Italy

Underground hydrogen storage (UHS) in depleted oil and gas fields is pivotal for balancing large-scale renewable-energy systems yet the wettability of reservoir rocks in contact with hydrogen after decades of Enhanced Oil Recovery (EOR) operations remains poorly quantified. This work experimentally investigates how two common EOR legacies cationic surfactant (city-trimethyl-ammonium bromide CTAB) and supercritical carbon dioxide (SC–CO2) flooding alter rock–water–Hydrogen (H2) wettability in carbonate formations. Contact angles were measured on dolomite and limestone rock slabs at 30–75 ◦C and 3.4–17.2 MPa using a high-pressure captive-bubble cell. Crude-oil aging shifted clean dolomite from strongly water-wet (θ ~ 28–29◦) to intermediate-wet (θ ≈ 84◦). Subsequent immersion in dilute CTAB solutions (0.5–2 wt %) fully reversed this effect restoring or surpassing the original water-wetness (θ ≈ 21–28◦). Limestone samples exposed to SC-CO2 at 60–80 ◦C became more hydrophilic (θ ≈ 18–30◦) relative to untreated controls; moderate carbonate dissolution (≤6 × 103 ppm Ca2+) produced the most significant improvement in water-wetness whereas severe dissolution yielded diminishing returns. These findings show that many mature reservoirs are already water-wet (post-CO2) or can be easily re-wetted (via residual CTAB). Across all scenarios sample wettability showed little sensitivity to pressure but higher temperature consistently promoted stronger water-wetness. Future work should include dynamic core-flooding experiments with realistic reservoir.

In this paper developed in the context of the Clean Sky 2 project SIENA (Scalability Investigation of hybrid-Electric concepts for Next-generation Aircraft) an extensive analysis is carried out to identify and accelerate the development of innovative propulsion technologies and architectures that can be scaled across five aircraft categories from small General Aviation airplanes to long-range airliners. The assessed propulsive architectures consider various components such as batteries and fuel cells to provide electricity as well as electric motors and jet engines to provide thrust combined to find feasible aircraft architectures that satisfy certification constraints and deliver the required performance. The results provide a comprehensive analysis of the impact of key technology performance indicators on aircraft performance. They also highlight technology switching points as well as the potential for scaling up technologies from smaller to larger aircraft based on different hypotheses and assumptions concerning the upcoming technological advancements of components crucial for the decarbonization of aviation. Given the considered scenarios the common denominator of the obtained results is hydrogen as the main energy source. The presented work shows that for the underlying models and technology assumptions hydrogen can be efficiently used by fuel cells for propulsive and system power for smaller aircraft (General Aviation commuter and regional) typically driven by propellers. For short- to long-range jet aircraft direct combustion of hydrogen combined with a fuel cell to power the on-board subsystems appears favorable. The results are obtained for two different temporal scenarios 2030 and 2050 and are assessed using Payload-Range Energy Efficiency as the key performance indicator. Naturally introducing such innovative architectures will face a lack of applicable regulation which could hamper a smooth entry into service. These regulatory gaps are assessed detailing the level of maturity in current regulations for the different technologies and aircraft categories.

Hydrogen is considered a key alternative to fossil fuels in the broader context of ecological transition. Repurposing natural gas pipelines for hydrogen transport is one of the challenges of this approach. However hydrogen can diffuse into metallic lattices leading to hydrogen embrittlement (HE). For this reason typically ductile materials can experience unexpected brittle fractures and it is therefore necessary to assess the HE propensity of the current pipeline network to ensure its fitness for hydrogen transport. This study examines the relationship between the microstructure of the circumferential weld joint in X52 pipeline steel and hydrogen concentration introduced electrolytically. Base material heat affected zone and fused zone were subjected to 1800 3600 7200 and 14400 s of continuous charging with a current density J = − 10 mA/cm2 in an acid solution. Results showed that the fusion zone absorbed the most hydrogen across all charging times while the base material absorbed more hydrogen than the heat-affected zone due to the presence of non-metallic inclusions. Fracture toughness was assessed using single edge notch tension specimens (SENT) in air and electrolytic hydrogen. Results indicate that the base material is particularly vulnerable to hydrogen environments exhibiting the greatest reduction in toughness when exposed to hydrogen compared to air.

Hydrogen-based technologies prominently fuel cells are emerging as strategic solutions for decarbonization. They offer an efficient and clean alternative to fossil fuels for electricity generation making a tangible contribution to the European Green Deal climate objectives. The primary issue is the production and transportation of hydrogen. An on-site hydrogen production system that includes CO2 capture could be a viable solution. The proposed power system integrates an internal combustion engine (ICE) with a steam methane reformer (SMR) equipped with a CO2 capture and energy storage system to produce “blue hydrogen”. The hydrogen fuels a high-temperature polymer electrolyte membrane (HTPEM) fuel cell. A battery pack incorporated into the system manages rapid fluctuations in electrical load ensuring stability and continuity of supply and enabling the fuel cell to operate at a fixed point under nominal conditions. This hybrid system utilizes natural gas as its primary source reducing climate-altering emissions and representing an efficient and sustainable solution. The simulation was conducted in two distinct environments: Thermoflex code for the integration of the engine reformer and CO2 capture system; and Matlab/Simulink for fuel cell and battery pack sizing and dynamic system behavior analysis in response to user-demanded load variations with particular attention to energy flow management within the simulated electrical grid. The main results show an overall efficiency of the power system of 39.9% with a 33.5% reduction in CO2 emissions compared to traditional systems based solely on internal combustion engines.

This study explores the design and feasibility of a novel fuel cell-powered wind farm for residential electricity hydrogen/oxygen production and cooling/heating via a compression chiller. Wind turbine energy powers Proton Exchange Membrane (PEM) electrolyzers and a compression chiller unit. The proposed system was modeled using EES thermodynamic software and its economic viability was assessed. A case study across seven Italian regions with varying wind potentials evaluated the system’s feasibility in diverse weather conditions. Multi-objective optimization using Response Surface Methodology (RSM) determined the number of wind turbines as optimum number of electrolyzers & fuel cell units. Optimization results indicated that 37 wind turbines 1 fuel cell unit and 2 electrolyzer units yielded an exergy efficiency of 27.98 % and a cost rate of 619.9 $/h. TOPSIS analysis suggested 32 wind turbines 2 electrolyzers and 2 reverse osmosis units as an alternative configuration. Further twelve different scenarios were examined to enhance the distribution of wind farmgenerated electricity among the grid electrolyzers and reverse osmosis systems. revealing that directing 25 % to reverse osmosis 20 % to electrolyzers and 55 % to grid sales was optimal. Performance analysis across seven Italian cities (Turin Bologna Florence Palermo Genoa Milan and Rome) identified Genoa Palermo and Bologna as the most suitable locations due to favorable wind conditions. Implementing the system in Genoa the optimal site could produce 28435 MWh of electricity annually prevent 5801 tons of CO2 emissions (equivalent to 139218 $). Moreover selling this clean electricity to the grid could meet the annual clean electricity needs of approximately 5770 people in Italy

This study aimed to investigate the effectiveness of dark fermentation in biohydrogen production from agro-industrial wastes including apple pomace brewer’s grains molasses and potato powder subjected to different pretreatment methods. The experiments were conducted at a laboratory scale using 1000 cm3 anaerobic reactors at a temperature of 35 ◦C and anaerobic sludge as the inoculum. The highest yield of hydrogen was obtained from pre-treated apple pomace (101 cm3/g VS). Molasses a less complex substrate compared to the other raw materials produced 25% more hydrogen yield following pretreatment. Methanogens are sensitive to high temperatures and low-pH conditions. Nevertheless methane constituted 1–6% of the total biogas under these conditions. The key factor was appropriate treatment of the inoculum to limit competition from methanogens. Increasing the inoculum dose from 150 cm3/dm3 to 250 cm3/dm3 had no further effect on biogas production. The physicochemical parameters and VFA data confirmed the stability and usefulness of activated sludge as a source of microbial cultures for H2 production via dark fermentation.

From an environmental standpoint carbon-free energy carriers such as ammonia and hydrogen are essential for future energy systems. However their hightemperature chemical behavior remains insufficiently understood posing challenges for the development and optimization of advanced combustion technologies. Ammonia in particular is globally available and cost-effective especially for energy-intensive industries. The addition of ammonia or hydrogen to methane significantly reduces the accuracy of existing predictive models. Therefore validated and detailed data are urgently needed to enable reliable design and performance predictions. This review highlights the compatibility of ammonia with existing combustion infrastructure facilitating a smoother transition to more sustainable heating methods without the need for entirely new systems. Applications in high-temperature heating processes such as metal processing ceramics and glass production and power generation are of particular interest. This review focuses on the systematic assessment of alternative fuel mixtures comprising ammonia and hydrogen as well as natural gas with particular consideration of existing safety-related parameters and combustion characteristics. Fundamental quantities such as the laminar burning velocity are discussed in the context of their relevance for fuel mixtures and their scalability toward turbulent flame propagation which is of critical importance for industrial burner and reactor design. The influence of fuel composition on ignition limits is examined as these are essential parameters for safety margin definitions and operational boundary conditions. Furthermore flame stability in mixed-fuel systems is addressed to evaluate the practical feasibility and robustness of combustion under varying process conditions. A detailed overview of current diagnostic and analysis methods follows encompassing both pollutant measurement techniques and the detection of key radical species. These diagnostics form the experimental basis for reaction kinetics modeling and mechanism validation. Given the importance of emission formation in combustion systems a dedicated subsection summarizes major emission trends even though a comprehensive treatment would exceed the scope of this review. Thermal radiation effects which are highly relevant for heat transfer and system efficiency in large-scale applications are then reviewed. In parallel current developments in numerical simulation approaches for industrial-scale combustion systems are presented including aspects of model accuracy boundary conditions and computational efficiency. The review also incorporates insights from materials engineering particularly regarding high-temperature material performance corrosion resistance and compatibility with combustion products. Based on these interdisciplinary findings operational strategies for high-temperature furnaces are outlined and selected industrial reference systems are briefly presented. This integrated approach aims to support the design optimization and safe operation of next-generation combustion technologies utilizing carbon-free or low-carbon fuels.

Underground Hydrogen Storage (UHS) is a promising solution to maximize the use of hydrogen as an energy carrier. This study presents a standardized methodology for assessing UHS quality by introducing the Underground Hydrogen Storage Suitability Index (UHSSI) which integrates three sub-indices: the Caprock Potential Index (CPI) the Reservoir Quality Index (RQI) and the Site Potential Index (SPI). Parameters such as porosity permeability lithology caprock thickness depth temperature and salinity are evaluated and ranked from 0 (unsuitable) to 5 (excellent). The methodology was validated using data from six worldwide sites including salt caverns and aquifers. Sites like Moss Bluff Clemens Dome and Spindletop (USA) scored highly while Teesside (UK) Lobodice (Czech Republic) and Beynes (France) were classified as unsuitable due to shallow depths and microbial activity. A software tool the UHSSI Calculator was developed to automate site evaluations. This approach offers a cost-effective tool for preliminary screening and supports the safer development of UHS.

This paper explores cleaner and techno-economically viable solutions to provide electricity heat and cooling using green hydrogen (H2) and green ammonia (NH3) across the entire decarbonized value chain. We propose integrating a 100% hydrogen-fueled internal combustion engine (e.g. Jenbacher JMS 420) as a stationary backup solution and comparing its performance with other backup technologies. While electrochemical storage systems or battery energy storage systems (BESSs) offer fast and reliable short-term energy buffering they lack flexibility in relocation and typically involve higher costs for extended backup durations. Through five case studies we highlight that renewable-based energy supply requires additional capacity to bridge longer periods of undersupply. Our results indicate that for cost reasons battery–electric solutions alone are not economically feasible for longterm backup. Instead a more effective system combines both battery and hydrogen storage where batteries address daily fluctuations and hydrogen engines handle seasonal surpluses. Despite lower overall efficiency gas engines offer favorable investment and operating costs in backup applications with low annual operating hours. Furthermore the inherent fuel flexibility of combustion engines eventually will allow green ammonia-based backup systems particularly as advancements in small-scale thermal cracking become commercially available. Future studies will address CO2 credit recognition carbon taxes and regulatory constraints in developing more effective dispatch and master-planning solutions.

The ongoing digitalization of energy infrastructure is a crucial enabler for improving efficiency reliability and sustainability in gas distribution networks especially in the context of decarbonization and the integration of alternative energy carriers (e.g. renewable gases including biogas green hydrogen). This study presents the development and application of a Digital Twin framework for a real-world gas distribution network developed using open-source tools. The proposed methodology covers the entire digital lifecycle: from data acquisition through smart meters and GIS mapping to 3D modelling and simulation using tools such as QGIS FreeCAD and GasNetSim. Consumption data are collected processed and harmonized via Python-based workflows hourly simulations of network operation including pressure flow rate and gas quality indicators like the Wobbe Index. Results demonstrate the effectiveness of the Digital Twin in accurately replicating real network behavior and supporting scenario analyses for the introduction of greener energy vectors such as hydrogen or biomethane. The case study highlights the flexibility and transparency of the workflow as well as the critical importance of data quality and availability. The framework provides a robust basis for advanced network management optimization and planning offering practical tools to support the energy transition in the gas sector.