Abstract
News on Green Energy and Green Hydrogen is spread on popular and academic media. When energy is obtained from sunlight, wind or water, we call it Green Energy. When hydrogen is obtained from electrolysis with Green Energy, we call it Green Hydrogen. Hydrogen Fuel Cells are electrochemical devices that convert hydrogen and oxygen s chemical energy into electricity and heat energy with high efficiency and contribute to the decarbonisation of the power supply. Bipolar plates, essential components of the fuel cells, made in polymer-carbon composites, are an economical alternative to the stainless steel, titan and graphite, traditional materials. Our experiments have used a polypropylene matrix filled with graphite with a total inorganic content of 87%, which contributes to high electrical and thermic conductivity but strongly influences the viscosity, flow, pressures, temperatures, and then challenging to process. Injection Moulding of thermoplastics is a technology widespread in all fields of activities and considerable potential. In this paper, the experiments design is highlighted in choosing the factors. A debate regarding the filling, packing, holding pressures, and the last decades approach and optimisation of injection moulding parameters with the Taguchi Method is presented. Conclusions on the injection moulding process of the bipolar plate made of a polypropylene-graphite composite, the parameters influence with direct effects on the fuel stack s performance are presented. The combined melt and mould temperatures influence most electrical conductivity by better contacting the electrically conductive particles through the polymer s melted layer. The injection pressure influences the mass and thickness of the product and the electrical conductivity by better packing. Furthermore, we suggest an adapted formula to predict the injection pressure considering the inorganic content and the process temperatures in agreement with the experiments.
Highlights
The bipolar plates are components of the fuel cell stacks, representing about 60% of the total weight and 40% of total costs
Our tests with injection moulding the bipolar plate in polypropylene evidenced the maximum hydraulic injection pressure, php of 30 bar, a specific pressure of 242.22 bar and a measured cavity pressure pc 207.6 bar at a barrel nozzle temperature set 220oC, mould temperature 30oC
Measurements concept We considered simple methods for evaluating the influence of the injection moulding parameters on the electrical conductivity of the bipolar plates: measuring the performance of the fuel cell stack, the product and standard available equipment
Summary
The bipolar plates are components of the fuel cell stacks, representing about 60% of the total weight and 40% of total costs. A high proportion, usually over 70% of graphite, is added to a thermoplastic polymer to obtain a good electrical conductivity of a composite for injection moulding bipolar plates at an industrial scale at economical costs. In this range, there are few works disseminating results. The Taguchi method performed to optimise the injection moulding parameters for better conductivity of a polymer composite bipolar plate and the influence of the bipolar plate on the power efficiency of the hydrogen-air PEM fuel cell are presented. In the injection moulding process, quality characteristics such as reject rate, flash, or porosity have traditionally been measured Taguchi method uses Smaller-the-Better, Nominal-the-Better and Larger-the-Better [11,12]
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