Production & Supply Chain

This paper focuses on the battle for a dominant design for renewable hydrogen electrolysis in which the designs alkaline and proton exchange membrane compete for dominance. First a literature review is performed to determine the most relevant factors that influence technology dominance. Following that a Best Worst Method analysis is conducted by interviewing multiple industry experts. The most important factors appear to be: Price Safety Energy consumption Flexibility Lifetime Stack size and Materials used. The opinion of experts on Proton Exchange Membrane and alkaline electrolyser technologies is slightly skewed in favour of alkaline technologies. However the margin is too small to identify a winner in this technology battle. The following paper contributes to the ongoing research on modelling the process of technology selection in the energy sector.

The global issue of climate change caused by humans and its inextricable linkage to our present and future energy demand presents the biggest challenge facing our globe. Hydrogen has been introduced as a new renewable energy resource. It is envisaged to be a crucial vector in the vast low-carbon transition to mitigate climate change minimize oil reliance reinforce energy security solve the intermittency of renewable energy resources and ameliorate energy performance in the transportation sector by using it in energy storage energy generation and transport sectors. Many technologies have been developed to generate hydrogen. The current paper presents a review of the current and developing technologies to produce hydrogen from fossil fuels and alternative resources like water and biomass. The results showed that reformation and gasification are the most mature and used technologies. However the weaknesses of these technologies include high energy consumption and high carbon emissions. Thermochemical water splitting biohydrogen and photo-electrolysis are long-term and clean technologies but they require more technical development and cost reduction to implement reformation technologies efficiently and on a large scale. A combination of water electrolysis with renewable energy resources is an ecofriendly method. Since hydrogen is viewed as a considerable game-changer for future fuels this paper also highlights the challenges facing hydrogen generation. Moreover an economic analysis of the technologies used to generate hydrogen is carried out in this study.

The world is facing an urgent global climate challenge and hydrogen (H2) is increasingly valued as a carbon-free energy carrier that can play a prominent role in decarbonising economies. However the environmental impact of the different methods for hydrogen production are sometimes overlooked. This work provides a comprehensive overview of the environmental impacts and costs of a diverse range of methods for producing hydrogen. Ninety nine life cycle assessments (LCAs) of hydrogen production published between 2015 and 2022 are categorised by geography production method energy source goal and scope and compared by data sources and methodology. A meta-analysis of methodological choices is used to identify a subset of mutually comparable studies whose results are then compared initially by global warming potential (GWP) then low-GWP scenarios are compared by other indicators. The results show that the lowest GWP is achieved by methods that are currently more expensive (~US $4–9/kg H2) compared to the dominant methods of producing hydrogen from fossil fuels (~US $1–2/kg H2). The research finds that data are currently limited for comparing environmental indicators other than GWP such as terrestrial acidification or freshwater eutrophication. Recommendations are made for future LCAs of hydrogen production.

This work focuses on the design of a reactor for producing clean hydrogen from methane pyrolysis in the form of the so-called “turquoise hydrogen”. In addition to its simple geometry the fundamental concept and the main novelty of the proposed method rely on using part of the methane to produce the required heat needed for the thermal decomposition of methane (TDM). The reactor configuration for hydrogen production is shown to produce significant advantages in terms of greenhouse gas (GHG) emissions. A reactive flow CFD model incorporating also soot formation mechanism has been first developed and validated with experimental results available in the literature and then used to design and characterize the performances of proposed reactor configuration. 3D CFD simulations have been carried out to predict the behavior of the reactor configuration; a sensitivity analysis is used for clearing the aspect related to key environmental parameters e.g. the global warming impact (GWI). The real potential of the proposed design resides in the low emissions and high efficiency with which hydrogen is produced at the various operating conditions (very flexible reactor) albeit subject to the presence of carbon by-product. This suggests that this type of methane conversion system could be a good substitute for the most common hydrogen production technologies.

Direct air capture (DAC) is considered one of the mitigation strategies in most of the future scenarios trying to limit global temperature to 1.5 ◦C. Given the high expectations placed on DAC for future decarbonisation this study presents an extensive review of DAC technologies exploring a number of techno-economic aspects including an updated collection of the current and planned DAC projects around the world. A dedicated analysis focused on the production of synthetic methane methanol and diesel from DAC and electrolytic hydrogen in the European Union (EU) is also performed where the carbon footprint is analysed for different scenarios and energy sources. The results show that the maximum grid carbon intensity to obtain negative emissions with DAC is estimated at 468 gCO2e/kWh which is compliant with most of the EU countries’ current grid mix. Using only photovoltaics (PV) and wind negative emissions of at least −0.81 tCO2e/tCO2 captured can be achieved. The maximum grid intensities allowing a reduction of the synthetic fuels carbon footprint compared with their fossil-fuels counterparts range between 96 and 151 gCO2e/kWh. However to comply with the Renewable Energy Directive II (REDII) sustainability criteria to produce renewable fuels of non-biological origin the maximum stays between 30.2 to 38.8 gCO2e/kWh. Only when using PV and wind is the EU average able to comply with the REDII threshold for all scenarios and fuels with fuel emissions ranging from 19.3 to 25.8 gCO2e/MJ. These results highlight the importance of using renewable energies for the production of synthetic fuels compliant with the EU regulations that can help reduce emissions from difficult-to-decarbonise sectors.

This research delineates a pivotal advancement in the domain of sustainable energy systems with a focused emphasis on the integration of renewable energy sources—predominantly wind and solar power—into the hydrogen production paradigm. At the core of this scientific endeavor is the formulation and implementation of a deep-learning-based framework for short-term localized weather forecasting specifically designed to enhance the efficiency of hydrogen production derived from renewable energy sources. The study presents a comprehensive evaluation of the efficacy of fully connected neural networks (FCNs) and convolutional neural networks (CNNs) within the realm of deep learning aimed at refining the accuracy of renewable energy forecasts. These methodologies have demonstrated remarkable proficiency in navigating the inherent complexities and variabilities associated with renewable energy systems thereby significantly improving the reliability and precision of predictions pertaining to energy output. The cornerstone of this investigation is the deployment of an artificial intelligence (AI)-driven weather forecasting system which meticulously analyzes data procured from 25 distinct weather monitoring stations across Latvia. This system is specifically tailored to deliver short-term (1 h ahead) forecasts employing a comprehensive sensor fusion approach to accurately predicting wind and solar power outputs. A major finding of this research is the achievement of a mean squared error (MSE) of 1.36 in the forecasting model underscoring the potential of this approach in optimizing renewable energy utilization for hydrogen production. Furthermore the paper elucidates the construction of the forecasting model revealing that the integration of sensor fusion significantly enhances the model’s predictive capabilities by leveraging data from multiple sources to generate a more accurate and robust forecast. The entire codebase developed during this research endeavor has been made available on an open access GIT server.

The abundant plastic wastes become an imperative global issue and how to handle these organic wastes gains growing scientific and industrial interest. Recently converting plastic wastes into hydrogen fuel has been investigated and the “waste-to-value” practice accelerates the circular economy. To accelerate the development of plastic-to-hydrogen conversion in this review recent advances in plastic-to-hydrogen conversion via thermochemical photocatalytic and electrocatalytic routes are analyzed. All of the thermo- photo- and electrochemical processes can transform different plastic wastes into hydrogen and the hydrogen production efficiency depends heavily on the selected techniques operating parameters and applied catalysts. The application of rational-designed catalysts can promote the selective production of hydrogen from plastic feedstocks. Further studies on process optimization cost-effective catalyst design and mechanism investigation are needed.

The production of hydrogen from photovoltaics (PV) has gained attention due to its potential as an energy vector. In this context there are two basic configurations for electrically coupling PV to hydrogen electrolyzers: direct and indirect. The direct configuration operates variably based on meteorological conditions but has simplicity as an advantage. The indirect configuration involves a power stage (PS) with a maximum power point tracker and a DC-DC converter maintaining an optimal power transfer from PV to electrolyzers but incurs losses at the PS. The direct configuration avoids these losses but requires a specific design of the PV generator to achieve high electrical transfer. The comparative analysis of hydrogen production between these two approaches indicates that the indirect paradigm yields a 37.5% higher hydrogen output throughout a typical meteorological year compared to the optimized direct configuration. This increase enhances the overall sunlight-to-hydrogen efficiency elevating it from 5.0% in the direct case to 6.9% in the indirect one. Furthermore the direct setup sensitive to PV power fluctuations suffers an 18% reduction in hydrogen production with just a 5% reduction in photogenerated power. Under optimal performance the direct coupling produces less hydrogen unless the DCDC converter efficiency drops 17% below commercial standards.

In response to the growing significance of hydrogen as a clean energy carrier this study investigates the advanced rectifier technologies employed in electrolytic hydrogen production. First the topologies of three rectifiers typically employed in industry—24-pulse thyristor rectifiers insulated gate bipolar transistor (IGBT) rectifiers and 24-pulse diode rectifiers with multi-phase choppers—are described in detail. Subsequently at a constant 5 MW power level the three rectifiers are compared in terms of rectifier efficiency gridside power quality power factor and overall investment cost. The results indicate that in comparison to the other two rectifiers the thyristor rectifier provides superior efficiency and cost advantages thereby maintaining a dominant market share. Additionally case studies of rectifier power supplies from three real-world industrial projects are presented along with actual grid-side power quality data. Finally the challenges potential applications and future prospects of rectifiers in renewable energy-based hydrogen production are discussed and summarized.

Green hydrogen a critical element in the shift towards sustainable energy is traditionally produced by electrolysis powered by solar photovoltaic (PV) systems. This research explores the potential of underexploited photovoltaic thermal (PV-T) systems for efficient green hydrogen generation. This paper compares this advanced technology performance and economic viability against conventional PV setups. This paper uses TRNSYS simulation software to analyze two distinct solar-based hydrogen production configurations – PV and PV-T – across diverse climatic conditions in Doha Tunis and Stuttgart. The paper’s findings indicate that PV-T significantly outperforms PV in hydrogen generation across diverse climates (Doha Tunis Stuttgart). For instance in Doha PV-T systems increase hydrogen output by 78% in Tunis by 59% and in Stuttgart by 25%. An economic assessment reveals PV panels as the most cost-effective option with hydrogen production costs ranging from $4.92/kg to $9.66/kg across the studied locations. For PV-T collectors the hydrogen cost range from $6.66/kg to $16.80/kg across the studied locations. Nevertheless this research highlights the potential of PV-T technology to enhance the efficiency and economic viability of green hydrogen production. These findings offer valuable insights for policymakers investors and researchers pursuing more efficient solutions for sustainable energy.