3.5 Sicherheit von Gasspeichern
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The presentation starts with the first agreement of making a national attempt for the introduction of a pV-limit for hydrogen transport. It explains aspects of the technical development, provides an impression of catastrophic incidents, and explains the difference between risk control and consequence limitation. Then the process of determining consequences and the result from the discussion at the UN-WG are explained. The next part summarises the approach for counting the number of impacted persons as a function of the model of pressure wave, the pressure peak, the limits of injured persons and the population density. Finally, the latest state of the discussion and the subsequent recommendations for a pV-value and the adequate phrases for explanation are introduced.
While hydrogen is one of the most promising energy carriers, the safety of hydrogen storage technology remains one of the most important factors for technological and societal approval. While the engineering safety factors of the pressure vessels are kept high, the periodic inspection and the limited lifetime are making the application very costly considering manpower, time, money, and material waste. The development of an integrated structural health monitoring system can allow an easy transition from the current situation to cost-effective predictive maintenance. Hence, we propose to integrate three different SHM systems into hydrogen pressure vessels, namely guided wave ultrasonics, acoustic emission, and fibre optic sensing, to continuously monitor the condition and integrity.
In this work, we evaluated the condition of a Type IV composite overwrapped pressure vessel using ultrasonic guided wave propagation. We mounted fifteen piezo-electric wafers on the composite cylinder by shaping three rings containing five sensors each. We acquired data from the sensor network following different boundary conditions with artificial damages on the selected locations. The data were evaluated with guided wave tomography techniques using ultrasonic features (amplitude, frequency, etc.) as well as artificial intelligence (AI). The results suggest that both traditional guided wave fusion techniques and AI-based characterization methods can detect artificial damages. In future work, it is planned to integrate acoustic emission and fibre optic sensing. Moreover, the measurement and the test results will be implemented into a digital twin to derive trends and make predictions on the damage propagation as well as the remaining useful lifetime.
This work has received funding from German Ministry of Economic Affairs and Climate Actions within the QI-Digital initiative (www.qi-digital.de).
The stacking sequence of a real scale type IV pressure vessels has been found. Feasibility study of a multiscale model has been carried out by modifying the original stacking sequence. All of the results were displayed in a Sample Performance Chart (SPC), where different burst pressure in terms of mean and scatter had been found.
The presentation reflects the questions that have been raised by member states and NGOs.
As background information details on the question how to choose a suitable salvage pressure receptacle (SPR) are provided. This leads to the need for deleting the volume limitation for SPRs and to the discussions in 2014 and 2016 on this issue.
As an adequate substitution for deleting the volume limit for SPRs it is proposed to limit the pressure receptacles to be stored in by a maximum pressure-volume-value of 1.5 Mio bar-litres.
After some explanations to standardisation projects currently also tackling this pV-limit, some risk-based safety criteria for a limitation are mentioned with the focus of the consequence level and the general avoidance of catastrophic worst case scenarios.
Safety criteria for the transport of hydrogen in permanently mounted composite pressure vessels
(2020)
The recent growth of the net of hydrogen fuelling stations increases the demands to transport compressed hydrogen on road by battery vehicles or tube-trailers, both in composite pressure vessels. As a transport regulation, the ADR is applicable in Europe and adjoined regions, and is used for national transport in the EU. This regulation provides requirements based on the behaviour of each individual pressure vessel, regardless of the pressure of the transported hydrogen and relevant consequences resulting from generally possible worst case scenarios such as sudden rupture. In 2012, the BAM (German Federal Institute for Materials Research and Testing) introduced consequence-dependent requirements and established them in national transport requirements concerning the “UN service life checks” etc. to consider the transported volume and pressure of gases. This results in a requirement that becomes more restrictive as the product of pressure and volume increases. In the studies presented here, the safety measures for hydrogen road transport are identified and reviewed through a number of safety measures from countries including Japan, the USA and China. Subsequently, the failure consequences of using trailer vehicles, the related risk and the chance are evaluated. A benefit-related risk criterion is suggested to add to regulations and to be defined as a safety goal in standards for hydrogen transport vehicles and for mounted pressure vessels. Finally, an idea is given for generating probabilistic safety data and for highly efficient evaluation without a significant increase of effort.
In this lecture, the safety assessment of hydrogen gas storage systems is presented using the example of composite pressure vessels. The main element is a probabilistic approval approach based on five steps. Firstly, the testing and evaluation of properties at the beginning of life are shown. Secondly, methods for artificial aging and the effect on the residual strength are presented. Thirdly, testing against dedicated accidents is introduced. Fourthly, effects on the surveillance of production quality are discussed. Finally, degradation and the end of life are estimated. Background information and examples are given for each step. The assessment presented is a method applicable for many safety-related systems.
In this lecture, the safety assessment of hydrogen gas storage systems is presented using the example of composite pressure vessels. The main element is a probabilistic approval approach based on five steps. Firstly, the testing and evaluation of properties at the beginning of life are shown. Secondly, methods for artificial aging and the effect on the residual strength are presented. Thirdly, testing against dedicated accidents is introduced. Fourthly, effects on the surveillance of production quality are discussed. Finally, degradation and the end of life are estimated. Background information and examples are given for each step. The assessment presented is a method applicable for many safety-related systems.
In this lecture, the safety assessment of hydrogen gas storage systems is presented using the example of composite pressure vessels. The main element is a probabilistic approval approach based on five steps. Firstly, the testing and evaluation of properties at the beginning of life are shown. Secondly, methods for artificial aging and the effect on the residual strength are presented. Thirdly, testing against dedicated accidents is introduced. Fourthly, effects on the surveillance of production quality are discussed. Finally, degradation and the end of life are estimated. Background information and examples are given for each step. The assessment presented is a method applicable for many safety-related systems.
In this lecture, the safety assessment of hydrogen gas storage systems is presented using the example of composite pressure vessels. The main element is a probabilistic approval approach based on five steps. Firstly, the testing and evaluation of properties at the beginning of life are shown. Secondly, methods for artificial aging and the effect on the residual strength are presented. Thirdly, testing against dedicated accidents is introduced. Fourthly, effects on the surveillance of production quality are discussed. Finally, degradation and the end of life are estimated. Background information and examples are given for each step. The assessment presented is a method applicable for many safety-related systems.
In this presentation safety aspects of hydrogen transportation are discussed. At first, the regulatory background and level of safety are presented. In the second part, the modelling of consequence due to sudden rupture of pressure receptacles is explained. Finally, the results are used to define a limit for consequence to enable an acceptable and safe transport of hydrogen.
Hydrogen is a central component of the energy transition and the European Green Deal for a climate-neutral Europe. To be able to achieve the targets defined by 2045, the EU and the German government have drafted a framework for action and are making long-term investments in research, development and the rapid implementation of innovative hydrogen technologies.
The conditions for a successful energy transition and the economic use of green hydrogen as a clean energy carrier are Hydrogen readiness and a rapid market ramp-up, as well as the establishment of the necessary value chains in the national and European framework. Reliable quality and safety standards are the prerequisite for ensuring safety of supply and environmental compatibility and for creating trust in these technologies.
BAM has bundled its expertise in the field of hydrogen technologies into a competence center H2Safety@BAM to create confidence in the technology and to support the hydrogen strategies of the German government and the EU. The topic of hydrogen has been current at BAM for more than one hundred years and is also currently the focus of numerous research and cooperation activities. The competence centre H2Safety@BAM and its vision of “We build trust in hydrogen technologies” will be presented with its many safety-related topics, which can be found throughout the entire hydrogen value chain. Two deep dives will present the results on projects dealing with the design-to-cost issue of classical pressurized gas storage containments and the consequences of the release of liquid hydrogen, which will be roughly compared to the release of ammonia.
BAM is part of the “Quality Infrastructure Digital” (QI Digital) initiative of the German Federal Ministry for Economic Affairs and Climate Action (BMWK). This initiative aims at coordinating a large cooperation project, “QI Digital” for making German and European quality management systems fit for the digital transformation. It is a fact that the digitization of new products and services is occurring much faster than quality management systems can be accordingly updated. Thus, the digital transformation of quality management is necessary to preserve the competitiveness of the German and European industries that stand for quality and safety in the global market. The Use Case “Reliable Hydrogen Refueling Station” of QI Digital aims at creating new solutions that are transferable to other technical systems and at further developing standards and technical rules as a contribution to technology transfer and innovation.
As a part of the QI-Digital cooperation project, BAM is setting up a hydrogen refuelling station research platform at the Test site for Technical Safety in Horstwalde. Based on this platform, BAM intends to develop, to test and to optimize new measurement techniques as well as data acquisition and processing methods for hydrogen refuelling stations and their periphery in close cooperation with partners from the quality infrastructure and industry. The presentation will introduce the hydrogen refuelling station use case and provide insights into the issues and research goals of the associated subprojects.
Photopolymer derived carbon grows in popularity, yet the range in available feature sizes is limited. Here we focus on expanding the field to low surface to volume ratio (SVR) structures. We describe a high temperature acrylic photopolymerizable precursor with FTIR and DSC and develop a thermal inert-gas treatment for producing architected carbon in the mm scale with SVR of 1.38 x10-3 μm-1. Based on TGA and MS, we distinguish two thermal regimes with activation energies of ~79 and 169 kJ mol-1, which we reason with mechanisms during the polymer’s morphologic conversion between 300 - 500 °C. The temperature range of the major dimensional shrinkage (300-440 °C, 50%) does not match the range of the largest alteration in elemental composition (440-600 °C, O/C 0.25-0.087%). The insights lead to an optimized thermal treatment with an initial ramp (2 °C min-1 to 350 °C), isothermal hold (14h), post hold ramp (0.5 °C min-1 to 440 °C) and final ramp (10 °C min-1 to 1000 °C). The resulting carbon structures are dimensionally stable, non-porous at the μm scale, and comprise an unprecedented variation in feature sizes (from mm to μm scale). The findings shall advance architected carbon to industrially relevant scales.
With the fast development in the field of additive manufacturing, triply periodic minimal surface (TPMS) based porous media have recently found many uses in mechanical property tuning. However, there is still a lack of understanding in their porosity-dependent permeability and electrical as well as thermal conductivity. Here, we perform finite volume simulations on the solid and void domains of the Schoen gyroid (SG), Schwarz primitive (SP) and Schwarz primitive beam (SPB) TPMS with porosities between 63% and 88% in Ansys Fluent. A simple cubic lattice (CL) of equivalent porosity served as reference. The SPB and CL showed up to one order of magnitude higher permeabilities than the SG and SP. However, SG and SP have about 1.3 and 2.6 times the electrical and thermal conductivity of SPB and CL, respectively. Furthermore, the properties of SPB and CL are largely affected by the surface area density, whereas tortuosity variation does not impact permeability and conductivity to a major extent. Finally, empirical relations are adapted to describe the presented data and thus, they may enable future designers of TPMS based porous structures to fine-tune the geometries according to the requirements on permeability and electrical as well as thermal conductivity.
Monte-Carlo-Analysis of Minimum Burst Requirements for Composite Cylinders for Hydrogen Service
(2021)
For achieving Net Zero-aims hydrogen is an indispensable component, probably the main component. For the usage of hydrogen, a wide acceptance is necessary, which requires trust in hydrogen based on absence of major incidents resulting from a high safety level. Burst tests stand for a type of testing that is used in every test standard and regulation as one of the key issues for ensuring safety in use. The central role of burst and proof test is grown to historical reasons for steam engines and steel vessels but - with respect for composite pressure vessels (CPVs) - not due an extraordinary depth of outcomes. Its importance results from the relatively simple test process with relatively low costs and gets its importance by running of the different test variations in parallel. In relevant test und production standards (as e. g. ECE R134) the burst test is used in at least 4 different meanings. There is the burst test on a) new CPVs and some others b) for determining the residual strength subsequent to various simulations of ageing effects. Both are performed during the approval process on a pre-series. Then there is c) the batch testing during the CPVs production and finally d) the 100% proof testing, which means to stop the burst test at a certain pressure level. These different aspects of burst tests are analysed and compared with respect to its importance for the resulting safety of the populations of CPVs in service based on experienced test results and Monte-Carlo simulations. As main criterial for this the expected failure rate in a probabilistic meaning is used. This finally ends up with recommendations for relevant RC&S especially with respect to GTR 13.
We present the results of distributed fiber optic strain sensing for condition monitoring of a hybrid type IV composite fully wrapped pressure vessel using multilayer integrated optical fibers. Distributed strain sensing was performed for a total number of 252,000 load cycles until burst of the vessel. During this ageing test material fatigue could be monitored and spatially localized. Critical material changes were detected 17,000 cycles before material failure. Results have been validated by acoustic emission analysis.
The publication is an extended abstract on the modelling of the manufacturing process related residual stresses in type 4 pressure vessels for hydrogen storage. A 2D analytical model based on the classical laminate theory and a 3D finite element model are introduced. The calculated residual stress state after the filament winding process as well as the stress state in service are presented and discussed.
The subject of permeation of hoses according to ISO 3821 for
hydrogen was discussed for a long time in ISO/TC 44/SC 8. The reason
is a considerable leakage of hydrogen diffused into the hose material
over the end face of the hose. Because of this unsolved, safety-related
problem of hoses sold on the market, measurements should be carried
out in order to be able to better assess the problem. BAM has declared
its attendance to provide a required fast solution to this issue.
In ultrasonic testing, material and structural properties of a specimen can be derived from the time-of-flight (ToF). Using signal features, such as the first peak or envelope maximum, to calculate the ToF is error-prone in multipath arrangements or dispersive and attenuating materials, which is not the case for the signal onset. Borrowing from seismology, researchers used the Akaike information criterion (AIC) picker to automatically determine onset times. The most commonly used formulation, Maeda's AIC picker, is reassessed and found to be based on inappropriate assumptions for signals often used in ultrasonic testing and dependent on arbitrary parameters. Consequently, an onset picker for ultrasonic through-transmission measurements is proposed, based on a spectral entropy criterion (SEC) to model the signal using the AIC framework. This SEC picker takes into account the spectral properties of the ultrasonic signal and is virtually free of arbitrary parameters. Synthetic and experimental data are used to compare the performance of SEC and AIC pickers. It is shown that the accuracy of onset picking is improved for densely sampled data.
Composite pressure vessels (CPVs) are becoming the state of the art for storage for compressed hydrogen (CH2) in automotive applications. There is a strong interest of car manufacturers to use lightweight and less-costly gas storage units. In order to reduce the necessary amount of expensive carbon fibre, the nominal safety margins are becoming gradually smaller, pushing the limits of the regulations for type approval. At the same time, the total volume of these vessels increases to extend the range of the vehicles, increasing the consequences for worst-case scenarios like the rupture of the CPVs in service.
This presentation presents insights gained in the project “TAnk HYdrogen Automotive” (TAHYA). Its aim is to improve the safety of current regulations for type approval of pressure vessels for the use in hydrogen fueled vehicles, namely GTR No. 13 and ECE R 134.
For the assessment of safety, the probabilistic approach developed by division 3.5 of BAM is used. Monte-Carlo-Simulations were conducted leading to the identification of several weak spots, mainly found in the burst test and the batch test.
By changing the requirements for burst tests and the approach for batch tests, the identified weak spots can be strongly reduced.
The objective of this work is to find a method that describes the degree of damage from an impact experiment. This experiment was performed on Composite Pressure Vessels (CPV) in order to find the correlation of impact damage to the residual burst pressure. Computed Tomography (CT) approach was used to capture the before and after impact condition of the CPVs. The Wasserstein function was used to calculate how much the after impact image has differed from the original one. In the end, a good correlation was obtained to the residual burst pressure.
The objective of this work is to find a method that describes the degree of damage from an impact experiment. This experiment was performed on Composite Pressure Vessels (CPV) in order to find the correlation of impact damage to the residual burst pressure. Computed Tomography (CT) approach was used to capture the before and after impact condition of the CPVs. The Wasserstein function was used to calculate how much the after impact image has differed from the original one. In the end, a good correlation was obtained to the residual burst pressure. The smaller the Wasserstein distance is, the higher the residual burst pressure would be and vice versa.
The introduction reflects the political background in Germany and worldwide concerning hydrogen as energy carrier. This leads to available hydrogen strategies and the reaction of BAM by launching the competence centre H2Safety@BAM. Fokus is set on the competence area TestCert, the special role of the division “Safety of Gas Storage Systems” there and its increasing success in research activities.
The main part explains the needs for a risk-controlled market ramp-up concerning hydrogen products and appropriate measures being under development in division 3.5: risk control, tools for consequence estimation and limitation, probabilistic assessment of end of safe life, the efficiency assessment and optimization of current regulations, the structural health monitoring (SHM) with necessary improvement of measures for quality management in the digital world of safety assessment. Last but not least, the wide range of full-scale testing and simulation of worst-case scenarios is explained.
In the DECHEMA Virtual Talks, general aspects of the safety and acceptance of hydrogen technologies were presented. How can trust in new technologies be built when past accidents led to myths and fairy tales? The presentation does away with general prejudices and shows that handling hydrogen is neither more unsafe nor safer than handling other fuel gases. The basis for the safe handling of hydrogen is always a risk analysis.
The reverse electrodialysis heat engine (REDHE) is a promising salinity gradient energy technology, capable of producing hydrogen with an input of waste heat at temperatures below 100 °C. A salinity gradient drives water electrolysis in the reverse electrodialysis (RED) cell, and spent solutions are regenerated using waste heat in a precipitation or evaporation unit. This work presents a non-equilibrium thermodynamics model for the RED cell, and the hydrogen production is investigated for KCl/water solutions. The results show that the evaporation concept requires 40 times less waste heat and produces three times more hydrogen than the precipitation concept. With commercial evaporation technology, a system efficiency of 2% is obtained, with a hydrogen production rate of 0.38 gH2 m−2h−1 and a waste heat requirement of 1.7 kWh g−1H2. The water transference coefficient and the salt diffusion coefficient are identified as membrane properties with a large negative impact on hydrogen production and system efficiency. Each unit of the water transference coefficient in the range tw=[0–10] causes a −7 mV decrease in unit cell electric potential, and a −0.3% decrease in system efficiency. Increasing the membrane salt diffusion coefficient from 10−12 to 10−11 leads to the system efficiency decreasing from 2% to 0.6%
H2Safety@BAM
(2023)
This lecture describes the history of hydrogen from the first scientific discoveries in the 18th century to the current technological and political developments for the market ramp-up of hydrogen technologies. The European policy framework for safe hydrogen technologies is explained comprehending the European Green Deal, European Climate Law, European Hydrogen Strategy, Clean Hydrogen Partnership, etc. Safety in hydrogen technologies is governed by international and European regulations and standards. An overview on regulatory bodies, technical committees, regulations, directives, standards, and technical guidelines with special attention on the BAM-GGR 021 is given in this lecture.
The test data for static burst strength and load cycle fatigue strength of pressure vessels can often be well described by Gaussian normal or Weibull distribution functions. There are various approaches which can be used to determine the parameters of the Weibull distribution function; however, the performance of these methods is uncertain. In this study, six methods are evaluated by using the criterion of OSL (observed significance level) from Anderson-Darling (AD) goodness of Fit (GoF), These are: a) the norm-log based method, b) least squares regression, c) weighted least squares regression, d) a linear approach based on good linear unbiased estimators, e) maximum likelihood estimation and f) method of moments estimation. In addition, various approaches of ranking function are considered. The results show that there are no outperforming methods which can be identified clearly, primarily due to the limitation of the small sample size of the test data used for Weibull analysis. This randomness resulting from the sampling is further investigated by using Monte Carlo simulations, concluding that the sample size of the experimental data is more crucial than the exact method used to derive Weibull parameters. Finally, a recommendation is made to consider the uncertainties of the limitations due to the small size for pressure vessel testing and also for general material testing.
This lecture describes the history of hydrogen from the first scientific discoveries in the 18th century to the current technological and political developments for the market ramp-up of hydrogen technologies. The European policy framework for safe hydrogen technologies is explained comprehending the European Green Deal, European Climate Law, European Hydrogen Strategy, Clean Hydrogen Partnership, etc. Safety in hydrogen technologies is governed by international and European regulations and standards. An overview on regulatory bodies, technical committees, regulations, directives, standards, and technical guidelines with special attention on the BAM-GGR 021 is given in this lecture.
This lecture describes the history of hydrogen from the first scientific discoveries in the 18th century to the current technological and political developments for the market ramp-up of hydrogen technologies. The European policy framework for safe hydrogen technologies is explained comprehending the European Green Deal, European Climate Law, European Hydrogen Strategy, Clean Hydrogen Partnership, REPowerEU Plan, Renewable Energy Directive and its Delegated Act, Net Zero Industry Act, etc.
Green hydrogen is seen as a cornerstone of the energy transition and decarbonization efforts of industry, transportation and the utilities sectors. The binding goal of the EU and Germany to reduce net zero carbon emissions by 2045 will substantially increase the demand for green hydrogen as an important carbon-free substitute for fossil fuels. The World Energy Council expects an annual demand of 60 million tons (equivalent 2.000 TWh) hydrogen and its derivatives (especially ammonia and methanol) in the EU until 2050. lt is estimated that the EU can produce less than half of its needed hydrogen by 2050, and will need to import the rest. African coastal countries therefore have the opportunity to become net exporters of their carbon-free regenerative energy in the form of hydrogen and its derivatives and to enable better economic growth and generate wealth on the African continent. The large-scale production, transport and storage of green hydrogen will require large investments in the development of knowledge and training, logistics and capital goods - for both the EU and African countries.
BAM is already facing the lack of skilled workers and hydrogen experts. By bundling its expertise in the field of hydrogen technologies into a competence center H2Safety@BAM to create confidence in the technology The topic of hydrogen has been current at BAM for more than one hundred years and is also currently the focus of numerous research and cooperation activities. In order to transfer its expertise in this field BAM developed a number of education activities. The centre of all activities is the Graduate School “Trustworthy Hydrogen”, established in 2022 together with the BTU Cottbus. In the presentation all activities and especially those of the graduate school and details of the cooperation with the University of Namibia are shown.
Determination of Distribution Function used in MCS on Safety Analysis of Hydrogen Pressure Vessel
(2019)
The test data of static burst strength and load cycle strength of composite pressure vessels are often described by GAUSSian normal or WEIBULL distribution function to perform safety analyses. The goodness of assumed distribution function plays a significant role in the inferential statistics to predict the population properties by using limited test data. Often, GAUSSian and WEIBULL probability nets are empirical methods used to validate the distribution function; Anderson-Darling and Kolmogorov-Smirnov tests are the mostly favorable approaches for Goodness of Fit. However, the different approaches used to determine the parameters of distribution function lead mostly to different conclusions for safety assessments. In this study, six different methods are investigated to show the variations on the rates for accepting the composite pressure vessels according to GTR No. 13 life test procedure. The six methods are: a) Norm-Log based method, b) Least squares regression, c) Weighted least squares regression, d) A linear approach based on good linear unbiased estimators, e) Maximum likelihood estimation and f) The method of moments estimation. In addition, various approaches of ranking function are considered. In the study, Monte Carlo simulations are conducted to generate basic populations based on the distribution functions which are determined using different methods. Then the samples are extracted randomly from a population and evaluated to obtain acceptance rate. Here, the “populations” and “samples” are corresponding to the burst strength or load cycle strength of the pressure vessels made from composite material and a plastic liner (type 4) for the storage of hydrogen. To the end, the results are discussed, and the best reliable methods are proposed.
Degradation and damage analysis of composite pressure vessels via experimental modal analysis
(2023)
For mobile gas storage systems, the application of type IV pressure vessels is state of the art. Type IV tanks consist of an inner polymer liner fully wrapped with fibre-reinforced plastic (FRP). Because of the complex fabric of the FRP as well as a difficulty estimable interaction behaviour between the single components under load, there are still no satisfying non-destructive testing methods to assess the current state of failure nor to estimate the level of degradation accurately and economically. At BAM division 3.5, analysing the ageing process of mobile composite pressure vessels is a major task to ensure safe usage over the whole lifetime. In this context, key aspects of our ongoing research activities are the invention of new test procedures and the development of accurate lifetime prediction models. In order to determine the level of degradation or damage, one meaningful non-destructive approach is to analyse the structural dynamic behaviour via an experimental modal analysis (EMA). Over the last few years, different types and sizes of composite pressure vessels have been tested in several research projects. The presented paper gives an insight into how to extract and interpret modal parameters and how to fit them to the results of residual strength tests.
Degradation and damage analysis of composite pressure vessels via experimental modal analysis
(2023)
For mobile gas storage systems, the application of type IV pressure vessels is state of the art. Type IV tanks consist of an inner polymer liner fully wrapped with fibre-reinforced plastic (FRP). Because of the complex fabric of the FRP as well as a difficulty estimable interaction behaviour between the single components under load, there are still no satisfying non-destructive testing methods to assess the current state of failure nor to estimate the level of degradation accurately and economically. At BAM division 3.5, analysing the ageing process of mobile composite pressure vessels is a major task to ensure safe usage over the whole lifetime. In this context, key aspects of our ongoing research activities are the invention of new test procedures and the development of accurate lifetime prediction models. In order to determine the level of degradation or damage, one meaningful non-destructive approach is to analyse the structural dynamic behaviour via an experimental modal analysis (EMA). Over the last few years, different types and sizes of composite pressure vessels have been tested in several research projects. The presented paper gives an insight into how to extract and interpret modal parameters and how to fit them to the results of residual strength tests.
As a contribution to the national hydrogen strategy, 3.5 years ago, the Delfin research project started with the aim of developing a cost- and material-optimized hydrogen tank design for automotive application. Under the patronage of the National Organization Hydrogen and Fuel Cell Technology (NOW), a consortium consisting of 9 research institutes, component suppliers, engineering service providers and automobile OEMs is processing a wide range of work packages. The focus of BAM research sets on impact testing and safety-related characterization of pressure vessels of different development stages. Furthermore, the implementation of nondestructive testing methods is applied. The presentation shows an overview of the BAM work packages and an extraction of the results generated so far.
First the acceptance rates resulting from the analysis of different minimum burst ratios and standards are displayed and explained. Especially the problems resulting from a further reduction if the minimum burst ratio are shown.
For a better understanding of these results the process of analysing the acceptance rate is explained in detail. This contains the alleged contradiction between safety of samples due to its scatter while the rejected sample provides a higher mean strength.
Then the importance of batch testing is explained and leads to the recommendation to have a strong interaction between provided mean strength and requested maximum of production scatter.
Hydrogen is an attractive energy carrier that requires high effort for safe storage. Forensuring safety, they must undergo a challenging approval process. Relevant standardsand regulations for composite cylinders used for the transport of hydrogen and for its on-board storage are currently based on deterministic (e.g. ISO 11119-3) or semi-probabilistic(UN GTR No. 13) criteria. This paper analysis the properties of such methods withrespect to the evaluation of load cycle strength. Their characteristics are compared withthe probabilistic approach of the BAM. Based on Monte-Carlo simulations, the availabledesign range (mean value and scatter of strength criteria) of current concepts was exem-plarily estimated. The aspect of small sample sizes is analysed and discussed with respectto the evaluation procedures.
Competence Centre H2Safety@BAM – Safeguarding the Quality Infrastructure in the Hydrogen Economy
(2022)
Hydrogen is a central component of the energy transition and the European Green Deal for a climate-neutral Europe. To achieve the goals defined for 2050, the EU and the German government have developed a framework for action and are making long-term investments in research, development, and the rapid implementation of innovative hydrogen technologies.
With the Competence Centre "H2Safety@BAM", BAM is creating the safety-related prerequisites for the successful implementation of hydrogen technologies at national as well as European level.
To this end, BAM conducts research, testing and consulting in a holistic and inter-disciplinary manner under one roof – in the Competence Centre H2Safety@BAM. The activities of the competence centre focus on ensuring the safety of infra-structures, plants, and processes as well as innovative hydrogen transport and storage systems based on digital quality testing and the experimental testing of components and systems. It thus creates the prerequisites for the implementation and adaptation of legal framework conditions as well as for standardization. Closely related to this are investigations into the properties and compatibility of metallic materials and polymers as well as friction systems for the safe operation of components, plants, processes, and systems. This interdisciplinary and holistic approach is complemented by the development of gas analytics and suitable sensors, online measurements of gas properties in process control, test scenarios under real conditions as well as impact assessments of accidents and risk assessments and risk management systems derived from them. With its portfolio of tasks and competences, BAM builds trust in the safety and reliability of technical system solutions for hydrogen.
The Gases Advisory Group is organized regularly by the Prevention Division of the German Employer's Liability Insurance Association for Raw Materials and the Chemical Industry. The event serves as an exchange between science and industry on current safety-related issues concerning oxygen and hydrogen. In this context, BAM presented an overview of its various activities of the competence center H2Safety@BAM, which are reflected in the entire hydrogen value chain. In addition, the plans for the expansion of the test infrastructure at BAM's Technical Safety Test Site were presented. The results of the DELFIN project on the safety of pressurized gas storage tanks, the release tests of liquid hydrogen as well as the underfiring of corresponding cryogenic storage tanks and the plans for the ModuH2Pipe@BAM project were also presented. The presentation concluded with the current recommendations of the Hydrogen Research Network.
Dr Mair presents the competence centre “H2Safety@BAM”. He starts with a spectacular hydrogen accident on the Tempelhofer Feld (Berlin) in 1894, comes to the foundation of the competence centre in the context of the hydrogen strategies of Germany and the EU and explains their safety-focused orientation in order to create and maintain confidence in hydrogen technologies.
Beyond the long-term changes in energy supply, in Sept. 2022 there are enormous cost leaps in gas supply, which puts hydrogen as an energy carrier in a different light.
Based on this, he presents the structure of the Competence Centre with its 5 competence areas and the corresponding contact persons. This is underpinned by a slide on each of the work packages in the fields of competence.
At the end of the presentation, he explains the focus of the competence area "Component Testing, Component Safety and Approval", for which he is responsible. This is the question of cost reduction by using the whole potential of digitalisation in connection with the safety surveillance of the storage systems. The run of a fully digital system is of great importance for both, for the hydrogen supply of large consumers via road and rail and for storage systems in stationary plants. A robust and well-thought-out digitalisation in all levels of documentation will lead to a new quality in monitoring safety porperties, integration of new components and cost reduction.
Based on the preliminary presentations in this task force it is repeated how a basic population scatters and its degradation influences properties statistically. There is a remainder on the issue of accepting borderline populations due to the minimum burst ratio requirement.
Then it is explained in detail how the analysis of minimum requirements by a Monte-Carlo-simulation works. The result with respect to the further reduced minimum burst ratio of 2.0 is summarised and means a two-step approach of two scatter levels requiring two different minimum burst ratios.
The methods for evaluating batch tests are analysed. A proposal for integration a statistical analysis is described in detail.
Finally, the positive effect of proof testing is shown and its dependence from the real ageing is shown.
This ends in the recommendation to have a stronger and quantitative look on real ageing and to follow the 2 proposed sets of criteria for a safe usage of hydrogen storage systems.
The presentation starts with some key figures about BAM. Then it introduces BAM's competence centre H2Safety@BAM and shows aspects of special competence of the centre. It closes with information about the engagement of BAM in European research projects on hydrogen and a reference to our bilingual paper about our hydrogen strategy.
We analyse electromotive force measurements of concentration cells using non-equilibrium thermodynamics, and determine the transference coefficients of ion-exchange membranes in aqueous KCl solutions. By taking advantage of the analytical expression for the permselectivity, we extract transport coefficients with high accuracy. The transport number of K+ and the transference coefficient of water in the Selemion CMVN cationexchange membrane are found to be 100𝑡K+ = 99.59 ± 0.56 and 𝑡𝑤 = 3.69 ± 0.40 respectively, while for the Selemion AMVN anion-exchange membrane they are 100𝑡Cl− = 100.21 ± 0.37 and 𝑡𝑤 = −3.75 ± 0.27. These results suggest that the membranes are perfectly selective to the target ion, and that each ion carries 3-4 water molecules through the membrane, which reduces the membrane permselectivity. In these concentration cells, the electrical potential contribution of the membrane alone was more easily isolated with bare Ag/AgCl electrodes without reference solutions and liquid junction plugs. Additionally, we find a large contribution to the measured concentration cell voltage from concentration gradients across the porous plug of the reference electrode, which cannot be explained by Henderson’s equation alone. For most of the concentration range, the transport number of the porous plug is determined to be 100𝑡K+ = 49.43 ± 0.78 with negligible water transport, similar to literature values for bulk electrolyte. In dilute electrolyte solutions with concentrations below 0.1 mol kg−1, the plug shows anomalous behaviour consistent with an increase in K+ selectivity and water co-transport.