Civil Engineering Reference
In-Depth Information
12.3
Wind Power
Wind can be generated as a result of uneven heated earth surfaces, locations pressure
differences and earth rotation. Wind turbines can be utilized to receive the kinetic
energy of the wind and transform it to clean renewable electricity by employing
electricity generators. Generally wind turbines are either horizontal axis or vertical
axis type, where the earlier type with two or three blades is the most popular one.
Wind turbines are made of combination of turbine, gear set, generator, and control-
lers that are installed on top of a tall (around 100 ft above ground) tower. As wind
moves through the aerodynamically designed blades of the turbine, generates two
different pressure regions in front and back of the blades. This differential pressure
causes the blades to rotate. Low rounds per minutes (rpm) rotation of the blades
through the blades shaft and the gear set will be converted to a rotation with high
rpm. This resultant fast rotation then will be delivered to a generator which as a
result generates electricity.
The main difference between a horizontal and a vertical axis turbines is that the
fi rst one needs to be directed toward the wind, but the latter one does not need to be
located towards the wind, but is much slower and requires much higher torque to
operate. Due to considerable slow rotation of vertical axis turbines they are gener-
ally not suitable for electricity generation.
Smaller scale wind turbines can be used for residential buildings which mostly can
produce only 0.3-10 kW. These wind turbines can be installed either on top of the
roof, or somewhere on the building site that can catch the available wind at the site.
12.4
Biomass, Biofuel, and Bio-Power
12.4.1
Biomass
During the day plants and vegetables use Carbon Dioxide (CO
2
) which is in the air
along with water and of course sun energy through the photosynthesis process to
create some sort of sugar inside them that helps them to grow. By-product of this
function is generation of O
2
which is deposited back to the air, and will be inhaled
by humans and animals and of course plants and vegetables during the night time.
The respiration system of humans and animals and plant and vegetables over the
night hours uses the inhaled O
2
and returns CO
2
to the air through their exhale func-
tion. When humans and animals consume plants and vegetables carbon moves from
plants and vegetables to humans and animals bodies. That helps them to grow as
well. Human and animal waste also adds carbon to this process of carbon exchange
which is called carbon cycle.
Carbon existed in long time dead body of humans, animals, and plants and veg-
etables which is buried under the layers of earth, if is deep enough and if stays there
for a long period of time (million years) will be changed to diamond, coal or other
