Publications

Spontaneous ignition processes due to the high-pressure hydrogen releases into air were investigated both experimentally and theoretically. Such processes reproduce accident scenarios of sudden expansion of pressurized hydrogen into the ambient atmosphere in cases of tube or valve rupture. High-pressure hydrogen releases in the range of initial pressures from 20 to 275 bar and with nozzle diameters of 0.5 – 4 mm have been investigated. Glass tubes and high-speed CCD camera were used for experimental study of self-ignition process. The problem was theoretically considered in terms of contact discontinuity for the case when spontaneous ignition of pressurized hydrogen due to the contact with hot pressurized air occurs. The effects of boundary layer and material properties are discussed in order to explain the minimum initial pressure of 25 bar leading to the self-ignition of hydrogen with air.

Hydrogen behavior at elevated pressures and temperatures was intensively studied by numerous investigators. Nevertheless there is a lack of experimental data on hydrogen ignition and combustion at reduced sub-atmospheric pressures. Such conditions are related to the facilities operating under vacuum or sub-atmospheric conditions for instance like ITER vacuum vessel. Main goal of current work was an experimental evaluation of such fundamental properties of hydrogen–air mixtures as flammability limits and laminar flame speed at sub-atmospheric pressures. A spherical explosion chamber with a volume of 8.2 dm3 was used in the experiments. A pressure method and high-speed camera combined with schlieren system for flame visualization were used in this work. Upper and lower flammability limits and laminar flame velocity have been experimentally evaluated in the range of 4–80% hydrogen in air at initial pressures 25–1000 mbar. An extraction of basic flame properties as Markstein length overall reaction order and activation energy was done from experimental data on laminar burning velocity.

This report sets out our advice on the fifth carbon budget covering the period 2028-2032 as required under Section 4 of the Climate Change Act; the Government will propose draft legislation for the fifth budget in summer 2016.

This report by the Committee on Climate Change (CCC) assesses the potential role of hydrogen in the UK’s low-carbon economy.

It finds that hydrogen:

• is a credible option to help decarbonise the UK energy system but its role depends on early Government commitment and improved support to develop the UK’s industrial capability
• can make an important contribution to long-term decarbonisation if combined with greater energy efficiency cheap low-carbon power generation electrified transport and new ‘hybrid’ heat pump systems which have been successfully trialled in the UK
• could replace natural gas in parts of the energy system where electrification is not feasible or is prohibitively expensive for example in providing heat on colder winter days industrial heat processes and back-up power generation
• is not a ‘silver bullet’ solution; the report explores some commonly-held misconceptions highlighting the need for careful planning

The report’s key recommendations are:

• Government must commit to developing a low-carbon heat strategy within the next three years
• Significant volumes of low-carbon hydrogen should be produced in a carbon capture and storage (CCS) ‘cluster’ by 2030 to help the industry grow
• Government must support the early demonstration of the everyday uses of hydrogen in order to establish the practicality of switching from natural gas to hydrogen
• There is low awareness amongst the general public of reasons to move away from natural gas heating to low-carbon alternatives
• A strategy should be developed for low-carbon heavy goods vehicles (HGVs) which encourages a move away from fossil fuels and biofuels to zero-emission solutions by 2050

This report for the CCC by Madano and Element Energy assesses the public acceptability of two alternative low-carbon technologies for heating the home: hydrogen heating and heat pumps.

These technologies could potentially replace natural gas in many UK households as part of the government’s efforts to decrease carbon emissions in the UK.

The report’s key findings are:

• carbon emissions reduction is viewed as an important issue but there is limited awareness of the need to decarbonise household heating or the implications of switching over to low-carbon heating technologies
• acceptability of both heating technologies is limited by a lack of perceived tangible consumer benefit which has the potential to drive scepticism towards the switch over more generally
• heating technology preferences are not fixed at this stage although heat pumps appear to be the favoured option in this research studythree overarching factors were identified as influencing preferences for heating technologies.

These factors manifested differently for different people meaning that the same factor could lead one person to prefer heat pumps and another to prefer hydrogen depending on their overall heating preferences and understanding of the two technologies. The factors are:

• perceptions of the negative installation burden
• familiarity with the lived experience of using the technologies for heating
• perceptions of how well the technologies would meet modern heating needs both hydrogen heating and heat pumps face significant challenges to secure public acceptability

The EC 6th framework research project HyApproval will draft a Handbook which will describe all relevant issues to get approval to construct and operate a Hydrogen Refuelling Station (HRS) for hydrogen vehicles. In WP3 of the HyApproval project it is under investigation which safety information competent authorities require to give a licence to construct an operate an HRS. The paper describes the applied methodology to collect the information from the authorities in 5 EC countries and the USA. The results of the interviews and recommendations for the information to include in the Handbook are presented.

We prepared several gas barrier resins based on amorphous PVA derivative that has the T1C (13C spin-lattice relaxation time) of a long time component in amorphous phase. We confirmed it was important to control state in amorphous phase of gas barrier resin in order to achieve both moldability and good gas barrier property. Polymer alloy was designed to improve flexibility. Polymer alloy made of amorphous PVA and elastomer resin showed good hydrogen resistance. Even after its polymer alloy were repeatedly exposed to 70MPa hydrogen gas the influence on higher-order structure in amorphous phase was in negligible level.

This paper discusses the results of computational fluid dynamics (CFD) modelling of hydrogen releases and dispersion outdoors during venting of hydrogen storage in real environment and geometry of a hydrogen refuelling or energy station for a given flow rate and dimensions of vent stack. The PHOENICS CFD software package was used to solve the continuity momentum and concentration equations with the appropriate boundary conditions buoyancy model and turbulence models. Also thermal effects resulting from potential ignition of flammable hydrogen clouds were assessed using TNO “Yellow Book” recommended approaches. The obtained results were then applied to determine appropriate clearance distances for venting of hydrogen storage for contribution to code development and station design considerations. CFD modelling of hydrogen concentrations and TNO-based modelling of thermal effects have proven to be reliable effective and relatively inexpensive tools to evaluate the effects of hydrogen releases.

This is the CCC’s eighth annual report on the UK’s progress in meeting carbon budgets.

The report shows that greenhouse gas emissions have fallen rapidly in the UK power sector but that progress has stalled in other sectors such as:

• heating in buildings
• transport
• industry
• agriculture

The report also outlines the Committee’s view of key criteria for the government’s ’emissions reduction plan’ published later in 2017

Hydrogen is one of the important alternative fuels for future transportation. At the present stage research into hydrogen safety and designing risk mitigation measures are significant task. For compact storage of hydrogen in fuel cell vehicles storage of hydrogen under high pressure up to 40 MPa at refuelling stations is planned and safety in handling such high-pressure hydrogen is essential. This paper describes our experimental investigation into dispersion of high-pressure hydrogen gas which leaks through pinholes in the piping to the atmosphere. First in order to comprehend the basic behaviour of the steady dispersion of high-pressure hydrogen gas from the pinholes the time-averaged concentrations were measured. In our experiments initial release pressures of hydrogen gas were set at 20 MPa or 40 MPa and release diameters were in the range from 0.25 mm to 2 mm. The experimental results show that the hydrogen concentration along the axis of the dispersion plume can be expressed as a simple formula which is a function of the downwind distance X and the equivalent release diameter. This formula enables us to easily estimate the axial concentration (maximum concentration) at each downstream distance. However in order for the safety of flammable gas dispersion to be analyzed comparisons between time-averaged concentrations evaluated as above and lower flammable limit are insufficient. This is because even if time-averaged concentration is lower than the flammability limit instantaneous concentrations fluctuate and a higher instantaneous concentration occasionally appears due to turbulence. Therefore the time-averaged concentration value which can be used as a threshold for assessing safety must be determined considering concentration fluctuations. Once the threshold value is determined the safe distance from the leakage point can be evaluated by the above-mentioned simple formula. To clarify the phenomenon of concentration fluctuations instantaneous concentrations were measured with the fast-response flame ionization detector. A small amount of methane gas was mixed into the hydrogen as a tracer gas for this measurement. The relationship between the time-mean concentration and the occurrence probability of flammable concentration was analyzed. Under the same conditions spark-ignition experiments were also conducted and the relationship between the occurrence probability of flammable concentration and actual ignition probabilities were also investigated. The experimental results show that there is a clear correlation between the time-mean concentration the occurrence probability of flammable concentration flame length and occurrence probability of hydrogen flame.

Hydrogen is seen as the future automobile energy storage media due to its inherent cleanliness upon oxidation and its ready utilization in fuel cell applications. Its physical storage in light weight low volume systems is a key technical requirement. In searching for ever higher gravimetric and volumetric density hydrogen storage materials and systems it is inevitable that higher energy density materials will be studied and used. To make safe and commercially acceptable systems it is important to understand quantitatively the risks involved in using and handling these materials and to develop appropriate risk mitigation strategies to handle unforeseen accidental events. To evaluate these materials and systems an IPHE sanctioned program was initiated in 2006 partnering laboratories from Europe North America and Japan. The objective of this international program is to understanding the physical risks involved in synthesis handling and utilization of solid state hydrogen storage materials and to develop methods to mitigate these risks. This understanding will support ultimate acceptance of commercially high density hydrogen storage system designs. An overview of the approaches to be taken to achieve this objective will be given. Initial experimental results will be presented on environmental exposure of NaAlH4 a candidate high density hydrogen storage compound. The tests to be shown are based on United Nations recommendations for the transport of hazardous materials and include air and water exposure of the hydride at three hydrogen charge levels in various physical configurations. Additional tests developed by the American Society for Testing and Materials were used to quantify the dust cloud ignition characteristics of this material which may result from accidental high energy impacts and system breach. Results of these tests are shown along with necessary risk mitigation techniques used in the synthesis and fabrication of a prototype hydrogen storage system.

In this document after a review of the accidents/incidents are described the different interactions between hydrogen gas and the most commonly used materials including the influence of "internal" and "external" hydrogen the phenomena occurring in all ranges of temperatures and pressures and Hydrogen Embrittlement (HE) created by gaseous hydrogen. The principle of all the test methods used to investigate this phenomenon are presented and discussed. The advantages and disadvantages of each method will be explained. The document also covers the influence of all the parameters related to HE including the ones related to the material itself the ones related to the design and manufacture of the equipment and the ones related to the hydrogen itself (pressure temperature purity etc). Finally recommendations to avoid repetition of accidents/incidents mentioned before are proposed.

Because of the increasing challenges raised by climate change power generation from renewable energy sources is steadily increasing to reduce greenhouse gas emissions especially CO2 . However this has escalated concerns about the instability of the power grid and surplus power generated because of the intermittent power output of renewable energy. To resolve these issues this study investigates two technical options that integrate a power-to-gas (PtG) process using surplus wind power and the gas turbine combined cycle (GTCC). In the first option hydrogen produced using a power-to-hydrogen (PtH) process is directly used as fuel for the GTCC. In the second hydrogen from the PtH process is converted into synthetic natural gas by capturing carbon dioxide from the GTCC exhaust which is used as fuel for the GTCC. An annual operational analysis of a 420-MWclass GTCC was conducted which shows that the CO2 emissions of the GTCC-PtH and GTCC-PtM plants could be reduced by 95.5% and 89.7% respectively in comparison to a conventional GTCC plant. An economic analysis was performed to evaluate the economic feasibility of the two plants using the projected cost data for the year 2030 which showed that the GTCC-PtH would be a more viable option.

The transition period towards the situation in which hydrogen will become an important energy carrier will be lengthy (decades) costly and needs a significant R&D effort. It’s clear therefore that the development of a hydrogen system requires a practical strategy within the context of the existing assets. Examining the potential of the existing extensive natural gas chain (transmission - distribution - end user infrastructures and appliances) is a logical first step towards the widespread delivery of hydrogen.

The project will define the conditions under which hydrogen can be mixed with natural gas for delivery by the existing natural gas system and later withdrawn selectively from the pipeline system by advanced separation technologies. Membranes will be developed to enable this separation. The socio-economic and life cycle consequences of this hydrogen delivery approach will be mapped out. By adding hydrogen to natural gas the physical and chemical properties of the mixture will differ from “pure” natural gas. As this may have a major effect on safety issues and durability issues (which also have a safety component) related to the gas delivery and the performance of end use appliances these issues are particularly addressed in the project.

The project is executed by a European consortium of 39 partners (including 15 from the gas industry). In this project set up under the auspices of GERG The European Gas Research Group there are leading roles for N.V. Nederlandse Gasunie (NL) Gaz de France (F) TNO (NL) ISQ (P) the Universities of Loughborough and Warwick (UK) and Exergia (GR). Guidance will be provided by a Strategic Advisory Committee consisting of representatives from relevant (inter)national organizations.

The project started on 1st May 2004 and will run for 5 years. The European Commission has selected the Integrated Project NATURALHY for financial support within the Sixth Framework Programme.

A review of the effect of hydrogen on materials is addressed in this paper. General aspects of the interaction of hydrogen and materials hydrogen embrittlement low temperature effects material suitability for hydrogen service and materials testing are the main subjects considered in the first part of the paper. As a particular case of the effect of hydrogen in materials the hydride formation of titanium alloys is considered. Alpha titanium alloys are considered corrosion resistant materials in a wide range of environments. However hydrogen absorption and the possible associated problems must be taken into account when considering titanium as a candidate material for high responsibility applications. The sensitivity of three different titanium alloys Ti Gr-2 Ti Gr-5 and Ti Gr-12 to the Hydrogen Assisted Stress Cracking phenomena has been studied by means of the Slow Strain Rate Technique (SSRT). The testing media has been sea water and hydrogen has been produced on the specimen surface during the test by cathodic polarization. Tested specimens have been characterized by metallography and scanning electron microscopy. Results obtained show that the microstructure of the materials particularly the β phase content plays an important role on the sensitivity of the studied alloys to the Hydrogen Assisted Stress Cracking Phenomena.

Hydrogen technology requires efficient and safe hydrogen storage systems. For this purpose storage in solid materials such as high capacity complex hydrides is studied intensely. Independent from the actual material to be used eventually any tank design will combine nanoscale powders of highly reactive material with pressurized hydrogen gas and so far little is known about the behaviour of these mixtures in case of incidents. For a first evaluation of a complex hydride in case of a tank failure NaAlH4 (doped with Ti) was investigated in a small scale tank failure tests. 80-100 ml of the material were filled into a heat exchanger tube and sealed under argon atmosphere with a burst disk. Subsequently the NaAlH4 was partially desorbed by heating. When the powder temperature reached 130 °C and the burst disk ruptured at 9 bar hydrogen overpressure the behaviour of the expelled powder was monitored using a high speed camera an IR camera as well as sound level meters. Expulsion of the hydrogen storage material into (dry) ambient atmosphere yields a dust cloud of finely dispersed powder which does not ignite spontaneously. Similar experiments including an external source of ignition (spark / water reacting with NaAlH4) yield a flame of reacting powder. The intensity will be compared to the reaction of an equivalent amount of pure hydrogen.

Polymer electrolyte membrane (PEM) water electrolysis has demonstrated its potentialities in terms of cell efficiency (energy consumption ≈ 4.0-4.2 kW/Nm3 H2) and gas purity (> 99.99% H2). Current research activities are aimed at increasing operating pressure up to several hundred bars for direct storage of hydrogen in pressurized vessels. Compared to atmospheric pressure electrolysis high-pressure operation yields additional problems especially with regard to safety considerations. In particular the rate of gases (H2 and O2) cross-permeation across the membrane and their water solubility both increase with pressure. As a result gas purity is affected in both anodic and cathodic circuits and this can lead to the formation of explosive gas mixtures. To prevent such risks two different solutions reported in this communication have been investigated. First the chemical modification of the solid polymer electrolyte in order to reduce cross-permeation phenomena. Second the use of catalytic H2/O2 recombiners to maintain H2 levels in O2 and O2 levels in H2 at values compatible with safety requirements.

Simulation of hydrogen-air mixture explosions in a closed large-scale vessel with uniform and nonuniform mixture compositions was performed by the group of partners within the EC funded project “Hydrogen Safety as an Energy Carrier” (HySafe). Several experiments were conducted previously by Whitehouse et al. in a 10.7 m3 vertically oriented (5.7-m high) cylindrical facility with different hydrogen-air mixture compositions. Two particular experiments were selected for simulation and comparison as a Standard Benchmark Exercise (SBEP) problem: combustion of uniform 12.8% (vol.) hydrogen-air mixture and combustion of non-uniform hydrogen-air mixture with average 12.6% (vol.) hydrogen concentration across the vessel (vertical stratification 27% vol. hydrogen at the top of the vessel 2.5% vol. hydrogen at the bottom of the vessel); both mixtures were ignited at the top of the vessel. The paper presents modelling approaches used by the partners comparison of simulation results against the experiment data and conclusions regarding the non-uniform mixture combustion modelling in real-life applications.

A best practice is a technique or methodology that has reliably led to a desired result. A wealth of experience regarding the safe use and handling of hydrogen exists as a result of an extensive history in a wide variety of industrial and aerospace settings. Hydrogen Safety Best Practices (www.h2bestpractices.org) captures this vast knowledge base and makes it publicly available to those working with hydrogen and related systems including those just starting to work with hydrogen. This online manual is organized under a number of hierarchical technical content categories. References including publications and other online links that deal with the safety aspects of hydrogen are compiled for easy access. This paper discusses the development of Hydrogen Safety Best Practices as a safety knowledge tool the nature of its technical content and the steps taken to enhance its value and usefulness. Specific safety event examples are provided to illustrate the link between technical content in the online best practices manual and a companion safety knowledge tool Hydrogen Incident Reporting and Lessons Learned (www.h2incidents.org) which encourages the sharing of lessons learned and other safety event information.

Correct selection and application of materials is essential to ensure safety and economy in production transportation and storage of hydrogen. There are several sources of materials challenges related to hydrogen. Established component producers may have limited experience in this specific field. Process developments may involve new process conditions with new demands on the materials. Further new materials will be added to the engineering toolbox to be used. The behaviour of these materials for hydrogen service may need additional documentation. Finally focus on hydrogen susceptibility and hydrogen damages alone may take away awareness of other subjects as trace elements by-products and change in raw materials which may be of as high importance for safety and quality. This overview of challenges and recommendations is made with emphasis on water electrolysis.

This paper is concerned with predicting the impact on the probability of failure of adding hydrogen to the natural gas distribution network. Hydrogen has been demonstrated to change the behaviour of crack like defects which may affect the safety of pipeline or make it more expensive to operate. A tool has been developed based on a stochastic approach to assess the failure probability of the gas pipeline due to the existence of crack-lie defects including the operational aspects of the pipeline such as inspection and repair procedures. With various parameters such as crack sizes material properties internal pressure modelled as uncertainties a reliability analysis based on failure assessment diagram is performed through direct Monte Carlo simulation. Inspection and repair procedures are included in the simulation to enable realistic pipeline maintenance scenarios to be simulated. In the data preparation process the accuracy of the probabilistic definition of the uncertainties is crucial as the results are very sensitive to certain variables such as the crack depth length and crack growth rate. The failure probabilities of each defect and the whole pipeline system can be obtained during simulation. Different inspection and repair criteria are available in the Monte Carlo simulation whereby an optimal maintenance strategy can be obtained by comparing different combinations of inspection and repair procedures. The simulation provides not only data on the probability of failure but also the predicted number of repairs required over the pipeline life thus providing data suitable for economic models of the pipeline management. This tool can be also used to satisfy certain target reliability requirement. An example is presented comparing a natural gas pipeline with a pipeline containing hydrogen.

The BMW Hydrogen 7 is the world’s first premium sedan with a bi-fuelled internal combustion engine concept that has undergone the series development process. This car also displays the BMW typical driving pleasure. During development the features of the hydrogen energy source were emphasized. Engine tank system and vehicle electronics were especially developed as integral parts of the vehicle for use with hydrogen. The safety-oriented development process established additional strict hydrogen-specific standards for the Hydrogen 7. The fulfilment of these standards were demonstrated in a comprehensive experimentation and testing program which included all required tests and a large number of additional hydrogen-specific crash tests such as side impacts to the tank coupling system or rear impacts. Furthermore the behaviour of the hydrogen tank was tested under extreme conditions for instance in flames and after strong degradation of the insulation. Testing included over 1.7 million km of driving; and all tests were passed successfully proving the intrinsic safety of the vehicle and also confirming the success of the safety-oriented development process which is to be continued during future vehicle development. A safety concept for future hydrogen vehicles poses new challenges for vehicles and infrastructure. One goal is to develop a car fuelled by hydrogen only while simultaneously optimizing the safety concept. Another important goal is removal of (self-imposed) restrictions for parking in enclosed spaces such as garages. We present a vision of safety standards requirements and a program for fulfilling them.

This paper presents a simple hydrogen fuel cell vehicle (HFCV) energy consumption model. Simple fuel/energy consumption models have been developed and employed to estimate the energy and environmental impacts of various transportation projects for internal combustion engine vehicles (ICEVs) battery electric vehicles (BEVs) and hybrid electric vehicles (HEVs). However there are few published results on HFCV energy models that can be simply implemented in transportation applications. The proposed HFCV energy model computes instantaneous energy consumption utilizing instantaneous vehicle speed acceleration and roadway grade as input variables. The mode accurately estimates energy consumption generating errors of 0.86% and 2.17% relative to laboratory data for the fuel cell estimation and the total energy estimation respectively. Furthermore this work validated the proposed model against independent data and found that the new model accurately estimated the energy consumption producing an error of 1.9% and 1.0% relative to empirical data for the fuel cell and the total energy estimation respectively. The results demonstrate that transportation engineers policy makers automakers and environmental engineers can use the proposed model to evaluate the energy consumption effects of transportation projects and connected and automated vehicle (CAV) transportation applications within microscopic traffic simulation models.

The key project objectives include:

• Understand the range size type mode of operation and control system of installed gas engines in the UK. This will include equipment for CHP and for stand-by power operation.
• Produce data sets on the impact of hydrogen on gas engine operational performance.
• Develop knowledge on the impact of hydrogen content on the operation of the gas engine including overall efficiency changes to emissions profiles overall system operability.
• Providing outline guidance on a potential hydrogen limit that should be considered regarding use of natural gas/hydrogen mixed fuels in gas engines.
• Outlining a high-level view on the reliability and impact on maintenance and replacement regimes if gas engines operate on natural gas/hydrogen mixed fuels for extended time periods.
• Highlight any existing barriers to use of natural gas and hydrogen blends in gas engine and through contact with OEMs develop an understanding of future technology developments that may be needed to enable the use of “high” hydrogen blends.

The main aim is to characterise the impact of using natural gas/hydrogen fuel mixtures on the operation of gas engines used in CHP systems.

The output from this project will also inform the HyDeploy NIC project in relation to potential hydrogen content limits. The project will be presented at the IGEM Gas Quality Working Group (IGEM GQWG).

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.

In August 2020 Germany and Ukraine launched an energy partnership that includes the development of a hydrogen economy. Ukraine has vast renewable energy resources for “green” hydrogen production and a gas transmission system for transportation instead of Russian natural gas. Based on estimates by Hydrogen Europe Ukraine can install 8000 MW of total electrolyser capacity by 2030. For these reasons Ukraine is among the EU’s priority partners concerning clean hydrogen according to the EU Hydrogen strategy. Germany plans to reach climate neutrality by 2045 and “green” hydrogen plays an important role in achieving this target. However according to the National Hydrogen Strategy of Germany local production of “green” hydrogen will not cover all internal demand in Germany. For this reason Germany considers importing hydrogen from Ukraine. To govern the production and import of “green” hydrogen Germany and Ukraine shall introduce legal regulations the initial analysis of which is covered in this study. Based on observation and comparison this paper presents and compares approaches while exploring the current stage and further perspectives for legal regulation of hydrogen in Germany and Ukraine. This research identifies opportunities in hydrogen production to improve the flexibility of the Ukrainian power system. This is an important issue for Ukrainian energy security. In the meantime hydrogen can be a driver for decarbonisation according to the initial plans of Germany and it may also have positive impact on the operation of Germany’s energy system with a high share of renewables.