Tile walkways may help reduce carbon footprint

Tiles may help shrink carbon footprint by harnessing pedestrian power This summer at the largest urban mall in Europe, visitors may notice something different at their feet. Twenty bright green rubber tiles will adorn one of the outdoor walkways at the Westfield Stratford City Mall, which abuts the new Olympic stadium in east London.
The squares aren't just ornamental. They are designed to collect the kinetic energy created by the estimated 40 million pedestrians who will use that walkway in a year, generating several hundred kilowatt-hours of electricity from their footsteps. That's enough to power half the mall's outdoor lighting.
The slabs are produced by Pavegen Systems, a London startup launched in 2009 by Laurence Kemball-Cook, a fresh-faced, 26-year-old Londoner who developed his clean energy idea while earning a degree in industrial design and technology at Loughborough University. The 17.7-by-23.6-inch (45-by-60-centimeter) tiles are designed to be used wherever pedestrians congregate en masse: transportation hubs such as train, subway, and bus stations; airports; schools; malls; bustling shopping avenues. The power generated from millions of footfalls can be used to operate a range of low-power applications, including lighting, signs, digital ads, and Wi-Fi zones.
Nearly 30 permanent and temporary Pavegen projects have been installed in the U.K. and Europe. For two years now, four of its tiles have lined a hallway at the Simon Langton Grammar School for Boys near Canterbury, capturing energy from footfalls of its 1,100 students to keep the corridor lit. Pavegen has also harnessed music festival attendees' foot-stamping to charge cell phones and power LED lights.
But higher profile gigs loom. Pavegen has partnered with Siemens, the German technology company, to install five tiles in Federation Square in Melbourne, Australia, to power lighting there. And large, sponsored installations are planned for a major London train station and an Athens shopping mall this summer. Interest in the technology is also growing in the United States. Several American schools are planning to install Pavegen tiles, and Kemball-Cook says federal government agencies have expressed an interest in the technology as well.
People Power
Kemball-Cook got the idea for the slabs while working for a power company as part of his Loughborough studies. He was tasked with looking into solar and wind energy technologies for cities, but concluded that neither technology was suitable for urban areas. That's when it hit him that it would be better to take advantage of people-generated power.
In 2009, he showed a prototype at a design and tech show and received a lot of media attention, which prompted him to launch the company. An early investment of about £500,000 ($800,000) came from family, friends, and the investment bank Renaissance Capital Partners. Pavegen has since gotten additional funding from London Business Angels, an investment network.
Once a Pavegen tile converts energy to electricity, 5 percent of it is used to light the round LED-lighted logo in the center of each tile. The other 95 percent is either directly fed to the application or stored in a battery for later use. Pavegen is also working on a new system that will feed the power directly into a grid. The tiles are completely waterproof, so they can endure rain, snow, and ice. Mechanical testing of the tiles to destruction proved that they would last at least five years, but Kemball-Cook said ideally they would survive for 20.
Pavegen's tiles are designed to have a minimal carbon footprint. All of the rubber comes from recycled truck tires, and about 80 percent of the polymers used for the other components can be recycled. On average, one footstep generates 7 watts of electricity, though the amount varies depending on a person's weight. Each step pushes the rubber down a mere 5 millimeters, or a fraction of an inch. The difference underfoot is "pretty much imperceptible to users," Kemball-Cook said.
Old Concept, New Applications
The harvesting of energy produced from footfalls is not a new idea. Other companies, such as the Netherlands-based Sustainable Dance Club and POWERleap in Michigan, make similar products using piezoelectric materials. First discovered in the 1880s by Pierre and Jacques Curie, piezoelectricity is generated when certain crystals, such as quartz, topaz, and cane sugar, are squeezed or otherwise put under stress. It is the basis of sonar technology, quartz watches, and some sensors, including those for safety airbags in cars.
Kemball-Cook considers Pavegen's technology to be proprietary information, so he won't say whether his tiles rely on piezoelectricity, or describe in detail how they work. It's a hybrid technology, he said, "and there's nothing else like it." That's why he also boasts that his tiles are 200 times more efficient at producing power than any rival product. While this claim can't be verified, Pavegen tiles have impressed judges at several competitions. The company has won a slew of accolades, including being a finalist for the Shell* LiveWIRE Grand Ideas Award last year, and an Observer Ethical Award in 2011.
The tiles have also impressed Matthew Baxter, the head teacher (principal) at Langton Grammar—Kemball-Cook's alma mater—who said his 1,100 "boisterous boys" have truly put them to a punishing test over the past two years. "They've taken a pummeling, but they're fine." While initially a novelty that students delighted in jumping on, the slabs have since become a normal part of the school—albeit one that's encouraged the boys to think about clean energy. "They've sparked an interest in sustainable technology in a number of our students," Baxter said.
High costs are a hurdle, however. Like a lot of green technologies, early iterations of Pavegen tiles weren't cheap. Kemball-Cook said the price of the tiles has dropped 70 percent in the past year, but he was not willing to publicly divulge the current price because it's changing so rapidly. As production ramps up—Pavegen has partnered with a manufacturer near Brighton, England, and is looking to add production partners elsewhere in Europe—and economies of scale kick in, Kemball-Cook is convinced he can get the price down to $50 a tile.
Pavegen is initially targeting low-power applications, but Kemball-Cook envisions larger installations that could handle greater power demands. For instance, he said, there's no reason why the tiles couldn't power an entire music festival, heavy-duty amps and all. Ultimately, Kemball-Cook wants to see thousands of Pavegen tiles permanently embedded in urban areas worldwide, turning cities into power plants.
"That's my dream," he said. He hopes to accomplish it one step at a time.
*Shell is sponsor of the Great Energy Challenge initiative. National Geographic retains autonomy over content.