Publications

Two key aspects of hydrogen safety are (1) incorporating data and analysis from research development and demonstration (RD&D) into the codes and standards development process; and (2) adopting and enforcing these codes and standards by state and local permitting officials. This paper describes work that the U.S. Department of Energy (DOE) is sponsoring to address these aspects of hydrogen safety. For the first DOE is working with the automobile and energy industries to identify and address high priority RD&D to establish a sound scientific basis for requirements that are incorporated in hydrogen codes and standards. The high priority RD&D needs are incorporated and tracked in an RD&D Roadmap adopted by the Codes and Standards Technical Team of the FreedomCAR and Fuel Partnership. DOE and its national laboratories conduct critical RD&D and work with key standards and model code development organizations to help incorporate RD&D results into the codes and standards process. To address the second aspect DOE has launched an initiative to facilitate the permitting process for hydrogen fueling stations (HFS). A key element of this initiative will be a Web-based information repository a toolkit that includes information fact sheets networking charts to encourage information exchange among code officials who have permitted or are in the process of permitting HFS templates to show whether a proposed station footprint conforms to requirements in the jurisdiction and a database of requirements incorporated in key codes and standards. The information repository will be augmented by workshops for code officials and station developers in jurisdictions that are likely to have HFS in the near future.

The UK government has committed to reducing greenhouse gas emissions to net zero by 2050. All future energy modelling identifies a key role for hydrogen (linked to CCUS) in providing decarbonised energy for heat transport industry and power generation. Blending hydrogen into the existing natural gas pipeline network has already been proposed as a means of transporting low carbon energy. However the expectation is that a gas blend with maximum hydrogen content of 20 mol% can be used without impacting consumers’ end use applications. Therefore a transitional solution is needed to achieve a 100% hydrogen future network.

Deblending (i.e. separation of the blended gas stream) is a potential solution to allow the existing gas transmission and distribution network infrastructure to transport energy as a blended gas stream. Deblending can provide either hydrogen natural gas or blended gas for space heating transport industry and power generation applications. If proven technically and economically feasible utilising the existing gas transmission and distribution networks in this manner could avoid the need for investment in separate gas and hydrogen pipeline networks during the transition to a future fully decarbonised gas network.

The Energy Network Association (ENA) “Gas Goes Green” programme identifies deblending could play a critical role in the transition to a decarbonised gas network. Gas separation technologies are well-established and mature and have been used and proven in natural gas processing for decades. However these technologies have not been used for bulk gas transportation in a transmission and distribution network setting. Some emerging hydrogen separation technologies are currently under development. The main hydrogen recovery and purification technologies currently deployed globally are:

• Cryogenic separation
• Membrane separation
• Pressure Swing Adsorption (PSA)

The technologies noted above require an energy input to drive the separation of gas components in the form of compression to provide a pressure differential. The configuration of the GB gas transmission and distribution networks provides a possible source of available energy through the pressure let-down in the network pressure tiers which could be used to drive the gas component separation processes. This study evaluated the gas separation technologies noted above against a selection of case studies based on actual network operating conditions to assess the technical andeconomic feasibility of hydrogen deblending in the GB gas network context. This study constitutes the first stage (proof of concept) in a programme of works that should provide the critical evidence for hydrogen deblending as a necessary component to enable the use of GB gas networks to transport and distribute hydrogen.

This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.

Uptake of hydrogen vehicles is an ideal solution for countries that face challenging targets for carbon dioxide reduction. The advantage of hydrogen fuel cell electric vehicles is that they behave in a very similar way to petrol engines yet they do not emit any carbon containing products during operation. The hydrogen industry currently faces the dilemma that they must meet certain measurement requirements (set by European legislation) but cannot do so due to a lack of available methods and standards. This paper outlines the four biggest measurement challenges that are faced by the hydrogen industry including flow metering quality assurance quality control and sampling.

The purpose of the experimental work is to determine the conditions for which an enclosure can guest a fuel cell for civil use. Concerning the installation permitting guide this study allows the safe use of the fuel cell in case of small not catastrophic leakages. In fact the correct plan of the vents in the enclosure guarantees the low concentration of hydrogen (H2) below the LFL.

The formation of a flammable hydrogen-air mixture is a major safety concern especially for closed space. This hazardous situation can arise when considering permeation from a car equipped with a composite compressed hydrogen tank with a non-metallic liner in a closed garage. In the following paper a scenario is developed and analysed with a simplified approach and a numerical simulation in order to estimate the evolution of hydrogen concentration. The system is composed of typical size garage and hydrogen car’s tank. Some parameters increasing permeation rate (i.e. tank’s material thickness and pressure) have been chosen to have a conservative approach. A close look on the top of tank surface showed that the concentration grows as square root of time and does not exceed 8.2×10-3 % by volume. Also a simplified comparative analysis estimated that the buoyancy of hydrogen-air mixture prevails on the diffusion 35 seconds after permeation starts in good agreement with simulation where time is at about 80 seconds. Finally the numerical simulations demonstrated that across the garage height the hydrogen is nearly distributed linearly and the difference in hydrogen concentration at the ceiling and floor is negligible (i.e. 3×10-3 %).

For large-scale distribution and use of energy carriers classified as hazardous material in many countries as a method to assist land use planning to grant licenses to design a safe installation and to operate it safely some form of risk analysis and assessment is applied. Despite many years of experience the methods have still their weaknesses even the most elaborated ones as e.g. shown by the large spread in results when different teams perform an analysis on a same plant as was done in EU projects. Because a fuel as hydrogen with its different properties will come new in the daily use of many people incidents may happen and risks will be discussed. HySafe and other groups take good preparatory action in this respect and work in the right direction as appears from various documents produced. However already a superficial examination of the results so far tells that further cooperative work is indispensable. To avoid criticism skepticism and frustration not only the positive findings should be described and general features of the methods but the community has also to give strong guidance with regard to the uncertainties. Scenario development appears to be very dependent on insight and experience of an individual analyst leak and ignition probability may vary over a wide range of values Computational Fluid Dynamics or CFD models may lead to very different result. The Standard Benchmark Exercise Problems SBEPs are a good start but shall produce guidelines or recommendations for CFD use or even perhaps certification of models. Where feasible narrowing of possible details of scenarios to the more probable ones taking into account historical incident data and schematizing in bowties more explicit use of confidence intervals on e.g. failure rates and ignition probability estimates will help. Further knowledge gaps should be defined.

At least once air filling a piping from main hydrogen pipe line to an individual home end should be replaced with hydrogen gas to use the gas in the home. Special attention is required to complete the replacing operation safely because air and supplied hydrogen may generate flammable/explosive gas mixture in the piping. The most probable method to fulfill the task is that at first an inert gas is used to purge air from the piping and then hydrogen will be supplied into the piping. It is easily understood that the amount of the inert gas consumed by this method is much to purge whole air especially in long piping system. Hence to achieve more economical efficiency an alternative method was considered. In this method previously injected nitrogen between air and hydrogen prevents them from mixing. The key point is that how much nitrogen is required to prevent the dangerous mixing and keep the condition in the piping safe. The authors investigated to find the minimum amount of nitrogen required to keep the replacing operation safe. The main objective of this study is to assess the effect of nitrogen and estimate a pipe length that the safety is maintained under various conditions by using computational fluid dynamic (CFD). The effects of the amount of injected nitrogen hydrogen-supply conditions and the structure of piping system are discussed.

In the present work the computational fluid dynamics (CFD) code ADREA-HF has been applied to simulate the very recent liquefied hydrogen spill experiments performed by the Health Safety Laboratory (HSL). The experiment consists of four LH2 release trials over concrete at a fixed rate of 60 lt/min but with different release direction height and duration. In the modeling the hydrogen source was treated as a two phase jet enabling simultaneous modeling of pool formation spreading as well as hydrogen vapor dispersion. Turbulence was modeled with the standard k- model modified for buoyancy effects. The effect of solidification of the atmospheric humidity was taken into account. The predicted concentration at the experimental sensors? locations was compared with the observed one. The results from the comparison of the predicted concentration with and without solidification of the atmospheric humidity indicate that the released heat from the solidification affects significantly the buoyant behavior of the hydrogen vapor. Therefore the simulation with solidification of the atmospheric humidity is in better agreement with the experiment.

In the last years different Italian hydrogen projects provided for gaseous hydrogen motor vehicles refuelling stations. Motivated by the lack of suitable set of rules in the year 2002 Italian National Firecorps (Institute under the Italian Ministry of the Interior) formed an Ad Hoc Working Group asked to regulate the above-said stations as regards fire prevention and protection safety. This Working Group consists of members coming from both Firecorps and academic world (Pisa University). Throughout his work this Group produced a technical rule covering the fire prevention requirements for design construction and operation of gaseous hydrogen refuelling stations. This document has been approved by the Ministry’s Technical Scientific Central Committee for fire prevention (C.C.T.S.) and now it has to carry out the “Community procedure for the provision of information”. This paper describes the main safety contents of the technical rule.

About 20 years ago Fraunhofer ICT has performed large scale experiments with premixed hydrogen air mixtures [1]. A special feature has been the investigation of the combustion of the mixture within a partial confinement simulating some sort of a “lane” which may exist in reality within a hydrogen production or storage plant for example. Essentially three different types of tests have been performed: combustion of quiescent mixtures combustion of mixtures with artificially generated turbulence by means of a fan and combustion of mixtures with high speed flame jet ignition. The observed phenomena will be discussed on the basis of measured turbulence levels flame speeds and overpressures. Conditions for DDT concerning critical turbulence levels and flame speeds as well as a scaling rule for DDT related to the detonation cell size of the mixture can be derived from the experiments for this special test setup. The relevance of the results with respect to safety aspects of future hydrogen technology is assessed. Combustion phenomena will be highlighted by the presentation of impressive high speed film videos.