United States

This study emphasises the growing relevance of hydrogen as a green energy source in meeting the growing need for sustainable energy solutions. It foregrounds the importance of assessing the environmental consequences of hydrogen-generating processes for their long-term viability. The article compares several hydrogen production processes in terms of scalability costeffectiveness and technical improvements. It also investigates the environmental effects of each approach considering crucial elements such as greenhouse gas emissions water use land needs and waste creation. Different industrial techniques have distinct environmental consequences. While steam methane reforming is cost-effective and has a high production capacity it is coupled with large carbon emissions. Electrolysis a technology that uses renewable resources is appealing but requires a lot of energy. Thermochemical and biomass gasification processes show promise for long-term hydrogen generation but further technological advancement is required. The research investigates techniques for improving the environmental friendliness of hydrogen generation through the use of renewable energy sources. Its ultimate purpose is to offer readers a thorough awareness of the environmental effects of various hydrogen generation strategies allowing them to make educated judgements about ecologically friendly ways. It can ease the transition to a cleaner hydrogen-powered economy by considering both technological feasibility and environmental issues enabling a more ecologically conscious and climate-friendly energy landscape.

Hydrogen vehicles encompassing fuel cell electric vehicles (FCEVs) are pivotal within the UK’s energy landscape as it pursues the goal of net-zero emissions by 2050. By markedly diminishing dependence on fossil fuels FCEVs including hydrogen vehicles wield substantial influence in shaping the circular economy (CE). Their impact extends to optimizing resource utilization enabling zero-emission mobility facilitating the integration of renewable energy sources supplying adaptable energy storage solutions and interconnecting diverse sectors. The widespread adoption of hydrogen vehicles accelerates the UK’s transformative journey towards a sustainable CE. However to fully harness the benefits of this transition a robust investigation and implementation of safety measures concerning hydrogen vehicle (HV) use are indispensable. Therefore this study takes a holistic approach integrating quantitative risk assessment (QRA) and an adaptive decision-making trial and evaluation laboratory (DEMATEL) framework as pragmatic instruments. These methodologies ensure both the secure deployment and operational excellence of HVs. The findings underscore that the root causes of HV failures encompass extreme environments material defects fuel cell damage delivery system impairment and storage system deterioration. Furthermore critical driving factors for effective safety intervention revolve around cultivating a safety culture robust education/training and sound maintenance scheduling. Addressing these factors is pivotal for creating an environment conducive to mitigating safety and risk concerns. Given the intricacies of conducting comprehensive hydrogen QRAs due to the absence of specific reliability data this study dedicates attention to rectifying this gap. A sensitivity analysis encompassing a range of values is meticulously conducted to affirm the strength and reliability of our approach. This robust analysis yields precise dependable outcomes. Consequently decision-makers are equipped to discern pivotal underlying factors precipitating potential HV failures. With this discernment they can tailor safety interventions that lay the groundwork for sustainable resilient and secure HV operations. Our study navigates the intersection of HVs safety and sustainability amplifying their importance within the CE paradigm. Using the careful amalgamation of QRA and DEMATEL methodologies we chart a course towards empowering decision-makers with the insights to steer the hydrogen vehicle domain to safer horizons while ushering in an era of transformative eco-conscious mobility.

Logistics is becoming more cost competitive while customers and regulatory bodies pressure businesses to disclose their carbon footprints creating interest in alternative fuels as a decarbonization strategy. This paper provides a thematic review of the role of alternative fuels in sustainable air land and sea logistics their challenges and potential mitigations. Through an extensive literature survey we determined that biofuels synthetic kerosene natural gas ammonia alcohols hydrogen and electricity are the primary alternative fuels of interest in terms of environmental sustainability and techno-economic feasibility. In air logistics synthetic kerosene from hydrogenated esters and fatty acids is the most promising route due to its high technical maturity although it is limited by biomass sourcing. Electrical vehicles are favorable in road logistics due to cheaper green power and efficient vehicle designs although they are constrained by recharging infrastructure deployment. In sea logistics liquified natural gas is advantageous owing to its supply chain maturity but it is limited by methane slip control and storage requirements. Overall our examination indicates that alternative fuels will play a pivotal role in the logistics networks of the future.

To identify lower-carbon and cost-effective hydrogen supplies for fuel and power generation in Singapore we assessed the cradle-to-gate greenhouse gas (GHG) emissions and the landed costs of over fifty supply chains from Malaysia and Australia with current and emerging blue turquoise and green hydrogen production and carrier technologies. We found that with current technologies the total life cycle global warming potential of local H2 production using steam methane reforming with carbon capture (4.47 kg CO2e/kg H2) is lower than importing solar-generated green H2 from Australia transported as NH3 (6.48 kg CO2e/kg H2) due to large emissions from conversion and transportation processes in the latter supply chain. When also considering emerging technologies turquoise H2 produced with the thermal decomposition of methane locally or in Malaysia is the most economical solution while wind-generated H2 from Australia transported as liquefied H2 or NH3 produce the least GHG emissions. In addition we projected the impacts of the Singapore carbon tax methane abatement in NG production and reduction of renewable energy embodied emissions and costs on the supply chains in the year 2030. We estimated that with the expected renewable energy improvements the emissions and costs of power generated from imported solar-powered H2 could drop by as much as 74% and 70% respectively.

Well characterized experimental data for consequence model validation is important in progressing the use of liquid hydrogen as an energy carrier. In 2019 the Health and Safety Executive (HSE) undertook a series of liquid hydrogen dispersion and combustion experiments as a part of the Pre-normative Research for Safe Use of Liquid Hydrogen (PRESLHY) project. In partnership between the National Renewable Energy Laboratory (NREL) and HSE time and spatially varying hydrogen concentration measurements were made in 25 dispersion experiments and 23 congested ignition experiments associated with PRESLHY WP3 and WP5 respectively. These measurements were undertaken using the hydrogen wide area monitoring system developed by NREL. During the 23 congested ignition experiments high variability was observed in the measured explosion severity during experiments with similar initial conditions. This led to the conclusion that wind including localized gusts had a large influence on the dispersion of the hydrogen and therefore the quantity of hydrogen that was present in the congested region of the explosions. Using the hydrogen concentration measurements taken immediately prior to ignition the hydrogen clouds were visualized in an attempt to rationalize the variability in overpressure between the tests. Gaussian process regression was applied to quantify the variability of the measured hydrogen concentrations. This analysis could also be used to guide modifications in experimental designs for future research on hydrogen combustion behavior.

In 2015 during the lead up to the Paris Climate Agreement the United States set forth a Nationally Determined Contribution that outlines national goals for greenhouse gas emission reductions. It was not until 2021 that the US put forth a long-term strategy that lays out the pathway to reach these goals. The US long-term strategy lays the framework for research needs to meet the greenhouse gas emission reduction goals and incentivizes industry to meet the goals using a variety of policies. The five US long term strategy core elements are to decarbonize electricity electrify end uses and switch to clean fuels cut energy waste reduce methane and other non-carbon dioxide greenhouse gas emissions and to scale up carbon dioxide removal. Implementation of the long term strategy has generally been funded by tax incentives and government grants that were approved as part of the Inflation Reduction Act. Political headwinds societal Not in My Backyard resistance long-term economic funding cumbersome permitting requirements and incentives vs. taxation debate are significant policy/nontechnical hurdles. Technical challenges remain regarding effective energy efficiency implementation the use of hydrogen as a fuel cost effective carbon emission treatment nuclear energy expansion renewables expansion and grid integration biofuel integration efficient and safe energy storage and electrical grid adequacy/expansion. This review article condenses the multitude of technical and policy issues facing the US long-term strategy providing readers with an overview of the extent and magnitude of the challenges while outlining possible solutions.

Hydrogen (H2) is widely viewed as critical to the decarbonization of industry and transportation. Water electrolysis powered by renewable electricity commonly referred to as green H2 can be used to generate H2 with low carbon dioxide emissions. Herein we analyze the critical mineral and energy demands associated with green H2 production under three different hypothetical future demand scenarios ranging from 100–1000 Mtpa H2. For each scenario we calculate the critical mineral demands required to build water electrolyzers (i.e. electrodes and electrolyte) and to build dedicated or additional renewable electricity sources (i.e. wind and solar) to power the electrolyzers. Our analysis shows that scaling electrolyzer and renewable energy technologies that use platinum group metals and rare earth elements will likely face supply constraints. Specifically larger quantities of lanthanum yttrium or iridium will be needed to increase electrolyzer capacity and even more neodymium silicon zinc molybdenum aluminum and copper will be needed to build dedicated renewable electricity sources. We find that scaling green H2 production to meet projected netzero targets will require ~24000 TWh of dedicated renewable energy generation which is roughly the total amount of solar and wind projected to be on the grid in 2050 according to some energy transition models. In summary critical mineral constraints may hinder the scaling of green H2 to meet global net-zero emissions targets motivating the need for the research and development of alternative lowemission methods of generating H2

Many off-grid communities in Canada are dependent on diesel generators to fulfill their utility and transportation needs causing destructive environmental impact. This study aims to optimize and investigate the technoeconomic feasibility of a hybrid renewable energy system to satisfy the 1.6 MWh/day electricity 184.2 kWh/day thermal and 428.38 kg/year hydrogen demand simultaneously Trout Lake a remote community of Northern Alberta. A novel hybrid energy system consisting of solar PV wind turbine electrolyzer hydrogen tank battery fuel cell hydrogen boiler and thermal load controller has been proposed to generate electricity heat and hydrogen by renewables which reduce carbon emission utilizing the excess energy (EE). Five different scenarios were developed in HOMER Pro software and the results were compared to identify the best combination of hybrid renewable energy systems. The results indicate that the fifth scenario is the optimal renewable energy system that provides a lower cost of energy (COE) at $0.675/kWh and can reduce 99.99% carbon emission compared to the diesel-based system. Additionally the utilization of thermal load controller battery and fuel cell improved the system’s reliability increasing renewable fraction (RF) (93.5%) and reducing EE (58.3%) significantly. In comparison to the diesel-based systems it is also discovered that battery energy storage is the most affordable option while fuel cells are the more expensive choice for remote community. Sensitivity analyses are performed to measure the impact of different dominating factors on COE EE and RF.

Recent advancements in membrane-assisted seawater electrolysis powered by renewable energy offer a sustainable path to green hydrogen production. However its large-scale implementation faces challenges due to slow powerto-hydrogen (P2H) conversion rates. Here we report a modular forward osmosis-water splitting (FOWS) system that integrates a thin-film composite FO membrane for water extraction with alkaline water electrolysis (AWE) denoted as FOWSAWE. This system generates high-purity hydrogen directly from wastewater at a rate of 448 Nm3 day−1 m−2 of membrane area over 14 times faster than the state-of-the-art practice with specific energy consumption as low as 3.96 kWh Nm−3 . The rapid hydrogen production rate results from the utilisation of 1 M potassium hydroxide as a draw solution to extract water from wastewater and as the electrolyte of AWE to split water and produce hydrogen. The current system enables this through the use of a potassium hydroxide-tolerant and hydrophilic FO membrane. The established waterhydrogen balance model can be applied to design modular FO and AWE units to meet demands at various scales from households to cities and from different water sources. The FOWSAWE system is a sustainable and an economical approach for producing hydrogen at a record-high rate directly from wastewater marking a significant leap in P2H practice.

Reducing greenhouse gas emissions in the transport sector is known to be an important contribution to climate change mitigation. Some parts of the transport sector are particularly difficult to decarbonize; this includes the heavy-duty vehicle sector which is considered one of the “hardto-abate” sectors of the economy. Transitioning from diesel trucks to hydrogen fuel cell trucks has been identified as a potential way to decarbonize the sector. However the current and future costs and efficiencies of the enabling technologies remain unclear. In light of these uncertainties this paper investigates the investments required to decarbonize New Zealand’s heavy-duty vehicle sector with green hydrogen. By combining system dynamics modelling literature and hydrogen transition modelling literature a customized methodology is developed for modelling hydrogen transitions with system dynamics modelling. Results are presented in terms of the investments required to purchase the hydrogen production capacity and the investments required to supply electricity to the hydrogen production systems. Production capacity investments are found to range between 1.59 and 2.58 billion New Zealand Dollars and marginal electricity investments are found to range between 4.14 and 7.65 billion New Zealand Dollars. These investments represent scenarios in which 71% to 90% of the heavy-duty vehicle fleet are replaced with fuel cell trucks by 2050. The wide range of these findings reflects the large uncertainties in estimates of how hydrogen technologies will develop over the course of the next thirty years. Policy recommendations are drawn from these results and a clear opportunity for future work is outlined. Most notably the results from this study should be compared with research investigating the investments required to decarbonize the heavy-duty vehicle sectors with alternative technologies such as battery-electric trucks biodiesel and catenary systems. Such a comparison would ensure that the most cost effective decarbonization strategy is employed.