Solar Energy

Ever since the dawn of time, the sun has been a resource we cannot live or do
without, so its not such a shock that man has come up with the idea of solar
energy. Solar energy had many uses. Some can be dangerous and some, a very
valuable asset to the modern world. Solar energy is energy derived from the sun
in a form of ultra-violet rays. Its was first applied to use in 212 B.C., by the
Greek genius Archimedes. Solar energy was used to defend the habor of Syracuse
against the Roman fleet. Archimedes used a mirror or “burning mirror” as
they had called it, to set fire to the ships of the Roman fleets while standing
on shore (McDaniels 83). It wasnt until 1615 when Salomon de Caux constructed
the first solar device; a solar engine. His device was made of glass lenses,
supporting frame, and an airtight metal vessel containing water and air. This
produced a small water fountain when the air heated up during operation. This
was considered to be more of a toy than a device, but it was the first published
account of the use of solar energy since the fall of the Roman Empire (Cheremisinoff
1). Some other use of solar energy after that was the solar roof and the solar
oven. The solar roof was thought up by Harold Hay. In a solar roof system, water
is contained in a clear plastic bag and it is placed on a black metal roof. Hay
got the idea while traveling in India on a technical aid mission for the U.S
government. While there, he noticed that many people were living in rusty, sheet
metal shacks, which were hot in the day and cold at night. Hays plan was to
remove the insulation from the roof on winter days so that the roof would get
hot, and Replacing the insulation at night to allow the shack to be warm through
the night. Then in the summer, he would so the reverse of what he did in winter
to let the house cool at night and replacing the insulation in the daytime to
block out the heat. Then over the years, Hay and a man named John Yellott
constructed a 3- by 3.7-m building using water basins as the actual roofing
material. During the summer, a slab of foam insulation was rolled back at night,
and the water would become cold through the night sky evaporation. Since the
water supply sat directly on a metal ceiling, it absorbed the heat from the room
and kept the building air-conditioned all day. During the winter, the movable
insulation was rolled back in the daytime which allowed for it to collect heat.

This generated enough heat into the house through the ceiling at night to keep
the room comfortable (McDaniels 179-181). Then there was the solar cooker.

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Developed by Augustin Mouchot in France and by John Ericsson in the United
States in the nineteenth century. They wanted to develop a solar cooker that not
only reached high temperatures, but also was to be used as a means of heat
storage enabling food to be cooked after sundown. Mouchot built a solar steam
engine that operated a printing press in Paris in 1882. In the United States,
John Ericsson invented what he called the “Ericsson-cycle” which was a
hot-air engine for the making of solar heat. The suns rays would be
concentrated with the use of a parabolic reflector, which was designed to track
the sun across the sky in order to keep a constant power output. (McPhillips
86-89) There was also the solar oven. In 1837, and astronomer from England named
John Fredrick Herschel introduced to the world a solar oven. He built a small
solar oven while on a trip to Africas Cape of Good Hope. He constructed it as
a mahogany, painted it black and buried it in the sand for purposes of
insulation. a doubled-glazed cover, which was the only portion of the oven left
exposed, serve to limit heat losses through the top, while at the same time,
letting in sunlight. The maximum temperature of the oven was of about 240 degree
F and it was used throughout his expedition by him and his staff to cook both
meat and vegetables (Regino 5). Not all solar energy inventions and discoveries
were good. Some solar energy is dangerous. One for example would be lasers.

Laser, an electromagnetic wave that is made up of excited atoms. It produces
coherent light. This means that the light produced is orderly, with all the
excited atoms making up the laser beam that is emitting their flashes in unison.

The laser often consist of polished ruby rod that has a solid mirror at one end,
and a high voltage flash tube wound around the rod. The flash tube acts as the
power source for the laser beam and the energy that is emitted as pulse is
visible light (Holsroemn 12-14). Another dangerous solar energy is Ultra-violet
rays. Ultra-violet rays is also referred to as UV rays for short. They are
energy rays that is given off from the sun. UV rays were first discovered by
astronomers in the 1960s. It can be dangerous because too much rays can cause
you to sun burn, tan, damages your hair, and at the worst; skin cancer. You can
get skin cancer if your are not careful about how to spend and protect yourself
from the sun. One way to protect yourself is by applying sun tan lotion to your
skin every time that you plan on spending a lot of time in the sun, especially
if you are going to the beach. To be on the safe side for sure, you should apply
it everytime you are in the sun. (Rose 123-125). There is basically a lot of
solar powered inventions in our society today. Like in our household, there are
many solar equipment. There is the solar heating, solar satellite, solar water
heating, solar cooling, solar radio, solar battery, etc. As you can see, there
are so many solar items in the world so solar is an important source. (Holstroemn
182). We believe that solar energy is worth it. It is a good thing that our
planet has so many ways of generating energy. We have electricity, solar power,
nuclear power, propane, so many! We think that out of all the choice of energy,
we prefer solar. Why you ask, because think of what will happen when we lose all
of our other source of energy. The sun is always here for us. Solar energy is
the only energy source that can not be controlled. We could lose all of our
electricity and still live because we can live off of solar power. You dont
need electricity or gas to power your stove because when there is a storm, the
power can be knocked out and you wouldnt have to worry if you have furniture
that were powered by solar. Every other power source can be destroyed but the
greatest power of all is the sun. This is one power source that can always be
depended on. The best part about solar energy is that it is free. It can last
forever. In a poll that we had conducted around our neighborhood, we found that
only five percent of the people on our street have solar powered products. This
is very surprising to me. We had expected the average to be somewhat higher.

Mrs. Richard is one of the person who we asked that had solar products such as:
solar battery and solar heating. She believes that everyone should at least give
solar products a try because you can always depend on it when you need it. Other
people like Mr. Pham said that there is no use to solar power because when the
sky is cloudy, there is no sun to power any of the solar product. He prefers to
stick to electricity. People have different ways of looking at solar energy so
its up to them if they want sun energy or electricity. Who knows, maybe one day,
everyone will agree on using solar energy. As for us, we still prefer solar over
electricity any day.

Cheremisinoff, Pual N. Principles & Applications Of Solar Energy. Ann
Arbor Science Publishers: Michigan, 1979. Holstroemn, Isaac R. Energy From The
Sun. Tab Books, Inc: Pennsylvania, 1981. McDaniels, David K. The Sun. John Wiley
& Sons, Inc: Canada, 1984. McPhillips, Martin. The Solar Energy. Everest
House: New Yrok, 1983. Regino, Thomas C. Solar Energy. St. Martins Press,
Inc: New Yrok, 1986. Rose, Harvey. Solar Energy Now. Ann Arbor Science

Solar Energy

About 47 percent of the energy that the sun releases to the earth actually reaches
the ground. About a third is reflected directly back into space by the atmosphere. The
time in which solar energy is available, is also the time we least need it least – daytime.
Because the sun’s energy cannot be stored for use another time, we need to convert the
suns energy into an energy that can be stored.
One possible method of storing solar energy is by heating water that can be
insulated. The water is heated by passing it through hollow panels. Black-coated steal
plates are used because dark colors absorb heat more efficiently.
However, this method only supplies enough energy for activities such as washing
and bathing. The solar panels generate “low grade” heat, that is, they generate low
temperatures for the amount of heat needed in a day. In order to generate “high grade”
heat, intense enough to convert water into high-pressure steam which can then be used to
turn electric generators there must be another method.
The concentrated beams of sunlight are collected in a device called a solar furnace,
which acts on the same principles as a large magnifying glass. The solar furnace takes the
sunlight from a large area and by the use of lenses and mirrors can focus the light into a
very small area. Very elaborate solar furnaces have machines that angle the mirrors and
lenses to the sun all day. This system can provide sizable amounts of electricity and create
extremely high temperatures of over 6000 degrees Fahrenheit.

Solar energy generators are very clean, little waste is emitted from the generators
into the environment. The use of coal, oil and gasoline is a constant drain, economically
and environmentally. Will solar energy be the wave of the future? Could the worlds
requirement of energy be fulfilled by the “powerhouse” of our galaxy – the sun?
Automobiles in the future will probably run on solar energy, and houses will have solar
Solar cells today are mostly made of silicon, one of the most common elements on
Earth. The crystalline silicon solar cell was one of the first types to be developed and it is
still the most common type in use today. They do not pollute the atmosphere and they
leave behind no harmful waste products.

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Photovoltaic cells work effectively even in cloudy weather and unlike solar heaters,
are more efficient at low temperatures. They do their job silently and there are no moving
parts to wear out. It is no wonder that one marvels on how such a device would function.
To understand how a solar cell works, it is necessary to go back to some basic
atomic concepts. In the simplest model of the atom, electrons orbit a central nucleus,
composed of protons and neutrons. Each electron carries one negative charge and each
proton one positive charge. Neutrons carry no charge. Every atom has the same number
of electrons as there are protons, so, on the whole, it is electrically neutral.
The electrons have discrete kinetic energy levels, which increase with the orbital
radius. When atoms bond together to form a solid, the electron energy levels merge into
bands. In electrical conductors, these bands are continuous but in insulators and
semiconductors there is an “energy gap”, in which no electron orbits can exist, between
the inner valence band and outer conduction band Book 1.

Valence electrons help to bind together the atoms in a solid by orbiting 2 adjacent
nuclei, while conduction electrons, being less closely bound to the nuclei, are free to move
in response to an applied voltage or electric field. The fewer conduction electrons there
are, the higher the electrical resistively of the material.

In semiconductors, the materials from which solar sells are made, the energy gap
E.g. is fairly small. Because of this, electrons in the valence band can easily be made to
jump to the conduction band by the injection of energy, either in the form of heat or light
Book 4. This explains why the high resistively of semiconductors decreases as the
temperature is raised or the material illuminated.
The excitation of valence electrons to the conduction band is best accomplished
when the semiconductor is in the crystalline state, i.e. when the atoms are arranged in a
precise geometrical formation or lattice. At room temperature and low illumination,
pure or so-called “intrinsic” semiconductors have a high resistively. But the resistively can
be greatly reduced by


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