Hydrogen Vessels Research Articles

Qualification and Indexation of Mechanoluminescent (ML) Sensors Toward Crack Monitoring and Visualizing Strain Distribution

Mechanoluminescent (ML) sensing material is a fascinating ceramic powder (size: av.1 μm, representative ML material: SrAl2O4:Eu2+, lem: 520 nm) and it emits intensive light repeatedly with various type of mechanical stress. The ML luminance is proportional to strain energy. Thus, the two-dimensional (2D) ML emission pattern reflects the dynamical strain/stress distribution.So far, ML visual sensors has been successfully applied for visualizing crack and mechanical behavior for (1) structural health monitoring (SHM) on infrastructure such as bridge, building, pipe, and hydrogen vessel [1, 2], (2) design and simulation supporting on light-weighting of automobile and airplane [1, 2], and (3) evaluation assisting tools of mechanical testing especially in adhesive joint [3]. In these cases, we have used our synthesized high performance SrAl2O4:Eu2+ as ML material and epoxy resin as matrix pf paint for preparing ML sensors. However, recently, along the big achievements of the ML sensing as above, novel ML sensing material has vigorously investigated and reported, However, there is no standard methods for qualification and indexation of mechanoluminescent (ML) sensors, the candidate user cannot choose appropriate ML sensors for their needs and requirements.In this presentation, firstly, the achievements of the ML sensing will be introduced, especially the viewpoint of application describe above. Then, we will propose a standard evaluation method of ML sensors using strain (% or mst)-ML luminance (mcd/mm2) curve and express the performance of ML sensor as “ML index”. Finally, we discuss the classification of ML sensor in ML index, to be able users to choose appropriate ML sensor toward crack monitoring and visualizing strain distribution.This presentation is based on results obtained from a project, JPNP2005, commissioned by the New Energy and Industrial Technology Development Organization (NEDO)[1] Nao Terasaki, “Direct Visualization of Mechanical Behavior During Adhesive Bonding Failure Using Mechanoluminescence (ML)”, Interfacial Phenomena in Adhesion and Adhesive Bonding, 4, 209-290 (2024), springer. https://link.springer.com/book/10.1007/978-981-99-4456-9[2] Protecting Infrastructure by Visualizing Stress, NHK WORLD-JAPAN, Science View, https://www3.nhk.or.jp/nhkworld/en/tv/scienceview/20220222/2015274/[3] ISO8065 ISO/PRF 8065, Composites and reinforcements fibres, Mechanoluminescent visualization method of crack propagation for joint evaluation Figure 1

Statistical safety evaluation method for composite high-pressure hydrogen vessels considering stacking sequence effect and fiber strength development rate

We developed a method to evaluate the failure rate (FR) for the cylindrical part of a composite high-pressure hydrogen vessel with arbitrary dimensions, number of layers, and stacking sequences by giving the mean and standard deviation of the fiber strength development rate and the stiffness reduction rate under various damage types. The FR is the rate at which the residual strength of a vessel is below the maximum service pressure (125%NWP). Assuming a case in which the vessel is designed with the damage-tolerance design, the FR was calculated for the case of all-layer matrix cracking (assuming beginning-of-life) and fiber failure in two layers in addition to the matrix cracking (assuming the most severe damage that is tolerable during service). The observations demonstrate the importance of improving the probability of detection for non-destructive testing in ensuring the safety of damage-tolerance-designed vessels after fiber failure. The mean strength of the fibers mainly affected the mean residual strength of the composite high-pressure hydrogen vessels when the dimensions and stacking sequence remained unchanged.

Damage-tolerance design for composite high-pressure hydrogen vessels when AE testing is applied

An approach was proposed to design high-pressure composite hydrogen vessels for fuel cell vehicles with damage tolerance. In addition, a stacking-sequence optimization method was developed, which was built upon the damage tolerance design. A no-growth approach, damage categorization, and residual strength requirements were proposed for the damage-tolerance design method for highpressure hydrogen vessels, which were implemented in the damage-tolerance design method for composite aircrafts. The initial burst pressure was set at 180% of normal working pressure (NWP) assuming that the structural health monitoring (SHM) system with acoustic emission (AE) testing would immediately detect the occurrence of fiber breakage. Stacking-sequence optimization was then conducted to minimize vessel thickness and meet the residual strength requirements. The results show that the thickness of the vessel can be reduced by introducing a damage-tolerant design. Moreover, the proposed method for an optimal design based on the damage-tolerance design method is effective.

Comparative study of plasma, laser, and flame induced activation of HDPE liner surfaces of type 4 hydrogen vessels

ABSTRACT In our study, we compare the surface modifications of coarse HDPE surface induced by atmospheric air plasma, CO2 laser, and flame treatments. An order of WCA decrease of air plasma>flame>CO2 laser methods was detected. The improvement in adhesion strength measured 5 days after the activations followed the same trend. FT-IR and EDS proved that different oxygen compounds were formed after treatments, resulting in increased polar component of the total surface energy. Flame activation showed a saturation character regarding the O-moiety. Hydrophobic recovery showed a linear behavior, with a larger decreasing slope for the polar component than the total surface energy. Plasma treatments induced higher recovery rate; however, restore was not complete here either. The effects of the different CO2 irradiation intensities were nonlinear; SEM and roughness measurements revealed surface ablation or structure formation on the different samples, while after plasma and flame treatment a hilly microtexture appeared. With different mechanisms and intensities, all the tested methods are suitable for increasing the adhesion strength on HDPE surfaces.

Exploring variations in the weight, size and shape of liquid hydrogen tanks for zero-emission fuel-cell vessels

We report an exploration of liquid hydrogen (LH2) tank technology, determining if improving LH2 tank weight, multiplicity or shape enables more hydrogen to be stored on hydrogen vessels. The improvements investigated are well beyond the current LH2 technology state-of-the-art. The platform for this study is a monohull H2 Baseline research vessel powered 100% by hydrogen.Regarding weight reductions, we found that the research vessel does not benefit significantly from large weight reductions of the LH2 tanks. A 50% reduction in mass of the inner pressure vessel led to a 3.1% reduction in the total research vessel weight. Reducing the LH2 tank weight to the asymptotic limit of zero results in a 7.1% reduction in the overall research vessel weight. This maritime application, while benefitting from a reduction in LH2 tank weight, is not a strong driver for LH2 tank weight improvements.The two large LH2 tanks of the H2 Baseline Vessel can be replaced with a multitude of smaller LH2 tanks. In two Multiplicity design variants, the total amount of stored LH2 was ∼5–9% less than that of the H2 Baseline Vessel, which does not motivate conducting the needed R&D that would drive the technology to smaller high-performing LH2 tanks.We did find a significant benefit to improving the shape of LH2 tanks, towards prismatic tanks that would better match the vessel hullform. Considering a “Shape Variant” that included space-consuming features such as tank connection spaces, manifolding and ventilation, we found a 26% improvement in stored LH2 compared to the H2 Baseline Vessel. The large improvement in storage capacity could warrant further LH2 tank R&D that can enable high performing prismatic LH2 tanks, such as pressure vessel steel developments allowing for higher strength/ductility at 20 K, improved insulation systems, methods for efficiently building prismatic tanks with insulation systems fit for 20 K service and flare-less techniques for managing heat leak (venting).The results are reviewed considering the current regulatory restrictions as well as prevailing limitations in LH2 tank manufacturing.

Energy Consumption and Saved Emissions of a Hydrogen Power System for Ultralight Aviation: A Case Study

The growing concern about climate change and the contemporary increase in mobility requirements call for faster, cheaper, safer, and cleaner means of transportation. The retrofitting of fossil-fueled piston engine ultralight aerial vehicles to hydrogen power systems is an option recently proposed in this direction. The goal of this investigation is a comparative analysis of the environmental impact of conventional and hydrogen-based propulsive systems. As a case study, a hybrid electric configuration consisting of a fuel cell with a nominal power of about 30 kW, a 6 kWh LFP battery, and a pressurized hydrogen vessel is proposed to replace a piston prop configuration for an ultralight aerial vehicle. Both power systems are modeled with a backward approach that allows the efficiency of the main components to be evaluated based on the load and altitude at every moment of the flight with a time step of 1 s. A typical 90 min flight mission is considered for the comparative analysis, which is performed in terms of direct and indirect emissions of carbon dioxide, water, and pollutant substances. For the hydrogen-based configuration, two possible strategies are adopted for the use of the battery: charge sustaining and charge depleting. Moreover, the effect of the altitude on the parasitic power of the fuel cell compressor and, consequently, on the net efficiency of the fuel cell system is taken into account. The results showed that even if the use of hydrogen confines the direct environmental impact to the emission of water (in a similar quantity to the fossil fuel case), the indirect emissions associated with the production, transportation, and delivery of hydrogen and electricity compromise the desired achievement of pollutant-free propulsion in terms of equivalent emissions of CO2 and VOCs if hydrogen is obtained from natural gas reforming. However, in the case of green hydrogen from electrolysis with wind energy, the total (direct and indirect) emissions of CO2 can be reduced up to 1/5 of the fossil fuel case. The proposed configuration has the additional advantage of eliminating the problem of lead, which is used as an additive in the AVGAS 100LL.

Distributed fiber optic strain sensing for structural health monitoring of 70 MPa hydrogen vessels

We report on the development and testing of 70 MPa hydrogen pressure vessels with integrated fiber optic sensing fibers for the automotive use. The paper deals with the condition monitoring of such composite pressure vessels using the optical backscatter reflectometry (OBR) which was applied for a distributed fiber optic strain sensing along fully integrated polyimide-coated single-mode glass optical fiber (SM-GOF). The sensing fibers were embedded into the vessel structure by wrapping them over the inside polymer liner during the manufacturing process of the outside carbon fiber reinforced polymer (CFRP). Detecting local strain events by the integrated fiber optic sensors might be an opportunity for monitoring the material degradation. Regarding the investigation of the ageing behavior, both ambient hydraulic cycling tests and slow burst tests were conducted on 70 MPa pressure vessels with embedded fiber optic sensors. The achieved results contribute to the knowledge about material fatigue to guarantee the safe usage during the entire lifetime of the composite hydrogen storage vessels. The presented work stands in context of the European Horizon 2020 research project SH2APED focused on the development of an innovative hydrogen storage system composed of an assembly of nine 70 MPa tubular pressure vessels used as an automotive battery pack.

Study of composite polymer degradation for high pressure hydrogen vessel by machine learning approach

AbstractThe aim of this article is to study the degradation of a composite material under static pressure. The high pressure condition is similar to the one encountered inside hydrogen tanks. Damage modeling was used to evaluate the behavior of hydrogen tanks to high pressure. A practical approach, coupling a finite element method (FEM) simulation and machine learning (ML) algorithm, is suggested. The representative volume element (RVE) was used in association with a choice of a behavior law and a damage law as an input data. Algorithms for ML classification such as K‐nearest neighbors (k‐NN) and a special k‐NN with a dynamic time warping metric were used. The hierarchical clustering through dendrograms visualizations allowed to exhibit the impact of composite parameters in relation to fiber, matrix properties and fiber volume fraction on the strain degradation under external static pressure. Continuing this, the optimum RVE which shows a low degradation value will be exhibited.

Recent Advancements towards Sustainability in Rotomoulding.

Rotational moulding is a unique low-shear process used to manufacture hollow parts. The process is an excellent process method for batch processing, minimal waste and stress-free parts. However, the process has drawbacks such as long cycle times, gas dependency and a limited palette of materials relative to other process methods. This review aimed to shed light on the current state-of-the-art research contributing towards sustainability in rotational moulding. The scope of this review broadly assessed all areas of the process such as material development, process adaptations and development, modelling, simulation and contributions towards applications carving a more sustainable society. The PRISMA literature review method was adopted, finding that the majority of publications focus on material development, specifically on the use of waste, fillers, fibres and composites as a way to improve sustainability. Significant focus on biocomposites and natural fibres highlighted the strong research interest, while recyclate studies appeared to be less explored to date. Other research paths are process modification, modelling and simulation, motivated to increase energy efficiency, reduction in scrap and attempts to reduce cycle time with models. An emerging research interest in rotational moulding is the contribution towards the hydrogen economy, particularly type IV hydrogen vessels.

Multi-scale systematization of damage and failure modes of composite cryogenic hydrogen vessels according to the Fault Tree method

Achieving a safe and lightweight design of composite liquid hydrogen (LH2) vessels without much empirical data requires advanced reliability assessment. An approach based on the Fault Tree method is proposed, to allow the systematization and modelling of functional and structural failure modes and their interactions. A hierarchical system model spanning across the length scales of the LH2 vessel down to the composite material is established. Subsequently, the failure probability of the composite material is estimated in dependence on temperature and load case using Weibull analysis. Using the accident data of US Air Carriers operating under 14 CFR 121 between 2012 and 2019, the probabilities of the load cases are derived, allowing a quantitative reliability analysis of the selected failure modes. Requirements for material and system design are derived in dependence of the maximum allowable failure probability.

Preliminary design of a retrofitted ultralight aircraft with a hybrid electric fuel cell power system

Emission-free aerial propulsion can be achieved with a proton-exchange membrane fuel cell (PEM-FC). In the present investigation, this potential is addressed by designing a hybrid electric power system with fuel cells for an ultralight aerial vehicle to be retrofitted from a conventional fossil-fuelled piston engine configuration. The proposed power system includes a fuel cell, a lithium battery, and a compressed hydrogen vessel. A procedure is proposed to find the size of these components that minimizes the total mass and satisfies the target of a size below 200L and uses performance data of commercially available components. A comparison of different energy management approaches, with and without on-board charge of the battery, is performed. The results underline that the optimal solution is to select the size of the fuel cell to meet the cruise electric request and point out that the maximum discharge current of the battery must be regarded as a key issue in sizing this component, because of the very high take-off power.

Damage-tolerance design method for composite high-pressure hydrogen vessels of fuel cell vehicles and stacking-sequence optimization method based on the design method

An approach was proposed to design high-pressure composite hydrogen vessels for fuel cell vehicles with damage tolerance. In addition, a stacking-sequence optimization method was developed, which was built upon the damage tolerance design. A no-growth approach, damage categorization, and residual strength requirements were proposed for the damage-tolerance design method for high-pressure hydrogen vessels, which were implemented in the damage-tolerance design method for composite aircrafts. The initial burst pressure was set at 180% of normal working pressure (NWP) assuming that the structural health monitoring (SHM) system with acoustic emission (AE) testing would immediately detect the occurrence of fiber failure. Stacking-sequence optimization was then conducted to minimize vessel thickness and meet the residual strength requirements. As a result of the optimization, the calculations confirmed that the vessel thickness could be reduced by approximately 52% of the existing vessel stacking sequence. The results show that the thickness of the vessel can be reduced by introducing a damage-tolerant design. Moreover, the proposed method for an optimal design based on the damage-tolerance design method is effective.

Analysis of Forming Factors for Build-Up Phenomenon in High Pressure Hydrogen Vessel

Analysis of Forming Factors for Build-Up Phenomenon in High Pressure Hydrogen Vessel

Performance characterization and comparison study of silver molecular sieve hydrogen adsorbents in liquid hydrogen vessels

Four commercially available silver molecular sieve (SMS) hydrogen adsorbents were tested and characterized in terms of both material characterization and hydrogen adsorption performance, and an attempt was made to establish the constitutive relationship between material structure and hydrogen adsorption. The results show that the four SMS products have an average Ag content between 33 and 36 wt%, with the SBET between 200 and 400 m2/g and the cumulative hydrogen adsorption capacity in the range of 10–20 cm3(STP)/g. The two SMS products with the best hydrogen adsorption performance can replace or even surpass PdO in the vacuum interlayer of liquid hydrogen vessels. Their hydrogen adsorption capacity at an equilibrium pressure of 2 × 10−2 to 10 Pa is about two orders of magnitude greater than that of PdO. The constitutive relationship between material characterization and hydrogen adsorption performance suggests that the realization of new efficient SMS hydrogen adsorbents requires micro-mesoporous composite molecular sieves with large specific surface area and pore volume, and further improvements in the silver ions exchange process to load more silver ions into the internal pores of the molecular sieve microspheres.

Hydrogen-related degradation of fracture properties and altered fracture behavior of Cr–Mo steel used in hydrogen stationary vessels

This study comprehensively analyzes the effect of high-pressure hydrogen gas on the elastic-plastic fracture toughness, fatigue crack growth rate (FCGR) properties, and the corresponding fracture behavior of Cr–Mo steel in hydrogen stationary vessels. The fracture toughness value under 99 MPa hydrogen pressure significantly reduced by approximately one-third of the value tested in ambient air while FCGRs tested under hydrogen environments at a specified ΔK exhibited an approximate two-order magnitude increase compared to those observed in ambient air. The hydrogen-assisted fracture mechanism, encompassing crack initiation, propagation, and crack arrested, was meticulously examined. The distinct variations in fracture modes with changes in the ΔK range can be attributed to the synergistic interaction of HELP and HEDE mechanisms. Leak before break (LBB) behavior was not satisfied for the hydrogen vessel due to a significant reduction in the fracture toughness of materials when exposed to 99 MPa H2.

Modelling the conjugate heat transfer during the fast-filling of high-pressure hydrogen vessels for vehicular transport

Compressed gas in cylinders is currently the preferred solution for storing hydrogen on board vehicles. Fast-filling combined with high storage pressures is required to meet competitive targets of long driving ranges and short refuelling times. Experiments and CFD models have shown that the fast-filling leads to significant rise in temperature within the hydrogen cylinder, which can lead to its structural failure. Thus, controlling the rise in temperature is vital during the refuelling process. This paper describes the implementation of a universal thermodynamic model that determines the gas and structural temperature during the fast-filling of hydrogen cylinders. It includes the computation of conjugate heat transfer from the gas to the cylinder structure. The thermodynamic model requires negligible computational time without compromising accuracy and can used to implement different fast-filling scenarios on a laptop or personal computer. The flexibility and robustness of the model is shown as it is capable of modelling the fast-filling of cylinders while varying different key parameters such as fill time, structural material, cylinder volume, final pressure, filling rate, initial temperatures and pressures.

A cleaner and more efficient energy system achieving a sustainable future for road transport

A novel integrated cooling system is developed for future medium to large electric vehicles by integrating the fuel cell, battery, metal-hydride, heat pump, and liquid desiccant dehumidification system to reduce power consumption and extend vehicle's driving range. The system benefits from the reuse of the normally wasted energy in the form of pressure difference and wasted thermal energy, from the hydrogen vessel, the fuel cell stack, and the battery pack. A numerical model for the proposed system and a finite element model for the dehumidifier and regenerator are developed and validated by experimental results from published data. A comprehensive evaluation of the impacts of the ambient air temperature and humidity, fuel cell current output, battery discharging C rate, and air mass flow rate on the Coefficient of Performance (COP), outlet air temperature, and cooling capacity is conducted. Two operating modes, namely non-compressive mode and heat pump supplemental mode are investigated and a detailed comparison between these two modes is undertaken. Furthermore, the proposed system under heat pump supplemental mode has been compared to other published cooling systems and dehumidification systems. Under non-compressive mode, results indicate that the proposed system can provide sufficient cooling capacity without the need of the compressor when the supply air mass flow rate is lower than 0.03 kg/s, under the specific operating situation. Under the heat pump supplemental mode, the proposed system can operate at 36 °C with a COP greater than 4, which is 56% higher than the cited published results, although the COP of the proposed system also considers battery cooling. Heat pump supplemental mode drastically reduces the 12-s insufficient cooling period that occurs at the beginning of the charging to discharging transition between the two metal hydrides to 2 s compared to non-compressed mode. Overall, this study provides a potential solution for future zero-emission vehicles by utilizing the heat and electric co-generation characteristic of the fuel cell, the isothermal characteristic of the metal hydride, and dehumidification and cooling characteristics of the liquid desiccant dehumidification system to extend the driving range of the electric vehicles and reduce energy consumption for cooling. Moreover, the proposed system can also provide domestic cooling loads and power by integrating the system into residential buildings.

Optimal design of curing process for manufacturing a high pressure hydrogen vessel (type 4)

Optimal design of curing process for manufacturing a high pressure hydrogen vessel (type 4)

Improving small unmanned aerial vehicle flight endurance with cryo-compressed hydrogen vessels

Detailed analysis indicates that substantial increases (22–43%) in flight endurance of small unmanned aerial vehicles (UAVs) powered by liquid hydrogen (LH2) are possible by increasing the maximum allowable pressure of the cryogenic storage vessel beyond the critical point to contain evaporated hydrogen (H2) and mitigate vent losses to the environment. Taking an existing UAV (US Naval Research Laboratory's “Ion Tiger”) as a baseline, we consider the effect of increasing Dewar maximum allowable pressure on flight endurance, under two different scenarios. In Case 1, the weight of the H2 storage system (including H2) is kept equal to the baseline design to maintain flight conditions unchanged. In Case 2, the external volume of the Dewar is kept equal to the baseline design, and the weight of the Dewar (and UAV) increases when the maximum allowable pressure increases, with the result that the propulsion power for the heavier UAV increases.The results are favorable. Although the modified Dewars have smaller inner volume (Case 1) or greater weight (Case 2) than the original Ion Tiger, flight endurance increases by 22% (Case 1) and 43% (Case 2), because the large H2 vent losses (39%) of the original design are reduced to only 1.6% (Case 1) and 1% (Case 2). The much higher utilization efficiency of the H2 stored in these modified Dewars compensates for their volume and weight disadvantages, resulting in UAVs with superior endurance.

Hydrogen Liquefaction by Active Magnetic Regenerative Refrigeration

The article summarizes the research and development of magnetic refrigeration for hydrogen liquefaction, and the Active Magnetic Regenerative Refrigeration (AMRR) developed by National Institute for Materials Science (NIMS). The NIMS-AMR consists of optimized AMR beds, a superconducting solenoid with correction coils, and a dedicated liquid hydrogen vessel with a liquid level sensor. This article also reports the first successful demonstration of hydrogen liquefaction with the AMRR.