The local saturation in porous transport layers (PTL) has been determined using synchrotron-based x-ray micro-tomography. The water distribution inside the porous structure could be resolved on the scale of the pores. After phase segmentation of the image data, the measurement of the liquid saturation as function of the through plane coordinate of the PTL and the capillary pressure was possible. For verification, first experiments with complete cells are also shown.

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This paper proposes a way to investigate the II. THE VEHICLE AND THE POWERTRAIN benefit of hybridising a fuel cell vehicle with a second energy source such as batteries or supercapacitors packs. A global Thevehicle considered forthis study is a sedan car such optimisation algorithm based on optimal control theory is as the VW Bora Hy-Power fuel cell hybrid vehicle [2]. proposed to determine an efficient power splitting between the Its main parameters are summarized in Table 1. fuel cell system (FCS) and the energy storage system (ESS). Both hybridisation and control strategy should minimise the TABLE 1 hydrogen consumption for a given driving cycle. This method VEHICLE PARAMETERS has fast computation time, and as a consequence many Vehicle total mass 2021 kg simulations can be performed within a short period, thus providing an interesting tool to test and compare different degree of hybridisation for various fuel cell hybrid vehicle Frontal area 2.1 m2 (FCHV) parameters and driving cycles. Gear ratio 8 Gear efE1ciency~9500 Index Terms -Fuel Cell Hybrid Vehicle, supercapacitor, Gear efficiency global optimisation, optimal control, state constraint. Cr =Cro + kc V(t), Rolling resistance [6]Cr = 0.0136, kc = 4*1 0-7 kM-1 *h

We have demonstrated earlier the useful performance of our PSI radiation-grafted membranes in terms of the current-voltage characteristics of 30 cm2 active area fuel cells containing these membranes and their long-term testing over 6,000 h at 60 °C. We report here on testing of PSI radiation-grafted membranes in these fuel cells at 80 °C and in short stacks comprised of two or four 100 cm2 active area cells. The in-situ degradation of membranes has been investigated by characterizing membranes both before testing in fuel cells and post-mortem after testing in fuel cells. Characterization was accomplished by means of ion-exchange capacity and infrared and Raman spectroscopic measurements. In addition, a rapid screening method for our ex-situ testing of the oxidative stability of proton-conducting membranes was developed in this work. Comparison of the initial screening test results concerning the oxidative stability of some perfluorinated, partially-fluorinated, and non-fluorinated membranes compare well qualitatively with the relative stability of these same membranes during their long-term testing in fuel cells.

A microporous layer (MPL) is typically added to gas diffusion layers in polymer electrolyte fuel cells (PEFC) to enhance fuel cell performance and water management. The related transport mechanisms are not completely understood and therefore characterization is required. However accurate determination of MPL liquid water saturation has not yet been broadly addressed, except for preliminary work. We demonstrate that X-ray computed tomography (XCT) is suitable and efficient in characterizing MPL’s local liquid water saturation in an ex situ model experiment setup. Our image evaluation pipeline was first developed on porous polymeric membrane materials, validated by independent gravimetric measurements. Mercury intrusion porosimetry (MIP) on MPL further justifies the efficacy of the method. The pipeline has indicated an accuracy of ca. ±7% and a field of view of 6 mm, which suits differential cell investigations. The linear relationship of greyscale value (GSV) and linear attenuation coefficients is shown to hold even for a polychromatic radiation source. This methodology has the potential to accurately characterize the water saturation in MPLs under operando PEFC conditions.