| Renewable
Energy |
| What
is Renewable Energy ? |
| Renewable
energy is the energy obtained from the nature sources
and is essentially inexhaustible. Renewable energy
is also called ¡§clean energy or green
energy because it does not pollute the environment.
Examples of renewable energy are solar energy, wind
power, hydro power, biomass energy and geothermal
energy. |
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| Solar
Energy |
Solar energy is a powerful source of energy which
comes directly from the sun. It can be used in three
different ways: heat source, energy source and solar
furnace.
Human has been using the sun as a heating source
for hundreds of years. This can be demonstrated
by the traditional Chinese building ¡V Central
Courtyard (¥|¦X°|) which was designed
to expose to most sunlight during the cold winter
months. Today, solar collectors are used for heating
water and air in families by using big shiny panels
on the roofs. |
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Solar Cooker (The Solarserver, 2005)
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Series of Solar Panel (California Weather and
Earth Science ¡V LLC, 2004)
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The use of sun as an
energy source has become more commonly used since
the past few decades. The process transfers solar
energy to electricity called photovoltaics, which
is performed by ¡§photovoltaic cells¡¨
or ¡§photoelectric cells¡¨.
Common examples are solar-powered watch or calculator.
Solar furnace is use a huge array of mirrors
to concentrate the sun¡¦s energy
into a small space and produce very high temperatures.
One of the solar furnaces located at Odellio,
France used for scientific experiments can achieve
temperatures up to 33,000 degrees Celsius (Darvill,
2005). |
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| Wind
Power |
When the
sun heats the atmosphere unevenly, some patches
become warmer than the others. The air in warm patches
rise and the cool air from the surrounding areas
blow in to replace them, and wind is formed.
The use of wind energy can be found in hundreds
of years ago, evidence showed that Babylonians and
Chinese were using wind power to pump water for
crop irrigation 4,000 years ago, and sailing boats
were around long before that (Darvill, 2005). Nowadays,
windmills are modified into wind turbines which
can use the wind¡¦s energy to generate
electricity. |
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| A part of a 5-mile line of
wind turbines sprawled acrossed the California skyline
(Daly, 2004). |
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| Wind turbine
works when wind blows the propeller round and turns
the generator to produce electricity. It is very
obvious that the more wind turbines, the stronger
the wind and the larger the propellers, the more
electricity can be generated. In order to allow
wind turbines to produce most electricity, it is
only worth building windmills in places where strong
and steady winds are usually found. |
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| Hydro Power |
Hydro
power is the energy created by flowing water which
has been captured and turned into electricity. Hydro
power is also called ¡§hydroelectric
power¡¨.
Human has been using hydro power for over 2,000
years. Ancient Egyptians used water wheels for grinding
grain. The ever greatest hydro power project in
the Asia would be the Three Gorges Project (ªø¦¿¤T®l¤uµ{)
in the China, which has been completed in June 2003.
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The
Three Gorges (New Three Gorges, 2005) |
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| Nowadays,
the most common type of hydro power plant uses a
dam on a river to trap water in a reservoir or a
valley where there is an existing lake. Water released
from the reservoir flows through a turbine and spins
it, hence generate electricity. |
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| Biomass
Energy |
Biomass
energy is also called bioenergy, which uses natural
materials like trees and plants or even rubbish
to make electricity.
The use of biomass energy can be found thousands
of years ago, since people started burning wood
log for warm and to cook food. Until today, wood
is still the largest biomass energy resource. Other
sources of biomass such as paper, corn stalk, sugar
cane, plants, organic component of municipal and
industrial wastes, |
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| Geothermal Energy |
Geothermal
energy is to use the heat from the center of the
earth to produce energy. Direct use of geothermal
energy dates back thousands of years, when people
began using hot springs for bathing and cooking
food. Nowadays some Australians and New Zealanders
are still using geothermal energy for cooking and
bathing.
In a modern direct-use of geothermal energy system,
a well is drilled into a geothermal reservoir to
provide a steady stream of hot water. The water
is brought up through the well, and a mechanical
system delivers the heat directly for its intended
use. The system is acts like a heat exchange process.
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