Something for nothing always appeals, which is perhaps why there's so much buzz being generated about piezoelectricity at the moment. Piezoelectricity is electricity generated from pressure, and it's used in a wide range of household applications today, from vibrating ink out of a nozzle in inkjet printers, to the ignition of a gas cooker.
It's a tried and tested technology for relatively minor applications but the question is, can it scale? Can we use piezoelectricity to generate free electricity from our movements, powering our phones, laptops or even street lamps as we pass under them?
Piezoelectricity is generated in certain materials -- most commonly quartz -- when they are put under pressure. In these materials an electric charge builds up on the surface as the material is deformed. In simple terms, it's the process that turns kinetic energy (the energy of motion) into electricity. Usually this energy is wasted as heat, but piezoelectric harvesting modules can store the energy for future use.
These modules needn't be huge. Indeed, Dr. Ville Kaajakari of Louisiana Tech University has created a prototype that embeds in the user's shoe. It takes the place of the heel shock absorber, generating enough power to run a small GPS receiver. His team are working on bringing the power levels up to a point where they can run bigger devices such as mobile phones. Although in its current state this tech isn't a very efficient way to generate electricity, it could make a valuable back-up source of power for emergencies.
Feet aren't the only part of the body earmarked as portable generators. Few parts of the body work as hard as the knee joint, so a prototype generator from a team of scientists from the UK at Cranfield University, University of Liverpool and University of Salford have great promise. It clips on the outside of the knee, and what it might lack in style and comfort it makes up for in energy generation -- again, enough to power a GPS tracking system, or to send wireless transmissions.
One of the most ambitious plans mooted for piezoelectricity is to create a back-up power source that could power our roads' street lights and traffic signals by turning gridlock into generators. London-based company Pavegen are one of the pioneers in the field. Their 'smart' pavement tiles were trialled at West Ham stadium during the 2012 Olympics and lined the approach to the finish line of the 2013 Paris marathon. Pavegen says one step on one of its slabs generates enough electricity to power an LED street lamp for 30 seconds.
Such technology is already in the wild -- Toulouse, France, has a small number of street lamps powered by pedestrian traffic, and the lighting in 'eco-discos' -- as seen in London and Rotterdam -- grow ever more psychedelic as revellers stomp on the pressure pads embedded underneath the dance floor.
When further developed, piezoelectricity might provide convenience for tech-savvy youths but it may be the older generations who benefit most acutely from this burgeoning industry. A team at Michigan University has successfully run experiments harnessing energy from simulated heartbeats, and their work could remove the need for stressful and invasive surgeries to replace batteries in pacemakers. Not bad for nothing, we're sure you'll agree.
Image Credit: Ecochunk