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SOLAR ENERGY
While most of the current sustainable options for energy
production use the sun in an indirect way, solar power
tries to harness that power directly, either by radiated
heat or to generate electricity. Solar power is the most
under-utilized of all sustainable sources; enough solar
energy hits the earth every minute to meet world-wide
energy needs for a full year, but only a minute
percentage is currently harnessed.
There are four methods of using solar energy. Passive
collection is the oldest method, and tries to capture
and utilize the sun's energy in its natural state,
without the use of a mechanical device. For example, a
greenhouse does not modify the thermal or light energy
captured by the sun, but simply contains it. In some
small-scale applications (particularly homes), solar
energy is used to heat water, which is then piped to
different locations. To a lesser extent, angling windows
and mirrors to light a room or theatre are also uses of
passive solar collection.
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Secondly, energy can be concentrated and collected using
lenses, similar to the way a magnifying glass can be
used to focus the sun's rays to start a fire. Many of
the large-scale scientific or industrial applications
use a modification of this method, such as movable
mirror arrays that can be rotated to maintain a direct
angle to sunlight. These arrays, sometimes called solar
furnaces, can generate sustained temperatures in the
hundreds of degrees quite easily, and one in Odeillo,
France reportedly reaches three-thousand degrees
Celsius. On a smaller scale, solar furnaces the size of
a home satellite dish are used in developing nations to
boil water or cook food in remote locations.
A third application, by far the most commercially
important, is the use of solar power to generate
electricity. In most cases, the thermal radiation from
the sun is used to convert water to steam, which then
turns a turbine to create electricity. The methods of
concentration outlined above, such as mirrors and
lenses, are used to enhance this process. Often a
container of oil is heated by these arrays to several
thousand degrees, which in turn is used to convert water
to steam.
Finally, the famous solar panels used on satellites or
homes often use photovoltaic cells to generate
electricity as well, though in this case the light from
the sun causes an electrical charge that is then
converted to a direct electrical current. Albert
Einstein first described the theory for this process in
1905, and it gained in popularity during the 1970s
energy crisis. In a photovoltaic cell, a semi-conductive
material (usually silicon) is exposed to light. The
energy from the light knocks electrons loose from the
silicon, creating an electrical charge that can then be
harnessed.
Solar energy currently accounts for less than one
percent of the world-wide energy production, but many
scientists feel that it may be the most viable renewable
source in the long-term. The life cycle of the sun is
considered in the billions of years, and is for all
intents and purposes unlimited. Just as important, as
mankind potentially extends into space, solar energy is
a resource that can be utilized virtually anywhere in
the solar system.
Solar power is also rapidly becoming the most cost
effective source of electricity in many major cities,
even without the subsidies many governments offer. It is
not susceptible to price fluctuations due to supply and
demand, and is easier to implement and less apt to
breakage than traditional pipelines or electrical grids.
It is one of the few renewable options that has
virtually no adverse side effects, aside from
installation cost.
Published by Carol Foss - in the hope that it will make
a difference, however small. |
