Harnessing Solar Power and Earth's Renewable Energy Sources

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Harnessing Solar Power and Earth's Renewable Energy Sources

Overview

In 1839 a young physicist experimenting with light discovered the photovoltaic effect, which would be exploited to create the world's first solar cells. The resulting photovoltaic cells were slowly perfected over the following century, and in 1954 Bell Laboratories developed the first practical solar cells, made of silicon. By the late twentieth century scientists had embraced these clean, renewable (and modular) energy sources, finding numerous applications to take advantage of the Sun's power. In the course of finding applications for solar power, scientists also searched for alternatives to fossil fuels, turning to other "green" technologies such as wind, hydro, and geothermal power.

Background

From man's earliest days on Earth, he has investigated his natural surroundings, exploring infinite uses for the byproducts of nature—water, stone, wood, metals. As this scientific exploration evolved, man's interest in his world produced a curiosity for the heavens, and he began studying the Sun and the stars in the sky, discovering, in the process, that sunlight provided energy. While the largest solar energy system on Earth occurs naturally in its green vegetation (where the sunlight causes chlorophyll to combine the air's carbon dioxide with water supplied by plant roots, producing carbohydrates—sugars, starch, and cellulose), man searched for synthetic methods to harness the sunlight. In 1839 French physicist Alexandre Edmond Becquerel (1820-1891) observed that light falling on certain materials could produce electricity, a phenomenon he termed the "photovoltaic effect."

Building on Becquerel's observations, scientist Willoughby Smith experimented with other materials, and in 1873 he discovered the photoconductivity of selenium. Soon afterwards, in 1877, William G. Adams and R. E. Day observed the photovoltaic effect in solid selenium, then developed a primitive (it converted less than one percent of the Sun's energy into electricity) photovoltaic cell from the selenium. In 1883 Charles Fritts, an American inventor, improved upon Adams and Day's design with his solar cells made from selenium wafers. As a result of the new selenium cells, and experiments in the 1920s with solar cells made of copper and copper oxide, the photovoltaic cells found their first practical application. Cells of both selenium and copper oxide were adopted in the emerging field of photography for use in light-measuring devices. (In the late twentieth century, light sensors for cameras were still made from selenium.)

In their search for a more practical and efficient solar cell, scientists continued to experiment with photovoltaic materials in the 1940s. In the early 1950s major progress was achieved when a sophisticated crystal growing method, invented in 1918 by Polish scientist Jan Czochralski, was used to produce highly pure crystalline silicon. In 1954 at Bell Laboratories in New Jersey, researchers Daryl M. Chapin, Calvin S. Fuller, and Gerald Leondus Pearson (1905 - ) used the Czochralski process to create the world's first practical photovoltaic cell, made from crystalline silicon. (The patent for their "Solar Energy Converting Apparatus" was issued in 1957.) at first, the cells could perform with an efficiency of only 4%, but, within a few months, the researchers had raised efficiency to 6%. Soon, the efficiency was 11%. The researchers' next obstacle was in producing a silicon cell that was less costly. This seemed an insurmountable problem. Had it not been for mankind's growing interest in space, the technological advancement of photovoltaic cells might have been stalled.

Impact

In July 1958 the U.S. Congress passed the National Aeronautics and Space Act, which created the National Aeronautics and Space Administration (NASA) and jumpstarted U.S. space science and exploration. Before that, however, U.S. scientists had been researching the launch of a satellite to collect geophysical data in and above the earth's atmosphere as part of the International Geophysical Year (IGY) research program. A key aspect of this satellite project was a search for a lightweight, long-lasting power source. The answer was found in the silicon solar cells originally designed by the team at Bell Laboratories.

In March 1958 the U.S. launched the world's first photovoltaic-powered satellite, Vanguard 1, which was the second U.S. satellite deployed into orbit above the earth. The satellite power system operated for eight years aboard Vanguard 1, a breakthrough for solar cell technology as its success led to large contracts from NASA and the expansion of the photovoltaic industry. By the late 1960s at least four U.S. companies were producing hundreds of thousands of solar cells each year, many earmarked for the growing satellite industry. (In the late twentieth century, solar cells power virtually all Earth-orbiting satellites.)

Achievements in solar cell development during the buildup of the space program included a major increase in cell efficiency and reductions in cost, but photovoltaic cells had still not found many terrestrial applications. Then, the mid-1970s oil embargo saw fossil-fuel costs soar dramatically. As a product of the oil crisis, the U.S. Department of Energy funded the Federal Photovoltaic Utilization Program, resulting in the installation and testing of thousands of solar power systems. Other applications followed.

In 1973 the University of Delaware built one of the world's first photovoltaic residences, Solar One. In 1982 the first photovoltaic power station was brought online in Hysperia, California. By the early 1990s electric utilities in 20 U.S. states had installed nearly 2,000 cost-effective photovoltaic systems. The Gulf War of 1990 again triggered interest in non-fossil fuel energy alternatives, and by the end of the 1990s there were several hundred thousand photovoltaic systems installed worldwide. In 1998 a team of Harvard University researchers led by physicist Eric Mazur discovered a new "spiky" black silicon whose future in photovoltaic technology was still being researched at the end of the century. As solar cell technology continued to progress, new discoveries like this brought on even more possibilities.

While the emerging technology of photovoltaics converted the Sun's energy into electricity, progress was made investigating other solar energy alternatives—mainly addressing the transfer of the Sun's heat to a fluid, which was then used to warm buildings, heat water, and even generate electricity. Solar thermal activities such as these were nothing new. In 100 A.D. historian Pliny the Younger (62-113) built a summer home in Northern Italy that featured thin sheets of mica windows in one room, which got hotter than the others, saving on short supplies of wood. By the sixth century sunrooms on houses and public buildings were common. Advances in glass technology, such as double and triple pane windows and low emissivity glass that employed a coating to allow heat in but not out, were a large contributor to further building efficiencies.

Just as buildings harnessed the Sun's energy for centuries, solar heating for water and other functions had also been practiced for many years. Solar thermal collectors, first built in 1767 by Swiss scientist Horace de Saussure (1740-1799), found many applications. In 1891 Baltimore inventor Clarence Kemp patented the first commercial solar water heater. After photovoltaic cells were perfected, the 1970s saw President Jimmy Carter (1924 - ) authorizing the installation of solar water heating panels on the White House. Solar pool heating technology wasn't far behind. Solar thermal electric power systems also developed that focused the Sun's power on heating water to make steam that was subsequently used to rotate a turbine attached to an electric generator. In 1998 in Southern California, these thermoelectric systems met the energy needs of over 350,000 people and were part of the world's largest solar energy power plant.

Besides the expansion of solar energy systems, the energy dilemma spotlighted by the 1973 oil embargo and the 1990 Gulf War brought about advancements in other renewable energy technologies. Wind power, actually generated as a result of temperature differences on the earth's surface caused by the Sun, had been one of the first natural energy sources utilized by man. Windmills, said to be invented by the Chinese and used as early as 200 b.c. by the Persians, were updated in the 1970s. Governmentsponsored wind turbine development programs flourished in the United States in the twentieth century. Tax credits for investors (which expired in 1985) resulted in nearly 7,000 turbines being installed in California alone between 1981 and 1984. Advancements in design reduced the costs of wind power, making it cost-competitive in many electric power applications.

Another inexpensive renewable energy source explored was that of hydropower, which harnesses falling water, usually in rivers. The most common form of hydropower was found in dams on these rivers. By the mid-1990s hydropower was generating about 10% of the United States' electricity—supplying enough energy to power whole towns, cities, and even entire regions of the country. Water also played a part in early usage of geothermal power. For at least 10,000 years mankind had used hot springs for cooking, refuge (they were neutral zones where members of warring nations could bathe together in peace), and, of course, relaxation. The exploitation of geothermal resources deepened beyond hot springs in 1892, when the world's first district heating system in Boise, Idaho, was served by pipes from their hot springs. In 1922 John D. Grant founded the United States' first geothermal power plant near The Geysers in California. More plants followed and alternative uses of geothermal energy, including agribusinesses such as crop drying (introduced by Geothermal Food Processors, Inc. in 1978), were initiated. By the 1990s engineers and scientists were developing technologies that would allow mankind to probe more than 10 miles below the earth's surface in search of geothermal energy. Along with photovoltaic cells and solar thermal technologies, hydro and geothermal power became viable alternatives to fossil fuel by the end of the twentieth century.

From the early efforts of researchers to harness the Sun's energy through photovoltaic cells, to discoveries such as a "spiky" black silicon, from windmills to sophisticated turbines, scientists endeavored to learn more about the myriad uses for the byproducts of nature. As scientists continue to explore all of these renewable energy technologies, constantly improving efficiencies and reducing costs, it may one day be possible to eliminate most of the world's fossil-fuel consumption.

ANN T. MARSDEN