Wind Energy Collectors
Wind Energy Collectors
Wind Energy Collectors
Wind Energy
Wind is a form of solar energy. Winds are caused by the
uneven heating of the atmosphere by the sun, the irregularities
of the earth's surface and rotation of the earth. Wind flow
patterns are modified by the earth's terrain, bodies of water,
and vegetative cover. This wind flow, or motion energy, when
"harvested" by modern wind turbines, can be used to
generate electricity. The machine which converts the kinetic
energy of the wind into mechanical / electrical energy is called
as wind turbine.
Wind Turbine
Wind turbines, like aircraft propeller blades, turn in the
moving air and power an electric generator that supplies an
electric current. Simply stated, a wind turbine is the opposite of
a fan. Instead of using electricity to make wind, like a fan, wind
turbines use wind to make electricity. The wind turns the
blades, which spin a shaft, which connects to a generator and
makes electricity.
Horizontal-Axis HAWT
Horizontal-axis wind turbines (HAWT) have the main rotor
shaft and electrical generator at the top of a tower, and must
be pointed into the wind.
Tower produces turbulence behind it, hence the turbine
must be fixed upwind of the flow
Downwind turbines are built because they eliminate the
need for a mechanism to keep the turbine in line with upwind
Turbines used in wind farms for commercial production of
electric power are usually three-bladed and pointed into the
wind by computer-controlled motors.
All turbines are equipped with protective features to avoid
damage at high wind speeds, by feathering the blades into the
wind which ceases their rotation, supplemented by brakes.
Vertical-Axis VAWT
Vertical-axis wind turbines (or VAWTs) have the main rotor
shaft arranged vertically.
One advantage of this arrangement is that the turbine
does not need to be pointed into the wind to be effective, which
is an advantage on a site where the wind direction is highly
variable.
1
KE= mv 2
2
1
P= mv 2
2
dm
=Av
dt
1
3
P= Av
2
T
the turbine to the total contained in the wind resource C p = P
1
3
PT = Av c p
2
Cp=
16
27
i.e. 59 %
10 m (33 ft)
Wind Power
Speed(b) m/s
2
Density (W/m )
(mph)
50 m (164 ft)
Wind Power
Speed(b) m/s
2
Density (W/m )
(mph)
0
100
0
4.4 (9.8)
0
200
0
5.6 (12.5)
150
5.1 (11.5)
300
6.4 (14.3)
200
5.6 (12.5)
400
7.0 (15.7)
250
6.0 (13.4)
500
7.5 (16.8)
300
6.4 (14.3)
600
8.0 (17.9)
400
7.0 (15.7)
800
8.8 (19.7)
1000
9.4 (21.1)
2000
11.9 (26.6)
2
3
4
5
6
7
Class
Turbulence
IA
10
18%
IB
10
16%
IIA
8.5
18%
IIB
8.5
16%
IIIA
7.5
18%
IIIB
7.5
16%
IVA
18%
IVB
16%