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With the growing demand for green technologies, hydrogen energy devices, such as Proton Exchange Membrane (PEM) fuel cells and water electrolysers, have received accelerated developments. However, the materials and manufacturing cost of these technologies are still relatively expensive which impedes their widespread commercialization. Additive Manufacturing (AM), commonly termed 3D Printing (3DP), with its advanced capabilities, could be a potential pathway to solve the fabrication challenges of PEM parts. Herein, in this paper, the research studies on the novel AM fabrication methods of PEM components are thoroughly reviewed and analysed. The key performance properties, such as corrosion and hydrogen embrittlement resistance, of the additively manufactured materials in the PEM working environment are discussed to emphasise their reliability for the PEM systems. Additionally, the major challenges and required future developments of AM technologies to unlock their full potential for PEM fabrication are identified. This paper provides insights from the latest research developments on the significance of advanced manufacturing technologies in developing sustainable energy systems to address the global energy challenges and climate change effects. • The AM technologies relevant to PEM fabrication are reviewed. • Corrosion performance of AM materials in the PEM working environment is presented. • The challenges and prospects of AM for PEM fabrication are discussed. • AM has the potential to revolutionize the fabrication of PEM systems. [ABSTRACT FROM AUTHOR]

The demand for clean power source which can be used to run the various types of vehicles on the road is increasing on a daily basis due to the fact that high emissions released from internal combustion engine play a significant role in air pollution and climate change. Fuel cell devices, particularly Proton Exchange Membrane (PEM) type, are strong candidates to replace the internal combustion engines in the transport industry. The PEMFC technology still has many challenges including high cost, low durability and hydrogen storage problems which limit the wide-world commercialization of this technology. In this paper, the fuel cell cost, durability and performances challenges which are associated with using of fuel cell technology for transport applications are detailed and reviewed. Recent developments that deal with the proposed challenges are reported. Furthermore, problems of hydrogen infrastructure and hydrogen storage in the fuel cell vehicle are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The current climate crisis and recent world events, including the global economic crisis and growing concerns over the availability and cost of petroleum fuels, has sparked a global interest in developing alternative, sustainable, clean fuel technologies for the transportation sector. While a multitude of alternative fuel and vehicle technologies have been presented, hydrogen is considered by many as an option of choice. However, the mass-adoption of hydrogen presents many challenges, including appropriate refueling infrastructure supply transitions, consumer vehicle purchase behavior, and fuel costs. Early fleet adoption is one proposed strategy to transition hydrogen use in the transportation sector. Bus-transit demonstration projects have proven the technology, yet there has not been large-scale adoption by transit fleets. This paper addresses infrastructure, vehicle, and personnel needs to support the transition of a medium sized transit agency to full conversion to hydrogen fuel, using Knoxville Area Transit (KAT) as a case study. Specifically, requirements for hydrogen bus fleets, production, storage, refueling and maintenance facilities, and personnel are addressed as well as the transition strategy for implementing the technology. [Copyright &y& Elsevier]

Abstract: Energy production and combating climate change are among some of the most significant challenges we are facing today. Whilst the introduction of a hydrogen economy has its merits, the associated problems with on-board hydrogen storage are still a barrier to implementation. Ammonia and related chemicals may provide an alternative energy vector. Besides ammonia and metal amine salts, some other ammonia related materials such as hydrazine, ammonia borane, ammonia carbonate and urea also have the potential for use as alternative fuels. These materials conform to many of the US DOE targets for hydrogen storage materials. Similar to hydrogen, ammonia itself is carbon-free at the end users, although CO2 emission on production of ammonia is dependent on the source of energy. Both hydrogen and ammonia utilised similar energy sources for production: fossil fuels, biomass, renewable electricity, nuclear and solar energy. While a number of papers have been published on the catalytic decomposition of ammonia or related chemicals to produce hydrogen, the use of fuel cells directly fed by ammonia and related chemicals would have a higher efficiency. In recent years significant progress has been made on direct ammonia, hydrazine and urea fuel cells to generate electricity from these materials for transport applications. With the development and application in these technologies, reduction of CO2 emissions in transportation would be possible. In this review, we propose the use of ammonia and related chemicals as potential indirect hydrogen storage materials. The progress on fuel cells using these fuels is also briefly reviewed. [Copyright &y& Elsevier]

Abstract: Fuel economy and emission abatement are issues, which are highly prioritized areas in the automotive industry of today. The debate about climate change has in recent years even more emphasized the importance of these issues and has increased the search for finding sustainable technical solutions. This paper describes an effort to develop an innovative and environmentally-benign hydrogen generation system operating on commercial diesel fuel to avoid running the engine to supply electricity at stand-still. The use of a fuel cell-based auxiliary power unit (APU) has the potential of delivering electricity at high efficiencies independent of the heavy-duty truck engine. During the reformer development phase, spray formation and mixing of reactants proved to be crucial to obtain high reforming efficiencies and low diesel slip. The diesel is being injected through a nozzle creating a spray of fine droplets of a size which can establish rapid evaporation. Air and steam are being pre-heated and injected into the mixture chamber and subsequently mixed with the evaporated diesel fuel. Depending on the operating parameters, a part of the fuel is being oxidized and produces heat. Autothermal reforming was chosen to circumvent the heat transfer problem in catalytic steam reforming. By supplying heat directly to the catalyst surface by an oxidation reaction the heat demand of the strongly endothermic steam reforming reaction can be fulfilled. We employed CFD calculations, which revealed the importance of avoiding large recirculation zones leading to a prolonged residence time of the hydrocarbon molecules and causing auto-ignition and excessive temperatures in the catalyst. Five different reformer generations are being described and discussed in detail in this publication. The first one was based on a fixed bed reactor, while the other four all relied on catalytic monoliths enabling low pressure drops. The early reactor designs all suffered from auto-ignition and instability problems. The latter generations exhibited a considerably more stable temperature profile in the reformer. The conversion of diesel and the reformer efficiencies are significantly higher than the early generation diesel reformers. [Copyright &y& Elsevier]