Publications

Zero-carbon-dioxide-emitting hydrogen-powered aircraft have in recent decades come back on the stage as promising protagonists in the fght against global warming. The main cause for the reduced performance of liquid hydrogen aircraft lays in the fuel storage which demands the use of voluminous and heavy tanks. Literature on the topic shows that the optimal fuel storage solution depends on the aircraft range category but most studies disagree on which solution is optimal for each category. The objective of this research was to identify and compare possible solutions to the integration of the hydrogen fuel containment system on regional short/medium- and large passenger aircraft and to understand why and how the optimal tank integration strategy depends on the aircraft category. This objective was pursued by creating a design and analysis framework for CS-25 aircraft capable of appreciating the efects that diferent combinations of tank structure fuselage diameter tank layout shape venting pressure and pressure control generate at aircraft level. Despite that no large diferences among categories were found the following main observations were made: (1) using an integral tank structure was found to be increasingly more benefcial with increasing aircraft range/size. (2) The use of a forward tank in combination with the aft one appeared to be always benefcial in terms of energy consumption. (3) The increase in fuselage diameter is detrimental especially when an extra aisle is not required and a double-deck cabin is not feasible. (4) Direct venting has when done efciently a small positive efect. (5) The optimal venting pressure varies with the aircraft confguration performance and mission. The impact on performance from sizing the tank for missions longer than the harmonic one was also quantifed.

The storage of excess electrical generation enabled through the electrolytic production of hydrogen from water would allow “load-shifting” of power generation. This paves the way for hydrogen as an energy carrier to be further used as a zero‑carbon fuel for land air and sea transportation. However challenges in hydrogen storage and transportation ultimately pose restrictions on its wider adaption along horizontal and vertical vectors. This paper investigates chemical energy carriers ranging from small molecules such as ammonia and methane to formic acid as well as other more complex hydrocarbons in response to this timely engineering problem. The hydrogenation and dehydrogenation of such carrier molecules require energy lowering the effective net heating value of hydrogen up to 32 %. Different carrier approaches are discussed in the light of availability energetics water requirements and suitability for applications in power generation shipping trucking and aviation supplemented by a comprehensive safety review making this study unique in its field. It is found that hydrogen delivered without a carrier is ideal for power generation applications due to the large quantities required. Aviation would benefit from either ammonia or hydrogen and is generally a field challenging to decarbonize. Ammonia appears also to be a good medium for shipping hydrogen between continents and to power container ships due to its high energy density and lower liquid temperature compared with hydrogen. At the same time ammonia can also be used to power the ship's engine. Long-haul trucking would benefit the most from cryogenic or compressed hydrogen due to the lower quantities required and purity requirements of the fuel cells.

Hydrogen is becoming increasingly important to achieve the valid defossilization goals. However due to its physical properties especially the storage of hydrogen is challenging. One option in this regard are metal hy drides which are able to store hydrogen in chemically material-bound form. Against this background the goal of this paper is an analysis of possible technical application areas of such metal hydrides – both regarding transport and stationary application. These various options are assessed for metal hydrides as well as selected competing hydrogen storage options. The investigation shows that metal hydrides with a temperature range below 100 ◦C (e.g. TiFe) are of interest particularly for transportation applications; possible areas of application include rail and marine transportation as well as selected non-road vehicles. For stationary applications metal hydrides can be used on low and high temperature levels. Here metal hydrides with operating temperatures below 100 ◦C are particularly useful for selected small-scale applications (e.g. home storage systems). For applications with me dium storage capacities (100 kWh to 100 MWh) metal hydrides with higher temperature levels are also conceivable (e.g. NaAlH4). For even higher storage demands metal hydrides are less promising.

The growing demand for air travel in the commercial sector leads to an increase in global emissions whose mitigation entails transitioning from the current fossil-fuel based generation of aircrafts to a cleaner one within a short timeframe. The use of hydrogen and fuel cells has the potential to reach zero emissions in the aerospace sector provided that required innovation and research efforts are substantially accomplished. Development programs investments and new regulations are needed for this technology to be safe and economical. In this context it makes sense to develop a model-based preliminary design methodology for a hybrid regional aircraft assisted by a battery hybridized fuel cell powertrain. The technological assumptions underlying the study refer to both current and expected data for 2035. The major contribution of the proposed methodology is to provide a mathematical tool that considers the interactions between the choice of components in terms of installed power and energy management. This simultaneous study is done because of the availability of versatile control maps. The tool was then deployed to define current and future technological scenarios for fuel cell battery and hydrogen storage systems by quickly adapting control strategies to different sizing criteria and technical specifications. In this way it is possible to facilitate the estimation of the impact of different sizing criteria and technological features at the aircraft level on the onboard electrical system the management of in-flight power the propulsion methods the impact of the masses on consumption and operational characteristics in a typical flight mission. The proposed combination of advanced sizing and energy management strategies allowed meeting mass and volume constraints with state-of-the-art PEM fuel cell and Li-ion battery specifications. Such a solution corresponds to a high degree of hybridization between the fuel cell system and battery pack (i.e. 300 kW and 750 kWh) whereas projected 2035 specs were demonstrated to help reduce mass and volume by 23 % and 40 % respectively.

Because of their high surface areas crystallinity and tunable propertiesmetal−organic frameworks (MOFs) have attracted intense interest as next-generationmaterials for gas capture and storage. While much effort has been devoted to thediscovery of new MOFs a vast catalog of existing MOFs resides within the CambridgeStructural Database (CSD) many of whose gas uptake properties have not beenassessed. Here we employ data mining and automated structure analysis to identify“cleanup” and rapidly predict the hydrogen storage properties of these compounds.Approximately 20 000 candidate compounds were generated from the CSD using analgorithm that removes solvent/guest molecules. These compounds were thencharacterized with respect to their surface area and porosity. Employing the empiricalrelationship between excess H2 uptake and surface area we predict the theoretical total hydrogen storage capacity for the subsetof ∼4000 compounds exhibiting nontrivial internal porosity. Our screening identifies several overlooked compounds having hightheoretical capacities; these compounds are suggested as targets of opportunity for additional experimental characterization.More importantly screening reveals that the relationship between gravimetric and volumetric H2 density is concave downwardwith maximal volumetric performance occurring for surface areas of 3100−4800 m2 /g. We conclude that H2 storage in MOFswill not benefit from further improvements in surface area alone. Rather discovery efforts should aim to achieve moderate massdensities and surface areas simultaneously while ensuring framework stability upon solvent removal.

Traditional high-pressure mechanical compressors account for over half of the car station’s cost have insufficient reliability and are not feasible for a large-scale fuel cell market. An alternative technology employing a two-stage hybrid system based on electrochemical and metal hydride compression technologies represents an excellent alternative to conventional compressors. The high-pressure stage operating at 100–875 bar is based on a metal hydride thermal system. A techno-economic analysis of the metal hydride system is presented and discussed. A model of the metal hydride system was developed integrating a lumped parameter mass and energy balance model with an economic model. A novel metal hydride heat exchanger configuration is also presented based on minichannel heat transfer systems allowing for effective high-pressure compression. Several metal hydrides were analyzed and screened demonstrating that one selected material namely (Ti0.97Zr0.03)1.1Cr1.6Mn0.4 is likely the best candidate material to be employed for high-pressure compressors under the specific conditions. System efficiency and costs were assessed based on the properties of currently available materials at industrial levels. Results show that the system can reach pressures on the order of 875 bar with thermal power provided at approximately 150 ◦C. The system cost is comparable with the current mechanical compressors and can be reduced in several ways as discussed in the paper.

Fuel cells as key carriers for hydrogen energy development and utilization provide a vital opportunity to achieve zero-emission energy use and have thus attracted considerable attention from fundamental research to industrial application levels. Considering the current status of fuel cell technology and the industry this paper presents a systematic elaboration of progress and development trends in fuel cell core components and key materials such as stacks bipolar plates membrane electrodes proton exchange membranes catalysts gas diffusion layers air compressors and hydrogen circulation systems. In addition some proposals for the development of fuel cell vehicles in China are presented based on the analysis of current supporting policies standards and regulations along with manufacturing costs in China. The fuel cell industry of China is still in the budding stage of development and thus suffers some challenges such as lagging fundamental systems imperfect standards and regulations high product costs and uncertain technical safety and stability levels. Therefore to accelerate the development of the hydrogen energy and fuel cell vehicle industry it is an urgent need to establish a complete supporting policy system accelerate technical breakthroughs transformations and applications of key materials and core components and reduce the cost of hydrogen use.

Hydrogen will become a key player in transitioning toward a net-zero energy system. However a clear pathway toward a unified European hydrogen infrastructure to support the rapid scale-up of hydrogen production is still under discussion. This study explores plausible pathways using a fully sector-coupled energy system model. Here we assess the emergence of hydrogen infrastructure build-outs connecting neighboring European nations through hydrogen import and domestic production centers with Western and Central European demands via four distinct hydrogen corridors. We identify a potential lock-in effect of blue hydrogen in the medium term highlighting the risk of longterm dependence on methane. In contrast we show that a self-sufficient Europe relying on domestic green hydrogen by 2050 would increase yearly expenses by around 3% and require 518 gigawatts of electrolysis capacity. This study emphasizes the importance of rapidly scaling up electrolysis capacity building hydrogen networks and storage facilities deploying renewable electricity generation and ensuring coherent coordination across European nations.

Hydrogen is a clean and environmentally friendly energy vector that can play an important role in meeting the world’s futureenergy needs. Therefore a comprehensive study of the potential for hydrogen production from solar energy could greatlyfacilitate the transition to a hydrogen economy. Because by knowing the exact amount of potential for solar hydrogenproduction the cost-effectiveness of its production can be compared with other methods of hydrogen production. Consideringthe above it can be seen that so far no comprehensive study has been done on finding the exact potential of solar hydrogenproduction in different stations of Iran and finding the most suitable station. Therefore in the present work for the first timeusing the HOMER and ArcGIS softwares the technical-economic study of solar hydrogen production at home-scale was done.The results showed that Jask station with a levelized cost of energy equal to $ 0.172 and annual production of 83.8 kg ofhydrogen is the best station and Darab station with a levelized cost of energy equal to $ 0.286 and annual production of 50.4 kgof hydrogen is the worst station. According to the results other suitable stations were Bushehr and Deyr and other unsuitablestations were Anzali and Khalkhal. Also in 102 under study stations 380 MW of solar electricity equivalent to 70.2 tons ofhydrogen was produced annually. Based on the geographic information system map it is clear that the southern half of Iranespecially the coasts of the Persian Gulf and the sea of Oman is suitable for hydrogen production and the northernnortheastern northwestern and one region in southern of Iran are unsuitable for hydrogen production. The authors of thisarticle hope that the results of the present work will help the energy policymakers to create strategic frameworks and a roadmapfor the production of solar hydrogen in Iran.

To achieve carbon neutrality by 2060 decarbonization in the energy sector is crucial. Hydrogen is expected to be vital for achieving the aim of carbon neutrality for two reasons: use of power-to-hydrogen (P2H) can avoid carbon emissions from hydrogen production which is traditionally performed using fossil fuels; Hydrogen from P2H can be stored for long durations in large scales and then delivered as industrial raw material or fed back to the power system depending on the demand. In this study we focus on the analysis and evaluation of hydrogen value in terms of improvement in the flexibility of the energy system particularly that derived from hydrogen storage. An electricity–hydrogen coupled energy model is proposed to realize the hourly-level operation simulation and capacity planning optimization aiming at the lowest cost of energy. Based on this model and considering Northwest China as the region of study the potential of improvement in the flexibility of hydrogen storage is determined through optimization calculations in a series of study cases with various hydrogen demand levels. The results of the quantitative calculations prove that effective hydrogen storage can improve the system flexibility by promoting the energy demand balance over a long term contributing toward reducing the investment cost of both generators and battery storage and thus the total energy cost. This advantage can be further improved when the hydrogen demand rises. However a cost reduction by 20% is required for hydrogen-related technologies to initiate hydrogen storage as long-term energy storage for power systems. This study provides a suggestion and reference for the advancement and planning of hydrogen storage development in regions with rich sources of renewable energy.

Hydrogen is expected to play a key role in the future as a clean energy source that can mitigate global warming. It can also contribute significantly to reducing the imbalance between energy supply and demand posed by deploying renewable energy. However the infrastructure is not ready for the direct use of hydrogen and largescale storage facilities are needed to store the excess hydrogen production. Geological formations particularly salt caverns seem to be a practical option for this large-scale storage as there is already good experience storing hydrocarbons in caverns worldwide. Salt is known to be ductile impermeable and inert to natural gas. Some cases of hydrogen storage in salt caverns in the United States the United Kingdom and Germany reinforce the idea that salt caverns could be a viable option for underground hydrogen storage especially when the challenges and uncertainties associated with hydrogen storage in porous media are considered. However cavern con struction and management can be challenging when salt deposits are not completely pure and mixed with nonsoluble strata. This review summarises the challenges associated with hydrogen storage in salt caverns and suggests some potential mitigation strategies linked to geomechanical and geochemical interactions. The Zechstein salt group in Northern Europe seems to be a feasible geological site for hydrogen storage but the effect of salt impurity particularly at deep offshore sites such as in the Norwegian North Sea should be carefully analysed. It appears that mechanical integrity geochemical reactions hydrogen loss by halophilic bacteria leaching issues and potential hydrogen diffusion are among the major issues when the internal structure of the salt is not pure.

Subsurface porous formations provide large capacities for underground hydrogen storage (UHS). Successful utilization of these porous reservoirs for UHS depends on accurate quantification of the hydrogen transport characteristics at continuum (macro) scale specially in contact with other reservoir fluids. Relative-permeability and capillary-pressure curves are among the macro-scale transport characteristics which play crucial roles in quantification of the storage capacity and efficiency. For a given rock sample these functions can be determined if pore-scale (micro-scale) surface properties specially contact angles are known. For hydrogen/brine/rock system these properties are yet to a large extent unknown. In this study we characterize the contact angles of hydrogen in contact with brine and Bentheimer and Berea sandstones at various pressure temperature and brine salinity using captive-bubble method. The experiments are conducted close to the in-situ conditions which resulted in water-wet intrinsic contact angles about 25 to 45 degrees. Moreover no meaningful correlation was found with changing tested parameters. We monitor the bubbles over time and report the average contact angles with their minimum and maximum variations. Given rock pore structures using the contact angles reported in this study one can define relative-permeability and capillary-pressure functions for reservoir-scale simulations and storage optimization.

Green hydrogen produced from surplus electricity during peak production can be injected into subsurface reservoirs and retrieved during high-demand periods. In this study X-ray tomography was employed to examine hysteresis resulting from repeated hydrogen injection and withdrawal. An unsteady state experiment was performed to evaluate the distribution of hydrogen and brine after drainage and imbibition cycles: images of the pore-space configuration of fluids were taken immediately once injection had stopped and after waiting for a period of 16 h with no flow. A Bentheimer sandstone sample with a length of 60 mm and diameter of 12.8 mm was used and hydrogen was injected at ambient temperature and a pore pressure of 1 MPa. The gas flow rate was decreased from 2 ml/min to 0.08 ml/min over three cycles of gas injection followed by water flooding while the brine injection rate was kept constant. The results showed the presence of capillary pressure hysteresis and hydrogen migration through Ostwald ripening due to the diffusion of gas dissolved in the brine. These phenomena were characterized through analysis of interfacial curvature area connectivity and pore occupancy. The hydrogen tended to reside in the larger pore spaces consistent with water-wet conditions. 16 h after flow had stopped the hydrogen aggregated into larger ganglia with a single large connected ganglion dominating the volume. Moreover the Euler characteristic decreased after 16 h indicating an improvement in connectivity. The work implies that Ostwald ripening – mass transport of dissolved gas – leads to less hysteresis and better connectivity than would be assumed ignoring this effect as done in assessments of hydrocarbon flow and trapping.

Underground hydrogen storage (UHS) in porous media is proposed to balance seasonal fluctuations between demand and supply in an emerging hydrogen economy. Despite increasing focus on the topic worldwide the understanding of hydrogen flow in porous media is still not adequate. In particular relative permeability hys teresis and its impact on the storage performance require detailed investigations due to the cyclic nature of H2 injection and withdrawal. We focus our analysis on reservoir simulation of an offshore aquifer setting where we use history matched relative permeability to study the effect of hysteresis and gas type on the storage efficiency. We find that omission of relative permeability hysteresis overestimates the annual working gas capacity by 34 % and the recovered hydrogen volume by 85 %. The UHS performance is similar to natural gas storage when using hysteretic hydrogen relative permeability. Nitrogen relative permeability can be used to model the UHS when hysteresis is ignored but at the cost of the accuracy of the bottom-hole pressure predictions. Our results advance the understanding of the UHS reservoir modeling approaches.

Implementation of the hydrogen economy for emission reduction will require storage facilitiesand underground hydrogen storage (UHS) in porous media offers a readily available large-scale option. Lack ofstudies on multiphase hydrogen flow in porous media is one of the several barriers for accurate predictions ofUHS. This paper reports for the first time measurements of hysteresis in hydrogen-water relative permeabilityin a sandstone core under shallow storage conditions. We use the steady state technique to measure primarydrainage imbibition and secondary drainage relative permeabilities and extend laboratory measurements withnumerical history matching and capillary pressure measurements to cover the whole mobile saturation range.We observe that gas and water relative permeabilities show strong hysteresis and nitrogen as substitute forhydrogen in laboratory assessments should be used with care. Our results serve as calibrated input to field scalenumerical modeling of hydrogen injection and withdrawal processes during porous media UHS.

We consider a profit-maximizing renewable energy producer operating in a rural area with limited electricity distribution capacity to the grid. While maximizing profits the energy producer is responsible for the electricity supply of a local community that aims to be self-sufficient. Energy storage is required to deal with the energy productions' uncertain and intermittent character. A promising new solution is to use strategic hydrogen reserves. This provides a long-term storage option to deal with seasonal mismatches in energy production and the local community's demand. Using a Markov decision process we provide a model that determines optimal daily decisions on how much energy to store as hydrogen and buy or sell from the power grid. We explicitly consider the seasonality and uncertainty of production demand and electricity prices. We show that ignoring seasonal demand and production patterns is suboptimal and that introducing hydrogen storage transforms loss-making operations into profitable ones. Extensive numerical experiments show that the distribution capacity should not be too small to prevent local grid congestion. A higher storage capacity increases the number of buying actions from the grid thereby causing more congestion which is problematic for the grid operator. We conclude that a profit-maximizing hydrogen storage operation alone is not an alternative to grid expansion to solve congestion which is essential knowledge for policy-makers and grid operators.

Hydrogen and electricity derived from renewable sources present feasible alternative energy options for the decarbonisation of the transportation and power sectors. This study presents the utilisation of hydrogen generated from solar and wind energy resources as a clean fuel for mobility and backup storage for stationary applications under economic and environmental uncertainties. This is achieved by developing a detailed technoeconomic model of an integrated system consisting of a hydrogen refuelling station and an electric power generation system using Mixed Integer Quadratic Constrained Programming (MIQCP) which is further relaxed to Mixed Integer Linear Programming (MILP). The model is implemented in the Advanced Interactive Multidi mensional Modelling Software (AIMMS) and considering the inherent uncertainties in the wind resource solar resource costs and discount rate the total cost of the three configurations (Hybrid PV-Wind Standalone PV and Standalone wind energy system) was minimised using robust optimisation technique and the corresponding optimal sizes of the components levelised cost of energy (LCOE) excess energy greenhouse emission avoided and carbon tax were evaluated. The levelised cost of the deterministic optimisation solution for all the config uration ranges between 0.0702 $/kWh to 0.0786 $/kWh while the levelised cost of the robust optimisation solution ranges between 0.07188 $/kWh to 0.1125 $/kWh. The proposed integration has the advantages of affordable hydrogen and electricity prices minimisation of carbon emissions and grid export of excess energy.

Acceleration of the hydrogen economy is being observed on a global scale. It is considered to be a potential solution to the problems with high-carbon energy industry and transport systems. The potential of production cost-competitiveness and opportunities are currently being investigated to provide insights to policymakers researchers and industry. In this context this study makes a quantitative assessment of the competitiveness of hydrogen storage compared to Li-ion batteries based on price arbitrage in the day-ahead market. Two scenarios that form the boundaries of rational decision-making regarding the charging and discharging of energy storage are considered. The first one assumes the charging and discharging of energy storage facilities over the same hours throughout the entire year. The selection of these hours is based on historical electricity prices. The second scenario assumes charge and discharge during historical daily minimum and maximum prices. The results show that NPV is below zero for both technologies when current values of investment expenditure are assumed. The outcomes of sensitivity analysis indicate that only a substantial reduction of investment expenditure could improve the financial results of the Li-ion batteries (NPV>0). The investigation also shows that even simplified charge and discharge over the same hours allows one to achieve 47% (hydrogen) and 70% (Li-ion batteries) of the maximum operating profit when the perfect foresight of prices is applied. In each case NPV for Li-ion technology is significantly higher than for hydrogen; for example for a 1 MWh and 1 MWout storage system NPV is EUR -4.85 million in the case of hydrogen and with Li-ion NPV is EUR -0.23 million. Consequently the application of expensive decision support systems in small systems may be unprofitable. The increase in profits may not cover the cost of developing and introducing such a system.

T The large-scale implementation of solar hydrogen production requires an optimal combination of photovoltaic systems with suitably-designed electrochemical cells possibly avoiding power electronics for DC-DC conversion to decrease costs. Here a stable solar-driven water splitting system is presented obtained through the direct connection of a state-of-the-art proton exchange membrane (PEM) electrolyzer to a bifacial silicon hetero junction (SHJ) solar module of three cells in series with total area of 730 cm2 . The bifaciality of the solar module has been optimized through modeling in terms of the number of cells module height and inclination. During outdoor operation in the standard monofacial configuration the system is able to produce 3.7 gr of H2 h 1 m 2 with an irradiation of 1000 W m 2 and a solar-to-hydrogen efficiency (STH) of 11.55%. The same system operating in bifacial mode gives rise to a higher H2 flux and STH efficiency reaching values of 4.2 gr of H2 h 1 m 2 and STH of 13.5%. Such a noticeable difference is achieved through the collection of albedo radiation from the ground by the bifacial PV system. The system has been tested outdoors for more than 55 h exhibiting very good endurance with no appreciable change in production and eff

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

The synergy between hydrogen and water is crucial in moving towards a sustainable energy future. This study explores the integration of geothermal energy with desalination and hydrogen production systems to address water and clean energy demands. Two configurations one using multi-effect distillation (MED) and the other reverse osmosis (RO) were designed and compared. Both configurations utilized geothermal energy with MED directly using geothermal heat and RO converting geothermal energy into electricity to power desalination. The systems are evaluated based on various performance indicators including net power output desalinated water production hydrogen production exergy efficiency and levelized costs. Multi-objective optimization using an artificial neural network (ANN) and genetic algorithm (GA) was conducted to identify optimal operational conditions. Results highlighted that the RO-based system demonstrated higher water production efficiency achieving a broader range of optimal solutions and lower levelized costs of water (LCOW) and hydrogen production while the MED-based system offered economic advantages under specific conditions. A case study focused on Canada illustrated the potential benefits of these systems in supporting hydrogen-powered vehicles and residential water needs emphasizing the significant impact of using high-quality desalinated water to enhance the longevity and efficiency of proton exchange membrane electrolyzers (PEME). This research provides valuable insights into the optimal use of geothermal energy for sustainable water and hydrogen production.

This study explores the performance and emissions characteristics of a dual-fuel internal combustion engine operating on a blend of hydrogen and gasoline. This research began with a baseline simulation of a conventional gasoline engine which was subsequently validated through experimental testing on an AVL testbed. The simulation results closely matched the testbed data confirming the accuracy of the model with deviations within 5%. Building on this validated model a hydrogen–gasoline dual-fuel engine simulation was developed. The predictive simulation revealed an approximately 5% increase in overall engine efficiency at the optimal operating point primarily due to hydrogen’s combustion properties. Additionally the injected gasoline mass and CO2 emissions were reduced by around 30% across the RPM range. However the introduction of hydrogen also resulted in a slight reduction (~10%) in torque attributed to the lower volumetric efficiency caused by hydrogen displacing intake air. While CO emissions were significantly reduced NOx emissions nearly doubled due to the higher combustion temperatures associated with hydrogen. This research demonstrates the potential of hydrogen–gasoline dual-fuel systems in reducing carbon emissions while highlighting the need for further optimization to balance performance with environmental impact.

A series of unconfined hydrogen detonation bench-mark experiments are analyzed with respect to CFD code validation and safety measures development. 1-Dimensional in-house code COM1D was applied for validation against experimental data for unconfined detonation of a hemispherical envelope of about 3- and 5-m radius with hydrogen-air mixtures from 20 to 30% hydrogen in air. The code demonstrates a very good agreement with experimental data and allows an adequate simulation of the unconfined hydrogen detonation. All calculated data were scaled in Sachs coordinates to compare with experimental data and to approximate the data for practical evaluation of safety distances. Numerical experiments with different hydrogen inventories from 50 g to 50 kg and different sizes of the cloud from 1 to 2 m radius of the same amount of hydrogen 50g were carried out to clarify the problem of energy of gaseous explosion responsible for the strength of blast wave. Additionally a comparison of hydrogen-air explosion pressure with blast wave properties from the hypothetical cloud of hot compressed combustion products (P=Picc; T=Ticc) and simply a hot air of the same initial pressure and temperature as combustion products showed very good agreement of shock wave strength at far distances beyond the cloud. This confirms the governing role of energy of combustion on blast wave propagation and its ability to scale the strength of blast waves. The dynamics of the explosion process and combustion product expansion were also analyzed experimentally and numerically to evaluate the dimension of the heat radiation zone and heat flux from combustion products. To demonstrate the capability of tested COM1D code the modeling and analysis of high-pressure hydrogen tanks rupture at 350 and 700 bar were conducted to investigate blast wave strength and evaluate the safety distances.

Hydrogen is a versatile energy vector for a plethora of applications; nevertheless its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper recent developments in R&D on waste gasification (municipal solid waste tires plastic waste) are summarised and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock ranging from 15 to 300 g H2/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However regulations like frame conditions or subsidies are necessary to bring the technology into the market.

During the last two decades Gulf Cooperation Council (GCC) countries have seen their population economies and energy production growing steeply with a substantial increase in Gross Domestic Product. As a result of this growth GCC consumption-based carbon dioxide (CO2) emissions increased from 540.79 Metric tons of CO2 equivalent (MtCO2) in 2003 to 1090.93 MtCO2 in 2020. The assumptions and strategies that have driven energy production in the past are now being recast to achieve a more sustainable economic development. The aim of this study is to review and analyze ongoing energy transition strategies that characterize this change to identify challenges and opportunities for bolstering the effectiveness of current strategic orientations. The ensuing analysis shows that since COP26 GCC countries have been pursuing a transition away from carbon-based energy policies largely characterized by the adoption of solar PV with other emerging technologies including energy storage carbon capture and hydrogen generation and storage. While as of 2022 renewable energy adoption in the GCC only represented 0.15 % of global installed capacity GCC countries are making strong efforts to achieve their declared 2030 energy targets that average about 26 % with peaks of 50 % in Saudi Arabia and 30 % in the UAE and Oman. With reference to solar energy plans are afoot to add 42.1 GW of solar photovoltaics and concentrated solar power which will increase 8-fold the current installed renewable capacity (5.1 GW). At the same time oil and gas production rates remain stable and fossil fuel subsidies have grown in the last few years. Also there is a marked preference for the deployment of CCUS and utility-scale solar energy technology vs. distributed solar energy energy efficiency and nature-based solutions. The pursuit of energy transition in the GCC will require increased efforts in the latter and other overlooked strategic endeavors to achieve a more balanced portfolio of sustainable energy solutions with stronger emphasis on energy efficiency (as long as rebound effects are mitigated) and nature-based solutions. Increased efforts are also needed in promoting governance practices aimed to institutionalize regulatory frameworks incentives and cooperation activities that promote the reduction of fossil fuel subsidies and the transition away from fossil fuels.