Environmental Engineering Reference
In-Depth Information
AC Voltage vs. Wind Speed
10
8.8
8
6
4
2
0
0
1
2
3
Wind Speed (m/s)
4
5
6
6.7
7
8
FIGURE 2.40
Open circuit AC voltage over a range of wind speeds.
DC output voltage of 8.8 V is used to power the wireless RF transmitter to
transmit several 12-bit digital signals to the base station in a wireless manner.
Another characterization illustrated by
Figure 2.41
shows the typical output
electrical power characteristic of the piezoelectric wind energy harvester as
a function of the load resistances at different wind speeds. Simply, the figure
shows how much power the piezoelectric wind energy harvester can supply
continuously to the load.
Note that in
Figure 2.41
a constant load resistance of 220 k
results in a
maximum output power over the full range of wind speeds. At a wind speed
of 6.7 m/s and the load resistance fixed at 220 k
,
Figure 2.41
shows that the
maximum amount of output power that can be harvested from one piezoelec-
tric wind energy harvester is around 155
W. If the number of piezoelectric
wind energy harvesters is to be increased, then the amount of power that can
be generated would be a multiple of 155
W. With the present microelectronic
technology, to power the sensor continuously with 155
Wisquite impossi-
ble; hence, an energy storage with some triggering circuit has to be included
in the power management system to ensure that the electric energy stored in
the storage element is sufficient before supplying the power to the RF wireless
transmitter and its associated power management circuit.
2.2.3
Power Processing Units
The harvested power of the piezoelectric wind energy harvester is first fed into
the power processing unit (PPU), and then the regulated output voltage from
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