Publications

Green hydrogen is considered a highly promising vector for deep decarbonisation of energy systems and is forecast to represent 20% of global energy use by 2050. In order to secure access to this resource Japan Germany and South Korea have announced plans to import hydrogen; other major energy consumers are sure to follow. Ammonia a promising hydrogen derivative may enable this energy transport by densifying hydrogen at relatively low cost using well-understood technologies. This review seeks to describe a global green ammonia import/export market: it identifies benefits and limitations of ammonia relative to other hydrogen carriers the costs of ammonia production and transport and the constraints on both supply and demand. We find that green ammonia as an energy vector is likely to be critical to future energy systems but that gaps remain in the literature. In particular rigorous analysis of production and transport costs are rarely paired preventing realistic assessments of the delivered cost of energy or the selection of optimum import/export partners to minimise the delivered cost of ammonia. Filling these gaps in the literature is a prerequisite to the development of robust hydrogen and ammonia strategies and to enable the formation of global import and export markets of green fuel

Anode recirculation with periodic purge is commonly used in polymer electrolyte fuel cell systems to control the accumulation of nitrogen water and other impurities that are present in the fuel or diffuse through the membrane from the cathode compartment. In this work we develop a simple generalized analytical model that simulates the time dependence of the accumulation of inert impurities in the anode compartment of such a system. It is shown that when there is transport out of the anode chamber the inert species is expected to accumulate exponentially until equilibrium is reached when the rate of inert entering the anode in the fuel supply and/or via crossover from the cathode is balanced by the rate of leakage and/or crossover to the cathode. The model is validated using recently published experimental data for the accumulation of N2 CH4 and CO2 in a recirculated system. The results show that nitrogen accumulation needs to be taken into account to properly adjust system parameters such as purge rate purge volume and recirculation rate. The use of this generalized analytical model is intended to aid the selection of these system parameters to optimize performance in the presence of inerts.

Biogas is one of the most important sources of renewable energy and hydrogen production which needs upgrading to be functional. In this study two methods of biogas upgrading from organic parts of municipal waste were investigated. For biogas upgrading this article used a 3E analysis and simulated cryogenic separation and chemical scrubbing. The primary goal was to compare thermoeconomic indices and create hydrogen by reforming biomethane. The exergy analysis revealed that the compressor of the refrigerant and recovery column of MEA contributed the most exergy loss in the cryogenic separation and chemical scrubbing. The total exergy efficiency of cryogenic separation and chemical scrubbing was 85% and 84%. The energy analysis revealed a 2.07% lower energy efficiency for chemical scrubbing. The capital energy and total annual costs of chemical absorption were 56.51 26.33 and 54.44 percent lower than those of cryogenic separation respectively indicating that this technology is more economically feasible. Moreover because the thermodynamic efficiencies of the two methods were comparable the chemical absorption method was adopted for hydrogen production. The biomethane steam reforming was simulated and the results indicated that this method required an energy consumption of 90.48 MJ kgH2 . The hydrogen production intensity equaled 1.98 kmoleH2 kmolebiogas via a 79.92% methane conversion.

China has become a major market for hydrogen used in fuel cells in the transportation field. It is key to control the cost of hydrogen to open up the Chinese market. The development status and trends of China’s hydrogen fuel industry chain were researched. A hydrogen energy cost model was established in this paper from five aspects: raw material cost fixed cost of production hydrogen purification cost carbon trading cost and transportation cost. The economic analysis of hydrogen was applied to hydrogen transported in the form of high-pressure hydrogen gas or cryogenic liquid hydrogen and produced by natural gas coal and electrolysis of water. It was found that the cost of hydrogen from natural gas and coal is currently lower while it is greatly affected by the hydrogen purification cost and the carbon trading price. Considering the impact of future production technologies raw material costs and rising requirements for sustainable energy development on the hydrogen energy cost it is recommended to use renewable energy curtailment as a source of electricity and multi-stack system electrolyzers as large-scale electrolysis equipment in combination with cryogenic liquid hydrogen transportation or on-site hydrogen production. Furthermore participation in electricity market-oriented transactions cross-regional transactions and carbon trading can reduce the cost of hydrogen. These approaches represent the optimal method for obtaining inexpensive hydrogen.

In the context of a numerical investigation of thermal hazards from two under-expanded hydrogen jet fires results from a newly-developed thermal radiation module of the ADREA-HF computational fluid dynamics (CFD) code were validated against two physical experiments. The first experiment was a vertical under-expanded hydrogen jet fire at 170 bar with the objective of the numerical investigation being to capture the spatial distribution of the radial radiative heat flux at a given time instant. In the second case a horizontal under-expanded hydrogen jet fire at 340 bar was considered. Here the objective was to capture the temporal evolution of the radial radiative heat flux at selected fixed points in space. The numerical study employs the eddy dissipation model for combustion and the finite volume method (FVM) for the calculation of the radiative intensity. The FVM was implemented using a novel angular discretization scheme. By dividing the unit sphere into an arbitrary number of exactly equal angular control volumes this new scheme allows for more flexibility and efficiency. A demonstration of numerical convergence as a function the number of both spatial and angular control volumes was performed.

In recent years increasing concerns regarding the energy costs and environmental effects of urban motorcycle use have spurred the development of hydrogen-electric motorcycles in Taiwan. Although gasoline-powered motorcycles produce substantial amounts of exhaust and noise pollution hydrogen-electric motorcycles are highly energy-efficient relatively quiet and produce zero emissions features that suggest their great potential to reduce the problems currently associated with the use of motorcycles in city environments. This study identified the significant external variables that affect consumers’ purchase intentions toward using hydrogen-electric motorcycles. A questionnaire method was employed with a total of 300 questionnaires distributed and 233 usable questionnaires returned yielding a 78% overall response rate. Structural equation modeling (SEM) was applied to test the research hypothesis. The research concluded that (1) product knowledge positively influenced purchase intentions but negatively affected the perceived risk; (2) perceived quality via hydrogen-electric motorcycles positively influenced the perceived value but negatively affected the perceived risk; (3) perceived risk negatively affected the perceived value; and (4) the perceived value positively affected purchase intentions. This study can be used as a reference for motorcycle manufacturers when planning their marketing strategies.

Dry reforming of hydrocarbons alcohols and biological compounds is one of the most promising and effective avenues to increase hydrogen (H2 ) production. Catalytic dry reforming is used to facilitate the reforming process. The most popular catalysts for dry reforming are Ni-based catalysts. Due to their inactivation at high temperatures these catalysts need to use metal supports which have received special attention from researchers in recent years. Due to the existence of a wide range of metal supports and the need for accurate detection of higher H2 production in this study a systematic review and meta-analysis using ANNs were conducted to assess the hydrogen production by various catalysts in the dry reforming process. The Scopus Embase and Web of Science databases were investigated to retrieve the related articles from 1 January 2000 until 20 January 2021. Forty-seven articles containing 100 studies were included. To determine optimal models for three target factors (hydrocarbon conversion hydrogen yield and stability test time) artificial neural networks (ANNs) combined with differential evolution (DE) were applied. The best models obtained had an average relative error for the testing data of 0.52% for conversion 3.36% for stability and 0.03% for yield. These small differences between experimental results and predictions indicate a good generalization capability.

Dynamic overpressures achieved during the combustion are related to the acceleration experienced by the propagating flame. In the case of premixed turbulent combustion in an obstructed geometry obstacles in the direction of flow result in a complex flame front interaction with the turbulence generated ahead of it. The interaction of flame front and vortex significantly affect the burning rate the rate of pressure rise and achieved overpressure the geometry of accelerating flame front and resulting structures in the flow field. Laboratory-scale premixed turbulent combustion experiments are convenient for the study of flame acceleration by obstacles in higher resolution. This paper presents numerical simulations of hydrogenair mixture combustion experiments performed in the University of Sydney small-scale combustion chamber. The simulations were performed using flameFoam – an open-source premixed turbulent combustion solver based on OpenFOAM. The experimental and numerical pressure evolutions are compared. Furthermore flow structures which develop due to the interaction between the obstacles and the flow are investigated with different obstacle configurations.

To meet the target of reducing greenhouse gas emissions hydrogen as a carbon-free fuel is expected to play a major role in future energy supplies. A challenge with hydrogen is its low density and volumetric energy value meaning that large tanks are needed to store and transport it. By injecting hydrogen into the natural gas network the transportation issue could be solved if the hydrogen–natural gas mixture satisfies the grid gas quality requirements set by legislation and standards. The end consumers usually have stricter limitations on the gas quality than the grid where Euromot the European association of internal combustion engine manufacturers has specific requirements on the parameters: the methane number and Wobbe index. This paper analyses how much hydrogen can be added into the natural gas grid to fulfil Euromot’s requirements. An average gas composition was calculated based on the most common ones in Europe in 2021 and the results show that 13.4% hydrogen can be mixed with a gas consisting of 95.1% methane 3.2% ethane 0.7% propane 0.3% butane 0.3% carbon dioxide and 0.5% nitrogen. The suggested gas composition indicates for engine manufacturers how much hydrogen can be added into the gas to be suitable for their engines.

Hydrogen production using water electrolysers equipped with an anion exchange membrane (AEM) a pure water feed and cheap components such as platinum group metal-free catalysts and stainless steel bipolar plates (BPP) can challenge proton exchange membrane (PEM) electrolysis systems as the state of the art. For this to happen the performance of the AEM electrolyzer must match the compact design stability H2 purity and high current densities of PEM systems. Current research aims at bringing AEM water electrolysis technology to an advanced level in terms of electrolysis cell performance. Such technological advances must be accompanied by demonstration of the cost advantages of AEM systems. The current state of the art in AEM water electrolysis is defined by sporadic reports in the academic literature mostly dealing with catalyst or membrane development. The development of this technology requires a future roadmap for systematic development and commercialization of AEM systems and components. This will include basic and applied research technology development & integration and testing at a laboratory scale of small demonstration units (AEM electrolyzer shortstacks) that can be used to validate the technology (from TRL 2–3 currently to TRL 4–5). This review paper gathers together recent important research in critical materials development (catalysts membranes and MEAs) and operating conditions (electrolyte composition cell temperature performance achievements). The aim of this review is to identify the current level of materials development and where improvements are required in order to demonstrate the feasibility of the technology. Once the challenges of materials development are overcome AEM water electrolysis can drive the future use of hydrogen as an energy storage vector on a large scale (GW) especially in developing countries.