[H.sub.2] going for distance.

A team of researchers at Lawrence Livermore National Laboratory in California is claiming the world's record for distance in a hydrogen-fueled car, thanks to a new high-pressure cryogenic tank they have developed. The group ran a Prius around the Livermore lab's campus for a total of

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One of the researchers, Salvador Aceves, told us the claim is based on publicly available information. Last May, General Motors claimed a record with a fuel cell car that ran for 300 miles on a single tank of hydrogen. That would be just under 500 km.

The Livermore team has been in pursuit of a traveling container for hydrogen for some years now. The cover article, "Fill'er Up--With Hydrogen," in our February 2002 issue reported on the group's tests of a version of the cryogenic tank. They had roasted one in a tire and shot one with a .30-caliber round to establish that the design was sale enough to install in an automobile.

Aceves, a former chairman of ASME's Advanced Energy Systems division, said the group has made a lot of progress since 2002. "We did two demonstrations in two different vehicles: a Ford Ranger pickup truck and the record-breaking Toyota Prius," Aceves said.

He said the new pressure vessel carried by the Prius is 47 inches long and 23 inches in diameter, of about 120 cm by 58 cm, considerably smaller than earlier versions, like the one in the pickup truck, but it stores more hydrogen. The larger tank capacity and the fuel efficiency of the hybrid Prius produced the world record driving distance. The Prius uses a small internal combustion engine and an electric motor. According to Toyota, Prius models burning gasoline average 46 miles per gallon, which translates to roughly 20 km per liter.

Aceves, who leads the Energy Conversion and Storage Group in the lab's Engineering Directorate, said the Livermore team expects to enter a collaborative agreement with an automobile manufacturer to develop the technology as an option for hydrogen storage in cars.

The tank developed at Livermore uses a vessel of aluminum coated with carbon fiber as the high-pressure inner vessel. It is surrounded by a vacuum space filled with reflective plastic and an outer stainless steel jacket. It is designed to accept liquid hydrogen--that is, chilled as low as 20 kelvin, or -253[degrees]C--or compressed gaseous hydrogen.

According to Aceves, the inner tank is a commercially available vessel of a sort commonly used to store compressed gases. The aluminum liner, about 6 mm thick, is wrapped in layers of carbon fiber tape wetted in epoxy resin. The carbon fiber provides strength and the aluminum liner provides containment for the hydrogen.

"Our contribution was demonstrating that we can use these same vessels for storing cryogenic liquids," Aceves wrote in an e-mail. "Storing cryogenic liquid hydrogen increases the system density by a factor of 1.5-2 with respect to compressed hydrogen tanks (due to the higher density of liquid hydrogen). It also eliminates evaporative losses under practical vehicle-use scenarios. Evaporative losses have been the limiting factor in wide spread utilization of liquid hydrogen tanks."

The tank remains at liquid-hydrogen temperature (33 kelvin or colder) for about one day when initially full. Today's low-pressure liquid hydrogen tanks typically start losing hydrogen to evaporation at low temperature (typically 28 kelvin).

The Lawrence Livermore team says its experimental tank can contain the hydrogen until it reaches about 65 kelvin. This ability allows three extra days before evaporative losses occur. If the vehicle is driven during the four days, the dormancy rapidly increases. Travel of perhaps as little as 10 miles a day can eliminate evaporative losses.

The rated pressure of the tank is 5,000 psi. If the pressure is exceeded, a relief device opens to release some of the hydrogen.

The research team has 13 members besides Aceves: Gene Berry, Francisco Espinosa-Loza, Rich Fairchild, Dan Flowers, Jim Fugina, Brian Kelly, Fernando Luna, Mark McCuller, Blake Myers, Sue Pierce, Tim Ross, Vern Switzer, and Andrew Weisberg.

According to the Livermore Lab, the research group's work on the fuel tank, which began more than a decade ago, has come under the Department of Energy's National Hydrogen Storage Project, a component of President Bush's Hydrogen Fuel Initiative, which began in 2003.