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today. For the home generator, batteries can be used to store the power; however,
this increases costs and reduces the environmental benefits. A solution is to use
the electric grid as a “storage” mechanism. During times when the turbine is pro-
ducing excess capacity, the electric company purchases your power. During times
when you need more power than you can produce, you can “buy back” the power
you sold.
13.5.14 Wind and the Environment
In the 1970s, oil shortages pushed the development of alternative energy sources. In
the 1990s, the push came from a renewed concern for the environment in response
to scientific studies indicating potential changes to the global climate, if the use of
fossil fuels continues to increase.
Wind energy is an economical power resource in many areas of the world. Wind
is a clean fuel; wind farms produce no air or water pollution because no fuel is
burned. Growing concern about emissions from fossil fuel generation, increased
government support, and higher costs for fossil fuels (especially natural gas and
coal) have helped wind power capacity in the United States grow substantially over
the last 10 years.
The most serious environmental drawbacks to wind machines may be their nega-
tive effect on wild bird populations and the visual impact on the landscape. To some,
the glistening blades of windmills on the horizon are an eyesore; to others, they're a
beautiful alternative to conventional power plants.
13.5.15 Sample Work Out Problems
Example 13.4
In an area, the average wind speed at the turbine level is 20 km/h. The area swept
by the rotating blades of the wind turbine is 0.5 m
2
. Determine the wind power to
be generated from the turbine.
Solution
We know, mechanical power from wind turbine,
P
w
=
AV
3
E
T
1
/
2
ρ
Given,
V
=
20 km/h = 5.56 m/s
0.5 m
2
Assuming, air density,
A
=
1.2 kg/m
3
Assuming efficiency of the turbine,
E
T
=
ρ
=
55%
=
0.55
Putting the values in above equation,
P
w
=
28.29 W (Ans.)
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