Production & Supply Chain

An exemplary techno-economic and environmental assessment of carbon-negative hydrogen (H2) production is carried out in this work. It is based on the so-called “dark photosynthesis” with carbon dioxide (CO2) capture and geological storage. As a special feature of the assessment the economic consequences due to the impact on the global climate are taken into account. The results indicate that the example project would be capable of generating negative GHG emissions under the assumptions made. The amount is estimated to be 17.72 kgCO2 to be removed from the atmosphere per kilogram of H2 produced. The levelized costs of carbon-negative hydrogen are obtained considering the economic impact of greenhouse gas emissions and removals. They are estimated to be 0.013 EUR/kWhH2. Compared to grey hydrogen from natural gas (0.12 EUR/kWhH2) and green hydrogen from electrolysis using renewable electricity (0.18 EUR/kWhH2) this shows a potential environmental-economic advantage of the considered example. Even without internalization of GHG impacts an economic advantage of the project (0.12 EUR/kWhH2) over green hydrogen (0.17 EUR/kWhH2) is indicated. Compared to other NETs the GHG removal efficiency is at the lower end of both BECCS and DACCS approaches.

As the commercialisation of two contrasting solar-powered water splitting devices with lower TRLs of proton exchange membrane (PEM) electrolyser systems and photoelectrochemical (PEC) systems gains momentum the path towards a sustainable H2 economy is taking shape. Ongoing pilot projects and demonstration plants are proving the feasibility and potential of these technologies in real-world applications. However to ensure their success we must confront the critical challenges of cost reduction and efficiency enhancement making green H2 economically competitive with traditional production methods. To achieve this a collaborative effort among academia industry and policymakers is paramount. This comprehensive review begins by examining traditional water electrolysis methods focusing on the production of green H2 through electrochemical splitting. It delves into crucial components and advancements in the PEM systems addressing challenges related to catalysts membranes gas diffusion layers and bipolar plates. The review also explores solar-driven PEC water splitting emphasizing the significance of efficient photoelectrodes and reactor design. Additionally it discusses the integration of photovoltaic cells with electrochemical or PEC systems for higher H2 yield. Commercialisation is underway and this endeavour necessitates a collaborative approach with active involvement from academia industry and policymakers. This collective effort not only propels us towards greener and more sustainable energy solutions but also represents a transformative step in the global journey towards a sustainable and environmentally conscious economy.

Hydrogen produced from electrolysis is an attractive carbon-free fuel and feedstock but potential benefits depend on the carbon intensity of electricity production. This study uses technoeconomic modeling to analyze the benefits of producing zero-carbon hydrogen through dynamically operated polymer electrolyte membrane electrolyzers connected to photovoltaic and wind variable renewable energy (VRE) sources. Dynamic operation is considered for current densities between 0 and 6 A cm2 and compared to a constant current density of 2 A cm2 for different combinations of VRE to electrolysis (VRE:E) capacity ratios and compositions of photovoltaic and wind energy in four locations across the United States. For optimal VRE:E and wind:photovoltaic capacity ratios dynamic operation is found to reduce the levelized cost of hydrogen by 5%–9% while increasing hydrogen production by 134%–173% and decreasing excess electrical power by 82%–95%. The framework herein may be used to determine the optimal VRE:E capacity and VRE mix for dynamically operated green hydrogen systems.

Hydrogen has received substantial attention because of its diverse application in the energy sector. Steam methane reforming (SMR) dominates the current hydrogen production and is the least expensive endothermic reaction to produce grey hydrogen. This technology provides the advantages of low cost and high energy efficiency; however it emits an enormous amount of CO2. Carbon capture storage (CCS) technology helps reduce these emissions by 47% to 53% producing blue hydrogen. Methane pyrolysis is an alternative to SMR that produces (ideally) CO2-free turquoise hydrogen. In practice methane pyrolysis reduces CO2 emissions by 71% compared to grey hydrogen and 46% compared to blue hydrogen. While carbon dioxide emissions decrease with CCS fugitive methane emissions (FMEs) for blue and turquoise hydrogen are higher than those for grey hydrogen because of the increased use of natural gas to power carbon capture. We undertake FMEs of 3.6% of natural gas consumption for individual processes. In this study we also explore the utilization of biogas as a feedstock and additional Boudouard reactions for efficient utilization of solid carbon from methane pyrolysis and carbon dioxide from biogas. The present study focuses on possible ways to reduce overall emissions from turquoise hydrogen to provide solutions for a sustainable low-CO2 energy source.

Hydrogen is an attractive clean sustainable energy source primarily produced via industry. At present most reviews on hydrogen mainly focus on the preparation and storage of hydrogen while the development and utilization of natural hydrogen will greatly reduce its cost. Natural hydrogen has been discovered in many geological environments. Therefore based on extensive literature research in this study the distribution and sources of natural hydrogen were systematically sorted and the identification method and occurrence state of natural hydrogen were examined and summarized. The results of this research show that hydrogen has been discovered in oceanic spreading centers transform faults passive margins convergent margins and intraplate settings. The primary sources of the hydrogen include alterations in Fe(II)-containing rocks the radiolysis of water degassed magma and the reaction of water- and silica-containing rocks during the mechanical fracturing. Hydrogen can appear in free gas it can be adsorbed and trapped in inclusions. Currently natural hydrogen exploration is in its infancy. This systematic review helps to understand the origin distribution and occurrence pattern of natural hydrogen. In addition it facilitates the exploration and development of natural hydrogen deposits thus enabling the production of low-cost hydrogen.

The Brazilian energy grid is considered as one of the cleanest in the world because it is composed of more than 80% of renewable energy sources. This work aimed to apply the levelized costs (LCOH) and environmental cost accounting techniques to demonstrate the feasibility of producing hydrogen (H2 ) by alkaline electrolysis powered by the Brazilian energy grid. A project of hydrogen production with a lifetime of 20 years had been evaluated by economical and sensitivity analysis. The production capacity (8.89 to 46.67 kg H2/h) production volume (25 to 100%) hydrogen sale price (1 to 5 USD/kg H2 ) and the MAR rate were varied. Results showed that at 2 USD/kg H2 all H2 production plant sizes are economically viable. On this condition a payback of fewer than 4 years an IRR greater than 31 a break-even point between 56 and 68% of the production volume and a ROI above 400% were found. The sensitivity analysis showed that the best economic condition was found at 35.56 kg H2/h of the plant size which generated a net present value of USD 10.4 million. The cost of hydrogen varied between 1.26 and 1.64 USD/kg and a LCOH of 37.76 to 48.71 USD/MWh. LCA analysis showed that the hydrogen production project mitigated from 26 to 131 thousand tons of CO2 under the conditions studied.

In the sustainability context the performance of energy-producing technologies using different energy sources needs to be scored and compared. The selective criterion of a higher level of useful energy to feed an ever-increasing demand of energy to satisfy a wide range of endo- and exosomatic human needs seems adequate. In fact surplus energy is able to cover energy services only after compensating for the energy expenses incurred to build and to run the technology itself. This paper proposes an energy sustainability analysis (ESA) methodology based on the internal and external energy use of a given technology considering the entire energy trajectory from energy sources to useful energy. ESA analysis is conducted at two levels: (i) short-term by the use of the energy sustainability index (ESI) which is the first step to establish whether the energy produced is able to cover the direct energy expenses needed to run the technology and (ii) long-term by which all the indirect energy-quotas are considered i.e. all the additional energy requirements of the technology including the energy amortization quota necessary for the replacement of the technology at the end of its operative life. The long-term level of analysis is conducted by the evaluation of two indicators: the energy return per unit of energy invested (EROI) over the operative life and the energy payback-time (EPT) as the minimum lapse at which all energy expenditures for the production of materials and their construction can be repaid to society. The ESA methodology has been applied to the case study of H2 production at small-scale (10–15 kWH2) comparing three different technologies: (i) steam-methane reforming (SMR) (ii) solar-powered water electrolysis (SPWE) and (iii) two-stage anaerobic digestion (TSAD) in order to score the technologies from an energy sustainability perspective.

The aim of this study is to investigate the technical and economic potential of electricity and hydrogen production in Casablanca Morocco. For this reason we simulated the performance of a 4.2 MWp wind turbine if installed in Casablanca. The results show that the electricity and hydrogen production varies greatly through the year due to the high fluctuation in wind speed. The annual electricity and hydrogen production is 29.16 GWh and 555 Tons respectively. As for the levelized cost of production the LCOE was found to be 0.24 $/kWh and the H2 LCO were equal to 13.52 $/Kg.

Alkaline electrolyzers are the most widespread technology due to their maturity low cost and large capacity in generating hydrogen. However compared to proton exchange membrane (PEM) electrolyzers they request the use of potassium hydroxide (KOH) or sodium hydroxide (NaOH) since the electrolyte relies on a liquid solution. For this reason the performances of alkaline electrolyzers are governed by the electrolyte concentration and operating temperature. Due to the growing development of the water electrolysis process based on alkaline electrolyzers to generate green hydrogen from renewable energy sources the main purpose of this paper is to carry out a comprehensive survey on alkaline electrolyzers and more specifically about their electrical domain and specific electrolytic conductivity. Besides this survey will allow emphasizing the remaining key issues from the modeling point of view.

This study presents an enhancement to the Switch optimization model for hydrogen energy planning by integrating the capability to consider the construction and operation of hydrogen electrolysis plants and the operation of water distribution systems. This integration was achieved through the addition of two new modules and their effectiveness is demonstrated through their application in a case study for Durham region. The study highlights the significance of incorporating water distribution systems into energy planning demonstrating how optimal locations for hydrogen plants can significantly influence water and power demand as well as alter the total operating costs. The enhanced Switch model showcases its improved capability to assist policymakers and stakeholders in transitioning towards a sustainable energy future.

Water electrolysis is the most promising method for efficient production of high purity hydrogen (and oxygen) while the required power input for the electrolysis process can be provided by renewable sources (e.g. solar or wind). The thus produced hydrogen can be used either directly as a fuel or as a reducing agent in chemical processes such as in Fischer–Tropsch synthesis. Water splitting can be realized both at low temperatures (typically below 100 °C) and at high temperatures (steam water electrolysis at 500– 1000 °C) while different ionic agents can be electrochemically transferred during the electrolysis process (OH− H+ O2− ). Singular requirements apply in each of the electrolysis technologies (alkaline polymer electrolyte membrane and solid oxide electrolysis) for ensuring high electrocatalytic activity and long-term stability. The aim of the present article is to provide a brief overview on the effect of the nature and structure of the catalyst–electrode materials on the electrolyzer’s performance. Past findings and recent progress in the development of efficient anode and cathode materials appropriate for large-scale water electrolysis are presented. The current trends limitations and perspectives for future developments are summarized for the diverse electrolysis technologies of water splitting while the case of CO2/H2O co-electrolysis (for synthesis gas production) is also discussed.

The necessity of energy solutions that are economically viable ecologically sustainable and environmentally friendly has become fundamental to economic and societal advancement of nations. In this context renewable energy sources emerge as the most vital component. Furthermore hydrogen generation systems based on renewable energies are increasingly recognized as the most crucial strategies to mitigate global warming. In the present study a comparative analysis is conducted from an exergy-economic perspective to find the most efficient configuration among three different systems for renewable-based power to hydrogen production. These renewable sources are wind turbine salinity gradient solar pond (SGSP) and ocean thermal energy conversion (OTEC). SGSP and OTEC are coupled with a hydrogen production unit by a trilateral cycle (TLC) to improve the temperature match of the heating process. The heat waste energy within these systems is recovered by a thermoelectric generator (TEG) and a proton exchange membrane electrolyzer (PEME) is used for hydrogen production. Under base case input conditions the net power input of PEME is estimated to be approximately 327.8 kW across all configurations. Additionally the 3E (energy exergy and exergy-economic) performance of the three systems is evaluated by a parametric study and design optimization. The results of the best performance analysis reveal that the best exergy efficiency is achievable with the wind-based system in the range of 5.8–10.47% and for average wind speed of 8–12 m/s. Correspondingly the most favorable total cost rate is attributed to the wind-based system at a wind speed of 8 m/s equating to 66.08 USD/h. Subsequently the unit cost of hydrogen for the SGSP-based system is estimated to be the most economical ranging from 42.78 to 44.31 USD/GJ.

Environmental concerns regarding greenhouse gases have spurred research into alternative energy sources. One of the most prevalent waste products in the beverage industry is spent coffee grains (SCG) an estimated 60 million tons globally each year. These quantities justify the need to find effective ways to recycle this waste through the adoption of closed-loop circular economies (CE) and sustainable biofuel strategies. One promising approach is the conversion of SCG into biofuels particularly biohydrogen and biomethane through biological processes. However prior to commercialization it is critical to validate its potential profitability via technical and economic analyses such as techno-economic assessment (TEA). To this end in this study the profitability of two scenarios for biohydrogen and biomethane production has been assessed to explore feasible processing routes for SCG valorization. First a two-step dark fermentation and anaerobic digestion (DF-AD) process and second a two-step dark fermentation and photo fermentation (DF-PF) process. The profitability and sensitivity analysis results clarified that Scenario I should be chosen over Scenario II due to its higher net present value (NPV) of 138 million $ internal rate of return (IRR) of 15.3 % gross margin (GM) of 56.9 % return on investment (ROI) of 12.7 % and shorter payback period (PBP) of 6.2 years.

This study describes the optimization of a modelling process concerning biogas’ use to generate green hydrogen and electrical power. The Aspen Plus simulation tool is used to model the procedure and the approach employed to limit the emissions of gas from the hydrogen production process will be the CO2 capture method. This technique uses slack lime (Ca(OH)2) to absorb CO2 capture since it is readily available. The study analyzes many critical parameters in the process including the temperature and pressure in the steam reforming (SR) and the water gas shift (WGS) reactions along with the steam to carbon ratio (S/C) to determine how the production of green hydrogen and electrical power will be influenced. Electricity generation is achieved by taking the residual water from the SR WGS carbonation reactions and converting it to the vapour phase allowing the steam to pass through the turbine to generate electricity. To examine the effects of the synchronized critical parameters response surface methodology (RSM) was used thus allowing the optimal operational conditions to be determined in the form of an optimized zone for operation. The result of parameter optimization gave the maximum green hydrogen production of 211.46 kmol/hr and electric power production of 2311.68 kWh representing increases of 34.86% and 5.62% respectively when using 100 kmol/hr of biogas. In addition control structures were also built to control the reactors’ temperature in the dynamic section. The tuning parameters can control the SR and WGS system’s reactor to maintain the system in approximately 0.29 h and 0.32 h respectively.

The valorization of integrated steelworks process off-gases as feedstock for synthesizing methane and methanol is in line with European Green Deal challenges. However this target can be generally achieved only through process off-gases enrichment with hydrogen and use of cutting-edge syntheses reactors coupled to advanced control systems. These aspects are addressed in the RFCS project i3 upgrade and the central role of hydrogen was evident from the first stages of the project. First stationary scenario analyses showed that the required hydrogen amount is significant and existing renewable hydrogen production technologies are not ready to satisfy the demand in an economic perspective. The poor availability of low-cost green hydrogen as one of the main barriers for producing methane and methanol from process off-gases is further highlighted in the application of an ad-hoc developed dispatch controller for managing hydrogen intensified syntheses in integrated steelworks. The dispatch controller considers both economic and environmental impacts in the cost function and although significant environmental benefits are obtainable by exploiting process off-gases in the syntheses the current hydrogen costs highly affect the dispatch controller decisions. This underlines the need for big scale green hydrogen production processes and dedicated green markets for hydrogen-intensive industries which would ensure easy access to this fundamental gas paving the way for a C-lean and more sustainable steel production.

Green hydrogen is considered to be one of the best candidates for fossil fuels in the near future. Bio-hydrogen production from the dark fermentation of organic materials including organic wastes is one of the most cost-effective and promising methods for hydrogen production. One of the main challenges posed by this method is the low production rate. Therefore optimizing the operating parameters such as the initial pH value operating temperature N/C ratio and organic concentration (xylose) plays a significant role in determining the hydrogen production rate. The experimental optimization of such parameters is complex expensive and lengthy. The present research used an experimental data asset adaptive network fuzzy inference system (ANFIS) modeling and particle swarm optimization to model and optimize hydrogen production. The coupling between ANFIS and PSO demonstrated a robust effect which was evident through the improvement in the hydrogen production based on the four input parameters. The results were compared with the experimental and RSM optimization models. The proposed method demonstrated an increase in the biohydrogen production of 100 mL/L compared to the experimental results and a 200 mL/L increase compared to the results obtained using ANOVA.

Within integrated steelmaking industries significant research efforts are devoted to the efficient use of resources and the reduction of CO2 emissions. Integrated steelworks consume a considerable quantity of raw materials and produce a high amount of by-products such as off-gases currently used for the internal production of heat steam or electricity. These off-gases can be further valorized as feedstock for methane and methanol syntheses but their hydrogen content is often inadequate to reach high conversions in synthesis processes. The addition of hydrogen is fundamental and a suitable hydrogen production process must be selected to obtain advantages in process economy and sustainability. This paper presents a comparative analysis of different hydrogen production processes from renewable energy namely polymer electrolyte membrane electrolysis solid oxide electrolyze cell electrolysis and biomass gasification. Aspen Plus® V11-based models were developed and simulations were conducted for sensitivity analyses to acquire useful information related to the process behavior. Advantages and disadvantages for each considered process were highlighted. In addition the integration of the analyzed hydrogen production methods with methane and methanol syntheses is analyzed through further Aspen Plus®-based simulations. The pros and cons of the different hydrogen production options coupled with methane and methanol syntheses included in steelmaking industries are analyzed

The depletion of fossil fuel reserves has resulted from their application in the industrial and energy sectors. As a result substantial efforts have been dedicated to fostering the shift from fossil fuels to renewable energy sources via technological advancements in industrial processes. Microalgae can be used to produce biofuels such as biodiesel hydrogen and bioethanol. Microalgae are particularly suitable for hydrogen production due to their rapid growth rate ability to thrive in diverse habitats ability to resolve conflicts between fuel and food pro duction and capacity to capture and utilize atmospheric carbon dioxide. Therefore microalgae-based bio hydrogen production has attracted significant attention as a clean and sustainable fuel to achieve carbon neutrality and sustainability in nature. To this end the review paper emphasizes recent information related to microalgae-based biohydrogen production mechanisms of sustainable hydrogen production factors affecting biohydrogen production by microalgae bioreactor design and hydrogen production advanced strategies to improve efficiency of biohydrogen production by microalgae along with bottlenecks and perspectives to over come the challenges. This review aims to collate advances and new knowledge emerged in recent years for microalgae-based biohydrogen production and promote the adoption of biohydrogen as an alternative to con ventional hydrocarbon biofuels thereby expediting the carbon neutrality target that is most advantageous to the environment.

Apart from many limitations the usage of hydrogen in different day-to-day applications have been increasing drastically in recent years. However numerous techniques available to produce hydrogen electrolysis of water is one of the simplest and cost-effective hydrogen production techniques. In this method water is split into hydrogen and oxygen by using external electric current. In this research a novel hydrogen production system incorporated with Photovoltaic – Thermal (PVT) solar collector is developed. The influence of different parameters like solar collector tilt angle thermal collector design and type of heat transfer fluid on the performance of PVT system and hydrogen production system are also discussed. Finally thermal efficiency electrical efficiency and hydrogen production rate have been predicted by using the Adaptive Neuro-Fuzzy Inference System (ANFIS) technique. Based on this study results it can be inferred that the solar collector tilt angle plays a significant role to improve the performance of the electrical and thermal performance of PVT solar system and Hydrogen yield rate. On the other side the spiral-shaped thermal collector with water exhibited better end result than the other hydrogen production systems. The predicted results ANFIS techniques represent an excellent agreement with the experimental results. In consequence it is suggested that the developed ANFIS model can be adopted for further studies to predict the performance of the hydrogen production system.

This study assesses the competitiveness of producing green hydrogen (H2) in Saudi Arabia and Germany using a power-to-carrier (P2X) model in PLEXOS for 2030 and beyond. The target amount of H2 to be produced serves as the only exogenous input allowing the model which runs on an hourly temporal resolution to endogenously optimize the electrolyzer technology (alkaline proton exchange membrane or solid oxide electrolyzer cell) the capacity of the electrolyzer to be built and the optimal carbon-free energy mix. Results suggest the overall investment needs in Saudi Arabia are approximately 25% lower than those for wind-based hydrogen production in Germany with the best-case scenario to produce 0.213 Mt of green H2 costing a net present value of $6.20 billion in Saudi Arabia compared to $8.11 billion in Germany. The findings indicate that alkaline electrolyzers dominate the production process favored for their low cost despite the higher efficiencies of other electrolyzer types. Moreover the model opts to dump excess energy rather than construct battery storage. Based on 16 scenarios the study determines a levelized cost of hydrogen of 2.34–3.08 $/kg for Saudi Arabia compared with 3.06–3.69 $/kg in Germany. Subsequently a detailed sensitivity analysis considers various discount rates for both countries. It is concluded that even when considering shipment costs from Saudi Arabia to Germany (~1 $/kg) green H2 can still be competitively delivered from Saudi Arabia to Germany.

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.