1. SYSTEMCONCEPT 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 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. 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. Fig 2: Node System diagram. 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. Fig 4: The demonstrator [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. Fig 3: Wind Generator – cross-section and actual. THE FINISHED DEMONSTRATOR 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. 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. WIND HARVESTER 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. Fig 5: Estimated duty cycle of the system. CONCLUSION CHARGE RATE Presented at Eurosensors 2012, Krakow