VW Shows Off Fuel-Cell Prototypes: LA 2008
November 19, 2008 by admin
Volkswagen showed off two of it’s fuel cell prototypes at the LA show: the Tiguan, a compact SUV; and the Touran, a compact minivan. In Germany, the Tiguan and Touran are the most successful cars in their class.
The Tiguan HyMotion fuel cell prototype is VW’s first fuel cell-powered SUV. Compared to earlier prototypes, VW has delivered further performance gains in the fuel cell drive, and its efficiency is better.
The fuel cell stack is a VW-developed high-temperature fuel cell (HTFC) stack which is much more robust than low-temperature, conventional PEM fuel cells (LTFC). LTFC’s will be destroyed if the temperature gets above 80° C while the new system can operate at 120° C and it does not rquire the humidification of the hydrogen and air gases which adds weight and cost.
In the HTFC, proton conduction occurs via phosphoric acid. This acid has electrolytic properties that are as good as those of water, but it exhibits a higher boiling point. Therefore, the HTFC can operate with a considerably less complicated cooling system and water management, thereby reducing weight and costs. The space requirement of the fuel cell system is also reduced by more than 30%. The problem of water permeating the membrane has also been solved by VW with new coatings and elements.
Performance is not the stong point of these prototypes, with the top speed of the Tiguan HyMotion being 87 mph (140 kph), and 0 to 100 kph in about 14 seconds. Power comes from a 100 kW electric motor fed by an 80 kW fuel cell. The fuel cell outputs its generated power to the electric motor via a converter and a downstream inverter.
A 22 kW lithium-ion battery with a charge capacity of 6.8 Ah is recharged via regenerative braking. The battery system is installed in the car’s cargo area under the dual cargo floor that is available on the production Tiguan.
A new 700-bar hydrogen tank is integrated in the space under the rear bench seat and the cargo area. It can hold 3.2 kg of hydrogen—sufficient for a driving range of 125 miles (about 200 km).
The Touran fuel cell prototype also uses the VW-developed stack, but with an 80 kW electric motor. The protoytpe uses a 1.9 kWh NiMH battery instead of a Li-ion battery, due to being designed much earlier than the Tiguan.
Both Tiguan and Touran fuel cell vehicles are currently being tested as part of the California Fuel Cell Partnership. At the same time, other prototypes are running in Germany. For test purposes, an infrastructure of hydrogen filling stations is being built along the test routes between Berlin and Hamburg.
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