Fuel cells are electrochemical devices that convert the chemical energy of a reactants directly into electricity and heat with high efficiency. Proton Exchange Membrane or Polymer Electrolyte Membrane (PEM) fuel cells are one of the most common type of fuel cells. In a convection PEM fuel cell, the oxygen from air is introduced to the cathode and hydrogen is introduced to anode. Between the anode and cathode electrodes is sandwiched the polymer electrolyte membrane. The hydrogen molecules break apart into protons and electrons due to the reaction helped by catalysts. The protons travel through the membrane to the cathode and electrons travel to an external circuit. At cathode side the protons, electrons and oxygen molecules combine to form water. Research work was directed to the study of hydrogen fuel cell power systems for portable applications. Last decade the industry developed portable power systems based on hydrogen fuel cell, mobile telephone chargers, vehicles energy supply. In this paper are presented the experiments with a hydrogen fuel cell stack in which were assembled resin filled graphite bipolar plates and then injection moulded polymeric conductive composite bipolar plates and results were compared concluding that injection moulded bipolar plates could represent an attractive alternative in building efficient fuel cell portable power systems.
All components contribute to the total electrical resistance in the fuel cell including the bipolar plates (BP). Contact interface between BP and gas diffusion layers (GDL) can influence the voltage losses. It is usually assumed the real contact area of two metal surfaces is determined by the plastic deformation of their highest asperities. The contact deformation of the polymer composite BP and GDL made of graphite paper or graphite cloth, is depending on the complex topography of the surfaces which touch elastically and plastically and on the clamping force the stack. This paper presents the analysis of the influence of microstructures of the BP surfaces on the voltage losses and directly affecting the performance of the fuel cells. For same model of the BP made by injection molding in a conductive poly(propylene) matrix composite, the mold cavities surface microstructure of the gas flow fields have been manufactured by micro-milling at two different roughness Ra of 0.77 µm (first type) and then, laser ablation at respectively Ra of 9.9 µm (second type). Voltage loss through the BP and membrane electrodes assembly have been investigated at different clamping forces the stack.
Fuel cells are electrochemical devices that convert chemical energy of fuels into electrical energy. Fuel cells were used in NASA space programs to generate energy to satellites and space capsules. Today fuel cells are used to power vehicles including automobiles, forklifts, buses, boats, motorcycles or submarines. Bipolar plates are components of the fuel cell stack and must be highly electrically conductive to obtain a good voltage across the stack and highly thermally conductive to help cooling. Bipolar plates were made of graphite and stainless steel to which additional surface treatments were added to improve properties. In order to reduce the costs of bipolar plates researchers were looking for alternatives: polymeric thermosets and thermoplastics composites. In our paper we analyse the composites polyethylene-carbon and polypropylene-carbon for which we investigated the mechanical properties for the compression-moulded samples. The mechanical, the electrical properties and flow length and the cavity pressure were analysed for the injection moulding in polyethylene-carbon with micro-profiles of 0.5mm x 0.2mm.
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