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.