Energy from Fluttering Flag

Harvesting energy from Fluttering Flag

Piezoelectricity is the property of the materials to produce charge (or voltage) when stimulated by a mechanical strain. The all-pervasive vibrations existing in the surroundings from various machines are traditional source strain which can be converted to energy through these Piezoelectric crystals. However, the uninhabited places like high mountains, hills, seashores where the human involvement is least, conventional approach fails due to absence of such vibration sources. These uninhabited places also need continuous environmental monitoring, surveillance monitoring, weather monitoring through small scale devices which consumes electricity. Battery is a good option; however, the regular charging of heavy batteries has led the researchers to search for self-powering alternatives. Also, the replacement of them is a tedious task. Under such situations, wind and solar are the only source of scavenging energy. Huge power stations of wind and solar have long been exploited in past years through large scale devices; however, for powering low-power small electronic devices, inventing novel strategy is the need of the hour. Additionally, large wind turbines work only when the wind velocity is more the 4 m/s and solar works only in day time. In order to address this issue, Dr. Palani’s and Dr. Vipul Singh’s Research group at IIT Indore have fabricated small-scale flag based piezoelectric energy harvesting devices which can be powered by the wind at low velocity. The need to regulate the usage of lead-based piezoelectric, there is a need to replace it with highly biocompatible and high performance devices. Also, the implementation of such energy harvesting devices in real time requires them to be of low impedance. Hence, it was a need of the hour to enhance the piezoelectric output of semiconductors like ZnO by the concept of doping and interfacial modifications, which might replace the lead-based materials To achieve high-productivity of such devices, improving flexibility and inducing flow instability are some of the critical parameters. The researchers at IIT Indore have fabricated an ultra-flexible lead-free piezoelectric device using bio-compatible material. The knowledge of aerodynamics of flow around the structure can be of significant advantage to increase the fluttering capacity. These forces are not desirable for structures like bridges and towers conversely we use these forces for the development of efficient energy source. The detaching of discrete vortices behind a bluff-body immersed in the stream is known to generate transverse periodic forces on the structure. The piezoe

lectric output is directly proportional to the strain produced. Hence, it is desired to use flexible substrates behind a bluff-body to achieve more output. The fabricated ultra-flexible flag based flutter piezoelectric composite device has been tested under three different flow regimes. The flow regime (2.8-3.8 m/s) was categorized as light breeze under the Beaufort scale which makes it advantageous to use in the place where windmill becomes inefficient. Hence, this technology can become complementary to existing technology for powering small scale devices. Additionally, it has been shown that flag based composite device can work as selfpowered wind velocity sensors. The device has also proved to function as the wind direction sensor. Finally, the device stability was ascertained for more than 4500 cycles and found to be extremely stable. This confirms that this flag fabricated by this technology will be an efficient energy harvester.