Publications

Fuel cell (FC) technologies are often regarded as a sustainable alternative to conventional combustion-based energy systems due to their low environmental impact and high efficiency. Thorough environmental assessments using Life Cycle Assessment (LCA) methodologies are needed to understand and mitigate their impacts. However there has been a lack of comprehensive reviews on LCA studies across all major types of FCs. This study reviews and synthesizes results from 44 peer-reviewed LCA studies from 2015 to 2024 covering six major FC types: alkaline (AFC) direct methanol (DMFC) molten carbonate (MCFC) proton- exchange membrane (PEMFC) solid oxide (SOFC) and phosphoric acid (PAFC). The review provides an updated overview of LCA practices and results over the past decade while identifying methodological inconsistencies and gaps. PEMFCs are the most frequently assessed FC typology covering 49 % of the studies followed by SOFCs at 38 % with no studies on DMFCs. Only 11 % of comparative studies carry out inter-comparison between FC types. Discrepancies in system boundary definitions across studies are identified highlighting the need for standardization to enhance comparability between studies. Global Warming Potential (GWP) evaluated in 100 % of the studies is the most assessed impact category. Fuel supply in the use phase a major contributor to greenhouse gas (GHG) emissions is under-assessed as it is usually aggregated with Operation and Maintenance (O&M) phase instead of discussed separately. GWP of energy production by all FC typologies spans from 0.026 to 1.76 kg CO₂-equivalent per kWh. Insufficient quantitative data for a meta-analysis and limited inter-comparability across FC types are noted as critical gaps. The study highlights the need for future research and policies focusing on green hydrogen supply and circular economy practices to improve FC sustainability.

Electric arc furnace slag is a major by-product of steelmaking yet its industrial utilization remains limited due to its complex chemical and mineralogical composition. This study presents a hydrogen-based approach to recover metallic components from EAF slag for potential reuse in steelmaking. Laboratory experiments were conducted by melting 50 g of industrial slag samples at 1600 ◦C and injecting hydrogen gas through a ceramic tube into the liquid slag. After cooling both the slag and the metallic phases were analyzed for their chemical and phase compositions. Additionally the reduction process was modeled using a combination of approaches including the thermochemical software FactSage 8.1 models for density surface tension and viscosity as well as a diffusion model. The injection of hydrogen resulted in the reduction of up to 40% of the iron oxide content in the liquid slag. In addition the fraction of reacted hydrogen gas was calculated.

The increasing demand for energy and the urgent need to reduce carbon emissions have positioned hydrogen as a promising alternative. This review paper explores the potential of hydrogen blending in natural gas pipelines focusing on the compatibility of pipeline materials and the associated safety challenges. Hydrogen blending can significantly reduce carbon emissions from homes and industries as demonstrated by various projects in Canada and globally. However the introduction of hydrogen into natural gas pipelines poses risks such as hydrogenassisted materials degradation which can compromise the integrity of pipeline materials. This study reviews the effects of hydrogen on the mechanical properties of both vintage and modern pipeline steels cast iron copper aluminum stainless steel as well as plastics elastomers and odorants that compose an active natural gas pipeline network. The review highlights the need for updated codes and standards to ensure safe operation and discusses the implications of hydrogen on material selection design and safety considerations. Overall this manuscript aims to provide a comprehensive resource on the current state of pipeline materials in the context of hydrogen blending emphasizing the importance of further research to address the gaps in current knowledge and to develop robust guidelines for the integration of hydrogen into existing natural gas infrastructure.

In this work a new modeling tool called DECAL (DEcarbonize CALifornia) is developed and used to evaluate what it will take to reach California’s climate mandate of net-zero emissions by 2045. DECAL is a scenario-based model that projects emissions society-wide costs and resource consumption in response to user-defined inputs. DECAL has sufficient detail to model true net-zero pathways and reveal fine-grain technology insights. Using DECAL we find the State can achieve 52 % of the emissions abatement needed to meet net-zero by 2045 using technologies that are already commercially available such as electric vehicles heat pumps and renewable electricity & storage. While these technologies are mature the speed and scale of deployment required will still pose significant practical challenges if not technical ones. In addition we find that 25 % of emissions abatement will come from technologies currently at early-stage deployment and 23 % from technologies at research scale motivating the continued research & development of these technologies including zero-emission heavy-duty vehicles carbon capture & sequestration clean industrial heating low global warming potential refrigerants and direct air capture. Significant carbon dioxide removal will also be needed for California to meet its net-zero target on time at least 45 Mt/yr and more likely up to 75 Mt/yr by 2045. Accelerating deployment of mature technologies can further reduce the need for carbon removal nevertheless establishing enforceable carbon removal targets and conducting policy planning to make said goals a reality will be needed if California is to meet its net-zero by 2045 goal.

Under the guidance of energy-saving and emission reduction goals a lowcarbon economic operation method for integrated energy systems (IES) has been proposed. This strategy aims to enhance energy utilization efficiency bolster equipment operational flexibility and significantly cut down on carbon emissions from the IES. Firstly a thorough exploration of the two-stage operational framework of Power-to-Gas (P2G) technology is conducted. Electrolyzers methane reactors and hydrogen fuel cells (HFCs) are introduced as replacements for traditional P2G equipment with the objective of harnessing the multiple benefits of hydrogen energy. Secondly a cogeneration and HFC operational strategy with adjustable heat-to-electricity ratio is introduced to further enhance the IES’s low-carbon and economic performance. Finally a step-by-step carbon trading mechanism is introduced to effectively steer the IES towards carbon emission control.

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.

In this study the electrolysis of water by using ammonium chloride (NH4Cl) as an electrolyte was investigated for the production of hydrogen gas. The assembled electrochemical cell consists mainly of twenty-one stainless-steel electrodes and a direct current from a battery ammonium chloride solution. In the electrolysis process hydrogen and oxygen are developed at the same time and collected as a mixture to be used as a fuel. This study explores a technic regarding the matching of oxyhydrogen (HHO) electrolyzers with photovoltaic (PV) systems to make HHO gas. The primary objective of the present research is to enable the electrolyzer to operate independently of other energy origins functioning as a complete unit powered solely by PV. Moreover the impact of using PWM on cell operation was investigated. The experimental data was collected at various time intervals NH4Cl concentrations. Additionally the hydrogen unit consists of two cells with a shared positive pole fixed between them. Some undesirable anodic reaction affects the efficiency of hydrogen gas production because of the corrosion of anode to ferrous hydroxide (Fe(OH)2). Polyphosphate Inhibitor was used to minimize the corrosion reaction of anode and keep the efficiency of hydrogen gas flow. The optimal concentration of 3M for ammonium chloride was identified balancing a gas flow rate of 772 ml/min with minimal anode corrosion. Without PWM conversion efficiency ranges between 93% and 96%. Therefore PWM increased conversion efficiency by approximately 5% leading to a corresponding increase in hydrogen gas production.

This study investigates the impact of delayed and accelerated expansion of the volatile renewable energy sources (vRES) onshore wind offshore wind and photovoltaics on Europe’s (EU27 United Kingdom Norway and Switzerland) demand for hydrogen imports and its derivatives to meet demand from final energy consumption sectors and to comply with European greenhouse gas (GHG) emission targets. Using the multi-energy system model ISAaR we analyze fourteen scenarios with different levels of vRES expansion including an evaluation of the resulting hydrogen prices. The load-weighted average European hydrogen price in the BASE scenario decreases from 4.1 €/kg in 2030 to 3.3 €/kg by 2050. Results show that delaying the expansion of vRES significantly increases the demand for imports of hydrogen and its derivatives and thus increases the risk of not meeting GHG emission targets for two reasons: (1) higher import volumes to meet GHG emission targets increase dependence on third parties and lead to higher risk in terms of security of supply; (2) at the same time lower vRES expansion in combination with higher import volumes leads to higher resulting hydrogen prices which in turn affects the economic viability of the energy transition. In contrast an accelerated expansion of vRES reduces dependency on imports and stabilizes hydrogen prices below 3 €/kg in 2050 which increases planning security for hydrogen off-takers. The study underlines the importance of timely and strategic progress in the expansion of vRES and investment in hydrogen production storage and transport networks to minimize dependence on imports and effectively meet the European climate targets.

The Middle East and North Africa region has not played a major role in climate action so far and several countries depend economically on fossil fuel exports. However this is a region with vast solar energy resources which can be exploited affordably for power generation and hydrogen production at scale to eventually reach carbon neutrality. In this paper we elaborate on the case of the United Arab Emirates and explore the aspirations and feasibility of its net-zero by 2050 target. While we affirm the concept per se we also highlight the technological complexity and economic dimensions that accompany such transformation. We expect the UAE’s electricity demand to triple between today and 2050 and the annual green hydrogen production is expected to reach 3.5 Mt accounting for over 40% of the electricity consumption. Green hydrogen will provide power-to-fuel solutions for aviation maritime transport and hard-to-abate industries. At the same time electrification will intensify—most importantly in road transport and low-temperature heat demands. The UAE can meet its future electricity demands primarily with solar power followed by natural gas power plants with carbon capture utilization and storage while the role of nuclear power in the long term is unclear at this stage.

Hydrogen is increasingly recognized as an element in the effort to decarbonize the energy sector. Within the development of large-scale supply chain the storage phase emerges as a significant challenge. This study reviews Life Cycle Assessment (LCA) literature focused exclusively on hydrogen as an energy vector aiming to identify areas for improvement highlight effective solutions and point out research gaps. The goal is to provide a comprehensive overview of hydrogen storage technologies from an environmental perspective. A systematic search was conducted in the SCOPUS database using a specific set of keywords resulting in the identification of 30 relevant studies. These works explore hydrogen storage across different scales and applications which were classified into five categories based on the type of storage application most of them related to stationary use. The majority of the selected studies focus on storing hydrogen in compressed gas tanks. Notably 33 % of the analyzed articles assess only greenhouse gas (GHG) emissions and 10 % evaluate only two environmental impact categories including GHGs. This reflects a limited understanding of broader environmental impacts with a predominant focus on CO₂eq emissions. When comparing different case studies storage methods associated with the lowest emissions include metal hydrides and underground hydrogen storage. Another important observation is the trend of decreasing CO₂eq emissions as the storage system scale increases. Future studies should adopt more comprehensive approaches by analyzing a wider range of hydrogen storage technologies and considering multiple environmental impact categories in LCA. Moreover it is crucial to integrate environmental economic and social dimensions of sustainability as multidimensional assessments are essential to support well-informed balanced decisions that align with the sustainable development of hydrogen storage systems.