The piezoelectric strips allow the flag to generate power through movement, whilst the photovoltaics is the best known method of harnessing electric power by using solar cells.
The flag can remote remote sensors and small-scale portable electronics used for environmental sensing such as to monitor pollution, sound levels and heatusing a “deploy-and-forget” strategy in smart cities.
“Under the action of the wind, the flags we built bend from side to side in a repetitive fashion, also known as Limit-Cycle Oscillations. This makes them perfectly suited for uniform power generation from the deformation of piezoelectric materials. Simultaneously, the solar panels bring a double benefit: they act as a destabilizing mass which triggers the onset of flapping motions at lower wind speeds, and of course are able to generate electricity from the ambient light,” said lead researcher Jorge Silva-Leon, from Manchester’s School of Mechanical, Aerospace & Civil Engineering
Dr Andrea Cioncolini added: “Wind and solar energies typically have intermittencies that tend to compensate each other. The sun does not usually shine during stormy conditions, whereas calm days with little wind are usually associated with shiny sun. This makes wind and solar energies particularly well suited for simultaneous harvesting, with a view at compensating their intermittency.”
The team used and developed unique research techniques such as fast video-imaging and object tracking with advanced data-analysis to prove their flags worked. Flags were tested in wind speeds varying from 0 m/s (calm) to about 26 m/s (storm/whole gale) and 1.8 kLux constant light exposure, simulating a wide range of environmental conditions. Under these operation conditions, total power outputs of up to 3-4 mW/cm3 were generated.
“Our piezo/solar inverted flags were capable of generating sufficient power for a range of low power sensors and electronics that operate in the micro-Watt to milli-Watt power range within a number of potential practical applications in avionics, land and sea remote locations, and smart cities. We hope to develop the concept further in order to support more power-demanding applications such as an eco-energy generating charging-station for mobile devices,” said fellow researcher Dr Mostafa Nabawy.