If you're concerned about moving civilization away from its dependence on climate-altering fossil fuels to generate electricity, you may be putting solar panels on our roofs, or by putting wind turbines on land. But there's another source of alternative energy that you may have overlooked — maybe you should be putting some shoes on your feet and taking to the street.
A British company called Pavegen is working to use pedestrians as a source of current, installing special tiles in public places. These tiles harvest the energy generated by the pressure of footsteps and use it to generate tiny amounts of electricity. But a lot of tiny from thousands of pedestrians can add up to something big.
"Pavegen aims to form an integral part of urban infrastructure powering our future smart cities, situated in high-footfall transport and retail hubs, as well as public spaces," the company said in an email. Pavegen was founded in 2009 by industrial engineer Laurence Kemball-Cook, whose previous job at a European energy company had him examine renewable electrical sources such as solar and wind.
But as Kemball-Cook explained in a 2012 TED talk in Rio de Janeiro, both of those sources have limitations: "When the sun's not shining, there's no power. And with wind, when there's no wind, there's no power. So I thought, what if there was a power source that's all around us that's literally under our feet ... when and where you need it, as an off-grid power source?" (Watch the entirety of the talk below.)
Kemball-Cool turned to something called piezoelectricity, which actually is an idea that's been around since the late Victorian era. Back in 1880, French scientists Pierre and Jacques Curie, who also happened to be brothers, discovered that when they compressed certain sorts of crystals — including quartz, tourmaline and Rochelle salt — they were able to produce voltage on the surface. That phenomenon was first put to practical use in the 1920s, when vibrations from sound were used to generate electrical current from quartz crystals in radio transmitters.
Pavegen invented a piezoelectric paving tile that harvests energy from people who walk over it — about seven watts from each footstep, which is roughly the power level that an iPhone over the 45 minutes to an hour that it takes to charge. That may not sound like a lot of juice, but if you put enough of the tiles in a public place with a lot of foot traffic, it adds up.
The company says its technology has been installed in over 100 locations in 30 countries, including train stations, shopping centers and airports. At the Saint-Omer subway station in northern France, for example, each day about 5,000 pedestrians walk over Pavegen's 7-by-24-inch (18-by-61-centimeter) tiles, which depress about five millimeters from the pressure of each step. The electricity generated by that movement is transferred to small batteries, which can store it for up to 72 hours. Ultimately, it's used to power an LED bench lighting system and USB ports that enable commuters to charge their mobile devices as they wait for trains.
In Washington, DC, there are plans to install a Pavegen's technology on a small park throughway in the city's Dupont Circle neighborhood, a heavy-traffic area for pedestrians. ZGF Architects, the park's designer, estimates that 30,000 people will pass over the tiles in the course of a typical day, generating about 1.25 kilowatt hours of electricity each day. (Granted, that's a relatively tiny amount of electricity--about enough to power a conventional 100-watt light bulb for 10 hours — but it's just a demonstration project.)
Pavegen has bigger plans. "Further along our product pipeline we are currently developing Roadgen, a concept that incorporates the Pavegen technology within roads," the company says. "This way we will have the ability to generate electricity from the impact of vehicles."