Solid (State) Progress; June 2005; Scientific American Magazine; by Steven Ashley; 3 Page(s)

Motorists expect cars to go at least 300 miles between fill-ups. That's not a concern for autos that burn gasoline or diesel, but for a future in which vehicles run on nonpolluting hydrogen, adequate driving range remains a real roadblock [see "On the Road to Fuel-Cell Cars," by Steven Ashley; Scientific American, March]. Despite considerable effort, engineers have so far failed to find a way to cram enough hydrogen--the lowest-density substance in the universe--onboard cars.

Conventional approaches to compact hydrogen storage--compressing the gas to up to 10,000 pounds per square inch (psi) or cooling it down to cryogenic temperatures so that it liquefies (around -252 degrees Celsius)--can attain only about half the energy density needed to fit enough fuel inside something the size of a gas tank. A few years back researchers thought that hydrogen could be extracted chemically onboard from liquid hydrocarbons such as methanol, but those schemes did not pan out. Since then, solutions to this packing problem have been lacking, notwithstanding long-term research programs at General Motors, Toyota, BMW and others. But recently hints of progress have emerged. Scientists at GM and its partner HRL Laboratories in Malibu, Calif., have reported advances in two hydrogen storage technologies--cryoadsorption and destabilized complex metal hydrides.