Type IV pressure vessels are commonly used for hydrogen on-board, stationary or bulk storages. When pressurized, hydrogen permeates through the materials and solves into them. Emptying then leads to a difference of pressure at the interface between composite and liner, possibly leading to a permanent deformation of the plastic liner called “collapse” or “buckling”. This phenomenon has been studied through French funded project Colline, allowing to better understand its initiation and longterm effects. This paper presents the methodology followed, using permeation tests, hydrogen decompression tests on samples, and gas diffusion calculation in order to determine safe operating conditions, such as maximum flow rate or residual pressure level.

There are times in engineering when it seems that safety and equipment cost reduction are conflicting priorities. This could be the case for pressure relief valves and vent stack sizing. This paper explores the role that component availability (particularly variety in flow and orifice diameters) plays in the engineer’s decision of a relief valve. This paper outlines the guidelines and assumptions in sizing and selecting pressure relief devices (PRDs) found in a typical high pressure hydrogen fueling station. It also provides steps in sizing the station common vent stack where the discharge gas is to be routed to prior being released into the atmosphere. This paper also explores the component availability landscape for hydrogen station designers and identifies opportunities for improvement in the supply chain of components as hydrogen fueling stations increase in number and size. American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section VIII (ASME BPVC Section VIII), Compressed Gas Association S-1.3 (CGA S-1.3), and American Petroleum Institute 520 (API 520) standards provide specific design criteria for hydrogen pressure relief valves. Results of these calculations do not match the available components. The available safety relief valves are 50 to 87 times larger than the required calculated flow capacities. Selecting a significantly oversized safety relief valve affects the vent stack design as the stack design requires sizing relative to the actual flowrate of the safety relief valve. The effect on the vent stack size in turn negatively affects site safety radiation threshold set back distances.

Efficient storage of hydrogen is crucial for the success of hydrogen energy markets. Hydrogen can be stored either as a compressed gas, a refrigerated liquefied gas, a cryo-compressed gas or in hydrides. This paper gives an overview of compressed hydrogen storage technologies focusing on high pressure storage tanks in metal and in composite materials. It details specific issues and constraints related to the materials and structure behavior in hydrogen and conditions representative of hydrogen energy uses.

Proper management of hydrogen gas is very important for safety of nuclear power plants. Hydrogen removal system by hydrogen recombination reaction (water formation reaction) on a catalyst is one of the candidates for avoiding hydrogen explosion. We have observed in situ and time-resolved structure change of platinum metal nanoparticle catalyst during hydrogen recombination reaction by using simultaneous measurement of temperature-programmed reaction and X-ray absorption fine structure (TPR-XAFS). A poisoning effect by carbon monoxide on catalytic activity was focused. It was found that the start of hydrogen recombination reaction is closely connected with the occurrence of the decomposition of adsorbed carbon monoxide molecules and creation of surface oxide layer on platinum metal nanoparticles.

Polymers for O-rings, valve seats, gaskets, and other sealing applications in the hydrogen infrastructure face extreme conditions of high-pressure H2 (0.1 to 100 MPa) during normal operation. To fill current knowledge gaps and to establish standard test methods for polymers in H2 environments, these materials can be tested in laboratoryscale H2 manifolds mimicking end use pressure and temperature conditions. Beyond the influence of high pressure H2, the selection of gases used for leak detection in the H2 test manifold, their pressures and times of exposure, gas types, relative diffusion and permeation rates are all important influences on the polymers being tested. These effects can be studied ex-situ with post-exposure characterization. In a previous study, four polymers (Viton A, Buna N, High Density Polyethylene (HDPE) and Polytetrafluoroethylene (PTFE)), commonly used in the H2 infrastructure, were exposed to high-pressure H2 (100 MPa). The observed effects of H2 were consistent with typical polymer property-structure relationships; in particular, H2 affected elastomers more than thermoplastics. However, since high pressure He was used for purging and leak detection prior to filling with H2, a study of the influence of the purge gas on these polymers was considered necessary to isolate the effects of H2 from those of the purge gas. Therefore, in this study, Viton A, Buna N, and PTFE were exposed to the He purge procedure without the subsequent H2 exposure. Additionally, six polymers, Viton A, Buna N, PTFE, Polyoxymethylene (POM), Polyamide 11 (Nylon), and Ethylenepropylenediene monomer rubber (EPDM), were subjected to high pressure Ar (100 MPa) followed by high pressure H2 (100 MPa) under the same static, isothermal conditions to identify the effect of a purge gas with a significantly larger molecular size than He. Viton A and Buna N elastomers are more prone to irreversible changes as a result of H2 exposure from both Ar and He leak tests as indicated by influences on storage modulus, extent of swelling, and increased compression set. EPDM, even though it is an elastomer, is not as prone to high-pressure gas influences. The thermoplastics are generally less influenced by high pressure regardless of the gas type. Conclusions from these experiments will provide insight into the influence of purging processes and purge gases on the subsequent testing in high pressure gaseous H2. Control for the influence of purging on testing results is essential for the development of robust test methods for evaluating the effects of H2 and other high-pressure gases on the properties of polymers

The influence of plastic deformation on hydrogen diffusion is of critical significance for hydrogen embrittlement (HE) studies. In this work, thermal desorption spectroscope (TDS), slow strain rate test (SSRT), feritscope, transmission electron microscope (TEM) and TDS model are used to establish the relationship between plastic deformation and hydrogen diffusion, aiming at unambiguously elucidating the effect of pre-existing traps on hydrogen diffusion of hot-rolled S30408. An effective way is developed to deduce hydrogen apparent diffusivity in this paper. Results indicate apparent diffusivities decrease firstly and then increase with increasing plastic strain at room temperature. Hydrogen diffusion changing with plastic deformation is a complicated process involving multiple factors. It is suggested to be divided into two processes controlled by dislocations and strain-induced martensite, respectively, and the transformation strain is about 20% demonstrated by experiments.

Diffusion coefficient is in significant dependence on vacancy concentration due to that migration of vacancy is the dominant mechanism of atom transport or diffusion in processes, such as void formation, dislocation movement and solid phase transformation. This study aims to investigate the effect of vacancy concentration on hydrogen diffusion in alpha-Fe by molecular dynamics simulations, especially at low temperatures and with loading. Comparisons of the diffusion coefficients between alpha-Fe with a perfect structure and different-concentration vacancies, as well as comparisons between experimental and theoretical results had been made to characterize and summarize the effect of vacancy on hydrogen diffusion coefficient.

Stationary pressure vessels for the storage of large volumes of gaseous hydrogen at high pressure (>70 MPa) are typically manufactured from Cr-Mo steels. These steels display hydrogen-enhanced fatigue crack growth, but pressure vessels can be manufactured using defect-tolerant design methodologies. However, storage volumes are limited by the wall thickness that can be reliably manufactured for quench and tempered Cr-Mo steels, typically not more than 25-35 mm. High-hardenability steels can be manufactured with thicker walls, which enables larger diameter pressure vessels and larger storage volumes. The goal of this study is to assess the fracture and fatigue response of high hardenability, Ni-Cr-Mo pressure vessel steels for use in high-pressure hydrogen service at pressure in excess of 1000 bar. Standardized fatigue crack growth tests were performed in gaseous hydrogen at frequency of 1Hz and for R-ratios in the range of 0.1 to 0.7. Elastic-plastic fracture toughness measurements were also performed. The measured fatigue and fracture behavior is placed into the context of previous studies on fatigue and fracture of Cr-Mo steels for gaseous hydrogen.

The development of a ‘Hydrogen Economy’ will see hydrogen fuel cells used in transportation and the generation of power for buildings as part of a decentralised grid, with low power units used in domestic and commercial environmental, situations. Low power fuel cells will be housed in small protective enclosures, which must be ventilated to prevent a build-up of hydrogen gas, produced during normal fuel cell operation or a supply pipework leak. Hydrogen’s flammable range (4-75%) is a significant safety concern. With poor enclosure ventilation, a low-level leak (below 10 lpm) could quickly create a flammable mixture with potential for an explosion. Mechanical ventilation is effective at managing enclosure hydrogen concentrations, but drains fuel cell power and is vulnerable to failure. In many applications (e.g. low power and remote installation) this is undesirable and reliable passive ventilation systems are preferred. Passive ventilation depends upon buoyancy driven flow, with the size and shape of ventilation openings critical for producing predictable flows and maintaining low buoyant gas concentrations. Environmentally installed units use louvre vents to protect the fuel cell, but the performance of these vents compared to plain vertical vents is not clear. Comparison small enclosure tests of ‘same opening area’ louvre and plain vents, with leak rates from 1 to 10 lpm, were conducted. A displacement ventilation arrangement was installed on the test enclosure with upper and lower opposing openings. Helium gas was released from a 4mm nozzle at the base of the enclosure to simulate a hydrogen leak. The tests determined that louvre vents increased average enclosure hydrogen concentrations by approximately 10% across the leak range tested, but regulated the flow. The test data was used in a SolidWorks CFD simulation model validation exercise. The model provided a good qualitative representation of the flow behaviour but under predicted average concentrations.