Sweden

Due to their ability to reversibly absorb/desorb hydrogen without hysteresis Pd–Au nanoalloys have been proposed as materials for hydrogen sensing. For sensing it is important that absorption/desorption isotherms are reproducible and stable over time. A few studies have pointed to the influence of short and long range chemical order on these isotherms but many aspects of the impact of chemical order have remained unexplored. Here we use alloy cluster expansions to describe the thermodynamics of hydrogen in Pd–Au in a wide concentration range. We investigate how different chemical orderings corresponding to annealing at different temperatures as well as different external pressures of hydrogen impact the behavior of the material with focus on its hydrogen absorption/desorption isotherms. In particular we find that a long-range ordered L12 phase is expected to form if the H₂ pressure is sufficiently high. Furthermore we construct the phase diagram at temperatures from 250 K to 500 K showing that if full equilibrium is reached in the presence of hydrogen phase separation can often be expected to occur in stark contrast to the phase diagram in para-equilibrium. Our results explain the experimental observation that absorption/desorption isotherms in Pd–Au are often stable over time but also reveal pitfalls for when this may not be the case.

More than 2000 h of solid-fuel CLC operation in a number of smaller pilot units clearly indicate that the concept works. A scale-up of the technology to 1000 MWth is investigated in terms of mass and heat balances flows solids inventories boiler dimensions and the major differences between a full-scale Circulating Fluidized-Bed (CFB) boiler and a Chemical-Looping Combustion CFB (CLC–CFB). Furthermore the additional cost of CLC–CFB relative to CFB technology is analysed and found to be 20 €/tonne CO2. The largest cost is made up of compression of CO2 which is common to all capture technologies. Although the need for oxygen to manage incomplete conversion is estimated to be only a tenth of that of oxy-fuel combustion oxygen production is nonetheless the second largest cost. Other significant costs include oxygen-carrier material increased boiler cost and steam for fluidization of the fuel reactor.

This review article provides a comprehensive overview of the fundamentals modelling approaches experimental studies and challenges associated with hydrogen gas flow in pipelines. It elucidates key aspects of hydrogen gas flow including density compressibility factor and other relevant properties crucial for understanding its behavior in pipelines. Equations of state are discussed in detail highlighting their importance in accurately modeling hydrogen gas flow. In the subsequent sections one-dimensional and three-dimensional modelling techniques for gas distribution networks and localized flow involving critical components are explored. Emphasis is placed on transient flow friction losses and leakage characteristics shedding light on the complexities of hydrogen pipeline transportation. Experimental studies investigating hydrogen pipeline transportation dynamics are outlined focusing on the impact of leakage on surrounding environments and safety parameters. The challenges and solutions associated with repurposing natural gas pipelines for hydrogen transport are discussed along with the influence of pipeline material on hydrogen transportation. Identified research gaps underscore the need for further investigation into areas such as transient flow behavior leakage mitigation strategies and the development of advanced modelling techniques. Future perspectives address the growing demand for hydrogen as a clean energy carrier and the evolving landscape of hydrogen-based energy systems.

Direct solar hydrogen generation via a combination of photovoltaics (PV) andwater electrolysis can potentially ensure a sustainable energy supply whileminimizing greenhouse emissions. The PECSYS project aims at demonstrating asolar-driven electrochemical hydrogen generation system with an area >10 m 2with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers(ECs) using thin-film silicon undoped and silver-doped Cu(InGa)Se 2 and siliconheterojunction PV combined with alkaline electrolysis to form one unit aredeveloped on a prototype level with solar collection areas in the range from 64 to2600 cm 2 with the solar-to-hydrogen (StH) efficiency ranging from 4 to 13%.Electrical direct coupling of PV modules to a proton exchange membrane EC totest the effects of bifaciality (730 cm 2 solar collection area) and to study the long-term operation under outdoor conditions (10 m 2 collection area) is also inves-tigated. In both cases StH efficiencies exceeding 10% can be maintained over thetest periods used. All the StH efficiencies reported are based on measured gasoutflow using mass flow meters.

The present study investigates four factors that govern the ability to supply hydrogen at a low cost in Europe: the scale of the hydrogen demand; the possibility to invest in large-scale hydrogen storage; process flexibility in hydrogen-consuming industries; and the geographical areas in which hydrogen demand arises. The influence of the hydrogen demand on the future European zero-emission electricity system is investigated by applying the cost-minimising electricity system investment model eNODE to hydrogen demand levels in the range of 0–2500 TWhH2. It is found that the majority of the future European hydrogen demand can be cost-effectively satisfied with VRE assuming that the expansion of wind and solar power is not hindered by a lack of social acceptance at a cost of around 60–70 EUR/MWhH2 (2.0–2.3 EUR/kgH2). The cost of hydrogen in Europe can be reduced by around 10 EUR/MWhH2 if the hydrogen consumption is positioned strategically in regions with good conditions for wind and solar power and a low electricity demand. The cost savings potential that can be obtained from full temporal flexibility of hydrogen consumption is 3-fold higher than that linked to strategic localisation of the hydrogen consumption. The cost of hydrogen per kg increases and the value of flexibility diminishes as the size of the hydrogen demand increases relative to the traditional demand for electricity and the available VRE resources. Low-cost hydrogen is thus achieved by implementing efficiency and flexibility measures for hydrogen consumers as well as increasing acceptance of VRE.

Anion exchange membrane water electrolysis (AEMWE) is a potentially low-cost and sustainable technology for hydrogen production that combines the advantages of proton exchange membrane water electrolysis and traditional alkaline water electrolysis systems. Despite considerable research efforts in recent years the medium-term (100 h) stability of Aemion™ membranes needs further investigation. This work explores the chemical and electrochemical durability (>100 h) of Aemion™ anion exchange membranes in a flow cell using nickel felt as the electrode material on the anode and cathode sides. Remixing the electrolytes between the AEMWE galvanostatic tests was very important to enhance electrolyte refreshment and the voltage stability of the system. The membranes were analyzed by NMR spectroscopy after the AEMWE tests and the results showed no sign of severe chemical degradation. In a separate experiment the chemical stability and mechanical integrity of the membranes were studied by soaking them in a strongly alkaline electrolyte for a month (>700 h) at 90 C followed by NMR analysis. A certain extent of ionic loss was observed due to chemical degradation and the membranes disintegrated into small pieces.

Maritime transport faces increasing pressure to reduce its greenhouse gas emissions to be in accordance with the Paris Agreement. For this to happen low- and zero-carbon energy solutions need to be developed. In this paper we draw on sustainability transition literature and introduce the technological innovation system (TIS) framework to the field of maritime transportation research. The TIS approach analytically distinguishes between different innovation system functions that are important for new technologies to develop and diffuse beyond an early phase of experimentation. This provides a basis for technology-specific policy recommendations. We apply the TIS framework to the case of battery-electric and hydrogen energy solutions for coastal maritime transport in Norway. Whereas both battery-electric and hydrogen solutions have developed rapidly the former is more mature and has a strong momentum. Public procurement and other policy instruments have been crucial for developments to date and will be important for these technologies to become viable options for shipping more generally.

Gas switching reforming (GSR) is a promising technology for natural gas reforming with inherent CO₂ capture. Like conventional steam methane reforming (SMR) GSR can be integrated with CO₂ -gas shift and pressure swing adsorption units for pure hydrogen production. The resulting GSR-H2 process concept was techno-economically assessed in this study. Results showed that GSR-H2 can achieve 96% CO₂ capture at a CO₂ avoidance cost of 15 $/ton (including CO₂ transport and storage). Most components of the GSR-H2 process are proven technologies but long-term oxygen carrier stability presents an important technical uncertainty that can adversely affect competitiveness when the material lifetime drops below one year. Relative to the SMR benchmark GSR-H2 replaces some fuel consumption with electricity consumption making it more suitable to regions with higher natural gas prices and lower electricity prices. Some minor alterations to the process configuration can adjust the balance between fuel and electricity consumption to match local market conditions. The most attractive commercialization pathway for the GSR-H2 technology is initial construction without CO2 capture followed by simple retrofitting for CO₂ capture when CO₂ taxes rise and CO₂ transport and storage infrastructure becomes available. These features make the GSR-H2 technology robust to almost any future energy market scenario.

There is a need for alternative marine fuels in order to reduce the environmental and climate impacts of shipping in the short and long term. This study assesses the prospects for seven alternative fuels for the shipping sector in 2030 including biofuels by applying a multi-criteria decision analysis approach that is based on the estimated fuel performance and on input from a panel of maritime stakeholders and by considering explicitly the influence of stakeholder preferences. Seven alternative marine fuels—liquefied natural gas (LNG) liquefied biogas (LBG) methanol from natural gas renewable methanol hydrogen for fuel cells produced from (i) natural gas or (ii) electrolysis based on renewable electricity and hydrotreated vegetable oil (HVO)—and heavy fuel oil (HFO) as benchmark are included and ranked by ten performance criteria and their relative importance. The criteria cover economic environmental technical and social aspects. Stakeholder group preferences (i.e. the relative importance groups assign to the criteria) influence the ranking of these options. For ship-owners fuel producers and engine manufacturers economic criteria in particular the fuel price are the most important. These groups rank LNG and HFO the highest followed by fossil methanol and then various biofuels (LBG renewable methanol and HVO). Meanwhile representatives from Swedish government authorities prioritize environmental criteria specifically GHG emissions and social criteria specifically the potential to meet regulations ranking renewable hydrogen the highest followed by renewable methanol and then HVO. Policy initiatives are needed to promote the introduction of renewable marine fuels.

Climate change and increased urban population are two major concerns for society. Moving towards more sustainable energy solutions in the urban context by integrating renewable energy technologies supports decarbonizing the energy sector and climate change mitigation. A successful transition also needs adequate consideration of climate change including extreme events to ensure the reliable performance of energy systems in the long run. This review provides an overview of and insight into the progress achieved in the energy sector to adapt to climate change focusing on the climate resilience of urban energy systems. The state-of-the-art methodology to assess impacts of climate change including extreme events and uncertainties on the design and performance of energy systems is described and discussed. Climate resilience is an emerging concept that is increasingly used to represent the durability and stable performance of energy systems against extreme climate events. However it has not yet been adequately explored and widely used as its definition has not been clearly articulated and assessment is mostly based on qualitative aspects. This study reveals that a major limitation in the state-of-the-art is the inadequacy of climate change adaptation approaches in designing and preparing urban energy systems to satisfactorily address plausible extreme climate events. Furthermore the complexity of the climate and energy models and the mismatch between their temporal and spatial resolutions are the major limitations in linking these  models. Therefore few studies have focused on the design and operation of urban energy infrastructure in terms of climate resilience. Considering the occurrence of extreme climate events and increasing demand for implementing climate adaptation strategies the study highlights the importance of improving energy system models to consider future climate variations including extreme events to identify climate resilient energy transition pathways.