Generating electricity isn’t limited to burning things, making steam, or harnessing the power of wind, wave, and sun—even though these are by far the most common ways of doing so. Delving into the more obscure, you’ve no doubt seen people peddling a stationary bicycle to power some lightbulbs; and you may have a crank-powered emergency radio or flashlight in a drawer someplace. But did you know that companies have tried and are trying to generate power from people jumping around and dancing in clubs, and even by them them just walking down the street?
All are technically possible, for sure. The technology isn’t crackpot. But against the backdrop of the massive amounts of energy we use, that we need to start generating from non-polluting sources (and now!), are any of these forms of renewable energy really worth the effort?
Let’s take a look.
For well over the past hundred years there have been pedal-powered machines, using something approaching what we’d today easily identify as parts of a bicycle. If we include treadle-powered and hand crank machines, the history of humans taking advantage of gears, cranks, and levers to boost the ability of machines to do work is much much older—for the past millennium at least.
From the 1870s through the turn of the 20th century the number of pedal-powered machines was astounding, and very, very efficient in many ways. In fact, much more efficient in many applications than generating electricity through pedal power.
As far as using pedal-power to generate electricity, these machines have a much less old pedigree, dating back to the 1970s. In the past several years they’ve certainly risen in popularity: During the COP15 climate talks there was a large array of them in Copenhagen demonstrating the potential of moving legs and pumping hearts to light up a Christmas tree. During the Occupy Wall Street protests in lower Manhattan, when the police pulled the power running into Zuccotti Park, activists rigged together several energy bikes to keep the electricity running.
Bicycle-powered generators work. They can be made from essentially scrounged parts. They definitely have a certain allure to them, a certain deep DIY sensibility. But they are unfortunately seriously inefficient when it comes to generating electricity.
Low-tech Magazine has a superb take-down of them, highlighting how the efficiency of these machines drops (and drops, and drops) every step of the way.
Here’s the gist of it: 1) Do to internal energy losses and inefficiencies, if the legs are capable of generating say 100 watts of power, well of half of that gets thrown away just converting the motion of your legs to electricity. 2) Because most of these use an ordinary bicycle just hooked up to a stand, the friction drive that connects them drops the efficiency of the system even more. 3) Due to the position of the rider on the bike leaning forward, in most bikes used for these devices, there are further efficiency losses—what’s good for aerodynamics going down the road isn’t as good for generating electricity.
That’s just generating the electricity. Once you take into account that the battery hooked up to it has a good deal of embodied energy in it, the conclusion of Low-tech Mag that you’re essentially just pedaling to pay back the energy needed to make the battery really takes the air out of the tires of these systems.
For most uses that is. In quasi-emergency situations, such as the OWS protests or perhaps in disaster situations, where you have no other way of generating electricity, there may be so good sense in getting on the energy bike.
But as part of the bigger picture of an all-renewable energy future, this is a teeny tiny niche application. In fact, if people want to burn calories to power machines, it’d be far better to do it directly, like our great-great grandparents’ generation did.