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VW Fuel-Cell APU with On-Board Reforming

Volkswagen has tapped IdaTech to design and manufacture an integrated fuel processor system operating on diesel fuel to be used in a fuel-cell-based Auxiliary Power Unit (APU). Fuel-cell APUs are of increasing interest for cars, vans and trucks that require a great deal of additional electricity (for communications, air conditioning and so on). Rather than burning gasoline or diesel to produce the power, the APU-enhanced vehicles rely on the electrical output of the fuel cell.

The fuel processor system apparently will become part of a demonstration project that VW is building using the T5 Transporter— a multipurpose van. In April of this year, the German state of Lower Saxony launched a fuel cell initiative at which VW showed an earlier version of the T5 equipped with a PEM (Proton Exchange Membrane) fuel cell APU using liquid hydrogen.

The Idatech fuel processor eliminates the need for a discrete hydrogen fuel source on the vehicle by providing on-board reforming of the primary fuel: diesel.


The IdaTech fuel processor (see schematic at right) first vaporizes the incoming diesel fuel in a combustion chamber. A catalyst then reforms the vaporized fuel into several gases, including hydrogen.

A palladium-alloy membrane then purifies the reformate by essentially passing through only hydrogen, which then feeds into the APU. The purifier also rejects trace contaminants such as sulfur compounds, unsaturated hydrocarbons, and amines. The separated impurities combine with ambient air and are fed back as fuel gas to the combustion chamber.

The resulting product hydrogen is typically greater than 99.95% pure, with <1 ppm CO and <1 ppb total sulfur compounds. Typical PEM fuel cells requires <10 ppm CO and <50 ppb total sulfur.

In the run up to hydrogen fuel vehicles, VW is concentrating on its diesel platforms and on synthetic biofuels as its primary approach to green cars. (An earlier post on a VW gas-hybrid test here.) The APU application of fuel cell technology is complementary to this approach.

Until such time as fuel cell technology has reached full maturity, Volkswagen is also using the synthetic bio-fuel SunFuel as part of its fuel strategy. We are convinced that the coming decades will see a co-existence of combustion engine and fuel cell and are therefore promoting both fuel cell technology and the development of new usage concepts for biomass.

Together with Swiss Paul Schere Institute (PSI), VW unveiled its first fuel cell car in November 2000, the Bora HyMotion. Fuelled by liquid hydrogen it has a top speed of 84 mph and a range of about 210 miles. Volkswagen has also been involved with the European Union funded CAPRI project to produce a methanol fuel cell vehicle.

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