For the One Laptop Per Child’s (OLPC) XO-3 tablet, thrift means not only a low price but also extreme efficiency harnessing meager sources of power. Just 4 percent of the communities that OLPC reached with its original product, the XO laptop , even have wall outlets to plug a charger into. For the rest, the XO-3 has special technologies to squeeze out power from a motley collection of sources – many of which would fry a first-world gadget.
One is an optional hand-crank generator that OLPC provides. The challenge: Different people crank with varying amounts of gusto from one moment to the next, producing wildly fluctuating voltage that no typical gadget could handle. Take a tablet sold in the U.S. that comes with a 12-volt charger. If that wall wart is off by just a fraction of a volt, protection circuits stop the tablet from even taking the charge, said Ed McNierney, the chief technology officer of OLPC . The XO-3, however, is equipped with special protection circuitry that can accept anything from 10 to 25 volts.
That covers hand cranks, bicycle-driven generators or even water wheels. “There’s actually a village in Madagascar,” said McNierney, "they have a reservoir up on the hill, and a pipe comes down and powers their generator. And they power the light in the evening, they run a compressor to make ice, and they charge the laptops.”
OLPC also provides a solar charging panel fitted onto a removable, rubberized cover for the tablet. Getting the XO-3 to work well with that — or any other solar panel — was another challenge. The power coming off a panel waxes and wanes from dawn to dusk and the shade to the open. “You have to vary the voltage of your device in order to efficiently use that power,” said McNierney. “We had to build hardware and software specifically for solar panels.”
None of these efficiency measures would be necessary in the US or any other country with a regular electric grid, he explained. “We don’t care if one half the power from iPad charging is lost,” said McNierney,“But power really matters to them.”