Environmental Engineering Reference
In-Depth Information
Harvested Electrical Power (µW) vs. Load Resistance (kΩ)
250
T = 5 K
T = 7 K
Maximum Power
Points (MPPs)
T
= 10 K
200
150
100
50
0 0
50
82 kΩ
Load Resistance (kΩ)
100
150
200
FIGURE 3.4
P-V curves of a thermoelectric generator at different thermal gradients.
Figure 3.4 shows that when the load resistance matches the source resistance
of the thermal energy harvester of 82 k
, the harvested power is always
maximum for different temperature differences. However, for other loading
conditions, shifting away from the internal resistance of the thermal energy
harvester, either very light or heavy electrical loads, the electrical output
power being generated by the generator drops significantly. This exhibits
that the MPPT technique based on resistor emulation is a possible option
to assist the small-scale TEH system to achieve maximum power harvesting
from the thermal energy harvester.
3.2 Resistor Emulation-Based Maximum Power Point Tracker
Resistor emulation techniques have been widely used in the impedance-
matching applications [69-71]. For instance, Paing et al. [70] successfully
demonstrated the resistor emulation approach in energy harvesting from
variable low-power radiative radio-frequency (RF) sources. Khouzam and
Khouzam [69] have also discussed the resistor emulation concept used in
their direct-coupling approach for optimum impedance matching between
the energy harvester and its load by carefully selecting the harvester's rated
parameters with respect to the load parameters. However, very limited re-
search works can be found in the literature that discuss the design and imple-
mentation of resistance emulation techniques and their approximation for a
small-scale TEH system to achieve resistor emulation-based MPPT.
In this chapter, the proposed MPP tracker uses a power converter as an
open-loop resistance emulator to naturally track the MPP of the thermal
 
Search WWH ::




Custom Search