Scaling factors for channel width variations in treelike flow field patterns for polymer electrolyte membrane fuel cells - An experimental study

To have a uniform distribution of reactants is an advantage to a fuel cell. We report results for such a distributor with tree-like flow field plates (FFP). Numerical simulations have shown that the width scaling parameters of tree-like patterns in FFPs used in polymer electrolyte membrane fuel cells (PEMFC) reduces the viscous dissipation in the channels. In this study, experimental investigations were conducted on a 2-layer FF plate possessing a tree-like FF pattern which was CNC milled on high-quality graphite. Three FF designs of different width scaling parameters were employed. IeV curves, power curves and impedance spectra were generated at 70%, 60% and 50% relative humidity (25 cm2 active area), and compared to those obtained from a conventional 1-channel serpentine FF. It was found that the FF design, with a width scaling factor of 0.917 in the inlet and 0.925 in the outlet pattern, exhibited the best peak power out of the three designs (only 11% - 0.08 W/cm2 lower than reference serpentine FF). Results showed that a reduction of the viscous dissipation in the flow pattern was not directly linked to a PEMFC performance increase

The role of hydrogen and fuel cells in the global energy system

Hydrogen technologies have experienced cycles of excessive expectations followed by disillusion. Nonetheless, a growing body of evidence suggests these technologies form an attractive option for the deep decarb onisation of global energy systems, and that recent improvements in their cost and performance point towards economic viability as well. This paper is a comprehensive review of the potential role that hydrogen could play in the provision of electricity, h eat, industry, transport and energy storage in a low - carbon energy system, and an assessment of the status of hydrogen in being able to fulfil that potential. The picture that emerges is one of qualified promise: hydrogen is well established in certain nic hes such as forklift trucks, while mainstream applications are now forthcoming. Hydrogen vehicles are available commercially in several countries, and 225,000 fuel cell home heating systems have been sold. This represents a step change from the situation of only five years ago. This review shows that challenges around cost and performance remain, and considerable improvements are still required for hydrogen to become truly competitive. But such competitiveness in the medium - term future no longer seems an unrealistic prospect, which fully justifies the growing interest and policy support for these technologies around the world

Power-to-X and power-to-power routes

The increasing dependence on a worldwide scale of the power generation sector on non-dispatchable renewable sources, such as wind or solar, is posing challenges to the electricity infrastructures that require flexibility solutions to keep the balance between power supply and demand. Flexible generation, energy storage, demand side response are among the several strategies pursued to increase the flexibility of electricity management in the presence of a large share of RES generation, but flexibility can also derive by the conversion of electricity to other energy commodities. Among the secondary energy carriers, electricity can be stored in the form of chemical potential following the so-called “Power-to-X” scheme. In this route, electricity is converted in energy carriers, such as hydrogen, that can be exploited not only for time-shifted power delivery (“X-to-Power” reverse scheme), but also employed to cover nonelectrical demand in different sectors, such as transportation, heating, and industry. This chapter provides a detailed description of the different routes in the Power-to-X scheme, highlighting the technologies, the benefits and services provided to the energy system, the strengths and criticality points, the possible applications of the output streams, and the lessons learned from projects and demonstrations worldwide