Powering the $100 Laptop

An efficient handheld generator could help bring computing to the world's poor.

As the One Laptop per Child project, a nonprofit effort based in Cambridge, MA, nears the completion of its rugged and versatile laptop designed for school children in poor countries, a key component has fallen into place: an efficient, human-powered generator that could make the computer practical for children living in areas without reliable, affordable electricity.

The first working prototype of the $100 laptop. Conspicuously missing: the hand-crank generator present in an earlier design. The new human-powered generator will be separate from the laptop itself, and much more efficient than a hand crank. (Courtesy of One Laptop per Child, Cambridge, MA)

The new generators, which will be field-tested beginning this October, abandon the bulky and inefficient hand-crank design featured on an early mock-up of the laptop in favor of a more compact off-laptop design that uses a pull string to spin a small generator. It was developed by Squid Labs, Emeryville, CA, a design and engineering group whose co-founders include several graduates of MIT's Media Lab, where the laptop project originated.

The $100 dollar laptop will include a 7.5-inch screen, a 500 megahertz processor, 500 megabytes of Flash memory, and wireless broadband for forming impromptu networks with other laptops. It will also be a multimedia workstation, supporting the playing and composing of music, for example.

The new generator will make the laptop much easier to power than it would be with a hand crank, in part, because the users will be able to operate the generator in a variety of ways, including holding the device (the size of two hockey pucks) in one hand and pulling the string with the other, or clamping the generator to a desk, attaching the string to one foot, and using leg power. "We wanted something that could take advantage of other muscle groups in the human body that can put out a lot more energy than the muscles that you get when you're just turning a crank," says Colin Bulthaup, a co-founder of Squid Labs.

To reach the project's goal of one minute of power generation for every ten minutes of laptop use, the generator would need to produce 20 watts (the laptop will require less than two watts in a primary application as an electronic textbook replacement). "With a hand-crank system, if you're gung-ho about it, you can get about five watts out of it. But you get tired after about a minute or so," says Geo Homsy, a partner and designer at Squid Labs. With the new system, generating 20 watts is comfortable, and it's possible to generate 10 watts for "as long as you want," the developers say.

The new generator is also quiet -- one of the key design requirements. "If you imagine an entire school room full of kids using this thing, it needs to be as quiet as possible. Otherwise it will drive everyone insane," Homsy says. Typical generators work best at high revolutions per minute, requiring noisy gears to step up the speed. The developers have done away with gears by custom-designing a generator that runs most efficiently at lower RPMs, a move that also makes possible a smaller device.