Man power: a great alternative

Pressure pads under pavements could generate electricity from every step we take. Meg Carter on the alternative energy source that stands out from the crowd

Can a staircase capture energy from people walking up and down it, store it as electricity and use it to power lighting? It sounds like science fiction, yet it is one of a number of seemingly far-out ideas being taken very seriously by scientists and engineers whose goal is to harness the generating power of the human body.

"When we walk along a pavement, eight watts of energy is wasted - absorbed by the ground - with each heel. Yet it's possible to harvest at least 30 per cent of that energy," explains Claire Price, a director at The Facility Architects in London.

"Think of a dance floor, which is designed to dampen vibrations and limit the damage dancers could do to their limbs. What we're now working on features a matrix of energy harvesters positioned beneath a floor. These dampen vibrations but store rather than dissipate that energy to provide a source of power - for free."

Price is leading the Pacesetters Project, an initiative that will involve the installation of the world's first human energy harvesting staircase in Portsmouth's Spinnaker Tower early in the new year. Also taking part are electronics company Philips and teams from Hull University - which has developed a heel-strike generator that fits into a shoe to capture the energy exerted as we walk - and Southampton University, which has developed a way of generating power from the vibrations which naturally occur within buildings. Their aim is to show how power can be generated from human movement and to prove its potential to supplement power supply in public spaces.

"How best to store the harvested energy has been a challenge," Price admits. "Our focus is on improvements to super-capacitors and other storage devices. But we are confident that if the energy is used close to where it was generated, then these plans would be a feasible alternative to the national grid. It could power lighting, LED displays and audio systems used in public spaces."

When you consider that a busy transport interchange such as Victoria station in London is used by an estimated 34,000 pedestrians an hour at peak times, footfall sounds like a viable alternative source of power. And there's another potential green benefit: once an electrical appliance no longer needs to be wired into the grid, less copper and plastic will be required.

So if human energy has this sort of potential, why has it not been properly exploited before? Rory Steer, executive chairman of Freeplay, which developed the first wind-up radio, dreamt up by British inventor Trevor Bayliss just over a decade ago, explains. "The energy generated by human activity needs not only to be effectively harnessed but also efficiently stored and then released in a controlled manner," he says. "And a large amount of human effort is required to generate even a modest amount of power. How long will someone be prepared to work to store the energy for a particular product? However, as electrical products are designed which consume less power, the potential applications grow."

And it is this that is now kick-starting interest in self-power generation. A growing number of low-power electrical goods are now available. And advances have been made in understanding how to capture, store and release human energy. The Pacesetters Project is not the first attempt to harness human energy, points out Professor Neil White of Southampton University, who has developed a device that can harvest energy from vibrations in buildings.

"Back in the Eighties, Seiko developed the Kinetic wristwatch, powered by human movement. This did away with the need for a conventional battery by exploiting the distances the human arm can cover over time," he says. "A number of kinetic watches have since been produced, but the potential of this technology to power larger electrical items is limited by the low speed at which people move."

The US and UK armies had experimented with energy-harvesting devices that could be built into soldiers' boots. One application for this technology was to provide an power supply to run radio telephones traditionally powered by unwieldy rechargeable batteries. However, plans foundered when it became clear the harvesters weren't robust enough to withstand extreme conditions.

Then in the early Nineties along came Freeplay, with its wind-up radios, lights and torches. More recently, it invented a wind-up generator to charge mobile phones, a foot-pump generator capable of powering larger items and a prototype range of wind-up medical equipment. It is also involved in developing the wind-up mechanism to power the so-called $100 (£53) laptop - being developed to bring the PC to children throughout the developing world.

Opinion is divided on what is the best way of harnessing human power. For some, the future lies in built-in devices such as the heel-strike generator; others point to mechanisms able to harness the energy generated by combined human activity.

Price says the Pacesetters Project has already attracted attention from the business world. She is working with a manufacturer of gym equipment to develop a way of harnessing power generated by people using running machines.

Steer, meanwhile, has struck a deal to launch renewable-energy-powered products in India. Yet he believes the future for Freeplay lies in developing products that combine wind-up technology with solar and wind power. "Sustainable energy is a niche business in the developed world and probably always will be - except in the UK, where legislation is encouraging its development," he explains. "The reason's simple: the average consumer wants the easiest access to energy - the national grid."

The story so far...

Seiko launched its first no-battery watch powered by the wearer's movement back in 1988. Its Kinetic range uses an oscillating weight that is rotated by the movement of the wearer's wrist, which is transformed into a magnetic charge then into electricity, which is stored in a tiny capacitor and rechargeable battery.

Massachusetts Institute of Technology's MIT Media Lab is one of a number of institutions exploring the potential for devices embedded in shoes to generate power while the wearer is walking and even harvesting energy from finger motion. Possible footfall applications include powering a radio or a wearable computer.

The Japanese rail company East Japan Railways earlier this year installed ticket gates that generate electricity from the vibrations and pressure created as people pass through them. The electricity is used to operate the automatic gates.

Freeplay developed and manufactured the original wind-up radio invented by Trevor Bayliss. Since then it has developed a whole family of wind-up radios; branched out into wind-up torches and hybrid products using solar and wind-up power; and recently launched Weza, its first foot-pump generator. Planned future applications of its technology include self-generated medical equipment.

Researchers at Georgia Institute of Technology have demonstrated that inexpensive nanowires can be used to harvest mechanical energy from inside the human body. This could be used to power advanced medical implants.