Italy

In electrolyzers Faraday’s efficiency is a relevant parameter to assess the amount of hydrogen generated according to the input energy and energy efficiency. Faraday’s efficiency expresses the faradaic losses due to the gas crossover current. The thickness of the membrane and operating conditions (i.e. temperature gas pressure) may affect the Faraday’s efficiency. The developed models in the literature are mainly focused on alkaline electrolyzers and based on the current and temperature change. However the modeling of the effect of gas pressure on Faraday’s efficiency remains a major concern. In proton exchange membrane (PEM) electrolyzers the thickness of the used membranes is very thin enabling decreasing ohmic losses and the membrane to operate at high pressure because of its high mechanical resistance. Nowadays high-pressure hydrogen production is mandatory to make its storage easier and to avoid the use of an external compressor. However when increasing the hydrogen pressure the hydrogen crossover currents rise particularly at low current densities. Therefore faradaic losses due to the hydrogen crossover increase. In this article experiments are performed on a commercial PEM electrolyzer to investigate Faraday’s efficiency based on the current and hydrogen pressure change. The obtained results have allowed modeling the effects of Faraday’s efficiency by a simple empirical model valid for the studied PEM electrolyzer stack. The comparison between the experiments and the model shows very good accuracy in replicating Faraday’s efficiency.

Globally climate change fossil fuel depletion and greenhouse emissions are fundamental problems requiring massive effort from the international scientific community to be addressed and solved. Following the Clean Energy for all Europeans Package (CEP) guidelines the Italian Government has established challenging and tight objectives both on energy and climate matter to be targeted by 2030. Accordingly research activities on different topics are carried out in Italy looking at the installation of intermittent renewable energy systems (IRES) implementation of carbon capture and sequestration (CCS) on existing power plants and hydrogen technology and infrastructure penetration for accomplishing the end-users demands. The optimal integration of the above-mentioned technologies is one of the most effective weapons to address these objectives. The paper investigates different energy scenarios for meeting the Italian National Energy and Climate Plan (NECP) 2030 targets showing how the combined implementation of around +12 GW of IRES and +6 GW of electrolyzers compared to the national estimates simultaneously with the CCS of around 10 Mt of CO2 per year can reduce the CO2 emissions up to about 247 Mt/year. Thanks to the adoption of the well-established software platform EnergyPlan the integration of IRES plants CCS and hydrogen-based technologies have been explored and the most successful results for concurrently reducing the impact of industrial transport residential and energy sectors and mitigating the greenhouse emissions substantially relies on the diversifications. Results show both the technical and economic convenience of a 2030 energy scenario which implements properly hydrogen IRES and CCS penetration in the energy system meeting the NECP 2030 targets and maintaining both the over-generation of the power plants below 5 TWh and the initial capital expenditure to be sustained for this scenario to occur below +80% compared to the 2019 energy scenario.

The paper describes a numerical study of the combustion of hydrogen enriched methane and biogases containing hydrogen in a Controlled Auto Ignition engine (CAI). A single cylinder CAI engine is modelled with Chemkin to predict engine performance comparing the fuels in terms of indicated mean effective pressure engine efficiency and pollutant emissions. The effects of hydrogen and carbon dioxide on the combustion process are evaluated using the GRI-Mech 3.0 detailed radical chain reactions mechanism. A parametric study performed by varying the temperature at the start of compression and the equivalence ratio allows evaluating the temperature requirements for all fuels; moreover the effect of hydrogen enrichment on the auto-ignition process is investigated. The results show that at constant initial temperature hydrogen promotes the ignition which then occurs earlier as a consequence of higher chemical reactivity. At a fixed indicated mean effective pressure hydrogen presence shifts the operating range towards lower initial gas temperature and lower equivalence ratio and reduces NOx emissions. Such reduction somewhat counter-intuitive if compared with similar studies on spark-ignition engines is the result of operating the engine at lower initial gas temperatures.

The valorization of integrated steelworks process off-gases as feedstock for synthesizing methane and methanol is in line with European Green Deal challenges. However this target can be generally achieved only through process off-gases enrichment with hydrogen and use of cutting-edge syntheses reactors coupled to advanced control systems. These aspects are addressed in the RFCS project i3 upgrade and the central role of hydrogen was evident from the first stages of the project. First stationary scenario analyses showed that the required hydrogen amount is significant and existing renewable hydrogen production technologies are not ready to satisfy the demand in an economic perspective. The poor availability of low-cost green hydrogen as one of the main barriers for producing methane and methanol from process off-gases is further highlighted in the application of an ad-hoc developed dispatch controller for managing hydrogen intensified syntheses in integrated steelworks. The dispatch controller considers both economic and environmental impacts in the cost function and although significant environmental benefits are obtainable by exploiting process off-gases in the syntheses the current hydrogen costs highly affect the dispatch controller decisions. This underlines the need for big scale green hydrogen production processes and dedicated green markets for hydrogen-intensive industries which would ensure easy access to this fundamental gas paving the way for a C-lean and more sustainable steel production.

Ammonia has strong potentialities as sustainable fuel for energy applications. NH3 is carbon free and can be synthetized from renewable energy sources (RES). In Solid Oxide Fuel Cells NH3 reacts electrochemically thereby avoiding the production of typical combustion pollutants such as NOx. In this study an ammonia-fueled solid oxide fuel cells (SOFC) system design is proposed and a thermodynamic model is developed to evaluate its performance. A SOFC short stack was operated with NH3 in a wide range of conditions. Experimental results are implemented in the thermodynamic model. Electrical efficiency of 52.1% based on ammonia Lower Heating Value is calculated at a net power density of 0.36 W cmFC −2 . The operating conditions of the after burner and of the ammonia decomposition reactor are studied by varying the values of specific parameters. The levelized cost of energy of 0.221 $ kWh−1 was evaluated as introduced by the International Energy Agency for a system that operates at nominal conditions and at a reference power output of 100 kW. This supports the feasibility of ammonia-fueled SOFC systems with reference to the carbon free energy market specifically considering the potential development of green ammonia production.

This work investigates the environmental and economic performances of a membrane reactor for hydrogen production from raw biogas. Potential benefits of the innovative technology are compared against reference hydrogen production processes based on steam (or autothermal) reforming water gas shift reactors and a pressure swing adsorption unit. Both biogas produced by landfill and anaerobic digestion are considered to evaluate the impact of biogas composition. Starting from the thermodynamic results the environmental analysis is carried out using environmental Life cycle assessment (LCA). Results show that the adoption of the membrane reactor increases the system efficiency by more than 20 percentage points with respect to the reference cases. LCA analysis shows that the innovative BIONICO system performs better than reference systems when biogas becomes a limiting factor for hydrogen production to satisfy market demand as a higher biogas conversion efficiency can potentially substitute more hydrogen produced by fossil fuels (natural gas). However when biogas is not a limiting factor for hydrogen production the innovative system can perform either similar or worse than reference systems as in this case impacts are largely dominated by grid electric energy demand and component use rather than conversion efficiency. Focusing on the economic results hydrogen production cost shows lower value with respect to the reference cases (4 €/kgH2 vs 4.2 €/kgH2) at the same hydrogen delivery pressure of 20 bar. Between landfill and anaerobic digestion cases the latter has the lower costs as a consequence of the higher methane content.

Biomass gasification is a versatile thermochemical process that can be used for direct energy applications and the production of advanced liquid and gaseous energy carriers. In the present work the results are presented concerning the H2 production at a high purity grade from biomass feedstocks via steam/oxygen gasification. The data demonstrating such a process chain were collected at an innovative gasification prototype plant coupled to a portable purification system (PPS). The overall integration was designed for gas conditioning and purification to hydrogen. By using almond shells as the biomass feedstock from a product gas with an average and stable composition of 40%-v H2 21%-v CO 35%-v CO2 2.5%-v CH4 the PPS unit provided a hydrogen stream with a final concentration of 99.99%-v and a gas yield of 66.4%.

Within integrated steelmaking industries significant research efforts are devoted to the efficient use of resources and the reduction of CO2 emissions. Integrated steelworks consume a considerable quantity of raw materials and produce a high amount of by-products such as off-gases currently used for the internal production of heat steam or electricity. These off-gases can be further valorized as feedstock for methane and methanol syntheses but their hydrogen content is often inadequate to reach high conversions in synthesis processes. The addition of hydrogen is fundamental and a suitable hydrogen production process must be selected to obtain advantages in process economy and sustainability. This paper presents a comparative analysis of different hydrogen production processes from renewable energy namely polymer electrolyte membrane electrolysis solid oxide electrolyze cell electrolysis and biomass gasification. Aspen Plus® V11-based models were developed and simulations were conducted for sensitivity analyses to acquire useful information related to the process behavior. Advantages and disadvantages for each considered process were highlighted. In addition the integration of the analyzed hydrogen production methods with methane and methanol syntheses is analyzed through further Aspen Plus®-based simulations. The pros and cons of the different hydrogen production options coupled with methane and methanol syntheses included in steelmaking industries are analyzed

Micro-mobility plays an increasingly important role in the current energy transition thanks to its low energy consumption and reduced contribution to urban congestion. In this scenario fuel cell hybrid electric vehicles have several advantages over state-of-the-art battery electric vehicles such as increased driving ranges and reduced recharge times. In this paper we study the conversion of a commercial electric moped (Askoll eS3 ®) into a fuel cell hybrid electric vehicle by finding the optimal design of the components through an optimization methodology based on backward dynamic programming. This optimal design and operation strategy can also be implemented with a rulesbased approach. The results show that a system composed of a 1 kW proton exchange membrane fuel cell a 2000 Sl metal hydride hydrogen tank and a 240 Wh buffer battery can cover the same driving range as the batteries in an electric moped (119 km). Such a hybrid system occupies considerably less volume (almost 40 L) and has a negligibly higher mass. The free volume can be used to extend the driving range up to almost three times the nominal value. Moreover by using a high-pressure composite tank it is possible to increase the mass energy density of the onboard energy storage (although compression can require up to 10% of the hydrogen’s chemical energy). The fuel cell hybrid electric vehicle can be recharged with green hydrogen that is locally produced. In detail we analyze a residential scenario and a shared mobility scenario in the small Italian city of Viterbo.

This article aims to develop a proton exchange membrane (PEM) electrolyzer emulator. This emulator is realized through an equivalent electrical scheme. It allows taking into consideration the dynamic operation of PEM electrolyzers which is generally neglected in the literature. PEM electrolyzer dynamics are reproduced by the use of supercapacitors due to the high value of the equivalent double-layer capacitance value. Steady-state and dynamics operations are investigated in this work. The design criteria are addressed. The PEM electrolyzer emulator is validated by using a 400-W commercial PEM electrolyzer. This emulator is conceived to test new DC-DC converters to supply the PEM ELs and their control as well avoiding the risk to damage a real electrolyzer for experiment purposes. The proposed approach is valid both for a single cell and for the whole stack emulation.

Nowadays nearly one quarter of global carbon dioxide emissions are attributable to energy use in industry making this an important target for emission reductions. The scope of this study is hence that to define a cost-optimized decarbonization strategy for an energy and carbon intensive industry using an Italian refinery as a case study. The methodology involves the coupling of EnergyPLAN with a Multi-Objective Evolutionary Algorithm (MOEA) considering the minimization of annual cost and CO2 emissions as two potentially conflicting objectives and the energy technologies’ capacities as decision variables. For the target year 2025 EnergyPLAN+MOEA has allowed to model a range of 0-100 % decarbonization solutions characterized by optimal penetration mix of 22 technologies in the electrical thermal hydrogen feedstock and transport demand. A set of nine scenarios with different land use availabilities and implementable technologies each consisting of 100 optimal systems out of 10000 simulated ones has been evaluated. The results show on the one hand the possibility of achieving medium-high decarbonization solutions at costs close to current ones on the other how the decarbonization pathways strongly depend on the available land for solar thermal photovoltaic and wind as well as the presence of a biomass supply chain in the region.

This paper introduces the concept of a thermal management system (TMS) with integrated on-board power generation capabilities for a Mach 8 hypersonic aircraft powered by liquid hydrogen (LH2). This work developed within the EU-funded STRATOFLY Project aims to demonstrate an opportunity for facing the challenges of hypersonic flight for civil applications mainly dealing with thermal and environmental control as well as propellant distribution and on-board power generation adopting a highly integrated plant characterized by a multi-functional architecture. The TMS concept described in this paper makes benefit of the connection between the propellant storage and distribution subsystems of the aircraft to exploit hydrogen vapors and liquid flow as the means to drive a thermodynamic cycle able on one hand to ensure engine feed and thermal control of the cabin environment while providing on the other hand the necessary power for other on-board systems and utilities especially during the operation of high-speed propulsion plants which cannot host traditional generators. The system layout inspired by concepts studied within precursor EU-funded projects is detailed and modified in order to suggest an operable solution that can be installed on-board the reference aircraft with focus on those interfaces impacting its performance requirements and integration features as part of the overall systems architecture of the plane. Analysis and modeling of the system is performed and the main results in terms of performance along the reference mission profile are discussed.

Natural gas based hydrogen production with carbon capture and storage is referred to as blue hydrogen. If substantial amounts of CO2 from natural gas reforming are captured and permanently stored such hydrogen could be a low-carbon energy carrier. However recent research raises questions about the effective climate impacts of blue hydrogen from a life cycle perspective. Our analysis sheds light on the relevant issues and provides a balanced perspective on the impacts on climate change associated with blue hydrogen. We show that such impacts may indeed vary over large ranges and depend on only a few key parameters: the methane emission rate of the natural gas supply chain the CO2 removal rate at the hydrogen production plant and the global warming metric applied. State-of-the-art reforming with high CO2 capture rates combined with natural gas supply featuring low methane emissions does indeed allow for substantial reduction of greenhouse gas emissions compared to both conventional natural gas reforming and direct combustion of natural gas. Under such conditions blue hydrogen is compatible with low-carbon economies and exhibits climate change impacts at the upper end of the range of those caused by hydrogen production from renewable-based electricity. However neither current blue nor green hydrogen production pathways render fully “net-zero” hydrogen without additional CO2 removal.

Nowadays the traditional energy sources used for greenhouse heating are fossil fuels such as LPG diesel and natural gas. The global energy demand will continue to grow and alternative technologies need to be developed in order to improve the sustainability of crop production in protected environments. Innovative solutions are represented by renewable energy plants such as photovoltaic wind and geothermal integrated systems however these technologies need to be connected to the power grid in order to store the energy produced. On agricultural land power grids are not widespread and stand-alone renewable energy systems should be investigated especially for greenhouse applications. The aim of this research is to analyze by means of a mathematical model the energy efficiency of a photovoltaic (8.2 kW) hydrogen (2.5 kW) and ground source gas heat pump (2.2 kW) integrated in a stand-alone system used for heating an experimental greenhouse tunnel (48 m2 ) during the winter season. A yearlong energy performance analysis was conducted for three different types of greenhouse cover materials a single layer polyethylene film an air inflated-double layer polyethylene film and a double acrylic or polycarbonate. The results of one year showed that the integrated system had a total energy efficiency of 14.6%. Starting from the electric energy supplied by the photovoltaic array the total efficiency of the hydrogen and ground source gas heat pump system was 112% if the coefficient of the performance of the heat pump is equal to 5. The heating system increased the greenhouse air temperatures by 3–9 ◦C with respect to the external air temperatures depending on the greenhouse cover material used.

Methanol is currently considered one of the most useful chemical products and is a promising building block for obtaining more complex chemical compounds such as acetic acid methyl tertiary butyl ether dimethyl ether methylamine etc. Methanol is the simplest alcohol appearing as a colorless liquid and with a distinctive smell and can be produced by converting CO2 and H2 with the further benefit of significantly reducing CO2 emissions in the atmosphere. Indeed methanol synthesis currently represents the second largest source of hydrogen consumption after ammonia production. Furthermore a wide range of literature is focused on methanol utilization as a convenient energy carrier for hydrogen production via steam and autothermal reforming partial oxidation methanol decomposition or methanol–water electrolysis reactions. Last but not least methanol supply for direct methanol fuel cells is a well-established technology for power production. The aim of this work is to propose an overview on the commonly used feedstocks (natural gas CO2 or char/biomass) and methanol production processes (from BASF—Badische Anilin und Soda Fabrik to ICI—Imperial Chemical Industries process) as well as on membrane reactor technology utilization for generating high grade hydrogen from the catalytic conversion of methanol reviewing the most updated state of the art in this field.

Delivering low-carbon heat will require the substitution of natural gas with low-carbon alternatives such as electricity and hydrogen. The objective of this paper is to develop a method to soft-link two advanced investment-optimising energy system models RTN (Resource-Technology Network) and WeSIM (Whole-electricity System Investment Model) in order to assess cost-efficient heat decarbonisation pathways for the UK while utilising the respective strengths of the two models. The linking procedure included passing on hourly electricity prices from WeSIM as input to RTN and returning capacities and locations of hydrogen generation and shares of electricity and hydrogen in heat supply from RTN to WeSIM. The outputs demonstrate that soft-linking can improve the quality of the solution while providing useful insights into the cost-efficient pathways for zero-carbon heating. Quantitative results point to the cost-effectiveness of using a mix of electricity and hydrogen technologies for delivering zero-carbon heat also demonstrating a high level of interaction between electricity and hydrogen infrastructure in a zero-carbon system. Hydrogen from gas reforming with carbon capture and storage can play a significant role in the medium term while remaining a cost-efficient option for supplying peak heat demand in the longer term with the bulk of heat demand being supplied by electric heat pumps.

Among the numerous envisioned applications for hydrogen in the decarbonization of the energy system seasonal energy storage is usually regarded as one of the most likely options. Although long-term energy storage is usually considered at grid-scale level given the increasing diffusion of distributed energy systems and the expected cost reduction in hydrogen related components some companies are starting to offer residential systems with PV modules and batteries that rely on hydrogen for seasonal storage of electrical energy. Such hydrogen storage systems are generally composed by water electrolysers hydrogen storage vessels and fuel cells.<br/>The aim of this work is to investigate such systems and their possible applications for different geographical conditions in Italy. On-grid and off-grid systems are considered and compared to systems without hydrogen in terms of self-consumption ratio size of components and economic investment. Each different option has been assessed from a techno-economic point of view via MESS (Multi Energy Systems Simulator) an analytical programming tool for the analysis of local energy systems.<br/>Results have identified the optimal sizing of the system's components and have shown how such systems are not in general economically competitive for a single dwelling although they can in some cases ensure energy independence.

This paper presents two different scenarios for the energy system of the Netherlands that achieve the Dutch government’s national target of near net-zero greenhouse gas emissions in 2050. Using the system optimisation model OPERA the authors have analysed the technology sector and cost implications of the assumptions underlying these scenarios. While the roles of a number of key energy technology and emission mitigation options are strongly dependent on the scenario and cost assumptions the analysis yields several common elements that appear in both scenarios and that consistently appear under differing cost assumptions. For example one of the main options for the decarbonisation of the Dutch energy system is electrification of energy use in end-use sectors and for the production of renewable hydrogen with electrolysers. As a result the level of electricity generation in 2050 will be three to four times higher than present generation levels. Ultimately renewable energy – particularly from wind turbines and solar panels – is projected to account for the vast majority of electricity generation around 99% in 2050. Imbalances between supply and demand resulting from this variable renewable electricity production can be managed via flexibility options including demand response and energy storage. Hydrogen also becomes an important energy carrier notably for transportation and in industry. If import prices are lower than costs of domestic production from natural gas with CCS or through electrolysis from renewable electricity (2.4–2.7 €/kgH2) the use of hydrogen increases especially in the built environment.

New technological solutions are required to control the impact of the increasing presence of renewable energy sources connected to the electric grid that are characterized by unpredictable production (i.e. wind and solar energy). Energy storage is becoming essential to stabilize the grid when a mismatch between production and demand occurs. Among the available solutions Power to Hydrogen (P2H) is one of the most attractive options. However despite the potential many barriers currently hinder P2H market development. The literature reports general barriers and strategies to overcome them but a specific analysis is fundamental to identifying how these barriers concretely arise in national and regional frameworks since tailored solutions are needed to foster the development of P2H local market. The paper aims to identify and to analyze the existing barriers for P2H market uptake in Italy. The paper shows how several technical regulatory and economic issues are still unsolved resulting in a source of uncertainty for P2H investment. The paper also suggests possible approaches and solutions to address the Italian barriers and to support politics and decision-makers in the definition and implementation of the national hydrogen strategy.

A larger adoption of hydrogen fuel-cell electric vehicles (FCEVs) is typically included in the strategies to decarbonize the transportation sector. This inclusion is supported by life-cycle assessments (LCAs) which show the potential greenhouse gas (GHG) emission benefit of replacing internal combustion engine vehicles with their fuel cell counterpart. However the literature review performed in this study shows that the effects of durability and performance losses of fuel cells on the life-cycle environmental impact of the vehicle have rarely been assessed. Most of the LCAs assume a constant fuel consumption (ranging from 0.58 to 1.15 kgH2/100 km) for the vehicles throughout their service life which ranges in the assessments from 120000 to 225000 km. In this study the effect of performance losses on the life-cycle GHG emissions of the vehicles was assessed based on laboratory experiments. Losses have the effect of increasing the life-cycle GHG emissions of the vehicle up to 13%. Moreover this study attempted for the first time to investigate via laboratory analyses the GHG implications of replacing the hydrophobic polymer for the gas diffusion medium (GDM) of fuel cells to increase their durability. LCA showed that when the service life of the vehicle was fixed at 150000 km the GHG emission savings of using an FC with lower performance losses (i.e. FC coated with fluorinated ethylene propylene (FEP) instead of polytetrafluoroethylene (PTFE)) are negligible compared to the overall life-cycle impact of the vehicle. Both the GDM coating and the amount of hydrogen saved account for less than 2% of the GHG emissions arising during vehicle operation. On the other hand when the service life of the vehicle depends on the operability of the fuel cell the global warming potential per driven km of the FEP-based FCEV reduces by 7 to 32%. The range of results depends on several variables such as the GHG emissions from hydrogen production and the initial fuel consumption of the vehicle. Higher GHG savings are expected from an FC vehicle with high consumption of hydrogen produced with fossil fuels. Based on the results we recommend the inclusion of fuel-cell durability in future LCAs of FCEVs. We also advocate for more research on the real-life performance of fuel cells employing alternative materials.

The current greatest challenge that all gas turbine manufactures and users have in front of them for the years to come is the energy transition while reducing CO2 footprint and to contrast climate change. To this aim the introduction of hydrogen as fuel gas (or its blend) is playing a very important role. The benefit from an environmental point of view is undisputed but the presence of hydrogen introduces a series of safety related aspects to be considered for the design of all systems of a gas turbine package. Most of the design standards developed and adopted in the past are based on conventional natural gas however physical properties of hydrogen require to analyze additional aspects or revise the current ones. In this context the design for safety is paramount as it is strongly impacted by the low energy ignition of hydrogen blend fuels. Baker Hughes has built its experience on several sites different Customers and applications currently installed. These gas turbines run with a variety of hydrogen blends with concentration as high as 100% hydrogen. Baker Hughes has achieved several milestones moving from design to experimental set up leveraging the internal infrastructures consolidating design assumptions. In this work the critical aspects such as material selection instrumentation electrical devices and components are discussed in the framework of package safety with the aim to evolve conventional design minimizing the impacts on package configurations.

Lamination-like defects in pipeline steels can be of both metallurgical and operational origin. In pipelines transporting hydrocarbon usually such defects are not a big challenge since they do not propagate under operating conditions. Nonetheless in presence of a corrosion phenomenon and sour gas (H2S) it is possible to observe blisters and cracks which may propagate in the steel. The observed damage mechanisms is Hydrogen Embrittlement and in spite of a huge amount of study and publications available it is quite difficult for a pipeline owner to get practical data (crack propagation rate for instance) allowing a reliable estimate of the fitness for service of a pipeline. Taking advantage of a pipeline spool containing internal defects that was in service for more than 10 years and recently removed a comprehensive study is underway to obtain a complete assessment of the pipeline future integrity. The program is comprehensive of study and comparison of ILI reports of the pipeline to determine the optimum interval between inspections assessment of inspection results via an accurate nondestructive (UT) and destructive examination of the removed section to verify ILI results lab tests program on specimens from the removed spool at operating conditions (75-80 bar and 30°-36° C) in presence of a small quantity of water H2S (5%) and CO2 (7%) in order to assess defect propagation and to obtain an estimate of crack growth rate and test in field of available methods to monitor the presence of Hydrogen and/or the growth of defects in in-service pipelines. This quite ambitious program is also expected to be able of offering a small contribution toward a better understanding of HE mechanisms and the engineering application of such complex often mainly academic studies.

Decarbonization of energy economy is nowadays a topical theme and several pathways are under discussion. Gaseous fuels have a fundamental role for this transition and the production of low carbon-impact fuels is necessary to deal with this challenge. The generation of renewable hydrogen is a trusted solution since this energy vector can be promptly produced from electricity and injected into the existing natural gas infrastructure granting storage capacity and easy transportation. This scenario will lead in the near future to hydrogen enrichment of natural gas whose impact on the infrastructures is being actively studied. The effect on end-user devices such as domestic gas boilers instead is still little analyzed and tested but is fundamental to be assessed. The aim of this research is to generate knowledge on the effect of hydrogen enrichment on the widely used premixed boilers: the investigations include pollutant emissions efficiency flashback and explosion hazard control system and materials selection. A model for calculating several parameters related to combustion of hydrogen enriched natural gas is presented. Guidelines for the design of new components are provided and an insight is given on the maximum hydrogen blending bearable by the current boilers.

The framework for life cycle sustainability analysis (LCSA) developed within the project CALCAS (Co-ordination Action for innovation in Life-Cycle Analysis for Sustainability) is introducing a truly integrated approach for sustainability studies. However it needs to be further conceptually refined and to be made operational. In particular one of the gaps still hindering the adoption of integrated analytic tools for sustainability studies is the lack of a clear link between the goal and scope definition and the modeling phase. This paper presents an approach to structure the goal and scope phase of LCSA so as to identify the relevant mechanisms to be further detailed and analyzed in the modeling phase. The approach is illustrated with an on-going study on a new technology for the production of high purity hydrogen from biomass to be used in automotive fuel cells.

The main objective of the article is to provide a thorough review of currently used AC-DC converters for alkaline and proton exchange membrane (PEM) electrolyzers in power grid or wind energy conversion systems. Based on the current literature this article aims at emphasizing the advantages and drawbacks of AC-DC converters mainly based on thyristor rectifier bridges and chopper-rectifiers. The analysis is mainly focused on the current issues for these converters in terms of specific energy consumption current ripple reliability efficiency and power quality. From this analysis it is shown that thyristors-based rectifiers are particularly fit for high-power applications but require the use of active and passive filters to enhance the power quality. By comparison the association combination of the chopper-rectifier can avoid the use of bulky active and passive filters since it can improve power quality. However the use of a basic chopper (i.e. buck converter) presents several disadvantages from the reliability energy efficiency voltage ratio and current ripple point of view. For this reason new emerging DC-DC converters must be employed to meet these important issues according to the availability of new power switching devices. Finally based on the authors’ experience in power conversion for PEM electrolyzers a discussion is provided regarding the future challenges that must face power electronics for green hydrogen production based on renewable energy sources.