Production & Supply Chain

An energy source transition is necessary to realize carbon neutrality emphasizing the importance of a hydrogen economy. The transportation sector accounted for 27% of annual carbon emissions in 2019 highlighting the increasing importance of transitioning to hydrogen vehicles and establishing hydrogen refueling stations (HRSs). In particular HRSs need to be prioritized for deploying hydrogen vehicles and developing hydrogen supply chains. Thus research on HRS is important for achieving carbon neutrality in the transportation sector. In this study we improved the efficiency and scaled up the capacity of an on-site HRS (based on steam methane reforming with a hydrogen production rate of 30 Nm3/h) in Seoul Korea. This HRS was a prototype with low efficiency and capacity. Its efficiency was increased through thermodynamic analysis and heat exchanger network synthesis. Furthermore the process was scaled up from 30 Nm3/h to 150 Nm3/h to meet future hydrogen demand. The results of exergy analysis indicated that the exergy destruction in the reforming reactor and heat exchanger accounted for 58.1% and 19.8% respectively of the total exergy destruction. Thus the process was improved by modifying the heat exchanger network to reduce the exergy losses in these units. Consequently the thermal and exergy efficiencies were increased from 75.7% to 78.6% and from 68.1% to 70.4% respectively. The improved process was constructed and operated to demonstrate its performance. The operational and simulation data were similar within the acceptable error ranges. This study provides guidelines for the design and installation of low-carbon on-site HRSs.

As new sources of energy and advanced technologies are used there is a continuous evolution in energy supply demand and distribution. Advanced nuclear reactors and clean hydrogen have the opportunity to scale together and diversify the hydrogen production market away from fossil fuel-based production. Nevertheless the technical uncertainties surrounding nuclear hydrogen processes necessitate thorough research and a solid development effort. This paper aims to position pink hydrogen for nuclear hydrogen production at the forefront of sustainable energy-related solutions by offering a comprehensive review of recent advancements in nuclear hydrogen production covering both research endeavors and industrial applications. It delves into various pink hydrogen generation methodologies elucidating their respective merits and challenges. Furthermore this paper analyzes the evolving landscape of pink hydrogen in terms of its levelized cost by comparatively assessing different production pathways. By synthesizing insights from academic research and industrial practices this paper provides valuable perspectives for stakeholders involved in shaping the future of nuclear hydrogen production.

With a limited global carbon budget it is imperative that decarbonisation decisions are based on accurate holistic accounts of all greenhouse gas (GHG) emissions produced to assess their validity. Here the upstream GHG emissions of potential UK offshore Green and Blue hydrogen production are compared to GHG emissions from hydrogen produced through electrolysis using UK national grid electricity and the ‘business-as-usual’ case of continuing to combust methane. Based on an operational life of 25 years and producing 0.5MtH2 per year for each hydrogen process the results show that Blue hydrogen will emit between 200-262MtCO2e of GHG emissions depending on the carbon capture rates achieved (39%–90%) Green hydrogen produced via electrolysis using 100% renewable electricity from offshore wind will emit 20MtCO2e and hydrogen produced via electrolysis powered by the National Grid will emit between 103-168MtCO2e depending of the success of its NetZero strategy. The ‘business-as-usual’ case of continuing to combust methane releases 250MtCO2e over the same lifetime. This study finds that Blue hydrogen at scale is not compatible with the Paris Agreement reduces energy security and will require a substantial GHG emissions investment which excludes it from being a ‘low carbon technology’ and should not be considered for any decarbonisation strategies going forward.

Blue hydrogen is gaining attention as an intermediate step toward achieving eco-friendly green hydrogen production. However the general blue hydrogen production requires an energy-intensive process for carbon capture and storage resulting in low process efficiency. Additionally the hydrogen production processes steam methane reforming (SMR) and electrolysis emits waste heat and byproduct oxygen respectively. To solve these problems this study proposes an oxy-fuel combustion-based blue hydrogen production process that integrates fossil fuel-based hydrogen production and electrolysis processes. The proposed processes are SMR + SOEC and SMR + PEMEC whereas SMR solid oxide electrolysis cell (SOEC) and proton exchange membrane electrolysis cell (PEMEC) are also examined for comparison. In the proposed processes the oxygen produced by the electrolyzer is utilized for oxy-fuel combustion in the SMR process and the resulting flue gas containing CO2 and H2O is condensed to easily separate CO2. Additionally the waste heat from the SMR process is recovered to heat the feed water for the electrolyzer thereby maximizing the process efficiency. Techno-economic sensitivity and greenhouse gas (GHG) analyses were conducted to evaluate the efficiency and feasibility of the proposed processes. The results show that SMR + SOEC demonstrated the highest thermal efficiency (85.2%) and exergy efficiency (80.5%) exceeding the efficiency of the SMR process (78.4% and 70.4% for thermal and exergy efficiencies respectively). Furthermore the SMR + SOEC process showed the lowest levelized cost of hydrogen of 6.21 USD/kgH2. Lastly the SMR + SOEC demonstrated the lowest life cycle GHG emissions. In conclusion the proposed SMR + SOEC process is expected to be a suitable technology for the transition from gray to green hydrogen.

Hydrogen production from sunlight using innovative photocatalytic and photoelectrochemical systems offers decentralized sustainable energy solutions with potential applications in remote off-grid locations.<br/>Photocatalytic hydrogen production has the potential to transform clean cooking by reducing dependency on wood and charcoal in low-resource settings addressing significant health and environmental challenges.<br/>Photocatalytic reactors could also be used to capture atmospheric carbon dioxide and perform artificial photosynthesis mimicking processes found in nature producing green energy molecules.

Rural mini-grids in Ghana often experience substantial midday solar PV generation surpluses due to mismatches between peak production and local demand with excess energy (redundant energy) frequently curtailed once batteries are fully charged. This underutilisation limits the socio-economic benefits of renewable electrification and highlights the need for alternative long-duration storage solutions. This study investigated the technoeconomic feasibility of converting excess PV energy from a 54 kWp mini-grid in Aglakope Ghana into hydrogen via electrolysis storing it and reconverting it to electricity using fuel cells. Redundant energy generation was quantified using measured PV output and load consumption and validated using statistical error metrics (R2 = 0.955). Hydrogen production and recovery potential were modelled for different electrolyser technologies and system performance was evaluated using round-trip efficiency (RTE) levelized cost of hydrogen (LCOH) and levelized cost of storage (LCOS) with comparative analysis against additional battery capacity. The results yielded an average monthly excess energy of about 2250 kWh convertible into 43–53 kg per month of hydrogen depending on electrolyser type. The proposed hydrogen-fuel cell pathway yielded a RTE of 44.4 % LCOH of $4.97/kg and LCOS of $0.249/kWh which is about 13 % higher than lithium-ion storage benchmarks. The study findings demonstrate that hydrogen storage can complement batteries offer seasonal and multi-day storage capability and reduce renewable curtailment. Therefore wider adoption could be supported by cost reductions efficiency improvements and enabling policies positioning hydrogen-based storage as a viable pathway for resilient low-carbon rural electrification in off-grid contexts.

Hydrogen produced from renewable sources is crucial for decarbonizing hard-to-abate sectors and achieving netzero targets. This study examines hydrogen production through the novel thermo-catalytic reforming (TCR) process using agricultural and forestry residues. The research aims to develop and optimize regression models that integrate feedstock properties (ash hydrogen-to-carbon molar ratio and lignin) and process parameters (reactor and reformer temperatures) to predict yields of hydrogen (H2) syngas methane (CH4) and carbon dioxide (CO2). Three biomass feedstocks – softwood pellets (SWPs) hardwood pellets (HWPs) and wheat straw pellets (WSPs) – were analyzed at reactor temperatures of 400–550 ◦C and reformer temperatures of 500–700 ◦C. Predictive models for H2 (R2 = 0.9642 RMSE = 1.0639) and syngas (R2 = 0.9894 RMSE = 0.0140) yields show strong agreement and accuracy between the predicted and experimental values. In contrast the models for CH4 and CO2 yields show higher variability in the predictions. Reformer temperature was the most significant parameter influencing the yields of H2 and syngas. The optimal H2 yields predicted for the model were obtained for HWPs at 550/700 ◦C (26.67 g H2/kg dry biomass) followed by SWPs at 550/700 ◦C (24.11 g H2/kg dry biomass) and WSPs at 550/685.2 ◦C (18.78 g H2/kg dry biomass). The volumetric syngas yields were highest for HWPs at 550/700 ◦C (0.831 Nm3 /kg dry biomass) followed by SWPs (0.777 Nm3 /kg dry biomass) and WSPs (0.634 Nm3 /kg dry biomass). This study demonstrates that regression modelling accurately predicts H2 and syngas yields which would help to expand the applicability of TCR technology for large-scale hydrogen production contributing to the decarbonization of the energy sector.

Sunlight-driven water splitting allows renewable hydrogen to be produced from abundant and environmentally benign water. Large-scale societal implementation of this green fuel production technology within energy generation systems is essential for the establishment of sustainable future societies. Among various technologies photocatalytic water splitting using particulate semiconductors has attracted increasing attention as a method to produce large amounts of green fuels at low cost. The key to making this technology practical is the development of photocatalysts capable of splitting water with high solar-to-fuel energy conversion efficiency. Furthermore advances that enable the deployment of water-splitting photocatalysts over large areas are necessary as is the ability to recover hydrogen safely and efficiently from the produced oxyhydrogen gas. This lead article describes the key discoveries and recent research trends in photosynthesis using particulate semiconductors and photocatalyst sheets for overall water splitting via one-step excitation and two-step excitation (Z-scheme reactions) as well as for direct conversion of carbon dioxide into renewable fuels using water as an electron donor. We describe the latest advances in solar watersplitting and carbon dioxide reduction systems and pathways to improve their future performance together with challenges and solutions in their practical application and scalability including the fixation of particulate photocatalysts hydrogen recovery safety design of reactor systems and approaches to separately generate hydrogen and oxygen from water.

This study engineered seabed sediment with microwave-assisted Ni2+ -substitution to enhance its composition and properties. The catalytic activity of microwave-assisted Ni2+ - substituted seabed sediment (Mwx%Ni-SB) was investigated in the two-stage pyrolysis of plastic waste for hydrogen production. The characterization reveals microwave irradiation synergistically modifies the physical properties (increasing functional groups reducing crystallinity) and electronic properties (modulating bandgap energy increasing electron density) of the Mwx%Ni-SB thereby improving methane reforming performance. Microwave treatment compresses and rearranges Ni2+ ions within the sediment lattice resulting in increased order and density and creating defects that enhance catalytic activity. GC-TCD analysis demonstrates that the use of catalysts in the first and second stages more than doubled hydrogen production (109.74%) compared to not using catalysts. Therefore increased Ni2+ substitution significantly reduced methane production by 49.04% while simultaneously boosting hydrogen production by 23.00%.

Microbial electrolysis cells (MECs) have garnered significant attention as a promising solution for industrial wastewater treatment enabling the simultaneous degradation of organic compounds and biohydrogen production. Developing efficient and cost-effective cathodes to drive the hydrogen evolution reaction is central to the success of MECs as a sustainable technology. While numerous lab-scale experiments have been conducted to investigate different cathode materials the transition to pilot-scale applications remains limited leaving the actual performance of these scaled-up cathodes largely unknown. In this study nickel-foam and stainless-steel wool cathodes were employed as catalysts to critically assess hydrogen production in a 150 L MEC pilot plant treating sugar-based industrial wastewater. Continuous hydrogen production was achieved in the reactor for more than 80 days with a maximum COD removal efficiency of 40 %. Nickel-foam cathodes significantly enhanced hydrogen production and energy efficiency at non-limiting substrate concentration yielding the maximum hydrogen production ever reported at pilot-scale (19.07 ± 0.46 L H2 m− 2 d− 1 and 0.21 ± 0.01 m3 m− 3 d− 1 ). This is a 3.0-fold improve in hydrogen production compared to the previous stainless-steel wool cathode. On the other hand the higher price of Ni-foam compared to stainless-steel should also be considered which may constrain its use in real applications. By carefully analysing the energy balance of the system this study demonstrates that MECs have the potential to be net energy producers in addition to effectively oxidize organic matter in wastewater. While higher applied potentials led to increased energy requirements they also resulted in enhanced hydrogen production. For our system a conservative applied potential range from 0.9 to 1.0 V was found to be optimal. Finally the microbial community established on the anode was found to be a syntrophic consortium of exoelectrogenic and fermentative bacteria predominantly Geobacter and Bacteroides which appeared to be well-suited to transform complex organic matter into hydrogen.

Excessive reliance on traditional energy sources such as coal petroleum and gas leads to a decrease in natural resources and contributes to global warming. Consequently the adoption of renewable energy sources in power systems is experiencing swift expansion worldwide especially in offshore areas. Floating solar photovoltaic (FPV) technology is gaining recognition as an innovative renewable energy option presenting benefits like minimized land requirements improved cooling effects and possible collaborations with hydropower. This study aims to assess the levelized cost of electricity (LCOE) associated with floating solar initiatives in offshore and onshore environments. Furthermore the LCOE is assessed for initiatives that utilize floating solar PV modules within aquaculture farms as well as for the integration of various renewable energy sources including wind wave and hydropower. The LCOE for FPV technology exhibits considerable variation ranging from 28.47 EUR/MWh to 1737 EUR/MWh depending on the technologies utilized within the farm as well as its geographical setting. The implementation of FPV technology in aquaculture farms revealed a notable increase in the LCOE ranging from 138.74 EUR/MWh to 2306 EUR/MWh. Implementation involving additional renewable energy sources results in a reduction in the LCOE ranging from 3.6 EUR/MWh to 315.33 EUR/MWh. The integration of floating photovoltaic (FPV) systems into green hydrogen production represents an emerging direction that is relatively little explored but has high potential in reducing costs. The conversion of this energy into hydrogen involves high final costs with the LCOH ranging from 1.06 EUR/kg to over 26.79 EUR/kg depending on the complexity of the system.

This study presents a scientometric analysis of renewable energy applications in low-temperature regions focusing on green hydrogen production carbon storage and emerging trends. Using bibliometric tools such as RStudio and VOSviewer the research evaluates publication trends from 1988 to 2024 revealing an exponential growth in renewable energy studies post-2021 driven by global policies promoting carbon neutrality. Life cycle assessment (LCA) plays a crucial role in evaluating the environmental impact of energy systems underscoring the need to integrate renewable sources for emission reduction. Hydrogen production via electrolysis has emerged as a key solution in decarbonizing hardto-abate sectors while carbon storage technologies such as bioenergy with carbon capture and storage (BECCS) are gaining traction. Government policies including carbon taxes fossil fuel phase-out strategies and renewable energy subsidies significantly shape the energy transition in cold regions by incentivizing low-carbon alternatives. Multi-objective optimization techniques leveraging artificial intelligence (AI) and machine learning are expected to enhance decision-making processes optimizing energy efficiency reliability and economic feasibility in renewable energy systems. Future research must address three critical challenges: (1) strengthening policy frameworks and financial incentives for largescale renewable energy deployment (2) advancing energy storage hydrogen production and hybrid energy systems and (3) integrating multi-objective optimization approaches to enhance cost-effectiveness and resilience in extreme climates. It is expected that the research will contribute to the field of knowledge regarding renewable energy applications in low-temperature regions.

In the introduction to this article a brief overview of the generated energy and the power produced by the photovoltaic systems with a peak power of 3 MWp and different tilt and orientation of the photovoltaic panels is given. The characteristics of the latest systems generating energy by wind turbines with a capacity of 3.45 MW are also presented. In the subsequent stages of the research the necessity of balancing the energy in power networks powered by a mix of renewable energy sources is demonstrated. Then a calculation algorithm is presented in the area of balancing the energy system powered by a photovoltaic–wind energy mix and feeding the low-emission hydrogen production process. It is analytically and graphically demonstrated that the process of balancing the entire system can be influenced by structural changes in the installation of the photovoltaic panels. It is proven that the tilt angle and orientation of the panels have a significant impact on the level of power generated by the photovoltaic system and thus on the energy mix in individual hourly intervals. Research has demonstrated that the implementation of planned design changes in the assembly of panels in a photovoltaic system allows for a reduction in the size of the energy storage system by more than 2 MWh. The authors apply actual measurement data from a specific geographical context i.e. from the Lublin region in Poland. The calculations use both traditional statistical methods and probabilistic analysis. Balancing the generated power and the energy produced for the entire month considered in hourly intervals throughout the day is the essence of the calculations made by the authors.

A pivotal ambition to aid global decarbonisation efforts is green electrolytic hydrogen produced with renewable energy. Prolonged operation of water electrolysers induces cell degradation decreasing production efficiency and gas yield over the lifespan of the electrolyser stack. Considerations for degradation modelling is seen to a varying extent in previous literature. This work shows the effects of including degradation modelling within existing system scenarios and new ones to demonstrate the impact of inclusion on key techno-economic parameters. A fundamental Anion Exchange Membrane electrolyser model is constructed validated and utilised into a broader hydrogen and oxygen co-production system powered by solar-PV. A second scenario tests the compatibility of the no-degradation trend with reference material and then investigates the effects of including degradation modelling showing only a 1.47% increase in levelised cost of hydrogen (LCOH). Subsequent scenarios include determining that byproduct oxygen utilisation becomes beneficial for a scenario with rated electrolyser power of above 35 MW and the observations related to stack replacement strategies are discussed. Under hypothetically higher degradation rates detriment to gas yield and LCOH is around 5% for average operational degradation rates of 15–20 μV/hr and around 10% for 30–40 μV/hr compared to around 2% for the model baseline average rate of 5.23–5.26 μV/hr.

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.

The biological production of hydrogen offers a renewable and potentially sustainable alternative for clean energy generation. In Northeast Brazil depleted oil reservoirs (DORs) present a unique opportunity to integrate biotechnology with existing fossil fuel infrastructure. These subsurface formations rich in residual hydrocarbons (RH) and native H2 producing microbiota can be repurposed as bioreactors for hydrogen production. This process often referred to as “Gold Hydrogen” involves the in situ microbial conversion of RH into H2 typically via dark fermentation and is distinct from green blue or grey hydrogen due to its reliance on indigenous subsurface biota and RH. Strategies include nutrient modulation and chemical additives to stimulate native hydrogenogenic genera (Clostridium Petrotoga Thermotoga) or the injection of improved inocula. While this approach has potential environmental benefits such as integrated CO2 sequestration and minimized surface disturbance it also presents risks namely the production of CO2 and H2S and fracturing which require strict monitoring and mitigation. Although infrastructure reuse reduces capital expenditures achieving economic viability depends on overcoming significant technical operational and biotechnological challenges. If widely applied this model could help decarbonize the energy sector repurpose legacy infrastructure and support the global transition toward low-carbon technologies.

This review article provides a comprehensive overview of the pivotal role that nanomaterials particularly graphene and its derivatives play in advancing hydrogen energy technologies with a focus on storage production and transport. As the quest for sustainable energy solutions intensifies the use of nanoscale materials to store hydrogen in solid form emerges as a promising strategy toward mitigate challenges related to traditional storage methods. We begin by summarizing standard methods for producing modified graphene derivatives at the nanoscale and their impact on structural characteristics and properties. The article highlights recent advancements in hydrogen storage capacities achieved through innovative nanocomposite architectures for example multi-level porous graphene structures containing embedded nickel particles at nanoscale dimensions. The discussion covers the distinctive characteristics of these nanomaterials particularly their expansive surface area and the hydrogen spillover effect which enhance their effectiveness in energy storage applications including supercapacitors and batteries. In addition to storage capabilities this review explores the role of nanomaterials as efficient catalysts in the hydrogen evolution reaction (HER) emphasizing the potential of metal oxides and other composites to boost hydrogen production. The integration of nanomaterials in hydrogen transport systems is also examined showcasing innovations that enhance safety and efficiency. As we move toward a hydrogen economy the review underscores the urgent need for continued research aimed at optimizing existing materials and developing novel nanostructured systems. Addressing the primary challenges and potential future directions this article aims to serve as a roadmap to enable scientists and industry experts to maximize the capabilities of nanomaterials for transforming hydrogen-based energy systems thus contributing significantly to global sustainability efforts.

Due to concerns regarding fossil greenhouse gas emissions biogenic material such as forest residues is viewed nowadays as a valuable source of carbon atoms to produce syngas that can be used to synthesise biofuels such as methanol. A great challenge in using gasified biomass for methanol production is the large excess of carbon in the syngas as compared to the H2 content. The water–gas shift (WGS) reaction is often used to add H2 and balance the syngas. CO2 is also produced by this reaction. Some of the CO2 has to be removed from the gaseous mixture thus decreasing the process carbon yield and maintaining CO2 emissions. The WGS reaction also decreases the overall process heat output. This paper demonstrates the usefulness of using an extra source of renewable H2 from steam electrolysis instead of relying on the WGS reaction for a much higher performance of syngas production from gasification of wood in a simple system with a fixed-bed gasifier. A commercial process simulation software is employed to predict that this approach will be more efficient (overall energy efficiency of about 67%) and productive (carbon conversion yield of about 75%) than relying on the WGS reaction. The outlook for this process that includes the use of the solid oxide electrolyser technology appears to be very promising because the electrolyser has the dual function of providing all of the supplemental H2 required for syngas balancing and all the O2 required for the production of a suitable hot raw syngas. This process is conducive to biomethanol production in dispersed small plants using local biomass for end-users from the same geographical area thus contributing to regional sustainability.

Renewable energy-based water electrolysis for hydrogen production is an effective pathway to achieve green energy transition. However the intermittency and randomness of renewable energy pose numerous challenges to the safe and stable operation of hydrogen production systems with the wide power fluctuation adaptability and economic efficiency of electrolyzers being prominent issues. Hybrid electrolyzers combine the operational characteristics of proton exchange membrane (PEM) and alkaline electrolyzers leveraging the advantages of both to improve adaptability to wide power fluctuations and economic efficiency thereby enhancing the overall system efficiency. To ensure coordinated operation of hybrid electrolyzers it is essential to consider their startstop characteristics and the impact of hydrogen to oxygen (HTO) concentration on the hydrogen production system. To achieve this we first discuss the operating characteristics of both types of electrolyzers and the in fluence of system parameters on HTO concentration. A control scheme for hybrid electrolyzer systems consid ering HTO content is proposed. By analyzing the electrolyzer efficiency curve the optimal efficiency point under low power operation is identified enabling the electrolyzers to operate at this optimal efficiency thus enhancing the efficiency of the hybrid electrolyzer system. The implementation of a dual-layer rotation control strategy effectively balances the lifecycle loss of the electrolyzers. Additionally reducing the pressure during startup broadens the startup range of the hybrid electrolyzer.

The integration of water electrolyzers and photovoltaic (PV) solar technology is a potential development in renewable energy systems offering new avenues for sustainable energy generation and storage. This coupling consists of using PV-generated electricity to power water electrolysis breaking down water molecules into hydrogen and oxygen. While oxygen is a useful byproduct the created hydrogen is used as a clean storable energy carrier or feedstock for numerous businesses. It is possible to operate the device with or without battery storage. When solar energy is combined with batteries excess solar energy may be stored for later use maximizing energy efficiency and guaranteeing a steady supply of electricity even in the absence of direct sunlight. On the other hand battery-free systems depend on the electrolyzer’s continuous power generation to convert solar energy into hydrogen during the day. In addition to allowing for the production of renewable hydrogenthis hybrid PV-solar and water electrolyzer setup contributes to grid stability by offering demand-side flexibility. Moreover the modularity of these systems enables scalability to meet diverse energy requirements spanning from residential to industrial applications thereby fostering a cleaner and more sustainable energy landscape. This review delves into various topologies for PV-driven electrolysis and conducts a thorough exploration of the dynamics of low-temperature water electrolyzers. Specifically it examines their integration with three primary technologies: Proton Exchange Membrane Alkaline and Anion Exchange Membrane shedding light on their implications for the broader integration landscape. Through detailed analysis and insights this study enriches the understanding of the potential and challenges inherent in the convergence of PV solar water electrolysis and renewable energy systems.

The commercialization of hydrogen as a fuel faces severe technological economic and environmental challenges. As a method to overcome these challenges microalgal biohydrogen production has become the subject of growing research interest. Microalgal biohydrogen can be produced through different metabolic routes the economic considerations of which are largely missing from recent reviews. Thus this review briefly explains the techniques and economics associated with enhancing microalgae-based biohydrogen production. The cost of producing biohydrogen has been estimated to be between $10 GJ-1 and $20 GJ−1 which is not competitive with gasoline ($0.33 GJ−1 ). Even though direct biophotolysis has a sunlight conversion efficiency of over 80% its productivity is sensitive to oxygen and sunlight availability. While the electrochemical processes produce the highest biohydrogen (>90%) fermentation and photobiological processes are more environmentally sustainable. Studies have revealed that the cost of producing biohydrogen is quite high ranging between $2.13 kg−1 and 7.24 kg−1 via direct biophotolysis $1.42kg−1 through indirect biophotolysis and between $7.54 kg−1 and 7.61 kg−1 via fermentation. Therefore low-cost hydrogen production technologies need to be developed to ensure long-term sustainability which requires the optimization of critical experimental parameters microalgal metabolic engineering and genetic modification.

Meeting climate targets requires profound transformations in the energy system. Most energy uses should be electrified but where this is not feasible hydrogen can be part of the solution. However 98% of global hydrogen production involves greenhouse gas emissions with an average of 12 kg CO2e/kg H2. Therefore new hydrogen production pathways are needed in order to make hydrogen production compatible with climate targets. In this work we fill this gap by systematically comparing the energy and emissions intensity of 173 hydrogen production pathways suitable for the UK. Scenarios include onshore and offshore pathways and the use of repurposed infrastructure. Unlike fossil-fuel based pathways the results show that electrolytic hydrogen powered by fixed offshore wind could align with proposed emissions standards either onshore or offshore. However the embodied and fugitive emissions are important to consider for electrolytic pathways as they result in 10–50% of the total emissions intensity.

Seawater electrolysis represents a promising green energy technology with significant potential for efficient energy conversion. This study provides an in-depth examination of the key scientific challenges inherent in the seawater-electrolysis process and their potential solutions. Initially it analyzes the potential issues of precipitation and aggregation at the cathode during hydrogen evolution proposing strategies such as self-cleaning cathodes and precipitate removal to ensure cathode stability in seawater electrolysis. Subsequently it addresses the corrosion challenges faced by anode catalysts in seawater introducing several anti-corrosion strategies to enhance anode stability including substrate treatments such as sulfidation phosphidation selenidation and LDH (layered double hydroxide) anion intercalation. Additionally this study explores the role of regulating the electrode surface microenvironment and forming unique coordination environments for active atoms to enhance seawater electrolysis performance. Regulating the surface microenvironment provides a novel approach to mitigating seawater corrosion. Contrary to the traditional understanding that chloride ions accelerate anode corrosion certain catalysts benefit from the unique coordination environment of chloride ions on the catalyst surface potentially enhancing oxygen evolution reaction (OER) performance. Lastly this study presents the latest advancements in the industrialization of seawater electrolysis including the in situ electrolysis of undiluted seawater and the implementation of three-chamber dual anion membranes coupled with circulating electrolyte systems. The prospects of seawater electrolysis are also explored.

While fossil fuels continue to be used and to increase air pollution across the world hydrogen gas has been proposed as an alternative energy source and a carrier for the future by scientists. Water electrolysis is a renewable and sustainable chemical energy production method among other hydrogen production methods. Hydrogen production via water electrolysis is a popular and expensive method that meets the high energy requirements of most industrial electrolyzers. Scientists are investigating how to reduce the price of water electrolytes with different methods and materials. The electrolysis structure equations and thermodynamics are first explored in this paper. Water electrolysis systems are mainly classified as high- and low-temperature electrolysis systems. Alkaline PEM-type and solid oxide electrolyzers are well known today. These electrolyzer materials for electrode types electrolyte solutions and membrane systems are investigated in this research. This research aims to shed light on the water electrolysis process and materials developments.

Hydrogen is a versatile energy vector for a plethora of applications; nevertheless its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper recent developments in R&D on waste gasification (municipal solid waste tires plastic waste) are summarised and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock ranging from 15 to 300 g H2/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However regulations like frame conditions or subsidies are necessary to bring the technology into the market.