Transmission, Distribution & Storage

The cooling effect from the para-ortho hydrogen conversion (POC) combined with a vaporcooled shield (VCS) and multi-layer insulation (MLI) can effectively extend the storage duration of liquid hydrogen in cryogenic tanks. However there is currently no effective and straightforward empirical correlation available for predicting the catalytic POC efficiency in VCS pipelines. This study focuses on the development of correlations for the catalytic conversion of para-hydrogen to ortho-hydrogen in pipelines particularly in the context of cryogenic hydrogen storage systems. A model that incorporates the Langmuir adsorption characteristics of catalysts and introduces the concept of conversion efficiency to quantify the catalytic process’s performance is introduced. Experimental data were obtained in the temperature range of 141.9~229.9 K from a cryogenic hydrogen catalytic conversion facility where the effects of temperature pressure and flow rate on the catalytic conversion efficiency were analyzed. Based on a validation against the experimental data the proposed model offers a reliable method for predicting the cooling effects and optimizing the catalytic conversion process in VCS pipelines which may contribute to the improvement of liquid hydrogen storage systems enhancing both the efficiency and duration of storage.

This study investigated the hydrogen embrittlement behavior of 304 stainless steel under the combined condition of sensitization and hydrogen pre-charging. Specifically hydrogen trapping analysis and martensite transformation mapping were used to examine the respective roles of carbide precipitation and chromium depletion and key factors were identified through fractographic observations. Sensitization was simulated at 650 ◦C for 50 h followed by hydrogen pre-charging at 250 ◦C under 50 MPa for 3.5 days. Under hydrogen pre-charging sensitized specimens showed a 9.3 % drop in ultimate tensile strength a 17.3 % reduction in elongation and a 16 % decrease in relative reduction of area indicating higher hydrogen embrittlement susceptibility. Hydrogen desorption analysis revealed a redistribution of hydrogen from reversible to irreversible traps consistent with 139 nm coarsened Cr23C6 carbides while phase mapping revealed extensive formation of strain-induced martensite along grain boundaries and within grains. These martensitic regions accelerated hydrogen transport and promoted strain localization leading to the disappearance of intragranular dimples and the development of intergranular cracking. The results demonstrate that strain-induced martensite formed in chromiumdepleted regions is the dominant factor governing post-sensitization hydrogen embrittlement emphasizing the necessity of controlling chromium depletion to maintain the stability of the austenitic matrix in hydrogen environments.

As a key zero-carbon energy carrier the accurate measurement of liquid hydrogen flow in its industrial chain is crucial. However the ultra-low temperature ultra-low density and other properties of liquid hydrogen can introduce calibration errors. To enhance the measurement accuracy and reliability of liquid hydrogen flow this study investigates the heat and mass transfer within a 1 m3 non-vented storage tank during the calibration process of a liquid hydrogen flow standard device that integrates combined dynamic and static gravimetric methods. The vertical tank configuration was selected to minimize the vapor–liquid interface area thereby suppressing boil-off gas generation and enhancing pressure stability which is critical for measurement accuracy. Building upon research on cryogenic flow standard devices as well as tank experiments and simulations this study employs computational fluid dynamics (CFD) with Fluent 2024 software to numerically simulate liquid hydrogen flow within a non-vented tank. The thermophysical properties of hydrogen crucial for the accuracy of the phase-change simulation were implemented using high-fidelity real-fluid data from the NIST Standard Reference Database as the ideal gas law is invalid under the cryogenic conditions studied. Specifically the Lee model was enhanced via User-Defined Functions (UDFs) to accurately simulate the key phasechange processes involving coupled flash evaporation and condensation during liquid hydrogen refueling. The simulation results demonstrated good agreement with NASA experimental data. This study systematically examined the effects of key parameters including inlet flow conditions and inlet liquid temperature on the flow characteristics of liquid hydrogen entering the tank and the subsequent heat and mass transfer behavior within the tank. The results indicated that an increase in mass flow rate elevates tank pressure and reduces filling time. Conversely a decrease in the inlet liquid hydrogen temperature significantly intensifies heat and mass transfer during the initial refueling stage. These findings provide important theoretical support for a deeper understanding of the complex physical mechanisms of liquid hydrogen flow calibration in non-vented tanks and for optimizing calibration accuracy.

The development of efficient and sustainable hydrogen storage materials is a key challenge for realizing hydrogen as a clean and flexible energy carrier. Among various options metal hydrides offer high volumetric storage density and operational safety yet their application is limited by thermodynamic kinetic and compositional constraints. In this work we investigate the potential of machine learning (ML) to predict key thermodynamic properties—equilibrium plateau pressure enthalpy and entropy of hydride formation—based solely on alloy composition using Magpie-generated descriptors. We significantly expand an existing experimental dataset from ~400 to 806 entries and assess the impact of dataset size and data augmentation using the PADRE algorithm on model performance. Models including Support Vector Machines and Gradient Boosted Random Forests were trained and optimized via grid search and cross-validation. Results show a marked improvement in predictive accuracy with increased dataset size while data augmentation benefits are limited to smaller datasets and do not improve accuracy in underrepresented pressure regimes. Furthermore clustering and cross-validation analyses highlight the limited generalizability of models across different material classes though high accuracy is achieved when training and testing within a single hydride family (e.g. AB2). The study demonstrates the viability and limitations of ML for accelerating hydride discovery emphasizing the importance of dataset diversity and representation for robust property prediction.

A thermodynamic modeling framework is introduced to describe hydrogen refueling station configurations and capture detailed thermal dynamics in vehicle tanks with large aspect ratios. With an aspect ratio larger than three axial discretization of temperature allows to recover accurate temperature profiles and show that the gas and liner temperature are always highest towards the rear of the tanks. The framework is validated against experimental data and used to investigate the internal heat transfer dynamics. As aspect ratio grows larger the amount of cooling received by the rear region decreases as the incoming turbulent jet does not reach the latter. The current thermal management strategy of pre-cooling is therefore limited showing marginal improvements even with a cooling temperature of -50 ◦C. Potential solutions are to increase the filling duration time or to carefully design the tank with higher thermal diffusivity and adequate external means of cooling.

This study investigates hydrogen storage enhancement through adsorption in porous materials by coupling the Dubinin–Astakhov (D-A) adsorption model with H2 conservation equations (mass momentum and energy). The resulting system of partial differential equations (PDEs) was solved numerically using the finite element method (FEM). Experimental work using activated carbon as an adsorbent was carried out to validate the model. The comparison showed good agreement in terms of temperature distribution average pressure of the system and the amount of adsorbed hydrogen (H2). Further simulations with different adsorbents indicated that compact metal–organic framework 5 (MOF-5) is the most effective material in terms of H2 adsorption. Additionally the pair (273 K 800 s) remains the optimal combination of injection temperature and time. The findings underscore the prospective advantages of optimized MOF-5-based systems for enhanced hydrogen storage. These systems offer increased capacity and safety compared to traditional adsorbents. Subsequent research should investigate multi-objective optimization of material properties and system geometry along with evaluating dynamic cycling performance in practical operating conditions. Additionally experimental validation on MOF-5-based storage prototypes would further reinforce the model’s predictive capabilities for industrial applications.

The Yangtze River as the world’s largest clean energy corridor links key economic regions and plays a crucial role in inland waterway transportation. However few studies have comprehensively evaluated the potential of the Yangtze River for cross-regional hydrogen transport. Here we develop a comprehensive integrated power and hydrogen supply chain (IPHSC) optimization model to evaluate the potential of cross-regional hydrogen transport via the Yangtze River. The IPHSC optimization model covers the entire hydrogen production-storage-transportation-utilization chain through cross-sector modeling of energy transportation water scheduling and environmental protection. Results show that in the 2060 carbon neutrality scenario the deployment of 62.2 kilotons of 574 differentiated liquid hydrogen (LH2) carrier ships could enable the transportation of 5018 kilotons (1512 million ton-km) of hydrogen annually meeting nearly 20% of the total electrolytic hydrogen demand across eight riverine provinces. Unlike west-to-east electricity transmission in China the central Yangtze River region is expected to become the main hub for hydrogen exports in the future. Compared with alternative methods such as transmission lines or pipelines LH2 carrier ships offer the lowest energy supply costs at 3 US cents/kWh for electricity and 5 US cents/kWh for hydrogen. Additionally a full-parameter attribution analysis of over 40 factors is conducted to assess variations in supply costs. Our study offers a thorough evaluation of the feasibility and economic benefits of hydrogen transportation via inland waterways providing a comprehensive multi-sectoral coupling assessment framework for regions with well-established inland waterway networks such as Europe and the United States.