Publications

Understanding what people think about hydrogen energy and how this influences their acceptance of the associated technology is a critical area of research. The public’s willingness to adopt practical applications of hydrogen energy such as hydrogen fuel-cell vehicles (HFCVs) is a key factor in their deployment. To analyse the direct and indirect effects of key attitudinal variables that could influence the intention to use HFCVs in Spain an online questionnaire was administered to a representative sample of the Spanish population (N = 1000). A path analysis Structural Equation Model (SEM) was applied to determine the effect of different attitudinal variables. A high intention to adopt HFCVs in Spain was found (3.8 out of 5) assuming their wider availability in the future. The path analysis results indicated that general acceptance of hydrogen technology and perception of its benefits had the greatest effect on the public’s intention to adopt HFCVs. Regarding indirect effects the role of trust in hydrogen technology was notable having significant mediating effects not only through general acceptance of hydrogen energy and local acceptance of hydrogen refuelling stations (HRS) but also through positive and negative emotions and benefits perception. The findings will assist in focusing the future hydrogen communication strategies of both the government and the private (business) sector.

This study proposes the SMR Smart Net-Zero City (SSNC) framework—a scalable model for achieving carbon neutrality by integrating Small Modular Reactors (SMRs) renewable energy sources and sector coupling within a microgrid architecture. As deploying renewables alone would require economically and technically impractical energy storage systems SMRs provide a reliable and flexible baseload power source. Sector coupling systems—such as hydrogen production and heat generation—enhance grid stability by absorbing surplus energy and supporting the decarbonization of non-electric sectors. The core contribution of this study lies in its real-time data emulation framework which overcomes a critical limitation in the current energy landscape: the absence of operational data for future technologies such as SMRs and their coupled hydrogen production systems. As these technologies are still in the pre-commercial stage direct physical integration and validation are not yet feasible. To address this the researchers leveraged real-time data from an existing commercial microgrid specifically focusing on the import of grid electricity during energy shortfalls and export during solar surpluses. These patterns were repurposed to simulate the real-time operational behavior of future SMRs (ProxySMR) and sector coupling loads. This physically grounded simulation approach enables highfidelity approximation of unavailable technologies and introduces a novel methodology to characterize their dynamic response within operational contexts. A key element of the SSNC control logic is a day–night strategy: maximum SMR output and minimal hydrogen production at night and minimal SMR output with maximum hydrogen production during the day—balancing supply and demand while maintaining high SMR utilization for economic efficiency. The SSNC testbed was validated through a seven-day continuous operation in Busan demonstrating stable performance and approximately 75% SMR utilization thereby supporting the feasibility of this proxy-based method. Importantly to the best of our knowledge this study represents the first publicly reported attempt to emulate the real-time dynamics of a net-zero city concept based on not-yet-commercial SMRs and sector coupling systems using live operational data. This simulation-based framework offers a forward-looking data-driven pathway to inform the development and control of next-generation carbon-neutral energy systems.

Portugal’s commitment to carbon neutrality by 2050 has intensified the search for renewable energy alternatives with biomass gasification emerging as a promising pathway for hydrogen production. This comprehensive review analyzes the potential of 39 Portuguese biomass species for gasification processes based on extensive laboratory characterization data including proximate analysis ultimate analysis heating values and metal content. The studied biomasses encompass woody shrubland species (matos arbustivos lenhosos) forest residues and energy crops representative of Portugal’s diverse biomass resources. Results indicate significant variability in gasification potential with moisture content ranging from 0.5% to 14.9% ash content from 0.5% to 5.5% and higher heating values between 16.8 and 21.2 MJ/kg. Theoretical hydrogen yield calculations suggest that Portuguese biomasses could produce between 85 and 120 kg H2 per ton of dry biomass with species such as Eucalyptus globulus Pinus pinaster and Cytisus multiflorus showing the highest potential. Statistical analysis reveals strong negative correlations between moisture content and hydrogen yield potential (r = −0.63) while carbon content shows positive correlation with gasification efficiency. The comprehensive characterization provides essential data for optimizing gasification processes and establishing Portugal’s biomass-tohydrogen production capacity contributing to the national hydrogen strategy and renewable energy transition.

This review article provides an overview of the use of hydrogen and tyre pyrolysis oil as fuels for homogeneous charge compression ignition (HCCI) engines. It discusses their properties the ways they are produced and their sustainability which is of particular importance in the present moment. Both fuels have certain advantages but also throw up many challenges which complicate their application in HCCI engines. The paper scrutinises engine performance with hydrogen and tyre pyrolysis oil respectively and compares the fuels’ emissions a crucial focus from an environmental perspective. It also surveys related technologies that have recently emerged their effects and environmental impacts and the rules and regulations that are starting to become established in these areas. Furthermore it provides a comparative discussion of various engine performance data in terms of combustion behaviour emission levels fuel economy and potential costs or savings in real terms. The analysis reveals significant research gaps and recommendations are provided as to areas for future study. The paper argues that hydrogen and tyre pyrolysis oil might sometimes be used together or in complementary ways to benefit HCCI engine performance. The importance of life-cycle assessment is noted acknowledging also the requirements of the circular economy. The major findings are summarised with some comments on future perspectives for the use of sustainable fuels in HCCI engines. This review article provides a helpful reference for researchers working in this area and for policymakers concerned with establishing relevant legal frameworks as well as for companies in the sustainable transport sector.

Hydrogen can play a significant role in Australian economy and Australia has set an ambitious goal to become a global leader in hydrogen industry as outlined in the National Hydrogen Strategy 2024. Hydrogen is an efficient energy carrier that can be used for both transporting and storing energy. Underground hydrogen storage (UHS) in aquifers depleted gas and oil reservoirs and salt caverns have been considered as a low-cost option for largescale storage of hydrogen. In this study a method for hydrogen storage in engineered (shallow) lenses is proposed where a lens is created in a very low permeability layered formation such as shales via opening the layers by a pressurised fluid. A preliminary overview of the Australian basins is presented focussing on the most suitable/obvious units for the purpose of creating engineered lenses for storage of hydrogen. Major engineering aspects of lenses such as size volume storage capacity storage time and hydrogen loss are reviewed followed by a Techno-Economic Analysis for the proposed hydrogen storage method. Initial modelling shows that up to 250 tonnes of hydrogen can be stored in shallow engineered lenses incurring a capital cost of 35.7 US$/kg and total annual operational cost of 7 US$/kg making the proposed storage method a competitive option against salt and lined rock caverns. Finally Monitoring and Verification (M&V) as part of storage assurance practice has been discussed and successful examples are presented.

Plastic waste continues to increasingly pollute the environment. Currently a significant portion of this waste is either landfilled or incinerated to generate energy which leads to substantial CO2 emissions. However thermochemical processing is a potential solution to create a circular economy with pyrolysis combined with the subsequent high-temperature treatment of the vapour-gas mixture being a method preferable to incineration. This study investigated the optimal conditions for the two-stage pyrolysis of non-recyclable plastic waste. The process involved a low-temperature treatment of feedstock followed by high-temperature exposure of the vapour-gas mixture in the presence of a carbon matrix. The final products of the two-stage pyrolysis were: synthesis gas mainly consisting of hydrogen and carbon monoxide; solid pyrolysis residue obtained in the first stage and high-carbon material during the second stage was obtained. The first stage of the two-stage pyrolysis was carried out at various temperatures ranging from 460 to 540 ◦C followed by cracking at 600 to 1000 ◦C with different ratios of packaging waste to wood charcoal (1:2 1:4 1:6). The conditions for obtaining more than 70 vol% hydrogen in the synthesis gas from packaging waste were determined the effect of changing the process parameters was studied. The decomposition kinetics of packaging waste showed activation energies of the first and second steps: 165 and 255 kJ/mol (Ozawa–Flynn–Wall method) 164 and 259 kJ/mol (Kissinger–Akahira–Sunose method) respectively. This work contributes to the study of efficient recycling methods for non-recyclable packaging waste and promotes advancements in sustainable waste management practices.

Hydrogen is a key energy carrier in the global transition to low-carbon systems requiring scalable and secure storage solutions. While underground hydrogen storage (UHS) in salt caverns is proven its cost and limited geographic availability have led to growing interest in depleted oil and gas reservoirs. A critical factor in evaluating these reservoirs is the sealing capacity of the overlying caprock. This study presents a novel experimental protocol for assessing caprock integrity under UHS conditions using a custom-designed core-flooding apparatus integrated with a micro-capillary flow meter. This setup enables high-resolution measurements of ultra-low permeabilities (as low as 10 nano-Darcy) flow rates (down to 10 nano-liters/hour) threshold pressure and breakthrough pressure. Benchmark tests with nitrogen and methane were followed by hydrogen experiments across caprocks with a wide range of permeability and porosity. The results demonstrate clear trends between caprock properties and sealing performance providing a quantitative framework for evaluating UHS site suitability. Hydrogen showed slightly lower threshold and breakthrough pressures compared to other gases reinforcing the need for accurate site-specific caprock evaluation. The proposed method offers a robust approach for characterizing candidate storage sites in depleted reservoirs.

Integrating renewable energy requires robust large-scale storage solutions to balance intermittent supply. Underground hydrogen storage (UHS) in geological formations such as salt caverns depleted hydrocarbon reservoirs or aquifers offers a promising way to store large volumes of energy for seasonal periods. This review focuses on the biological aspects of UHS examining the biogeochemical interactions between H2 reservoir minerals and key hydrogenotrophic microorganisms such as sulfate-reducing bacteria methanogens acetogens and iron-reducing bacteria within the gas–liquid–rock–microorganism system. These microbial groups use H2 as an electron donor triggering biogeochemical reactions that can affect storage efficiency through gas loss and mineral dissolution–precipitation cycles. This review discusses their metabolic pathways and the geochemical interactions driven by microbial byproducts such as H2S CH4 acetate and Fe2+ and considers biofilm formation by microbial consortia which can further change the petrophysical reservoir properties. In addition the review maps 76 ongoing European projects focused on UHS showing 71% target salt caverns 22% depleted hydrocarbon reservoirs and 7% aquifers with emphasis on potential biogeochemical interactions. It also identifies key knowledge gaps including the lack of in situ kinetic data limited field-scale monitoring of microbial activity and insufficient understanding of mineral–microbe interactions that may affect gas purity. Finally the review highlights the need to study microbial adaptation over time and the influence of mineralogy on tolerance thresholds. By analyzing these processes across different geological settings and integrating findings from European research initiatives this work evaluates the impact of microbial and geochemical factors on the safety efficiency and long-term performance of UHS.

This study focuses on the power systems of inland waterway vessels in Chinese Yangtze River systematically outlining the low-carbon technology pathways for different power system types. A comparative analysis is conducted on the technical feasibility emission reduction potential and economic viability of LNG methanol ammonia pure electric and hybrid power systems revealing the bottlenecks hindering the large-scale application of each system. Key findings indicate that: (1) LNG and methanol fuels offer significant short-term emission reductions in internal combustion engine power systems yet face constraints from methane slip and insufficient green methanol production capacity respectively; (2) ammonia enables zero-carbon operations but requires breakthroughs in combustion stability and synergistic control of NOX; (3) electric vessels show high decarbonization potential but battery energy density limits their range while PEMFC lifespan constraints and SOFC thermal management deficiencies impede commercialization; (4) hybrid/range-extended power systems with superior energy efficiency and lower retrofitting costs serve as transitional solutions for existing vessels though challenged by inadequate energy management strategies and multi-equipment communication protocol interoperability. A phased transition pathway is proposed: LNG/methanol engines and hybrid systems dominate during 2025–2030; ammonia-powered systems and solid-state batteries scale during 2030–2035; post-2035 operations achieve zero-carbon shipping via green hydrogen/ammonia.

The increasing interest in off-grid green hydrogen production has elevated the importance of reliable techno-economic assessment (TEA) tools to support investment and planning decisions. However limited operational data and inconsistent modeling approaches across existing tools introduce significant uncertainty in cost estimations. This study presents a comprehensive review and comparative analysis of seven TEA tools—ranging from simplified calculators to advanced hourly based simulation platforms—used to estimate the Levelized Cost of Hydrogen (LCOH) in off-grid Hydrogen Production Plants (HPPs). A standardized simulation framework was developed to input consistent technical economic and financial parameters across all tools allowing for a horizontal comparison. Results revealed a substantial spread in LCOH values from EUR 5.86/kg to EUR 8.71/kg representing a 49% variation. This discrepancy is attributed to differences in modeling depth treatment of critical parameters (e.g. electrolyzer efficiency capacity factor storage and inflation) and the tools’ temporal resolution. Tools that included higher input granularity hourly data and broader system components tended to produce more conservative (higher) LCOH values highlighting the cost impact of increased modeling realism. Additionally the total project cost—more than hydrogen output—was identified as the key driver of LCOH variability across tools. This study provides the first multi-tool horizontal testing protocol a methodological benchmark for evaluating TEA tools and underscores the need for harmonized input structures and transparent modeling assumptions. These findings support the development of more consistent and reliable economic evaluations for off-grid green hydrogen projects especially as the sector moves toward commercial scale-up and policy integration.