Italy

Explosion venting is a frequently used measure to mitigate the consequence of gas deflagrations in closed environments. Despite the effort to predict the vent area needed to achieved the protection through engineering formulas and CFD tools work has still to be done to reliably predict the outcome of a vented gas explosion. Most of available data derived from experimental campaigns performed in the past involved homogeneous conditions while especially in the case of a very buoyant gas such as hydrogen the most probable scenario that can follow and unintended release in a closed environment foresee the ignition of a stratified inhomogeneous mixture. University of Pisa performed experimental tests in a 25 m3 facility in homogeneous and inhomogeneous conditions. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated in the two scenarios. Description of the experimental set-up includes all the details deemed necessary to reproduce the phenomenon with a CFD tool.

This paper summarizes the current results of the theoretical and experimental activity carried out by the Italian Working Group on the fire prevention safety issues in the field of the hydrogen transport in pipelines. From the theoretical point of view a draft document has been produced beginning from the regulations in force on the natural gas pipelines; these have been reviewed corrected and integrated with the instructions suitable to the use of hydrogen. From the experimental point of view an apparatus has been designed and installed at the University of Pisa; this apparatus has allowed the simulation of hydrogen releases from a pipeline with and without ignition of hydrogen-air mixture. The experimental data have helped the completion of the above-mentioned draft document with the instructions about the safety distances. The document has been improved for example pipelines above ground (not buried) are allowed due to the knowledge acquired by means of the experimental campaign. The safety distances related to this kind of piping has been chosen on the base of risk analysis. The work on the text contents is concluded and the document is currently under discussion with the Italian stakeholders involved in the hydrogen applications.

The purpose of the experimental work is to determine the conditions for which an enclosure can guest a fuel cell for civil use. Concerning the installation permitting guide this study allows the safe use of the fuel cell in case of small not catastrophic leakages. In fact the correct plan of the vents in the enclosure guarantees the low concentration of hydrogen (H2) below the LFL.

In our society the use of hydrogen is continually growing and there will be a widespread installation of plants with high capacity storages in our towns as automotive refuelling stations. For this reason it is necessary to make accurate studies on the safety of these kinds of plants to protect our town inhabitants Moreover hydrogen is a highly flammable chemical that can be particularly dangerous in case of release since its mixing with air in the presence of an ignition source could lead to fires or explosions. Generally most simulation models whether or not concerned with fluid dynamics used in safety and risk studies are not validated for hydrogen use. This aspect may imply that the results of studies on safety cannot be too accurate and realistic. This paper introduces an experimental activity which was performed by the Department of Energetics of Politecnico of Torino with the collaboration of the University of Pisa. Accidental hydrogen release and dispersion were studied in order to acquire a set of experimental data to validate simulation models for such studies. At the laboratories of the Department of Mechanical Nuclear and Production Engineering of the University of Pisa a pilot plant called Hydrogen Pipe Break Test was built. The apparatus consisted of a 12 m3 tank which was fed by high pressure cylinders. A 50 m long pipe moved from the tank to an open space and at the far end of the pipe there was an automatic release system that could be operated by remote control. During the experimental activity data was acquired regarding hydrogen concentration as a function of distance from the release hole also lengthwise and vertically. In this paper some of the experimental data acquired during the activity have been compared with the integral models Effects and Phast. In the future experimental results will be used to calibrate a more sophisticated model to atmospheric dispersion studies.

This paper presents the current results of the theoretical and experimental activity carried out by the Italian Working Group on the fire prevention safety issues in the field of the hydrogen transport in pipelines. From the theoretical point of view a draft document has been produced beginning from the regulations in force on the natural gas pipelines; these have been reviewed corrected and integrated with the instructions suitable to the use with hydrogen gas. From the experimental point of view a suitable apparatus has been designed and installed at the University of Pisa; this apparatus will allow the simulation of hydrogen releases from a pipeline with or without ignition of the hydrogen-air mixture. The experimental data will help the completion of the above-mentioned draft document with the instructions about the safety distances. However in the opinion of the Group the work on the text contents is concluded and the document is ready to be discussed with the Italian stakeholders involved in the hydrogen applications.

The paper presents an overview of the main achievements of the internal project InsHyde of the HySafe NoE. The scope of InsHyde was to investigate realistic small-medium indoor hydrogen leaks and provide recommendations for the safe use/storage of indoor hydrogen systems. Additionally InsHyde served to integrate proposals from HySafe work packages and existing external research projects towards a common effort. Following a state of the art review InsHyde activities expanded into experimental and simulation work. Dispersion experiments were performed using hydrogen and helium at the INERIS gallery facility to evaluate short and long term dispersion patterns in garage like settings. A new facility (GARAGE) was built at CEA and dispersion experiments were performed there using helium to evaluate hydrogen dispersion under highly controlled conditions. In parallel combustion experiments were performed by FZK to evaluate the maximum amount of hydrogen that could be safely ignited indoors. The combustion experiments were extended later on by KI at their test site by considering the ignition of larger amounts of hydrogen in obstructed environments outdoors. An evaluation of the performance of commercial hydrogen detectors as well as inter-lab calibration work was jointly performed by JRC INERIS and BAM. Simulation work was as intensive as the experimental work with participation from most of the partners. It included pre-test simulations validation of the available CFD codes against previously performed experiments with significant CFD code inter-comparisons as well as CFD application to investigate specific realistic scenarios. Additionally an evaluation of permeation issues was performed by VOLVO CEA NCSRD and UU by combining theoretical computational and experimental approaches with the results being presented to key automotive regulations and standards groups. Finally the InsHyde project concluded with a public document providing initial guidance on the use of hydrogen in confined spaces.

In order to facilitate the introduction of a new technology as it is the utilization of hydrogen as an energy carrier development of safety codes and standards besides the conduction of demonstrative projects becomes a very important action to be realized. Useful tools of work could be the existing gaseous fuel codes (natural gas and propane) regulating the stationary and automotive applications. Some safety codes have been updated to include hydrogen but they have been based on criteria and/or data applicable for large industrial facilities making the realization of public hydrogen infrastructures prohibitive in terms of space. In order to solve the above mentioned problems others questions come out: how these safety distances have been defined? Which hazard events have been taken as reference for calculation? Is it possible to reduce the safety distances through an appropriate design of systems and components or through the predisposition of adequate mitigation measures? This paper presents an analysis of the definitions of “safety distances” and “hazardous locations” as well as a synoptic analysis of the different values in force in several States for hydrogen and natural gas. The above mentioned synoptic table will highlight the lacks and so some fields that need to be investigated in order to produce a suitable hydrogen standard.

In the last years different Italian hydrogen projects provided for gaseous hydrogen motor vehicles refuelling stations. Motivated by the lack of suitable set of rules in the year 2002 Italian National Firecorps (Institute under the Italian Ministry of the Interior) formed an Ad Hoc Working Group asked to regulate the above-said stations as regards fire prevention and protection safety. This Working Group consists of members coming from both Firecorps and academic world (Pisa University). Throughout his work this Group produced a technical rule covering the fire prevention requirements for design construction and operation of gaseous hydrogen refuelling stations. This document has been approved by the Ministry’s Technical Scientific Central Committee for fire prevention (C.C.T.S.) and now it has to carry out the “Community procedure for the provision of information”. This paper describes the main safety contents of the technical rule.

Duplex Stainless Steels (DSSs) are an attractive class of materials characterized by a strong corrosion resistance in many aggressive environments. Thanks to the high mechanical performances DSSs are widely used for many applications in petrochemical industry chemical and nuclear plants marine environment desalination etc.<br/>Among the DSSs critical aspects concerning the embrittlement process it is possible to remember the steel sensitization and the hydrogen embrittlement.<br/>The sensitization of the DSSs is due to the peculiar chemical composition of these grades which at high temperature are susceptible to carbide nitrides and second phases precipitation processes mainly at grains boundary and in the ferritic grains. The hydrogen embrittlement process is strongly influenced by the duplex (austenitic-ferritic) microstructure and by the loading conditions.<br/>In this work a rolled lean ferritic-austenitic DSS (2101) has been investigated in order to analyze the hydrogen embrittlement mechanisms by means of slow strain rate tensile tests considering the steel after different heat treatments. The damaging micromechanisms have been investigated by means of the scanning electron microscope observations on the fracture surfaces.

The target for European decarburization encourages the use of renewable energy sources and H₂ is considered the link in the global energy system transformation. So research studies are numerous but only few facilities can test materials and components for H₂ storage. This work offers a brief review of H₂ storage methods and presents the preliminary results obtained in a new facility. Slow strain rate and fatigue life tests were performed in H₂ at 80 MPa on specimens and a tank of AISI 4145 respectively. Besides the storage capacity at 30 MPa of a solid-state system they were evaluated on kg scale by adsorption test. The results have shown the H₂ influence on mechanical properties of the steel. The adsorption test showed a gain of 26% at 12 MPa in H₂ storage with respect to the empty condition. All samples have been characterized by complementary techniques in order to connect the H2 effect with material properties.

The need to significantly reduce emissions from the steelmaking sector requires effective and ready-to-use technical solutions. With this aim different decarbonization strategies have been investigated by both researchers and practitioners. To this concern the most promising pathway is represented by the replacement of natural gas with pure hydrogen in the direct reduced iron (DRI) production process to feed an electric arc furnace (EAF). This solution allows to significantly reduce direct emissions of carbon dioxide from the DRI process but requires a significant amount of electricity to power electrolyzers adopted to produce hydrogen. The adoption of renewable electricity sources (green hydrogen) would reduce emissions by 95–100% compared to the blast furnace–basic oxygen furnace (BF–BOF) route. In this work an analytical model for the identification of the minimum emission configuration of a green energy–steel system consisting of a secondary route supported by a DRI production process and a renewable energy conversion system is proposed. In the model both technological features of the hydrogen steel plant and renewable energy production potential of the site where it is to be located are considered. Compared to previous studies the novelty of this work consists of the joint modeling of a renewable energy system and a steel plant. This allows to optimize the overall system from an environmental point of view considering the availability of green hydrogen as an inherent part of the model. Numerical experiments proved the effectiveness of the model proposed in evaluating the suitability of using green hydrogen in the steelmaking process. Depending on the characteristics of the site and the renewable energy conversion system adopted decreases in emissions ranging from 60% to 91% compared to the BF–BOF route were observed for the green energy–steel system considered It was found that the environmental benefit of using hydrogen in the secondary route is strictly related to the national energy mix and to the electrolyzers’ technology. Depending on the reference context it was found that there exists a maximum value of the emission factor from the national electricity grid below which is environmentally convenient to produce DRI by using only hydrogen. It was moreover found that the lower the electricity consumption of the electrolyzer the higher the value assumed by the emission factor from the electricity grid which makes the use of hydrogen convenient.

A potentially viable solution to the problem of greenhouse gas emissions by vehicles in the transportation sector is the deployment of hydrogen as alternative fuel. A limitation to the diffusion of the hydrogen‐fuelled vehicles option is the intricate refuelling stations that vehicles will require. This study examines the practical use of hydrogen fuel within the internal combustion engine (ICE)‐powered long‐haul heavy‐duty trucking vehicles. Specifically it appraises the techno‐ economic feasibility of constructing a network of long‐haul truck refuelling stations using hydrogen fuel across Canada. Hydrogen fuel is chosen as an option for this study due to its low carbon emissions rate compared to diesel. This study also explores various operational methods including variable technology integration levels and truck traffic flows truck and pipeline delivery of hydrogen to stations and the possibility of producing hydrogen onsite. The proposed models created for this work suggest important parameters for economic development such as capital costs for station construction the selling price of fuel and the total investment cost for the infrastructure of a nation‐ wide refuelling station. Results showed that the selling price of hydrogen gas pipeline delivery op‐ tion is more economically stable. Specifically it was found that at 100% technology integration the range in selling prices was between 8.3 and 25.1 CAD$/kg. Alternatively at 10% technology integration the range was from 12.7 to 34.1 CAD$/kg. Moreover liquid hydrogen which is delivered by trucks generally had the highest selling price due to its very prohibitive storage costs. However truck‐delivered hydrogen stations provided the lowest total investment cost; the highest is shown by pipe‐delivered hydrogen and onsite hydrogen production processes using high technology integration methods. It is worth mentioning that once hydrogen technology is more developed and deployed the refuelling infrastructure cost is likely to decrease considerably. It is expected that the techno‐economic model developed in this work will be useful to design and optimize new and more efficient hydrogen refuelling stations for any ICE vehicles or fuel cell vehicles.

Hydrogen has the potential to act as the energy carrier of the future. It will be then produced in large amounts and will certainly need to be transported for long distances. The safest way to transport hydrogen is through pipelines. Failure of pipelines carrying gaseous hydrogen can have several effects some of which can pose a significant threat of damage to people and buildings in the immediate proximity of the failure location. This paper presents a probabilistic risk assessment procedure for the estimation of damage to people and buildings endangered by high-pressure hydrogen pipeline explosions. The procedure provides evaluation of annual probability of damage to people and buildings under an extreme event as a combination of the conditional probability of damage triggered by an explosion and the probability of occurrence of the explosion as a consequence of the pipeline failure. Physical features such as the gas jet release process flammable cloud size blast generation and explosion effects on people and buildings are considered and evaluated through the SLAB integral model TNO model Probit equations and Pressure-Impulse diagrams. For people both direct and indirect effects of overpressure events are considered. For buildings a comparison of the damage to different types of buildings (i.e. reinforced concrete buildings and tuff stone masonry buildings) is made. The probabilistic procedure presented may be used for designing a new hydrogen pipeline network and will be an advantageous tool for safety management of hydrogen gas pipelines.

In industrial buildings explosion relief panels or doors are often used to reduce damages caused by gas explosion. Decades of research produced a significant contribution to the understanding of the phenomena involved nevertheless among the aspects that need further research interaction between acoustic oscillation and the flame front is one of the more important. Interaction between the flame front and acoustic oscillation has raised technical problem in lots of combustion applications as well and had been studied theoretically and experimentally in such cases. Pressure oscillation had been observed in vented deflagration and in certain cases they are responsible for the highest pressure peak generated during the event. At Scalbatraio laboratory of Pisa University CVE test facility was built in order to investigate vented hydrogen deflagration. This paper is aimed to present an overview of the results obtained during several experimental campaigns which tests are analysed with the focus on the investigation of flame acoustic interaction phenomenon. Qualitative and quantitative analysis is presented and the possible physic generating the phenomenon investigated.

With the development of the natural gas industry gas transmission pipelines have been developed rapidly in terms of safety economy and efficiency. Our recent studies have shown that an important factor of main pipelines serviceability loss under their long-term service is the in-bulk metal degradation of the pipe wall. This leads to the loss of the initial mechanical properties primarily resistance to brittle fracture which were set in engineering calculations at the pipeline design stage. At the same time stress corrosion cracking has been identified as one of the predominant failures in pipeline steels in humid environments which causes rupture of high-pressure gas transmission pipes as well as serious economic losses and disasters.

In the present work the low-carbon pipeline steels with different strength levels from the point of view of their susceptibility to stress corrosion cracking in the as-received state and after in-laboratory accelerated degradation under environmental conditions similar to those of an acidic soil were investigated. The main objectives of this study were to determine whether the development of higher strength materials led to greater susceptibility to stress corrosion cracking and whether degraded pipeline steels became more susceptible to stress corrosion cracking than in the as-received state. The procedure of accelerated degradation of pipeline steels was developed and introduced in laboratory under the combined action of axial loading and hydrogen charging. It proved to be reliable and useful to performed laboratory simulation of in-service degradation of pipeline steels with different strength. The in-laboratory degraded 17H1S and X60 pipeline steels tested in the NS4 solution saturated with CO₂ under open circuit potential revealed the susceptibility to stress corrosion cracking reflected in the degradation of mechanical properties and at the same time the degraded X60 steel showed higher resistance to stress corrosion cracking than the degraded 17H1S steel. Fractographic observation confirmed the pipeline steels hydrogen embrittlement caused by the permeated hydrogen.

A large deployment of energy storage solutions will be required by the stochastic and non-controllable nature of most renewable energy sources when planning for higher penetration of renewable electricity into the energy mix. Various solutions have been suggested for dealing with medium- and long-term energy storage. Hydrogen and ammonia are two of the most frequently discussed as they are both carbon-free fuels. In this paper the authors analyse the energy and cost efficiency of hydrogen and ammonia-based pathways for the storage transportation and final use of excess electricity from an offshore wind farm. The problem is solved as a linear programming problem simultaneously optimising the size of each problem unit and the respective time-dependent operational conditions. As a case study we consider an offshore wind farm of 1.5 GW size located in a reference location North of Scotland. The energy efficiency and cost of the whole chain are evaluated and compared with competitive alternatives namely batteries and liquid hydrogen storage. The results show that hydrogen and ammonia storage can be part of the optimal solution. Moreover their use for long-term energy storage can provide a significant cost-effective contribution to an extensive penetration of renewable energy sources in national energy systems.

The diffusion of electric vehicles in Italy has started but some complications weight its spread. At present hybrid technology is the most followed by users due particularly to socioeconomic factors such as cost of investment and range anxiety. After a deep discussion of the Italian scenario the aim of the paper is to recognize whether fuel cell technology may be an enabling solution to overcome pollution problems and respect for the environment. The opportunity to use fuel cells to store electric energy is quite fascinating—the charging times will be shortened and heavy passenger transport should be effortless challenged. On the basis of the present history and by investigating the available information this work reports the current e-mobility state in Italy and forecasts the cities in which a fuel cell charging infrastructure should be more profitable with the intention of granting a measured outlook on the plausible development of this actual niche market.

Proposed sustainable transition pathways for moving away from natural gas in domestic heating focus on two main energy vectors: electricity and hydrogen. Electrification would be implemented by using vapourcompression heat pumps which are currently experiencing market growth in many countries. On the other hand hydrogen could substitute natural gas in boilers or be used in thermally–driven absorption heat pumps. In this paper a consistent thermodynamic and economic methodology is developed to assess the competitiveness of these options. The three technologies along with the option of district heating are for the first time compared for different weather/ambient conditions and fuel-price scenarios first from a homeowner’s and then from a wholeenergy system perspective. For the former two-dimensional decision maps are generated to identify the most cost-effective technologies for different combinations of fuel prices. It is shown that in the UK hydrogen technologies are economically favourable if hydrogen is supplied to domestic end-users at a price below half of the electricity price. Otherwise electrification and the use of conventional electric heat pumps will be preferred. From a whole-energy system perspective the total system cost per household (which accounts for upstream generation and storage as well as technology investment installation and maintenance) associated with electric heat pumps varies between 790 and 880 £/year for different scenarios making it the least-cost decarbonisation pathway. If hydrogen is produced by electrolysis the total system cost associated with hydrogen technologies is notably higher varying between 1410 and 1880 £/year. However this total system cost drops to 1150 £/year with hydrogen produced cost-effectively by methane reforming and carbon capture and storage thus reducing the gap between electricity- and hydrogen-driven technologies.

Chemical looping combustion (CLC) is a promising method for power production with integrated CO₂ capture with almost no direct energy penalty. When integrated into a natural gas combined cycle (NGCC) plant however CLC imposes a large indirect energy penalty because the maximum achievable reactor temperature is far below the firing temperature of state-of-the-art gas turbines. This study presents a techno-economic assessment of a CLC plant that circumvents this limitation via an added combustor after the CLC reactors. Without the added combustor the energy penalty amounts to 11.4%-points causing a high CO₂ avoidance cost of $117.3/ton which is more expensive than a conventional NGCC plant with post-combustion capture ($93.8/ton) with an energy penalty of 8.1%-points. This conventional CLC plant would also require a custom gas turbine. With an added combustor fired by natural gas a standard gas turbine can be deployed and CO2 avoidance costs are reduced to $60.3/ton mainly due to a reduction in the energy penalty to only 1.4%-points. However due to the added natural gas combustion after the CLC reactor CO₂ avoidance is only 52.4%. Achieving high CO₂ avoidance requires firing with clean hydrogen instead increasing the CO₂ avoidance cost to $96.3/ton when a hydrogen cost of $15.5/GJ is assumed. Advanced heat integration could reduce the CO₂ avoidance cost to $90.3/ton by lowering the energy penalty to only 0.6%-points. An attractive alternative is therefore to construct the plant for added firing with natural gas and retrofit the added combustor for hydrogen firing when CO₂ prices reach very high levels.

A 16Cr5NiMo supermartensitic stainless steel was subjected to different tempering treatments and analyzed by means of permeation tests and slow strain rate tests to investigate the effect of different amounts of retained austenite on its hydrogen embrittlement susceptibility. The 16Cr5NiMo steel class is characterized by a very low carbon content. It is the new variant of 13Cr4Ni. These steels are used in many applications for example compressors for sour environments offshore piping naval propellers aircraft components and subsea applications. The typical microstructure is a soft-tempered martensite very close to a body-centered cubic with a retained austenite fraction and limited δ ferrite phase. Supermartensitic stainless steels have high mechanical properties together with good weldability and corrosion resistance. The amount of retained austenite is useful to increase low temperature toughness and stress corrosion cracking resistance. Experimental techniques allowed us to evaluate diffusion coefficients and the mechanical behaviour of metals in stress corrosion cracking (SCC) conditions.

This work reports the integration of thin (~3e4 mm thick) Pd-based membranes for H2 separation in a fluidized bed catalytic reactor for ethanol auto-thermal reforming. The performance of a fluidized bed membrane reactor has been investigated from an experimental and numerical point of view. The demonstration of the technology has been carried out over 50 h under reactive conditions using 5 thin Pd-based alumina-supported membranes and a 3 wt%Pt-10 wt%Ni catalyst deposited on a mixed CeO2/SiO2 support. The results have confirmed the feasibility of the concept in particular the capacity to reach a hydrogen recovery factor up to 70% while the operation at different fluidization regimes oxygen-to-ethanol and steam-to-ethanol ratios feed pressures and reactor temperatures have been studied. The most critical part of the system is the sealing of the membranes where most of the gas leakage was detected. A fluidized bed membrane reactor model for ethanol reforming has been developed and validated with the obtained experimental results. The model has been subsequently used to design a small reactor unit for domestic use showing that 0.45 m2 membrane area is needed to produce the amount of H2 required for a 5 kWe PEM fuel-cell based micro-CHP system.

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.

Various Pt-based materials (unsupported Pt PtRu PtCo) were investigated as catalysts for recombining hydrogen and oxygen back into water. The recombination performance correlated well with the surface Pt metallic state. Alloying cobalt to platinum was observed to produce an electron transfer favouring the occurrence of a large fraction of the Pt metallic state on the catalyst surface. Unsupported PtCo showed both excellent recombination performance and dynamic behaviour. In a packed bed catalytic reactor when hydrogen was fed at 4% vol. in the oxygen stream (flammability limit) 99.5% of the total H2 content was immediately converted to water in the presence of PtCo thus avoiding safety issues. The PtCo catalyst was thus integrated in the anode of the membrane-electrode assembly of a polymer electrolyte membrane electrolysis cell. This catalyst showed good capability to reduce the concentration of hydrogen in the oxygen stream under differential pressure operation (1–20 bar) in the presence of a thin (90 μm) Aquivion® membrane. The modified system showed lower hydrogen concentration in the oxygen flow than electrolysis cells based on state-of-the-art thick polymer electrolyte membranes and allowed to expand the minimum current density load down to 0.15 A cm−2 . This was mainly due to the electrochemical oxidation of permeated H2 to protons that were transported back to the cathode. The electrolysis cell equipped with a dual layer PtCo/IrRuOx oxidation catalyst achieved a high operating current density (3 A cm−2 ) as requested to decrease the system capital costs under high efficiency conditions (about 77% efficiency at 55 °C and 20 bar). Moreover the electrolysis system showed reduced probability to reach the flammability limit under both high differential pressure (20 bar) and partial load operation (5%) as needed to properly address grid-balancing service

Currently Power-to-Gas technologies are considered viable solutions to face the onset problems associated with renewable capacity firming. Indeed carbon-free hydrogen production converting renewable electricity excess and its injection into natural gas pipelines is considered a short- to medium-term solution. In this way the so-called H2NG blends can be fired within internal combustion engines and micro gas turbines operating in CHP mode offering better environmental-energy performances in machines. As regards the distributed energy generation scenario the local H2 production by means of electrolysis for methane enrichment will be more cost-effective if the oxygen is fruitfully used instead of venting it out like a by-product as usually occurs. This study focuses on the usefulness of using that oxygen to enrich the air-fuel mixture of an internal combustion engine for micro-CHP applications once it has been fuelled with H2NG blends. Thus the main aim of this paper is to provide a set of values for benchmarking in which H2NG blends ranging in 0%-15% vol. burn within an ICE in partial oxy-fuel conditions. In particular a preliminary energy analysis was carried out based on experimental data reporting the engine operating parameters gains and losses in both electrical and heat recovery efficiency. The oxygen content in the air varies up to 22% vol. A Volkswagen Blue Tender CHP commercial version (19.8 kWel. of rated electrical power output) was considered as the reference machine and its energy characterization was reported when it operated under those unconventional conditions.

The way to decarbonization will be characterized by the huge production of hydrogen through sustainable routes. Thus the basic production way is water electrolysis sustained by renewable energy sources allowing for obtaining “green hydrogen”. The present paper reviews the main available technologies for the water electrolysis finalized to the hydrogen production. We describe the fundamental of water electrolysis and the problems related to purification and/or desalinization of water before electrolysis. As a matter of fact we describe the energy efficiency issues with particular attention to the potential application in the steel industry. The fundamental aspects related to the choice of high-temperature or low-temperature technologies are analyzed.