Production & Supply Chain

This paper explores the opportunities for and progress in establishing a social licence to operate (SLO) for CCS in industrial clusters in the UK focusing on the perspectives of key stakeholders. The evolution of narratives and networks relating to geographical clusters as niches for CCS in industrial decarbonisation is evaluated in relation to seven pillars supporting SLO. Evidence is drawn from a combination of cluster mapping documentary analysis and stakeholder interviews to identify the wider contexts underpinning industrial decarbonisation stakeholder networks interaction and communication critical narratives the conditions for establishing trust and confidence different scales of social licence and maintaining a SLO. The delivery of a sustainable industrial decarbonisation strategy will depend on multiple layers of social licence involving discourses at different scales and potentially for different systems (heat transport different industrial processes). Despite setbacks as a result of funding cancellations and changes to government policy the UK is positioned to be at the forefront of CCS deployment. While there is a high ambition and a strong narrative from government of the urgency to accelerate projects involving CCS clear coordinated strategy and funding frameworks are necessary to build confidence that UK policy is both compatible with net zero and economically viable.

Solar H2 production is considered as a potentially promising way to utilizesolar energy and tackle climate change stemming from the combustion of fossil fuels.Photocatalytic photoelectrochemical photovoltaic−electrochemical solar thermochem-ical photothermal catalytic and photobiological technologies are the most intensivelystudied routes for solar H2 production. In this Focus Review we provide a comprehensivereview of these technologies. After a brief introduction of the principles and mechanisms ofthese technologies the recent achievements in solar H2 production are summarized with aparticular focus on the high solar-to-H 2 (STH) conversion efficiency achieved by eachroute. We then comparatively analyze and evaluate these technologies based on the metricsof STH efficiency durability economic viability and environmental sustainability aimingto assess the commercial feasibility of these solar technologies compared with currentindustrial H 2 production processes. Finally the challenges and prospects of future researchon solar H2 production technologies are presented.

One of the emerging and environmentally friendly technologies is the photoelectrochemical generation of green hydrogen; however the cheap cost of production and the need for customizing photoelectrode properties are thought to be the main obstacles to the widespread adoption of this technology. The primary players in hydrogen production by photoelectrochemical (PEC) water splitting which is becoming more common on a worldwide basis are solar renewable energy and widely available metal oxide based PEC electrodes. This study attempts to prepare nanoparticulate and nanorod-arrayed films to better understand how nanomorphology can impact structural optical and PEC hydrogen production efficiency as well as electrode stability. Chemical bath deposition (CBD) and spray pyrolysis are used to create ZnO nanostructured photoelectrodes. Various characterization methods are used to investigate morphologies structures elemental analysis and optical characteristics. The crystallite size of the wurtzite hexagonal nanorod arrayed film was 100.8 nm for the (002) orientation while the crystallite size of nanoparticulate ZnO was 42.1 nm for the favored (101) orientation. The lowest dislocation values for (101) nanoparticulate orientation and (002) nanorod orientation are 5.6 × 10−4 and 1.0 × 10−4 dislocation/nm2 respectively. By changing the surface morphology from nanoparticulate to hexagonal nanorod arrangement the band gap is decreased to 2.99 eV. Under white and monochromatic light irradiation the PEC generation of H2 is investigated using the proposed photoelectrodes. The solar-to-hydrogen conversion rate of ZnO nanorod-arrayed electrodes was 3.72% and 3.12% respectively under 390 and 405 nm monochromatic light which is higher than previously reported values for other ZnO nanostructures. The output H2 generation rates for white light and 390 nm monochromatic illuminations were 28.43 and 26.11 mmol.h−1 cm−2 respectively. The nanorod-arrayed photoelectrode retains 96.6% of its original photocurrent after 10 reusability cycles compared to 87.4% for the nanoparticulate ZnO photoelectrode. The computation of conversion efficiencies H2 output rates Tafel slope and corrosion current as well as the application of low-cost design methods for the photoelectrodes show how the nanorod-arrayed morphology offers low-cost high-quality PEC performance and durability.

The production of synthetic fuels and chemicals from solar energy and abundant reagents offers a promising pathway to a sustainable fuel economy and chemical industry. For the production of hydrogen photoelectrochemical or integrated photovoltaic and electrolysis devices have demonstrated outstanding performance at the lab scale but there remains a lack of larger-scale on-sun demonstrations (>100 W). Here we present the successful scaling of a thermally integrated photoelectrochemical device—utilizing concentrated solar irradiation— to a kW-scale pilot plant capable of co-generation of hydrogen and heat. A solar-to-hydrogen device-level efficiency of greater than 20% at an H2 production rate of >2.0 kW (>0.8 g min−1) is achieved. A validated model-based optimization highlights the dominant energetic losses and predicts straightforward strategies to improve the system-level efficiency of >5.5% towards the device-level efficiency. We identify solutions to the key technological challenges control and operation strategies and discuss the future outlook of this emerging technology.

The use of green hydrogen as a high-energy fuel of the future may be an opportunity to balance the unstable energy system which still relies on renewable energy sources. This work is a comprehensive review of recent advancements in green hydrogen production. This review outlines the current energy consumption trends. It presents the tasks and challenges of the hydrogen economy towards green hydrogen including production purification transportation storage and conversion into electricity. This work presents the main types of water electrolyzers: alkaline electrolyzers proton exchange membrane electrolyzers solid oxide electrolyzers and anion exchange membrane electrolyzers. Despite the higher production costs of green hydrogen compared to grey hydrogen this review suggests that as renewable energy technologies become cheaper and more efficient the cost of green hydrogen is expected to decrease. The review highlights the need for cost-effective and efficient electrode materials for large-scale applications. It concludes by comparing the operating parameters and cost considerations of the different electrolyzer technologies. It sets targets for 2050 to improve the efficiency durability and scalability of electrolyzers. The review underscores the importance of ongoing research and development to address the limitations of current electrolyzer technology and to make green hydrogen production more competitive with fossil fuels.

Electrolytic hydrogen from renewable sources is central to many nations' net-zero emission strategies serving as a low-carbon alternative for traditional uses and enabling decarbonisation across multiple sectors. Current stringent policies in the EU and US are set to soon require hourly time-matching of renewable electricity generation used by electrolysers aimed at ensuring that hydrogen production does not cause significant direct or indirect emissions. Whilst such requirements enhance the “green credentials” of hydrogen they also increase its production costs. A modest relaxation of these requirements offers a practicable route for scaling up low-carbon hydrogen production optimising both costs and emission reductions. Moreover in jurisdictions with credible and near-to-medium-term decarbonisation targets immediate production of electrolytic hydrogen utilising grid electricity would have a lifetime carbon intensity comparable to or even below blue hydrogen and very significantly less than that of diesel emphasising the need to prioritise rapid grid decarbonisation of the broader grid.

Biohydrogen a low-carbon footprint technology can play a significant role in decarbonizing the energy system. It uses existing infrastructure is easily transportable and produces no greenhouse gas emissions. Four technologies can be used to produce biohydrogen: photosynthetic biohydrogen dark fermentation (DF) photo-fermentation and microbial electrolysis cells (MECs). DF produces more biohydrogen and is flexible with organic substrates making it a sustainable method of waste repurposing. However low achievable biohydrogen yields are a common issue. To overcome this catalytic mechanisms including enzymatic systems such as [Fe-Fe]- and [Ni-Fe]-hydrogenases in DF and electroactive microbial consortia in MECs alongside advanced electrode catalysts which collectively surmount thermodynamic and kinetic constraints and the two stage system such as DF connection to photo-fermentation and anaerobic digestion (AD) to microbial electrolysis cells (MECs) have been investigated. MECs can generate biohydrogen at better yields by using sugars or organic acids and combining DF and MEC technologies could improve biohydrogen production. As such this review highlights the challenges and possible solutions for coupling DF–MEC while also offering knowledge regarding the technical and microbiological aspects.

The article discusses a regenerative heat exchange system for a solid oxide electrolyzer cell (SOEC) used in the production of green hydrogen. The heating system comprises four heat exchangers one condenser heat exchanger and a mixer evaporator. A pump and two throttle valves have been added to separate the hydrogen at an elevated steam condensation temperature. Assuming steady flow a thermodynamic analysis was performed to validate the design and to predict the main parameters of the heating system. Numerical optimization was then used to determine the optimal temperature distribution ensuring the lowest possible additional external energy requirement for the regenerative system. The proportions of energy gained through heat exchange were determined and their distribution analyzed. The calculated thermal efficiency of the regenerative system is 75% while its exergy efficiency is 73%. These results can be applied to optimize the design of heat exchangers for hydrogen production systems using SOECs.

Hydrogen is a key energy carrier for decarbonizing multiple sectors particularly when produced via water electrolysis powered by renewable energy. Proton exchange membrane (PEM) electrolyzers are well suited for this application due to their ability to rapidly adjust to fluctuating power inputs. Despite being conventionally operated at high temperatures and pressures to reduce heating and compression needs recent studies suggest that under partial loads lower operating conditions may enhance efficiency. This study introduces a novel optimization framework for dynamically adjusting pressure and temperature in PEM electrolyzers. The model integrates an efficiency map within a Mixed-Integer Linear Programming (MILP) formulation and applies McCormick tightening to address nonlinearities. A one-week case study demonstrates operational cost reductions of up to 12.5 % through optimal control favoring lower temperatures and pressures at low current densities and higher temperatures near rated load while maintaining moderate pressures. The results show improved efficiency and reduced hydrogen crossover enhancing safety and enabling scalable application over extended time horizons. These insights are valuable for long-term planning and evaluation of hydrogen production and storage systems.

This study evaluates the feasibility of repurposing produced water—an abundant byproduct of hydrocarbon extraction—for green hydrogen production in Wyoming USA. Analysis of geospatial distribution and production volumes reveals that there are over 1 billion barrels of produced water annually from key basins with a general total of dissolved solids (TDS) ranging from 35000 to 150000 ppm though Wyoming’s sources are often at the lower end of this spectrum. Optimal locations for hydrogen production hubs have been identified particularly in high-yield areas like the Powder River Basin where the top 2% of fields contribute over 80% of the state’s produced water. Detailed water-quality analysis indicates that virtually all of the examined sources exceed direct electrolyzer feed requirements (e.g. 10% LCOH) are notable electricity pricing (50–70% LCOH) and electrolyzer CAPEX (20–40% LCOH) are dominant cost factors. While leveraging produced water could reduce freshwater consumption and enhance hydrogen production sustainability further research is required to optimize treatment processes and assess economic viability under real-world conditions. This study emphasizes the need for integrated approaches combining water treatment renewable energy and policy incentives to advance a circular economy model for hydrogen production.