Conclusions and Future Works - Energy Harvesting Autonomous Sensor Systems - page 213

7
Conclusions and Future Works
This chapter concludes the topic; it briefly restates the motivation of the re-
search works recorded in the topic, the identified problem areas, and the
various findings in each problem area. Finally, it shows the direction of future
research in this regard.
7.1 Conclusions
This topic covers work done on design, analysis, and practical implementa-
tion of various optimized energy harvesting (EH) systems for sustaining self-
autonomous wireless sensor nodes. Conventionally, these tiny, smart, and
inexpensive sensor nodes, connected together into a wireless sensor network
(WSN), are powered by alkaline or rechargeable batteries. They are scattered
in the targeted deployment field to facilitate monitoring and controlling of
physical environments from remote locations that are too difficult or dan-
gerous to reach. However, as the coverage area of the WSN becomes larger,
dense with many sensor nodes, problems arise in powering each of these
battery-operated sensor nodes. The onboard batteries of the sensor nodes
have limited energy capacity, so after operating the sensor nodes for some
time the batteries deplete and the sensor nodes go into an idle state. Hence,
the limitation of energy sources for sensor nodes becomes critical, even worse
when one considers the prohibitive cost of providing power through wired
cables to them or replacing batteries. Furthermore, when the sensor nodes
must be extremely small, as tiny as several cubic centimetres, to be conve-
niently placed and used, such small volumetric devices are very limited in
the amount of energy that the batteries can store, and there would be severe
limits imposed on the nodes' lifetime powered by the miniaturized battery
that is meant to last the entire life of the node.
Energy harvesting emerges as a highly potential solution to make a para-
digm shift from battery-operated conventional, the WSN, towards a truly
self-autonomous and sustainable energy harvesting wireless sensor network
(EH-WSN). The main focus of this research is to design and implement EH
systems to resolve the energy supply problems faced by the wireless sensor
nodes. In an EH system, there are generally four main parts: energy harvester
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