Validation of Selected Optical Methods for Assessing Polyethylene (PE) Liners Used in High Pressure Vessels for Hydrogen Storage

Abstract

A polyethylene (PE) liner is the basic element in high-pressure type 4 composite vessels designed for hydrogen or compressed natural gas (CNG) storage systems. Liner defects may result in the elimination of the whole vessel from use, which is very expensive, both at the manufacturing and exploitation stage. The goal is, therefore, the development of efficient non-destructive testing (NDT) methods to test a liner immediately after its manufacturing, before applying a composite reinforcement. It should be noted that the current regulations, codes and standards (RC&S) do not specify liner testing methods after manufacturing. It was considered especially important to find a way of locating and assessing the size of air bubbles and inclusions, and the field of deformations in liner walls. It was also expected that these methods would be easily applicable to mass-produced liners. The paper proposes the use of three optical methods, namely, visual inspection, digital image correlation (DIC), and optical fiber sensing based on Bragg gratings (FBG). Deformation measurements are validated with finite element analysis (FEA). The tested object was a prototype of a hydrogen liner for high-pressure storage (700 bar). The mentioned optical methods were used to identify defects and measure deformations.

High hydrogen release by cryo-adsorption and compression on porous materials

“…Technical features of commercial types I, II, III and IV high-pressure tanks (adapted from [23] and data recovered from [37]). Compressed hydrogen tanks operate under high stress conditions and require periodic inspections to ensure their safety [43][44][45]. Although binding legal regulations only require periodic inspections of high-pressure tanks [45], several studies consider the incorporation of continuous structural health monitoring (SHM) systems into high-pressure tanks [43,44,46].…”

“…Compressed hydrogen tanks operate under high stress conditions and require periodic inspections to ensure their safety [43][44][45]. Although binding legal regulations only require periodic inspections of high-pressure tanks [45], several studies consider the incorporation of continuous structural health monitoring (SHM) systems into high-pressure tanks [43,44,46]. SHM operates by direct feedback of the physical properties of the system (i.e., displacement and temperature), which allows for the determination of other parameters such as distribution of stress, creep or temperature, and detection of leaks [43,47,48].…”

“…Therefore, SHM could potentially reduce the weight and costs of the high-pressure tanks [43,49]. Various non-destructive techniques have been considered (i.e., shearography, acoustic emission, vibration monitoring, ultrasonic monitoring, radiography, and thermography) [44,46,47]. The integration of fiber optic sensors into tanks could be a suitable approach for SHM because they have high sensitivity in long-term measurements, resistance to electromagnetic interference, and easy integration into the tank structure [43,49].…”

“…In general, fiber optic sensors are permanently attached to 13 tanks and/or integrated into the composite material structure without influencing its mechanical properties [46,49]. Various optical methods have been investigated for the fabrication of optical sensors, such as visual inspection, digital image correlation (DIC), and fiber Bragg grating (FBG)-based sensing [43,44,47,48].…”

Challenges and Future Perspectives on Production, Storage Technologies, and Transportation of Hydrogen: A Review

“…Gasior et al investigated high-pressure type 4 composite vessels based on polyethylene (PE) liner, and they suggested applying a non-destructive evaluation of PE at the beginning of the manufacturing chain of high-pressure composite vessels. [55] Storage of hydrogen in the form of ammonia is another promising method, as ammonia has a higher auto-ignition Table 2. Comparison of some techno-economic characteristics of ALK, PEM, and SOEC electrolyzers.…”