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Last Updated: Wednesday, 24 May 2006, 11:06 GMT 12:06 UK
Charging up the stairs
Canary Wharf
Transport hubs could be wired up
Can we harvest the energy expended from footsteps and the vibrations from trains? Architect Claire Price describes how this can be put into practice.

Reading this, your body at rest is emitting about 100 watts into the environment. If you're sitting in an open plan office, count the number of surrounding colleagues and you don't need to be a maths genius to appreciate the possibilities of tapping into all that wasted energy.

Instead it could provide a renewable energy source to power office lighting or laptops - and it may be possible to recharge your mobile phone by walking to the photocopier.

Energy harvesting is an exciting field to explore, looking at ways to tap into the energy available from the workings of the human body or transport vibrations.

There's been a surge of interest over the past 10 years, driven by the search for battery-free techniques for powering wireless sensor networks, laptops and mobile phones.

The concept was pioneered by the military sector, largely bankrolled by the DARPA in the United States (Defense Advanced Research Projects Agency).

Their interest is mainly in reducing the need for soldiers to carry heavy rechargeable batteries that serve essential yet power-hungry communication devices. So they've looked at how "heel-strike" generators, powered through the pumping motion of a footstep, can be embedded within a boot heel. These devices currently achieve upwards of 3 - 6 watts of power output.

Rush hour

So the 34,000 commuters who pass through Victoria underground station at rush hour, for example, could theoretically generate enough energy to power 6,500 LED light fittings - energy that today is disappearing into the ground.

Energy from vibrations
Elsewhere in the world, researchers are also looking into how energy harvesting devices can be embedded within roads or how they can be used to create a self-powering heart pacemaker or even an artificial limb.

Already there are skis and tennis rackets that incorporate a "piezoelectric" material (which produces an electrical charge when stress is applied to them) that can dampen the vibration and reduce damage to the human joints.

For railway arches, rather than merely trying to dampen the noise and vibration, the architectural practice of which I am a director is trying to harness this energy to help light buildings.

The possibilities of this new sustainable energy source need not stop there as vibrations are created everywhere that people and transport are - railway stations, airports, roads and public thoroughfares.

Floor power

We are applying and testing our ideas practically within a building project within the next year, including a sprung floor fitted with heel-strike generations to harvest the energy from people walking across it. This power output will then be wired back to provide the lighting within that building.

London Bridge station
Walking to make light
We also plan an LED light fitting with its own micro generator. This unit will convert vibrations from passing trains, lorries or planes to provide continuous light without the need for wiring into the grid.

This could potentially mean considerable savings by omitting the need for the costly digging and laying of cables.

In the future, such devices could be part of our everyday environment, monitoring temperature, light and the location of people in offices, to increase the efficiency, comfort and security of our buildings. These could be wired into a central computer to alert it when windows have been left open or lights left on at the end of the day, and so switch them off.

One day when you use a staircase at a tube station, it might be a step towards saving the planet.

The Material World will be broadcast on BBC Radio 4, Thursday May 25 at 1630 BST. Claire Price is director of the Facility architecture practice in Bermondsey, south London.

Add your comments on this story, using the form below.

My first thought is that to encourage this sort of behaviour and investment for the sprung floor electricity generation would be a night club. Surely it is not beyond someone's technical capabilities to rig up the floor to the lighting control panel. Once the power generated by the dancefloor motion reaches a certain level a synchronised light display/show commences and would continue for as long as the energy generated exceeds a certain level.
Michael, Hampshire

Energy companies should invest in gym equipment and have their cardio machines linked to energy generators. People running on treadmills could generate electricity... imagine the incentive to exercise if you got paid to go to the gym!
Anon, Edinburgh

You don't get anything for nothing - driving a truck or train over a device that is designed to flex will use more fuel than driving over more solid ground. The amount per vehicle would be miniscule, but could mount up to greater overall fuel consumption by all road users. On the other hand, this would be a good thing when harnessing energy from footsteps - tackling our thirst for power and obesity simultaneously.
Ian Shepherd, Milton Keynes, UK

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