Publications

Liquid hydrogen has attracted much attention due to its high energy storage density and suitability for long-distance transportation. An efficient hydrogen liquefaction process is the key to obtaining liquid hydrogen. In an effort to determine the parameter optimization of the hydrogen liquefaction process this paper employed process simulation software Aspen HYSYS to simulate the hydrogen liquefaction process. By establishing a dynamic model of the unit module this study carried out dynamic simulation optimization based on the steady-state process and process parameters of the hydrogen liquefaction process and analyzed the dynamic characteristics of the process. Based on the pressure drop characteristic experiment an equation for the pressure drop in the heat exchanger was proposed. The heat transfer of hydrogen conversion was simulated and analyzed and its accuracy was verified by comparison with the literature. The dynamic simulation of a plate-fin heat exchanger was carried out by coupling heat transfer simulation and the pressure drop experiment. The results show that the increase in inlet temperature (5 C and 10 C) leads to an increase in specific energy consumption (0.65 % and 1.29 % respectively) and a decrease in hydrogen liquefaction rate (0.63 % and 2.88 % respectively). When the inlet pressure decreases by 28.57 % the hydrogen temperature of the whole liquefaction process decreases and the specific energy consumption increases by 52.94 %. The research results are of great significance for improving the operating efficiency of the refrigeration cycle and guiding the actual liquid hydrogen production.

Disposing of plastic waste through burial or burning leads to air pollution issues while also contributing to gas emissions and plastic waste spreading underground into seas via springs. Henceforth this research aims at reducing plastic waste volume while simultaneously generating clean energy. Hydrogen energy is a promising fuel source that holds great value for humanity. However achieving clean hydrogen energy poses challenges including high costs and complex production processes especially on a national scale. This research focuses on Iran as a country capable of producing this energy examining the production process along with related challenges and the general supply chain. These challenges encompass selecting appropriate raw materials based on chosen technologies factory capacities storage methods and transportation flow among different provinces of the country. To deal with these challenges a mixed-integer linear programming model is developed to optimize the hydrogen supply chain and make optimal decisions about the mentioned problems. The supply chain model estimates an average cost—IRR 4 million (approximately USD 8)—per kilogram of hydrogen energy that is available in syngas during the initial period; however subsequent periods may see costs decrease to IRR 1 million (approximately USD 2) factoring in return-on-investment rates.

This paper describes a model of hydrogen blowdown dynamics for storage tanks needed for hydrogen safety engineering to accurately represent incident scenarios. Heat transfer through a tank wall affects the temperature and pressure dynamics inside the storage vessel and therefore the characteristics of the resulting hydrogen jet in case of loss of containment. Available non-adiabatic blowdown models are validated only against experiments on hydrogen storages at ambient temperature. Effect of heat transfer for cryo-compressed hydrogen can be more significant due to a larger temperature difference between the stored hydrogen and surrounding atmosphere especially in case of failure of equipment insulation. Previous work by the authors demonstrated that the heat transfer through a discharge pipe wall can significantly affect the mass flow rate of cryogenic hydrogen releases. To the authors’ knowledge thoroughly validated models of non-adiabatic blowdown dynamics for cryo-compressed hydrogen are currently missing. The present work further develops the non-adiabatic blowdown model at ambient temperature using the under-expanded jet theory developed at Ulster University to expand it to cryo-compressed hydrogen storages. The non-ideal behaviour of cryo-compressed hydrogen is accounted through the high-accuracy Helmholtz energy formulations. The developed model includes effect of heat transfer at both the tank and discharge pipe wall. The model is thoroughly validated against sixteen tests performed by Pro-Science on blowdown of hydrogen storage tanks with initial pressure 0.5-20 MPa and temperature 80-310 K through release nozzle of diameter 0.5-4.0 mm. The model well reproduces the experimental pressure and temperature dynamics during the entire blowdown duration.

Maritime and aviation transport are widely recognised as sectors where reducing greenhouse gas emissions is particularly challenging due to their reliance on energy-dense fuels and the challenges associated with direct electrification. These sectors face increasing pressure to defossilise and reduce emissions in line with global climate goals while simultaneously facing unique technological operational and economic uncertainties. This study addresses a key research gap by comparing the maritime and aviation sectors for common factors and sector-specific differences in their transition to green e-fuels produced from renewable electricity and sustainable CO2. A techno-economic assessment is conducted to evaluate alternative fuel and propulsion options using the levelised cost of mobility framework. The analysis also incorporates the pricing of non-CO2 greenhouse gases and air pollutant emissions. Results show that e-ammonia or e-LNG combustion is the most cost-effective option for maritime transport when emission costs are excluded whereas hydrogen fuel cells become more economical when these costs are internalised. In aviation e-kerosene use in conventional aircraft presents the lowest costs regardless of the year or emission pricing. The findings highlight the importance of considering unique characteristics of each sector and tailored defossilisation and decarbonisation strategies that consider sector-specific constraints. To sustainably meet the growing demand for transport fuels rapid investments in renewable electricity generation electrolysers and e-fuel synthesis are essential. Development of strong regulatory frameworks and financial instruments will be critical to support early deployment of e-fuels and minimise the risks.

In Southern Italy near the Mediterranean Sea mobility services like cars bicycles scooters and materialhandling forklifts are frequently required in addition to multimodal local transportation services such as trains ferry boats and airplanes. This research proposes an innovative concept of hydrogen valley virtually simulated in Matlab/Simulink environment located in Calabria. As a novelty hydrogen is produced centrally and delivered via fuel cell hybrid trains to seven hydrogen refueling stations serving various mobility hubs. The centralized production facility operates with a nominal capacity of about 4 tons/day producing hydrogen via PEM electrolysis and storing hydrogen at 200 bar with a hydrogen compressor. As the size of vehicle fleets and the cost of acquiring renewable energy through power purchase agreements vary the hydrogen valley is examined from both a technical and an economic perspective analyzing: the values of the levelized cost of hydrogen the energy consumption and the energy efficiency of the energy systems. Specifically the levelized cost of hydrogen reached competitive values close to 5 €/kg of hydrogen under the most optimistic scenarios with fleet conversions of more than 60 % and a power purchase agreement price lower than 150 €/MWh. Then the benefits of hydrogen rail transport in terms of emissions reduction and health from an economic standpoint are compared to conventional diesel trains and fully electric trains saving respectively 3.2 ktons/year and 0.4 ktons/year of carbon dioxide equivalent emissions and corresponding economic benefits of respectively 51 and 0.548 million euros.

As a clean and renewable energy carrier hydrogen is one of the most promising alternative fuels. Cryogenic compressed hydrogen can achieve high storage density without liquefying hydrogen which has good application prospects. Investigation of the safety problems of cryogenic compressed hydrogen is necessary before massive commercialization. The present study modeled the instantaneous flow field using the Large Eddy Simulation (LES) for cryogenic (50 and 100 K) underexpanded hydrogen jets released from a round nozzle of 1.5 mm diameter at pressures of 0.5-5.0 MPa. The simulation results were compared with the experimental data for validation. The axial and radial concentration and velocity distributions were normalized to show the self-similar characteristics of underexpanded cryogenic jets. The shock structures near the nozzle were quantified to correlate the shock structure sizes to the source pressure and nozzle diameter. The present study on the concentration and velocity distributions of underexpanded cryogenic hydrogen jets is useful for developing safety codes and standards.

In this study a novel thermo-economic analysis on a membrane reactor adopted to generate hydrogen coupled to a carbon-dioxide capture system is proposed. Exergy destruction fuel and environmental as well as pur chased equipment costs have been accounted to estimate the cost of hydrogen production in the aforementioned integrated plant. It has been found that the integration of the CO2 capture system with the membrane reactor is responsible for the reduction of the hydrogen production cost by 12 % due to the decrease in environmental penalty cost. In addition the effects of operating parameters (steam-to-carbo ratio and biogas temperature) on the hydrogen production cost are investigated. Hence this work demonstrates that the latter can be decreased by approximately 2 $/kgH2 when steam to carbon ratio increases from 1.5 to 4. The analyses reveal that steam-tocarbo ratio increases exergy destruction cost affecting consequently also the hydrogen production cost. How ever from a thermodynamic point of view it enhances the hydrogen production in the membrane reactor mutually lowering the hydrogen production cost. It has been also estimated that a decrease in the biogas inlet temperature from 450 to 400◦C can reduce the hydrogen production cost by 7 %. This study demonstrates that the fuel cost is a major economic parameter affecting commercialization of hydrogen production while exergy destruction and environmental costs are also significant factors in determining the hydrogen production cost.

Transforming Europe into a climate neutral economy and society by 2050 requires extraordinary efforts and the mobilisation of all sectors and economic actors coupled with all the creative and brain power one can imagine. Each sector has to fundamentally rethink the way it operates to ensure it can be transformed towards this new net-zero paradigm without jeopardising other environmental and societal objectives both within the EU and globally. Given the scale of the transformation ahead our ability to meet climate neutrality targets directly depends on our ability to innovate. In this context Research & Innovation programmes have a key role to play and it is crucial to ensure they are fit for purpose and well equipped to support the next wave of breakthrough innovations that will be required to achieve climate neutrality in the EU and globally by 2050. The objective of this study is to contribute to these strategic planning discussions by not only identifying high-risk and high-impact climate mitigation solutions but most importantly look beyond individual solutions and consider how systemic interactions of climate change mitigation approaches can be integrated in the development of R&I agendas.

Hydrogen is experiencing a resurgence in energy transition debates. Before representing a solution however the existing hydrogen economy is still a climate change headache: over 99 % of production depends on fossil fuels oil refining accounts for 42 % of demand and its transportation is intertwined with fossil infrastructure like natural gas pipelines. This article investigates the path-dependent dynamics shaping the hydrogen economy and its interconnections with the oil and gas industry. It draws on the global production networks (GPN) approach and political economy research to provide a comprehensive review of current and prospective enduses of hydrogen modes of transport networks of industrial actors and state strategies along the major production facilities and holders of intellectual property rights. The results presented in this article suggest that the superimposition of private agendas may jeopardise the viability of future energy systems and requires counterbalancing forces to override the negative consequences of path-dependent energy transitions.

Carbon dioxide and hydrogen storage in geological formations at Gt scale are two promising strategies toward net-zero carbon emissions. To date investigations into underground hydrogen storage (UHS) remain relatively limited in comparison to the more established knowledge body of underground carbon dioxide storage (UCS). Despite their analogous physical processes can be used for accelerating the advancements in UHS technology the existing distinctions possibly may hinder direct applicability. This review therefore contributes to advancing our fundamental understanding on the key differences between UCS and UHS through multi-scale comparisons. These comparisons encompass key factors influencing underground gas storage including storage media trapping mechanisms and respective fluid properties geochemical and biochemical reactions and injection scenarios. They provide guidance for the conversion of our existing knowledge from UCS to UHS emphasizing the necessity of incorporating these factors relevant to their trapping and loss mechanisms. The article also outlines future directions to address the crucial knowledge gaps identified aiming to enhance the utilisation of geological formations for hydrogen and carbon dioxide storage.