Publications

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.

In the development of hydrogen technology special attention is paid to the technical problems of hydrogen storage. One possible way is cryogenic storage in liquid form. Generally cryo-technical machines need components with interacting surfaces in relative motion such as bearings seals or valves which are subjected to extreme conditions. Materials of such systems have to be resistant to friction-caused mechanical deformation at the surface low temperatures and hydrogen environment. Since materials failure can cause uncontrolled escape of hydrogen new material requirements are involved for these tribo-systems in particular regarding operability and reliability. In the past few years several projects dealing with the influence of hydrogen on the tribological properties of friction couples were conducted at the Federal Institute for Materials Research and Testing (BAM) Berlin. This paper reports some  investigations carried out with polymer composites. Friction and wear were measured for continuous sliding and analyses of the worn surfaces were performed after the experiments. Tests were performed at room temperature in hydrogen as well as in liquid hydrogen.

This paper presents a compilation of the results supplied by HySafe partners participating in the Standard Benchmark Exercise Problem (SBEP) V2 which is based on an experiment on hydrogen combustion that is first described. A list of the results requested from participants is also included. The main characteristics of the models used for the calculations are compared in a very succinct way by using tables. The comparison between results together with the experimental data when available is made through a series of graphs. The results show quite good agreement with the experimental data. The calculations have demonstrated to be sensitive to computational domain size and far field boundary condition.

Composite cylinders with metal liner are used for the storage of compressed hydrogen in automotive application. These hybrid pressure cylinders are designed for a nominal working pressure of up to 70 MPa. They also have to withstand a temperature range between -40°C and +85°C according GRPE draft [1] and for short periods up to a maximum temperature of 140°C during filling (fast filling) [2]. In order to exploit the material properties efficiently with a high degree of lightweight optimization and a high level of safety on the same time a better understanding of the structural behavior of hybrid designs is necessary. Work on this topic has been carried out in the frame of a work package on safety aspects and regulation (Subproject SAR) of the European IP StorHy (www.storhy.net). The temperature influence on the composite layers is distinctive due to there typical polymer material behavior. The stiffness of the composite layer is a function of temperature which influences global strains and stress levels (residual stresses) in operation. In order to do an accurate fatigue assessment of composite hybrid cylinders a realistic modeling of a representative temperature load is needed. For this climate data has been evaluated which were collected in Europe over a period of 30 years [3]. Assuming that the temperature follows a Gaussian (normal) distribution within the assessed period of 30 years it is possible to generate a frequency distribution for different temperature classes for the cold extreme and the hot extreme. Combining these distributions leads to the overall temperature range distribution (frequency over temperature classes). The climatic temperature influence the filling temperature and the pressure load have to be considered in combination with the operation profile of the storage cylinder to derive a complete load vector for an accurate assessment of the lifetime and safety level.

Climate change is one of today’s most pressing global challenges. Since the emission of greenhouse gases is often closely related to the use and supply of energy the goal to avoid emissions requires a fundamental restructuring of the energy system including all parts of the technology chains from production to end-use. Natural gas is today one of the most important primary energy sources in Europe with utilization ranging from power generation and industry to appliances in the residential and commercial sector as well as mobility. As natural gas is a fossil fuel gas utilization is thus responsible for significant emissions of carbon dioxide (CO₂ ) a greenhouse gas. However the transformation of the gas sector with its broad variety of technologies and end-use applications is a challenge as a fuel switch is related to changing physical properties. Today the residential and commercial sector is the biggest end user sector for natural gas in the EU both in terms of consumption and in the number of installed appliances. Natural gas is used to provide space heating as well as hot water and is used in cooking and catering appliances with in total about 200 million gas-fired residential and commercial end user appliances installed. More than 40 % of the EU gas consumption is accounted for by the residential and commercial sector. The most promising substitutes for natural gas are biogases and hydrogen. The carbon-free fuel gas hydrogen may be produced e.g. from water and renewable electricity; therefore it can be produced with a greatly lowered carbon footprint and on a very large scale. As a gaseous fuel it can be transported stored and utilised in all end-use sectors that are served by natural gas today: Power plants industry commercial appliances households and mobility. Technologies and materials however need to be suitable for the new fuel. The injection of hydrogen into existing gas distribution for example will impact all gas-using equipment in the grids since these devices are designed and optimized to operate safely efficiently and with low pollutant emissions with natural gas as fuel. The THyGA project1 focusses on all technical aspects and the regulatory framework concerning the potential operation of domestic and commercial end user appliances with hydrogen  / natural gas blends. The THyGA deliverables start with theoretical background from material science (D2.4) and combustion theory (this report) and extend to the project’s experimental campaign on hydrogen tolerance tests as well as reports on the status quo and potential future developments on rules and standards as well as mitigation strategies for coping with high levels of hydrogen admixture. By this approach the project aims at investigating which levels of hydrogen blending impact the various appliance technologies to which extent and to identify the regime in which a safe efficient and low-polluting operation is possible. As this is in many ways a question of combustion this report focuses on theoretical considerations about the impact of hydrogen admixture on combustion processes. The effects of hydrogen admixture on main gas quality properties as well as combustion temperatures laminar combustion velocities pollutant formation (CO NOx) safety-related aspects and the impact of combustion control are discussed. This overview provides a basis for subsequent steps of the project e.g. for establishing the testing program. A profound understanding of the impact on hydrogen on natural gas combustion is also essential for the development of mitigation strategies to reduce potential negative consequences of hydrogen admixture on appliances.

This is part one. Part two of this project can be found at this link

The 'Hydrogen for Heat' (Hy4Heat) programme aims to support the UK Government in its ambitions to decarbonise the UK energy sector in line with the targets of the Climate Change Act 2008 by attempting to evaluate and de-risk the natural gas to hydrogen network conversion option. The impact on the commercial sector is an important factor in understanding the feasibility of utilising hydrogen to decarbonise heat in the UK. The overall objective of the market research study Work Package 5 (WP5) was to determine if it is theoretically possible to successfully convert the commercial sector to hydrogen. This work will contribute to the understanding of the scale type and capacity of gas heating appliances within the sector providing a characterisation of the market and determining the requirements and feasibility for successfully transitioning them to hydrogen in the future.

This report and any attachment is freely available on the Hy4Heat website here. The report can also be downloaded directly by clicking on the pdf icon above 

If the general public is to use hydrogen as a vehicle fuel customers must be able to handle hydrogen with the same degree of confidence and with comparable risk as conventional liquid and gaseous fuels. The hazards associated with jet releases from leaks in a vehicle-refuelling environment must be considered if hydrogen is stored and used as a high-pressure gas since a jet release in a confined or congested area could result in an explosion. As there was insufficient knowledge of the explosion hazards a study was initiated to gain a better understanding of the potential explosion hazard consequences associated with high-pressure leaks from refuelling systems. This paper describes two experiments with a dummy vehicle and dispenser units to represent refuelling station congestion. The first represents a ‘worst-case’ scenario where the vehicle and dispensers are enveloped by a 5.4 m x 6.0 m x 2.5 m high pre-mixed hydrogen-air cloud. The second is an actual high-pressure leak from storage at 40 MPa (400 bar) representing an uncontrolled full-bore failure of a vehicle refuelling hose. In both cases an electric spark ignited the flammable cloud. Measurements were made of the explosion overpressure generated its evolution with time and its decay with distance. The results reported provide a direct demonstration of the explosion hazard from an uncontrolled leak; they will also be valuable for validating explosion models that will be needed to assess configurations and conditions beyond those studied experimentally.

Many countries including China have implemented supporting policies to promote the commercialized application of green hydrogen and hydrogen fuel cells. In this study a system dynamics (SD) model is proposed to study the evolution of hydrogen demand in China from the petroleum refining industry the synthetic ammonia industry and the vehicle market. In the model the impact from the macro-environment hydrogen fuel supply and construction of hydrogen facilities is considered to combine in incentives for supporting policies. To further formulate the competitive relationship in the vehicle market the Lotka–Volterra (LV) approach is adopted. The model is verified using published data from 2003 to 2017. The model is also used to forecast China’s hydrogen demand up to the year of 2030 under three different scenarios. Finally some forward-looking guidance is provided to policy makers according to the forecasting results.

This work programme was focused on identifying a suitable odorant for use in a 100% hydrogen gas grid (domestic use such as boilers and cookers). The research involved a review of existing odorants (used primarily for natural gas) and the selection of five suitable odorants based on available literature. One odorant was selected based on possible suitability with a Polymer Electrolyte Membrane (PEM) based fuel cell vehicle which could in future be a possible end-user of grid hydrogen. NPL prepared Primary Reference Materials containing the five odorants in hydrogen at the relevant amount fraction levels (as would be found in the grid) including ones provided by Robinson Brothers (the supplier of odorants for natural gas in the UK). These mixtures were used by NPL to perform tests to understand the effects of the mixtures on pipeline (metal and plastic) appliances (a hydrogen boiler provided by Worcester Bosch) and PEM fuel cells. HSE investigated the health and environmental impact of these odorants in hydrogen. Olfactory testing was performed by Air Spectrum to characterise the ‘smell’ of each odorant. Finally an economic analysis was performed by E4tech. The results confirm that Odorant NB would be a suitable odorant for use in a 100% hydrogen gas grid for combustion applications but further research would be required if the intention is to supply grid hydrogen to stationery fuel cells or fuel cell vehicles. In this case further testing would need to be performed to measure the extent of fuel cell degradation caused by the non-sulphur odorant obtained as part of this work programme and also other UK projects such as the Hydrogen Grid to Vehicle (HG2V) project[1] would provide important information about whether a purification step would be required regardless of the odorant before the hydrogen purity would be suitable for a PEM fuel cell vehicle. If purification was required it would be fine to use Odorant NB as this would be removed during the purification step.

This report and any attachment is freely available on the Hy4Heat website here. The report can also be downloaded directly by clicking on the pdf icon above 

An experimental study of flame propagation acceleration and transition to detonation in hydrogen-air mixture in 2 m long rectangular cross section channel filled with obstacles located at the bottom wall was performed. The initial conditions of the hydrogen-air mixture were 0.1 MPa and 293 K. Three different cases of obstacle height (blockage ratio 0.25 0.5 and 0.75) and four cases of obstacle density were studied with the channel height equal to 0.08 m. The channel width was 0.11 m in all experiments. The propagation of flame and pressure waves was monitored by four pressure transducers and four in house ion probes. The pairs of transducers and probes were placed at various locations along the channel in order to get information about the progress of the phenomena along the channel. To examine the influence of mixture composition on flame propagation and DDT the experiments were performed for the compositions of 20% 25% and 29.6% of H2 in air by volume. As a result of the experiments the deflagration and detonation regimes and velocities of flame propagation in the obstructed channel were determined.