Production & Supply Chain

The transition towards clean and economically viable hydrogen production is crucial for ensuring energy sustainability and mitigating climate change. This transition can be effectively facilitated by using renewable energy sources and advanced hydrogen production methods. Methane pyrolysis and water electrolysis emerge as crucial techniques for achieving hydrogen production with minimal carbon intensity. Recognizing the unique opportunity presented by solar energy for both processes this study presents a comparative techno-economic analysis between solar-based molten salt methane pyrolysis (SMSMP) and solar-based solid oxide electrolyzer cell (SSOEC). This study offers a guideline for selecting SMSMP vs SSOEC for cities across theworld. In particular a comprehensive case study including five cities worldwide—San Antonio Edmonton Auckland Seville and Lyon—is conducted utilizing their dynamic solar data and localized prices of methane and electricity to provide a realistic comparison. The results indicate the superior economic feasibility of SMSMP across all case studies. Among different case studies San Antonio and Auckland have the lowest hydrogen costs for SMSMP (2.31 $/kgH2) and SSOEC (5.19 $/kgH2) respectively. It was also concluded that SMSMP is preferred over SSOEC in average to ideal solar conditions given its full dependency on solar thermal energy. However the SSOEC has the potential to achieve better economic feasibility by incorporating clean hydrogen tax incentives and reducing the costs associated with renewable energy infrastructure in the future.

This review presents a broad exploration of the techno economic evaluation of different technologies utilized in the production of hydrogen from both renewable and non-renewable sources. These encompass methods ranging from extracting hydrogen from fossil fuels or biomass to employing microbial processes electrolysis of water and various thermochemical cycles. A rigorous techno-economic evaluation of hydrogen production technologies can provide a critical cost comparison for future resource allocation priorities and trajectory. This evaluation will have a great impact on future hydrogen production projects and the development of new approaches to reduce overall production costs and make it a cheaper fuel. Different methods of hydrogen production exhibit varying efficiencies and costs: fast pyrolysis can yield up to 45% hydrogen at a cost range of $1.25 to $2.20 per kilogram while gasification operating at temperatures exceeding 750°C faces challenges such as limited small-scale coal production and issues with tar formation in biomass. Steam methane reforming which constitutes 48% of hydrogen output experiences cost fluctuations depending on scale whereas auto-thermal reforming offers higher efficiency albeit at increased costs. Chemical looping shows promise in emissions reduction but encounters economic hurdles and sorptionenhanced reforming achieves over 90% hydrogen but requires CO2 storage. Renewable liquid reforming proves effective and economically viable. Additionally electrolysis methods like PEM aim for costs below $2.30 per kilogram while dark fermentation though cost-effective grapples with efficiency challenges. Overcoming technical economic barriers and managing electricity costs remains crucial for optimizing hydrogen production in a low-carbon future necessitating ongoing research and development efforts.

This scientific article presents a developed model for optimising the scheduling of hydrogen production processes addressing the growing demand for efficient and sustainable energy sources. The study focuses on the integration of advanced scheduling techniques to improve the overall performance of the hydrogen electrolyser. The proposed model leverages constraint programming and satisfiability (CP-SAT) techniques to systematically analyse complex production schedules considering factors such as production unit capacities resource availability and energy costs. By incorporating real-world constraints such as fluctuating energy prices and the availability of renewable energy the optimisation model aims to improve overall operational efficiency and reduce production costs. The CP-SAT was applied to achieve more efficient control of the electrolysis process. The optimisation of the scheduling task was set for a 24 h time period with time resolutions of 1 h and 15 min. The performance of the proposed CP-SAT model in this study was then compared with the Monte Carlo Tree Search (MCTS)-based model (developed in our previous work). The CP-SAT was proven to perform better but has several limitations. The model response to the input parameter change has been analysed.

The analysis of Carbon Footprint (CF) for technology of hydrogen production from cleaned coke oven gas was performed. On the basis of real data and simulation calculations of the production process of hydrogen from coke gas emission indicators of carbon dioxide (CF) were calculated. These indicators are associated with net production of electricity and thermal energy and direct emission of carbon dioxide throughout a whole product life cycle. Product life cycle includes: coal extraction and its transportation to a coking plant the process of coking coal purification and reforming of coke oven gas carbon capture and storage. The values were related to 1 Mg of coking blend and to 1 Mg of the hydrogen produced. The calculation is based on the configuration of hydrogen production from coke oven gas for coking technology available on a commercial scale that uses a technology of coke dry quenching (CDQ). The calculations were made using ChemCAD v.6.0.2 simulator for a steady state of technological process. The analysis of carbon footprint was conducted in accordance with the Life Cycle Assessment (LCA).

Hydrogen is seen as a key element for the transition from a fossil fuel based economy to a renewable sustainable economy. Hydrogen can be used either directly as an energy carrier or as a feedstock for the reduction of CO2 to synthetic hydrocarbons. Hydrogen can be produced by electrolysis decomposing water in oxygen and hydrogen. This paper presents an overview of the three major electrolysis technologies: acidic (PEM) alkaline (AEL) and solid oxide electrolysis (SOEC). An updated list of existing electrolysers and commercial providers is provided. Most interestingly the specific prices of commercial devices are also given when available. Despite tremendous development of the PEM technology in the past decades the largest and most efficient electrolysers are still alkaline. Thus this technology is expected to play a key role in the transition to the hydrogen society. A detailed description of the components in an alkaline electrolyser and an analytical model of the process are provided. The analytical model allows investigating the influence of the different operating parameters on the efficiency. Specifically the effect of temperature on the electrolyte conductivity—and thus on the efficiency—is analyzed. It is found that in the typical range of operating temperatures for alkaline electrolysers of 65˚C - 220˚C the efficiency varies by up to 3.5 percentage points increasing from 80% to 83.5% at 65˚C and 220˚C respectively.

This paper presents an advanced Adaptive Sliding Mode Control (ASMC) strategy specifically developed for a hydrogen production system based on a Proton Exchange Membrane electrolyzer (PEM electrolyzer). This work utilized a static model of the PEM electrolyzer characterized by its V-I electrical characteristic which was approximated by a linear equation. The ASMC was designed to estimate the coefficients of this equation which are essential for designing an efficient controller. The primary objective of the proposed control strategy is to ensure the overall stability of the integrated system comprising both an interleaved buck converter (IBC) and PEM electrolyzer. The control framework aims to maintain the electrolyzer voltage at its reference value despite the unknown coefficients while ensuring equal current distribution among the three parallel legs of the IBC. The effectiveness of the proposed approach was demonstrated through numerical simulations in MATLAB-SIMULINK and was validated by the experimental results. The results showed that the proposed ASMC achieved a voltage tracking error of less than 2% and a current distribution imbalance of only 1.5%. Furthermore the controller exhibited strong robustness to parameter variations effectively handling fluctuations in the electrolyzer’s ohmic resistance (Rohm) (from ±28.75% to ±40.35%) and in the reversible voltage (Erev) (from ±28.67% to ±40.19%) highlighting its precision and reliability in real-world applications.

Different photoelectrochemical (PEC) artificial-leaf systems have been proposed for green hydrogen production. However their sustainability is not well understood in comparison to conventional hydrogen technologies. To fill this gap this study estimates cradle-to-grave life cycle environmental impacts and costs of PEC hydrogen production in different provinces in China using diverse tandem solar cells: Ge/GaAs/GaInP (Ge-PEC) GaAs/ GaInAs/GaInP (GaAs-PEC) and perovskite/silicon (P-PEC). These systems are benchmarked against conventional hydrogen production technologies − coal gasification (CG) and steam methane reforming (SMR) − across 18 environmental categories life cycle costs and levelised cost of hydrogen (LCOH). P-PEC emerges as the best options with 36–95 % lower impacts than Ge-PEC and GaAs-PEC across the categories including the climate change impact (0.38–0.52 t CO2 eq./t H2) which is 77–79 % lower. Economically P-PEC shows 81–84 % lower LCOH (2.51–3.81 k$/t). Compared to SMR and CG P-PEC reduces the impacts by 23–98 % saving 3.67–38.5 Mt of CO2 eq./yr. While its LCOH is 5 % higher than that of conventional hydrogen it could be economically competitive with both SMR and CG at 10 % higher solar-to-hydrogen efficiency and 25 % lower operating costs. In contrast Ge-PEC and GaAs-PEC while achieving much lower (81–91 %) climate change and some other impacts than the conventional technologies face significant economic challenges. Their LCOH (21.51–32.82 k$/t for Ge-PEC and 16.96–25.89 k$/t for GaAs-PEC) is 7–9 times higher than that of the conventional hydrogen due to the high solar cell costs. Therefore despite their environmental benefits these technologies require substantial cost reductions to become economically viable.

With the growing global focus on hydrogen as a key solution for achieving decarbonization understanding the most cost-effective and environmentally sustainable production methods is crucial. The objective of this study is to evaluate the economic and environmental performance of different renewable energy sources for hydrogen production while also considering the impact of geographic location system sizing and technological efficiency. This study compares the production of green hydrogen powered by onshorewind offshore-wind and solar PV with that of yellow hydrogen (grid-based hydrogen) in terms of cost and environmental impact for a large sample of publicly announced green hydrogen projects in Europe. Using geographic renewable energy data project-specific details and prevailing technological standards we derive each country’s weighted average cost of capital (WACC) to calculate market-based levelized cost of hydrogen. We find onshore-wind projects to have the lowest average levelized cost of green hydrogen followed by offshore-wind and then by solar PV . The costs for yellow hydrogen depend on the price of electricity. Excluding 2022 yellow hydrogen had lower mean costs than solar PV but higher costs than both types of wind. The environmental impact assessment finds significant decarbonization potential for green hydrogen particularly in regions with substantial renewable resources and carbon-intensive energy mixes. The study aggregates the project data at the country level then clusters the analyzed countries based on economic and environmental metrics to derive specific hydrogen strategies. It concludes that substantial governmental support is essential for the large-scale integration of green hydrogen into the energy system to achieve meaningful decarbonization.

Solid oxide electrolysis (SOEL) has emerged as a promising technology for efficient hydrogen production. Its main advantages lie in the high operating temperatures which enhance thermodynamic efficiency and in the ability to supply part of the required energy in the form of heat. Nevertheless improving the long-term durability of stack materials remains a key challenge. Thermal energy can be supplied by dedicated integration with different industrial processes where the main challenge lies in the elevated stack operating temperature (700–900 ◦C). This review provides a comprehensive analysis of the integration of solid oxide electrolysis cells (SOECs) into different industrial applications. Main processes cover methanol production methane production Power-to-Hydrogen systems or the use of reversible solid oxide electrolysis cell (rSOEC) stacks that can operate in both electrolysis and fuel cell mode. The potential of co-electrolysis to increase process flexibility and broaden application areas is also analyzed. The aim is to provide a comprehensive analysis of the integration strategies identify the main technical and economic challenges and highlight recent developments and future trends in the field. A detailed comparison assessment of the different processes is being discussed in terms of electrical and thermal efficiencies and operating parameters as well as Key Performance Indicators (KPIs) for each process. Technical-economic challenges that are currently a barrier to their implementation in industry are also analyzed.

To achieve energy transition hydrogen and carboxylic acids have attracted much attention due to their cleanliness and renewability. Anaerobic fermentation technology is an effective combination of waste biomass resource utilization and renewable energy development. Therefore the utilization of anaerobic fermentation technology is expected to achieve efficient co-production of hydrogen and carboxylic acids. However this process is fundamentally affected by gas–liquid mass transfer kinetics bubble behaviors and system partial pressure. Moreover the related studies are few and unfocused and no systematic research has been developed yet. This review systematically summarizes and discusses the basic mathematical models used for gas–liquid mass transfer kinetics the relationship between gas solubility and mass transfer and the liquid-phase product composition. The review analyzes the roles of the headspace gas composition and partial pressure of the reaction system in regulating co-production. Additionally we discuss strategies to optimize the metabolic pathways by modulating the gas composition and partial pressure. Finally the feasibility of and prospects for the realization of hydrogen and carboxylic acid co-production in anaerobic fermentation systems are outlined. By exploring information related to gas mass transfer and system pressure this review will surely provide an important reference for promoting cleaner production of sustainable energy.