Publications

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.

Future pathways for Great Britain’s energy system decarbonization have highlighted the importance of lowcarbon hydrogen as an energy carrier and demand flexibility support. However the potential application within various sectors (heating industry transport) and production capacity through different technologies (methane reformation with carbon capture biomass gasification electrolysis) is highly varying introducing substantial uncertainties for hydrogen infrastructure development. This study sets out infrastructure priorities and identifies locational flexibility for hydrogen supply and demand options. Advances on limitations of previous research are made by developing an open-source model of the hydrogen system of Great Britain based on three Net Zero scenarios set out by National Grid in their Future Energy Scenarios in high temporal and spatial resolution. The model comprehensively covers demand sectors and supply options in addition to extending the locational considerations of the Future Energy Scenarios. This study recommends prioritizing the establishment of green hydrogen hubs in the near-term aligning with demands for synthetic fuels production industry and power which can facilitate the subsequent roll out of up to 10GW of hydrogen production capacity by 2050. The analysis quantifies a high proportion of hydrogen supply and demand which can be located flexibly.

This study proposes a country-based life-cycle assessment (LCA) of several conversion pathways related 10 to both on grid-connected Power-to-X (PtX) fuels and advanced biofuel production for maritime transport 11 in Europe. We estimate the biomass resource availability (both agricultural and forest residues and 12 second-generation energy crops from abandoned cropland) electricity mix and a future-oriented 13 prospective LCA to assess how future climate change mitigation policies influence the results. Our results 14 indicate that the potential of PtX fuels to achieve well-to-wake greenhouse gas intensities lower than 15 those of fossil fuels is limited to countries with a carbon intensity of the electricity mix below 100 gCO2eq kWh-1 16 . The more ambitious FuelEU Maritime goal could be achieved with PtX only if connected to electricity sources below ca. 17 gCO2eq kWh-1 17 which can become possible for most of the national 18 electricity mix in Europe by 2050 if renewable energy sources will become deployed at large scales. For 19 drop-in and hydrogen-based biofuels biomass residues have a higher potential to reduce emissions than 20 dedicated energy crops. In Europe the potentials of energy supply from all renewable and low-carbon 21 fuels (RLFs) range from 32-149% of the current annual fuel consumption in European maritime transport. 22 The full deployment of RLFs with carbon capture and storage technologies could mitigate up to 184% of 23 the current well-to-wake shipping emissions in Europe. Overall our study highlights how the strategic use 24 of both hydrogen-based biofuels and PtX fuels can contribute to the climate mitigation targetsfor present 25 and future scenarios of European maritime transport.

A promising energy carrier and storage solution for integrating renewable energies into the power grid currently being investigated is hydrogen produced via electrolysis. It already serves various purposes but it might also enable the development of hydrogen-based electricity storage systems made up of electrolyzers hydrogen storage systems and generators (fuel cells or engines). The adoption of hydrogen-based technologies is strictly linked to the electrification of end uses and to multicarrier energy grids. This study introduces a generic method to integrate and optimize the sizing and operation phases of hydrogen-based power systems using an energy hub optimization model which can manage and coordinate multiple energy carriers and equipment. Furthermore the uncertainty related to renewables and final demands was carefully assessed. A case study on an urban microgrid with high hydrogen demand for mobility demonstrates the method’s applicability showing how the multi-objective optimization of hydrogen-based power systems can reduce total costs primary energy demand and carbon equivalent emissions for both power grids and mobility down to  −145%. Furthermore the adoption of the uncertainty assessment can give additional benefits allowing a downsizing of the equipment.

The technique of producing hydrogen by utilizing green and renewable energy sources is called green hydrogen production. Therefore by implementing this technique hydrogen will become a sustainable and clean energy source by lowering greenhouse gas emissions and reducing our reliance on fossil fuels. The key beneft of producing green hydrogen by utilizing green energy is that no harmful pollutants or greenhouse gases are directly released throughout the process. Hence to guarantee all of the environmental advantages it is crucial to consider the entire hydrogen supply chain involving storage transportation and end users. Hydrogen is a promising clean energy source and targets plan pathways towards decarbonization and net-zero emissions by 2050. This paper has highlighted the techniques for generating green hydrogen that are needed for a clean environment and sustainable energy solutions. Moreover it summarizes an overview outlook and energy transient of green hydrogen production. Consequently its perspective provides new insights and research directions in order to accelerate the development and identify the potential of green hydrogen production.

The Next Generation EU plan fosters the development of a large capacity for hydrogen generation. However water and energy resources are strictly connected to an indissoluble nexus. For that water electrolysis may counteract the coexistence of two primary UNO Sustainable Development Goals humankind must face to achieve a prosperous and equal society namely SDG 7 (Affordable access to renewable energy sources) and SDG 6 (clean water). To design innovative energy systems implementing hydrogen as an efficient and sustainable vector water resources need careful management and energy use ought not to compete with freshwater delivery. Therefore the present study reviews the technologies available for hydrogen production and their fitness to water quality standards. Among the feeding possibilities to be scrutinized wastewaters and saline waters are worth attention. Each source of water asks for a specific design and management of the water treatment pre-process. Since these steps are energydemanding in some applications the direct use of low-quality water to produce hydrogen may be envisaged. An example is the direct feeding of seawater to Solid Oxide Electrolysers (SOE). SOEs appear more promising than commercial low-temperature electrolysis systems since water steam production integrates the function of preliminary water treatment.

The conversion of solar to chemical energy is one of the central processes considered in the emerging renewable energy economy. Hydrogen production from water splitting over particulate semiconductor catalysts has often been proposed as a simple and a cost-effective method for largescale production. In this review we summarize the basic concepts of the overall water splitting (in the absence of sacrificial agents) using particulate photocatalysts with a focus on their synthetic methods and the role of the so-called “co-catalysts”. Then a focus is then given on improving light absorption in which the Z-scheme concept and the overall system efficiency are discussed. A section on reactor design and cost of the overall technology is given where the possibility of the different technologies to be deployed at a commercial scale and the considerable challenges ahead are discussed. To date the highest reported efficiency of any of these systems is at least one order of magnitude lower than that deserving consideration for practical applications.

By passing the delegated acts supplementing the revised Renewable Energy Directive the European Commission has recently set a regulatory benchmark for the classifcation of green hydrogen in the European Union. Controversial reactions to the restricted power purchase for electrolyser operation refect the need for more clarity about the efects of the delegated acts on the cost and the renewable characteristics of green hydrogen. To resolve this controversy we compare diferent power purchase scenarios considering major uncertainty factors such as electricity prices and the availability of renewables in various European locations. We show that the permission for unrestricted electricity mix usage does not necessarily lead to an emission intensity increase partially debilitating concerns by the European Commission and could notably decrease green hydrogen production cost. Furthermore our results indicate that the transitional regulations adopted to support a green hydrogen production ramp-up can result in similar cost reductions and ensure high renewable electricity usage.

Zero-carbon-dioxide-emitting hydrogen-powered aircraft have in recent decades come back on the stage as promising protagonists in the fght against global warming. The main cause for the reduced performance of liquid hydrogen aircraft lays in the fuel storage which demands the use of voluminous and heavy tanks. Literature on the topic shows that the optimal fuel storage solution depends on the aircraft range category but most studies disagree on which solution is optimal for each category. The objective of this research was to identify and compare possible solutions to the integration of the hydrogen fuel containment system on regional short/medium- and large passenger aircraft and to understand why and how the optimal tank integration strategy depends on the aircraft category. This objective was pursued by creating a design and analysis framework for CS-25 aircraft capable of appreciating the efects that diferent combinations of tank structure fuselage diameter tank layout shape venting pressure and pressure control generate at aircraft level. Despite that no large diferences among categories were found the following main observations were made: (1) using an integral tank structure was found to be increasingly more benefcial with increasing aircraft range/size. (2) The use of a forward tank in combination with the aft one appeared to be always benefcial in terms of energy consumption. (3) The increase in fuselage diameter is detrimental especially when an extra aisle is not required and a double-deck cabin is not feasible. (4) Direct venting has when done efciently a small positive efect. (5) The optimal venting pressure varies with the aircraft confguration performance and mission. The impact on performance from sizing the tank for missions longer than the harmonic one was also quantifed.

Many developing countries seek to participate in the emerging global green hydrogen industry not only as exporters of green hydrogen and its derivatives to Europe and the Far East but also to use it for their own energy security and green transition. They hope that new development paths will lead to late-comer industrialisation. This article assesses corresponding prospects in Chile and Namibia two countries that pursue particularly ambitious plans on green hydrogen. To better understand the chances for path creation ex ante the authors draft an innovative framework that refers to context factors – that is structure – and three types of transformative agency. Against the backdrop of information from secondary sources and a series of expert interviews they uncover sound institutional reforms and initiatives of place-based leadership to promote the green hydrogen industry. However Chile and Namibia lack Schumpeterian entrepreneurship. It therefore remains to be seen whether new development paths will be inclusive contributing to in-country development. Typical downsides of extractive industries in resource peripheries might occur.