Hydrogen-on-demand process helps feed fuel cell fever - Street Smarts - Brief Article - Column

Diesel Progress North American Edition, May, 2002 by Rob Wilson

Logic might dictate that fuel cells will first come into play in stationary applications, where logistics and infrastructure for fueling would seem to be more manageable. But with the great amount of attention and funding that automakers are giving to fuel cells, the first mass applications could well be vehicular.

As part of the energy venue at the Hannover Fair in Germany last month, fuel cells were the center of attention, shoving other alternative energy technologies such as wind power and solar panels to the side. The themes and applications pursued by nearly 90 exhibitors were extremely divergent and some of it also seemed far-fetched.

I'm thinking of one particular fuel cell the size of a large microwave oven that has an output of 500 watts. It's hard to escape the reality that you would need three of these to run a hair dryer. I have a hard time convincing myself this particular cell can have practical applications. Yet people see great promise in standby power applications for hydrogen fuel cell power and strive to resolve fuel containment and storage issues.

I am personally more impressed by something like the HydroGen3 prototype from Opel and GM. In the project an Opel Zafira five-seater has been converted over to fuel cell power with impressive results. Its fuel cell stack has constant power of 94 kW, peak power of 129 kW, and provides the vehicle with a range of approximately 250 miles. It accelerates from zero to 60 mph in 16 seconds and has a top speed of just over 90 mph.

Another impressive program is the Mercedes-Benz Citaro municipal bus program that will place 30 fuel cell-powered buses in 10 European cities in the summer of 2003. This is actually the first case where we are talking about a limited production series rather than a prototype vehicle. These buses are powered by two Ballard Mark 900 hydrogen fuel cell stacks driving a 600 V motor with an output of 200 kW Performance is said to be comparable to a diesel or natural gas-f fueled bus.

But it takes nine roof-mounted, robust steel cylinders to contain the equivalent of 487 gal. of hydrogen at just over 5000 psi for the Citaro bus. I think this is the awkward, difficult side of packaging this fuel cell technology and the part that has to be simplified. Great strides have been made in the power density of fuel stacks and battery backup power systems have even been dropped on prototypes like the HydroGen3. Fuel storage systems have not improved at a commensurate pace.

One promising alternative might be producing hydrogen-on-demand through a chemical process. A company named Millennium Cell has developed a System for generating hydrogen-on-demand from an aqueous solution of sodium borohydride, which is made from commonly found borax.

The sodium borohydride is introduced to a proprietary catalyst bed producing hydrogen at 100 percent relative humidity and a byproduct sodium metaborate, which is essentially borax. The borate is returned to a collection tank and can be reprocessed into sodium borohydride.

Only a small amount of hydrogen is kept in a buffer at about 100 psi to insure instantaneous starting. It does still take an oversized fuel tank to contain the fuel feedstock and byproduct, but there are no special high pressure or cryogenic temperature requirements.

Chrysler has fitted this hydrogen-on-demand fueling system to a Town & Country van called Natrium (Latin for sodium). The vehicle just started its first public road testing phase in mid-April.

The Natrium vehicle has a range of 300 miles, thought to be the high water mark for fuel cell prototypes, top speed of 80 mph and acceleration of zero to 60 mph in 16 seconds. The vehicle is powered by a Ballard/XCELLSIS fuel cell, equipped with a 40 kW lithium ion battery pack. The actual motor is a 35 kW Siemens a.c. motor. The vehicle is front-wheel drive with regenerative braking.

The packaging of the entire drive and fuel processing system is entirely under the floor of the minivan, with absolutely no intrusion into the cabin of the van. This looks like a considerable step forward.

Though the hydrogen-on-demand processing system is used in conjunction with a fuel cell in this case, it could also be used to fuel and internal combustion engine. This will be an interesting one to watch.

STREET SMARTS IS A MONTHLY COLUMN DEVOTED TO THE ON-HIGHWAY ENGINE MARKET. ROB WILSON 15 PRESIDENT OF DIESEL & GAS TURBINE PUBLICATIONS.