Germany

This article explains and evaluates contemporary methods for manufacturing bipolar plates (BPPs) for lowtemperature polymer electrolyte membrane fuel cells (LT-PEMFC) and highlights the potential of new improved approaches. BPPs are an essential component of fuel cells responsible for distributing reaction gases to facilitate efficient conversion of gaseous electrochemical energy to electricity. BPPs must balance technical properties such as electrical and thermal conductivities structural strength and corrosion resistance. Graphitic and metallic materials can meet the required specifications with each material offering distinct advantages and disadvantages. Each materials’ performance is complimented by a comparison of its manufacturability including: the material costs production rates and required capital investment. These results are contextualised with respect to the target applications to identify the challenges and advantages of manufacturing methods of choice for BPPs. This analysis shows that the optimal choice of BPP manufacturing method depends entirely on the needs of the target application in particular the relative importance of manufacturing rate cost and the expected operational life of the bipolar plate to the fuel cell designer.

Liquid organic hydrogen carriers (LOHC) store hydrogen by reversible hydrogenation of a carrier material. Water can enter the system via wet hydrogen coming from electrolysis as well as via moisture on the catalyst. Removing this water is important for reliable operation of the LOHC system. Different approaches for doing this have been evaluated on three stages of the process. Drying of the hydrogen before entering the LOHC system itself is preferable. A membrane drying process turns out to be the most efficient way. If the water content in the LOHC system is still so high that liquid–liquid demixing occurs it is crucial for water removal to enhance the slow settling. Introduction of an appropriate packing can help to separate the two phases as long as the volume flow is not too high. Further drying below the rather low solubility limit is challenging. Introduction of zeolites into the system is a possible option. Water adsorbs on the surface of the zeolite and moisture content is therefore decreased.

For the successful deployment of the Heavy Duty (HD) hydrogen vehicles an associated infrastructure in particular hydrogen refueling stations (HRS) should be reliable compliant with regulations and optimized to reduce the related costs. FCH JU project PRHYDE aims to develop a sophisticated protocol dedicated to HD applications. The target of the project is to develop protocol and recommendations for an efficient refueling of 350 500 and 700 bar HD tanks of types III and IV. This protocol is based on modeling results as well as experimental data. Different partners of the PRHYDE European project are closely working together on this target. However modeling approaches and corresponding tools must first be compared and validated to ensure the high level of reliability for the modeling results. The current paper presents the benchmark performed in the frame of the project by Air Liquide Engie Wenger Engineering and NREL. The different models used were compared and calibrated to the configurations proposed by the PRHYDE project. In addition several scenarios were investigated to explore different cases with high ambient temperatures.

The use of drop-in capable alternative fuels in aircraft can support the European aviation sector to achieve its goals for sustainable development. They can be a transitional solution in the short and medium term as their use does not require any structural changes to the aircraft powertrain. However the production of alternative fuels is often energy-intensive and some feedstocks are associated with harmful effects on the environment. In addition alternative fuels are often more expensive to produce than fossil kerosene which can make their use unattractive. Therefore this paper analyzes the environmental and economic impacts of four types of alternative fuels compared to fossil kerosene in a well-to-wake perspective. The fuels investigated are sustainable aviation fuels produced by power-to-liquid and biomass-to-liquid pathways. Life cycle assessment and life cycle costing are used as environmental and economic assessment methods. The results of this well-towake analysis reveal that the use of sustainable aviation fuels can reduce the environmental impacts of aircraft operations. However an electricity mix based on renewable energies is needed to achieve significant reductions. In addition from an economic perspective the use of fossil kerosene ranks best among the alternatives. A scenario analysis confirms this result and shows that the production of sustainable aviation fuels using an electricity mix based solely on renewable energy can lead to significant reductions in environmental impact but economic competitiveness remains problematic.

The automotive industry sees hydrogen-powered fuel cell(FC) drives as a promising option with a high range and shortrefueling time. Current research aims to increase the profitabil-ity of the fuel cell system by reducing hydrogen consumption.This study suggests the use of an electrochemical hydrogencompressor (EHC) for hydrogen recirculation. Compared tomechanical compressors the EHC is very efficient due to thealmost isothermal conditions and due to its modular structurecan only take up a minimal amount of space in vehicles. Inaddition gas separation and purification of the hydrogentakes place in an EHC which is a significant advantage overthe standard recirculation with a blower or a jet pump. Thehigh purity of the hydrogen at the cathode outlet of the EHCalso increased partial pressure of the hydrogen at the fuel cellinlet and its efficiency. The study carried out shows that repla-cing the blower with the EHC reduces the hydrogen loss bypurging by up to ~95% and the efficiency of the FC systemcould be further improved. Thus the EHC has a great poten-tial for recycling hydrogen in FC systems in the automotiveindustry and is a great alternative to the current blower.

Import and export of fossil energy carriers are cornerstones of energy systems world-wide. If energy systems are to become climate neutral and sustainable fossil carriers need to be substituted with carbon neutral alternatives or electrified if possible. We investigate synthetic chemical energy carriers hydrogen methane methanol ammonia and Fischer-Tropsch fuels produced using electricity from Renewable Energy Source (RES) as fossil substitutes. RES potentials are obtained from GIS-analysis and hourly resolved time-series are derived using reanalysis weather data. We model the sourcing of feedstock chemicals synthesis and transport along nine different Energy Supply Chains to Germany and compare import options for seven locations around the world against each other and with domestically sourced alternatives on the basis of their respective cost per unit of hydrogen and energy delivered. We find that for each type of chemical energy carrier there is an import option with lower costs compared to domestic production in Germany. No single exporting country or energy carrier has a unique cost advantage since for each energy carrier and country there are cost-competitive alternatives. This allows exporter and infrastructure decisions to be made based on other criteria than energy and cost. The lowest cost means for importing of energy and hydrogen are by hydrogen pipeline from Denmark Spain and Western Asia and Northern Africa starting at 36 EUR/MWhLHV to 42 EUR/MWhLHV or 1.0 EUR/kgH2 to 1.3 EUR/kgH2 (in 2050 assuming 5% p.a. capital cost). For complex energy carriers derived from hydrogen like methane ammonia methanol or Fischer-Tropsch fuels imports from Argentina by ship to Germany are lower cost than closer exporters in the European Union or Western Asia and Northern Africa. For meeting hydrogen demand direct hydrogen imports are more attractive than indirect routes using methane methanol or ammonia imports and subsequent decomposition to hydrogen because of high capital investment costs and energetic losses of the indirect routes. We make our model and data available under open licenses for adaptation and reuse.

Hydrogen safety is an important topic for hydrogen energy application. Unintended hydrogen releases and combustions are potential accident scenarios which are of great interest for developing and updating the safety codes and standards. In this paper hydrogen releases and delayed ignitions were studied.

Wind and solar energy are often expected to fall victim to their own success: the higher their share in electricity generation the more their revenue in electricity markets (their “market value”) declines. While market values may converge to zero in conventional power systems this study argues that “green” hydrogen production can effectively and permanently halt the decline by adding flexible electricity demand in low-price hours. To support this argument this article further develops the merit order model and uses price duration curves to include flexible hydrogen electrolysis and to derive an analytical formula for the minimum market value of renewables in the long-term market equilibrium. This hydrogen-induced minimum market value is quantified for a wide range of parameters using Monte Carlo simulations and complemented with results from a more detailed numerical electricity market model. It is shown that—due to flexible hydrogen production alone—market values across Europe will likely stabilize above €19 ± 9 MWh− 1 for solar energy and above €27 ± 8 MWh− 1 for wind energy in 2050 (annual mean estimate ± standard deviation). This is in the range of the projected levelized cost of renewables and other types of flexible electricity demand may further increase renewable market values. Market-based renewables may hence be within reach.

Integrated steelworks off-gases are generally exploited to produce heat and electricity. However further valorization can be achieved by using them as feedstock for the synthesis of valuable products such as methane and methanol with the addition of renewable hydrogen. This was the aim of the recently concluded project entitled “Intelligent and integrated upgrade of carbon sources in steel industries through hydrogen intensified synthesis processes (i3 upgrade)”. Within this project several activities were carried out: from laboratory analyses to simulation investigations from design development and tests of innovative reactor concepts and of advanced process control to detailed economic analyses business models and investigation of implementation cases. The final developed methane production reactors arerespectively an additively manufactured structured fixedbed reactor and a reactor setup using wash-coated honeycomb monoliths as catalyst; both reactors reached almost full COx conversion under slightly over-stoichiometric conditions. A new multi-stage concept of methanol reactor was designed commissioned and extensively tested at pilot-scale; it shows very effective conversion rates near to 100% for CO and slightly lower for CO2 at one-through operation for the methanol synthesis. Online tests proved that developed dispatch controller implements a smooth control strategy in real time with a temporal resolution of 1 min and a forecasting horizon of 2 h. Furthermore both offline simulations and cost analyses highlighted the fundamental role of hydrogen availability and costs for the feasibility of i 3 upgrade solutions and showed that the industrial implementation of the i 3 upgrade solutions can lead to significant environmental and economic benefits for steelworks especially in case green electricity is available at an affordable price.

Explosion venting is a prevention/mitigation solution widely used in the process industry to protect indoor equipment or buildings from excessive internal pressure caused by an accidental explosion. Vented explosions are widely investigated in the literature for various geometries hydrogen/air concentrations ignition positions initial turbulence etc. In real situations the vents are normally covered by a vent panel. In the case of an indoor leakage the hydrogen/air cloud will be stratified rather than homogeneous. Nowadays there is a lack in understanding about the vented explosion of stratified clouds and about the influence of vent cover inertia on the internal overpressure. This paper aims at shedding light on these aspects by means of experimental investigation of vented hydrogen/air deflagration using an experimental facility of 1m3 and via numerical simulations using the computational fluid dynamics (CFD) code FLACS