They look like flags, but do far more than just blow in the wind and display patriotism. Instead, these flags, developed by researchers at the University of Manchester in the U.K., are designed to generate electrical energy using wind and solar power.
The novel wind and solar energy-harvesting flags were developed as part of a research effort aimed at developing cheap and sustainable energy harvesting solutions that can be deployed and left to generate energy with little or no maintenance. The strategy is known as “deploy-and-forget” and this is the anticipated model that so-called smart cities will adopt when using remote sensors.
The flags use flexible piezoelectric strips and flexible photovoltaic cells. The piezoelectric strips allow the flag to generate power through movement, while the photovoltaic cells harvest solar energy to produce electric power. The scientists envision the energy harvesting flags powering remote sensors and small-scale portable electronics, which can be used for environmental sensing such as to monitor pollution, sound levels, and heat, for example.
Jorge Silva-Leon, from Manchester’s School of Mechanical, Aerospace & Civil Engineering and lead-author of the study, says: “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.”
Dr Andrea Cioncolini, co-author of the study, adds: “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 research techniques such as fast video-imaging and object tracking with advanced data analysis to prove their flags worked. The developed harvesters 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 operating conditions, total power outputs of up to 3 to 4 mW were generated.
Dr Mostafa Nabawy, co-author of the study, says: “Our piezo/solar inverted flags were capable of generating sufficient power for a range of low power sensors and electronics that operate in the microwatt to milliwatt 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.”