Introduction - Energy Harvesting Autonomous Sensor Systems - page 32

thermal and electrical analyzes of the TEH mechanism are illustrated.
Since the characteristic of the TEH mechanism is found to be similar to
the WTG, a resistor emulation-based MPPT is developed to naturally
track the MPP of the TEH mechanism with very little control circuit.

A batteryless and wireless remote controller has been developed to
switch electrical appliances such as lights and fans on/off in a wireless
manner. Two types of piezoelectric-based VEH systems are presented
to harvest impact or impulse forces from a human pressing a button
or switch action. Detailed understanding and characterisation of the
performance of the VEH mechanisms are carried out. Since the har-
vested power is lower than the power consumed by the wireless RF
transmitter, an energy management circuit has been implemented.
The harvested energy from the VEH mechanism is first accumulated
and stored in a capacitor until there is sufficient stored energy to
power the RF transmitter; the transmitter is then energized.

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For some WSN applications, multiple energy sources are available.
A hybrid wind and SEH scheme is proposed to extend the lifetime
of the wireless sensor node. In order for the developed hybrid en-
ergy harvesting (HEH) system to harvest simultaneously from both
energy sources, the WEH subsystem uses the resistor emulation tech-
nique while the SEH subsystem uses the constant voltage technique
for MPP operation. In another HEH research work, a hybrid of indoor
ambient light and TEH has been proposed. Energy sources of differ-
ent characteristics are connected directly. A detailed analysis of their
relationship has been conducted to validate that the impedance mis-
match issue does not affect much of the maximum attainable power
from the HEH mechanism. A power management circuit is devel-
oped to condition the combined output power harvested from both
energy sources.

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Like EH, two remote means of charging low-power electronic devices
are proposed. A magnetic inductive approach has been investigated
to transfer electrical power from the power lines to the sensor node
in a wireless manner. Based on the electrical power requirements
of the wireless RF transmitter and the electrical characteristic of the
magnetic energy harvester, a magnetic induction system has been de-
signed and successfully implemented. Another wireless power trans-
fer (WPT) mechanism operating at its magnetic resonance has been
proposed to further extend the distance for wireless power transmis-
sion. Detailed theoretical analysis of the WPT mechanism has been
provided and then verified by the simulation results. Based on the
verified theoretical findings and experimental results, the design of
the WPT mechanism can be optimized for improving the WPT dis-
tance, efficiency, and form factor.

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Various types of EH systems and their respective main components,
namely, energy harvester (source), power management circuit, energy

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