Publications

To develop safety strategies for the use of hydrogen indoors the HyIndoor project is studying the behaviour of a hydrogen release deflagration or non-premixed flame in an enclosed space such as a fuel cell or its cabinet a room or a warehouse. The paper proposes a safety approach based on safety objectives that can be used to take various scenarios of hydrogen leaks into account for the safe design of Hydrogen and Fuel Cell (HFC) early market applications. Knowledge gaps on current engineering models and unknown influence of specific parameters were identified and prioritized thereby re-focusing the objectives of the project test campaign and numerical simulations. This approach will enable the improvement of the specification of openings and use of hydrogen sensors for enclosed spaces. The results will be disseminated to all stakeholders including hydrogen industry and RCS bodies.

The challenges and approaches of the safety and risk management for the hydrogen production with nuclear-based thermochemical water splitting have been far from sufficiently reported as the thermochemical technology is still at a fledgling stage and the linkage of a nuclear reactor with a hydrogen production plant is unprecedented. This paper focuses on the safety issues arising from the interactions between the nuclear heat source and thermochemical hydrogen production cycle as well between the proximate individual processes in the cycle. As steam is utilized in most thermochemical cycles for the water splitting reaction and heat must be transferred from the nuclear source to hydrogen production plant this paper particularly analyzes and quantifies the heat hazard for the scenarios of start-up and shutdown of the hydrogen production plant. Potential safety impacts on the nuclear reactor are discussed. It is concluded that one of the main challenges of safety and risk management is efficient rejection of heat in a shutdown accident. Several options for the measures to be taken are suggested. Copper-chlorine and sulphur-iodine thermochemical cycles are taken as two representative examples for the hazard analysis. It is expected that these newly reported challenges and approaches could help build the future safety and risk management codes and standards for the infrastructure of the thermochemical hydrogen production.

This paper examines the flame dynamics of vented deflagration in stratified hydrogen layers. It also compares the measured combustion pressure transients with 3D GOTHIC simulations to assess GOTHIC’s capability in simulating the associated phenomena. The experiments were performed in the Large-Scale Vented Combustion Test Facility at the Canadian Nuclear Laboratories. The stratified layer was formed by injecting hydrogen at a high elevation at a constant flow rate. The dominant parameters for vented deflagrations in stratified layers were investigated. The experimental results show that significant overpressures are generated in stratified hydrogen–air mixtures with local high concentration although the volume-averaged hydrogen concentration is non-flammable. The GOTHIC predictions capture the overall pressure dynamics of combustion very well but the peak overpressures are consistently over-predicted particularly with higher maximum hydrogen concentrations. The measured combustion overpressures are also compared with Molkov’s model prediction based on a layer-averaged hydrogen concentration.

Radiative heat fluxes from small to medium-scale hydrogen jet flames (<10 m) compare favorably to theoretical predictions provided the product species thermal emittance and optical flame thickness are corrected for. However recent heat flux measurements from two large-scale horizontally orientated hydrogen flames (17.4 and 45.9 m respectively) revealed that current methods underpredicted the flame radiant fraction by 40% or more. Newly developed weighted source flame radiation models have demonstrated substantial improvement in the heat flux predictions particularly in the near-field and allow for a sensible way to correct potential ground surface reflective irradiance. These updated methods are still constrained by the fact that the flame is assumed to have a linear trajectory despite buoyancy effects that can result in significant flame deformation. The current paper discusses a method to predict flame centerline trajectories via a one-dimensional flame integral model which enables optimized placement of source emitters for weighted multi-source heat flux prediction methods. Flame shape prediction from choked releases was evaluated against flame envelope imaging and found to depend heavily on the notional nozzle model formulation used to compute the density weighted effective nozzle diameter. Nonetheless substantial improvement in the prediction of downstream radiative heat flux values occurred when emitter placement was corrected by the flame integral model regardless of the notional nozzle model formulation used.

Hydrogen leakage in a closed space is one of the causes of serious accidents because of its high detonability. Assuming the situation that hydrogen is accumulated in a closed space two-dimensional numerical simulation for hydrogen oxygen detonation which propagates in stratified fuel and oxidizer with concentration gradient is conducted by using detailed chemical reaction model. The concentration gradient between fuel and oxidizer is expressed by changing the number of hydrogen moles by using sigmoid function. Strength of discontinuity at the boundary is controlled by changing the gain of the function. The maximum pressure history shows that the behaviour of triple points is different depending on the strength of discontinuity between the two kind of gas. In without concentration gradient case the transverse waves are reflected at the boundary because of the sudden change of acoustic impedance ratio between two kind of gas. In contrast in with concentration gradient case the transverse wavs are not reflected in the buffer zone and they are flowed into the oxidizer as its structures are kept. As a result the confined effect declines as the strength of discontinuity between the two kind of gas is weakened and the propagating distance of detonation changes

The development of the temperature field in hydrogen tanks during the filling process has been investigated with Computational Fluid Dynamics (CFD). Measurements from experiments undertaken at the JRC GasTef facility have been used to develop and validate the CFD modelling strategy; by means of the CFD calculations the effect of the injector direction on the temperature distribution has been analysed. It has been found that the dynamics of the temperature field including the development of potentially detrimental phenomena like thermal stratification and temperature inhomogeneity e.g. hot spots can be significantly affected by the injector orientation.

Hydrogen energy is expanding world wide in recent years while hydrogen safety issues have drawn considerable attention. It is widely accepted that accidental hydrogen release in an open air environment will disperse quickly hence not causing significant hydrogen hazards. A hydrogen hazard is more likely to occur when hydrogen is accidentally released in a confined place i.e. parking garages and tunnels. Prediction the consequences of hydrogen detonation is important for hydrogen safety assessment and for ensuring the safety of installations during accidents. Hence an accident scenario of hydrogen release  nd detonation in a tunnel is analysed with GASFLOW-MPI in this paper. GASFLOW-MPI is a well validated parallel CFD code focusing on hydrogen transport combustion and detonation. GASFLOWMPI solves compressible Navier-Stokes equations with a powerful all-speed Arbitrary-Lagrangian-Eulerian (ALE) method hence it can cover both the non-compressible flow during the hydrogen relesase and dispersion phases and the compressible flow during combustion and detonation. A 3D model of a tunnel including eight cars is modelled. Firstly the hydrogen dispersion in the tunnel is calculated. Then the detonation in the tunnel is calculated by manually igniting the hydrogen at the top of the tunnel when the λ criterion is maximum. The pressure loads are calculated to evaluate the consequence of the hazard.

The hourly operation of Thermal Hydrogen electricity markets is modelled. The economic values for all applicable chemical commodities are quantified (syngas ammonia methanol and oxygen) and an hourly electricity model is constructed to mimic the dispatch of key technologies: bi-directional power plants dual-fuel heating systems and plug-in fuel-cell hybrid electric vehicles. The operation of key technologies determines hourly electricity prices and an optimization model adjusts the capacity to minimize electricity prices yet allow all generators to recover costs. We examine 12 cost scenarios for renewables nuclear and natural gas; the results demonstrate emissionsfree ‘energy-only’ electricity markets whose supply is largely dominated by renewables. The economic outcome is made possible in part by seizing the full supply-chain value from electrolysis (both hydrogen and oxygen) which allows an increased willingness to pay for (renewable) electricity. The wholesale electricity prices average $25–$45/ MWh or just slightly higher than the assumed levelized cost of renewable energy. This implies very competitive electricity prices particularly given the lack of need for ‘scarcity’ pricing capacity markets dedicated electricity storage or underutilized electric transmission and distribution capacity.

Short refuelling time and high final state of charge are among the main hydrogen car user's requirements. To meet these requirements without exceeding the tank materials safety limits hydrogen precooling is needed. Filling experiments with different inlet gas temperatures and mass flow rates have been executed using two different types of on-board tanks (type 3 and 4). State of charge has a strong dependency on the inlet gas temperature. This dependency is more visible for type 4 tanks. Lowest precooling temperature (−40 °C) is not always required in order to meet user's requirements so energy savings can be achieved if the initial conditions of the tank are correctly identified. The results of the experiments performed have been compared with the SAE J2601 look-up tables for non-communication fillings. A big safety margin has been observed in these tables. Refuelling could be performed faster and with less demanding precooling requirements if the initial conditions and the configuration of the hydrogen storage system are well known.

In order to facilitate the application of hydrogen energy and ensure its safety the compressed hydrogen storage tank on board needs to be full of hydrogen gas within 3 minutes. Therefore to meet this requirement the effects of refueling parameters on the filling time need to be investigated urgently. For the purpose of solving this issue a novel analytical solution of filling time is obtained from a lumped parameter model in this paper. According to the equation of state for real gas and dimensionless numbers Nu and Re the function relationships between the filling time and the refueling parameters are presented. These parameters include initial temperature initial pressure inflow temperature final temperature and final pressure. These equations are used to fit the reference data the results of fitting show good agreement. Then the values of fitting parameters are further utilized so as to verify the validity of these formulas. We believe this study can contribute to control the hydrogen filling time and ensure the safety during fast filling process.

"The current practise of focusing the periodic retesting of composite cylinders primarily on the hydraulic pressure test has to be evaluated as critical - with regard to the damage of the specimen as well as in terms of their significance. This is justified by micro damages caused to the specimen by the test itself and by a lack of informative values. Thus BAM Federal Institute of Materials Research and Testing (Germany) uses a new approach of validation of composite for the determination of re-test periods. It enables the description of the state of a population of composite cylinders based on destructive tests parallel to operation.<br/>An essential aspect of this approach is the prediction of residual safe service life. In cases where it cannot be estimated by means of hydraulic load cycle tests as a replacement the creep or burst test remains. As a combination of these two test procedures BAM suggests the ""slow burst test SBT"". On this a variety of about 150 burst test results on three design types of cylinders with plastic liners are presented. For this purpose both the parameters of the test protocol as well as the nature and intensity of the pre-damage artificially aged test samples are analysed statistically. This leads first to an evaluation of the different types of artificial ageing but also to the clear recommendation that conventional burst tests be substituted totally if indented for assessment of composite pressure receptacles."

The highly combustible nature of hydrogen poses a great hazard creating a number of problems with its safety and handling. As a part of safety studies related to the use of hydrogen in a confined environment it is extremely important to have a good knowledge of the dispersion mechanism.<br/>The present work investigates the concentration field and flammability envelope from a small scale leak. The hydrogen is released into a 0.47 m × 0.33 m x 0.20 m enclosure designed as a 1/15 – scale model of a room in a nuclear facility. The performed tests evaluates the influence of the initial conditions at the leakage source on the dispersion and mixing characteristics in a confined environment. The role of the leak location and the presence of obstacles are also analyzed. Throughout the test during the release and the subsequent dispersion phase temporal profiles of hydrogen concentration are measured using thermal conductivity gauges within the enclosure. In addition the BOS (Background Oriented Schlieren) technique is used to visualise the cloud evolution inside the enclosure. These instruments allow the observation and quantification of the stratification effects.

As the depletion of traditional fossil fuels and environmental pollution become a serious problem of human society researchers are actively finding renewable green energy sources. Considered as a clean efficient and renewable alternative Hydrogen energy is considered the most promising energy source. However the safe and efficient storage of hydrogen has become the major problem that hinders its application. To solve this gap this paper proposes to utilize surfactant modified graphene for hydrogen storage. With Hummers method and ultrasonic stripping method this study prepared graphene from graphene oxide with NaBH4. Surfactant sodium dodecylbenzene sulfonate (SDBS) was used as a dispersant during the reduction process to produce the dispersion-stabilized graphene suspensions. The characteristics of the graphene suspensions then were examined by XRD SEM TEM FT-IR Raman XPS TG and N2 adsorption-desorption tests. The hydrogen adsorption properties of the samples were investigated with Langmuir and Freundlich fitting. The results show that the adsorption behavior is consistent with the Freundlich adsorption model and the process is a physical adsorption.

The test data of static burst strength and load cycle strength of composite pressure vessels are often described by GAUSSian normal or WEIBULL distribution function to perform safety analyses. The goodness of assumed distribution function plays a significant role in the inferential statistics to predict the population properties by using limited test data. Often GAUSSian and WEIBULL probability nets are empirical methods used to validate the distribution function; Anderson-Darling and Kolmogorov-Smirnov tests are the mostly favorable approaches for Goodness of Fit. However the different approaches used to determine the parameters of distribution function lead mostly to different conclusions for safety assessments.<br/>In this study six different methods are investigated to show the variations on the rates for accepting the composite pressure vessels according to GTR No. 13 life test procedure. The six methods are: a) Norm- Log based method b) Least squares regression c) Weighted least squares regression d) A linear approach based on good linear unbiased estimators e) Maximum likelihood estimation and f) The method of moments estimation. In addition various approaches of ranking function are considered. In the study Monte Carlo simulations are conducted to generate basic populations based on the distribution functions which are determined using different methods. Then the samples are extracted randomly from a population and evaluated to obtain acceptance rate. Here the “populations” and “samples” are corresponding to the burst strength or load cycle strength of the pressure vessels made from composite material and a plastic liner (type 4) for the storage of hydrogen. To the end the results are discussed and the best reliable methods are proposed.

Integrity of natural gas transmission systems is of great importance for energy and environmental security. Deterioration occurs in gas transit pipelines due to operational conditions and action of corrosion and hydrogenating media and leads to changes in microstructure and mechanical properties of pipeline steels which influences on pipeline performance. Hydrogenation of metal during corrosion process together with working stresses facilitates a development of in-bulk damaging at nano- and microscales. Reducing brittle fracture resistance of pipeline steels under operation increases significantly a failure risk of gas pipelines associated with in-bulk material degradation. Therefore hydrogen assisted degradation of pipelines steels under operation calls for effective methods for in-laboratory accelerated degradation. The present study is devoted to the development of the procedure of laboratory simulation of in-service degradation of pipeline steels. The role of hydrogen in degradation of pipeline steels was analysed. The procedure of accelerated degradation of pipeline steels under the combined action of axial loading and hydrogen charging was developed and induced in the laboratory. The procedure was consisted in consistently subjecting of specimens to electrolytic hydrogen charging to an axial loading up and to an artificial aging. Pipeline steels in the different states (as-received post-operated aged and after in-laboratory degradation) were investigated. The tensile mechanical behaviour of steels and impact toughness were experimentally studied. It was definitely concluded that the applied procedure caused the changes in the metal mechanical properties at the same level compared to the properties degradation due to operation. The developed procedure enables on a laboratory scale simulating of pipeline steel degradation during long-term operation under simultaneous action of hydrogenation and working loading and it makes possible to predict the mechanical behaviour of pipeline steels during service.

<br/>Cyclic Voltammetry Measurements performed on a Cobaloxime Catalyst designed for photochemical hydrogen production.

The paper describes CFD modelling of lean hydrogen mixture deflagrations. Large eddy simulation (LES) premixed combustion model developed at the University of Ulster to account phenomena related to large-scale deflagrations was adjusted specifically for lean hydrogen-air flames. Experiments by Kumar (2006) on lean hydrogen-air mixture deflagrations in a 120 m3  vessel at initially quiescent conditions were simulated. 10% by volume hydrogen-air mixture was chosen for simulation to provide stable downward flame propagation; experiments with the smallest vent area 0.55 m2  were used as having the least apparent flame instabilities affecting the pressure dynamics. Deflagrations with igniter located centrally near vent and at far from the vent wall were simulated. Analysis of simulation results and experimental pressure dynamics demonstrated that flame instabilities developing after vent opening made the significant contribution to maximum overpressure in the considered experiments. Potential causes of flame instabilities are discussed and their comparative role for different igniter locations is demonstrated.

This report summarises key themes emerging from the Energy Technologies Institute’s (ETI) project ‘Enabling efficient networks for low carbon futures’. The project aimed to explore the options for reforming the governance and regulatory arrangements to enable major changes to and investment in the UK’s energy network infrastructures. ETI commissioned four expert perspectives on the challenges and options facing the UK.

This paper is an investigation of the spontaneous ignition process of high-pressure hydrogen and hydrogen-methane mixtures injected into air. The experiments were conducted in a closed channel filled with air where the hydrogen or hydrogen–methane mixture depressurised through different tubes (diameters d = 6 10 and 14 mm and lengths L = 10 25 40 50 75 and 100 mm). The methane addition to the mixture was 5% and 10% vol. The results showed that only 5% methane addition may increase even 2.67 times the pressure at which the mixture may ignite in comparison to the pressure of the pure hydrogen flow. The 10% of methane addition did not provide an ignition for burst pressures up to 15.0 MPa in the geometrical configuration with the longest tube (100 mm). Additionally the simulations of the experimental configuration with pure hydrogen were performed with the use of KIVA numerical code with full kinetic reaction mechanism.

This work presents a parametric study on the similitude between hydrogen and helium distribution when released in the air by a source located inside of a naturally ventilated enclosure with two vents. Several configurations were experimentally addressed in order to improve knowledge on dispersion. Parameters were chosen to mimic operating conditions of hydrogen energy systems. Thus the varying parameters of the study were mainly the source diameter the releasing flow rate the volume and the geometry of the enclosure. Two different experimental set-ups were used in order to vary the enclosure's height between 1 and 2 m. Experimental results obtained with helium and hydrogen were compared at equivalent flow rates determined with existing similitude laws. It appears for the plume release case that helium can suitably be used for predicting hydrogen dispersion in these operating designs. On the other hand – when the flow turns into a jet – non negligible differences between hydrogen and helium dispersion appear. In this case helium – used as a direct substitute to hydrogen – will over predict concentrations we would get with hydrogen. Therefore helium concentration read-outs should be converted to obtain correct predictions for hydrogen. However such a converting law is not available yet.

This paper revisits the theoretical concepts of lock-in mechanisms to analyse transition processes in energy production and road transportation in the Nordic countries focussing on three technology platforms: advanced biofuels e-mobility and hydrogen and fuel cell electrical vehicles. The paper is based on a comparative analysis of case studies.<br/>The main lock-in mechanisms analysed are learning effects economies of scale economies of scope network externalities informational increasing returns technological interrelatedness collective action institutional learning effects and the differentiation of power.<br/>We show that very different path dependencies have been reinforced by the lock-in mechanisms. Hence the characteristics of existing regimes set the preconditions for the development of new transition pathways. The incumbent socio-technical regime is not just fossil-based but may also include mature niches specialised in the exploitation of renewable sources. This implies a need to distinguish between lock-in mechanisms favouring the old fossil-based regime well-established (mature) renewable energy niches or new pathways.

This report contains information on the relative risks of natural gas and hydrogen fires particularly regarding their visibility. The fires considered are those that could occur on the H100 Fife trial network. The H100 Fife project will connect a number of residential houses to 100% hydrogen gas supply. The project includes hydrogen production storage and a new distribution network. From a review of large and small-scale tests and incidents it is concluded that hydrogen flames are likely to be clearly visible for releases above 2 bar particularly for larger release rates. At lower pressures hydrogen flame visibility will be affected by ambient lighting background colour and release orientation although this is also the case for natural gas. Potential safety implications from lack of flame  visibility are that SGN workers other utility workers or members of the public could inadvertently come into contact with an ignited release. However some releases would be detected through noise thrown soil or interaction with objects. From a workshop and review of risk reduction measures and analysis of historical interference damage incidents it is concluded that flames with the potential for reduced visibility are adequately controlled. This is due to the likelihood of such scenarios occurring being low and that the consequences of coming into contact with such a flame are unlikely to be severe. These conclusions are supported by cost-benefit analysis that shows that no additional risk mitigation measures are justified for the H100 project. It is recommended that the cost-benefit analysis is revisited before applying the approach to a network wider than the H100 project. It was observed that the addition of odorant at relevant concentrations did not have an effect on the visibility of hydrogen flames.

This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.

This paper proposes that whilst the exact pathway to decarbonising heat in the UK is not yet clear there are a range of actions that could be taken in the next ten years to shift heat onto the right route to meet our 2050 net zero obligation. We already possess many of the skills and technologies required but there are a number of significant barriers preventing a spontaneous movement towards low carbon heat on the scale required – a starting impulse is needed.<br/><br/>Energy efficiency and low carbon heating have the potential to radically improve the quality of life of not just the poorest in our society but all residents of the United Kingdom. With the right approach the decarbonisation of heat can improve health outcomes for millions create new jobs in manufacturing and construction reduce air pollution in our cities and reduce the burden on our health service. This in addition to leading the world in mitigating the climate emergency.

A systematic method for obtaining a novel electrode structure based on PtCoMn ternary alloy catalyst supported on graphitic carbon nanofibers (CNF) for hydrogen evolution reaction (HER) in acidic media is proposed. Ternary alloy nanoparticles (Co0.6Mn0.4 Pt) with a mean crystallite diameter under 10 nm were electrodeposited onto a graphitic support material using a two-step pulsed deposition technique. Initially a surface functionalisation of the carbon nanofibers is performed with the aid of oxygen plasma. Subsequently a short galvanostatic pulse electrodeposition technique is applied. It has been demonstrated that if pulsing current is employed compositionally controlled PtCoMn catalysts can be achieved. Variations of metal concentration ratios in the electrolyte and main deposition parameters such as current density and pulse shape led to electrodes with relevant catalytic activity towards HER. The samples were further characterised using several physico-chemical methods to reveal their morphology structure chemical and electrochemical properties. X-ray diffraction confirms the PtCoMn alloy formation on the graphitic support and energy dispersive X-ray spectroscopy highlights the presence of the three metallic components from the alloy structure. The preliminary tests regarding the electrocatalytic activity of the developed electrodes display promising results compared to commercial Pt/C catalysts. The PtCoMn/CNF electrode exhibits a decrease in hydrogen evolution overpotential of about 250 mV at 40 mA cm⁻² in acidic solution (0.5 M H₂SO₄) when compared to similar platinum based electrodes (Pt/CNF) and a Tafel slope of around 120 mV dec−1 indicating that HER takes place under the Volmer-Heyrovsky mechanismm

Membrane reactors for hydrogen production can increase both the hydrogen production efficiency at small scale and the electric efficiency in micro-cogeneration systems when coupled with Polymeric Electrolyte Membrane fuel cells. This paper discusses the achievements of three European projects (FERRET FluidCELL BIONICO) which investigate the application of the membrane reactor concept to hydrogen production and micro-cogeneration systems using both natural gas and biofuels (biogas and bio-ethanol) as feedstock. The membranes used to selectively separate hydrogen from the other reaction products (CH4 CO2 H2O etc.) are of asymmetric type with a thin layer of Pd alloy (<5 μm) and supported on a ceramic porous material to increase their mechanical stability. In FERRET the flexibility of the membrane reactor under diverse natural gas quality is validated. The reactor is integrated in a micro-CHP system and achieves a net electric efficiency of about 42% (8% points higher than the reference case). In FluidCELL the use of bio-ethanol as feedstock for micro-cogeneration Polymeric Electrolyte Membrane based system is investigated in off-grid applications and a net electric efficiency around 40% is obtained (6% higher than the reference case). Finally BIONICO investigates the hydrogen production from biogas. While BIONICO has just started FERRET and FluidCELL are in their third year and the two prototypes are close to be tested confirming the potentiality of membrane reactor technology at small scale.

HyNet North West (NW) is an innovative integrated low carbon hydrogen production distribution and carbon capture utilisation and storage (CCUS) project. It provides hydrogen distribution and CCUS infrastructure across Liverpool Manchester and parts of Cheshire in support of the Government’s Clean Growth Strategy (CGS) and achievement of the UK’s emissions reduction targets.<br/>Hydrogen will be produced from natural gas and sent via a new pipeline to a range of industrial sites for injection as a blend into the existing natural gas network and for use as a transport fuel. Resulting carbon dioxide (CO2) will be captured and together with CO2 from local industry which is already available sent by pipeline for storage offshore in the nearby Liverpool Bay gas fields. Key data for the Project are presented in Table ES1.

There is a need for alternative fuels in the shipping sector for two main motivations: to deliver a reduction in local pollutants and comply with existing regulation; and to mitigate climate change and cut greenhouse gas emissions. However any alternative fuel must meet a range of criteria to become a viable option. Key among them is the requirement that it can deliver emissions reductions over its full life-cycle. For a set of fuels comprising both conventional and alternative fuels together with associated production pathways this paper presents a life-cycle assessment with respect to six emissions species: local pollutants sulphur oxides nitrogen oxides and particulate matter; and greenhouse gases carbon dioxide methane and nitrous oxide. While the analysis demonstrates that no widely available fuel exists currently to deliver on both motivations some alternative fuel options have the potential if key barriers can be overcome. Hydrogen or other synthetic fuels rely on decarbonisation of both energy input to production and other feedstock materials to deliver reductions in greenhouse gas emissions. Similarly bio-derived fuels can be an abatement option but only if it can be ensured that land-use change whilst growing biomass does not impact wider potential savings and the sector is able to compete sufficiently for their use. These examples show that crucial barriers are located upstream in the respective fuel life-cycle and that the way to overcome them may reside beyond the scope of the shipping sector alone.

This study is a review of hydrogen station patents using the Derwent Innovation system and also a secondary screening. This was undertaken by the researchers to better understand and identify hydrogen station trends. The review focuses on analyzing the developing trends of patent technologies associated with a hydrogen station. The results of the review indicated that the countries with the major distribution of patents were Japan China the USA and Europe. Japan is leading the developmental trajectory of hydrogen stations. The results of the analysis found the leading developers of these patented technologies are Kobe Steel Nippon Oil Toyota and Honda. Other active patent developers analyzed include Linde Hyundai and Texaco. The review concludes with a suggestion that using a patent analysis methodology is a good starting point to identify evaluate and measure the trend in hydrogen station commercial development.

The possibility of flame acceleration (FA) and deflagration-to-detonation transition (DDT) when homogeneous hydrogen-carbon monoxide-air (H2-CO-air) mixtures are used rises the need for an efficient simulation approach for safety assessment. In this study a modelling approach for H2-CO-air flames incorporating deflagration and detonation within one framework is presented. It extends the previous work on H2-air mixtures. The deflagration is simulated by means of the turbulent flame speed closure model incorporating a quenching term. Since high flow velocities e.g. the characteristic speed of sound of the combustion products are reached during FA the flow passing obstacles generates turbulence at high enough levels to partially quench the flame. Partial flame quenching has the potential to stall the onset of detonation. An altered formulation for quenching is introduced to the modelling approach to better account for the combustion characteristics for accelerating lean H2-CO-air flames. The presented numerical approach is validated with experimental flame velocity data of the small-scale GraVent test rig [1] with homogeneous fuel contents of 22.5 and 25.0 vol-% and fuel compositions of 75/25 and 50/50 vol-% H2/CO respectively. The impact of the quenching term is further discussed on simulations of the FZK-7.2m test rig [2] whose obstacle spacing is smaller than the spacing in the GraVent test rig.

The competition between chemical energy release rate and volumetric expansion related to shock wave’s dynamics is of primary importance for a number of situations relevant to explosion safety. While studies have been performed on this topic over the years they have been limited to mixtures with monotonous energy release profile. In the present study the ignition of H2-NO2/N2O4 mixtures which exhibit a single-step or a two-step energy release rate profile depending on the equivalence ratio has been investigated under volumetric expansion conditions. The rate of expansion has been calculated using the Taylor-Sedov solution and accounted for using 0-D numerical simulations with time-dependent specific volume. The results were analyzed in terms of a Damkohler number defined as the ratio of the expansion to ignition times. For mixtures with non-monotonous energy release rate profiles two critical Damkohler numbers can be identified one for each of the steps of energy release. It was also shown that the fluid element which is the most likely to ignite corresponds to the one behind a shock propagating at the Chapman-Jouguet velocity. The thermo-chemical dynamics have been analyzed about the critical conditions using energy release rate per reaction rate of production and sensitivity analyses.

This paper presents a new Fuel Cell Fuel Consumption Minimization Strategy (FCFCMS) for Hybrid Electric Vehicles (HEVs) powered by a fuel cell and an energy storage system in order to minimize as much as possible the consumption of hydrogen while maintaining the State Of Charge (SOC) of the battery. Compared to existing Energy Management Strategies (EMSs) (such as the well-known State Machine Strategy (SMC) Fuzzy Logic Control (FLC) Frequency Decoupling and FLC (FDFLC) and the Equivalent Consumption Minimization Strategy (ECMS)) the proposed strategy increases the overall vehicle energy efficiency and therefore minimizes the total hydrogen consumption while respecting the constraints of each energy and power element. A model of a hybrid vehicle has been built using the TruckMaker/MATLAB software. Using the Urban Dynamometer Driving Schedule (UDDS) which includes several stops and accelerations the performance of the proposed strategy has been compared with these different approaches (SMC FLC FDFLC and ECMS) through several simulations.

Ignition conditions and risks of ignition on a permissible value of hydrogen concentration in purge gas prescribed by HFCV-GTR were reevaluated. Experiments were conducted to investigate burning behavior and thermal influence of continuous evacuation of hydrogen under continuous purge of air / hydrogen premixed gas which is close to an actual purge condition of FCV and thermal evacuation of hydrogen. As a result of the re-evaluation it was shown from the viewpoint of safety that the permissible value of hydrogen concentration in purge gas prescribed by the current HFCV GTR is appropriate.

Worldwide the road transport sector typically arises as one of the main sources of air pollutants due to its high energy intensity and the use of fossil fuels. Thus governments and social agents work on the development and prospective planning of decarbonisation strategies oriented towards sustainable transport. In this regard the increase in the use of alternative fuels is the recurrent approach to energy planning e.g. through the promotion of electric vehicles biofuels natural gas liquefied petroleum gas etc. However there is a lack of comprehensive information on the techno-economic performance of production pathways for alternative fuels. The acquisition of robust techno-economic data is still a challenge for energy planners modellers analysts and policy-makers when building their prospective models to support decision-making processes. Hence this article aims to fill this gap through a deep literature review including the most representative production routes for a wide range of road transportation fuels. This led to the development of datasets including investment costs operating and maintenance costs and transformation efficiencies for more than 40 production pathways. The techno-economic data presented in this work are expected to be especially useful to those energy actors interested in performing long-term studies on the transition to a sustainable transport system.

Hydrogen has emerged as an important part of the clean energy mix needed to ensure a sustainable future. Falling costs for hydrogen produced with renewable energy combined with the urgency of cutting greenhouse-gas emissions has given clean hydrogen unprecedented political and business momentum.



This paper from the International Renewable Energy Agency (IRENA) examines the potential of hydrogen fuel for hard-to-decarbonise energy uses including energy-intensive industries trucks aviation shipping and heating applications. But the decarbonisation impact depends on how hydrogen is produced. Current and future sourcing options can be divided into grey (fossil fuel-based) blue (fossil fuel-based production with carbon capture utilisation and storage) and green (renewables-based) hydrogen. Green hydrogen produced through renewable-powered electrolysis is projected to grow rapidly in the coming years.



Among other findings:



Important synergies exist between hydrogen and renewable energy. Hydrogen can boost renewable electricity market growth and broaden the reach of renewable solutions.

• Electrolysers can add demand-side flexibility. In advanced European energy markets electrolysers are growing from megawatt to gigawatt scale.
• Blue hydrogen is not inherently carbon free. This type of production requires carbon-dioxide (CO2) monitoring verification and certification.
• Synergies may exist between green and blue hydrogen deployment given the chance for economies of scale in hydrogen use or logistics.
• A hydrogen-based energy transition will not happen overnight. Hydrogen use is likely to catch on for specific target applications. The need for new supply infrastructure could limit hydrogen use to countries adopting this strategy.
• Dedicated hydrogen pipelines have existed for decades and could be refurbished along with existing gas pipelines. The implications of replacing gas abruptly or changing mixtures gradually should be further explored.

Trade of energy-intensive commodities produced with hydrogen including “e-fuels” could spur faster uptake or renewables and bring wider economic benefits.

This report shows that low-carbon hydrogen supply at scale is economically and environmentally feasible and will have significant societal benefits if the right localised approach and best-practices for production are used. The report also demonstrates that there is not one single hydrogen production pathway to achieve low lifecycle greenhouse gas (GHG) emissions but rather the need for a fact-based approach that leverages regional resources and includes a combination of different production pathways. This will achieve both emission and cost reductions ultimately helping to decarbonize the energy system and limit global warming.

In 2020 more than 15 countries launched major hydrogen plans and policies and industry players announced new projects of more than 35GW until 2030. As this hydrogen momentum accelerates it is increasingly clear that decision makers must put the focus on decarbonization to ensure hydrogen can fulfil its potential as a key solution in the global clean energy transition making a significant contribution to net zero emissions. To support this effort the two-part Hydrogen Council report provides new data based on an assessment of the GHG emissions generated through different hydrogen supply pathways and the lifecycle GHG emissions for different hydrogen applications (see report part 1 – A Life-cycle Assessment). In addition the report explores 3 hypothetical hydrogen supply scenarios to measure the feasibility and impact of deploying renewable and low-carbon hydrogen at scale (report part 2 – Potential Supply Scenarios).

The report outlines that there are many ways of producing hydrogen and although GHG emissions vary widely very high CO2 savings can be achieved across a broad range of different hydrogen production pathways and end-uses. For example while “green” hydrogen produced through water electrolysis with renewable power achieves the lowest emissions “blue” hydrogen produced from natural gas with high CO2 capture rate and storage can also achieve low emissions if best technologies are used and best practices are followed. Across eight illustrative pathways explored in the report analysis shows that if hydrogen is used significant GHG emission reductions can be made: as much as 60-90% or more compared to conventional fossil alternatives. The study also looked into the gross water demand of hydrogen supply pathways. Water electrolysis has a very low specific water demand of 9 kg per kg of hydrogen compared to cooling of thermal power plants (hundreds of kg/kg) or biomass cultivation (hundreds to thousands of kg/kg).

Furthermore low-carbon hydrogen supply at scale is fully achievable. Having investigated two hypothetical boundary scenarios (a “green-only” and a “blue-only” scenario) to assess the feasibility and impact of decarbonized hydrogen supply the report found that both scenarios are feasible: they are not limited by the world’s renewables potential or carbon sequestration (CCS) capacities and they do not exceed the speed at which industry can scale. In the Hydrogen Council’s “Scaling up” study a demand of 21800 TWh hydrogen has been identified for the year 2050. To achieve this a compound annual growth rate of 30-35% would be needed for electrolysers and CCS. This deployment rate is in line with the growth of the offshore wind and solar PV industry over the last decade.

Hydrogen Council data released in January 2020 showed that a wide range of hydrogen applications can become competitive by 2030 driven also by falling costs of renewable and low-carbon hydrogen[1]. The new study indicates that a combination of “green” and “blue” production pathways would lead to hydrogen cost reductions relative to either boundary scenario. By making use of the near-term cost advantage of “blue” while also scaling up “green” hydrogen as the most cost-efficient option in many regions in the medium and long-term the combined approach lowers average hydrogen costs between now and 2050 relative to either boundary scenario.

Part 1 – A Life-cycle Assessment

• The life-cycle assessment (LCA) analysis in this study addresses every aspect of the supply chain from primary energy extraction to end use. Eight primary-energy-to-hydrogen value chains have been selected for illustrative purposes.
• Across the hydrogen pathways and applications depicted very high to high GHG emission reduction can be demonstrated using green (solar wind) and blue hydrogen.
• In the LCA study renewables + electrolysis shows strongest GHG reduction of the different hydrogen supply pathways assessed in this study with a best-case blue hydrogen pathway also coming into the same order of magnitude.

Part 2 – Potential Supply Scenarios

• Currently the vast majority of hydrogen is produced by fossil pathways. To achieve a ten-fold build-out of hydrogen supply by 2050 as envisaged by the Hydrogen Council in its ‘Scaling Up’ report (2017) the existing use of hydrogen – and all its many potential new roles – need to be met by decarbonized sources.
• Three hypothetical supply scenarios with decarbonized hydrogen sources are considered in the study: 1) a “green-only” renewables-based world; 2) a “blue-only” world relying on carbon sequestration; and 3) a combined scenario that uses a region-specific combination of green and blue hydrogen based on the expected regional cost development of each source.
• The study finds that a decarbonized hydrogen supply is possible regardless of the production pathway: while both the green and blue boundary scenario would be highly ambitious regarding the required speed of scale-up they do not exceed the world’s resources on either renewable energy or carbon sequestration capabilities.
• A combination of production pathways would result in the least-cost global supply over the entire period of scale-up. It does so by making best use of the near-term cost advantage of “blue” in some regions while simultaneously achieving a scale-up in electrolysis.
• In reality the decarbonized supply scenario will combine a range of different renewable and low-carbon hydrogen production pathways that are optimally suited to local conditions political and societal preferences and regulations as well as industrial and cost developments for different technologies.

You can download the full reports from the Hydrogen Council website

Hydrogen Council Report- Decarbonization Pathways Part 1: Life Cycle Assessment here

Hydrogen Council Report-Decarbonization Pathways Part 2: Supply Scenarios here

An executive summary of the whole project can be found here

Car park fires are known to be dangerous due to the risk of fast fire spread from one car to another. In general no fatalities are recorded in such fires but they may have a great cost in relation to damaged cars and structural repair. A very recent example is the Liverpool multi-storey car park fire from December 31 2017. It destroyed 1400 cars and parts of the building structure collapsed. This questions the validity of current design praxis of car parks. Literature studies assumes a 12 minutes period for the fire spread from one gasoline fuelled car to another. Statistical research and test from the European commission of steel structures states that in an open car park at most 3-4 vehicles are expected to be on fire at the same time.<br/>A number of investigations have been made concerning vehicles performance in car park fires but only a few are concerned with hydrogen-fuelled vehicles (HFV). It is therefore important to investigate how these new vehicles may contribute to potential fire spread scenario. The aim of the paper is to report the outcome of car park fire spread simulations involving common fuelled and hydrogen fuelled cars. The case study is based on a typical car park found in Denmark. The simulation applied numerical models implemented in the Fire Dynamic Simulator (FDS). In particular the focus of the study is on the influence of the parking distance to fire spread to adjacent vehicles in case a TPRD is activated during a car fire. The results help understanding whether different design rules should be envisaged for such structures or how a sufficient safety level can be obtained by ensuring specific parking condition for the hydrogen-fuelled cars.

Thermal power plants face substantial challenges to remain competitive in energy systems with high shares of variable renewables especially inflexible integrated gasification combined cycles (IGCC). This study addresses this challenge through the integration of Gas Switching Combustion (GSC) and Membrane Assisted Water Gas Shift (MAWGS) reactors in an IGCC plant for flexible electricity and/or H₂ production with inherent CO₂ capture. When electricity prices are high H₂ from the MAWGS reactor is used for added firing after the GSC reactors to reach the high turbine inlet temperature of the H-class gas turbine. In periods of low electricity prices the turbine operates at 10% of its rated power to satisfy the internal electricity demand while a large portion of the syngas heating value is extracted as H₂ in the MAWGS reactor and sold to the market. This product flexibility allows the inflexible process units such as gasification gas treating air separation unit and CO2 compression transport and storage to operate continuously while the plant supplies variable power output. Two configurations of the GSC-MAWGS plant are presented. The base configuration achieves 47.2% electric efficiency and 56.6% equivalent hydrogen production efficiency with 94.8–95.6% CO₂ capture. An advanced scheme using the GSC reduction gases for coal-water slurry preheating and pre-gasification reached an electric efficiency of 50.3% hydrogen efficiency of 62.4% and CO₂ capture ratio of 98.1–99.5%. The efficiency is 8.4%-points higher than the pre-combustion CO₂ capture benchmark and only 1.9%-points below the unabated IGCC benchmark.

The large-scale storage of hydrogen plays a fundamental role in a potential future hydrogen economy. Although the storage of gaseous hydrogen in salt caverns already is used on a full industrial scale the approach is not applicable in all regions due to varying geological conditions. Therefore other storage methods are necessary. In this article options for the large-scale storage of hydrogen are reviewed and compared based on fundamental thermodynamic and engineering aspects. The application of certain storage technologies such as liquid hydrogen methanol ammonia and dibenzyltoluene is found to be advantageous in terms of storage density cost of storage and safety. The variable costs for these high-density storage technologies are largely associated with a high electricity demand for the storage process or with a high heat demand for the hydrogen release process. If hydrogen is produced via electrolysis and stored during times of low electricity prices in an industrial setting these variable costs may be tolerable.

Our gas network is one of the best developed in the world providing safe secure affordable energy to homes and businesses across the UK.<br/><br/>To meet the biggest energy challenge of our generation – making deep cuts to carbon emissions by 2050 – it needs to embrace new technology which builds on these strengths and delivers the integrated flexible network of the future. This briefing sets out how it is already doing that. Take a look at our Gas Futures Messages booklet attached.

As hydrogen-air mixtures are flammable in a wide range of concentrations and the minimum ignition energy is low compared to hydrocarbon fuels the safe handling of hydrogen is of utmost importance. Additional hazards may arise with the accidental spill of liquid hydrogen. Such a release of LH2 leads to a formation of a cryogenic pool a dynamic vaporization process and consequently a dispersion of gaseous hydrogen into the environment. Several LH2 release experiments as well as modelling approaches address this phenomenology. In contrast to existing approaches a new CFD model capable of simulating liquid and gaseous distribution was developed at Forschungszentrum Jülich. It is validated against existing experiments and yields no substantial lacks in the physical model and reveals a qualitatively consistent prediction. Nevertheless the deviation between experiment and simulation raises questions on the completeness of the database in particular with regard to the boundary conditions and available measurements.

This paper considers potential import routes for low-carbon and renewable hydrogen (H2) to main European markets like Germany. In particular it analyses claims made by Hydrogen Europe and subsequently picked up by the European Commission in its Hydrogen Strategy that there will be 40GW of electrolyser capacity in nearby countries providing hydrogen imports to Europe by 2030.   The analysis shows that by 2030 potential demand for H2 could be high enough to initiate some limited international hydrogen trade most likely between European countries initially rather than from outside Europe. Geographically a northern hydrogen cluster around Netherlands and NW Germany will be more significant for hydrogen demand while southern Europe is more likely to have surplus low cost renewable power generation.  The paper considers potential H2 exporters to Europe including Ukraine and North African countries (in line with the proposal from Hydrogen Europe) as well as Norway and Russia. (The research pre-dates recent political and military tensions between Russia and Ukraine which are likely to influence future development pathways).   The supply cost of hydrogen in 2030 is predicted to be in a reasonably (and perhaps surprisingly) narrow band around €3/kg from various sources and supply chains. The paper concludes that overall while imports of hydrogen to Europe are certainly possible in the longer term there are many challenges to be addressed. This conclusion supports the growing consensus that development of low carbon hydrogen certainly within Europe is likely to start within relatively local hydrogen clusters with some limited bilateral trade.

The research paper can be found on their website

The aim of this study was the syngas production by the gasification of plastic waste (polyethylene polypropylene and terephthalate polyethylene). Ca Ce La Mg and Mn were used to promote the Ni/ZSM-5 catalyst in order to enhance the production of higher syngas yield. The modified catalysts can enhanced the reaction rate of the pyrolysis process and resulting in high syngas in the product yields. Especially cerium lanthanum promoted catalysts can enhance the yield of syngas. The effect of the reaction temperature and nitrogen/oxygen ratio of the carrier gas was also investigated. The maximum syngas production was obtained with lanthanum catalyst (112.2 mmol/g (95%N2 and 5%O2) and 130.7 mmol/g (90%N2 and 10%O2) at 850 °C. Less carbon depositions was found at 850 °C or even by the using of catalyst and more oxygen in the carrier gas. The oxygen content of the pyrolysis-gasification atmosphere had a key role to the syngas yield and affects significantly the carbon-monoxide/carbon-dioxide ratio. Catalysts can also accelerate the methanization reactions and isomerize the main carbon frame. Increasing in both temperature and oxygen in the atmosphere led to higher n-paraffin/n-olefin ratio and more multi-ring aromatic hydrocarbons in pyrolysis oils. The concentration of hydrocarbons containing oxygen and branched compounds was also significantly affected by catalysts.

Hydrogen is regarded as a potential solution to address future energy demands and environmental protection challenges. This study assesses the triple bottom line (TBL) sustainability performance of hydrogen as an automotive fuel for Western Australia (WA) using a life cycle approach. Hydrogen is considered to be produced through water electrolysis. Two scenarios current grid electricity and future renewable-based hydrogen were compared with gasoline as a base case. The results show that locally produced grid electricity-based hydrogen is good for local jobs but exhibits higher environmental impacts and negative economic benefits for consumers when compared to gasoline. After incorporating wind-generated electricity reductions of around 69% and 65% in global warming potential (GWP) and fossil fuel depletion (FFD) respectively were achieved compared to the base case gasoline. The land utilization for the production of hydrogen is not a problem as Western Australia has plenty of land to accommodate renewable energy projects. Water for hydrogen feedstock could be sourced through seawater desalination or from wastewater treatment plants in WA. Hydrogen also performed better than gasoline in terms of human health and conservation of fossil fuel indicators under the renewable energy scenario. Local job creation potential of hydrogen was estimated to be 1.29E-03 man-hours/VKT. It has also been found that the cost of hydrogen fuel cell vehicles (HFCV) needs to be similar to that of gasoline vehicles (GV) in order to be comparable with the gasoline life cycle cost per vehicle kilometre travel (VKT).

Webinar to accompany the launch of the Cadent Future Role of Gas in Transport report which can be found here

There is a huge quantity of energy needs/demands for multiple developmental and domestic activities in the modern era. And in this context consumption of more non-renewable energy is reported and created many problems or issues (availability of fossil fuel stocks in the future period causes a huge quantity of toxic gases or particles or climatic change effects) at the global level. And only sustainable or renewable fuel development can provide alternate fuel and we report from various biological agents processes including microbial biofuel cell applications for future energy needs only. These will not cause any interference in natural resources or services. Microbial biofuel cells utilize the living cell to produce bioelectricity via bioelectrochemical system. It can drive electricity or other energy generation currents via lived cell interaction. Microbial fuel cells (MFCs) and enzymatic biofuel cells with their advancement in design can improve sustainable bio-energy production by proving an efficient conversion system compared to chemical fuels into electric power. Different types of MFCs operation are reported in wastewater treatment with biogas biohydrogen and other biofuel/energy generation. Later biogas can convert into electric power. Hybrid microbial biofuel cell utility with photochemical reaction is found for electricity generation. Recent research and development in microbial biofuel design and its application will emphasize bioenergy for the future.

CeO2- ZrO2- and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE) for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51) at a gaseous space velocity of 70600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2 which showed the best performance in the stability test also produced the highest H2 yield above 600 °C followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM XPS and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm) and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.

A renewables-based energy transition promises to deliver vast socio-economic benefits to countries across Africa improving energy access creating jobs and boosting energy security. To realise these benefits African countries have an opportunity to leapfrog fossil fuel technologies to a more sustainable climate-friendly power strategy aligned with the Paris Agreement and low-carbon growth.<br/><br/>The Renewable Energy Transition in Africa jointly prepared by Germany's KfW Development Bank Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) and the International Renewable Energy Agency (IRENA) on behalf of the German Federal Ministry for Economic Cooperation and Development (BMZ) explores how African countries can achieve universal energy access within the 2030 Agenda timeframe and identifies four areas of action:<br/><br/>Promote access to energy;<br/>De-risk and promoting private sector investments;<br/>Strengthen and modernise the grid;<br/>Support systemic innovation.<br/>The study also explores the transformational potential of the electricity sector in five Africa countries: Ghana Ivory Coast Morocco Rwanda and South Africa. Specifically developed by IRENA country case studies show the real-life applicability of power sector transformation and demonstrates how countries can:<br/><br/>Take advantage of the abundancy and competitiveness of renewables;<br/>Align ambitious renewable targets in energy and climate plans;<br/>Continue supporting the development of regional markets;<br/>Leverage renewables and distributed energy resources to achieve universal energy access;<br/>Develop tailored power sector transformation plans based on a systemic innovation approach;<br/>Build on policy frameworks for just and inclusive transitions.

A research is under development at the Department of Agro-Environmental Sciences of the University of Bari “Aldo Moro” in order to investigate the suitable solutions of a power system based on solar energy (photovoltaic) and hydrogen integrated with a geothermal heat pump for powering a self sustained heated greenhouse. The electrical energy for heat pump operation is provided by a purpose-built array of solar photovoltaic modules which supplies also a water electrolyser system controlled by embedded pc; the generated dry hydrogen gas is conserved in suitable pressured storage tank. The hydrogen is used to produce electricity in a fuel cell in order to meet the above mentioned heat pump power demand when the photovoltaic system is inactive during winter night-time or the solar radiation level is insufficient to meet the electrical demand. The present work reports some theoretical and observed data about the electrolyzer operation. Indeed the electrolyzer has required particular attention because during the experimental tests it did not show a stable operation and it was registered a performance not properly consistent with the predicted performance by means of the theoretical study.

Power-to-fuel systems via solid-oxide electrolysis are promising for storing excess renewable electricity by efficient electrolysis of steam (or co-electrolysis of steam and CO₂) into hydrogen (or syngas) which can be further converted into synthetic fuels with plant-wise thermal integration. Electrolysis stack performance and durability determine the system design performance and long-term operating strategy; thus solid-oxide electrolyzer based power-to-fuels were investigated from the stack to system levels. At the stack level the data from a 6000-h stack testing under laboratory isothermal conditions were used to calibrate a quasi-2D model which enables to predict practical isothermal stack performance with reasonable accuracy. Feasible stack operating windows meeting various design specifications (e.g. specific syngas composition) were further generated to support the selection of operating points. At the system level with the chosen similar stack operating points various power-to-fuel systems including power-to-hydrogen power-to-methane power-to-methanol (dimethyl ether) and power-to-gasoline were compared techno-economically considering system-level heat integration. Several operating strategies of the stack were compared to address the increase in stack temperature due to degradation. The modeling results show that the system efficiency for producing H₂ methane methanol/dimethyl ether and gasoline decreases sequentially from 94% (power-to-H₂) to 64% (power-to-gasoline) based on a higher heating value. Co-electrolysis which allows better heat integration can improve the efficiency of the systems with less exothermic fuel-synthesis processes (e.g. methanol/dimethyl ether) but offers limited advantages for power-to-methane and power-to-gasoline systems. In a likely future scenario where the growing amount of electricity from renewable sources results in increasing periods of a negative electricity price solid oxide electrolyser based power-to-fuel systems are highly suitable for levelling the price fluctuations in an economic way.

In the present work the effect of artificial ageing of AA2024-T3 on the tensile mechanical properties and fracture toughness degradation due to corrosion exposure will be investigated. Tensile and fracture toughness specimens were artificially aged to tempers that correspond to Under-Ageing (UA) Peak-Ageing (PA) and Over-Ageing (OA) conditions and then were subsequently exposed to exfoliation corrosion environment. The corrosion exposure time was selected to be the least possible according to the experimental work of Alexopoulos et al. (2016) so as to avoid the formation of large surface pits trying to simulate the hydrogen embrittlement degradation only. The mechanical test results show that minimum corrosion-induced decrease in elongation at fracture was achieved for the peak-ageing condition while maximum was noticed at the under-ageing and over-ageing conditions. Yield stress decrease due to corrosion is less sensitive to tempering; fracture toughness decrease was sensitive to ageing heat treatment thus proving that the S΄ particles play a significant role on the corrosion-induced degradation.