Environmental Engineering Reference
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Main : 125 k
10 s/div
∆
T
10 K
15 K
Decreasing ∆
T
from 15 K
10 K
P
/mW
1
R
/Ω
Source Power (
P
in
)
200
0
R
s
Source Resistance (
)
0
V
/
V
Source Voltage (
V
in
)
6
4
I
/mA
Output Voltage (
V
o
)
2
200
0
0
Source Current (
I
in
)
0
10
20
30
40
50
60
70
80
Time/sec
FIGURE 3.7
Operation of a resistor emulation-based MPP tracker under varying temperature differences.
in
Equation 3.10
, the buck converter has been experimentally tested under
varying temperature differences and different loading conditions. First, a
fixed resistance of 10 k
was used as the test load for the operation of a re-
sistor emulation-based MPP tracker under varying temperature differences;
the experimental results are shown in
Figure 3.7
.
Referring to
Figure 3.7
, as the temperature difference
T across the thermal
energy harvester increases from 10 to 15 K, the harvested power
P
in
, which
is the result of the product of the source voltage
V
in
and source current
I
in
,
increases from around 300 to 600
T
is increasing,
resistor emulation MPP tracker to remain steadily at the optimal resistance of
82 k
W. During this time when
.
Based on Seebeck's effect, as the temperature difference across the ther-
mal energy harvester rises from 10 to 15 K, the source voltage increases
from 5 to 7 V, and the step-down voltage
V
o
output from the buck converter
with resistor emulation-based MPP tracker also increases from 1.8 to 2.2 V.
Given that the converter parameters are chosen as
L
=30mH,
f
s
=18kHz,
tained experimentally, as shown in
Figure 3.7
, is verified to be around 82 k
.
The buck converter is able to maintain the thermal energy harvester near
its MPPs for various input operating conditions. Hence, the buck converter
yields good performance as a simple resistor emulation-based MPPT under
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