Germany

In this work the mechanical milling of a FeTiMn alloy for hydrogen storage purposes was performed in an industrial milling device. The TiFe hydride is interesting from the technological standpoint because of the abundance and the low cost of its constituent elements Ti and Fe as well as its high volumetric hydrogen capacity. However TiFe is difficult to activate usually requiring a thermal treatment above 400 °C. A TiFeMn alloy milled for just 10 min in a 100 L industrial milling device showed excellent hydrogen storage properties without any thermal treatment. The as-milled TiFeMn alloy did not need any activation procedure and showed fast kinetic behavior and good cycling stability. Microstructural and morphological characterization of the as-received and as-milled TiFeMn alloys revealed that the material presents reduced particle and crystallite sizes even after such short time of milling. The refined microstructure of the as-milled TiFeMn is deemed to account for the improved hydrogen absorption-desorption properties.

In this paper a gas-to-power (GtoP) system for power outages is digitally modeled and experimentally developed. The design includes a solid-state hydrogen storage system composed of TiFeMn as a hydride forming alloy (6.7 kg of alloy in five tanks) and an air-cooled fuel cell (maximum power: 1.6 kW). The hydrogen storage system is charged under room temperature and 40 bar of hydrogen pressure reaching about 110 g of hydrogen capacity. In an emergency use case of the system hydrogen is supplied to the fuel cell and the waste heat coming from the exhaust air of the fuel cell is used for the endothermic dehydrogenation reaction of the metal hydride. This GtoP system demonstrates fast stable and reliable responses providing from 149 W to 596 W under different constant as well as dynamic conditions. A comprehensive and novel simulation approach based on a network model is also applied. The developed model is validated under static and dynamic power load scenarios demonstrating excellent agreement with the experimental results.

The efficiency of gas sensor application for facilitating the safe use of hydrogen depends considerably on the sensor response to a change in hydrogen concentration. Therefore the response time has been measured for five different-type commercially available hydrogen sensors. Experiments showed that all these sensors surpass the ISO 26142 standard; for the response times t90 values of 2 s to 16 s were estimated. Results can be fitted with an exponential or sigmoidal function. It can be demonstrated that the results on transient behaviour depend on both the operating parameters of sensors and investigation methods as well as on the experimental conditions: gas change rate and concentration jump.

The storage of hydrogen in materials has received a significant amount of attention in recent years because this approach is widely thought to be one of the most promising solutions to the problem of storing hydrogen for use as an alternative energy carrier in a safe compact and affordable form. However there have been a number of high profile cases in which erroneous or irreproducible data have been published. Meanwhile the irreproducibility of research results in a wide range of disciplines has been the subject of an increasing amount of attention due to problems with some of the data in the literature. In this Perspective we provide a summary of the problems that have affected hydrogen storage material research. We also discuss the reasons behind them and possible ways of reducing the likelihood of further problems occurring in the future.

Our contribution demonstrates that hydrogen storage in stationary Liquid Organic Hydrogen Carrier (LOHC) systems becomes much simpler and significantly more efficient if both the LOHC hydrogenation and the LOHC dehydrogenation reaction are carried out in the same reactor using the same catalyst. The finding that the typical dehydrogenation catalyst for hydrogen release from perhydro dibenzyltoluene (H18-DBT) Pt on alumina turns into a highly active and very selective dibenzyltoluene hydrogenation catalyst at temperatures above 220 °C paves the way for our new hydrogen storage concept. Herein hydrogenation of H0-DBT and dehydrogenation of H18-DBT is carried out at the same elevated temperature between 290 and 310 °C with hydrogen pressure being the only variable for shifting the equilibrium between hydrogen loading and release. We demonstrate that the heat of hydrogenation can be provided at a temperature level suitable for effective dehydrogenation catalysis. Combined with a heat storage device of appropriate capacity or a high pressure steam system this heat could be used for dehydrogenation.

Hydrogen can be produced from the decomposition of methane (also called pyrolysis). Many studies assume that this process emits few greenhouse gas (GHG) because the reaction from methane to hydrogen yields only solid carbon and no CO₂. This paper assesses the life-cycle GHG emissions and the levelized costs for hydrogen provision from methane decomposition in three configurations (plasma molten metal and thermal gas). The results of these configurations are then compared to electrolysis and steam methane reforming (SMR) with and without CO₂capture and storage (CCS). Under the global natural gas supply chain conditions hydrogen from methane decomposition still causes significant GHG emissions between 43 and 97 g CO₂-eq./MJ. The bandwidth is predominately determined by the energy source providing the process heat i.e. the lowest emissions are caused by the plasma system using renewable electricity. This configuration shows lower GHG emissions compared to the “classical” SMR (99 g CO₂-eq./MJ) but similar emissions to the SMR with CCS (46 g CO2-eq./MJ). However only electrolysis powered with renewable electricity leads to very low GHG emissions (3 g CO₂-eq./MJ). Overall the natural gas supply is a decisive factor in determining GHG emissions. A natural gas supply with below-global average GHG emissions can lead to lower GHG emissions of all methane decomposition configurations compared to SMR. Methane decomposition systems (1.6 to 2.2 €/kg H2) produce hydrogen at costs substantially higher compared to SMR (1.0 to 1.2 €/kg) but lower than electrolyser (2.5 to 3.0 €/kg). SMR with CCS has the lowest CO₂abatement costs (24 €/t CO₂-eq. other > 141 €/t CO₂-eq.). Finally fuels derived from different hydrogen supply options are assessed. Substantially lower GHG emissions compared to the fossil reference (natural gas and diesel/gasoline) are only possible if hydrogen from electrolysis powered by renewable energy is used (>90% less). The other hydrogen pathways cause only slightly lower or even higher GHG emissions.

The maritime shipping sector is a major contributor to CO₂ emissions and this figure is expected to rise in coming decades. With the intent of reducing emissions from this sector this research proposes the utilization of the jet stream to transport a combination of cargo and hydrogen using airships or balloons at altitudes of 10–20 km. The jet streams flow in the mid-latitudes predominantly in a west–east direction reaching an average wind speed of 165 km/h. Using this combination of high wind speeds and reliable direction hydrogen-filled airships or balloons could carry hydrogen with a lower fuel requirement and shorter travel time compared to conventional shipping. Jet streams at different altitudes in the atmosphere were used to identify the most appropriate circular routes for global airship travel. Round-the-world trips would take 16 days in the Northern Hemisphere and 14 in the Southern Hemisphere. Hydrogen transport via the jet stream due to its lower energy consumption and shorter cargo delivery time access to cities far from the coast could be a competitive alternative to maritime shipping and liquefied hydrogen tankers in the development of a sustainable future hydrogen economy.

Hydrogen technologies have received increased attention in research and development to foster the shift towards carbon-neutral energy systems. Depending on the specific production techniques transportation concepts and application areas hydrogen supply chains (HSCs) can be anything from part of the energy transition problem to part of the solution: Even more than battery-driven electric mobility hydrogen is a polyvalent technology and can be used in very different contexts with specific positive or negative sustainability impacts. Thus a detailed sustainability evaluation is crucial for decision making in the context of hydrogen technology and its diverse application fields. This article provides a comprehensive structured literature review in the context of HSCs along the triple bottom line dimensions of environmental economic and social sustainability analyzing a total of 288 research papers. As a result we identify research gaps mostly regarding social sustainability and the supply chain stages of hydrogen distribution and usage. We suggest further research to concentrate on these gaps thus strengthening our understanding of comprehensive sustainability evaluations for HSCs especially in social sustainability evaluation. In addition we provide an additional approach for discussion by adding literature review results from neighboring fields highlighting the joint challenges and insights regarding sustainability evaluation.

The storage of hydrogen is the key technology for a sustainable future. We developed an in silico procedure which is based on the combination of experimental and quantum-chemical methods. This method was used to evaluate energetic parameters for hydrogenation/dehydrogenation reactions of various pyrazine derivatives as a seminal liquid organic hydrogen carriers (LOHC) that are involved in the hydrogen storage technologies. With this in silico tool the tempo of the reliable search for suitable LOHC candidates will accelerate dramatically leading to the design and development of efficient materials for various niche applications.

In this paper the implications of the use of hydrogen on product yield and conversion efficiency as well as on economic performance of a hydrogen enhanced Biomass-to-Liquid (BtL) process are analyzed. A process concept for the synthesis of fuel (gasoline and LPG) from biomass-derived synthesis gas via Methanol-to-Gasoline (MtG) route with utilization of carbon dioxide from gasification by feeding additional hydrogen is developed and modeled in Aspen Plus. The modeled process produces 0.36 kg fuel per kg dry straw. Additionally 99 MW electrical power are recovered from purge and off gases from fuel synthesis in CCGT process covering the electricity consumption of fuel synthesis and synthesis gas generation. The hydrogen enhanced BtL procces reaches a combined chemical and electrical efficiency of 48.2% and overall carbon efficiency of 69.5%. The total product costs (TPC) sum up to 3.24 €/kg fuel. Raw materials (hydrogen and straw) make up the largest fraction of TPC with a total share of 75%. The hydrogen enhanced BtL process shows increased chemical energy and carbon efficiencies and thus higher product yields. However economic analysis shows that the process is unprofitable under current conditions due to high costs for hydrogen provision.