Main presentation title goes here.

1
Practical Implementation of a Novel Wind Energy
Harvesting Network N.R. Harris, D. Zhu, S.P.
Beeby, J. Tudor, N. Grabham and N.M. White School
of Electronics and Computer Science, University
of Southampton, UK
INTRODUCTION This poster describes a
demonstration wireless sensor network consisting
of 24 self-powered nodes that harvest energy from
airflow, utilizing a novel wind energy harvester.
Although the main application for the technology
is for fitting to ducted air systems for building
health monitoring applications, this demonstrator
showcases the various technologies in a more
direct manner, by using energy harvested
throughout the day in intensive periods of high
power operation, (as sensor networks would), in
this case by lighting LEDs. This provides a
visible and dynamic introduction to the nature of
wireless networks and makes it easy to see the
operation of the network. Further, we can report
on the long term testing of this network, as it
has been running continuously for over a year.
SYSTEM
CONCEPT

• 24 nodes are configured in a wind duct with
  airflow from top to bottom. A PC controlled
  base-station sends timing and lighting messages
  to the nodes at specified intervals. The nodes
  are self starting and self synchronising.
• Fig 1. Display Concept
• At set times, the nodes will activate and light
  their LEDS, using up energy they have previously
  harvested during times of electrical inactivity.

The node is based on a Chipcon CC2430 system on a
chip, with an integral IEEE802.15.4 transceiver.
An external Real Time Clock is used for
synchronising and wake-up events. Harvested
energy is stored in 2 super capacitors with a
capacity of 3.6F. A bootstrapping configuration
allows the system to operate with input voltages
down to 0.3V, allowing 89 of the full capacity
of the capacitors to be used.
Fig 2 Node System diagram.
WIND HARVESTER
The wind harvester is based on an oscillating
beam design, with a stationary coil and a moving
magnet 1. Operation is possible for windspeeds
between 2 and 6 m/s. The airflow must remain
laminar for this type of generator. The picture
shows a moving generator with the LED lit. The
electronics are housed in the bluff body. For
successful operation of this generator it is
necessary to design the input impedance of the
electronics to match the desired range of
operating speeds, as electrical damping can
significantly affect the operating
characteristics.
THE FINISHED DEMONSTRATOR
Fig 3 Wind Generator cross-section and actual.
CHARGE RATE
CONCLUSION
This poster highlights the development of a
novel wind harvester and illustrates its
operation in a self powered autonomous network by
demonstrating its active operation by a visual
display. Of interest is the long term performance
of such systems, and this demonstrator has been
operating continuously for over a year with 24
nodes and has shown no failures yet. Future work
will develop the generator for autonomous
operation within building health applications,
such as air-conditioning duct monitoring.
Fig 5 Estimated duty cycle of the system.
Fig 4 The demonstrator
The generator is capable of charging the system
whilst powered up for windspeeds in excess of
3m/s. Charging is possible for speeds down to
2m/s. The system turns on for voltages above 1.8V
and will stay on until the input drops below
0.3V. The stored voltage is electrically limited
to 2.7V.
The array of generators are mounted in a custom
made wind duct (height about 2m) for display
purposes. The LEDs are visible as green dots.
1 Zhu, D, Beeby, S, Tudor, J, White, N and
Harris, N A Novel Miniature Wind Generator for
Wireless Sensing Applications. IEEE Sensors 2010,
Waikoloa, Hawaii, USA, 01 - 04 Nov 2010.
Presented at Eurosensors 2012, Krakow