Researchers create flags that harvest energy from solar and wind

Scientists at the University of Manchester in the UK have developed flags that are reckoned to be the first to harvest solar and wind at the same time. Not enough to power a house, or even a gadget such as a smartphone, but could be enough for set it and forget it remote sensors.

The energy-harvesting device uses an inverted flag setup – where the leading edge is free to move but the trailing edge is secured. The body of the flags is made up of piezoelectric strips that harvest energy as the device flaps around in the wind and flexible photovoltaic cells which capture solar energy.

"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," explained the team's Jorge Silva-Leon, lead author of the study. "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."

To be fair, the flags don't generate very much electricity, but the team believes that the devices could be used to power environmental sensors that monitor such things as air pollution, sound levels and inner city ambient temperature, as well as small portable electronics.

The researchers tested the energy-harvesting flags in calm and gale-force wind speeds with constant light exposure, finding that such operational conditions resulted in power output of up to 3-4 milliwatts. And there is a kind of useful redundancy in the design.

"Wind and solar energies typically have intermittencies that tend to compensate each other," study co-author Dr. Andrea Cioncolini said. "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 hopes to further develop the concept, upping the power output for more demanding applications such as charging stations for mobile devices.

A paper detailing the research has been published in the journal Applied Energy. The video below has more.

Source: University of Manchester

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