Piezoelectrics, the future-proof human dynamo

It’s all kicking off! The atmosphere is electric since the footballers are such bright sparks. At the new stadium in the favela of Morro da Mineira, Rio de Janeiro, it’s the players who produce the energy to power the six LED floodlights for night-time matches – just by running around. “I thought we were inaugurating another artificial pitch, but I didn’t expect that this field could produce energy,” says the legendary Pelé, who came to open the pitch. How is it done? Two hundred tiles fitted under the turf capture the energy generated by the pressure of footsteps and transform it into electrical energy.Pedestrians in Saint-Omer recharge a battery which supplies two street lights, without even noticing.This technology, which British company Pavegen has been developing since 2009, is a based on the principle of piezoelectricity, which creates electric charges by applying mechanical stress to certain solid materials. The direct piezoelectric effect was first demonstrated by Pierre and Jacques Curie in 1880. Since then, the effect has been applied in many ways, both in industry and everyday life, from gas lighters to quartz watches, including sensors which are highly valuable to the automotive and aerospace industries. Pavegen tiles are already on the ground in a school in Kent and in several streets, as well as at Heathrow Airport’s Terminal 3 and the pavement outside the French railway station Saint-Omer, in Pas-de-Calais. Pedestrians recharge a battery which supplies two street lights, without even noticing.The price of 10,000 euros per square metre installed remains a barrier. In Brazil, the players themselves are financing the lighting, as well as generating it. They are charged for using the stadium, at around 18 euros per team per hour during the week.The eternal energy of rockIn a football stadium, supporters shout and sing. This represents a wealth of energy which could be harnessed, for example to recharge phones. Once again, a material emitting a piezoelectric current would be used – in this case zinc oxide. Last year, researchers in the UK created a photovoltaic cell which also detected sound waves. The yield of the photovoltaic cell increased by up to 40 per cent. Clearly, rock and pop are two types of music which are full of energy.Two researchers from Queen Mary University of London, in partnership with Nokia, extended their work to create an energy-harvesting device (a nanogenerator) capable of generating electricity from everyday background noise – such as traffic, music, and our own voices. Their prototype can generate five volts, which in theory is enough to charge a phone. But it is not currently sufficient to do away with conventional chargers altogether.Save every single pulse of energyHere’s one last application of piezoelectricity to get your teeth into. Researchers at the École de Technologie Supérieure in Montreal, Canada, suggest that in the course of an ordinary day, jaw movements can produce up to seven milliwatts. They’ve created a chin strap to harvest this energy. The strap is placed under the chin, and comprises piezoelectric fibre composite layers incorporating electrodes into an adhesive polymer matrix, which reacts to chewing. The amount of electricity recovered is not currently sufficient for use in traditional applications. However, once the model is optimized, researchers believe it could power electronic implants or portable electronic devices such as hearing aids and cochlear implants.Equally promising is Korean research on the same principle, which recently produced a prototype piezoelectric nanogenerator capable of powering a heart pacemaker using the movements of the muscles to which it was connected.To go furtherGenerating power through music
The spread of solar ivy across our walls
Pavegen’s website

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