Wind up your laptop

The human body can deliver enough power to drive computers, television sets and washing machines – but it does go hand in hand with lots of sweat.

Eco-tech boffins dream of self-sufficient gadgets: mobile phones fed by solar energy, heartbeat-powered music players. However, the potential of these energy sources is much too small. Handles, cranks and biking machines on the other hand, do have a promise to be a powerful energy source. Swinging a crank for fifteen minutes is enough to power a mobile phone. Less than an hour of pedalling a bike can power larger machines. The only thing missing is a remedy for laziness. 

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"With a hand crank it is possible to generate 35 to 60 watts, on a bike this sustained power capacity rises to 100 or 150 watts."

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A ‘green’ phone of Siemens made headlines on eco-blogs recently. The gadget is not only made of biodegradable plastic, it is said to also generate its own electricity by means of a small integrated solar panel. The phone, which will arrive on the market in two years time, made eco-geeks dream of a house filled with self-sufficient appliances: not only telephones, but later on also mixers, tellies and computers. Solar panels, however, are not the right technology to make that dream come true.

Green image

If you want to power a mobile telephone on solar energy, you need a much larger solar panel. A mobile is not a calculator. It would take weeks for the machine to be charged. Odds are that the gadget will eventually hit the market equipped with a plug. The solar panel is in that case good for a green image, but not more than that. A mixer or a TV on solar energy is even more unlikely, even in the far future.

Furthermore, it is not very worthwhile to install solar panels on gadgets that only last for some years. Because in that case the energy needed to produce the solar panels is larger than the energy saved during the machine’s use. The result, therefore, is not less but more energy consumption. It’s a much better idea to put solar panels on your roof, and simply plug your appliances in the sockets.

A more or less similar problem arises with the harvesting of energy out of internal processes in the body, or looking for energy in every day movements like walking. These are inventive ideas, but the technology will never power more than a pacemaker or a hearing aid.

Human energy plant

There is a much more ecological and powerful energy source available to power all kinds of devices: deliberate muscular strength. Although not easy to find, there are already appliances for sale that can get going by a handle or lever: radios, torches, mobile chargers, media-players and even a micro-generator. The latter is in fact a tiny energy plant with a plug and can be driven by a foot pump. Another supplier markets a system which can be used to turn your bike into an energy plant. 

With these tools, it is not the intention that you keep swinging or cycling while the appliance is working: by turning the crank or by pedalling, a battery is charged. Once you’ve put in the effort, the device can be used for some time.

The capacity of human kinetic energy is surprisingly large. With a hand crank it is possible to generate 35 to 60 watts, on a bike this sustained power capacity rises to 100 or 150 watts. The exact power is of course dependent on the fitness of a person. The best racing cyclists can keep up a power capacity of 300 watts, with peaks of 600 watts.

Watching TV

It takes approximately a few dozens of seconds or some minutes to power up a radio or a torch for hours of use. The battery of a mobile phone can be charged in a quarter of an hour. The driving of larger appliances demands some more effort. To surf the Net for an hour on a laptop, or watching TV for an hour, you have to get on your bike for around 45 minutes. If you want to watch TV on a large flat screen, you’d need to get the whole family on the bike. Gone are the days of slouching on the couch.

Gadgets driven by a crank are much more eco-friendly than devices powered by solar energy, since the production of the mechanism requires almost no extra energy or materials. Moreover, they have another interesting advantage: you can always count on them. The battery of your torch is never empty, and your phone can always be charged, even in the middle of the night.

The only drawback is that it takes a physical effort of at least some minutes. And for most people, that is enough to make fun of the idea.

Bicycle machines

In developing countries, self-sufficient appliances are more popular, for the simple reason that often there is no alternative. Worldwide almost two billion people have no access to electricity. The ‘one laptop per child’ project has developed a very economical laptop that is powered by a crank.

Another example is Mayapedal, an NGO in Guatemala that recycles bikes into muscular powered machines, for the manufacturing of food crops, the pureeing of fruits and vegetables, the pumping of water, the sharpening of metal, the sawing of wood, the washing of clothes or the generating of electricity. These are all processes we currently use fossil fuels for.

Mechanically driven devices also used to be very common in western societies. A bicycle lamp was not always powered by batteries, but by a dynamo. Not so long ago, all watches and clocks were wound up by hand. In the early twentieth century nearly all gadgets were powered by a crank: musical boxes, gramophones, toys, field telephones. Coffee-mills, mangles (to dry clothes) and drills lasted unto the fifties.

Progress or sheer laziness?

Since then, however, we have automated even the smallest physical act. No one is surprised anymore by an electrically driven screwdriver, a push-button can opener or an electric toothbrush. More recent examples are the electrically driven salt- and pepper mills, the fully automatic toilet, the intelligent trashcan and the high-tech wine cellar.

For every product, we have introduced an alternative with a cord or batteries. What is already automated gets automated even further: try finding a car with windows that can be opened manually. There is nothing to stop the birth of the electrically driven umbrella or the automatically folding handkerchief. Progress or sheer laziness?

It’s too easy to dismiss criticism on the ever increasing automation as nostalgic moaning. Because in the meantime the newspapers are full of warnings on the negative consequences of the fact that people are not moving anymore. Couple this with the economical and ecological consequences of our voracious energy use, and the solution is obvious. Instead of jumping on fitness appliances (that often consume energy themselves) we could use our physical strength to power our toy shop. In that case we kill two (or three, four) birds with one stone. (Picture: Passive working devices by Hungarian artist Antal Lakner).

This plea for beads of sweat does not mean that using solar energy for charging devices is per definition a bad idea. Just keep two things in mind: firstly, buy a solar panel that can charge different (generations of) devices, instead of a gadget with integrated solar panels. Secondly, buy a solar panel that is sufficiently large, and put it outside (for instance on the terrace). Groovy looking, convertible pocket solar panels do not have enough power to supply the required energy.

© Kris De Decker (edited by Vincent Grosjean) (Artículo en español)

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UPDATES

1. A team of MIT students powered a small supercomputer by pedaling bicycles. See the article on Computerworld.

2. Professor Alex Van den Bossche (UGent, Belgium) writes us to warn that human electricity generation is not always a good idea. "Physical effort requires more food. Especially meat, fish or tropical fruits demand large amounts of energy. To deliver 1 kilowatt-hour of electricity (fe, ten hours on a bike), you need to eat a surplus of around 1 kilogram of dry pasta or bread. But if you eat fish, you need around 5 kilograms (because most of it is water and has less calories). The catch of one kilogram of fish can cost up to 4 litres of diesel oil. This means that a human energy plant powered by fish needs 21 litres of diesel oil for the production of 1 kilowatt-hour electricity. A normal electricity generator needs only 0.2 litres of oil for the same amount and is thus 100 times more efficient. That does not mean biking is bad for the environment, since a bicycle weighs almost nothing compared to a car. But for electricity production, human power might be worse than anything else."

3. A knee brace can generate 5 watts of power - inspired by generative braking in cars

4. A bicyle machine from 1936

5. Wind up bed side lamp : for people who can't sleep without lights

6. Capturing human energy from revolving doors

7. Powering African schools with playground toys

8. Pull-cord generator by Potenco : one pull for every song on your mp3-player

9. Llamadas pedaleadas : phone calls powered by bikes (via earth2tech)

10. A pedal powered forklift (via Make)

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LINKS :

Build your own bicycle machine (another one here)

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Computing without electricity : mechanical calculators

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