Production & Supply Chain

The exploration of green energy is a demanding issue due to climate change and ecology. Green energy hydrogen is gaining importance in the area of alternative energy sources. Many methods are being explored for this but most of them are utilizing other sources of energy to produce hydrogen. Therefore these approaches are not economic and acceptable at the industrial level. Sunlight and nuclear radiation as free or low-cost energy sources to split water for hydrogen. These methods are gaining importance in recent times. Therefore attempts are made to explore the latest updates in direct radiation water-splitting methods of hydrogen production. This article discusses the advances made in green hydrogen production by water splitting using visible and UV radiations as these are freely available in the solar spectrum. Besides water splitting by gamma radiation (a low-cost energy source) is also reviewed. Eforts are also made to describe the water-splitting mechanism in photo- and gamma-mediated water splitting. In addition to these challenges and future perspectives have also been discussed to make this article useful for further advanced research.

Securing decarbonized economies for energy and commodities will requireabundant and widely available green H2. Ubiquitous wastewaters and nontraditional watersources could potentially feed water electrolyzers to produce this green hydrogen withoutcompeting with drinking water sources. Herein we show that the energy and costs of treatingnontraditional water sources such as municipal wastewater industrial and resource extractionwastewater and seawater are negligible with respect to those for water electrolysis. We alsoillustrate that the potential hydrogen energy that could be mined from these sources is vast.Based on these findings we evaluate the implications of small-scale distributed waterelectrolysis using disperse nontraditional water sources. Techno-economic analysis and lifecycle analysis reveal that the significant contribution of H2 transportation to costs and CO2emissions results in an optimal levelized cost of hydrogen at small- to moderate-scale waterelectrolyzer size. The implications of utilizing nontraditional water sources and decentralizedor stranded renewable energy for distributed water electrolysis are highlighted for severalhydrogen energy storage and chemical feedstock applications. Finally we discuss challengesand opportunities for mining H2 from nontraditional water sources to achieve resilient and sustainable economies for water andenergy.

This paper presents a comprehensive safety assessment of hydrogen production using Alkaline Water Electrolysis (AWE). The study utilizes various risk assessment methodologies including Hazard Identification (HAZID) What-If analysis Fault Tree Analysis (FTA) Event Tree Analysis (ETA) and Bow Tie analysis to systematically identify and evaluate potential hazards associated with the AWE process. Key findings include the identification of critical hazards such as hydrogen leaks oxygen-related risks and maintenance challenges. The assessment emphasizes the importance of robust safety measures including preventive and mitigative strategies to manage these risks effectively. Consequence modeling highlights significant threat zones for thermal radiation and explosion risks underscoring the need for comprehensive safety protocols and emergency response plans. This work contributes valuable insights into hydrogen safety providing a framework for risk assessment and mitigation in hydrogen production facilities crucial for the safe and sustainable development of hydrogen infrastructure in the global energy transition.

Billions of litres of wastewater are produced daily from domestic and industrial areas and whilst wastewater is often perceived as a problem it has the potential to be viewed as a rich source for resources and energy. Wastewater contains between four and five times more energy than is required to treat it and is a potential source of bio-hydrogen—a clean energy vector a feedstock chemical and a fuel widely recognised to have a role in the decarbonisation of the future energy system. This paper investigates sustainable low-energy intensive routes for hydrogen production from wastewater critically analysing five technologies namely photo-fermentation dark fermentation photocatalysis microbial photo electrochemical processes and microbial electrolysis cells (MECs). The paper compares key parameters influencing H2 production yield such as pH temperature and reactor design summarises the state of the art in each area and highlights the scale-up technical challenges. In addition to H2 production these processes can be used for partial wastewater remediation providing at least 45% reduction in chemical oxygen demand (COD) and are suitable for integration into existing wastewater treatment plants. Key advancements in lab-based research are included highlighting the potential for each technology to contribute to the development of clean energy. Whilst there have been efforts to scale dark fermentation electro and photo chemical technologies are still at the early stages of development (Technology Readiness Levels below 4); therefore pilot plants and demonstrators sited at wastewater treatment facilities are needed to assess commercial viability. As such a multidisciplinary approach is needed to overcome the current barriers to implementation integrating expertise in engineering chemistry and microbiology with the commercial experience of both water and energy sectors. The review concludes by highlighting MECs as a promising technology due to excellent system modularity good hydrogen yield (3.6–7.9 L/L/d from synthetic wastewater) and the potential to remove up to 80% COD from influent streams.

Reducing the gap between the electrodes and diaphragm to zero is an often adopted strategy to reduce the ohmic drop in alkaline water electrolyzers for hydrogen production. We provide a thorough account of the current–voltage relationship in such a zero-gap configuration over a wide range of electrolyte concentrations and current densities. Included are voltage components that are not often experimentally quantified like those due to bubbles hydroxide depletion and dissolved hydrogen and oxygen. As is commonly found for zero-gap configurations the ohmic resistance was substantially larger than that of the separator. We find that this is because the relatively flat electrode area facing the diaphragm was not active likely due to separator pore blockage by gas the electrode itself and or solid deposits. Over an e-folding time-scale of ten seconds an additional ohmic drop was found to arise likely due to gas bubbles in the electrode holes. For electrolyte concentrations below 0.5 M an overpotential was observed associated with local depletion of hydroxide at the anode. Finally a high supersaturation of hydrogen and oxygen was found to significantly increase the equilibrium potential at elevated current densities. Most of these voltage losses are shown to be easily avoidable by introducing a small 0.2 mm gap greatly improving the performance compared to zero-gap.

The study examines the methods for producing hydrogen using solar energy as a catalyst. The two commonly recognised categories of processes are direct and indirect. Due to the indirect processes low efficiency excessive heat dissipation and dearth of readily available heat-resistant materials they are ranked lower than the direct procedures despite the direct procedures superior thermal performance. Electrolysis bio photosynthesis and thermoelectric photodegradation are a few examples of indirect approaches. It appears that indirect approaches have certain advantages. The heterogeneous photocatalytic process minimises the quantity of emissions released into the environment; thermochemical reactions stand out for having low energy requirements due to the high temperatures generated; and electrolysis is efficient while having very little pollution created. Electrolysis has the highest exergy and energy efficiency when compared to other methods of creating hydrogen according to the evaluation.

Hydrogen has been receiving a lot of attention in the last few years since it is seen as a viable yet not thoroughly dissected alternative for addressing climate change issues namely in terms of energy storage and therefore great investments have been made towards research and development in this area. In this context a study about the main options for hydrogen production along with the analysis of a variety of the main power electronics converter topologies for such applications is presented as the purpose of this paper. Much of the analyzed available literature only discusses a few types of hydrogen production methods so it becomes crucial to include an analysis of all known types of methods for producing hydrogen according to their production type along with the color code associated with each type and highlighting the respective contextualization as well as advantages and disadvantages. Regarding the topologies of power electronics converters most suitable for hydrogen production and more specifically for green hydrogen production a list of them was analyzed through the available literature and a discussion of their advantages and disadvantages is presented. These topologies present the advantage of having a low ripple current output which is a requirement for the production of hydrogen.

Low-cost alkaline water electrolysis from renewable energy sources (RESs) is suitable for large-scale hydrogen production. However fluctuating RESs lead to poor performance of alkaline water electrolyzers (AWEs) at low loads. Here we explore two urgent performance issues: inefficiency and inconsistency. Through detailed operation process analysis of AWEs and the established equivalent electrical model we reveal the mechanisms of inefficiency and inconsistency of low-load AWEs are related to the physical structure and electrical characteristics. Furthermore we propose a multi-mode self-optimization electrolysis converting strategy to improve the efficiency and consistency of AWEs. In particular compared to a conventional dc power supply we demonstrate using a lab-scale and large-scale commercially available AWE that the maximum efficiency can be doubled while the operation range of the electrolyzer can be extended from 30–100% to 10–100% of rated load. Our method can be easily generalized and can facilitate hydrogen production from RESs.

Deployment of innovative renewable-based energy applications are critical for reducing CO2 emissions and achieving global climate neutrality. This work evaluates the production of decarbonized green H2 based on sorption-enhanced biomass (sawdust) gasification. The calcium-based sorbent was evaluated in a looping cycle configuration as sorption material to enhance both the CO2 capture rate and the energy-efficient hydrogen production. The investigated concept is set to produce 100 MWth high purity hydrogen (>99.95% vol.) with very high decarbonization yield (>98–99%) using woody biomass as a fuel. Conventional biomass (sawdust) gasification systems with and without CO2 capture capability are also assessed for the calculation of energy and economic penalties induced by decarbonization. The results show that the decarbonized green hydrogen manufacture by sorption-enhanced biomass gasification shows attractive performances e.g. high overall energy efficiency (about 50%) reduced energy and economic penalties for almost total decarbonization (down to 8 net efficiency points) low specific carbon emissions at system level (lower than 7 kg/MWh) and negative CO2 emission for whole biomass value chain (about − 518.40 kg/MWh). However significant developments (e.g. improving reactor design and fuel/sorbent conversion yields reducing sorbent make-up etc.) are still needed to advance this innovative concept from present level to industrial sizes.

With rapidly depleting fossil fuels and growing environmental alarms due to their usage hydrogen as an energy vector provides a clean and sustainable solution. However the challenge lies in replacing mature fossil fuel technology with efficient and economical hydrogen production. This paper provides a technoeconomic and environmental overview of H2 production technologies. Reforming of fossil fuels is still considered as the backbone of large-scale H2 production. Whereas renewable hydrogen has technically advanced and improved its cost remains an area of concern. Finding alternative catalytic materials would reduce such costs for renewable hydrogen production. Taking a mid-term timeframe a viable scenario is replacing fossil fuels with solar hydrogen production integrated with water splitting methods or from biomass gasification. Gasification of biomass is the preferred option as it is carbon neutral and costeffective producing hydrogen at 1.77 – 2.77 $/kg of H2. Among other uses of hydrogen in industrial applications the most viable approach is to use it in hydrogen fuel cells for generating electricity. Commercialization of fuel cell technology is hindered by a lack of hydrogen infrastructure. Fuel cells and hydrogen production units should be integrated to achieve desired results. Case studies of different fuel cells and hydrogen production technologies are presented at the end of this paper depicting a viable and environmentally acceptable approach compared with fossil fuels.