History of Solar Energy
Solar energy isn’t a new phenomenon. It has been utilized in one form or another for thousands of years. The history of solar energy goes back to the beginning of time. In fact, the first recorded use of solar energy of any kind was in the 7th century B.C. The earliest use of solar power entailed using glass and mirrors. By using a magnifying glass, the sun’s rays could create an intense heat, and actually light a fire. As early as the 3rd century, we read that the Romans and Greeks lit their torches for religious purposes using this technique. Using bronze shields to focus sunlight, the Greek scientist, Archimedes actually set wooden ships on fire belonging to the Roman Empire as early as 212 B.C. The famous Roman bathhouses of the first through the fourth centuries A.D. were solar heated, using large South facing windows to let the sun’s warmth heat them. The Anasazi cliff dwellers in North America built their homes facing the South to capture the winter sun, thus providing heating.
The world’s first solar collector was credited to the Swiss scientist Horace de Saussure in 1776. Sir John Herschel later used this device to cook food during his expedition to South Africa in the 1830s. Robert Stirling, a minister for the Church of Scotland, applied for a patent on his economizer in Edinburgh, Scotland in 1816. He built heat engines in his spare time in his workshop. One of these engines was used by Lord Kelvin in one of his classes at the university where he taught. This same engine was later used in the dish/Stirling system, which was a solar thermal electric device that produced electrical power through the sun’s thermal energy.
Our present day solar panels found their genesis in 1839. The French scientist Edmond Becquerel discovered what is known as the photovoltaic effect. He experimented with an electrolytic cell made up of two metal electrodes which were placed within a solution that would conduct electricity. When exposed to light, this device would generate the flow of electricity. In 1873, Willoughby Smith discovered that selenium could be used for photoconductivity. In 1876, William Grylls Adams and Richard Evans Day discovered that when exposed to light, selenium would produce electricity. As early as 1883, Charles Fritts spoke about the first solar cells made from selenium wafers.
In 1891, Clarence Kemp patented the very first commercial solar water heater. In 1904, Wilhelm Hallwachs found that by combining copper and cuprous oxide, it created a photosensitive material. It was in 1905 that Albert Einstein published a paper on the photoelectric effect. Robert Millikan provided proof of the photoelectric effect through his experiments. It was in 1954 that photovoltaic technology had its beginning in the United States. Gerald Pearson, Daryl Chapin, and Calvin Fuller developed the silicon photovoltaic (PV) cell while employed at Bell Labs. These solar cells were capable of converting enough solar energy to actually operate electrical equipment.
In the mid 1950s, Frank Bridgers designed the world’s first commercial solar water heated office building. RCA Labs was approached by William Cherry of U.S. Signal Corps Laboratories in 1956 about developing photovoltaic cells for use on proposed Earth orbiting satellites. A couple of years later, his company fabricated n-on-p silicon photovoltaic cells. The space satellite Vanguard 1 used a small array of these cells to power its radios. That same year, Explorer III, Vanguard II, and Sputnik-3 were all launched with PV powered systems onboard. In 1964, NASA launched the first Nimbus spacecraft, which was a satellite entirely powered by a 470 watt PV array. The next year, Peter Glaser came up with the idea of a solar powered satellite station. The following year, the first Orbiting Astronomical Observatory was launched by NASA. This spacecraft was powered by a one kilowatt PV array.
Until this time, the cost of a solar system was approximately $100 per watt. In the 1970s, Dr. Elliot Bernam, working with Exxon Corporation designed a much more cost effective device, bringing the cost down to about $20 per watt. Exxon used these solar cells to power navigation warning lights and horns on their offshore gas and oil rigs. They were also used on lighthouses and railroad crossings. They were ideal for remote locations where power lines were unavailable. It was in 1972 that the Institute of Energy Conversion was established at the University of Delaware. At that time, research and development was conducted on thin-film photovoltaic systems. This was the first lab that was dedicated to R & D of PV technology. The Department of Energy established the Solar Energy Research Institute in 1977.
The world’s first village photovoltaic system was installed on the Papago Indian Reservation in Arizona in 1978. It was a 3.5 kilowatt system which provided water pumping and residential electricity for 15 homes until 1983. In 1980, ARCO Solar produced more than a megawatt of PV modules during the year. Paul MacCready built the very first solar powered aircraft in 1981. This plane was called the Solar Challenger. This aircraft had over 16,000 solar cells mounted to its wings and produced about 3,000 watts of power. The first solar powered car was constructed in 1982. It was driven by the Australian Hans Tholstrup between Sydney and Perth, approximately 2,800 miles in twenty days. This car was named the Quiet Achiever. Volkswagen started testing PV arrays that were mounted on the roofs of the Dasher station wagon in 1982. This generated 160 watts to operate the ignition system. During that year, the worldwide production of PV electricity exceeded 9.3 megawatts.
ARCO Solar constructed a six megawatt PV substation in Central California in 1983 which provided Pacific Gas & Electric enough energy to power 2,000 to 2,500 homes. Worldwide production of PV exceeded 21 megawatts in that same year, more than twice of that the previous year.
Early solar panels could only achieve an efficiency of 4%, but in 1985, The University of South Wales was able to achieve 20% efficiency with the silicon solar cells.
In 1986, solar took on another twist. They built the world’s largest solar thermal facility in Kramer Junction, California. This entailed rows of mirrors that were used to concentrate the sun’s energy to a system of pipes which circulated a heat transfer fluid. This was used to produce steam, which in turn powered a turbine in order to generate electricity. In that same year, ARCO Solar released their G-4000. This was the first commercial thin-film power module.
In 1988, Dr. Alvin Marks received two separate patents for two power technologies that he had developed. The first of those was for Lepcon, which consisted of glass panels that were covered with millions of aluminum or copper strips. These strips were less than one micron wide. As solar energy hit these metal strips, electrons would move along the metal and be collected as they escaped at one end. The other patent he developed was for the technology called Lumeloid. This utilized a similar approach, except rather than glass panels, they were made up of a cheaper film like sheet of plastic with conductive polymers which formed long chains.
Thin-film technology was improved in 1992 by the University of South Florida. They developed thin-film PV cells made of cadmium telluride which was almost 16% efficient. This was a breakthrough for this specific technology.
Pacific Gas & Electric installed its first grid supported photovoltaic system in 1993 near Kerman, California. This was a 500 kilowatt system. In 1994, the National Renewable Energy Lab developed a solar cell that was constructed from gallium indium phosphide and gallium arsenide. This cell was the first to exceed 30% efficiency. In 1998 the Pathfinder, which is a remote controlled solar powered aircraft set an altitude record. It climbed to an altitude of 80,000 feet, which is higher than any prop-driven aircraft had been able to achieve. Solar shingles, or roofing materials were also developed that year by the scientist, Subhendu Guha out of amorphous silicon. These shingles would mount directly to the roof in place of asphalt shingles. Spectrolab, Inc. and the National Renewable Energy Laboratory developed a PV cell that was 32.3% efficient in 1999. They achieved this by combining three layers of PV material into a single solar cell. Ideally, this cell is used in conjunction with lenses or mirrors which concentrate sunlight onto the cell.
In the year 2,000, the International Space Station has 32,800 solar cells installed on each wing. That same year, BP Solarex broke the previous performance records with two new thin-film solar modules. Their new modules achieved 10.8% conversion efficiency with a power output of 91.5 watts. That year, a family in Morrison, Colorado installed the largest residential system of that time on their home. This system had an output of 12 kilowatts. The very next year, NASA’s Helios, a solar powered aircraft set a new world record for a non-rocket powered aircraft of 96,863 feet which is more than 18 miles high.
In 2001, Japan announced plans to construct a satellite that would be able to beam energy back to Earth. This satellite, which had large solar panels installed, would then use a laser to transmit its power to an aircraft at an altitude of approximately 12 miles. This plane would then transmit the power on to the Earth.
Today, it is common for solar panels to produce 12% efficiency. I’m sure that number will continue to increase with the development of technology. With the use of single-crystal silicon, grown silicon is cut into thin wafers as thin as 200 microns. Some research cells have reached nearly 30% efficiency with commercial modules of single-crystal cells exceeding 20%. The other material that is used today is Multicrystalline silicon. This material is sliced from blocks of cast silicon which is less expensive to manufacture and less efficient than single-crystal silicon cells. Research tests approach 18% efficiency and commercial modules nearly 14 percent efficiency.
Researchers at MIT have recently developed materials that make it possible to actually print photovoltaic cells on paper, fabric, or other materials. When the paper is exposed to light, it generates electricity just like any other photovoltaic material. This technique represents a major departure from methods used before. This new technique utilizes vapors, not liquids. And it prints at temperatures less than 120 degrees Celsius. As a result, ordinary untreated paper, cloth or plastic can be used as a substrate upon which the cells are printed. Granted, the printing process is much more complex than Xeroxing a form letter. To create the array of PV cells on the paper, five layers of material are deposited onto the same sheet of paper in successive passes. A mask is also needed, which is made of paper. This helps to form the patterns of cells on the surface of the paper. This whole process must take place in a vacuum chamber as well. What is amazing is the resilient nature of this printing. The paper can be folded and unfolded 1,000 times with no measurable amount of performance loss. This PV material also reaches record high watts-per-kilogram in its performance. As you consider the history of solar energy, we have really come a long way since the beginning of time.