An ingenious device that uses the energy from typing on a laptop's keyboard to recharge the battery has been patented by Compaq in the US. The keyboard generator could reduce the size of batteries or make them last longer.
The generator was invented by Adrian Crisan, who works at Compaq's Houston, Texas, headquarters. In his design, published in US patent 5 911 529, the shaft of each key has tiny permanent magnets attached to it, and each shaft is surrounded by wire coils. Every time a key is depressed, the magnets move through the coils, inducing a tiny current that is used to charge a capacitor. When the capacitor has a high enough charge, it recharges the battery.
The magnets, coils and charging mechanism will add to the cost and weight of a computer, but Crisan believes time and trends are on his side: "Displays, disc drives and other components in portables keep getting more power-efficient, and consumers are willing to pay for longer battery life," he says. "We will not know the economics of this keyboard until it is produced, but it could mean a 1-kilogram notebook instead of a 1á5-kilogram machine, or one that would last 10 hours on one charge, as long as you keep typing."
Most keyboards have springs to return keys to their original positions after they're struck. Crisan says that his generator should not significantly change their feel. "The magnets weigh a fraction of a gram each, and the conversion of kinetic to electrical energy shouldn't add any noticeable resistance compared to the return springs," he says.
Inventing such devices is just a sideline for Crisan. Although the three Compaq patents that bear his name are for improvements in hardware, he is actually a software engineer.
Author: Jonathan Beard, New York
New Scientist issue 24th July 1999
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