Windmill WiFi

12 November 2005 --
http://www.indolink.com/displayArticleS.php?id=111205035839

According to Nature, the world's pre-eminent scientific magazine, Assistant Professor Shashank Priya of the Materials Science and Engineering Program at the University of Texas at Arlington is successfully using pocket-sized mini windmills to power wireless network of sensors in remote locations.

As Dr Priya himself wrote in an article published early this year in the Japan Journal of Applied Physics, "practically, on-site small scale successful harvesting of electrical energy from wind energy can solve various existing challenges and evolve new applications."

Essentially, Priya's challenge was to develop a windmill with a diameter of just 10cm which works by flexing piezoelectric crystals as it rotates, causing them to generate a current. A 'gentle breeze' of 16km/h is enough to generate the 7.5mW necessary to power a small electronic sensor. Such windmills are designed to solve the problem of powering Wi-Fi kit in remote locations. Geologists, for instance, can monitor seismic activity using wireless-enabled sensors located across large geographical areas.

Priya and other Materials Science & Engineering researchers have created two versions of inexpensive generators utilizing wind power. As wind turns a propeller, a cam on the propeller shaft causes flexing in a series of bimorphs that are arranged in circular or stacked patterns. The researchers have created output power of 5 - 50 mW using wind flow of 5 - 10 mph from their crude but inexpensive - less than $20 - prototypes.

Developments by Dr. Priya and his team have been published in the Japanese Journal of Applied Physics. This week they offered further confirmation as well as details in Applied Physics Letters.

Potential uses of the wind-powered generators include powering remote sensing and communications devices. Most research in this area - small-scale energy-on-demand - has centered on expensive generators such as fuel cells and photoelectric or thermoelectric devices.

Since minor vibrations can also create a charge, Dr. Priya foresees piezoelectric bimorphs being utilized to power a variety of small devices, including insulin pumps powered by the vibrations of a beating human heart or portable radios and CD players powered by the vibrations caused by walking, running or riding a bicycle.

The article this week in Nature says wireless networks have freed us from miles of cumbersome wiring needed to carry information, but the electronic 'nodes' of such networks still need power. If geologists want to place hundreds of sensors on a mountain to monitor seismic activity, for example, they either have to supply electricity using cables or hike out to each sensor every six months or so to replace batteries.

"The problem is keeping the nodes powered all the time," says Priya, adding that wind power could be the answer.

Priya says there are four possible ways to address this problem (1) Enhance the energy density of the storage systems (2) reduce the power consumption of the wireless nodes, (3) develop self-powered nodes by generating or scavenging power and (4) develop other novel methods for powering the nodes.

Priya explains: "Out of these various possible solutions the most efficient and practical method is to develop self-powered nodes by scavenging energy from the wasted mechanical vibrational energy. The largest source of vibration energy around us is Wind. Trapping the vibration energy from wind energy to generate electricity at small scale can evolve a new generation of distributed power sources."

Priya's group is already a leader in the piezoelectric energy harvesting technology with various harvester prototypes, “Piezoelectric Windmill” and “AutoPiezo”. His windmill is about 10 centimetres across,and is attached to a rotating cam that flexes a series of piezoelectric crystals as it rotates. Piezoelectric materials generate a current when they are squeezed or stretched, and are commonly used to make a spark in gas lighters. Priya has found that a gentle breeze of 16 kilometres per hour can generate a constant power of 7.5 milliwatts,which is more than enough to keep an electronic sensor running. He unveiled his windmill earlier this year,and has now followed up with precise details of the device's abilities.

Priya has an undergraduate degree from Allahabad University (1996) and a graduate degree from the Indian Institute of Science (2000), Bangalore. He earned his Ph.D. from the University of Pennsylvania in 2003.

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