Wind Energy Harvesting System - Energy Harvesting Autonomous Sensor Systems - page 37

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Wind Energ y Harvesting System
Like any of the common renewable energy sources, wind energy harvesting
(WEH) has been widely studied and researched for high-power applications
where large wind turbine generators are used for supplying power to re-
mote loads and grid-connected applications [55-56]. However, to my best
knowledge, few research works can be found in the literature that discuss the
issue of small-scale WEH [35, 60], and those are miniature in size and highly
portable to power small autonomous sensors deployed in remote locations
for sensing or even to endure long-term exposure to a hostile environment
such as a forest fire. In addition, energy harvesting from wind, the incoming
wind speed can be sensed to determine the outbreak of a disaster and raise an
emergency warning to people in that area so that they have time to respond to
the emergency situation. Thus, this reduces the number of causalities caused
by the disaster.
In this chapter, two types of small-scale WEH schemes are introduced:
(1) the direct WEH approach using a wind turbine generator in Section 2.1
and (2) the indirect WEH approach using piezoelectric material in Section 2.2.
Several challenges are associated with these types of small-scale WEH systems
in contrast to the large-scale WEH systems, such as:
1. Random wind at the concealed deployment site of small-scale WEH,
rather than regular wind flow in open field, results in an extremely
intermittent and fluctuating wind energy supply.
2. Low wind speeds at low height and concealed ground, in the range of
2to7m/s, as compared to large-scale WEH systems with tall towers
up to 90 m, which are exposed to high wind speeds of greater than 10
m/s, significantly reduce the harvested power by a cube root factor.
3. Weak aerodynamic force is generated with a very small wind front
area of few square inches in comparison to a huge wind turbine,
which further lessens the available wind power for harvesting.
4. A small size, lightweight, and low-cost WEH system is required by
miniaturized ubiquitous wireless sensor nodes instead of a large-
scale WEH system for power generation.
Due to the challenges, the proposed direct and indirect WEH systems have
to be lightweight and small in size, comparable to the miniaturized wireless
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