] when he built a device that could measure the intensity of light by observing the strength of an electric current between two metal plates. When sunlight is absorbed by a solar cell, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic (PV) effect.Becquerel's conversion process transformed only 1% of the sunlight that fell on the submerged electrode into electricity. In other words, the conversion process was only 1% efficient. Following the initial discovery of the PV effect, scientists experimented with different materials in an attempt to find a practical use for PV systems. In the late nineteenth century, scientists discovered that the metal selenium was particularly sensitive to sunlight, and during the 1880 s Charles Fritts constructed the first selenium solar cell. His device, however, was inefficient, converting less than one percent of the received light into usable electricity.
John Ericsson, a Swedish inventor who lived and worked for most of his adult life in the United States, designed and built the world’s first solar-energy engine/dish in Pasadena, Calif. Ericsson presented the concept design for the solar machine (featured above) in 1876 at the centennial celebration in Philadelphia. The Fritts selenium solar cell was mostly forgotten until the 1950s, when the drive to produce an efficient solar cell was renewed. It was known that the key to the photovoltaic cell lay in creating a semiconductor that would release electrons when exposed to radiation within the visible spectrum. During this time, researchers at the Bell Telephone Laboratories were developing similar semiconductors to be used in communication systems. By accident, Bell scientists Calvin Fuller and Daryl Chapin found the perfect semiconductor: a hybridized crystal called a " doped" cell, which was made of phosphorous and boron. The first solar cells using these new crystals debuted in 1954 and yielded a conversion efficiency of nearly six percent. Later improvements in the design increased the efficiency to almost 15 percent. In 1957 Bell Telephone used a silicon solar cell to power a telephone repeater station in Georgia. The process was considered a success although it was still too inefficient to penetrate the general mmarketplace . The first real application of silicon solar cells came in 1958 when a solar array was used to provide electricity for the radio transmitter of Vanguard 1 , the second American satellite to orbit Earth. Solar cells have been used on almost every satellite launched since. By the 1960s, photovoltaic cells were used to power U.S. space satellites. By the 1980s, the simplest photovoltaic systems were being used commercially to power small calculators and wrist watches. Today, advanced solar-energy systems provide electricity to pump water, power communications equipment and increasingly generate electricity on a commercial scale. Two solar-energy technologies currently dominate the market for solar-based electricity production. Concentrating solar power systems direct sunlight through a magnifying lens, which increases the heat energy and drives a generator that produces electricity. Photovoltaics systems (PV) convert solar energy into electricity with semiconductors. A third technology, solar heating, absorbs the sun's energy with solar collectors and provides low-grade heat used directly for solar water heating, solar space heating in buildings, and solar pool heaters. From the mid 1950s to the early 1970s, PV research and development (R&D) was directed primarily toward space applications and satellite power. Large-scale development of solar collectors began in the United States in the mid-1970s under the Energy Research and Development Administration and continued under the auspices of the U.S. Department of Energy after 1976. In 1973, a greatly increased level of R&D on solar cells was initiated following the oil embargo in that year, which caused widespread concern regarding energy supply. In 1976, the U.S. Department of Energy, along with its Photovoltaics Program, was created. DOE, as well as many other international organizations, began funding PV R&D at appreciable levels, and a terrestrial solar cell industry quickly evolved. By the late twentieth century, solar energy had become practical and affordable enough to warrant its broad-scale marketing as one of the primary energy sources of the future. During the 1990s, the price of solar energy plunged 50 percent as technology improved. Meanwhile, PV applications went from a niche source of electricity to bringing solar technology into the margins of the mainstream. More than 10,000 homes in the United States were powered exclusively by solar energy in the late 1990s while an additional 200,000 homes supplemented electricity consumption with some form of photovoltaic system, according to the Solar Energy Industries Association. Although the solar power industry was valued globally at $5 billion in 2003, solar power still represented only about one percent of all electric power in the United States that year, primarily due to its persistently high costs and the continuing availability of cheap energy via traditional sources. As you will discover in the following sections, these barriers have fallen dramatically in recent years and unleashed a small revolution in the role the sun plays in humanity's daily life..