Spain

The production of hydrogen from renewable sources is essential to develop the future hydrogen economy. Biomass is an abundant clean and renewable energy source and it can be important in the production of hydrogen. The Valencian Community due to its great agricultural and forestry activities generates an important quantity of biomass residues that can be used for energy generation approximately 778 kt of wet biomass residues per year. This great quantity of biomass can be transformed into a hydrogen-rich gas by different thermochemical conversion processes. In this article the potential of production of hydrogen-rich gas is analyzed considering several factors affecting the conversion yield of these processes. As a result of this analysis it could be possible to produce 1271 MNm3 of H₂ per year considering the total biomass residues of the community and selecting the gasification processes.

With regard to the goals of the European HySafe Network research facilities are essential for the experimental investigation of relevant phenomena for testing devices and safety concepts as well as for the generation of validation data for the various numerical codes and models. The integrating activity ‘Integration of Experimental Facilities (IEF)’ has provided basic support for jointly performed experimental work within HySafe. Even beyond the funding period of the NoE HySafe in the 6th Framework Programme IEF represents a long lasting effort for reaching sustainable integration of the experimental research capacities and expertise of the partners from different research fields. In order to achieve a high standard in the quality of experimental data provided by the partners emphasis was put on the know-how transfer between the partners. The strategy for reaching the objectives consisted of two parts. On the one hand a documentation of the experimental capacities has been prepared and analysed. On the other hand a communication base has been established by means of biannual workshops on experimental issues. A total of 8 well received workshops has been organised covering topics from measurement technologies to safety issues. Based on the information presented by the partners a working document on best practice including the joint experimental knowledge of all partners with regard to experiments and instrumentation was created. Preserving the character of a working document it was implemented in the IEF wiki website which was set up in order to provide a central communication platform. The paper gives an overview of the IEF network activities over the last 5 years.

The hydrogen economy has received resurging interest in recent years as more countries commit to net-zero CO₂ emissions around the mid-century. “Blue” hydrogen from natural gas with CO₂ capture and storage (CCS) is one promising sustainable hydrogen supply option. Although conventional CO₂ capture imposes a large energy penalty advanced process concepts using the chemical looping principle can produce blue hydrogen at efficiencies even exceeding the conventional steam methane reforming (SMR) process without CCS. One such configuration is gas switching reforming (GSR) which uses a Ni-based oxygen carrier material to catalyze the SMR reaction and efficiently supply the required process heat by combusting an off-gas fuel with integrated CO₂ capture. The present study investigates the potential of advanced La-Fe-based oxygen carrier materials to further increase this advantage using a gas switching partial oxidation (GSPOX) process. These materials can overcome the equilibrium limitations facing conventional catalytic SMR and achieve direct hydrogen production using a water-splitting reaction. Results showed that the GSPOX process can achieve mild efficiency improvements relative to GSR in the range of 0.6–4.1%-points with the upper bound only achievable by large power and H₂ co-production plants employing a highly efficient power cycle. These performance gains and the avoidance of toxicity challenges posed by Ni-based oxygen carriers create a solid case for the further development of these advanced materials. If successful results from this work indicate that GSPOX blue hydrogen plants can outperform an SMR benchmark with conventional CO₂ capture by more than 10%-points both in terms of efficiency and CO₂ avoidance.

Experimental evidence exists for the enhancement of the hydrogen storage capacity of porous carbons when these materials are doped with metal nanoparticles. One of the most studied dopants is palladium. Dissociation of the hydrogen molecules and spillover of the H atoms towards the carbon substrate has been advocated as the reason for the enhancement of the storage capacity. We have investigated this mechanism by performing ab initio density functional molecular dynamics (AIMD) simulations of the deposition of molecular hydrogen on Pd6 clusters anchored on graphene vacancies. The clusters are initially near-saturated with atomic and molecular hydrogen. This condition would facilitate the occurrence of spillover since our energy calculations based on density functional theory indicate that migration of preadsorbed H atoms towards the graphene substrate becomes exothermic on Pd clusters with high hydrogen coverages. However AIMD simulations show that the H atoms prefer to intercalate and absorb within the Pd cluster rather than migrate to the carbon substrate. These results reveal that high activation barriers exist preventing the spillover of hydrogen from the anchored Pd clusters to the carbon substrate.

In the present work methane carbon monoxide hydrogen and the binary mixtures 20 % CH4–80 % H2 80 % CH4–20 % H2 25 % CO–75 % H2 (by volume) were considered as fuels of a naturally aspirated port-fuel injection four-cylinder Volkswagen 1.4 L spark-ignition (SI) engine. The interest in these fuels lies in the fact that they can be obtained from renewable resources such as the fermentation or gasification of residual biomasses as well as the electrolysis of water with electricity of renewable origin in the case of hydrogen. In addition they can be used upon relatively easy modifications of the engines including the retrofitting of existing internal combustion engines. It has been found that the engine gives similar performance regardless the gaseous fuel nature if the air–fuel equivalence ratio (λ) is the same. Maximum brake torque and mean effective pressure values within 45–89 N⋅m and 4.0–8.0 bar respectively have been obtained at values of λ between 1 and 2 at full load engine speed of 2000 rpm and optimum spark-advance. In contrast the nature of the gaseous fuel had great influence upon the range of λ values at which a fuel (either pure or blend) could be used. Methane and methane-rich mixtures with hydrogen or carbon monoxide allowed operating the engine at close to stoichiometric conditions (i.e. 1 < λ < 1.5) yielding the highest brake torque and mean effective pressure values. On the contrary hydrogen and hydrogen-rich mixtures with methane or carbon monoxide could be employed only in the very fuel-lean region (i.e. 1.5 < λ < 2). The behavior of carbon monoxide was intermediate between that of methane and hydrogen. The present study extends and complements previous works in which the aforementioned fuels were compared only under stoichiometric conditions in air (λ = 1). In addition a simple zero-dimensional thermodynamic combustion model has been developed that allows describing qualitatively the trends set by the several fuels. Although the model is useful to understand the influence of the fuels properties on the engine performance its predictive capability is limited by the simplifications made.

We investigate the influence of microstructural traps in hydrogen-assisted fatigue crack growth. To this end a new formulation combining multi-trap stress-assisted diffusion mechanism-based strain gradient plasticity and a hydrogen- and fatigue-dependent cohesive zone model is presented and numerically implemented. The results show that the ratio of loading frequency to effective diffusivity governs fatigue crack growth behaviour. Increasing the density of beneficial traps not involved in the fracture process results in lower fatigue crack growth rates. The combinations of loading frequency and carbide trap densities that minimise embrittlement susceptibility are identified providing the foundation for a rational design of hydrogen-resistant alloys.

The paper addresses the sensitivity to hydrogen embrittlement of heavily cold-drawn wires made of the new generation of lower alloyed duplex stainless steels often referred to as lean duplex grades. It includes comparisons with similar data corresponding to cold-drawn eutectoid and duplex stainless steels. For this purpose fracture tests under constant load were carried out with wires in the as-received condition and fatigue-precracked in air and exposed to ammonium thiocyanate solution. Microstructure and fractographic observations were essential means for the cracking analysis. The effect of hydrogen-assisted embrittlement on the damage tolerance of lean duplex steels was assessed regarding two macro-mechanical damage models that provide the upper bounds of damage tolerance and accurately approximate the failure behavior of the eutectoid and duplex stainless steels wires.

Hydrogen assisted macrodelamination in the pipe elbows of 40-year exploited lateral pipelines located behind the compressor station was studied. The crack on the external surface of the pipe elbow was revealed. Macrodelamination was occurred in the steel being influenced by the joined action of working loads and hydrogen absorbed by metal during long-term operation. The causes of the material degradation were investigated by non-destructive testing using ultrasound thickness meter observing microstructure hydrostatic pressure testing and mechanical properties testing of pipe steel.<br/>Intensive degradation of steel primarily essential reduction of plasticity was revealed. The degradation degree of the pipe elbow steel was higher than of the straight pipe steel regardless of a section was tensioned or compressed. Basing on the tensile tests carried out on cylindrical smooth and notched specimens from the pipe elbow steel it was established that the plasticity of the damaged steel could be measured correctly only on the specimens with a circular notch due to concentration of deformation in the cross section location only. The limitations in using elongation and reduction in area for characterisation of plasticity of the pipe steel with extensive delamination were defined. The diagnostic features of macrodelamination namely an abnormal thickness meter readings and a sharp decrease in hardness and plasticity of the pipe elbow steel were established.

The paper presents the results of the CFD inter-comparison exercise SBEP-V3 performed within the activity InsHyde internal project of the HYSAFE network of excellence in the framework of evaluating the capability of various CFD tools and modelling approaches in predicting the physical phenomena associated to the short and long term mixing and distribution of hydrogen releases in confined spaces. The experiment simulated was INERIS-TEST-6C performed within the InsHyde project by INERIS consisting of a 1 g/s vertical hydrogen release for 240 s from an orifice of 20 mm diameter into a rectangular room (garage) of dimensions 3.78x7.2x2.88 m in width length and height respectively. Two small openings at the front and bottom side of the room assured constant pressure conditions. During the test hydrogen concentration time histories were measured at 12 positions in the room for a period up to 5160 s after the end of release covering both the release and the subsequent diffusion phases. The benchmark was organized in two phases. The first phase consisted of blind simulations performed prior to the execution of the tests. The second phase consisted of post calculations performed after the tests were concluded and the experimental results made available. The participation in the benchmark was high: 12 different organizations (2 non-HYSAFE partners) 10 different CFD codes and 8 different turbulence models. Large variation in predicted results was found in the first phase of the benchmark between the various modelling approaches. This was attributed mainly to differences in turbulence models and numerical accuracy options (time/space resolution and discretization schemes). During the second phase of the benchmark the variation between predicted results was reduced.

A method for determination of hazardous zones for hydrogen installations has been studied. This work has been carried out within the NoE HySafe. The method is based on the Italian Method outlined in Guide 31-30(2004) Guide 31–35(2001) Guide 31-35/A(2001) and Guide 31-35/A; V1(2003). Hazardous zones for a “generic hydrogen refuelling station”(HRS) are assessed based on this method. The method is consistent with the EU directive 1999/92/EC “Safety and Health Protection of Workers potentially at risk from explosive atmospheres” which is the basis for determination of hazardous zones in Europe. This regulation is focused on protection of workers and is relevant for hydrogen installations such as hydrogen refuelling stations repair shops and other stationary installations where some type of work operations will be involved. The method is also based on the IEC standard and European norm IEC/EN60079-10 “Electrical apparatus for explosive gas atmospheres. Part 10 Classification of hazardous areas”. This is a widely acknowledged international standard/norm and it is accepted/approved by Fire and Safety Authorities in Europe and also internationally. Results from the HySafe work and other studies relevant for hydrogen and hydrogen installations have been included in the case study. Sensitivity studies have been carried out to examine the effect of varying equipment failure frequencies and leak sizes as well as environmental condition (ventilation obstacles etc.). The discharge and gas dispersion calculations in the Italian Method are based on simple mathematical formulas. However in this work also CFD (Computational Fluid Dynamics) and other simpler numerical tools have been used to quantitatively estimate the effect of ventilation and of different release locations on the size of the flammable gas cloud. Concentration limits for hydrogen to be used as basis for the extent of the hazardous zones in different situations are discussed.