June 2008

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LIVERMORE, CA - One key problem of storing liquid hydrogen on board a car or truck - quick evaporation of the ultra-cold fuel - may be on the way to a solution.

And in the process, the issue of whether liquid cryogenic hydrogen or compressed gaseous hydrogen is the preferred storage technology may fade away with the development of a so-called cryo-capable hydrogen storage tank that can be refueled by both.

Such a tank, under development here at Lawrence Livermore National Laboratory (LLNL) and installed in a Toyota Prius that had been converted to hydrogen (H&FCL DoE News, June 07), recently set a record without much fanfare by storing the liquid hydrogen at minus 420 deg. F (minus 251.1 C) for six days without venting any of the fuel. And the tank design holds promise for extending no-vent storage for as long as 15 days, according to a note sent to H&FCL by Salvador Aceves, the team leader of the tank development team.

At least one major carmaker, Germany’s BMW, is looking at similar concepts. In fact, BMW is cooperating with the LLNL team in advancing this technology, BMW has told H&FCL.

Currently available cryogenic hydrogen tanks can hold hydrogen for no more than 2 to 4 days during long-term parking for example even with the best available insulation which is about 200 times less heat-conductive than styrofoam insulation.

One reason why this tank performs the way it does has to do with the fact that it is constructed much stronger than conventional liquid hydrogen tanks - more like a compressed hydrogen tank but with added features. Normal automotive LH2 tanks operate at low pressures between 2 and 10 atmospheres. But the LLNL cryogenically capable tank can operate at pressures of up to 350 atmospheres, similar to scuba tanks, holding the hydrogen in as pressure increases due to heat transfer from the environment.

Additionally, the tank’s thermal endurance improves as the tank empties with fuel being fed to the fuel cell, or i.c. engine: the Lawrence Livermore team believes the tank can hold hydrogen fuel indefinitely when it is about 1/3rd full.

Last year, the LLNL team set a record with the converted Prius, travelling 650 miles on a single tank of hydrogen (H&FCL Feb. 07). “These two advantages make LH2 vehicles far more practical in the search for a replacement to today’s gasoline automobiles,” the LLNL note said.

BMW evidently agrees. Company experts described its efforts both at the recent NHA annual conference in Sacramento, CA where it displayed the latest mono-fuel version of its Hydrogen 7 series sedan which runs on hydrogen only (The first one ran on both gasoline and LH2 - H&FCL Dec. 06). It also showed the car and described the concept in a briefing to reporters at the SAE World Congress two weeks later in Detroit but it didn’t present any papers on this work.

In an April 14 story on its website, “Automotive News” said cryo-compression would “give BMW a way to sidestep the debate over whether refueling stations should carry hydrogen in gaseous or liquid form,” using essentially “a conventional compressed hydrogen tank surrounded with an insulating jacket.”

“It‘s the best of both worlds,” Tom Baloga, BMW’s U.S. vice president of engineering, was quoted by the publication as saying. Baloga confirmed to H&FCL that BMW is working with Lawrence Livermore on these tankage concepts, adding that nothing had been published so far. “We have a way to go,” he added.

The new mono-fuel, hydrogen-only version is one of the cleanest internal combustion engined vehicles ever built. Tests conducted by DoE engineers at Argonne National Laboratory showed the engine surpasses the super-ultra low-emission vehicle (SULEV) the most stringent emissions performance standard to date. The car’s emissions “were only a fraction of SULEV levels,” the end-of-March Argonne release quoted Thomas Wallner, a mechanical engineer who leads Argonne’s hydrogen vehicle testing activities, as saying.

“The car’s engine actively cleans the air,” Wallner added. Argonne’s tests showed that “the Hydrogen 7’s 12-cylinder engine actually shows emission levels that, for certain components, are cleaner than the ambient air that comes into the car’s engine.”

Closer to home, the Lawrence Livermore team is also collaborating with Quantum Fuel Systems Technologies Worldwide, Inc., in Irvine, CA in developing next-generation manufacturing technologies for hydrogen storage vessels. Livermore is to demonstrate what’s described as unique high-speed composite processing technologies for building advanced tanks under a $5.6 million three-year contract with the U.S. Energy Department.

The LLNL team has developed a so-called dry tape winding process that drastically cuts the time required for pressure vessel winding of carbon fiber - 15 minutes compared to three hours for current method of wet winding.

And in yet another extension of the research collaboration web and apparently as part of that same DoE contract, Quantum is partnering with the Boeing Company in the development of hydrogen storage vessels. A Quantum release said Boeing has established itself as a global leader in advanced composite manufacturing technologies.

Boeing Phantom Works, the planemaker’s advanced research and development organization, will adapt precision composite manufacturing technologies it has developed for the aerospace industry in the development of these advanced hydrogen tanks.

Contacts: Livermore, media, Anne M. Stark, 925/422-9799, stark8@llnl.gov; Quantum, Dale Rasmussen, 206/315-8242, Drasmussen@qtww.com; BMW North America, media, Dave Buchko, 201/307-3709, Dave.Buchko@bmwna.com; Argonne, media, Angela Hardin, 630/252-5501, ahardin@anl.gov.