United Kingdom

The Paris Climate Agreement seeks to keep global temperature increases under 2° Celsius ideally 1.5° Celsius. This goal necessitates significant emission reductions. By 2030 emissions are expected to range between 52 and 58 GtCO2e from their 2016 level of approximately 52 GtCO2e. This review paper explores a number of low and zero-carbon renewable fuels such as hydrogen green ammonia green methanol biomethane natural gas and synthetic methane (with natural gas and synthetic methane subject to CCUS both at processing and at final use) as alternative solutions for providing a way to rebalance transition paths in order to achieve the goals of the Paris Agreement while also reaping the benefits of other sustainability targets. The results show renewables will need to account for approximately 90% of total electricity generation by 2050 and approximately 25% of non-electric energy usage in buildings and industry. However low and zero-carbon renewable fuels currently only contributes about 15% to the global energy shares and it will take about 10% more capacity to reach the 2050 goal. The transportation industry will need to take important steps toward energy efficiency and fuel switching in order to achieve the 20% emission reduction. Therefore significant new commitments to efficient low-carbon alternatives will be necessary to make this enormous change. According to this paper investing in energy efficiency and lowcarbon alternative energy must rise by a factor of about five by 2050 in comparison to 2015 levels if the 1.5 °C target is to be realised.

Hydrogen spark-ignition direct-injection engines result in no carbon emissions at use but NOX remains a challenge. This study demonstrates that with lean combustion (ϕ < 0.38) in-cylinder NOX can be reduced to a quarter of the current maritime regulatory limit. An original contribution of this work is the use of speciesresolved emissions formation across multiple engine load conditions. A novel chemically detailed combustion modelling framework was developed in CHEMKIN-Pro incorporating the evolution of the CRECK C1–C3 NOX mechanism for improved high-pressure accuracy. The framework was extensively validated using crank-angleresolved data across 9–18 bar loads. The model accurately reproduced pressure traces heat release angles and NOX. Mechanistic analysis revealed a shift from thermal Zeldovich NOX to intermediate-species (notably N2Odriven) as equivalence ratio and pressure varied. The findings highlighted the use of a high-fidelity chemical kinetic modelling framework not only to match experimental results but to gain physically grounded insight into actionable near-zero emission strategies.

The main aim of this study deals with the potential evaluation of a fluidized bed membrane reactor (FBMR) for hydrogen production as a clean fuel carrier via methanol steam reforming reaction comparing its performance with other reactors including packed bed membrane reactors (PBMR) fluidized bed reactors (FBR) and packed bed reactors (PBR). For this purpose a two-dimensional axisymmetric numerical model was developed using computational fluid dynamics (CFD) to simulate the reactor performances. Model accuracy was validated by comparing the simulation results for PBMR and PB with experimental data showing an accurate agreement within them. The model was then employed to examine the effects of key operating parameters including reaction temperature pressure steam-to-methanol molar ratio and gas volumetric space velocity on reactor performance in terms of methanol conversion hydrogen yield hydrogen recovery and selectivity. At 573 K 1 bar a feed molar ratio of 3/1 and a space velocity of 9000 h−1 the PBMR reached the best results in terms of methanol conversion hydrogen yield hydrogen recovery and hydrogen selectivity such as 67.6% 69.5% 14.9% and 97.1% respectively. On the other hand the FBMR demonstrated superior performance with respect to the latter reaching a methanol conversion of 98.3% hydrogen yield of 95.8% hydrogen recovery of 74.5% and hydrogen selectivity of 97.4%. These findings indicate that the FBMR offers significantly better performance than the other reactor types studied in this work making it a highly efficient method for hydrogen production through methanol steam reforming and a promising pathway for clean energy generation.

Multi-energy microgrids (MEMGs) with green hydrogen have attracted significant research attention for their benefits such as energy efficiency improvement carbon emission reduction as well as line congestion alleviation. However the complexities of multi-energy networks coupled with diverse uncertainties may threaten MEMG’s operation. In this paper a data-driven methodology is proposed to achieve effective MEMG operation considering the green hydrogen technique and congestion management. First a detailed MEMG modelling approach is developed coupling with electricity green hydrogen natural gas and thermal flows. Different from conventional MEMG models hydrogen-enriched compressed natural gas (HCNG) models and weatherdependent power flow are thoroughly considered in the modelling. Meanwhile the power flow congestion problem is also formulated in the MEMG operation which could be mitigated through HCNG integration. Based on the proposed MEMG model a reinforcement learning-based method is designed to obtain the optimal solution of MEMG operation. To ensure the solution’s safety a soft actor-critic (SAC) algorithm is applied and modified by leveraging the Lagrangian relaxation and safety layer scheme. In the end case studies are conducted and presented to validate the effectiveness of the proposed method.

High-emitting industrial processes are often concentrated in clusters that share infrastructure to maximise efficiency and reduce costs. These clusters prevalent in many industrialised economies pose significant challenges for decarbonisation due to their dependence on energy-intensive systems and legacy assets. Carbon capture and storage (CCS) is frequently promoted as a key solution for reducing emissions in these hard-to-abate sectors. Drawing on an adapted ‘Multi-Level Perspective’ framework (Geels and Turnheim 2022) this paper examines how industrial practices are being reconfigured in response to decarbonisation imperatives. While our study focuses on the UK the findings have broader relevance to other industrialised nations pursuing a similar strategy. We observe a dominant reliance on fuel switching and CCS characterising the innovation style as ‘modular substitution’; incremental changes that replace individual components without fundamentally transforming the overall system. This pattern suggests a gap between ambitious climate commitments and the depth of systemic change being pursued. Without more comprehensive strategies there is a growing risk of delayed emissions reductions and increased residual emissions both contributing to the overshooting of carbon budgets which will be compounded if replicated across industrial sectors worldwide.

Hydrogen is a promising fuel to decarbonise aviation. Storage in liquid form is favoured for long-haul aircraft; storage as a high-pressure gas is preferred otherwise. The exergy expended during the compression or liquefaction process is stored as physical exergy in the fuel. Most discussions around hydrogen-fuelled aviation ignore this very significant exergy content. When combusted in an engine the chemical energy of hydrogen can produce around 60 MJ of work per kg. The work that can be extracted from the physical exergy depends strongly on the method used. This paper presents an exergy analysis considering a range of storage conditions operating conditions and work-extraction methods. For reasonable gas-turbine operating conditions upwards of 16 MJ/kg might be extracted from compressed hydrogen (at 700 bar) and 30 MJ/kg from LH2. This additional work representing 25–50 % of the shaft work produced by combustion has been by and large neglected.

The transport sector is a major contributor to greenhouse gas emissions largely due to its dependence on fossil fuels. Electrifying transport through Battery Electric Vehicles (BEVs) and Hydrogen Fuel Cell Electric Vehicles (FCEVs) is widely recognized as a key pathway to reducing emissions. While both BEVs and FCEVs are zero-emission during operation they still require electricity to function. Sourcing this electricity from solar energy presents a promising opportunity for sustainable operation. The novelty of this work lies in exploring how solar energy can be effectively integrated into both BEV and FCEV systems. The paper examines the potential scope and infrastructure requirements of these vehicle types as well as innovative charging and refuelling strategies. For BEVs charging options include fixed charging stations battery swapping stations and wireless charging. In the context of solar integration photovoltaic (PV) systems can be mounted directly on the vehicle body or used to power charging stations. While current PV efficiency and reliability are insufficient to meet the full energy demand of BEVs they can provide valuable auxiliary power. For FCEVs solar energy can be utilized for hydrogen production enabling the concept of solar-powered FCEVs. Refuelling options include onsite and offsite hydrogen production facilities as well as mobile refuelling units. In both cases land requirements for PV installations are significant. Alternatives to ground-mounted PV such as floating PV or agrivoltaics (agriPV) should be considered to optimize land use. While solar-powered charging or refuelling stations are technically feasible complete reliance on solar power alone is not yet practical. A hybrid approach with grid connections energy storage or backup generation remains necessary to ensure consistent energy availability. For BEVs the cost of charging particularly for long-distance travel where rapid charging is required remains a barrier. For FCEVs challenges include the high cost of hydrogen production and the limited availability of refuelling infrastructure despite their advantage of fast refuelling times. Government policies and incentives are playing a critical role in overcoming these barriers fostering investment in infrastructure and accelerating the transition toward a cleaner transport sector. In summary integrating solar energy into BEV and FCEV infrastructure can advance sustainable mobility by reducing lifecycle emissions. While current PV efficiency storage and hydrogen production limitations require hybrid energy solutions ongoing technological improvements and supportive policies can enable broader adoption. A balanced renewable energy mix with solar as a key component will be essential for realizing truly sustainable zero-emission transport.

Effective water management is crucial for the optimal performance and durability of proton exchange membrane fuel cells (PEMFCs) in automotive applications. Conventional techniques like electrochemical impedance spectroscopy (EIS) face challenges in accurately measuring high-frequency resistance (HFR) impedance during dynamic vehicle operations. This study proposes a novel stack water management stability control and vehicle energy control method to address these limitations. Simulation and experimental results demonstrate improved system and powertrain efficiency extended stack lifespan and optimized hydrogen consumption. These findings contribute to advancing robust water management strategies supporting the transition toward sustainable zero-emission fuel cell vehicles.

Green hydrogen is likely to play a major role in decarbonising the aviation industry. It is crucial to understand the effects of microstructure on hydrogen redistribution which may be implicated in the embrittlement of candidate fuel system metals. We have developed a multiscale finite element modelling framework that integrates micromechanical and hydrogen transport models such that the dominant microstructural effects can be efficiently accounted for at millimetre length scales. Our results show that microstructure has a significant effect on hydrogen localisation in elastically anisotropic materials which exhibit an interesting interplay between microstructure and millimetre-scale hydrogen redistribution at various loading rates. Considering 316L stainless steel and nickel a direct comparison of model predictions against experimental hydrogen embrittlement data reveals that the reported sensitivity to loading rate may be strongly linked with rate-dependent grain scale diffusion. These findings highlight the need to incorporate microstructural characteristics in hydrogen embrittlement models.

As global demand for green hydrogen rises potential hydrogen exporters move into the spotlight. While exports can bring countries revenue large-scale on-grid hydrogen electrolysis for export can profoundly impact domestic energy prices and energy-related emissions. Our investigation explores the interplay of hydrogen exports domestic energy transition and temporal hydrogen regulation employing a sector-coupled energy model in Morocco. We find substantial co-benefits of domestic carbon dioxide mitigation and hydrogen exports whereby exports can reduce market-based costs for domestic electricity consumers while mitigation reduces costs for hydrogen exporters. However increasing hydrogen exports in a fossil-dominated system can substantially raise market-based costs for domestic electricity consumers but surprisingly temporal matching of hydrogen production can lower these costs by up to 31% with minimal impact on exporters. Here we show that this policy instrument can steer the welfare (re-)distribution between hydrogen exporting firms hydrogen importers and domestic electricity consumers and hereby increases acceptance among actors.