Publications

The utilization of hydrogen fuel in gas turbines brings significant changes to the thermophysical properties of flue gas including higher specific heat capacities and an enhanced steam content. Therefore hydrogen-fueled gas turbines are susceptible to health degradation in the form of steam-induced corrosion and erosion in the hot gas path. In this context the fault diagnosis of hydrogen-fueled gas turbines becomes indispensable. To the authors’ knowledge there is a scarcity of fault diagnosis studies for retrofitted gas turbines considering hydrogen as a potential fuel. The present study however develops an artificial neural network (ANN)-based fault diagnosis model using the MATLAB environment. Prior to the fault detection isolation and identification modules physics-based performance data of a 100 kW micro gas turbine (MGT) were synthesized using the GasTurb tool. An ANN-based classification algorithm showed a 96.2% classification accuracy for the fault detection and isolation. Moreover the feedforward neural network-based regression algorithm showed quite good training testing and validation accuracies in terms of the root mean square error (RMSE). The study revealed that the presence of hydrogen-induced corrosion faults (both as a single corrosion fault or as simultaneous fouling and corrosion) led to false alarms thereby prompting other incorrect faults during the fault detection and isolation modules. Additionally the performance of the fault identification module for the hydrogen fuel scenario was found to be marginally lower than that of the natural gas case due to assumption of small magnitudes of faults arising from hydrogen-induced corrosion.

Accurate evaluation of thermo‑fluid dynamic characteristics in tanks is critically important for designing liquid hydrogen tanks for small‑scale hydrogen liquefiers to minimize heat leakage into the liquid and ullage. Due to the high costs most future liquid hydrogen storage tank designs will have to rely on predictive computational models for minimizing pressurization and heat leakage. Therefore in this study to improve the storage efficiency of a small‑scale hydrogen liquefier a three‑ dimensional CFD model that can predict the boil‑off rate and the thermo‑fluid characteristics due to heat penetration has been developed. The prediction performance and accuracy of the CFD model was validated based on comparisons between its results and previous experimental data and a good agreement was obtained. To evaluate the insulation performance of polyurethane foam with three different insulation thicknesses the pressure changes and thermo‑fluid characteristics in a partially liquid hydrogen tank subject to fixed ambient temperature and wind velocity were investigated nu‑ merically. It was confirmed that the numerical simulation results well describe not only the temporal variations in the thermal gradient due to coupling between the buoyance and convection but also the buoyancy‑driven turbulent flow characteristics inside liquid hydrogen storage tanks with differ‑ ent insulation thicknesses. In the future the numerical model developed in this study will be used for optimizing the insulation systems of storage tanks for small‑scale hydrogen liquefiers which is a cost‑effective and highly efficient approach.

With decreasing costs of the clean technologies the balanced scales of the Sustainable Development Goal 7 targets e.g. energy equity (EE) energy security (ES) and environmental sustainability (EVS) are quickly changing. This fundamental balancing process is a key requirement for a net-zero future. Accordingly this research analyzes the regime-switching effect of Hydrogen economy as the green transition sharing economy and economic complexity as the complexity-based and geopolitical risks and energy prices as the geostrategy policies on the Goal 7 targets. To this end a Markov-switching panel vector autoregressive method with regime-heteroskedasticity is applied to study advancing the Goal 7 in the world's twenty-five large energy consumers during 2004–2020. Concerning the parameters and statistics of the model the results refer to the existence of two regimes associated with the Goal 7 corners called “upward and downward” regimes for EE and “slightly upward and sharply upward” regimes for ES and EVS. It is revealed that the vulnerability of EE and ES targets is considerably reduced when the regime switches to the dominant regime that is “downward” and “slightly upward” regimes respectively and that of the EVS target remains unaffected. Through the impulse-response analysis the findings denote that the first hypothesis of the efficiency of the Hydrogen economy in promoting the Goal 7 targets is insignificant. However the significant short-term and dynamic shock effects of the complexity-based and geostrategy policies on the Hydrogen economy are detected which will be a feasible alternative assessment in advancing the Goal 7. Further the complexity-based policies support the Goal 7 targets under different regimes especially in the short- and medium-term. Hence the second hypothesis regarding the effectiveness of the complexity-based policies in promoting Goal 7 targets is confirmed. The third hypothesis concerning the complexity of the impact of geostrategy policies on the Goal 7 targets is verified. Particularly the switching process towards the Goal 7 may not necessarily be restricted by the geopolitical risks. Moreover EE is supported through energy prices in the short-term under both regimes while they are non-conductive to promote ES and EVS through time. Accordingly the decision-makers should acknowledge adopting a regime-switching path forward for ensuring the time-varying balanced growth of the Goal 7 targets as the impact of the suggested policy instruments is asymmetric.

The import of hydrogen and derivatives forms part of many national strategies and is fundamental to achieving climate protection targets. This paper provides an overview and technical comparison of import pathways for hydrogen and derivatives in terms of efficiency technological maturity and development and construction times with a focus on the period up to 2030. The import of hydrogen via pipeline has the highest system efficiency at 57–67 % and the highest technological maturity with a technology readiness level (TRL) of 8–9. The import of ammonia and methanol via ship and of SNG via pipeline shows efficiencies in the range of 39–64 % and a technological maturity of TRL 7 to 9 when using point sources. Liquid hydrogen LOHC and Fischer-Tropsch products have the lowest efficiency and TRL in comparison. The use of direct air capture (DAC) reduces efficiency and TRL considerably. Reconversion of the derivatives to hydrogen is also associated with high losses and is not achievable for all technologies on an industrial scale up to 2030. In the short to medium term import routes for derivatives that can utilise existing infrastructures and mature technologies are the most promising for imports. In the long term the most promising option is hydrogen via pipelines.

Green hydrogen generated from water through renewable energies like solar and wind is a key player in sus tainable energy. It only produces water when used making it a clean energy source. However the inconsistent nature of solar and wind energy highlights the need for storage solutions where green hydrogen is promising. This study uniquely combines green hydrogen (GH) and renewable energy (RE) domains using a comprehensive bibliometric approach covering 2018–2022. It identifies emerging trends collaboration networks and key contributors that shape the global landscape of GH research. Our findings show a significant yearly growth in this research field averaging 93.56 %. The study also identifies China Germany India and Italy as leaders among 76 countries involved in this area. Research trends have shifted from technical details to social and economic factors. Given the increasing global commitment to achieving carbon neutrality understanding the evolution and integration of GH within RE systems is essential for guiding future research policy-making and technology development. The analysis categorizes the research into seven main themes focusing on green hydrogen’s role in energy transition and storage. Other vital topics include improving hydrogen production methods assessing its climate impact examining its environmental benefits and exploring various production techniques like water electrolysis and photocatalysis. Our analysis reveals a 93.56 % annual growth rate in GH research highlighting key challenges in storage integration and policy development and offering a roadmap for future studies. The study highlights areas needing more exploration such as better storage methods integration with existing energy infrastructures risk management and policy development. The advancement of green hydrogen as a sustainable energy solution depends on innovative research international collaboration and supportive policy frameworks.

The large-scale deployment of technologies that enable energy from renewables is essential for a successful transition to a carbon-neutral future. While photovoltaic panels are one of the main technologies commonly used for harvesting energy from the Sun storage of renewable solar energy still presents some challenges and often requires integration with additional devices. It is believed that hydrogen – being a perfect energy carrier – can become one of the broadly utilised storage alternatives that would effectively mitigate the energy supply and demand issues associated with the intermittent nature of renewable energy sources. Current pathways in the development of green technologies indicate the need for more sustainable material utilisation and more efficient device operation. To address this requirement integration of various technologies for renewable energy harvesting conversion and storage in a single device appears as an advantageous option. From the hydrogen economy perspective systems driven by green solar electricity that allow for (photo)electrochemical water splitting would generate hydrogen with the minimal CO2 footprint. If at the same time one of the device electrodes could store the generated gas and release it on demand the utilisation of critical and often costly elements would be reduced with possible gain in more effective device operation. Although conceptually attractive this cross-disciplinary concept has not gained yet enough attention and only limited number of experimental setups have been designed tested and reported. This review presents the first exhaustive overview and critical examination of various laboratory-scale prototype setups that attempt to combine both the hydrogen production and storage processes in a single unit via integration of a metal hydride-based electrode into a photoelectrochemical cell. The architectures of presented configurations enables direct solar energy to hydrogen conversion and its subsequent storage in a single device which – in some cases – can also release the stored (hydrogen) energy on demand. In addition this work explores perspectives and challenges related with the potential upscaling of reviewed solar-to-hydrogen storage systems trying to map and indicate the main future directions of their technological development and optimization. Finally the review also combines information and expertise scattered among various research fields with the aim of stimulating much-needed exchange of knowledge to accelerate the progress in the development and deployment of optimum green hydrogen-based solutions.

Air compressors in hydrogen fuel cell vehicles play a crucial role in ensuring the stability of the cathode air system. However they currently face challenges related to low efficiency and poor stability. To address these issues the experimental setup for the pneumatic performance of air compressors is established. The effects of operational parameters on energy consumption efficiency and mass flow rate of the air compressor are revealed based on a Morris global sensitivity analysis. Considering a higher flow rate larger efficiency and lower energy consumption simultaneously the optimal operating combination of the air compressor is determined based on grey relational multi-objective optimization. The optimal combination of operational parameters consisted of a speed of 80000 rpm a pressure ratio of 1.8 and an inlet temperature of 18.3 °C. Compared to the average values the isentropic efficiency achieved a 48.23% increase and the mass flow rate rose by 78.88% under the optimal operational combination. These findings hold significant value in guiding the efficient and stable operation of air compressors. The comprehensive methodology employed in this study is applicable further to investigate air compressors for hydrogen fuel cell vehicles.

In the process of building a new power system with new energy sources as the mainstay wind power and photovoltaic energy enter the multiplication stage with randomness and uncertainty and the foundation and support role of large-scale long-time energy storage is highlighted. Considering the advantages of hydrogen energy storage in large-scale cross-seasonal and cross-regional aspects the necessity feasibility and economy of hydrogen energy participation in long-time energy storage under the new power system are discussed. Firstly power supply and demand production simulations were carried out based on the characteristics of new energy generation in China. When the penetration of new energy sources in the new power system reaches 45% long-term energy storage becomes an essential regulation tool. Secondly by comparing the storage duration storage scale and application scenarios of various energy storage technologies it was determined that hydrogen storage is the most preferable choice to participate in large-scale and long-term energy storage. Three long-time hydrogen storage methods are screened out from numerous hydrogen storage technologies including salt-cavern hydrogen storage natural gas blending and solid-state hydrogen storage. Finally by analyzing the development status and economy of the above three types of hydrogen storage technologies and based on the geographical characteristics and resource endowment of China it is pointed out that China will form a hydrogen storage system of “solid state hydrogen storage above ground and salt cavern storage underground” in the future.

The automotive industry is undergoing a profound transformation driven by the need for sustainable and environmentally friendly transportation solutions [1]. In this context fuel cell technology has emerged as a promising alternative offering clean efficient and high-performance power sources for vehicles [2]. Fuel cell vehicles are electric vehicles that use fuel cell systems as a single power source or as a hybrid power source in combination with rechargeable energy storage systems. A typical fuel cell system for electric vehicle is exhibited in Figure 1 which provides a comprehensive demonstration of this kind of complex system. Hydrogen energy is a crucial field in the new energy revolution and will become a key pillar in building a green efficient and secure new energy system. As a critical field for hydrogen utilization fuel cell vehicles will play an important role in the transformation and development of the automotive industry. The development of fuel cell vehicles offers numerous advantages such as strong power outputs safety reliability and economic energy savings [3]. However improvements must urgently be made in existing technologies such as fuel cell stacks (including proton exchange membranes catalysts gas diffusion layers and bipolar plates) compressors and onboard hydrogen storage systems [4]. The advantages and current technological status are analyzed here.

The energy production market based on hydrogen technologies is an innovative solution that will allow the industry to achieve climate neutrality in the future in Poland and in the world. The paper presents the idea of using hydrogen as a modern energy carrier and devices that in cooperation with renewable energy sources produce the so-called green hydrogen and the applicable legal acts that allow for the implementation of the new technology were analyzed. Energy transformation is inevitable and according to reports on good practices in European Union countries hydrogen and the hydrogen value chain (production transport and transmission storage use in transport and energy) have wide potential. Thanks to joint projects and subsidies from the EU initiatives supporting hydrogen technologies are created such as hydrogen clusters and hydrogen valleys and EU and national strategic programs set the main goals. Poland is one of the leaders in hydrogen production both in the world and in Europe. Domestic tycoons from the energy refining and chemical industries are involved in the projects. Eight hydrogen valleys that have recently been created in Poland successfully implement the assumptions of the “Polish Hydrogen Strategy until 2030 with a perspective until 2040” and “Energy Policy of Poland until 2040” which are in line with the assumptions of the most important legal acts of the EU including the European Union’s energy and climate policy the Green Deal and the Fit for 55 Package. The review of the analysis of the development of hydrogen technologies in Poland shows that Poland does not differ from other European countries. As part of the assumptions of the European Hydrogen Strategy and the trend related to the management of energy surpluses electrolyzers with a capacity of at least 6 GW will be installed in Poland in 2020–2024. It is also assumed that in the next phase planned for 2025–2030 hydrogen will be a carrier in the energy system in Poland. Poland as a member of the EU is the creator of documents that take into account the assumptions of the European Union Commission and systematically implement the assumed goals. The strategy of activities supporting the development of hydrogen technologies in Poland and the value chain includes very extensive activities related to among others obtaining hydrogen using hydrogen in transport energy and industry developing human resources for the new economy supporting the activities of hydrogen valley stakeholders building hydrogen refueling stations and cooperation among Poland Slovakia and the Czech Republic as part of the HydrogenEagle project.

Given the urgency to combat climate change and ensure environmental sustainability this review examines the transition to net-zero emissions in chemical and process industries. It addresses the core areas of carbon emissions reduction efficient energy use and sustainable practices. What is new however is that it focuses on cutting-edge technologies such as biomass utilization biotechnology applications and waste management strategies that are key drivers of this transition. In particular the study addresses the unique challenges faced by industries such as cement manufacturing and highlights the need for innovative solutions to effectively reduce their carbon footprint. In particular the role of hydrogen as a clean fuel is at the heart of revolutionizing the chemical and process sectors pointing the way to cleaner and greener operations. In addition the manuscript explores the immense importance of the European Green Deal and the Sustainable Development Goals (SDGs) for the chemical industry. These initiatives provide a clear roadmap and framework for advancing sustainability driving innovation and reducing the industry’s environmental impact and are a notable contribution to the existing body of knowledge. Ultimately alignment with the European Green Deal and the SDGs can bring numerous benefits to the chemical industry increasing its competitiveness promoting societal well-being and supporting cross-sector collaboration to achieve shared sustainability goals. By highlighting the novelty of integrating cutting-edge technologies addressing unique industrial challenges and positioning global initiatives this report offers valuable insights to guide the chemical and process industries on their transformative path to a sustainable future.

Hydrogen substitution in applications fueled by compressed natural gas arises as a potential alternative to fossil fuels and it may be the key to an effective hydrogen economy transition. The reduction of greenhouse gas emissions especially carbon dioxide and unburned methane as hydrogen is used in transport and industry applications makes its use an attractive option for a sustainable future. The purpose of this research is to examine the gradual adoption of hydrogen as a fuel for light-duty transportation. Particularly the study focuses on evaluating the performance and emissions of a single-cylinder port fuel injection spark-ignition engine as hydrogen is progressively increased in the natural gas-based fuel blend. Results identify the optimal conditions for air dilution and engine operation parameters to achieve the best performance. They corroborate that the dilution rate has to be adjusted to control pollutant emissions as the percentage of hydrogen is increased. Moreover the study identifies the threshold for hydrogen substitution below which the reduction of carbon dioxide emissions due to efficiency gains is negligible compared to the reduction of the carbon content in the fuel blend. These findings will help reduce the environmental footprint of light-duty transportation not only in the long term but also in the short and medium terms.

Hydrogen is anticipated to play a key role in global decarbonization and within the UK’s pathway to achieving net zero targets. However as the production of hydrogen expands in line with government strategies a key concern is where this hydrogen will be stored for later use. This study assesses the different large-scale storage options in geological structures available to the UK and addresses the surrounding uncertainties moving towards establishing a hydrogen economy. Currently salt caverns look to be the most favourable option considering their proven experience in the storage of hydrogen especially high purity hydrogen natural sealing properties low cushion gas requirement and high charge and discharge rates. However their geographical availability within the UK can act as a major constraint. Additionally a substantial increase in the number of new caverns will be necessary to meet the UK’s storage demand. Salt caverns have greater applicability as a good short-term storage solution however storage in porous media such as depleted hydrocarbon reservoirs and saline aquifers can be seen as a long-term and strategic solution to meet energy demand and achieve energy security. Porous media storage solutions are estimated to have capacities which far exceed projected storage demand. Depleted fields have generally been well explored prior to hydrocarbon extraction. Although many saline aquifers are available offshore UK geological characterizations are still required to identify the right candidates for hydrogen storage. Currently the advantages of depleted gas reservoirs over saline aquifers make them the favoured option after salt caverns.

The article examines the feasibility of implementing standalone hydrogen-based renewable energy systems in Spanish residential buildings specifically analyzing the optimization of a solar-battery and solar-hydrogen system for a building with 20 dwellings in Spain. The study initially assesses two standalone setups: solarbattery and solar-hydrogen. Subsequently it explores scenarios where these systems are connected to the grid to only generate and sell surplus energy. A scenario involving grid connection for self-consumption without storage serves as a benchmark for comparison. All system optimizations are designed to meet energy demands without interruptions while minimizing costs as determined by a techno-economic analysis. The systems are sized using custom software that incorporates an energy management system and employs the Jaya algorithm for optimization. The findings indicate that selling surplus energy can be economically competitive and enhance the efficiency of grid-connected self-consumption systems representing the study’s main innovation. The conclusion highlights the economic and technical potential of an autonomous hybrid energy system that includes hydrogen with the significant remaining challenge being the development of a regulatory framework to support its technical feasibility in Spain.

Nowadays one of the hottest topic in the automotive engineering community is the reduction of fossil fuels. Hydrogen is an alternative energy source that is already providing clean renewable and efficient power being used in fuel cells. Despite being developed since a few decades fuel cells are affected by several hurdles the most impacting one being their cost per unit power. While waiting for their cost reduction and mass-market penetration hydrogen-fueled internal combustion engines (H2ICEs) can be a rapidly applicable solution to reduce pollution caused by the combustion of fossil fuels. Such engines benefit from the advanced technology of modern internal combustion engines (ICEs) and the advantages related to hydrogen combustion although some modifications are needed for conventional liquid-fueled engines to run on hydrogen. The gaseous injection of hydrogen directly into the combustion chamber is a challenge both for the designers and for the injection system suppliers. To reduce uncertainties time and development cost computational fluid dynamics (CFD) tools appear extremely useful since they can accurately predict mixture formation and combustion before the expensive production/testing phase. The high-pressure gaseous injection which takes place in Direct-Injected H2ICEs promotes a super-sonic flow with very high gradients in the zone between the bulk of the injected hydrogen and the flow already inside the combustion chamber. To develop a methodology for an accurate simulation of these phenomena the SoPHy Engine of the Engine Combustion Network group (ECN) is used and presented. This engine is fed through a single nozzle H2-injector; planar laser-induced fluorescence (PLIF) data are available for comparison with the CFD outcomes.

Hydrogen energy has a significant potential in mitigating the intermittency of renewable energy generation by converting the excess of renewable energy into hydrogen through many technologies. Also hydrogen is expected to be used as an energy carrier that contribute to the global decarbonization in transportation industrial and building sectors. Many technologies have been developed to store hydrogen energy. Hydrogen can be stored to be used when needed and thus synchronize generation and consumption. The current paper presents a review on the different technologies used to store hydrogen. The storage capacity advantages drawbacks and development stages of various hydrogen storage technologies were presented and compared.

With the world-wide decision to reduce carbon emissions through the Paris Agreement (2015) the demand for hydrogen-fuelled vehicles has been increasing. Although hydrogen is not a toxic gas it has a wide flammable range (4e75%) and can explode due to static electricity. Therefore studies on hydrogen safety are urgently required. In this study an explosion was induced by applying fire to the lower part of a fuel cell electric vehicle (FCEV). Out of three compressed hydrogen storage tanks installed in the vehicle two did not have hydrogen fuel and one was filled with compressed gaseous hydrogen of 700 bar and forcedly deactivated its temperature-activated pressure relief device. The side-on overpressure transducers were installed by distance in main directions to measure the side-on overpressure generated by the vehicle explosion. A 10 m-long protective barrier was installed on which reflected overpressure displacement and acceleration were measured to examine the effect of attenuation of explosion damage in the event of an accident. The vehicle exploded approximately 11 min after ignition generating a blast wave fireballs and fragments. The results of the experiment showed that the protective barrier could almost completely block explosive pressure smoke and scattering generated during an explosion. Through Probit function analysis the probabilities of an accident occurring were derived based on peak overpressure peak impulse and scattering. The results of this study can be used to develop standard operating procedures (SOPs) for firefighters as the base data for setting the initial operation location and deriving the safe separation distance.

Methanol as a liquid phase hydrogen storage carrier has broad prospects. Although the on-board methanol reforming hydrogen fuel cell system (MRFC) has long been proposed to replace the traditional hydrogen fuel cell vehicle the inherent safety of the system itself has rarely been studied. This paper adopted the improved method of Inherently Safer Process Piping (ISPP) to evaluate the pipeline inherent safety of MRFC. The process data such as temperature pressure viscosity and density were obtained by simulating the MRFC in ASPEN HYSYS. The Process Stream Characteristic Index (PSCI) and risk assessment of jet fire and vapor cloud explosion was carried out for the key streams with those simulated data. The results showed the risk ranks of different pipelines in the MRFC and the countermeasures were given according to different risk ranks. Through the in-depth study of the evaluation results this paper demonstrates the risk degree of the system in more detail and reduces the fuzziness of risk rating. By applying ISPP to the small integrated system of MRFC this paper realizes the leap of inherent safety assessment method in the object and provides a reference for the inherent safety assessment of relevant objects in the future.

Rapid urbanization and globalization are causing a rise in the energy demand within the residential sector. Currently majority of the energy demand for the residential sector being supplied from fossil fuels these sources account for greenhouse gas emissions responsible for anthropogenic-driven climate change. About 85 % of the world’s energy demands are being met by non-renewable sources of energy. An immediate need to shift towards renewable energy sources to generate electricity is the need of the hour. These long-standing renewable energy sources including solar hydropower and wind energy have been crucial pillars of sustainable energy for years. However as their implementation has matured we are increasingly recognizing their limitations. Issues such as the scarcity of suitable locations and the significant carbon footprint associated with constructing renewable energy infrastructure are becoming more apparent. Hydrogen has been found to play a vital role as an energy carrier in framing the energy picture in the 21st century. Currently about 1 % of the global energy demands are being met by hydrogen energy harnessed through renewable methods. Its low carbon emissions when compared to other methods lower comparative production costs and high energy efficiency of 40–60 % make it a suitable choice. Integrating hydrogen production systems with other renewable source of energy such as solar and wind energy have been discussed in this review in detail. With the concepts of green buildings or net zero energy buildings gaining attraction integration of hydrogen-based systems within residential and office sectors through the use of devices such as micro–Combined Heat and Power devices (mCHP) have proven to be effective and efficient. These devices have been found to save the consumed energy by 22 % along with an effective reduction in carbon emissions of 18 % when used in residential sectors. Using the rejected energy from other processes these mCHP devices can prove to be vital in meeting the energy demands of the residential sector. Through the support of government schemes mCHP devices have been widely used in countries such as Japan and Finland and have benefitted from the same. Hydrogen storage is critical for efficient operation of the integrated renewable systems as improper storage of the hydrogen produced could lead to human and environmental disasters. Using boron hydrides or ammonia (121 kg H2/m3 ) or through organic carriers hydrogen can be stored safely and easily regenerated without loss of material. A thorough comparison of all the renewable sources of energy that are used extensively is required to evaluate the merits of using hydrogen as an energy carrier which has been addressed in this review paper. The need to address the research gap in application of mCHP devices in the residential sector and the benefits they provide has been addressed in this review. With about 2500 GW of energy ready to be harnessed through the mCHP devices globally the potential of mCHP systems globally are discussed in detail in this paper. This review discusses challenges and solutions to hydrogen production storage and ways to implement hydrogen technology in the residential sector. This review allows researchers to build a renewable alternative with hydrogen as a clean energy vector for generating electricity in residential systems.

Innovation in key low-carbon technologies plays a supporting role in achieving a high-quality low-carbon transition in the power sector. This paper aims to integrate research on the power transition pathway under the “dual carbon” goals with key technological innovation layouts. First it deeply analyzes the development trends of three key low-carbon technologies in the power sector—new energy storage CCUS and hydrogen energy—and establishes a quantitative model for their technological support in the low-carbon transition of the power sector. On this basis the objective function and constraints of traditional power planning models are improved to create an integrated optimization model for the power transition pathway and key low-carbon technologies. Finally a simulation analysis is conducted using China’s power industry “dual carbon” pathway as a case study. The optimization results include the power generation capacity structure power generation mix carbon reduction pathway and key low-carbon technology development path for China from 2020 to 2060. Additionally the impact of uncertainties in breakthroughs in new energy storage CCUS and hydrogen technologies on the power “dual carbon” pathway is analyzed providing technological and decision-making support for the low-carbon transition of the power sector.

Hydrogen an advanced energy source is growing quickly in its infrastructure and technological development. Urban areas are constructing convergence-type hydrogen refilling stations utilizing existing gas stations to ensure economic viability. However it is essential to conduct a risk analysis as hydrogen has a broad range for combustion and possesses significant explosive capabilities potentially leading to a domino explosion in the most severe circumstances. This study employed quantitative risk assessment to evaluate the range of damage effects of single and domino explosions. The PHAST program was utilized to generate quantitative data on the impacts of fires and explosions in the event of a single explosion with notable effects from explosions. Monte Carlo simulations were utilized to forecast a domino explosion aiming to predict uncertain events by reflecting the outcome of a single explosion. Monte Carlo simulations indicate a 69% chance of a domino explosion happening at a hydrogen refueling station if multi-layer safety devices fail resulting in damage estimated to be three times greater than a single explosion

Hydrogen produced by water electrolysis using renewable energy is a sustainable alternative to steam reformation. As a nascent commercial technology performance and economic comparisons of anion exchange membrane water electrolyzers (AEMWE) to other electrolyzer technology benchmarks are not available. We present a techno-economic model estimating AEMWE's baseline levelized cost of hydrogen (LCOH) at $5.79/kg considering trade-offs between current density efficiency stability capital and operating costs. The optimal current density is 1.38 A cm2 balancing stability and performance for the lowest LCOH. Using low-cost electricity and larger stack sizes AEMWE could achieve $2/kg low-carbon hydrogen. Technical improvements targeting system efficiency particularly reducing overpotentials in hydrogen and oxygen evolution reactions could further reduce LCOH to $1.29/kg approaching U.S. Department of Energy cost targets. There are hopes this model could raise the profile of AEMWE's economic potential to produce green hydrogen and highlight its suitability for decarbonizing the energy sector.

This paper describes a renewable energy system incorporating a hydrogen production unit to address the imbalance between energy supply and demand. The system utilizes renewable energy and hydrogen production energy to release energy to fill the power gap during peak demand power supply for demand peaking and valley filling. The system is optimized by analyzing marine predator behavioral logic and optimizing the system for maximum operational efficiency and best economic value. The results of the study show that after the optimized scheduling of the hydrogen production coupled renewable energy integrated energy system using the improved marine predator optimization algorithm the energy distribution of the whole energy system is good with the primary energy saving rate maintained at 24.75% the CO2 emission reduction rate maintained at 42.32% and the cost saving rate maintained at 0.78%. In addition this paper uses the Adaboost-BP prediction model to predictively analyze the system. The results show that as the price of natural gas increases the advantages of the combined hydrogen production renewable integrated energy system proposed in this paper become more obvious and the cumulative cost over three years is better than other related systems. These research results provide an important reference for the application and development of the system.

The novel constructions of hybrid energy sources using polymer electrolyte fuel cells (PEMFCs) and supercapacitors are developed. Studies on the energy demand and peak electrical power of unmanned ground vehicles (UGVs) weighing up to 100 kg were conducted under various conditions. It was found that the average electrical power required does not exceed ~2 kW under all conditions studied. However under the dynamic electrical load of the electric drive of mobile robots the short peak power exceeded 2 kW and the highest current load was in the range of 80–90 A. The electrical performance of a family of PEMFC stacks built in open-cathode mode was determined. A hydrogen-usage control strategy for power generation cleaning processes and humidification was analysed. The integration of a PEMFC stack with a bank of supercapacitors makes it possible to mitigate the voltage dips. These occur periodically at short time intervals as a result of short-circuit operation. In the second construction the recovery of electrical energy dissipated by a short-circuit unit (SCU) was also demonstrated in the integrated PEMFC stack and supercapacitor bank system. The concept of an energy-efficient mobile and environmentally friendly hydrogen charging unit has been proposed. It comprises (i) a hydrogen anion exchange membrane electrolyser (ii) a photovoltaic installation (iii) a battery storage (iv) a hydrogen buffer storage in a buffer tank (v) a hydrogen compression unit and (vi) composite tanks.

Offshore electricity production mainly by wind turbines and eventually floating PV is expected to increase renewable energy generation and their dispatchability. In this sense a significant part of this offshore electricity would be directly used for hydrogen generation. The integration of offshore energy production into the hydrogen economy is of paramount importance for both the techno-economic viability of offshore energy generation and the hydrogen economy. An analysis of this integration is presented. The analysis includes a discussion about the current state of the art of hydrogen pipelines and subsea cables as well as the storage and bunkering system that is needed on shore to deliver hydrogen and derivatives. This analysis extends the scope of most of the previous works that consider port-to-port transport while we report offshore to port. Such storage and bunkering will allow access to local and continental energy networks as well as to integrate offshore facilities for the delivery of decarbonized fuel for the maritime sector. The results of such state of the art suggest that the main options for the transport of offshore energy for the production of hydrogen and hydrogenated vectors are through direct electricity transport by subsea cables to produce hydrogen onshore or hydrogen transport by subsea pipeline. A parametric analysis of both alternatives focused on cost estimates of each infrastructure (cable/pipeline) and shipping has been carried out versus the total amount of energy to transport and distance to shore. For low capacity (100 GWh/y) an electric subsea cable is the best option. For high-capacity renewable offshore plants (TWh/y) pipelines start to be competitive for distances above approx. 750 km. Cost is highly dependent on the distance to land ranging from 35 to 200 USD/MWh.

This article presents a comprehensive description of the safety system of a real installation that comprises PV panels lithium-ion batteries an electrolyzer H2 storage a fuel cell and a barium chloride/ammonia thermochemical prototype for heat recovery and cooling production. Such a system allows for the increase of the overall efficiency of the H2 chain by exploiting the waste heat and transforming it into a cooling effect particularly useful in tropical regions like French Polynesia. The study provides a great deal of detail regarding practical aspects of the system implementation and a consistent reference to the relevant standards and regulations applicable to the subject matter. More specifically the study covers the ATEX classification of the site the safety features of each component the electrical power distribution the main safety instrumented system fire safety and the force ventilation system. The study also includes safety assessment and a section on lessons learned that could serve as guidance for future installations. In addition an extensive amount of technical data is readily available to the reader in repository (P&ID electrical diagrams etc.).

This research investigated the suitability of air-to-water generator (AWG) technology to address one of the main concerns in green hydrogen production namely water supply. This study specifically addresses water quality and energy sustainability issues which are crucial research questions when AWG technology is intended for electrolysis. To this scope a reasoned summary of the main findings related to atmospheric water quality has been provided. Moreover several experimental chemical analyses specifically focused on meeting electrolysis process requirements on water produced using a real integrated AWG system equipped with certified materials for food contact were discussed. To assess the energy sustainability of AWGs in green hydrogen production a case study was presented regarding an electrolyzer plant intended to serve as energy storage for a 2 MW photovoltaic field on Iriomote Island. The integrated AWG used for the water quality analyses was studied in order to determine its performance in the specific island climate conditions. The production exceeded the needs of the electrolyzer; thus the overproduction was considered for the panels cleaning due to the high purity of the water. Due to such an operation the efficiency recovery was more than enough to cover the AWG energy consumption. This paper on the basis of the quantity results provides the first answers to the said research questions concerning water quality and energy consumption establishing the potential of AWG as a viable solution for addressing water scarcity and enhancing the sustainability of electrolysis processes in green hydrogen production.

The overuse of fossil fuels has caused a serious energy crisis and environmental pollution. Due to these challenges the search for alternative energy sources that can replace fossil fuels is necessary. Hydrogen is a widely acknowledged future energy carrier because of its nonpolluting properties and high energy density. To realize a hydrogen economy in the future it is essential to construct a comprehensive hydrogen supply chain that can make hydrogen a key energy carrier. This paper reviews the various technologies involved in the hydrogen supply chain encompassing hydrogen production storage transportation and utilization technologies. Then the challenges of constructing a hydrogen supply chain are discussed from techno-economic social and policy perspectives and prospects for the future development of a hydrogen supply chain are presented in light of these challenges.

This study identifies supply options for sustainable urban energy systems which are robust to external system changes. A multi-criteria optimization model is used to minimize greenhouse gas (GHG) emissions and financial costs of a reference system. Sensitivity analyses examine the impact of changing boundary conditions related to GHG emissions energy prices energy demands and population density. Options that align with both financial and emission reduction and are robust to system changes are called “no-regret” options. Options sensitive to system changes are labeled as “potential-risk” options.<br/>There is a conflict between minimizing GHG emissions and financial costs. In the reference case the emission-optimized scenario enables a reduction of GHG emissions (-93%) but involves higher costs (+160%) compared to the financially-optimized scenario.<br/>No-regret options include photovoltaic systems decentralized heat pumps thermal storages electricity exchange between sub-systems and with higher-level systems and reducing energy demands through building insulation behavioral changes or the decrease of living space per inhabitant. Potential-risk options include solar thermal systems natural gas technologies high-capacity battery storages and hydrogen for buildiing energy supply.<br/>When energy prices rise financially-optimized systems approach the least-emission system design. The maximum profitability of natural gas technologies was already reached before the 2022 European energy crisis.

Hydrogen-fuelled technologies for home heating and cooking may provide a low-carbon solution for decarbonising parts of the global housing stock. For the transition to transpire the attitudes and perceptions of consumers must be factored into policy making efforts. However empirical studies are yet to explore potential levels of consumer heterogeneity regarding domestic hydrogen acceptance. In response this study explores a wide spectrum of consumer responses towards the prospect of hydrogen homes. The proposed spectrum is conceptualised in terms of the ‘domestic hydrogen acceptance matrix’ which is examined through a nationally representative online survey conducted in the United Kingdom. The results draw attention to the importance of interest and engagement in environmental issues knowledge and awareness of renewable energy technologies and early adoption potential as key drivers of domestic hydrogen acceptance. Critically strategic measures should be taken to convert hydrogen scepticism and pessimism into hope and optimism by recognising the multidimensional nature of consumer acceptance. To this end resources should be dedicated towards increasing the observability and trialability of hydrogen homes in proximity to industrial clusters and hubs where the stakes for consumer acceptance are highest. Progress towards realising a net-zero society can be supported by early stakeholder engagement with the domestic hydrogen acceptance matrix.

This study introduces a method for identifying territories ideal for establishing photovoltaic (PV) plants for green hydrogen (GH2 ) production in the Antofagasta region of northern Chile a location celebrated for its outstanding solar energy potential. Assessing the viability of PV plant installation necessitates a balanced consideration of technical aspects and socio-environmental constraints such as the proximity to areas of ecological importance and indigenous communities to identify potential zones for solar and non-conventional renewable energy (NCRE)-based hydrogen production. To tackle this challenge we propose a methodology that utilizes geospatial analysis integrating Geographic Information System (GIS) tools with sensitivity analysis to determine the most suitable sites for PV plant installation in the Antofagasta region. Our geospatial analysis employs the QGIS software to identify these optimal locations while sensitivity analysis uses the Sørensen–Dice coefficient method to assess the similarity among chosen socio-environmental variables. Applying this methodology to the Antofagasta region reveals that a significant area within a 15 km radius of existing road networks and electrical substations is favorable for photovoltaic projects. Our sensitivity analysis further highlights the limiting effects of socio-environmental factors and their interactions. Moreover our research finds that enlarging areas of socio-environmental importance could increase the total hydrogen production by about 10% per commune indicating the impact of these factors on the potential for renewable energy production.

Safety and reliability have long been recognized as key issues for the development commercialization and implementation of new technologies and infrastructure and hydrogen systems are no exception to this rule. Reliability engineering quantitative risk assessment (QRA) and knowledge exchange each play a key role in proactive addressing safety – before problems happen – and help us learn from problems if they happen. Many international research activities are focusing on both reliability and risk assessment for hydrogen systems. However the element of knowledge exchange is sometimes less visible. To support international collaboration and knowledge exchange the International Energy Agency (IEA) convened a new Technology Collaboration Program “Task 43: Safety and Regulatory Aspects of Emerging Large Scale Hydrogen Energy Applications” started in June 2022. Within Task 43 Subtask E focuses on Hydrogen Systems Safety. This paper discusses the structure of the Hydrogen Systems Safety subtask and the aligned activities and introduces opportunities for future work.

Updates to the separation distances between different exposures and bulk liquid hydrogen systems are included in the 2023 version of NFPA 2: Hydrogen Technologies Code. This work details the models and calculations leading to those distances. The specific models used including the flow of liquid hydrogen through an orifice within the Hydrogen Plus Other Alternative Fuels Risk Assessment Models (HyRAM+) toolkit are described and discussed to emphasize challenges specific to liquid hydrogen systems. Potential hazards and harm affecting individual exposures (e.g. ignition sources air intakes) for different unignited concentrations overpressures and heat flux levels were considered and exposures were grouped into three bins. For each group the distances to a specific hazard criteria (e.g. heat flux level) for a characteristic leak size informed by a risk-analysis led to a hazard distance. The maximum hazard distance within each group was selected to determine a table of separation distances based on internal pressure and pipe size rather than storage volume similar to the bulk gaseous separation distance tables in NFPA 2. The new separation distances are compared to the previous distances and some implications of the updated distances are given.

Fuel cell-battery electric drivetrains are attractive alternatives to reduce the shipping emissions. This research focuses on emission-free cargo vessels and provides insight on the design lifetime operation and costs of hydrogen-hybrid systems which require further research for increased utilization. A representative round trip is created by analysing one-year operational data based on load ramps and power frequency. A low-pass filter controller is employed for power distribution. For the lifetime cost analysis 14 scenarios with varying capital and operational expenses were considered. The Net Present Value of the retrofitted fuel cell-battery propulsion system can be up to $ 2.2 million lower or up to $ 18.8 million higher than the original diesel mechanical configuration highly dependent on the costs of green hydrogen and carbon taxes. The main propulsion system weights and volumes of the two versions are comparable but the hydrogen tank (68 tons 193 m3 ) poses significant design and safety challenges.

Shock-flame interactions (SFI) occur in a variety of combustion scenarios of scientific and engineering interest which can distort the flame extend the flame surface area and subsequently enhance heat release. This process is dominated by Richtmyer-Meshkov instability (RMI) that features the perturbation growth of a density-difference interface (flame) after the shock passage. The main mechanism of RMI is the vorticity deposition results from a misalignment between pressure and density gradients. This paper focuses on the multi-dimensional interactions between shock wave and flame in a hydrogen-air mixture. The simulations of this work were conducted by solving three-dimensional fully-compressible reactive Navier-Stokes equations using a high-order numerical method on a dynamically adapting mesh. The effect of wall friction on the SFI was examined by varying wall boundary condition (free-slip/no-slip) on sidewall. The results show that the global flame perturbation grows faster with the effect of wall friction in the no-slip case than that in the free-slip case in the process of SFI. Two effects of wall friction on SFI were found: (1) flame stretching close to the no-slip wall and (2) damping of local flame perturbation at the no-slip wall. The flame stretch effect leads to a significantly higher growth rate in the global flame perturbation. By contrast the damping effect locally moderates the flame perturbation induced by RMI in close proximity to the no-slip wall because less vorticity is deposited on this part of flame during SFI.

Widespread use of hydrogen and hydrogen-based fuels as energy carriers in society may enable the gradual replacement of fossil fuels by renewable energy sources. Although the development and deployment of the associated technologies and infrastructures represent a considerable bottleneck it is generally acknowledged that neither the technical feasibility nor the economic viability alone will determine the extent of the future use of hydrogen as an energy carrier. Public perception beliefs awareness and knowledge about hydrogen will play a significant role in the further development of the hydrogen economy. To this end the present study examines public perception and awareness of hydrogen in Norway. The approach adopted entailed an open-ended question examining spontaneous associations with the term ‘hydrogen’. The question was fielded to 2276 participants in Wave 25 of the Norwegian Citizen Panel (NCP) an on-line panel that derives random samples from the general population registry. The analysis focused on classifying the responses into negative associations (i.e. barriers towards widespread implementation of hydrogen in society) neutral associations (e.g. basic facts) and positive associations (i.e. drivers towards widespread implementation of hydrogen in society). Each of the 2194 responses were individually assessed by five researchers. The majority of the responses highlighted neutral associations using words such as ‘gas’ ‘water’ and ‘element’. When considering barriers vs. drivers the overall responses tend towards positive associations. Many respondents perceive hydrogen as a clean and environmentally friendly fuel and hydrogen technologies are often associated with the future. The negative sentiments were typically associated with words such as ‘explosive’ ‘hazardous’ and ‘expensive’. Despite an increase in the mentioning of safety-related properties relative to a previous study in the same region the frequency of such references was rather low (4%). The responses also reveal various misconceptions such as hydrogen as a prospective ‘source’ of clean energy.

A wide range of aircraft propulsion technologies is being investigated in current research to reduce the environmental impact of commercial aviation. As the implementation of purely hydrogenpowered aircraft may encounter various challenges on the airport and vehicle side combined hydrogen and kerosene energy sources may act as an enabler for the first operations with liquid hydrogen propulsion technologies. The presented studies describe the conceptual design of such a dual-fuel regional aircraft featuring a retrofit derived from the D328eco under development by Deutsche Aircraft. By electrically assisting the sustainable aviation fuel (SAF) burning conventional turboprop engines with the power of high-temperature polymer-electrolyte fuel cells the powertrain architecture enables a reduction of SAF consumption. All aircraft were modeled and investigated using the Bauhaus Luftfahrt Aircraft Design Environment. A description of this design platform and the incorporated methods to model the hydrogen-hybrid powertrain is given. Special emphasis was laid on the implications of the hydrogen and SAF dual-fuel system design to be able to assess the potential benefits and drawbacks of various configurations with the required level of detail. Retrofit assumptions were applied particularly retaining the maximum takeoff mass while reducing payload to account for the propulsion system mass increase. A fuel cell power allocation of 20% led to a substantial 12.9% SAF consumption decrease. Nonetheless this enhancement necessitated an 18.1% payload reduction accompanied by a 34.5% increment in propulsion system mass. Various additional studies were performed to assess the influence of the power split. Under the given assumptions the design of such a retrofit was deemed viable.

The economic competitiveness of hydrogen-powered aviation highly depends on the supply costs of green liquid hydrogen to enable true-zero CO2 flying. This study uses non-linear energy system optimization to analyze three main liquid hydrogen (LH2) supply pathways for five locations. Final liquid hydrogen costs at the dispenser supply costs could reach 2.04 USD/kgLH2 in a 2050 base case scenario for locations with strong renewable energy source conditions. This could lead to cost-competitive flying with hydrogen. Reflecting techno-economic uncertainties in two additional scenarios the liquid hydrogen cost span at all five airport locations ranges between 1.37–3.48 USD/kgLH2 if hydrogen import options from larger hydrogen markets are also available. Import setups are of special importance for airports with a weaker renewable energy source situation e.g. selected Central European airports. There on-site supply might not only be too expensive but space requirements for renewable energy sources could be too large for feasible implementation in densely populated regions. Furthermore main costs for liquid hydrogen are caused by renewable energy sources electrolysis systems and liquefaction plants. Seven detailed design rules are derived for optimized energy systems for these and the storage components. This and the cost results should help infrastructure planners and general industry and policy players prioritize research and development needs

Battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) whose exhaust pipes emit nothing are examples of zero-emission automobiles. FCEVs should be considered an additional technology that will help battery-powered vehicles to reach the aspirational goal of zero-emissions electric mobility particularly in situations where the customers demand for longer driving ranges and where using batteries would be insufficient due to bulky battery trays and time-consuming recharging. This study stipulates a current evaluation of the status of development and challenges related to (i) research gap to promote fuel-cell based HEVs (ii) key barriers of fuel-cell based HEVs (iii) advancement of electric mobility and their power drive (iv) electrochemistry of fuel cell technology for FCEVs (v) power transformation topologies communication protocols and advanced charging methods (vi) recommendations and future prospects of fuel-cell HEVs and (vii) current research trends of EVs and FCEVs. This article discusses key challenges with fuel cell electric mobility such as low fuel cell performance cold starts problems with hydrogen storage cost-reduction safety concerns and traction systems. The operating characteristics and applications of several fuel-cell technologies are investigated for FCEVs and FCHEVs. An overview of the fuel cell is provided which serves as the primary source of energy for FCHEVs along with comparisons and its electrochemistry. The study of power transformation topologies communication protocols and enhanced charging techniques for FCHEVs has been studied analytically. Recent technology advancements and the prospects for FCHEVs are discussed in order to influence the future vehicle market and to attain the aim of zero emissions.

This study investigates the feasibility of utilizing surplus hydropower from Ecuador’s major hydroelectric plants to produce green hydrogen a clean energy source that can be used to meet a large percentage of energy needs. Given Ecuador’s significant hydropower infrastructure this approach leverages untapped energy resources for hydrogen production with potential impacts on decarbonization strategies. A Pareto analysis identified five key hydroelectric plants that contribute the most to the national surplus. Using historical data from 2019 to 2023 a stochastic model was applied to estimate future surplus availability through 2030. The findings indicate that although Ecuador’s surplus hydropower peaked in 2021 the general trend shows a decline suggesting an urgent need to capitalize on these resources efficiently. The results indicate a projected annual surplus of hydroelectric energy in Ecuador ranging from 7475 to 3445 GWh over the next five years which could be utilized for green hydrogen production. Ecuador thus has promising potential to become a green hydrogen producer enhancing both regional energy security and carbon reduction goals. The reduction in energy availability for hydrogen production is attributed to the increasing energy demand and variable climatic conditions.

This study presents a techno-economic assessment of power-to-gas and power-to-liquid pathways within the Hydrogen Valley concept to support the decarbonization of local energy systems. Using the EnergyPLAN software both business-as-usual and Hydrogen Valley scenarios were analyzed by varying renewable energy electrolyzer capacity and hydrogen storage. The levelized costs of green hydrogen electrofuels and synthetic natural gas were estimated for both scenarios. A sensitivity analysis was conducted to assess the impact of cost parameters on the levelized costs of hydrogen and alternative fuel production. The findings indicate that the Hydrogen Valley scenario results in a 5.9% increase in total annual costs but achieves a 29.5% reduction in CO2 emissions compared to the business-as-usual scenario. Additionally utilizing excess energy for power-to-gas and power-to-liquid conversion in the Hydrogen Valley scenario lowers the levelized cost of electrofuels from 0.28 €·kWh−1 to 0.21 €·kWh−1 . Similarly the levelized cost of synthetic natural gas decreases from 0.33 €·kWh−1 to 0.25 €·kWh−1 when transitioning from the businessas-usual scenario to the Hydrogen Valley scenario. The results highlight that Hydrogen Valleys enable low-emission energy systems with cost-effective alternative fuels underscoring the tradeoffs between deep decarbonization and cost optimization in the transition to clean energy systems.

Integrating carbon capture and storage (CCS) technology into an integrated energy system (IES) can reduce its carbon emissions and enhance its low-carbon performance. However the full CCS of flue gas displays a strong coupling between lean and rich liquor as carbon dioxide liquid absorbents. Its integration into IESs with a high penetration level of renewables results in insufficient flexibility and renewable curtailment. In addition integrating split-flow CCS of flue gas facilitates a short capture time giving priority to renewable energy. To address these limitations this paper develops a carbon capture utilization and storage (CCUS) method into which storage tanks for lean and rich liquor and a two-stage power-to-gas (P2G) system with multiple utilizations of hydrogen including a fuel cell and a hydrogen-blended CHP unit are introduced. The CCUS is integrated into an IES to build an electricity–heat–hydrogen–gas IES. Accordingly a deep low-carbon economic optimization strategy for this IES which considers stepwise carbon trading coal consumption renewable curtailment penalties and gas purchasing costs is proposed. The effects of CCUS the twostage P2G system and stepwise carbon trading on the performance of this IES are analyzed through a case-comparative analysis. The results show that the proposed method allows for a significant reduction in both carbon emissions and total operational costs. It outperforms the IES without CCUS with an 8.8% cost reduction and a 70.11% reduction in carbon emissions. Compared to the IES integrating full CCS the proposed method yields reductions of 6.5% in costs and 24.7% in emissions. Furthermore the addition of a two-stage P2G system with multiple utilizations of hydrogen further amplifies these benefits cutting costs by 13.97% and emissions by 12.32%. In addition integrating CCUS into IESs enables the full consumption of renewables and expands hydrogen utilization and the renewable consumption proportion in IESs can reach 69.23%.

The transition from fossil fuels to renewable energy sources particularly hydrogen has emerged as a central strategy for decarbonization and the pursuit of net-zero carbon emissions. Meeting the demand for large-scale hydrogen storage a crucial component of the hydrogen supply chain has led to the exploration of underground hydrogen storage as an economically viable solution to global energy needs. In contrast to other subsurface storage options such as salt caverns and aquifers which are geographically limited depleted gas reservoirs have garnered increasing attention due to their broader distribution and higher storage capacity. However the safe storage and cycling of hydrogen in depleted gas reservoirs require the preservation of high stability and integrity in the caprock reservoir and wellbore. Nevertheless there exists a significant gap in the current research concerning storage integrity in underground hydrogen storage within depleted gas reservoirs and a systematic approach is lacking. This paper aims to address this gap by reviewing the primary challenges associated with storage integrity including geochemical reactions microbial activities faults and fractures and perspectives on hydrogen cycling. The study comprehensively reviews the processes and impacts such as abiotic and biotic mineral dissolution/precipitation reactivation and propagation of faults and fractures in caprock and host-rock wellbore instability due to cement degradation and casing corrosion and stress changes during hydrogen cycling. To provide a practical solution a technical screening tool has been developed considering controlling variables risks and consequences affecting storage integrity. Finally this paper highlights knowledge gaps and suggests feasible methods and pathways to mitigate these risks facilitating the development of large-scale underground hydrogen storage in depleted gas reservoirs.

This paper presents a method for estimating Well-to-Wheel (WTW) energy use and greenhouse gas (GHG) emissions attributed to the advanced railway propulsion systems implemented in conjunction with different energy carriers and their production pathways. The analysis encompasses diesel-electric multiple unit vehicles converted to their hybrid-electric plug-in hybrid-electric fuel cell hybrid-electric or battery-electric counterparts combined with biodiesel or hydrotreated vegetable oil (HVO) as the first and second generation biofuels liquefied natural gas (LNG) hydrogen and/or electricity. The method is demonstrated using non-electrified regional railway network with heterogeneous vehicle fleet in the Netherlands as a case. Battery-electric system utilizing green electricity is identified as the only configuration leading to emission-free transport while offering the highest energy use reduction by 65–71% compared to the current diesel-powered hybrid-electric system. When using grey electricity based on the EU2030 production mix these savings are reduced to about 27–39% in WTW energy use and around 68–73% in WTW GHG emissions. Significant reductions in overall energy use and emissions are obtained for the plug-in hybrid-electric concept when combining diesel LNG or waste cooking oil-based HVO with electricity. The remaining configurations that reduce energy use and GHG emissions are hybrid-electric systems running on LNG or HVO from waste cooking oil. The latter led to approximately 88% lower WTW emissions than the baseline for each vehicle type. When produced from natural gas or EU2030-mix-based electrolysis hydrogen negatively affected both aspects irrespective of the prime mover technology. However when produced via green electricity it offers a GHG reduction of approximately 90% for hybrid-electric and fuel cell hybrid-electric configurations with a further reduction of up to 92–93% if combined with green electricity in plug-in hybrid-electric systems. The results indicate that HVO from waste cooking oil could be an effective and instantly implementable transition solution towards carbon–neutral regional trains allowing for a smooth transition and development of supporting infrastructure required for more energy-efficient and environment-friendly technologies.

The steel industry which relies heavily on primary energy is one of the industries with the highest CO2 emissions in China. It is urgent for the industry to identify ways to embark on the path to “green steel”. Hydrogen metallurgy technology uses hydrogen as a reducing agent and its use is an important way to reduce CO2 emissions from long-term steelmaking and ensure the green and sustainable development of the steel industry. Previous research has demonstrated the feasibility and emission reduction effects of hydrogen metallurgy technology; however further research is needed to dynamically analyze the overall impact of the large-scale development of hydrogen metallurgy technology on future CO2 emissions from the steel industry. This article selects the integrated MARKAL-EFOM system (TIMES) model as its analysis model constructs a China steel industry hydrogen metallurgy model (TIMES-CSHM) and analyzes the resulting impact of hydrogen metallurgy technology on CO2 emissions. The results indicate that in the business-as-usual scenario (BAU scenario) applying hydrogen metallurgy technology in the period from 2020 to 2050 is expected to reduce emissions by 203 million tons and make an average 39.85% contribution to reducing the steel industry’s CO2 emissions. In the carbon emission reduction scenario applying hydrogen metallurgy technology in the period from 2020 to 2050 is expected to reduce emissions by 353 million tons contributing an average of 41.32% to steel industry CO2 reduction. This study provides an assessment of how hydrogen metallurgy can reduce CO2 emissions in the steel industry and also provides a reference for the development of hydrogen metallurgy technology.

The imperative to address traditional energy crises and environmental concerns has accelerated the need for energy structure transformation. However the variable nature of renewable energy poses challenges in meeting complex practical energy requirements. To address this issue the construction of a multifunctional large-scale stationary energy storage system is considered an effective solution. This paper critically examines the battery and hydrogen hybrid energy storage systems. Both technologies face limitations hindering them from fully meeting future energy storage needs such as large storage capacity in limited space frequent storage with rapid response and continuous storage without loss. Batteries with their rapid response (90%) excel in frequent short-duration energy storage. However limitations such as a selfdischarge rate (>1%) and capacity loss (~20%) restrict their use for long-duration energy storage. Hydrogen as a potential energy carrier is suitable for large-scale long-duration energy storage due to its high energy density steady state and low loss. Nevertheless it is less efficient for frequent energy storage due to its low storage efficiency (~50%). Ongoing research suggests that a battery and hydrogen hybrid energy storage system could combine the strengths of both technologies to meet the growing demand for large-scale long-duration energy storage. To assess their applied potentials this paper provides a detailed analysis of the research status of both energy storage technologies using proposed key performance indices. Additionally application-oriented future directions and challenges of the battery and hydrogen hybrid energy storage system are outlined from multiple perspectives offering guidance for the development of advanced energy storage systems.

The automotive industry is under increasing pressure to develop cleaner and more efficient technologies in response to stringent emission regulations. Hydrogenpowered internal combustion engines represent a promising alternative offering the potential to reduce carbon-based emissions while improving efficiency. However the accurate estimation of in-cylinder pressure is crucial for optimizing the performance and emissions of these engines. While traditional simulation tools such as GT-POWER are widely utilized for these purposes recent advancements in artificial intelligence provide new opportunities for achieving faster and more accurate predictions. This study presents a comparative evaluation of the predictive capabilities of GT-POWER and an artificial neural network model in estimating in-cylinder pressure with a particular focus on improvements in computational efficiency. Additionally the artificial neural network is employed to predict the equivalent flame radius thereby obviating the need for repeated tests using dedicated high-speed cameras in optical access research engines due to the resource-intensive nature of data acquisition and post-processing. Experiments were conducted on a single-cylinder research engine operating at low-speed and low-load conditions across three distinct relative air–fuel ratio values with a range of ignition timing settings applied for each air excess coefficient. The findings demonstrate that the artificial neural network model surpasses GT-POWER in predicting in-cylinder pressure with higher accuracy achieving an RMSE consistently below 0.44% across various conditions. In comparison GT-POWER exhibits an RMSE ranging from 0.92% to 1.57%. Additionally the neural network effectively estimates the equivalent flame radius maintaining an RMSE of less than 3% ranging from 2.21% to 2.90%. This underscores the potential of artificial neural network-based approaches to not only significantly reduce computational time but also enhance predictive precision. Furthermore this methodology could subsequently be applied to conventional road engines exhibiting characteristics and performance similar to those of a specific optical engine used as the basis for the machine learning analysis offering a practical advantage in real-time diagnostics.

Fuel cell electric vehicles (FCEVs) have received significant attention in recent times due to various advantageous features such as high energy efficiency zero emissions and extended driving range. However FCEVs have some drawbacks including high production costs; limited hydrogen refueling infrastructure; and the complexity of converters controllers and method execution. To address these challenges smart energy management involving appropriate converters controllers intelligent algorithms and optimizations is essential for enhancing the effectiveness of FCEVs towards sustainable transportation. Therefore this paper presents emerging energy management strategies for FCEVs to improve energy efficiency system reliability and overall performance. In this context a comprehensive analytical assessment is conducted to examine several factors including research trends types of publications citation analysis keyword occurrences collaborations influential authors and the countries conducting research in this area. Moreover emerging energy management schemes are investigated with a focus on intelligent algorithms optimization techniques and control strategies highlighting contributions key findings issues and research gaps. Furthermore the state-of-the-art research domains of FCEVs are thoroughly discussed in order to explore various research domains relevant outcomes and existing challenges. Additionally this paper addresses open issues and challenges and offers valuable future research opportunities for advancing FCEVs emphasizing the importance of suitable algorithms controllers and optimization techniques to enhance their performance. The outcomes and key findings of this review will be helpful for researchers and automotive engineers in developing advanced methods control schemes and optimization strategies for FCEVs towards greener transportation.

Optimally scheduling alkaline electrolyzers (AELs) in a hydrogen-based microgrid (HBM) can greatly unleash the operational flexibility of the HBM. However existing scheduling strategies of AELs mostly utilize a simplified AEL model which ignores the nonlinear coupling of electric-hydrogen-thermal sectors violating the AEL’s security constraints thereby making the scheduling scheme infeasible. This paper proposes an improved model predictive control (MPC) based optimal scheduling framework which incorporates a scheduling correction algorithm into the basic MPC structure. This framework is utilized for implementing economic and resilient scheduling of an HBM under normal and emergency conditions respectively. With the scheduling correction algorithm this framework can be formulated into a computationally efficient mixedinteger linear programming meanwhile guaranteeing the solutions strictly satisfy the security constraints of hydrogen facilities (i.e. AEL and hydrogen tank). Case studies are conducted based on real operating data of a Danish energy island Bornholm. The results demonstrate that the proposed scheduling scheme under normal conditions can contribute to significant comprehensive benefits from the daily operation cost saving of 68% computational time saving of 98% and satisfying the security constraints of hydrogen facilities compared to previous scheduling strategies. Besides it sharply reduces load shedding under emergency conditions by proactively allocating distributed energy sources in the HBM.

This paper mainly introduces the main pain point of China's civil hydrogen energy supply chain - the problem of storage and transportation and analyzes the safety economy and scale effect and other issues of the existing hydrogen energy storage and transportation compares with other storage and transportation technology solutions and comprehensively screens out the storage and transportation technology solution mainly based on liquid hydrogen technology. The liquid hydrogen technology solution has significant advantages over the existing compressed hydrogen system in terms of safety economy and scale effect especially for future large-scale hydrogen energy application scenarios. In addition the future hydrogen energy storage and transportation system based on liquid hydrogen technology can help improve the overall utilization efficiency of country’s renewable energy promote the country's energy transition promote the electrification of the country's transportation sector and help achieve China's carbon emission reduction 2030/2060 target.