Technology Status of Hydrogen Road Vehicles

design requirements derived from safety considerations. The overall project examined included the facilities
of large-scale LH 2 transportation (115,000 m 3 tanker with 40-MW H 2 power plant), storage (1,000 tonnes LH 2)
and distribution, and use (10 MW FC; 150 LH 2 bus depot) in the port and city of Hamburg.
The safety analyses in question are HAZOPS-style, before the P&I drawings have progressed enough to justify
a full-blown fault tree approach. Preliminary flow sheets and process/function descriptions are required to
some minimum level to allow concrete assessments, and especially to reveal weak points relatively easy to
correct early on. Experience and expert judgement are required, and outsiders should join the insiders in the
analyses.
Although the paper concentrates on the 40-MW power plant, the results for the other three indicate that they
can be constructed from a safety viewpoint in Hamburg, and that in general design improvements derived from
purely safety considerations lead also to operational benefits in the form of higher reliability and availability.
TOPIC 6: Fundamentals
Giesenger, A., et al., “Zeolite Powders as Hydrogen Storage Materials: Measurements and Theoretical
Modelling of Thermophysical Properties,” University of Stuttgart, Germany, pp. 2513-2522.
Zeolites are highly porous crystalline aluminosilicates, whose crystal structure with pores and cages enables
the reversible encapsulation of guest molecules. Present uses are as molecular sieves and drying mediums,
and recently for H 2 storage where the H 2 molecules are forced into the zeolite cages at 30 bar and 600 K.
Reheating the loaded zeolite releases the H 2. The effective thermal conductivity of the zeolite powder strongly
influences the velocity of adsorbing and desorbing hydrogen. The specific heat is a measure of the zeolite
water content whose presence inhibits H 2 uptake.
The paper describes measurements of the thermal conductivity and specific heat, and their comparison with
theoretical models. The application of the measurement techniques to synthetic zeolites with better H 2 storage
capability is mentioned.
Fischer, A., et al., “Comparing different production technologies for Proton-Exchange-Membrane Fuel
Cells,” Technische Hochschule Darmstadt, Germany, pp. 2523-2530.
This paper was erroneously reproduced under Topic 6, and should be under Topic 4.
It deals with the influence of the production technology on electrode porosity and FC performance, and shows
the importance of coarse pores for thin film electrodes.
With H 2 at the anode, the catalysts cannot tolerate more than 10 ppm CO; with air instead of O 2 at the cathode
the N accumulation there creates a barrier for O 2, so the electrode porosity is important to performance. To
show this experimentally, the membrane/electrode assemblies were produced either by hot pressing platinized
carbon percolated with Nafion as electrode material on Nafion 117 membranes, or by spraying an
electrocatalyst slurry on to the heated membrane with subsequent drying; an additional porosity was
implemented by adding fillers to the electrocatalyst slurry.
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