People power

Every step you take, every move you make, every spin of the pedals on an exercise bike - you’re generating tiny amounts of power. Now scientists are working out how to turn it into electricity. Chris Alden reports.

Don’t tell me you haven’t dreamt about it too - when you were sweating away in the gym, lugging home the shopping, or just strolling in the park. It occurred to me when I was pootling round Peckham Rye in my jogging suit. This exercise lark, I thought, is hard work. Surely it must be possible to harness the energy we expend like this every day - energy we lose as heat - and use it to save the planet at the same time.

It turns out we dreamers are not alone. Scientists the world over are exploring ways to harness energy we use in our day-to-day lives - call it ‘human power’ - from nightclubs to gyms to city streets.

The last year has seen an explosion of ideas on how to do just that. In Zanzibar, there are plans for a luxury hotel gym which will convert the effort you spend on its machines into electricity [see GF63, ‘Zero in Zanzibar ’]. In Hong Kong, inventor Lucien Gambarota has rigged up 13 exercise bikes to turn pedal power into watts.

“When the DJ clears the room with cheesy Europop, he’s harming the planet in more ways than one.”

In the UK and US, scientists have designed backpacks and shoes that can convert energy from walking into enough power to run an MP3 or other portable device. And in Rotterdam, there are proposals to build a ‘green nightclub’, whose dancefloor will convert the movement of dancers into power (www.sustainabledanceclub.com), so when the DJ clears the room with cheesy Europop, he’s harming the planet in more ways than one.

But how much energy can we reasonably harness from human activity? How many laps of the Rye do I have to run to harvest, say, the same amount of energy a power station can produce in a day?

The answer, sadly, is far too many - and when dealing with generation from ‘human power’, it’s important to keep perspective, says Gambarota. “An average person can produce 50 watts,” he says - enough to power a few low-energy lights, but little more. “From the moment you wake up to when you go to sleep, even if you do extensive work - let’s say on a farm - the maximum energy you’ll produce is one kilowatt-hour. In terms of money, it’s 15 US cents [less than 8p].”

So if human power isn’t that powerful, why the fuss? One reason, apart from the fact that it’s good PR for gyms, is that it makes people think about energy. “When you work out on a machine and you see how painful it is to produce electricity,” says Gambarota, “you go back home and say to your kids: ‘Switch off the light.’”

Second, by definition, you’re carrying your power source with you - so power can be brought to difficult-to-access places.

Jim Gilbert, an engineer at the University of Hull, is working on electromagnetic sensors that harness energy from footfall. Along with wind-up radio inventor Trevor Baylis [see‘Start Me Up’], he developed an energy-harvesting shoe; now he’s working on energy-harvesting floors.

“One person walking generates around six watts of potential power.”

An ordinary person walking at one step per second, he says, is generating around six watts of potential power. “It’s not going to make a major contribution to carbon footprints - but where you want a relatively modest amount of power local to you or in a remote area, it has some potential.”

You can’t get much more local and inaccessible, of course, than inside the body. Like Gilbert, Paul Mitcheson from the control and power research group at Imperial College, London, is working on harnessing an exciting form of ‘human power’ - that produced by organs such as the heart.

Using electrostatic microgenerators, Mitcheson hopes to harness microwatts of energy - hardly enough to trouble the OPEC oil exporters, but enough to power medical systems. “You have to replace a pacemaker about every seven years,” says Mitcheson. “If you could power that pacemaker directly from the motion of the heart, that would be fantastic.”

Back in the heady world of single-figure wattage, there is a growth market in human-powered gadgets that take a little extra work to use. 

Apart from the famous wind-up radios, torches and mobile phone chargers, there are ever more applications for remote regions, such as laptops that give you an hour’s power for ten minutes’ cranking, and bicycle or treadle pumps to bring water up from a well or charge a battery. In India and Bangladesh in particular, such simple yet revolutionary technologies are now bringing water and electricity to some of the poorest villages - and outdoing pricey and polluting diesel engines.

“Imagine powering a pacemaker directly from the motion of the heart. That would be fantastic.”

In Africa, PlayPumps are catching on. These children’s merry-go-rounds power a pump to bring water to the whole community.

If that all seems too sensible, a recent US design competition was won by - wait for it - the world’s first yoyo-powered MP3 player.

Yet perhaps the most energy-saving form of human power isn’t the power we spend ourselves, but the extra work we can do to replace what is done more wastefully by machines.

David Gordon Wilson, now in his 80s and an emeritus professor at the Massachusetts Institute of Technology, is ex-president of the International Human Powered Vehicle Association. A self-confessed cycle nut, he designs energy-saving, human-powered gadgets like mowers and snow ploughs.

“I like to compete with my neighbours when there’s a blizzard here,” he says. “I get out my human-powered snow plough and clear my driveway in about half the time it takes other people to get out their petrol-powered machines and fire them up.”

Wilson points to research showing that a petrol-powered lawnmower causes as much air pollution in one hour as a family car in 100 miles. “Almost everything we do” could be done by human power if there were better gadgets for the job.

“If I want to drill a hole in a lot of pieces of wood, it’s great if I can sit at my drill press and pedal as they used to in the old days,” he says. “If we applied that to things like cutting hedges or mowing a lawn - if you could pedal in one place for a while and then mow a lawn with a powered device - that would be interesting.”

In a world of rising fuel prices, perhaps we’re all going to have to work a little harder if human power is to have its day once more.

Chris Alden is a freelance journalist specialising in technology.

24 June 2007

Chris Alden