Researchers have developed flags that can produce electrical energy using solar and wind power. Flexible photovoltaic cells and piezoelectric strips have been used to create the new solar and wind energy-harvesting flags.
With piezoelectric strips, the flag can produce power through motion; on the other hand, the use of photovoltaics is the best-known technique to harness electric power by using solar cells.
The research, carried out by scientists at the University of Manchester, is the most advanced of its kind so far and the first to yield wind and solar energies at the same time using inverted flags. The study has been reported in the journal Applied Energy.
The newly developed energy-harvesting flags have the ability to enable remote sensors and small-scale portable electronics that can be used for environmental sensing, for example, monitoring sound levels, pollution, and heat.
The research aims to enable cheap and sustainable energy-harvesting solutions that can be installed and left to produce energy with less or no need for maintenance. The approach is called “deploy-and-forget” and this is the projected model that will be adopted by the so-called smart cities when using remote sensors.
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.
Jorge Silva-Leon, Study Lead Author, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester
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.
Dr Andrea Cioncolini, Study Co-Author, Senior Lecturer in Thermal Hydraulics, The University of Manchester
The researchers used and developed unique research approaches like fast video-imaging and object tracking with sophisticated data analysis to establish that their flags worked.
The created harvesters were tested by subjecting them to wind speeds ranging from 0 m/second (calm) to nearly 26 m/second (storm/whole gale) and 1.8 kLux constant light exposure, reproducing a broad variety of environmental conditions. Under these operational conditions, it produced a total power output of up to 3–4 mW.
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.
Dr Mostafa Nabawy, Study Co-Author, The University of Manchester
Dr Alistair Revell, one of the co-authors of the study, underlines present and future research directions, saying: “We are currently making use of a novel computational framework for modeling and simulation developed at The University of Manchester, building on a long tradition of Computational Fluid Dynamics in the group. The use of computers to model fluid-structure interactions is increasingly referred to as virtual engineering, and plays a key part in device development by reducing the number of models which need to be physically manufactured and tested.”