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We Could Be Doing Something Useful With the Energy Under Our Feet

Some surprisingly not-so-unrealistic plans to capture unused energy all around us.

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Every time you take a step, a tiny bit of energy goes to waste. You raise one leg and plant another. And in the space of that modest footfall, the energy created by your landing sole dissipates beneath you.

"At the moment," says Oliver Schneider, the managing director of London-based architecture and innovation consultancy The Facility, "when you walk along the ground, the energy that you’re giving out actually goes into the ground as vibration through the body, as sound, as friction that wears your shoes out."

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Picture a whole crowd of pedestrians scuffing their soles and stomping to work – maybe on a subway platform, or in food court – and that accumulated footfall starts to look like something that might be useful. The Facility has been working on variations of this notion for a decade, harnessing energy from foot traffic, from cars rolling over roadways, or trains rumbling across railroad tracks. And as long as we’re looking for renewable energy just about anywhere we can find it, why not literally beneath our feet?

The Facility first began to consider this in the context of old, creaking rail infrastructure around London. Most engineers would try to solve that problem by dampening the loud vibrations created when trains pass over tracks (that noise itself is a form of energy). The Facility proposed instead trying to capture that energy and turn it into electricity, eliminating the noise while also creating something valuable in the form of zero-carbon energy.

From there, a similar idea is feasible with footfall: If you create a flooring surface that moves, imperceptibly, with the weight of many people walking, that energy could be absorbed and converted into electricity. The shifting floor could move fluid – through a series of subsurface tubes – that then drives small turbines linked to a generator. Or your footfall might compress flooring material that generates electricity. The core technology here is not really novel (the idea relies on electromagnetic induction, Schneider tells us, which is about 200 years old). Rather, it's the application of the technology that's new.

The more the floor moves, the more energy you generate. But you probably wouldn’t want to walk on a surface that feels like a sailboat. And so The Facility is aiming for a flooring design that would shift by about 3 millimeters, creating something that would feel about like the rubberized surface at a children’s playground.

The Facility has already developed some small-scale prototypes capable of illuminating LED light bulbs. But the concept stalled when the recession hit.

“What was going be a big R&D project, a couple million-pound investment, was something scaled right down to where it had to be more commercially viable,” Schneider says. “And that kind of sharpened our focus from conceptual R&D to what’s going to work in the real world.”

So what will work in the real world?

The amount of energy generated by pedestrians is relatively small compared to other renewables like solar power. You could potentially use that energy to power a metal detector at a public event. But Schneider concedes that it would make more sense to just slap a solar panel on top of it. Other small-scale infrastructure, however, is now appearing all over cities: sensors.

“And that suddenly became very commercially attractive,” Schneider says. Sensors to what end? "To any end: traffic flow, traffic calming, information, wayfinding, health care, security, building automation. There’s a huge amount of potential in that area."

"Smart Cities” are now trying to put sensors on everything. And this could be a way to power them. The Facility is now trying to develop a floor that could map where people are in a building (or how they loiter and move through a store). This information might also be particularly useful in assisted living facilities. And the source of the data – foot traffic – also powers its collection.

Something similar could be deployed at the bottlenecks of dense foot traffic, for instance heading into a subway turnstile. There, the energy might operate the turnstile itself (or the sensor in it that reads your transit card).

Other, non-bipedal applications are still possible, too. Schneider suggests that roadways could absorb the braking energy from cars as they slow down. And the Facility is still working on a railway tie (containing a small suspension) that might generate electricity from passing trains for use in powering other smart technologies along rail corridors.

Today, it doesn’t exactly make financial sense to harvest the energy of tires and feet when we’ve got fossil fuels and solar power.

"But all innovations, when they’re new to market, are disproportionately expensive," Schneider says. The first automobile was insanely unaffordable. So was the first solar panel. But within a few decades, that changed. "That’s what you’ve got to look at," Schneider says.

Besides, this idea may have market forces on its side (if not angel investors who disappeared with the recession). The cost of most fossil fuels will only go up. And so will the demand for sensors. Schneider sounds certain that this technology will one day address both trends.

“Without a shadow of a doubt,” he says. “I think it’s not something that’s going to be ubiquitous in the next ten years. But it will react to the demands of modern cities. And modern cities are becoming much more connected."

Top image: PHOTOCREO Michal Bednarek/Shutterstock

About the Author

  • Emily Badger is a former staff writer at CityLab. Her work has previously appeared in Pacific StandardGOODThe Christian Science Monitor, and The New York Times. She lives in the Washington, D.C. area.