United States

This research undertakes a comparative analysis of current and emerging hydrogen (H2) production technologies evaluating them based on quantitative and qualitative decision criteria. The quantitative criteria include cost of H2 production (USD/kg H2) energy consumption (MJ/kg H2) global warming potential (kg CO2-eq/kg H2) and technology energy efficiency (%). The qualitative criteria encompass technology readiness level (TRL) and availability of supply chain materials (classified as low medium or high). To achieve these objectives an extensive literature review has been conducted systematically assessing the selected H2 production technologies against the aforementioned criteria. The insights synthesized from the literature provide a foundation for an informed science-based evaluation of the potentials and techno-economic challenges that these technologies face in achieving the 1-1-1 goal set by the U.S. Department of Energy (DOE) in 2021. This target aims for a H2 production cost of USD 1/kg H2 within one decade (by 2031) including costs associated with production delivery and dispensing at H2 fueling stations (HRSs). Also the DOE established an interim goal of USD 2/kg H2 by 2026. This research concludes that among the examined H2 production technologies water electrolysis and biomass waste valorization emerge as the most promising near-term solutions to meet the DOE’s goal.

Electrolysis of water to generate hydrogen fuel is an attractiverenewable energy storage technology. However grid-scale fresh-water electrolysis would put a heavy strain on vital water re-sources. Developing cheap electrocatalysts and electrodes that cansustain seawater splitting without chloride corrosion could ad-dress the water scarcity issue. Here we present a multilayer anodeconsisting of a nickel–iron hydroxide (NiFe) electrocatalyst layeruniformly coated on a nickel sulfide (NiSx) layer formed on porousNi foam (NiFe/NiSx-Ni) affording superior catalytic activity andcorrosion resistance in solar-driven alkaline seawater electrolysisoperating at industrially required current densities (0.4 to 1 A/cm2)over 1000 h. A continuous highly oxygen evolution reaction-active NiFe electrocatalyst layer drawing anodic currents towardwater oxidation and an in situ-generated polyatomic sulfate andcarbonate-rich passivating layers formed in the anode are respon-sible for chloride repelling and superior corrosion resistance of thesalty-water-splitting anode.

China’s progress in decarbonizing its transportation particularly vehicle electrification is notable. However the economically effective pathways are underexplored. To find out how much cost is necessary for carbon neutrality for the light-duty vehicle (LDV) sector this study examines twenty decarbonization pathways combining the New Energy and Oil Consumption Credit model and the China-Fleet model. We find that the 2060 zero-greenhouse gas (GHG) emission goal for LDVs is achievable via electrification if the battery pack cost is under CNY483/kWh by 2050. However an extra of CNY8.86 trillion internal subsidies is needed under pessimistic battery cost scenarios (CNY759/kWh in 2050) to eliminate 246 million tonnes of CO2-eq by 2050 ensuring over 80% market penetration of battery electric vehicles (BEVs) in 2050. Moreover the promotion of fuel cell electric vehicles is synergy with BEVs to mitigate the carbon abatement difficulties decreasing up to 34% of the maximum marginal abatement internal investment.

Civil aviation provides an essential transportation network that connects the world and supports global economic growth. To maintain these benefits while meeting environmental goals next-generation aircraft must have drastically reduced climate impacts. Hydrogen-powered aircraft have the potential to fly existing routes with no carbon emissions and reduce or eliminate other emissions. This paper is a comprehensive guide to hydrogen-powered aircraft that explains the fundamental physics and reviews current technologies. We discuss the impact of these technologies on aircraft design cost certification and environment. In the long term hydrogen aircraft appear to be the most compelling alternative to today’s kerosene-powered aircraft. Using hydrogen also enables novel technologies such as fuel cells and superconducting electronics which could lead to aircraft concepts that are not feasible with kerosene. Hydrogen-powered aircraft are technologically feasible but require significant research and development. Lightweight liquid hydrogen tanks and their integration with the airframe is one of the critical technologies. Fuel cells can eliminate in-flight emissions but must become lighter more powerful and more durable to make large fuel cell-powered transport aircraft feasible. Hydrogen turbofans already have these desirable characteristics but produce some emissions albeit much less damaging than kerosene turbofans. Beyond airframe and propulsion technologies the viability of hydrogen aircraft hinges on low-cost green hydrogen production which requires massive investments in the energy infrastructure.

A holistic approach to decision-making in modern energy systems is vital due to their increase in complexity and interconnectedness. However decision makers often rely on narrowlyfocused strategies such as economic assessments for energy system strategy selection. The approach in this paper helps considers various factors such as economic viability technological feasibility environmental impact and social acceptance. By integrating these diverse elements decision makers can identify more economically feasible sustainable and resilient energy strategies. While existing focused approaches are valuable since they provide clear metrics of a potential solution (e.g. an economic measure of profitability) they do not offer the much needed system-as-a-whole understanding. This lack of understanding often leads to selecting suboptimal or unfeasible solutions which is often discovered much later in the process when a change may not be possible. This paper presents a novel evaluation framework to support holistic decision-making in energy systems. The framework is based on a systems thinking approach applied through systems engineering principles and model-based systems engineering tools coupled with a multicriteria decision analysis approach. The systems engineering approach guides the development of feasible solutions for novel energy systems and the multicriteria decision analysis is used for a systematic evaluation of available strategies and objective selection of the best solution. The proposed framework enables holistic multidisciplinary and objective evaluations of solutions and strategies for energy systems clearly demonstrates the pros and cons of available options and supports knowledge collection and retention to be used for a different scenario or context. The framework is demonstrated in case study evaluation solutions for a novel energy system of clean hydrogen generation.

Hydrogen will play a key role in decarbonizing economies. Here we quantify the costs and environmental impacts of possible large-scale hydrogen economies using four prospective hydrogen demand scenarios for 2050 ranging from 111–614 megatonne H2 year−1 . Our findings confirm that renewable (solar photovoltaic and wind) electrolytic hydrogen production generates at least 50–90% fewer greenhouse gas emissions than fossil-fuel-based counterparts without carbon capture and storage. However electrolytic hydrogen production could still result in considerable environmental burdens which requires reassessing the concept of green hydrogen. Our global analysis highlights a few salient points: (i) a mismatch between economical hydrogen production and hydrogen demand across continents seems likely; (ii) regionspecific limitations are inevitable since possibly more than 60% of large hydrogen production potentials are concentrated in water-scarce regions; and (iii) upscaling electrolytic hydrogen production could be limited by renewable power generation and natural resource potentials.

This review sets out to investigate the detrimental impacts of hydrogen gas (H2 ) on critical boiler components and provide appropriate state-of-the-art mitigation measures and future research directions to advance its use in industrial boiler operations. Specifically the study focused on hydrogen embrittlement (HE) and high-temperature hydrogen attack (HTHA) and their effects on boiler components. The study provided a fundamental understanding of the evolution of these damage mechanisms in materials and their potential impact on critical boiler components in different operational contexts. Subsequently the review highlighted general and specific mitigation measures hydrogen-compatible materials (such as single-crystal PWA 1480E Inconel 625 and Hastelloy X) and hydrogen barrier coatings (such as TiAlN) for mitigating potential hydrogen-induced damages in critical boiler components. This study also identified strategic material selection approaches and advanced approaches based on computational modeling (such as phase-field modeling) and data-driven machine learning models that could be leveraged to mitigate potential equipment failures due to HE and HTHA under elevated H2 conditions. Finally future research directions were outlined to facilitate future implementation of mitigation measures material selection studies and advanced approaches to promote the extensive and sustainable use of H2 in industrial boiler operations.

Nanomaterials have attracted great interest in recent years because of the unusual mechanical electrical electronic opticalmagnetic and surface properties. The high surface/volume ratio of these materials has significant implications with respectto energy storage. Both the high surface area and the opportunity for nanomaterial consolidation are key attributes of thisnew class of materials for hydrogen storage devices. Nanostructured systems including carbon nanotubes nano-magnesiumbased hydrides complex hydride/carbon nanocomposites boron nitride nanotubes TiS2/MoS2 nanotubes alanates polymernanocomposites and metal organic frameworks are considered to be potential candidates for storing large quantities of hydrogen.Recent investigations have shown that nanoscale materials may offer advantages if certain physical and chemical effects related tothe nanoscale can be used efficiently. The present review focuses the application of nanostructured materials for storing atomicor molecular hydrogen. The synergistic effects of nanocrystalinity and nanocatalyst doping on the metal or complex hydrides forimproving the thermodynamics and hydrogen reaction kinetics are discussed. In addition various carbonaceous nanomaterialsand novel sorbent systems (e.g. carbon nanotubes fullerenes nanofibers polyaniline nanospheres and metal organic frameworksetc.) and their hydrogen storage characteristics are outlined.

Hydrogen is a zero-carbon energy carrier with potential to decarbonize industrial and transportation sectors but its life-cycle greenhouse gas (GHG) emissions depend on its energy supply chain and carbon management measures (e.g. carbon capture and storage). Global support for clean hydrogen production and use has recently intensified. In the United States Congress passed several laws that incentivize the production and use of renewable and low-carbon hydrogen such as the Bipartisan Infrastructure Law (BIL) in 2021 and the Inflation Reduction Act (IRA) in 2022 which provides tax credits of up to $3/kg depending on the carbon intensity of the produced hydrogen. A comprehensive life-cycle accounting of GHG emissions associated with hydrogen production is needed to determine the carbon intensity of hydrogen throughout its value chain. In the United States Argonne’s R&D GREET® (Greenhouse Gases Regulated emissions and Energy use in Technologies) model has been widely used for hydrogen carbon intensity calculations. This paper describes the major hydrogen technology pathways considered in the United States and provides data sources and carbon intensity results for each of the hydrogen production and delivery pathways using consistent system boundaries and most recent technology performance and supply chain data.

Hydrogen as a clean fuel offers a practical pathway to achieve net-zero targets. However due to its physical and chemical characteristics there are some safety concerns for large-scale hydrogen utilisation particularly in process safety management. Leakage of gaseous hydrogen especially in semi-confined spaces such as tunnels can lead to catastrophic outcomes including uncontrolled fire and explosion. The current paper describes the outcome of an experimental and numerical study that aims to understand the dispersion of leaked light gas in a semi-confined space to support the adoption of hydrogen. A dispersion chamber with dimensions of 4m × 0.3m × 0.3m was constructed to investigate a baseline gas leakage scenario. To reduce the risk of the experiment in the laboratory helium is utilised as a surrogate for hydrogen. Computational fluid dynamics simulations are con ducted using FLACS-CFD to model the dispersion of leaked gas in different scenarios focusing on the impact of the ventilation velocity leakage rate and slope. The results from comprehensive numerical simulations show that ventilation is a critical safety management measure that can significantly reduce the growth of flammable clouds and mitigate the fire and explosion risk. Even with the lowest ventilation velocity of 0.25 m/s an improvement in the gas concentration level of 29.34% can be achieved in the downstream chamber. The current results will help to further enhance the understanding of hydrogen safety aspects.