Search Results (610)

We present the first European intercomparison of primary flow measurement standards with hydrogen-enriched natural gas (up to 20% hydrogen in molar fraction) and natural gas with pressure up to 60 bar and volume flow rates in the range (5 to 160) m³/h. We describe the principles of operation of the primary standards and present the transfer standards, a rotary meter and an ultrasonic meter, used for the intercomparison. In many instances, the overlap between the different laboratories is satisfactory, but the collected results are limited and do not allow us to make advanced conclusions. In addition, we investigate the effect of nitrogen impurities (2% in molar fraction) on the performance of low-pressure gas meters for pure hydrogen using newly developed measurement standards. We present the methods and results of this investigation. We show that nitrogen impurities affect the volume flow measurements of an ultrasonic meter but seem to have little effect on a thermal mass flow meter. This paper explores future opportunities and challenges in international intercomparisons involving hydrogen blends and highlights key issues and solutions with hydrogen gas metering in the presence of impurities. Full article

This paper presents an experimental investigation of hydrogen enrichment effects on combustion behavior and exhaust emissions in a self-developed micro gas turbine fueled with a propane–butane mixture. Hydrogen was blended with the base fuel in volume fractions of 0–30%, and combustion was examined under unloaded operating conditions at three global equivalence ratios (ϕ = 0.7, 1.1, and 1.3). The global equivalence ratio (ϕ) is defined as the ratio of the actual fuel–air ratio to the corresponding stoichiometric fuel–air ratio, with ϕ < 1 representing lean, ϕ = 1 stoichiometric, and ϕ > 1 fuel-rich operating conditions. The micro gas turbine is based on an automotive turbocharger coupled with a custom-designed counterflow combustion chamber developed specifically for alternative gaseous fuel research. Exhaust gas emissions of CO, CO₂, and NO_x were measured using a laboratory-grade FTIR analyzer (Horiba Mexa FTIR Horiba Ltd., Kyoto, Japan), while combustion chamber temperature was monitored with thermocouples. The results show that hydrogen addition significantly influences flame stability, combustion temperature, and emission characteristics. Increasing the hydrogen fraction led to a pronounced reduction in CO emissions across all equivalence ratios, indicating enhanced oxidation kinetics and improved combustion completeness. CO₂ concentrations decreased monotonically with hydrogen enrichment due to the reduced carbon content of the blended fuel and the shift of combustion products toward higher H₂O fractions. In contrast, NO_x emissions increased with increasing hydrogen content for all tested equivalence ratios, which is attributed to elevated local flame temperatures, enhanced reaction rates, and the formation of locally near-stoichiometric zones in the compact combustor. A slight reduction in NO_x at low hydrogen fractions was observed under near-stoichiometric conditions, suggesting a temporary shift toward a more distributed combustion regime. Overall, the findings demonstrate that hydrogen–propane–butane blends can be stably combusted in a micro gas turbine without major operational issues under unloaded conditions. While hydrogen addition offers clear benefits in terms of CO reduction and carbon-related emissions, effective NO_x mitigation strategies will be essential for future high-hydrogen microturbine applications. Full article

Renewable hydrogen has become a versatile technology that can play a key role in the deployment of energy communities, although technological, economic, environmental, legal, and social challenges remain to be addressed. This study conducts a systematic review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) methodology that analyzes the current state of technologies, the different applications, challenges and limitations, and future lines of research related to the enabling role of hydrogen in energy communities. Results from the bibliometric analysis show sustained growth in the number of publications over the last five years (2020–2025), with a predominance of applications in which hydrogen is combined with other energy carriers (58%). The versatility of hydrogen has prompted the evaluation of different applications, with particular emphasis on energy storage to capitalize on energy surpluses (51%), mobility (19%), and heating (20%). The main existing barriers come from the absence of stable long-term regulation, interoperability between components and technologies, and a lack of real data. Overcoming these challenges should be based on new technologies such as artificial intelligence and the construction and operation of pilot projects. In addition, a Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis has been conducted building upon the SHARED-H2 SUDOE project, yielding particularly insightful results through the active involvement of stakeholders in the preparatory process. Based on all the points given above, the research concludes that it is necessary to improve long-term policies and increase training at all levels aimed at active end-user participation and a profound restructuring of the energy system. Full article

To meet stringent efficiency and environmental targets, future gas turbines require increased turbine inlet temperatures while maintaining low NO_x emissions and accommodating hydrogen-blended fuels. Axially staged combustion has emerged as a key technology to address these challenges. This paper presents a mathematical model for the rapid prediction of NO emissions in axially staged combustors fueled with hydrogen-blended methane. The model integrates a simplified thermal NO mechanism with a set of dimensionless staging variables, providing a unified description of flow, mixing, and reaction processes. Its accuracy was validated against a detailed chemical reaction network (CRN). The model was applied to identify feasible low-emission staging windows across different hydrogen-blending ratios and to systematically analyze the effects of secondary-stage mixing quality, operating parameters, and fuel composition on optimal staging and emissions. Results demonstrate that coordinating the combustion strategies of the primary and secondary stages enables effective NO control across a wide fuel range. This work provides a theoretical foundation for the design of low-emission, fuel-flexible axially staged combustors. Full article

In this study, an Integrated Energy System (IES) with hydrogen refinement within a tiered carbon trading mechanism (TCTM) is presented to improve energy efficiency and support decarbonization. To address uncertainties in the IES, a distributionally robust optimization (DRO) approach, employing a fuzzy set framework with Kernel Density Estimation (KDE) to construct error distributions and specify output ranges for renewable energy (RE), is proposed. Latin hypercube sampling (LHS) and K-means clustering are, respectively, applied to generate original and representative scenarios. Subsequently, case studies are performed to evaluate advantages of the presented model. The results indicate that hydrogen refinement within the TCTM framework has substantial benefits for the IES. Specifically, the proposed scenario integrates hydrogen blending combustion (HBC) with synthetic methane, demonstrating significant economic and carbon benefits, with cost reductions of 7.3%, 7.1%, and 4.3% and carbon emission reductions of 6%, 3%, and 2.4% compared to scenarios with no hydrogen utilization, HBC only, and synthetic methane only, respectively. In contrast, to exclude carbon trading and include fixed-price trading, the TCTM achieves a 3.5% and 1.1% reduction in carbon emissions, respectively. Finally, a comprehensive sensitivity analysis is performed, examining factors such as the ratio of hydrogen blending, price, and growth rate of carbon trading. Full article

The increasing penetration of variable renewable energy sources intensifies grid imbalance and challenges the reliability of small-scale power systems. This study addresses these challenges by developing and analyzing a fully integrated hybrid energy system that combines biogas upgrading to biomethane, photovoltaic (PV) generation, hydrogen production via alkaline electrolysis, hydrogen storage, and a gas-steam combined cycle (CCGT). The system is designed to supply uninterrupted electricity to a small municipality of approximately 4500 inhabitants under predominantly self-sufficient operating conditions. The methodology integrates high-resolution, full-year electricity demand and solar resource data with detailed process-based simulations performed using Aspen Plus, Aspen HYSYS, and PVGIS-SARAH3 meteorological inputs. Surplus PV electricity is converted into hydrogen and stored, while upgraded biomethane provides dispatchable backup during periods of low solar availability. The gas-steam combined cycle enables flexible and efficient electricity generation, with hydrogen blending supporting dynamic turbine operation and further reducing fossil fuel dependency. The results indicate that a 10 MW PV installation coupled with a 2.9 MW CCGT unit and a hydrogen storage capacity of 550 kg is sufficient to ensure year-round power balance. During winter months, system operation is sustained entirely by biomethane, while in high-solar periods hydrogen production and storage enhance operational flexibility. Compared to a conventional grid-based electricity supply, the proposed system enables near-complete elimination of operational CO₂ emissions, achieving an annual reduction of approximately 8800 tCO₂, corresponding to a reduction of about 93%. The key novelty of this work lies in the simultaneous and process-level integration of biogas, hydrogen, photovoltaic generation, energy storage, and a gas-steam combined cycle within a single operational framework, an approach that has not been comprehensively addressed in the recent literature. The findings demonstrate that such integrated hybrid systems can provide dispatchable, low-carbon electricity for small communities, offering a scalable pathway toward resilient and decentralized energy systems. Full article

This study presents a quantitative simulation analysis of hydrogen-enriched methane (HENG) storage with nitrogen as the cushion-gas in a depleted gas reservoir by varying three key operational parameters: the injection/withdrawal period, hydrogen blending ratio (5–20%), and injection depth. Ten injection–withdrawal cycles were modeled for each scenario, and performance was evaluated using cycle-averaged and cumulative hydrogen purity, recovery factors, and the mixing zone size. Extending the injection period increased hydrogen purity to 20.00–20.26% and reduced nitrogen to 0.001–0.003%, but recovery decreased from 65.63 to 53.83–41.09% due to enhanced dispersion and residual trapping. The blending ratio was the dominant control: 20% blending yielded 19.9–20.0% purity with nitrogen as low as 0.00–0.03%, whereas 5–10% blending produced lower purity but minimized nitrogen production to 0.97–1.08%. Injection depth affected nitrogen recovery more than purity, increasing from 0.72–1.20% (upper) to 1.46–1.61% (lower), along with thicker mixing zones. Final mixing zone size ranged from 3176 to 5546 blocks, with smaller zones consistently linked to higher purity and lower nitrogen breakthrough. The shut-in period further reduced nitrogen recovery from 6.49 to 1.33% and stabilized mixing behavior. Overall, minimizing late-cycle mixing zone thickness is essential for maintaining HENG storage performance. Although this study provides quantitative insights into HENG operational strategies, the use of a homogeneous grid and simplified fluid properties limits representation of geological heterogeneity and reactive processes. Future work will incorporate heterogeneity and reaction modeling into field-scale simulations to validate and refine these operating strategies for practical deployment. Full article

Hydrogen is widely regarded as a promising clean energy carrier, and blending hydrogen into existing natural gas pipelines is considered a cost-effective and practical pathway for large-scale deployment. Supplying hydrogen-enriched natural gas to buildings requires careful consideration of the safe operation of pipelines and appliances without introducing new risks. In this study, on-site demonstrations and experimental tests were conducted in two high-rise buildings in Weifang to evaluate the impact of hydrogen addition on high-rise building natural gas distribution systems. The results indicate that hydrogen blending up to 20% by volume does not cause stratification in building risers and leads only to a relatively minor increase in additional pressure, approximately 0.56 Pa/m for every 10% increase in hydrogen addition. While hydrogen addition may increase leakage primarily in aging indoor gas systems, gas meter leakage rates under a 10% hydrogen blend remain below 3 mL/h, satisfying safety requirements. In addition, in-service domestic gas alarms remain effective under hydrogen ratios of 0–20%, with average response times of approximately 19–20 s. These findings help clarify the safety performance of hydrogen-blended natural gas in high-rise building distribution systems and provide practical adjustment measures to support future hydrogen injection projects. Full article

This study examines the high-temperature degradation of Hastelloy C276, a corrosion-resistant nickel-based alloy, during exposure to combustion products generated by methane and 99% cracked ammonia. Using a high-pressure optical combustor (HPOC) at 4 bar and exhaust temperatures of 815–860 °C, standard tensile specimens were exposed for five hours to fully developed post-flame exhaust gases, simulating real industrial turbine or burner conditions. The surfaces and subsurface regions of the samples were analysed using scanning electron microscopy (SEM; Zeiss Sigma HD FEG-SEM, Carl Zeiss, Oberkochen, Germany) and energy-dispersive X-ray spectroscopy (EDX; Oxford Instruments X-MaxN detectors, Oxford Instruments, Abingdon, United Kingdom), while mechanical properties were evaluated by tensile testing, and the gas-phase compositions were tracked in detail for each fuel blend. Results show that exposure to methane causes moderate oxidation and some grain boundary carburisation, with localised carbon enrichment detected by high-resolution EDX mapping. In contrast, 99% cracked ammonia resulted in much more aggressive selective oxidation, as evidenced by extensive surface roughening, significant chromium depletion, and higher oxygen incorporation, correlating with increased NO_x in the exhaust gas. Tensile testing reveals that methane exposure causes severe embrittlement (yield strength +41%, elongation −53%) through grain boundary carbide precipitation, while cracked ammonia exposure results in moderate degradation (yield strength +4%, elongation −24%) with fully preserved ultimate tensile strength (870 MPa), despite more aggressive surface oxidation. These counterintuitive findings demonstrate that grain boundary integrity is more critical than surface condition for mechanical reliability. These findings underscore the importance of evaluating material compatibility in low-carbon and hydrogen/ammonia-fuelled combustion systems and establish critical microstructural benchmarks for the anticipated mechanical testing in future work. Full article

Ammonia is considered as a promising hydrogen carrier and a carbon-free fuel. Methods for improving ammonia combustion characteristics often involve its co-firing with more reactive fuels (natural gas, biofuels, etc.). Among the natural gas components, ethane is second most abundant. Therefore, the development of detailed chemical–kinetic mechanisms that accurately consider the interactions between ammonia and each component of natural gas is very important. Such mechanisms must be based on experimental data obtained under a wide range of conditions. In this work, NH₃/C₂H₆/O₂/Ar blends were studied in JSR (φ = 0.5–2.0, p = 1 atm, τ = 1 s, T = 800–1300 K) and in a shock tube (p = 7.3–8.6 atm, T = 1260–1590 K). Additionally, the structure of premixed flames was investigated (φ = 0.8–1.2, p = 1–5 atm). Eleven recently published detailed chemical–kinetic mechanisms were tested. The model Shrestha-2025 was updated to achieve better agreement with the entire set of experimental data. The effect of p and φ on intermediate species concentration was analyzed. Ammonia and ethane consumption pathways were also examined. Full article

Active packages have become a significant center of attention, and especially those based on biodegradable materials, due to their ability to enhance food preservation and extend shelf life. A suitable base for obtaining such types of packages has turned out to be polymers with natural origin, such as hydroxylpropyl methylcellulose (HPMC) and zein. Therefore, the present study is focused on developing films using the casting method based on pure HPMC and blends between HPMC and zein. Three types of polymer matrices were developed: pure HPMC film, HPMC 3:1 zein, and HPMC 1:1 zein. Further, all of them were loaded with curcumin to improve their biological activity, and mainly their antioxidant activity. In order to investigate the potential of these films, some of their most vital properties in terms of potential application as packaging material are established, such as mechanical properties (strain at break, Young’s modulus), barrier properties (water vapor transmission rate), and morphology. A significant change in the Young’s modulus was present after the addition of zein; it went from 276.98 ± 28.48 MPa for pure HPMC to 52.17 ± 10.19 MPa in a 1:1 ratio between the polymers. Meanwhile, strain at break showed a slight drop from 86.74 ± 8.64% to 72.44 ± 9.62%. Barrier properties were also influenced by the formation of composite film and the addition of polyphenol, lowering the water vapor transmission rate from 913.07 ± 74.01 g/m².24 h for pure HPMC to 873.05 ± 9.07 g/m².24 h for 1:1 ratio film and further to 826.35 ± 33.67 g/m².24 h after the addition of rutin to the latter. Additional characterization of radical scavenging ability towards DPPH free radicals showed a similar A-shaped trend to the values of Young’s modulus, due to the presence of hydrogen bonds, which affect both properties of the film structures. Thermal behavior and phase state investigation of the films obtained by differential scanning calorimetry prior to and after polyphenol addition was carried out, indicating full phase transition of rutin from crystalline to amorphous state. Full article

In the steel industry, reheating furnaces are a significant source of carbon emissions. Co-firing natural gas and ammonia in reheating furnaces reduces carbon emissions and mitigates ignition difficulties and the limited flammability range of ammonia. This research develops a three-dimensional model for combustion, fluid dynamics, and heat transfer in a reheating furnace to investigate slab heating and emission with a natural gas/ammonia blended fuel. Numerical results demonstrate that, under constant calorific value conditions, the average temperature of the discharged slab decreases following ammonia blending, with the greatest temperature differential of 110 K achieved at a 10% ammonia blending ratio. Moreover, as the ammonia blending ratio increases from 0 to 40%, the mass fraction of CO first rises and subsequently declines, ultimately decreasing by 18%. Meanwhile, the CO₂ emissions at the outlet decrease by 17.6% to 40.7%. The mass fraction of unburned NH₃ rises to 0.0271, whilst NO_x emissions diminish from 49.47 ppm to 14.23 ppm. These changes are attributed to the low combustion efficiency and burning rate of ammonia, coupled with the reduced furnace temperature during ammonia-blended combustion, which weakens radiative heat transfer. Thus, optimizing the equivalence ratio along with applying hydrogen can improve the thermal efficiency of the reheating furnace. This study provides insight into the operational characteristics of a full-scale walking-beam reheating furnace operating under natural gas-ammonia co-firing conditions, providing theoretical guidance for enhancing the thermal efficiency of furnaces. Full article

Developing cost-effective and durable electrocatalysts is essential for advancing anion exchange membrane fuel cells (AEMFCs). This work evaluates Pd-based catalysts supported on β-MnO₂, Vulcan carbon (C), and their physical blend (Pd/MnO₂:Pd/C) as bifunctional electrodes for the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR). The catalysts were synthesized via chemical reduction and characterized by TGA, ICP-OES, TEM, BET, and XRD. Rotating disk electrode studies revealed that the hybrid exhibited superior activity and kinetics, with lower Tafel slopes and higher exchange current densities compared to the individual supports. In AEMFCs, the hybrid reached 128.0 mW cm⁻² as a cathode and 221.7 mW cm⁻² as an anode, outperforming individual components. This enhanced performance arises from the synergistic interaction between Pd nanoparticles and MnO₂, where MnO₂ modulates the catalyst’s microstructure and local reaction environment while the carbon phase ensures efficient electron transport. MnO₂, although inactive for the HOR alone, acted as a structural spacer, enhancing mass transport and stability. Durability tests confirmed that the hybrid electrocatalyst retained over 99% of its initial activity after 3000 cycles. These results highlight the hybrid Pd/MnO₂:Pd/C as a promising, bifunctional, and durable electrocatalyst for AEMFC applications. Full article

Recent progress in hydrogen combustion indicates that hydrogen could partially or fully replace traditional fuels in power plants, but maintaining stable flames remains a major challenge for many combustion systems. This study presents the effect of hydrogen enrichment of Liquid Petroleum Gas (LPG) on the low-swirl flame structure and flame temperature at different hydrogen mass fractions and equivalence ratios (φ = 0.501 and 1.04). The experimental observations for low-swirl flames under various conditions, including the effect of increasing hydrogen enrichment from 0% to ~20%, were discussed. Experiments were performed using a swirl burner, flame photography, and temperature measurements to evaluate the dynamic swirl flame, stability, and flame temperature distribution. The results show that moderate hydrogen enrichment (5–15%) improves flame stability and delays blow-off. In contrast, very high hydrogen concentrations may destabilize the flame due to higher reactivity and enhanced sensitivity to flow perturbations. Also, hydrogen enrichment up to ~20% enhances flame compactness, intensifies heat release, and reduces oscillatory instability without triggering blow-off or flashback, making hydrogen blending a promising strategy for stabilizing swirl flames at rich operating conditions. Finally, hydrogen enrichment consistently increases swirl flame temperature at both equivalence ratios. Full article

The electricity–hydrogen–electricity conversion chain offers an effective solution for integrating clean energy into the grid while addressing multiple grid control requirements. Moreover, multiregional, interconnected, and integrated energy systems (IESs) can significantly increase overall energy utilization efficiency and operational flexibility through spatiotemporal coordination among diverse energy sources. However, few researchers have considered these two aspects in a unified framework. To address this gap, a low-carbon economic dispatch model and control strategy for a multiregional hydrogen-blended IES are proposed in this work. The model is constructed based on a system architecture that incorporates electricity–hydrogen–electricity conversion links while accounting for source–load uncertainties and peak shaving requirements. We solve the resulting distributed nonconvex nonlinear optimization problem using the alternating direction method of multipliers (ADMM). Furthermore, we analyze how uncertainty factors and peak shaving needs affect the maximum allowable hydrogen blending ratio in the gas grid, as well as the corresponding dynamic blending strategy. Our findings demonstrate that the proposed multiregional hydrogen-blended integrated energy system, with dynamic hydrogen blending control, significantly enhances the capacity for clean energy integration and reduces carbon emissions by approximately 12.3%. The peak-shaving demand is addressed through a coordinated mechanism involving electrolyzers (ELs), gas turbines (GTs), and hydrogen fuel cells (HFCs). This coordinated mechanism enables hydrogen fuel cells to double their output during peak hours, while electrolyzers increase their power consumption by approximately 730 MW during off-peak hours. The proposed dispatch model employs conditional risk measures to quantify the impacts of uncertainty and uses economic coefficients to balance various cost components. This approach enables effective coordination among economic objectives, risk management, and system performance (including peak shaving capability), thereby improving the practical applicability of the model. Full article