Green machine: Power from the people


Earth 19 April 2010

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People power

(Image: Eliot J. Schechter/Getty)

At the end of a hard day it can sometimes feel like gadgets such as phones and computers are sapping our energy. But now they are set to do it literally, and we should be pleased.

Technologies that harvest energy from movement could see your every move charge a mobile device, or even a building. Such people power could provide an alternative to mains charging of electronic gadgets, reducing energy consumption and greenhouse gas emissions.

Crowdsourced energy

London-based architectural research firm Facility: Innovate is developing an energy harvester for crowded areas such as sports arenas and shopping centres.


The technology will be invisible to the people it feeds on: they will simply walk over what looks like a normal floor tile. But their steps will push down on a pneumatic device that drives air through a turbine to generate electricity, says managing director Oliver Schneider. People will feel only a slight movement at most, like stepping on an entrance mat, he says.

“We’re looking to generate around 1 kilowatt-hour of electricity [from each device]per day. That’s enough to charge around 300 phones per day,” he says. The power will be fed to phone-charging stations, or to lighting and electronic advertising. The system generates a direct current, so using it to power DC devices locally is more efficient than switching to the alternating current needed to feed it back to the grid.

The company plans to install its first device later this year in a US shopping centre, with a UK site to follow soon after. “Ticket barriers at sports stadiums are also a good spot, anywhere people are funnelled through a small area,” Schneider says.

Unlike existing energy-generating paving slabs such as those developed by London-based Pavegen Systems, the technology can be installed under conventional flooring, allowing it to be used in a wide range of settings without altering a building’s appearance, claims Schneider.

Strain gain

But Zhong Lin Wang at the Georgia Institute of Technology in Atlanta wants to generate electricity from footsteps without ripping up the flooring at all. He hopes to produce devices such as shoe pads that harvest energy from the pressure of their wearer’s feet within the next five years, using piezoelectric nanowire generators that produce an alternating current when squeezed.

Just last month Wang published the results of experiments on a device about 5 centimetres across that when flexed can produce 1.3 volts, enough to charge an AA battery.

Meanwhile Chieh Chang at the University of California, Berkeley, and colleagues have developed a technique to “print” nanowires that generate energy in the same way. They are made with a process known as electrospinning, in which a charged solution is drawn through an electrically charged needle onto an electrically grounded surface.

That method can print nanogenerators on all kinds of surfaces, including textiles, raising the possibility of clothes that power electronic devices as the wearer moves.

More on these topics:


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