Environmental Engineering Reference
In-Depth Information
Power Curve (Variation of θ
Z
)
160
0°
140
120
30°
100
60°
80
90°
60
40
20
0
0
200
400
Resistance (kΩ)
600
800
1000
FIGURE 2.39
Power generated by the harvester with angles of
.
maximum power output,
L
,
W
, and
Z
should be set at 0
◦
with respect to
the wind flow direction.
Piezoelectric-based wind energy harvester offers several advantages over
the conventional wind turbine harvester. These include instant starting with
no dead time (due to the inertia of the wind turbine generator); small size
and ultralight weight; extremely low magnetic permeability (suitable for use
in high-magnetic-field environments); and almost no heat dissipation. There-
fore, the piezoelectric wind energy harvester is suitable to power the minia-
turized autonomous sensor used in many application areas, such as structural
and automation applications. To study the feasibility of using the piezoelectric
wind energy harvester as a generator to supply power to the power condi-
tioning circuit and the RF transmitter for practical application, some charac-
terizations have been conducted to better understand the capability of the
piezoelectric wind energy harvester. One of the characterization works car-
ried out on the harvester was to determine the relationship between the open
circuit rectified DC voltage and the wind speed as shown in
Figure 2.40
.
Based on the plot in
Figure 2.40
, the DC output voltage of the piezoelec-
tric wind energy harvester can be used to predict the speed of the incoming
wind. For a given wind speed (any wind speed beyond this threshold value
would trigger a 12-bit digital signal to be transmitted to the base station in a
wireless manner), the corresponding preset voltage level for the power man-
agement circuit can be determined from
Figure 2.40
. Take, for instance, at a
wind speed of 6.7 m/s, the DC output voltage of the piezoelectric wind en-
ergy harvester that is measured to be around 8.8 V. If this is the preset wind
speed threshold for sounding the siren at the remote base station, then the
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