Publications

Different photoelectrochemical (PEC) artificial-leaf systems have been proposed for green hydrogen production. However their sustainability is not well understood in comparison to conventional hydrogen technologies. To fill this gap this study estimates cradle-to-grave life cycle environmental impacts and costs of PEC hydrogen production in different provinces in China using diverse tandem solar cells: Ge/GaAs/GaInP (Ge-PEC) GaAs/ GaInAs/GaInP (GaAs-PEC) and perovskite/silicon (P-PEC). These systems are benchmarked against conventional hydrogen production technologies − coal gasification (CG) and steam methane reforming (SMR) − across 18 environmental categories life cycle costs and levelised cost of hydrogen (LCOH). P-PEC emerges as the best options with 36–95 % lower impacts than Ge-PEC and GaAs-PEC across the categories including the climate change impact (0.38–0.52 t CO2 eq./t H2) which is 77–79 % lower. Economically P-PEC shows 81–84 % lower LCOH (2.51–3.81 k$/t). Compared to SMR and CG P-PEC reduces the impacts by 23–98 % saving 3.67–38.5 Mt of CO2 eq./yr. While its LCOH is 5 % higher than that of conventional hydrogen it could be economically competitive with both SMR and CG at 10 % higher solar-to-hydrogen efficiency and 25 % lower operating costs. In contrast Ge-PEC and GaAs-PEC while achieving much lower (81–91 %) climate change and some other impacts than the conventional technologies face significant economic challenges. Their LCOH (21.51–32.82 k$/t for Ge-PEC and 16.96–25.89 k$/t for GaAs-PEC) is 7–9 times higher than that of the conventional hydrogen due to the high solar cell costs. Therefore despite their environmental benefits these technologies require substantial cost reductions to become economically viable.

Hydrogen valleys are envisaged (imagined) integrated industrial systems where hydrogen is produced stored and utilized. Here we show how hydrogen valleys as sociotechnical imaginaries are differentiated in terms of their specific configurations but homogenous in terms of reflecting the interests of large industrial fossil fuel suppliers and consumers. This path dependence is anticipated in sociotechnical transitions theory which emphasises the power of incumbents with vested interests to maintain basic templates or regimes of production and consumption. The simultaneously heterogeneous and homogenous nature of hydrogen valley imaginaries can be thought of as a form of glocalisation for which we draw on Roudometof's theory of glocalisation as involving the local refraction of diffusing global tendencies. To illustrate this we compare two hydrogen valleys one in the north of the Netherlands and one in southern Spain. In the north Netherlands the hydrogen valley imaginary comprises use of offshore windpower to electrolyse hydrogen for transport fuel and as feedstock to heavy industry in proximate regions including northern Germany and Belgium. This is consistent with existing gas distribution networks connecting industrial consumers. In the southern Spanish case the imaginary positions Spain as a major exporter of green hydrogen to the rest of Europe via onshore renewable electrolysis with export including via ocean tankers and chemical refining in existing infrastructure in Rotterdam. Overall the study explores empirically theoretically-informed themes concerning the interrelationship of mutually supportive local and global imaginaries – hence our term glocalised imaginaries.

Hydrogen economy is spreading across the maritime sector in response to increasingly stringent regulations for shipping emissions. The challenging on-board hydrogen logistics are often mitigated with hydrogen carriers such as methanol. Research on methanol reforming to hydrogen for fuel cell feed is conducted mostly in steady state overlooking dynamic reactor operation and its effects on the power production system. Forced reactor operations induce fluctuations of CO content in the reformate potentially harmful to the PEM fuel cell and drops in methanol conversion causing inefficient operation. In present research simulations with a physical 2D unsteady model of a packed bed methanol steam reforming reactor resulted in methanol conversion drop durations of up to a minute. Additionally temporary increases of CO content up to 112% were observed. Throughput ramp ups most notably impact the conversion while ramp downs negatively affect selectivity. The investigation on reactor geometry concludes that larger tube diameters increase transient time and CO spikes while they decrease with reactor length. Amplified unsteady effects are also observed with larger changes in input process variables. The results imply that heat transfer rate to the reactor are most often the detrimental factor for transient effects and durations in practice. Following this work inclusion of realistic heating methods is recommended instead of uniform tube temperatures used in present simulations. Heating system characteristics are necessary for realistic evaluation of the methanol reformer constraint on fuel cell feed demand in fully integrated systems.

Hydrogen tanks (HT) with different connection modes are an integral part of the shipborne hydrogen fuel cell system. To ensure the safe and reliable operation of the shipborne multi-tank cascade system this study innovatively develops 3D models of four different connection modes for the shipborne multi-tank cascade system namely Type-22 Type-211 Type-121 and Type-112. Through computational fluid dynamics (CFD) numerical simulation the variations in parameters of different multi-tank cascade systems during the hydrogen storage process are analyzed. The results indicate that the maximum temperature of Type-112 is 271.107K which is 2.220% 4.779% and 3.993% lower than that of Type-22 Type-211 and Type-121 respectively and thus the optimal parameters such as the initial temperature in the tank and pre-cooling temperature are derived. Type-112's maximum temperature is reduced by 14.02% and 16.66% compared to systems connected solely in series or in parallel. The study identifies the optimal structure and reasonable hydrogen storage parameters effectively reducing heat generation during the refueling process while optimizing space utilization thereby strongly ensuring the stability of hydrogen storage and opening up new avenues for addressing related hydrogen storage issues in the future.

Mobility has been a prominent target for proponents of the hydrogen economy. Given the complexities involved in the mobility value chain actors hoping to participate in this nascent market must overcome a range of challenges relating to the availability of vehicles the co-procurement of supporting infrastructure a favourable regulatory environment and a supportive community among others. In this paper we present a state-of-play account of the nascent hydrogen mobility market in Victoria Australia drawing on data from a workshop (N ¼ 15) and follow-up interviews (n ¼ 10). We interpret findings through a socio-technical framework to understand the ways in which fuel cell electric vehicles (FCEVs)dand hydrogen technologies more generallydare conceptualised by different stakeholder groups and how these conceptualisations mediate engagement in this unfolding market. Findings reveal prevailing efforts to make sense of the FCEV market during a period of considerable institutional ambiguity. Discourses embed particular worldviews of FCEV technologies themselves in addition to the envisioned roles the resultant products and services will play in broader environmental and energy transition narratives. Efforts to bring together stakeholders representing different areas of the FCEV market should be seen as important enablers of success for market participants.

This paper aims to present an overview of the current state of hydrogen storage methods and materials assess the potential benefits and challenges of various storage techniques and outline future research directions towards achieving effective economical safe and scalable storage solutions. Hydrogen is recognized as a clean secure and costeffective green energy carrier with zero emissions at the point of use offering significant contributions to reaching carbon neutrality goals by 2050. Hydrogen as an energy vector bridges the gap between fossil fuels which produce greenhouse gas emissions global climate change and negatively impact health and renewable energy sources which are often intermittent and lack sustainability. However widespread acceptance of hydrogen as a fuel source is hindered by storage challenges. Crucially the development of compact lightweight safe and cost-effective storage solutions is vital for realizing a hydrogen economy. Various storage methods including compressed gas liquefied hydrogen cryocompressed storage underground storage and solid-state storage (material-based) each present unique advantages and challenges. Literature suggests that compressed hydrogen storage holds promise for mobile applications. However further optimization is desired to resolve concerns such as low volumetric density safety worries and cost. Cryo-compressed hydrogen storage also is seen as optimal for storing hydrogen onboard and offers notable benefits for storage due to its combination of benefits from compressed gas and liquefied hydrogen storage by tackling issues related to slow refueling boil-off and high energy consumption. Material-based storage methods offer advantages in terms of energy densities safety and weight reduction but challenges remain in achieving optimal stability and capacities. Both physical and material-based storage approaches are being researched in parallel to meet diverse hydrogen application needs. Currently no single storage method is universally efficient robust and economical for every sector especially for transportation to use hydrogen as a fuel with each method having its own advantages and limitations. Moreover future research should focus on developing novel materials and engineering approaches in order to overcome existing limitations provide higher energy density than compressed hydrogen and cryo-compressed hydrogen storage at 70 MPa enhance costeffectiveness and accelerate the deployment of hydrogen as a clean energy vector.

This study investigates the effect of Oxygen-Enriched Combustion on hydrogen-enriched natural gas (H2 -NG) fuel mixtures at a semi-industrial scale (up to 60 kW). The analysis focuses on flame structure temperature distribu tion in the furnace NOx emissions and potential fuel savings. A multi-fuel multi-oxidizer jet burner was used to compare two oxygen enrichment configurations: premixed with air (PM) and air-pure O2 (AO) independent feed. The O2 -enriched flames remained stable across the entire fuel range. OH* chemiluminescence imaging for the H2 -NG fuel mixture delivering 50 concentration kW revealed that higher O2 increases the OH* intensity narrows and elongates the flame transitions from buoyancy- to momentum-driven shape and relocates the reaction zone. At 50 % oxygen enrichment level (OEL) flame shape OH* intensity and temperature profiles resembled pure O combustion. Up to 29 % OEL furnace temperature profiles were similar to those 2 of air-fuel combustion. The power required to maintain 1300 ± 25 ◦C at the reference position decreases with O2 enrichment. Higher OELs resulted in a sharp increase in NOx emissions. The effect of hydrogen enrichment on NOx levels was significantly less pronounced than that of oxygen enrichment. The rise in NOx emissions correlates with increased OH* in tensities. For a 50 % H2 2 blend increasing the O concentration in the oxidizer from 21 % to 50 % resulted in a 27 % reduction in flue gas heat losses. Utilizing O2 co-produced with H2 could be strategic for reducing fuel consumption facilitating the adoption of hydrogen-based energy systems.

This report is an output of the Clean Energy Technology Observatory (CETO) and is an update of the “Water electrolysis and hydrogen in the European Union” 2023 CETO report. CETO’s objective is to provide an evidencebased analysis feeding the policy making process and hence increasing the effectiveness of R&I policies for clean energy technologies and solutions. It monitors EU research and innovation activities on clean energy technologies needed for the delivery of the European Green Deal; and assesses the competitiveness of the EU clean energy sector and its positioning in the global energy market. CETO is being implemented by the Joint Research Centre for DG Research and Innovation Energy in coordination with DG Energy.

To achieve energy transition hydrogen and carboxylic acids have attracted much attention due to their cleanliness and renewability. Anaerobic fermentation technology is an effective combination of waste biomass resource utilization and renewable energy development. Therefore the utilization of anaerobic fermentation technology is expected to achieve efficient co-production of hydrogen and carboxylic acids. However this process is fundamentally affected by gas–liquid mass transfer kinetics bubble behaviors and system partial pressure. Moreover the related studies are few and unfocused and no systematic research has been developed yet. This review systematically summarizes and discusses the basic mathematical models used for gas–liquid mass transfer kinetics the relationship between gas solubility and mass transfer and the liquid-phase product composition. The review analyzes the roles of the headspace gas composition and partial pressure of the reaction system in regulating co-production. Additionally we discuss strategies to optimize the metabolic pathways by modulating the gas composition and partial pressure. Finally the feasibility of and prospects for the realization of hydrogen and carboxylic acid co-production in anaerobic fermentation systems are outlined. By exploring information related to gas mass transfer and system pressure this review will surely provide an important reference for promoting cleaner production of sustainable energy.

To achieve deep decarbonization in the transportation sector this study employs life cycle assessment (LCA) and the GREET model to construct baseline and low-carbon scenarios. It simulates the evolution of emissions and energy consumption within Inner Mongolia’s public transportation energy system (including diesel buses (DBs) electric buses (EBs) and hydrogen fuel cell buses (HFCBs)) from 2022 to 2035 while exploring synergistic pathways for its low-carbon transition. Results reveal that under the baseline scenario reliance on industrial by-product hydrogen causes fuel cell bus emissions to increase by 3.64% in 2025 compared to 2022 with system energy savings below 10% and decarbonization potential will be constrained by scale limitations and storage/transportation losses in cold regions. Under the low-carbon scenario deep grid decarbonization vehicle structure optimization and green hydrogen integration reduced system emissions and energy consumption by 66.86% and 40.44% respectively compared to 2022. The study identifies a 15% green hydrogen penetration rate as the critical threshold for resource misallocation and confirms grid decarbonization as the top-priority policy tool yielding marginal benefits 1.43 times greater than standalone hydrogen policies. This study underscores the importance of multipolicy coordination and ‘technology-supply chain’ synergy particularly highlighting the critical threshold of green hydrogen penetration and the primacy of grid decarbonization offering insights for similar coal-dominated cold-region transportation energy transitions.