Photovoltaic
solar cells are thin silicon disks that convert sunlight into electricity.
These disks act as energy sources for a wide variety of uses, including:
calculators and other small devices; telecommunications; rooftop panels on
individual houses; and for lighting, pumping, and medical refrigeration for
villages in developing countries. Solar cells in the form of large arrays are
used to power satellites and, in rare cases, to provide electricity for power
plants.
When
research into electricity began and simple batteries were being made and
studied, research into solar electricity followed amazingly quickly. As early
as 1839, Antoine-Cesar Becquerel exposed a chemical battery to the sun to see it produce voltage. This first
conversion of sunlight to electricity was one percent efficient. That is, one
percent of the incoming sunlight was converted into electricity. Willoughby
Smith in 1873 discovered that selenium was sensitive to light; in 1877 Adams
and Day noted that selenium, when exposed to light, produced an electrical
current. Charles Fritts, in the 1880s, also used gold-coated selenium to make
the first solar cell, again only one percent efficient. Nevertheless, Fritts
considered his cells to be revolutionary. He envisioned free solar energy to be
a means of decentralization, predicting that solar cells would replace power
plants with individually powered residences.
With
Albert Einstein's explanation in 1905 of the photoelectric effect—metal absorbs
energy from light and will retain that energy until too much light hits it—hope
soared anew that solar electricity at higher efficiencies would become
feasible. Little progress was made, however, until research into diodes and
transistors yielded the knowledge necessary for Bell scientists Gordon Pearson,
Darryl Chapin, and Cal Fuller to produce a silicon solar cell of four percent
efficiency in 1954.
Further
work brought the cell's efficiency up to 15 percent. Solar cells were first
used in the rural and isolated city of Americus, Georgia as a power source for
a telephone relay system, where it was used successfully for many years.
A
type of solar cell to fully meet domestic energy needs has not as yet been
developed, but solar cells have become successful in providing energy for
artificial satellites. Fuel systems and regular batteries were too heavy in a
program where every ounce mattered. Solar cells provide more energy per ounce
of weight than all other conventional energy sources, and they are
cost-effective.
Only
a few large scale photovoltaic power systems have been set up. Most efforts
lean toward providing solar cell technology to remote places that have no other
means of sophisticated power. About 50 megawatts are installed each year, yet
solar cells provide only about. 1 percent of all electricity now being
produced. Supporters of solar energy claim that the amount of solar radiation
reaching the Earth's surface each year could easily provide all our energy needs
several times over, yet solar cells have a long way to go before they fulfill
Charles Fritts's dream of free, fully accessible solar electricity.
Fig.Simple use of Solar Power
