Environmental Engineering Reference
In-Depth Information
Nominal Daily Wind Speed
7
6
5
4
3
2
1
1
3579 1
Month of June
13
15
17
19
21
23
25
27
29 30
FIGURE 2.2
Nominal monthly wind speed in a typical deployment location over a period of 30 days in 2006.
blade radius of 3 cm directly coupled to a single-phase AC generator with a
volumetric size of 1 cm
3
. The process starts with quantifying the wind power
P
wind
using the relationship between the input wind speed
v
in metres/second
and the output power available in wind
P
wind
in watts expressed as [72]
1
2
Av
3
P
wind
=
(2.1)
where
A
is the given wind front contact area in square metres. Using the
nominal daily wind speed recorded throughout the month in a sample re-
mote area environment as shown in
Figure 2.2
[73], the average wind speed
throughout the month is calculated to be around 3.62 m/s. Based on the
Beaufort scale, the calculated average wind speed is termed as fairly light,
which is equivalent to a gentle breeze, and the amount of energy available
in the wind for harnessing is therefore quite limited. Under gentle breeze
conditions, the power available from the wind is computed based on
Equa-
tion 2.1
to be 82 mW. As can be seen in
Figure 2.2
, the fluctuation in wind speed
is quite significant; wind speed can go as high as 6 to 7 m/s and resides at a
low wind speed of around 2 m/s for many days. This high fluctuation in wind
speed, due to the geographical condition of the sample remote area, requires
the power management circuit to have a wide input operating bandwidth
to be able to cover the minimum as well as maximum harvested electrical
power.
Figure 2.3
is a functional block diagram of the wind turbine generator
system showing the conversion of raw wind power to electrical power, indi-
cating the corresponding power available at different stages, for example, the
raw wind power
P
wind
, the mechanical power
P
T
, and the electrical power
P
elec
. When wind flows past the blades of the wind turbine, some part of
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