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A National Set of Hydrogen Codes and Standards for the US
Sep 2009
Publication
In 2003 the US Department of Energy (DOE) initiated a project to coordinate the development of a national template of hydrogen codes and standards for both vehicular and stationary applications. The process consisted of an initial evaluation to determine where there were gaps in the existing hydrogen codes and standards and the codes and standards required to fill these gaps. These codes and standards were to be developed by several Standards Development Organizations (SDOs). This effort to develop codes and standards has progressed from a position in 2003 when there were relatively few codes and standards that directly addressed hydrogen technology applications to the position at the end of 2008 where requirements to permit hydrogen technologies have been implemented in primary adopted codes- building and fire codes in hydrogen specific codes such as National Fire Protection Association (NFPA) 52 NFPA 55 and NFPA 853 and in many of the hydrogen specific component standards that are referenced primarily in the NFPA codes and standards. This paper describes the three levels of codes and standards that address hydrogen technologies for the built environment:<br/>Level 1. Primary adopted building and fire codes<br/>Level 2. Hydrogen specific codes and standards references in primary adopted code<br/>Level 3. Hydrogen specific component standards referenced in hydrogen specific codes<br/>This paper also describes the progress to date in populating these three levels with the required hydrogen codes and standards. The first two levels are essentially complete and are undergoing refinement and routine revision. Level 3 the hydrogen specific component standards is the furthest from having first edition documents that address requirements for a hydrogen system component.<br/>The DOE is focusing much of their codes and standards development efforts on these hydrogen specific component standards with the expectation that a first edition of most of these standards will be issued by 2010.
Ignition and Heat Radiation of Cryogenic Hydrogen Jets
Sep 2011
Publication
In the present work release and ignition experiments with horizontal cryogenic hydrogen jets at temperatures of 35–65 K and pressures from 0.7 to 3.5 MPa were performed in the ICESAFE facility at KIT. This facility is specially designed for experiments under steady-state sonic release conditions with constant temperature and pressure in the hydrogen reservoir. In distribution experiments the temperature velocity turbulence and concentration distribution of hydrogen with different circular nozzle diameters and reservoir conditions was investigated for releases into stagnant ambient air. Subsequent combustion experiments of hydrogen jets included investigations on the stability of the flame and its propagation behaviour as function of the ignition position. Furthermore combustion pressures and heat radiation from the sonic jet flame during the combustion process were measured. Safety distances were evaluated and an extrapolation model to other jet conditions was proposed. The results of this work provide novel data on cryogenic sonic hydrogen jets and give information on the hazard potential arising from leaks in liquid hydrogen reservoirs.
Quantitative Imaging of Multi-Component Turbulent Jets
Sep 2011
Publication
The integration of a hydrogen gas storage arrangement in vehicles has not been without its challenges. Gaseous state of hydrogen at ambient temperature combined with the fact that hydrogen is highly flammable results in the requirement of more robust high pressure storage systems that can meet modern safety standards. To develop these new safety standards and to properly predict the phenomena of hydrogen dispersion a better understanding of the resulting flow structures and flammable region from controlled and uncontrolled releases of hydrogen gas must be achieved. With the upper and lower explosive limits of hydrogen known the flammable envelope surrounding the site of a uncontrolled hydrogen release can be found from the concentration field. In this study the subsonic release of hydrogen was emulated using helium as a substitute working fluid. A sharp orifice round turbulent jet is used to emulate releases in which leak geometry is circular. Effects of buoyancy and crossflow were studied over a wide range of Froude numbers. The velocity fields of turbulent jets were characterized using particle image velocimetry (PIV). The mean and fluctuation velocity components were well quantified to show the effect of buoyancy due to the density difference between helium and the surrounding air. In the range of Froude numbers investigated (Fr = 1000 750 500 250 and 50) the increasing effects of buoyancy were seen to be proportional to the reduction of the Fr number. While buoyancy is experienced to have a negligible effect on centerline velocity fluctuations acceleration due to buoyancy in the other hand resulted in a slower decay of time-averaged axial velocity component along the centerline. The obtained results will serve as control reference values for further concentration measurement study and for computational fluid dynamics (CFD) validation.
High Pressure Hydrogen Fires
Sep 2009
Publication
Within the scope of the French national project DRIVE and European project HyPER high pressure jet flames of hydrogen were produced and instrumented.<br/>The experimental technique and measurement strategy are presented. Many aspects are original developments like the direct measurement of the mass flow rate by weighing continuously the hydrogen container the image processing to extract the flame geometry the heat flux measurement device the thermocouples arrangement…<br/>Flames were observed from 900 bar down to 1 bar with orifices ranging from 1 to 3 mm. An original set of data is now available about the main flame characteristics and about some thermodynamic aspects of hydrogen releases under high pressure.<br/>A brief comparison of some available models is presented.
Numerical Modelling of Hydrogen Deflagration Dynamics in Enclosed Space
Sep 2009
Publication
A three-dimensional mathematical model of gaseous hydrogen deflagration in the enclosed space is developed. The process is described by the system of gas dynamics differential equations. Thermodynamic parameters of the mixture and its components are defined as functions of the local temperature and mixture composition. The concentration changes of the fuel and combustion products are determined using conservation laws taking into account rates of component disappearance and formation and turbulent diffusion. It is assumed that the chemical reaction takes place only in the volume where the fuel concentration is within the limits of inflammability. The mathematical model is validated during an intercomparison test to predict deflagration of a large-scale hydrogen-air mixture in open atmosphere. An algorithm of numerical solution based on the Godunov method is developed. A computer system of engineering analysis of gas-dynamic processes of hydrogen-air mixture formation and combustion in enclosed space with natural ventilation is created. It allows predicting the history of the changes of overpressure temperature concentrations of hydrogen and combustion products and other thermogasdynamic parameters of the mixture in space. This prognosis can be used to estimate dangerous zones of destruction and recommend some safety measures.
High-pressure PEM Water Electrolysis and Corresponding Safety Issues
Sep 2009
Publication
In this paper safety considerations related to the operation of proton-exchange membrane (PEM) water electrolysers (hydrogen production capacity up to 1 Nm3/h and operating pressure up to 130 bars) are presented. These results were obtained in the course of the GenHyPEM project a research program on high-pressure PEM water electrolysis supported by the European Commission. Experiments were made using a high-pressure electrolysis stack designed for operation in the 0–130 bars pressure range at temperatures up to 90 °C. Besides hazards related to the pressure itself hydrogen concentration in the oxygen gas production and vice-versa (resulting from membrane crossover permeation effects) have been identified as the most significant risks. Results show that the oxygen concentration in hydrogen at 130 bars can be as high as 2.66 vol %. This is a value still outside the flammability limit for hydrogen–oxygen mixtures (3.9–95.8 vol %) but safety measures are required to prevent explosion hazards. A simple model based on the diffusion of dissolved gases is proposed to account for gas cross-permeation effects. To reduce contamination levels different solutions are proposed. First thicker membranes can be used. Second modified or composite membranes with lower gas permeabilities can be used. Third as reported earlier external catalytic gas recombiners can be used to promote H2/O2 recombination and reduce contamination levels in the gas production. Finally other considerations related to cell and stack design are also discussed to further reduce operation risks.
Hydrogenation and Dehydrogenation of Liquid Organic Hydrogen Carriers: A New Opportunity for Carbon-Based Catalysts
Jan 2022
Publication
The development of a hydrogen-based economy is the perfect nexus between the need of discontinuing the use of fossil fuels (trying to mitigate climate change) the development of a system based on renewable energy (with the use of hydrogen allowing us to buffer the discontinuities produced in this generation) and the achievement of a local-based robust energy supply system. However extending the use of hydrogen as an energy vector must still overcome challenging issues with the key issues being related to its storage. Cryogenic or pressurized storage is relatively expensive technically complex and presents important safety concerns. As a promising alternative the use of organic hydrogen carriers has been suggested in recent years. The ideal carrier will be an organic compound with a low melting point and low viscosity with a significant number of unsaturated carbon–carbon bonds in addition to being easy to hydrogenate and dehydrogenate. These properties allow us to store and transport hydrogen in infrastructures designed for liquid fuels thus facilitating the replacement of fossil fuels by hydrogen
Numerical Study of Spontaneous Ignition in Pressurized Hydrogen Release Through a Length of Tube with Local Contraction
Sep 2011
Publication
Numerical investigations have been conducted on the effect of the internal geometry of a local contraction on the spontaneous ignition of pressurized hydrogen release through a length of tube using a 5th-order WENO scheme. A mixture-averaged multi-component approach was used for accurate calculation of molecular transport. The auto-ignition and combustion chemistry were accounted for using a 21-step kinetic scheme. It is found that a local contraction can significantly facilitate the occurrence of spontaneous ignition by producing elevated flammable mixture and enhancing turbulent mixing from shock formation reflection and interaction. The first ignition kernel is observed upstream the contraction. It then quickly propagates along the contact interface and transits to a partially premixed flame due to the enhanced turbulent mixing. The partially premixed flames are highly distorted and overlapped with each other. Flame thickening is observed which is due to the merge of thin flames. The numerical predictions suggested that sustained flames could develop for release pressure as low as 25 bar. For the release pressure of 18 bar spontaneous ignition was predicted but the flame was soon quenched. To some extent this finding is consistent with Dryer et al.'s experimental observation in that the minimum release pressure required to induce a spontaneous ignition for the release through a tube with internal geometries is only 20.4 bar.
Design and Costs Analysis of Hydrogen Refuelling Stations Based on Different Hydrogen Sources and Plant Configurations
Jan 2022
Publication
In this study the authors present a techno-economic assessment of on-site hydrogen refuelling stations (450 kg/day of H2 ) based on different hydrogen sources and production technologies. Green ammonia biogas and water have been considered as hydrogen sources while cracking autothermal reforming and electrolysis have been selected as the hydrogen production technologies. The electric energy requirements of the hydrogen refuelling stations (HRSs) are internally satisfied using the fuel cell technology as power units for ammonia and biogas-based configurations and the PV grid-connected power plant for the water-based one. The hydrogen purification where necessary is performed by means of a Palladium-based membrane unit. Finally the same hydrogen compression storage and distribution section are considered for all configurations. The sizing and the energy analysis of the proposed configurations have been carried out by simulation models adequately developed. Moreover the economic feasibility has been performed by applying the life cycle cost analysis. The ammonia-based configurations are the best solutions in terms of hydrogen production energy efficiency (>71% LHV) as well as from the economic point of view showing a levelized cost of hydrogen (LCOH) in the range of 6.28 EUR/kg to 6.89 EUR/kg a profitability index greater than 3.5 and a Discounted Pay Back Time less than five years.
Numerical Study on Spontaneous Ignition of Pressurized Hydrogen Release Through a Length of Tube
Sep 2009
Publication
The issue of spontaneous ignition of highly pressurized hydrogen release is of important safety concern e.g. in the assessment of risk and design of safety measures. This paper reports on recent numerical investigation of this phenomenon through releases via a length of tube. This mimics a potential accidental scenario involving release through instrument line. The implicit large eddy simulation (ILES) approach was used with the 5th-order weighted essentially non-oscillatory (WENO) scheme. A mixture-averaged multi-component approach was used for accurate calculation of molecular transport. The thin flame was resolved with fine grid resolution and the autoignition and combustion chemistry were accounted for using a 21-step kinetic scheme.<br/>The numerical study revealed that the finite rupture process of the initial pressure boundary plays an important role in the spontaneous ignition. The rupture process induces significant turbulent mixing at the contact region via shock reflections and interactions. The predicted leading shock velocity inside the tube increases during the early stages of the release and then stabilizes at a nearly constant value which is higher than that predicted by one-dimensional analysis. The air behind the leading shock is shock-heated and mixes with the released hydrogen in the contact region. Ignition is firstly initiated inside the tube and then a partially premixed flame is developed. Significant amount of shock-heated air and well developed partially premixed flames are two major factors providing potential energy to overcome the strong under-expansion and flow divergence following spouting from the tube.<br/>Parametric studies were also conducted to investigate the effect of rupture time release pressure tube length and diameter on the likelihood of spontaneous ignition. It was found that a slower rupture time and a lower release pressure will lead to increases in ignition delay time and hence reduces the likelihood of spontaneous ignition. If the tube length is smaller than a certain value even though ignition could take place inside the tube the flame is unlikely to be sufficiently strong to overcome under-expansion and flow divergence after spouting from the tube and hence is likely to be quenched.
Regulations and Research on RC&S for Hydrogen Storage Relevant To Transport and Vehicle Issues with Special Focus on Composite Containments
Sep 2011
Publication
Developers interested in high pressure storage of hydrogen for mobile use increasingly rely on composite cylinders for onboard storage or transport of dangerous goods. Thus composite materials and systems deserve special consideration. History gives interesting background information important to the understanding of the current situation as to regulations codes and standards.<br/>Based on this review origins of different regulations for the storage of hydrogen as dangerous good and as propellant for vehicles will be examined. Both categories started out using steel and sometimes aluminium as cylinder material. With composite materials becoming more common a new problem emerged: vital input for regulations on composite pressure systems was initially derived from decades of experience with steel cylinders. As a result both regulatory fields suffer somewhat from this common basis. Only recent developments regarding requirements for composite cylinders have begun to go more and more separate ways. Thus these differences lead to some shortcomings in regulation with respect to composite storage systems.<br/>In principle in spite of separate development these deficits are in both applications very much the same: there are uncertainties in the prediction of safe service life in retesting procedures of composite cylinders and in their intervals. Hence different aspects of uncertainties and relevant approaches to solutions will be explained.
Spontaneous Ignition Processes Due To High-Pressure Hydrogen Release in Air
Sep 2011
Publication
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.
Pressure Cycling Of Type 1 Pressure Vessels with Gaseous Hydrogen
Sep 2011
Publication
Type 1 steel pressure vessels are commonly used for the transport of pressurized gases including gaseous hydrogen. In the majority of cases these cylinders experience relatively few pressure cycles over their lifetime perhaps in the hundreds. In emerging markets such as hydrogen-powered industrial trucks hydrogen fuel systems are expected to experience thousands of cycles over just a few year period. This study investigates the fatigue life of Type 1 steel pressure vessels by subjecting full- scale vessels to pressure cycles with gaseous hydrogen between nominal pressure of 3.5 and 43.8 MPa. In addition engineered defects were machined on the inside of several pressure vessels for comparison to fatigue crack growth measurements on materials sectioned from these pressure vessels. As-manufactured pressure vessels have sustained >35000 cycles with failure while vessels with machined defects leaked before bursting after 8000 to 15000 pressure cycles. The measured number of cycles to failure in these pressure vessels is two to three times greater than predicted using conservative methods based on fatigue crack growth rates measured in gaseous hydrogen.
Flammability Limits and Laminar Flame Speed of Hydrogen–air Mixtures at Sub-atmospheric Pressures
Sep 2011
Publication
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.
Numerical Study on Fast Filling of 70 MPA Hydrogen Vehicle Cylinder
Sep 2011
Publication
There will be significant temperature rise within hydrogen vehicle cylinder during the fast filling process. The temperature rise should be controlled under the temperature limit (85 °C) of the structure material (set by ISO/TS 15869) because it may lead to the failure of the structure. In this paper a 2-dimensional axisymmetric computational fluid dynamics (CFD) model for fast filling of 70 MPa hydrogen vehicle cylinder is presented. The numerical simulations are based on the modified standard k − ɛ turbulence model. In addition both the equation of state for hydrogen gas and the thermodynamic properties are calculated by National Institute of Standards and Technology (NIST) database: REFPROP 7.0. The thermodynamic responses of fast filling with different pressure-rise patterns and filling times within type III cylinder have been analyzed in detail.
The Fifth Carbon Budget: The Next Step Towards a Low-carbon Economy
Nov 2015
Publication
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.
An Independent Assessment of the UK’s Clean Growth Strategy: From Ambition to Action
Nov 2018
Publication
This report provides the Committee on Climate Change’s response to the UK Government’s Clean Growth Strategy.
The report finds that:
The report finds that:
- The Government has made a strong commitment to achieving the UK’s climate change targets.
- Policies and proposals set out in the Clean Growth Strategy will need to be firmed up.
- Gaps to meeting the fourth and fifth carbon budgets remain. These gaps must be closed.
- Risks of under-delivery must be addressed and carbon budgets met on time.
Hydrogen in a Low-carbon Economy
Nov 2018
Publication
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:
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
- 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
The Role of Charging and Refuelling Infrastructure in Supporting Zero-emission Vehicle Sales
Mar 2020
Publication
Widespread uptake of battery electric plug-in hybrid and hydrogen fuel-cell vehicles (collectively zero-emissions vehicles or ZEVs) could help many regions achieve deep greenhouse gas mitigation goals. Using the case of Canada this study investigates the extent to which increasing ZEV charging and refuelling availability may boost ZEV sales relative to other ZEV-supportive policies. We adapt a version of the Respondent-based Preferences and Constraints (REPAC) model using 2017 survey data from 1884 Canadian new vehicle-buyers to simulate the sales impacts of increasing electric vehicle charging access at home work public destinations and on highways as well as increasing hydrogen refuelling station access. REPAC is built from a stated preference choice model and represents constraints in supply and consumer awareness as well as dynamics in ZEV policy out to 2030. Results suggest that new ZEV market share from 2020 to 2030 does not substantially benefit from increased infrastructure. Even when electric charging and hydrogen refuelling access are simulated to reach “universally” available levels by 2030 ZEV sales do not rise by more than 1.5 percentage points above the baseline trajectory. On the other hand REPAC simulates ZEV market share rising as high as 30% by 2030 with strong ZEV-supportive policies even without the addition of charging or refuelling infrastructure. These findings stem from low consumer valuation of infrastructure found in the stated preference model. Results suggest that achieving ambitious ZEV sale targets requires a comprehensive suite of policies beyond a focus on charging and refuelling infrastructure.
Public Acceptability of the Use of Hydrogen for Heating and Cooking in the Home: Results from Qualitative and Quantitative Research in UK<br/>Executive Summary
Nov 2018
Publication
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:
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.
- 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
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