If you need portable electric power, batteries are your only choice. But everyone knows they love going flat when they're needed most.
Fuel cells are a different story, theoretically capable of storing vastly more energy.
Instead of returning an electric charge that was stored in it, like a battery, a fuel cell generates electricity by oxidizing fuel. Their greater storage capacity makes fuel cells the number-one topic in energy storage these days. Major auto makers are even talking about replacing engines that burn petroleum products with cells that oxidize fuel without combustion. Bob Hockaday, a Los Alamos basement inventor, has much smaller ambitions. Instead of powering Cadillacs and Camrys, he's talking about juicing up cell phones. .