Daimler-Benz (DB) has moved fuel cell technology nearer to production reality with an
on-board system for generating hydrogen from methanol. The company, now working with the
Canadian company Ballard Power Systems, claimed the system as a "world first"
when it gave details at the Frankfurt Motor Show. DB calls the research vehicle NECAR (New
Electric Car) 3. It is based on Mercedes-Benz's latest model, the A-class. A reformer is
carried that converts the methanol into hydrogen by water vapor reformation. The hydrogen
gas is fed to fuel cells to react with atmospheric oxygen which in turn produces
electrical energy to power the car. The great attraction of methanol is that it can easily
fit into the existing gasoline/diesel infrastructure of filling stations and does not need
highly specialized equipment or handling. It is also easy to store on board the vehicle,
unlike hydrogen, which needs heavy and costly tanks. DB says NECAR3 has a range of about
400 km on a 40 liter methanol tank; it has decided methanol is a more efficient fuel for
hydrogen generation than either gasoline or diesel, both of which are being researched by
other manufacturers and suppliers. However, consideration is, initially at least, being
given by DB to multi-fuel hydrogen sourcing.
Detailing the research car, DB says the methanol reformer technology used has benefited
from developments that have allowed the system to become smaller and more efficient
compared to earlier efforts. But performance and dynamic response have been improved. The
result is a compact, 47-cm-high unit. Located in the rear of the A-class, the reformer
directly injects hydrogen "on-line" into the fuel cells. Hydrogen production
occurs at a temperature of some 280 °C. Methanol and water vaporize to yield hydrogen
(H), carbon dioxide (CO2), and carbon monoxide (CO). Following catalytic oxidation of the
CO, the purified gas is fed to the negative pole of the fuel cell. A special plastic foil,
which is coated with a platinum catalyst and sandwiched between two electrodes, is located
at this position. The conversion of the hydrogen into positively charged protons and
negatively charged electrons begins with the arrival of oxygen at the positive pole. Since
the foil is only permeable to protons, an electrical voltage, which can be used to drive
the electric motor, builds up across the fuel cell.
By Stuart Birch