Greece

In the course towards a safe future hydrogen based society one of the tasks to be considered is the investigation of the conditions under which the use or storage of hydrogen systems inside buildings becomes too dangerous to be accepted. One of the relevant scenarios which is expected to have a relatively high risk is a slow (and long lasting) hydrogen release from a vehicle stored in a closed private garage without any forced ventilation i.e. only with natural ventilation. This scenario has been earlier investigated experimentally (by M. Swain) using He (helium) to simulate the hydrogen behavior. In the present work the CFD code ADREA-HF is used to simulate three of the abovementioned experiments using the standard k-  turbulence model. For each case modeled the predicted concentration (by vol.) time series are compared against the experimental at the given sensor locations. In addition the structure of the flow is investigated by presenting the helium concentration field.

The paper presents an overview of the main results of the EC NOE HySafe activity to estimate an allowable hydrogen permeation rate for automotive legal requirements and standards. The work was undertaken as part of the HySafe internal project InsHyde.<br/>A slow long term hydrogen release such as that due to permeation from a vehicle into an inadequately ventilated enclosed structure is a potential risk associated with the use of hydrogen in automotive applications. Due to its small molecular size hydrogen permeates through the containment materials found in compressed gaseous hydrogen storage systems and is an issue that requires consideration for containers with non-metallic (polymer) liners. Permeation from compressed gaseous hydrogen storage systems is a current hydrogen safety topic relevant to regulatory and standardisation activities at both global and regional levels.<br/>Various rates have been proposed in different draft legal requirements and standards based on different scenarios and the assumption that hydrogen dispenses homogeneously. This paper focuses on the development of a methodology by HySafe Partners (CEA NCSRD. University of Ulster and Volvo Technology) to estimate an allowable upper limit for hydrogen permeation in automotive applications by investigating the behaviour of hydrogen when released at small rates with a focus on European scenario. The background to the activity is explained. reasonable scenarios are identified a methodology proposed and a maximum hydrogen permeation rate from road vehicles into enclosed structures is estimated The work is based on conclusions from the experimental and numerical investigations described by CEA NCSRD and the University of Ulster in related papers.

The “SUpport to SAfety aNAlysis of Hydrogen and Fuel Cell Technologies (SUSANA)” project aims to support stakeholders using Computational Fluid Dynamics (CFD) for safety engineering design and assessment of FCH systems and infrastructure through the development of a model evaluation protocol. The protocol covers all aspects of safety assessment modelling using CFD from release through dispersion to combustion (self-ignition fires deflagrations detonations and Deflagration to Detonation Transition - DDT) and not only aims to enable users to evaluate models but to inform them of the state of the art and best practices in numerical modelling. The paper gives an overview of the SUSANA project including the main stages of the model evaluation protocol and some results from the on-going benchmarking activities.

To develop safety strategies for the use of hydrogen indoors the HyIndoor project is studying the behaviour of a hydrogen release deflagration or non-premixed flame in an enclosed space such as a fuel cell or its cabinet a room or a warehouse. The paper proposes a safety approach based on safety objectives that can be used to take various scenarios of hydrogen leaks into account for the safe design of Hydrogen and Fuel Cell (HFC) early market applications. Knowledge gaps on current engineering models and unknown influence of specific parameters were identified and prioritized thereby re-focusing the objectives of the project test campaign and numerical simulations. This approach will enable the improvement of the specification of openings and use of hydrogen sensors for enclosed spaces. The results will be disseminated to all stakeholders including hydrogen industry and RCS bodies.

Purpose- To present an overview of the research and development carried out in a European funded framework 7 (FP7) project called SafeHPower for the implementation of neutron radiography to inspect fatigue cracks in vehicle and storage hydrogen fuel tanks. Project background– Hydrogen (H2) is the most promising replacement fuel for road transport due to its abundance efficiency low carbon footprint and the absence of harmful emissions. For the mass market of hydrogen to take off the safety issue surrounding the vehicle and storage hydrogen tanks needs to be addressed. The problem is the residual and additional stresses experienced by the tanks during the continuous cyclic loading between ambient and storage pressure which can result in the development of fatigue cracks. Steel tanks used as storage containers at service stations and depots and/or the composite tanks lined with steel are known to suffer from hydrogen embrittlement (HE). Another issue is the explosive nature of hydrogen (when it is present in the 18-59% range) where it is mixed with oxygen which can lead to catastrophic consequences including loss of life. Monitoring systems that currently exist in the market impose visual examination tests pressure tests and hydrostatic tests after the tank installation [1] [2]. Three inspection systems have been developed under this project to provide continuous monitoring solutions. Approach and scope- One of the inspection systems based on the neutron radiography (NR) technology that was developed in different phases with the application of varied strategies has been presented here. Monte Carlo (MCNP) simulation results to design and develop a bespoke collimator have been presented. A limitation of using an inertial electrostatic Deuterium-Tritium (D-T) pulsed neutron generator for fast neutron radiography has been discussed. Radiographs from the hydrogen tank samples obtained using thermal neutrons from a spallation neutron source at ISIS Rutherford laboratory UK have been presented. Furthermore radiograph obtained using thermal neutrons from a portable D-T neutron generator has been presented. In conclusion a proof in principle has been made to show that the defects in the hydrogen fuel tank can be detected using thermal neutron radiography.

A multi-scale modeling approach for simulating the tensile behavior of the corroded aluminum alloy 2024 T3 was developed accounting for both the geometrical features of corrosion damage and the effect of corrosion-induced hydrogen embrittlement (HE). The approach combines two Finite Element (FE) models: a model of a three-dimensional Representative Unit Cell (RUC) representing an exfoliated area and its correspondent hydrogen embrittled zone (HEZ) and a model of the tensile specimen. The models lie at the micro- and macro-scales respectively. The characteristics of the HEZ are determined from measurements of nanoindentation hardness conducted on pre-corroded specimens. Using the model of the RUC the local homogenized mechanical behavior of the corroded material is simulated. Then the behavior of the exfoliated areas is assigned into different areas (elements) of the tensile specimen and final analyses are performed to simulate the tensile behavior of the corroded material. The approach was applied to model specimens after 8 16 and 24 h exposure periods of the Exfoliation Corrosion (EXCO) test. For validation of the approach tensile tests were used. The numerical results show that this approach is suitable for accurately simulating the tensile behavior of pre-corroded experimental specimens accounting for both geometrical features of corrosion damage and corrosion-induced HE.

Globally the accelerating use of renewable energy sources enabled by increased efficiencies and reduced costs and driven by the need to mitigate the effects of climate change has significantly increased research in the areas of renewable energy production storage distribution and end-use. Central to this discussion is the use of hydrogen as a clean efficient energy vector for energy storage. This review by experts of Task 32 “Hydrogen-based Energy Storage” of the International Energy Agency Hydrogen TCP reports on the development over the last 6 years of hydrogen storage materials methods and techniques including electrochemical and thermal storage systems. An overview is given on the background to the various methods the current state of development and the future prospects. The following areas are covered; porous materials liquid hydrogen carriers complex hydrides intermetallic hydrides electro-chemical storage of energy thermal energy storage hydrogen energy systems and an outlook is presented for future prospects and research on hydrogen-based energy storage

Electrifying transportation is a promising approach to alleviate climate change issues arising from increased emissions. This study examines a system for the production of hydrogen using renewable energy sources as well as its use in buses. The electricity requirements for the production of hydrogen through the electrolysis of water are covered by renewable energy sources. Fuel cells are being used to utilize hydrogen to power the bus. Exergy analysis for the system is carried out. Based on a steady-state model of the processes exergy efficiencies are calculated for all subsystems. The subsystems with the highest proportion of irreversibility are identified and compared. It is shown that PV panel has exergetic efficiency of 12.74% wind turbine of 45% electrolysis of 67% and fuel cells of 40%.

An  inter-comparison  among  partners’  CFD  simulations  has  been  carried  out  within  the  EU-funded project PRESLHY to investigate the dispersion of the mixture cloud formed from large scale liquid hydrogen release. Rainout experiments performed by Health and Safety Executive (HSE) have been chosen for the work. From the HSE experimental series trial-11 was selected forsimulation due to its conditions where  only  liquid  flow  at  the  nozzle  was  achieved.   During  trial-11  liquid  hydrogen  is spilled horizontally 0.5 m above a concrete pad from a 5 barg tank pressure through a 12 mm (1/2 inch) nozzle. The dispersion takes place outdoors and thus it is imposed to variant wind conditions. Comparison  of  the  CFD  results  with  the   measurements  at  several  sensors  is  presented  and  useful conclusions are drawn.

In the framework of the EU-funded project HyTunnel-CS an inter-comparison among partners CFD simulations  has  been  carried  out.  The simulations  are  based  on  experiments  conducted   within  the project by Pro-Science and involve hydrogen release inside a safety vessel testing different ventilation configurations. The different ventilation configurations that were tested are co-flow counter-flow and cross-flow.  In the  current  study  co-flow  and  counter-flow  tests   along  with  the  no  ventilation  test (m'  = S g/s  d = 4 mm ) are simulated with the aim to validate available and well-known CFD codes against  such  applications  and  to  provide   recommendations  on  modeling  strategies. Special  focus  is given on modeling the velocity field produced by the fan during the experiments. The computational results are compared with the experimental results and a discussion follows regarding the efficiency of each ventilation configuration.