Publications

The transport sector is considered to be a significant contributor to greenhouse gas emissions as this sector emits about one-fourth of global CO2 emissions. Transport emissions contribute toward climate change and have been linked to adverse health impacts. Therefore alternative and sustainable transport options are urgent for decarbonising the transport sector and mitigating those issues. Hydrogen fuel cell vehicles are a potential alternative to conventional vehicles which can play a significant role in decarbonising the future transport sector. This study critically analyses the recent works related to hydrogen fuel cell integration into vehicles modelling and experimental investigations of hydrogen fuel cell vehicles with various powertrains. This study also reviews and analyses the performance energy management strategies lifecycle cost and emissions of fuel cell vehicles. Previous literature suggested that the fuel consumption and well-to-wheel greenhouse gas emissions of hydrogen fuel cell-powered vehicles are significantly lower than that of conventional internal combustion vehicles. Hydrogen fuel cell vehicles consume about 29–66 % less energy and cause approximately 31–80 % less greenhouse gas emissions than conventional vehicles. Despite this the lifecycle cost of hydrogen fuel cell vehicles has been estimated to be 1.2–12.1 times higher than conventional vehicles. Even though there has been recent progress in energy management in hydrogen fuel cell electric vehicles there are a number of technical and economic challenges to the commercialisation of hydrogen fuel cell vehicles. This study presents current knowledge gaps and details future research directions in relation to the research advancement of hydrogen fuel cell vehicles.

It is likely that blending hydrogen into natural gas grids could contribute to economy-wide decarbonization while retaining some of the benefits that natural gas networks offer energy systems. Hydrogen injection into existing natural gas infrastructure is recognised as a key solution for energy storage during periods of low electricity demand or high variable renewable energy penetration. In this scenario natural gas networks provide an energy vector parallel to the electricity grid offering additional energy transmission capacity and inherent storage capabilities. By incorporating green hydrogen into the NG network it becomes feasible to (i) address the current energy crisis (ii) reduce the carbon intensity of the gas grid and (iii) promote sector coupling through the utilisation of various renewable energy sources. This study gives an overview of various interchangeability indicators and investigates the permissible ratios for hydrogen blending with two types of natural gas distributed in Tunisia (ANG and MNG). Additionally it examines the impact of hydrogen injection on energy content variation and various combustion parameters. It is confirmed by the data that ANG and MNG can withstand a maximum hydrogen blend of up to 20%. The article’s conclusion emphasises the significance of evaluating infrastructure and safety standards related to Tunisia’s natural gas network and suggests more experimental testing of the findings. This research marks a critical step towards unlocking the potential of green hydrogen in Tunisia.

Ammonia a molecule that is gaining more interest as a fueling vector has been considered as a candidate to power transport produce energy and support heating applications for decades. However the particular characteristics of the molecule always made it a chemical with low if any benefit once compared to conventional fossil fuels. Still the current need to decarbonize our economy makes the search of new methods crucial to use chemicals such as ammonia that can be produced and employed without incurring in the emission of carbon oxides. Therefore current efforts in this field are leading scientists industries and governments to seriously invest efforts in the development of holistic solutions capable of making ammonia a viable fuel for the transition toward a clean future. On that basis this review has approached the subject gathering inputs from scientists actively working on the topic. The review starts from the importance of ammonia as an energy vector moving through all of the steps in the production distribution utilization safety legal considerations and economic aspects of the use of such a molecule to support the future energy mix. Fundamentals of combustion and practical cases for the recovery of energy of ammonia are also addressed thus providing a complete view of what potentially could become a vector of crucial importance to the mitigation of carbon emissions. Different from other works this review seeks to provide a holistic perspective of ammonia as a chemical that presents benefits and constraints for storing energy from sustainable sources. State-of-the-art knowledge provided by academics actively engaged with the topic at various fronts also enables a clear vision of the progress in each of the branches of ammonia as an energy carrier. Further the fundamental boundaries of the use of the molecule are expanded to real technical issues for all potential technologies capable of using it for energy purposes legal barriers that will be faced to achieve its deployment safety and environmental considerations that impose a critical aspect for acceptance and wellbeing and economic implications for the use of ammonia across all aspects approached for the production and implementation of this chemical as a fueling source. Herein this work sets the principles research practicalities and future views of a transition toward a future where ammonia will be a major energy player.

The global green hydrogen rush is prone to repeat extractivist patterns at the expense of economies ecologies and communities in the production zones in the Global South. With a socio-ecological risk analysis grounded in energy water and environmental justice scholarship we systematically assess the risks of the ‘green’ hydrogen transition and related injustices arising in 28 countries in the Global South with regard to energy water land and global justice dimensions. Our findings show that risks materialize through the exclusion of affected communities and civil society the enclosure of land and resources for extractivist purposes and through the externalization of socio-ecological costs and conflicts. We further demonstrate that socio-ecological risks are enhanced through country-specific conditions such as water scarcity historical continuities such as post-colonial land tenure systems as well as repercussions of a persistently uneven global politico-economic order. Contributing to debates on power inequality and justice in the global green hydrogen transition we argue that addressing hydrogen risks requires a framework of environmental justice and a transformative perspective that encompasses structural shifts in the global economy including degrowth and a decentering of industrial hegemonies in the Global North.

This study evaluates the potential for large-scale green hydrogen production in Indonesia by utilizing renewable energy sources connected on-grid namely 50 MWp of solar panels and 35 MW of wind turbines as well as a hybrid system combining both with a capacity of 45 MW at a grid cost of $100/kWh in five strategic cities: Banyuwangi Kupang BauBau Banjarmasin and Ambon. Using HOMER Pro software various integrated energy system scenarios involving ion exchange membrane electrolysis and alkaline water electrolysis. Additionally the study assumes a project lifespan of 15 years a discount rate of 6.6% and an inflation rate of 2.54%. The results showed that Bau-Bau recorded the highest hydrogen production reaching more than 1.9 million kilograms per year with the lowest levelized cost of hydrogen of $0.65/kg in Scheme 2. On the other hand Kupang shows high costs for most schemes with the levelized cost reaching $1.10/kg. In addition to hydrogen the study also evaluated oxygen production as a by-product of electrolysis. Bau-Bau and Kupang recorded the highest oxygen production with Scheme 6 achieving more than 15 million kilograms per year. The cost of electricity production varies between cities with Banyuwangi having the lowest cost of electricity for wind energy at $80.9/MWh. The net present cost for renewable energy systems in Banyuwangi was $35.4 million for wind turbines while the photovoltaic+wind combination showed the highest cost at $116 million. These findings emphasize the importance of hybrid systems in improving hydrogen production efficiency and supporting sustainable energy transition in Indonesia.

The manner in which an ultra-lean hydrogen flame stabilizes and blows off is crucial for the understanding and design of safe and efficient combustion devices. In this study we use experiments and numerical simulations for pure H2-air flames stabilized behind a cylindrical bluff body to reveal the underlying physics that make such flames stable and eventually blow-off. Results from CFD simulations are used to investigate the role of stretch and preferential diffusion after a qualitative validation with experiments. It is found that the flame displacement speed of flames stabilized beyond the lean flammability limit of a flat stretchless flame (φ = 0.3) can be scaled with a relevant tubular flame displacement speed. This result is crucial as no scaling reference is available for such flames. We also confirm our previous hypothesis regarding lean limit blow-off for flames with a neck formation that such flames are quenched due to excessive local stretching. After extinction at the flame neck flames with closed flame fronts are found to be stabilized inside a recirculation zone.

Meeting climate targets requires profound transformations in the energy system. Most energy uses should be electrified but where this is not feasible hydrogen can be part of the solution. However 98% of global hydrogen production involves greenhouse gas emissions with an average of 12 kg CO2e/kg H2. Therefore new hydrogen production pathways are needed in order to make hydrogen production compatible with climate targets. In this work we fill this gap by systematically comparing the energy and emissions intensity of 173 hydrogen production pathways suitable for the UK. Scenarios include onshore and offshore pathways and the use of repurposed infrastructure. Unlike fossil-fuel based pathways the results show that electrolytic hydrogen powered by fixed offshore wind could align with proposed emissions standards either onshore or offshore. However the embodied and fugitive emissions are important to consider for electrolytic pathways as they result in 10–50% of the total emissions intensity.

The current study seeks to greenhouse gas emissions reduction in an existing engine under dual-fuel combustion fueled with diesel fuel and natural gas due to great concerns about global warming. This simulation study focuses on the identification of areas prone to the formation of greenhouse gas emissions in engine cylinders. The simulation results of dual-fuel combustion confirmed that the possibility of incomplete combustion and the formation of greenhouse gas emissions in high levels are not far from expected. Therefore an efficient combustion strategy along with replacing natural gas with hydrogen was considered. Only changing the combustion mode to reactivity-controlled compression ignition has led to the improvement of the natural gas burning rate and guarantees a 32 % reduction in unburned methane and 50 % carbon monoxide. To further reduce engine emissions while changing the combustion mode a part of natural gas replacement with hydrogen to the complete elimination of it was evaluated. Increasing the share of hydrogen energy in the intake air-natural gas mixture up to 54 % without exhaust gas recirculation does not lead to diesel knock. Moreover improvement of engine load and efficiency can be achieved by up to 18 % and 6 % respectively. Natural gas consumption can be reduced by up to 67 %. Meanwhile the unburned methane and carbon dioxide mass known as greenhouse gas emissions can be reduced to less than 1 % and up to 50 % respectively. Continued replacement of natural gas with hydrogen until its complete elimination guarantees a reduction of 92000 cubic meters of natural gas per year in one engine cylinder. Although the engine efficiency and load face a decrease of 0.8 % and 5.0 % respectively; the amount of carbon dioxide can be decreased by about 4.5 times. Unburned methane carbon monoxide and nitrogen oxides can be reduced to below the relevant EURO VI range while the amount of unburned hydrogen compared to the hydrogen entering the engine is about 0.5 %.

The transformation from a fossil fuel economy to a low-carbon economy has reshaped the way energy is transmitted. As most renewable energy is obtained in the form of electricity using green electricity to produce hydrogen is considered a promising energy carrier. However most studies have not considered the transportation mode of hydrogen. In order to encourage the utilization of renewable energy and hydrogen this paper proposes a comprehensive energy system optimization operation strategy considering multi-mode hydrogen transport. Firstly to address the shortcomings in the optimization operation of existing systems regarding hydrogen transport modeling is conducted for multi-mode hydrogen transportation through hydrogen tube trailers and pipelines. This model reflects the impact of multi-mode hydrogen delivery channels on hydrogen utilization which helps promote the consumption of new energy in electrolysis cells to meet application demands. Based on this the constraints of electrolyzers combined heat and power units hydrogen fuel cells and energy storage systems in integrated energy systems (IESs) are further considered. With the objective of minimizing the daily operational cost of the comprehensive energy system an optimization model for the operation considering multi-mode hydrogen transport is constructed. Lastly based on simulation examples the impact of multi-mode hydrogen transportation on the operational cost of the system is analyzed in detail. The results indicate that the proposed optimization strategy can reduce the operational cost of the comprehensive energy system. Hydrogen tube trailers and pipelines will have a significant impact on operational costs. Properly allocating the quantity of hydrogen tube trailers and pipelines is beneficial for reducing the operational costs of the system. Reasonable arrangement of hydrogen transportation channels is conducive to further promoting the green and economic operation of the system.

A proton exchange membrane (PEM) electrolyzer is fed with water and powered by electric power to electrochemically produce hydrogen at low operating temperatures and emits oxygen as a by-product. Due to the complex nature of the performance of PEM electrolyzers the application of an artificial neural network (ANN) is capable of predicting its dynamic characteristics. A handful of studies have examined and explored ANN in the prediction of the transient characteristics of PEM electrolyzers. This research explores the estimation of the transient behavior of a PEM electrolyzer stack under various operational conditions. Input variables in this study include stack current oxygen pressure hydrogen pressure and stack temperature. ANN models using three differing learning algorithms and time delay structures estimated the hydrogen mass flow rate which had transient behavior from 0 to 1 kg/h and forecasted better with a higher count (>5) of hidden layer neurons. A coefficient of determination of 0.84 and a mean squared error of less than 0.005 were recorded. The best-fitting model to predict the dynamic behavior of the hydrogen mass flow rate was an ANN model using the Levenberg–Marquardt algorithm with 40 neurons that had a coefficient of determination of 0.90 and a mean squared error of 0.00337. In conclusion optimally fit models of hydrogen flow from PEM electrolyzers utilizing artificial neural networks were developed. Such models are useful in establishing an agile flow control system for the electrolyzer system to help decrease power consumption and increase efficiency in hydrogen generation.