Italy
How Far Away is Hydrogen? Its Role in the Medium and Long-term Decarbonisation of the European Energy System
Nov 2015
Publication
Hydrogen is a promising avenue for decarbonising energy systems and providing flexibility. In this paper the JRC-EU-TIMES model – a bottom-up technology-rich model of the EU28 energy system – is used to assess the role of hydrogen in a future decarbonised Europe under two climate scenarios current policy initiative (CPI) and long-term decarbonisation (CAP). Our results indicate that hydrogen could become a viable option already in 2030 – however a long-term CO2 cap is needed to sustain the transition. In the CAP scenario the share of hydrogen in the final energy consumption of the transport and industry sectors reaches 5% and 6% by 2050. Low-carbon hydrogen production technologies dominate and electrolysers provide flexibility by absorbing electricity at times of high availability of intermittent sources. Hydrogen could also play a significant role in the industrial and transport sectors while the emergence of stationary hydrogen fuel cells for hydrogen-to-power would require significant cost improvements over and above those projected by the experts.
Achievements of European Projects on Membrane Reactor for Hydrogen Production
May 2017
Publication
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.
Micro and Macro Mechanical Analysis of Gas Pipeline Steels
Sep 2017
Publication
The actual safety margins of gas pipelines depend on a number of factors that include the mechanical characteristics of the material. The evolution with time of the metal properties can be evaluated by mechanical tests performed at different scales seeking for the best compromise between the simplicity of the experimental setup to be potentially employed in situ and the reliability of the results. Possible alternatives are comparatively assessed on pipeline steels of different compositions and in different states.
Expert Opinion Analysis on Renewable Hydrogen Storage Systems Potential in Europe
Nov 2016
Publication
Among the several typologies of storage technologies mainly on different physical principles (mechanical electrical and chemical) hydrogen produced by power to gas (P2G) from renewable energy sources complies with chemical storage principle and is based on the conversion of electrical energy into chemical energy by means of the electrolysis of water which does not produce any toxic or climate-relevant emission. This paper aims to pinpoint the potential uses of renewable hydrogen storage systems in Europe analysing current and potential locations regulatory framework governments’ outlooks economic issues and available renewable energy amounts. The expert opinion survey already used in many research articles on different topics including energy has been selected as an effective method to produce realistic results. The obtained results highlight strategies and actions to optimize the storage of hydrogen produced by renewables to face varying electricity demand and generation-driven fluctuations reducing the negative effects of the increasing share of renewables in the energy mix of European Countries.
Homogeneous Hydrogen Deflagrations in Small Scale Enclosure. Experimental Results
Sep 2017
Publication
University of Pisa performed experimental tests in a 1m3 facility which shape and dimensions resemble a gas cabinet for the HySEA project founded by the Fuel Cells and Hydrogen 2 Joint Undertaking with the aim to conduct pre-normative research on vented deflagrations in real-life enclosures and containers used for hydrogen energy applications in order to generate experimental data of high quality. The test facility named Small Scale Enclosure (SSE) had a vent area of 042m2 which location could be varied namely on the top or in front of the facility while different types of vent were investigated. Three different ignition location were investigated as well and the range of Hydrogen concentration ranged between 10 and 18% vol. This paper is aimed to summarize the main characteristics of the experimental campaign as well as to present its results.
A Techno-Economic Analysis of Solar Hydrogen Production by Electrolysis in the North of Chile and the Case of Exportation from Atacama Desert to Japan
Aug 2020
Publication
H2 production from solar electricity in the region of the Atacama Desert – Chile – has been identified as strategical for global hydrogen exportation. In this study the full supply chain of solar hydrogen has been investigated for 2018 and projected to scenarios for 2025-2030. Multi-year hourly electrical profiles data have been used from real operating PV plants and simulated Concentrated Solar Power “CSP” plants with Thermal Energy Storage “TES” as well as commercial electricity Power Purchase Agreement “PPA” prices reported in the Chilean electricity market were considered. The Levelized Cost of Hydrogen “LCOH” of each production pathway is calculated by a case-sensitive techno-economic MATLAB/Simulink model for utility scale (multi-MW) alkaline and PEM electrolyser technologies. Successively different distribution storage and transportation configurations are evaluated based on the 2025 Japanese case study according to the declared H2 demand. Transport in the form of liquefied hydrogen (LH2) and via ammonia (NH3) carrier is compared from the port of Antofagasta CL to the port of Osaka JP.
Hydrogen and Renewable Energy Sources Integrated System for Greenhouse Heating
Sep 2013
Publication
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.
Thermal Efficiency of On-site, Small-scale Hydrogen Production Technologies using Liquid Hydrocarbon Fuels in Comparison to Electrolysis a Case Study in Norway
Oct 2018
Publication
The main goal of this study was to assess the energy efficiency of a small-scale on-site hydrogen production and dispensing plant for transport applications. The selected location was the city of Narvik in northern Norway where the hydrogen demand is expected to be 100 kg/day. The investigated technologies for on-site hydrogen generation starting from common liquid fossil fuels such as heavy naphtha and diesel were based on steam reforming and partial oxidation. Water electrolysis derived by renewable energy was also included in the comparison. The overall thermal efficiency of the hydrogen station was computed including compression and miscellaneous power consumption.
Potential Models For Stand-Alone And Multi-Fuel Gaseous Hydrogen Refuelling Stations- Assessment Of Associated Risk
Sep 2005
Publication
Air pollution and traffic congestion are two of the major issues affecting public authorities policy makers and citizens not only in Italy and European Union but worldwide; this is nowadays witnessed by always more frequent limitations to the traffic in most of Italian cities for instance. Hydrogen use in automotive appears to offer a viable solution in medium-long term; this new perspective involves the need to carry out adequate infrastructures for distribution and refuelling and consequently the need to improve knowledge on hydrogen technologies from a safety point of view. In the present work possible different configurations for gaseous hydrogen refuelling station has been compared: “stand-alone” and “multi-fuel”. These two alternative scenarios has been taken into consideration each of one with specific hypotheses: “stand-alone” configuration based on the hypothesis of a potential model consisting of a hydrogen refuelling station composed by on-site hydrogen production via electrolysis a trailer of compressed gas for back-up compressor unit intermediate storage unit and dispenser. In this model it is assumed that no other refuelling equipment and/or dispenser of traditional fuel is present in the same site. “multi-fuel” configuration where it is assumed that the same components for hydrogen refuelling station are placed in the same site beside one or more refuelling equipment and/or dispenser of traditional fuel. Comparisons have been carried out from the point of view of specific risk assessment which have been conducted on both the two alternative scenarios.
Hydrogen Transport Safety: Case of Compressed Gaseous Tube Trailer
Sep 2005
Publication
The following paper describes researches to evaluate the behaviour under various accidental conditions of systems of transport compressed hydrogen. Particularly have been considered gaseous tube trailer and the packages cylinders employed for the road transport which have an internal gas pressures up to 200 barg.<br/>Further to a verification of the actual safety conditions this analysis intends to propose a theme that in the next future if confirmed projects around the employment of hydrogen as possible source energetic alternative could become quite important. The general increase of the consumptions of hydrogen and the consequently probable increase of the transports of gaseous hydrogen in pressure they will make the problem of the safety of the gaseous tube trail particularly important. Gaseous tube trailers will also use as components of plant. for versatility easy availability' and inexpensiveness.<br/>The first part of the memory is related to the analysis of the accidents happened in the last year in Italy with compressed hydrogen transports and particularly an accurate study has been made on the behaviour of a gaseous tube trailer involved in fire following a motorway accident in March 2003. In the central part of the job has been done a safety analysis of the described events trying to make to also emerge the most critical elements towards the activities developed by the teams of help intervened.<br/>Finally in the last part you are been listed on the base of the picked data a series of proposals and indications of the possible structural and procedural changes that could be suggested with the purpose to guarantee more elevated safety levels.
Guidelines for Fire Corps Standard Operating Procedures in the Event of Hydrogen Releases
Sep 2007
Publication
This paper presents a study on the Standard Operating Procedures (P.O.S.s) for the operation of the Fire Corps squads in the event of accidents with a hydrogen release fire or explosion. This study has been carried out by the Italian Working Group on the fire prevention safety issues as one of its main objectives. The Standard Operating Procedures proved to be a basic tool in order to improve the effectiveness of the Fire Corps rescue activity. The unique physical and chemical properties of the hydrogen its use without odorization and its almost invisible flame require a review of the already codified approaches to the rescue operations where conventional gases are involved. However this is only the first step; a Standard Operating Procedure puts together both the theoretical and practical experience achieved on the management of the rescue operations; therefore its arrangement is a cyclic process by nature always under continuous revision updating and improvement.
Fire Prevention Technical Rule for Gaseous Hydrogen Refuelling Stations
Sep 2005
Publication
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.
Hydrogen–methane Mixtures: Dispersion and Stratification Studies
Sep 2011
Publication
The study of hydrogen as an alternative fuel clean and “environment friendly” has been in the last years and continues to be object of many studies international projects and standard development. Hydrogen is a fundamental energy carrier to be developed together with other renewable resources for the transition to a sustainable energy system.<br/>But experience has shown how often the introduction and establishment of a new technology does not necessarily pass through radical changes but can be stimulated by slight modifications to the “present situation”.<br/>So the worldwide experience with natural gas as industrial automotive and domestic fuel has been the incentive to the present interest towards hydrogen–methane mixtures. The possible use of existing pipeline networks for mixtures of natural gas and hydrogen offers a unique and cost-effective opportunity to initiate the progressive introduction of hydrogen as part of the development of a full hydrogen system.<br/>The aim of the work presented in this paper is the investigation of the dispersion and stratification properties of hydrogen and methane mixtures. Experimental activities have been carried out in a large scale closed apparatus characterized by a volume of about 25 m3 both with and without natural ventilation. Mixtures of 10%vol. hydrogen – 90%vol. methane and 30%vol. hydrogen – 70%vol. methane have been studied with the help of oxygen sensors and gas chromatography.
Life Cycle Environmental Analysis of a Hydrogen-based Energy Storage System for Remote Applications
Mar 2022
Publication
Energy storage systems are required to address the fluctuating behaviour of variable renewable energy sources. The environmental sustainability of energy storage technologies should be carefully assessed together with their techno-economic feasibility. In this work an environmental analysis of a renewable hydrogen-based energy storage system has been performed making use of input parameters made available in the framework of the European REMOTE project. The analysis is applied to the case study of the Froan islands (Norway) which are representative of many other insular microgrid sites in northern Europe. The REMOTE solution is compared with other scenarios based on fossil fuels and submarine connections to the mainland grid. The highest climate impacts are found in the dieselbased configuration (1090.9 kgCO2eq/MWh) followed by the REMOTE system (148.2 kgCO2eq/MWh) and by the sea cable scenario (113.7 kgCO2eq/MWh). However the latter is biased by the very low carbon intensity of the Norwegian electricity. A sensitivity analysis is then performed on the length of the sea cable and on the CO2 emission intensity of electricity showing that local conditions have a strong impact on the results. The REMOTE system is also found to be the most cost-effective solution to provide electricity to the insular community. The in-depth and comparative (with reference to possible alternatives) assessment of the renewable hydrogen-based system aims to provide a comprehensive overview about the effectiveness and sustainability of these innovative solutions as a support for off-grid remote areas.
Quantification of the Uncertainty of the Peak Pressure Value in the Vented Deflagrations of Air-Hydrogen Mixtures
Sep 2007
Publication
In the problem of the protection by the consequences of an explosion is actual for many industrial application involving storage of gas like methane or hydrogen refuelling stations and so on. A simple and economic way to reduce the peak pressure associated to a deflagration is to supply to the confined environment an opportune surface substantially less resistant then the protected structure typically in stoichiometric conditions the peak pressure reduction is around the 8 bars for a generic hydrocarbon combustion in an adiabatic system lacking of whichever mitigation system. In general the problem is the forecast of the peak pressure value (PMAX) of the explosion. This problem is faced using CFD codes modelling the structure in which the explosion is located and setting the main parameters like concentration of the gas in the mixture the volume available the size of vent area and obstacles (if included) and so on. In this work the idea is to start from empirical data to train a Neural Network (NN) in order to find the correlation among the parameters regulating the phenomenon. Associated to this prediction a fuzzy model will provide to quantify the uncertainty of the predicted value.
Experimental Characterization and Energy Performance Assessment of a Sorption-Enhanced Steam–Methane Reforming System
Aug 2021
Publication
The production of blue hydrogen through sorption-enhanced processes has emerged as a suitable option to reduce greenhouse gas emissions. Sorption-enhanced steam–methane reforming (SESMR) is a process intensification of highly endothermic steam–methane reforming (SMR) ensured by in situ carbon capture through a solid sorbent making hydrogen production efficient and more environmentally sustainable. In this study a comprehensive energy model of SESMR was developed to carry out a detailed energy characterization of the process with the aim of filling a current knowledge gap in the literature. The model was applied to a bench-scale multicycle SESMR/sorbent regeneration test to provide an energy insight into the process. Besides the experimental advantages of higher hydrogen concentration (90 mol% dry basis 70 mol% wet basis) and performance of CO2 capture the developed energy model demonstrated that SESMR allows for substantially complete energy self-sufficiency through the process. In comparison to SMR with the same process conditions (650 ◦C 1 atm) performed in the same experimental rig SESMR improved the energy efficiency by about 10% further reducing energy needs.
Experimental and Theoretical Insights to Demonstrate the Hydrogen Evolution Activity of Layered Platinum Dichalcogenides Electrocatalysts
Mar 2021
Publication
Hydrogen is a highly efficient and clean renewable energy source and water splitting through electrocatalytic hydrogen evolution is a most promising approach for hydrogen generation. Layered transition metal dichalcogenides-based nano-structures have recently attracted significant interest as robust and durable catalysts for hydrogen evolution. We systematically investigated the platinum (Pt) based dichalcogenides (PtS2 PtSe2 and PtTe2) as highly energetic and robust hydrogen evolution electrocatalysts. PtTe2 catalyst unveiled the rapid hydrogen evolution process with the low overpotentials of 75 and 92 mV (vs. RHE) at a current density of 10 mA cm−2 and the small Tafel slopes of 64 and 59 mV/dec in acidic and alkaline medium respectively. The fabricated PtTe2 electrocatalyst explored a better catalytic activity than PtS2 and PtSe2. The density functional theory estimations explored that the observed small Gibbs free energy for H-adsorption of PtTe2 was given the prominent role to achieve the superior electrocatalytic and excellent stability activity towards hydrogen evolution due to a smaller bandgap and the metallic nature. We believe that this work will offer a key path to use Pt based dichalcogenides for hydrogen evolution electrocatalysts.
Goal and Scope in Life Cycle Sustainability Analysis: The Case of Hydrogen Production from Biomass
Aug 2014
Publication
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.
Delivering Net-zero Carbon Heat: Technoeconomic and Whole-system Comparisons of Domestic Electricity- and Hydrogen-driven Technologies in the UK
Apr 2022
Publication
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.
A Statistical Assessment of Blending Hydrogen into Gas Networks
Aug 2021
Publication
The deployment of low-carbon hydrogen in gas grids comes with strategic benefits in terms of energy system integration and decarbonization. However hydrogen thermophysical properties substantially differ from natural gas and pose concerns of technical and regulatory nature. The present study investigates the blending of hydrogen into distribution gas networks focusing on the steady-state fluid dynamic response of the grids and gas quality compliance issues at increasing hydrogen admixture levels. Two blending strategies are analyzed the first of which involves the supply of NG–H2 blends at the city gate while the latter addresses the injection of pure hydrogen in internal grid locations. In contrast with traditional case-specific analyses results are derived from simulations executed over a large number (i.e. one thousand) of synthetic models of gas networks. The responses of the grids are therefore analyzed in a statistical fashion. The results highlight that lower probabilities of violating fluid dynamic and quality restrictions are obtained when hydrogen injection occurs close to or in correspondence with the system city gate. When pure hydrogen is injected in internal grid locations even very low volumes (1% vol of the total) may determine gas quality violations while fluid dynamic issues arise only in rare cases of significant hydrogen injection volumes (30% vol of the total).
Stress Corrosion Cracking of Gas Pipeline Steels of Different Strength
Jul 2016
Publication
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.
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.
Electrified Hydrogen Production from Methane for PEM Fuel Cells Feeding: A Review
May 2022
Publication
The greatest challenge of our times is to identify low cost and environmentally friendly alternative energy sources to fossil fuels. From this point of view the decarbonization of industrial chemical processes is fundamental and the use of hydrogen as an energy vector usable by fuel cells is strategic. It is possible to tackle the decarbonization of industrial chemical processes with the electrification of systems. The purpose of this review is to provide an overview of the latest research on the electrification of endothermic industrial chemical processes aimed at the production of H2 from methane and its use for energy production through proton exchange membrane fuel cells (PEMFC). In particular two main electrification methods are examined microwave heating (MW) and resistive heating (Joule) aimed at transferring heat directly on the surface of the catalyst. For cases the catalyst formulation and reactor configuration were analyzed and compared. The key aspects of the use of H2 through PEM were also analyzed highlighting the most used catalysts and their performance. With the information contained in this review we want to give scientists and researchers the opportunity to compare both in terms of reactor and energy efficiency the different solutions proposed for the electrification of chemical processes available in the recent literature. In particular through this review it is possible to identify the solutions that allow a possible scale-up of the electrified chemical process imagining a distributed production of hydrogen and its consequent use with PEMs. As for PEMs in the review it is possible to find interesting alternative solutions to platinum with the PGM (Platinum Group Metal) free-based catalysts proposing the use of Fe or Co for PEM application.
A Preliminary Energy Analysis of a Commercial CHP Fueled with H2NG Blends Chemically Supercharged by Renewable Hydrogen and Oxygen
Dec 2016
Publication
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.
Control of Electrons’ Spin Eliminates Hydrogen Peroxide Formation During Water Splitting
Jul 2017
Publication
The production of hydrogen through water splitting in a photoelectrochemical cell suffers from an overpotential that limits the efficiencies. In addition hydrogen-peroxide formation is identified as a competing process affecting the oxidative stability of photoelectrodes. We impose spin-selectivity by coating the anode with chiral organic semiconductors from helically aggregated dyes as sensitizers; Zn-porphyrins and triarylamines. Hydrogen peroxide formation is dramatically suppressed while the overall current through the cell correlating with the water splitting process is enhanced. Evidence for a strong spin-selection in the chiral semiconductors is presented by magnetic conducting (mc-)AFM measurements in which chiral and achiral Zn-porphyrins are compared. These findings contribute to our understanding of the underlying mechanism of spin selectivity in multiple electron-transfer reactions and pave the way toward better chiral dye-sensitized photoelectrochemical cells.
Timmermans’ Dream: An Electricity and Hydrogen Partnership Between Europe and North Africa
Oct 2021
Publication
Because of differences in irradiation levels it could be more efficient to produce solar electricity and hydrogen in North Africa and import these energy carriers to Europe rather than generating them at higher costs domestically in Europe. From a global climate change mitigation point of view exploiting such efficiencies can be profitable since they reduce overall renewable electricity capacity requirements. Yet the construction of this capacity in North Africa would imply costs associated with the infrastructure needed to transport electricity and hydrogen. The ensuing geopolitical dependencies may also raise energy security concerns. With the integrated assessment model TIAM-ECN we quantify the trade-off between costs and benefits emanating from establishing import-export links between Europe and North Africa for electricity and hydrogen. We show that for Europe a net price may have to be paid for exploiting such interlinkages even while they reduce the domestic investments for renewable electricity capacity needed to implement the EU’s Green Deal. For North African countries the potential net benefits thanks to trade revenues may build up to 50 billion €/yr in 2050. Despite fears over costs and security Europe should seriously consider an energy partnership with North Africa because trade revenues are likely to lead to positive employment income and stability effects in North Africa. Europe can indirectly benefit from such impacts.
Process Integration of Green Hydrogen: Decarbonization of Chemical Industries
Sep 2020
Publication
Integrated water electrolysis is a core principle of new process configurations for decarbonized heavy industries. Water electrolysis generates H2 and O2 and involves an exchange of thermal energy. In this manuscript we investigate specific traditional heavy industrial processes that have previously been performed in nitrogen-rich air environments. We show that the individual process streams may be holistically integrated to establish new decarbonized industrial processes. In new process configurations CO2 capture is facilitated by avoiding inert gases in reactant streams. The primary energy required to drive electrolysis may be obtained from emerging renewable power sources (wind solar etc.) which have enjoyed substantial industrial development and cost reductions over the last decade. The new industrial designs uniquely harmonize the intermittency of renewable energy allowing chemical energy storage. We show that fully integrated electrolysis promotes the viability of decarbonized industrial processes. Specifically new process designs uniquely exploit intermittent renewable energy for CO2 conversion enabling thermal integration H2 and O2 utilization and sub-process harmonization for economic feasibility. The new designs are increasingly viable for decarbonizing ferric iron reduction municipal waste incineration biomass gasification fermentation pulp production biogas upgrading and calcination and are an essential step forward in reducing anthropogenic CO2 emissions.
Comparative Life Cycle Assessment of Hydrogen-fuelled Passenger Cars
Feb 2021
Publication
In order to achieve gradual but timely decarbonisation of the transport sector it is essential to evaluate which types of vehicles provide a suitable environmental performance while allowing the use of hydrogen as a fuel. This work compares the environmental life-cycle performance of three different passenger cars fuelled by hydrogen: a fuel cell electric vehicle an internal combustion engine car and a hybrid electric vehicle. Besides two vehicles that use hydrogen in a mixture with natural gas or gasoline were considered. In all cases hydrogen produced by wind power electrolysis was assumed. The resultant life-cycle profiles were benchmarked against those of a compressed natural gas car and a hybrid electric vehicle fed with natural gas. Vehicle infrastructure was identified as the main source of environmental burdens. Nevertheless the three pure hydrogen vehicles were all found to be excellent decarbonisation solutions whereas vehicles that use hydrogen mixed with natural gas or gasoline represent good opportunities to encourage the use of hydrogen in the short term while reducing emissions compared to ordinary vehicles.
Life Cycle Assessment of Substitute Natural Gas Production from Biomass and Electrolytic Hydrogen
Feb 2021
Publication
The synthesis of a Substitute Natural Gas (SNG) that is compatible with the gas grid composition requirements by using surplus electricity from renewable energy sources looks a favourable solution to store large quantities of electricity and to decarbonise the gas grid network while maintaining the same infrastructure. The most promising layouts for SNG production and the conditions under which SNG synthesis reduces the environmental impacts if compared to its fossil alternative is still largely untapped. In this work six different layouts for the production of SNG and electricity from biomass and fluctuating electricity are compared from the environmental point of view by means of Life Cycle Assessment (LCA) methodology. Global Warming Potential (GWP) Cumulative Energy Demand (CED) and Acidification Potential (AP) are selected as impact indicators for this analysis. The influence of key LCA methodological aspects on the conclusions is also explored. In particular two different functional units are chosen: 1 kg of SNG produced and 1 MJ of output energy (SNG and electricity). Furthermore different approaches dealing with co-production of electricity are also applied. The results show that the layout based on hydrogasification has the lowest impacts on all the considered cases apart from the GWP and the CED with SNG mass as the functional unit and the avoided burden approach. Finally the selection of the multifunctionality approach is found to have a significant influence on technology ranking.
Direct Route from Ethanol to Pure Hydrogen through Autothermal Reforming in a Membrane Reactor: Experimental Demonstration, Reactor Modelling and Design
Nov 2020
Publication
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.
Impact Assessments on People and Buildings for Hydrogen Pipeline Explosions
Sep 2019
Publication
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.
Techno-economic Analysis of In-situ Production by Electrolysis, Biomass Gasification and Delivery Systems for Hydrogen Refuelling Stations: Rome Case Study
Oct 2018
Publication
Starting from the Rome Hydrogen Refuelling Station demand of 65 kg/day techno-economics of production systems and balance of plant for small scale stations have been analysed. A sensitivity analysis has been done on Levelised Cost of Hydrogen (LCOH) in the range of 0 to 400 kg/day varying capacity factor and availability hours or travel distance for alkaline electrolysers biomass gasification and hydrogen delivery. As expected minimum LCOH for electrolyser and gasifier is found at 400 kg/day and 24 h/day equal to 12.71 €/kg and 5.99 €/kg however for operating hours over 12 and 10 h/day the differential cost reaches a plateau (below 5%) for electrolyser and gasifier respectively. For the Rome station design 160 kWe of electrolysers 24 h/day and 100 kWth gasifier at 8 h/day LCOH (11.85 €/kg) was calculated considering the modification of the cost structure due to the existing equipment which is convenient respect the use of a single technology except for 24 h/day gasification.
Integration of Gas Switching Combustion and Membrane Reactors for Exceeding 50% Efficiency in Flexible IGCC Plants with Near-zero CO2 Emissions
Jul 2020
Publication
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.
Integration of Chemical Looping Combustion for Cost-effective CO2 Capture from State-of-the-art Natural Gas Combined Cycles
May 2020
Publication
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.
Hydrogen Production as a Clean Energy Carrier through Heterojunction Semiconductors for Environmental Remediation
Apr 2022
Publication
Today as a result of the advancement of technology and increasing environmental problems the need for clean energy has considerably increased. In this regard hydrogen which is a clean and sustainable energy carrier with high energy density is among the well-regarded and effective means to deliver and store energy and can also be used for environmental remediation purposes. Renewable hydrogen energy carriers can successfully substitute fossil fuels and decrease carbon dioxide (CO2 ) emissions and reduce the rate of global warming. Hydrogen generation from sustainable solar energy and water sources is an environmentally friendly resolution for growing global energy demands. Among various solar hydrogen production routes semiconductor-based photocatalysis seems a promising scheme that is mainly performed using two kinds of homogeneous and heterogeneous methods of which the latter is more advantageous. During semiconductor-based heterogeneous photocatalysis a solid material is stimulated by exposure to light and generates an electron–hole pair that subsequently takes part in redox reactions leading to hydrogen production. This review paper tries to thoroughly introduce and discuss various semiconductor-based photocatalysis processes for environmental remediation with a specific focus on heterojunction semiconductors with the hope that it will pave the way for new designs with higher performance to protect the environment.
Detection, Characterization and Sizing of Hydrogen Induced Cracking in Pressure Vessels Using Phased Array Ultrasonic Data Processing
Jul 2016
Publication
Pressure vessels operating in sour service conditions in refinery environments can be subject to the risk of H₂S cracking resulting from the hydrogen entering into the material. This risk which is related to the specific working conditions and to the quality of the steel used shall be properly managed in order to maintain the highest safety at a cost-effective level.<br/>Nowadays the typical management strategy is based on a risk based inspection (RBI) evaluation to define the inspection plan used in conjunction with a fitness for service (FFS) approach in defining if the vessel although presenting dangerous defects such as cracks can still be considered “fit for purpose” for a given time window based on specific fracture mechanics analysis.<br/>These vessels are periodically subject to non-destructive evaluation typically ultrasonic testing. Phased Array (PA) ultrasonic is the latest technology more and more used for this type of application.<br/>This paper presents the design and development of an optimized Phased Array ultrasonic inspection technique for the detection and sizing of hydrogen induced cracking (HIC) type flaws used as reference for comparison. Materials used containing natural operational defects were inspected in “as-service” conditions.<br/>Samples have then been inspected by means of a “full matrix capture” (FMC) acquisition process followed by “total focusing method” (TFM) data post processing. FCM-TFM data have been further post-processed and then used to create a 3D geometrical reconstruction of the volume inspected. Results obtained show the significant improvement that FMC/TFM has over traditional PA inspection techniques both in terms of sensitivity and resolution for this specific type of defect. Moreover since the FMC allows for the complete time domain signal to be captured from every element of a linear array probe the full set of data is available for post-processing.<br/>Finally the possibility to reconstruct the geometry of the component from the scans including the defects present in its volume represents the ideal solution for a reliable data transferring process to the engineering function for the subsequent FFS analysis.
Analysis of Acoustic Pressure Oscillation During Vented Deflagration
Oct 2015
Publication
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.
Helios- A New Method for Hydrogen Permeation Test
Sep 2013
Publication
Hydrogen induced cracking is still a severe and current threat for several industrial applications. With the aim of providing a simple and versatile device for hydrogen detection a new instrument was designed based on solid state sensor technology. New detection technique allows to execute hydrogen permeation measurement in short time and without material surface preparation. Thanks to this innovation HELIOS offers a concrete alternative to traditional experimental methods for laboratory permeability tests. In addition it is proposed as a new system for Non Destructive Testing of components in service in hydrogenating environment. Hydrogen flux monitoring is particularly relevant for risk mitigation of elements involved in hydrogen storage and transportation. Hydrogen permeation tests were performed by means of HELIOS instruments both on a plane membrane and on the wall of a gas cylinder. Results confirmed the extreme sensitivity of the detection system and its suitability to perform measurements even on non metallic materials by means of an easy-to-handle instrument.
Hydrogen Embrittlement Behavior of 18Ni 300 Maraging Steel Produced by Selective Laser Melting
Jul 2019
Publication
A study was performed to investigate the hydrogen embrittlement behavior of 18-Ni 300 maraging steel produced by selective laser melting and subjected to different heat treatment strategies. Hydrogen was pre-charged into the tensile samples by an electro-chemical method at the constant current density of 1 A m−2 and 50 A m−2 for 48 h at room temperature. Charged and uncharged specimens were subjected to tensile tests and the hydrogen concentration was eventually analysed using quadrupole mass spectroscopy. After tensile tests uncharged maraging samples showed fracture surfaces with dimples. Conversely in H-charged alloys quasi-cleavage mode fractures occurred. A lower concentration of trapped hydrogen atoms and higher elongation at fracture were measured in the H-charged samples that were subjected to solution treatment prior to hydrogen charging compared to the as-built counterparts. Isothermal aging treatment performed at 460 °C for 8 h before hydrogen charging increased the concentration of trapped hydrogen giving rise to higher hydrogen embrittlement susceptibility.
Optimal Operations for Hydrogen-based Energy Storage Systems in Wind Farms via Model Predictive Control
Feb 2021
Publication
Efficient energy production and consumption are fundamental points for reducing carbon emissions that influence climate change. Alternative resources such as renewable energy sources (RESs) used in electricity grids could reduce the environmental impact. Since RESs are inherently unreliable during the last decades the scientific community addressed research efforts to their integration with the main grid by means of properly designed energy storage systems (ESSs). In order to highlight the best performance from these hybrid systems proper design and operations are essential. The purpose of this paper is to present a so-called model predictive controller (MPC) for the optimal operations of grid-connected wind farms with hydrogen-based ESSs and local loads. Such MPC has been designed to take into account the operating and economical costs of the ESS the local load demand and the participation to the electricity market and further it enforces the fulfillment of the physical and the system's dynamics constraints. The dynamics of the hydrogen-based ESS have been modeled by means of the mixed-logic dynamic (MLD) framework in order to capture different behaviors according to the possible operating modes. The purpose is to provide a controller able to cope both with all the main physical and operating constraints of a hydrogen-based storage system including the switching among different modes such as ON OFF STAND-BY and at the same time reduce the management costs and increase the equipment lifesaving. The case study for this paper is a plant under development in the north Norway. Numerical analysis on the related plant data shows the effectiveness of the proposed strategy which manages the plant and commits the equipment so as to preserve the given constraints and save them from unnecessary commutation cycles.
Influence of Thermal Treatment on SCC and HE Susceptibility of Supermartensitic Stainless Steel 16Cr5NiMo
Apr 2020
Publication
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.
Effect of Hot Mill Scale on Hydrogen Embrittlement of High Strength Steels for Pre-Stressed Concrete Structures
Mar 2018
Publication
The presence of a conductive layers of hot-formed oxide on the surface of bars for pre or post-compressing structures can promote localized attacks as a function of pH. The aggressive local environment in the occluded cells inside localized attacks has as consequence the possibility of initiation of stress corrosion cracking. In this paper the stress corrosion cracking behavior of high strength steels proposed for tendons was studied by means of Constant Load (CL) tests and Slow Strain Rate (SSR) tests. Critical ranges of pH for cracking were verified. The promoting role of localized attack was confirmed. Further electrochemical tests were performed on bars in as received surface conditions in order to evaluate pitting initiation. The adverse effect of mill scale was recognized.
Investigation of Mechanical Tests for Hydrogen Embrittlement in Automotive PHS Steels
Aug 2019
Publication
The problem of hydrogen embrittlement in ultra-high-strength steels is well known. In this study slow strain rate four-point bending and permeation tests were performed with the aim of characterizing innovative materials with an ultimate tensile strength higher than 1000 MPa. Hydrogen uptake in the case of automotive components can take place in many phases of the manufacturing process: during hot stamping due to the presence of moisture in the furnace atmosphere high-temperature dissociation giving rise to atomic hydrogen or also during electrochemical treatments such as cataphoresis. Moreover possible corrosive phenomena could be a source of hydrogen during an automobile’s life. This series of tests was performed here in order to characterize two press-hardened steels (PHS)—USIBOR 1500® and USIBOR 2000®—to establish a correlation between ultimate mechanical properties and critical hydrogen concentration.
Experimental Characterization of an Alkaline Electrolyser and a Compression System for Hydrogen Production and Storage
Aug 2021
Publication
Storing renewable energy in chemicals like hydrogen can bring various benefits like high energy density seasonal storability possible cost reduction of the final product and the potential to let renewable power penetrate other markets and to overcome their intermittent availability. In the last year’s production of this gas from renewable energy sources via electrolysis has grown its reputation as one feasible solution to satisfy future zero-emission energy demand. To extend the exploitation of Renewable Energy Source (RES) small-scale conversion plants seem to be an interesting option. In view of a possible widespread adoption of these types of plants the authors intend to present the experimental characterization of a small-scale hydrogen production and storage plant. The considered experimental plant is based on an alkaline electrolyser and an air-driven hydrogen compression and storage system. The results show that the hydrogen production-specific consumption is on average 77 kWh/kgH2 . The hydrogen compressor energy requirement is on average 15 kWh/kgH2 (data referred to the driving compressed air). The value is higher than data found in literature (4.4–9.3 kWh/kgH2 ) but the difference can be attributed to the small size of the considered compressor and the choice to limit the compression stages.
Graphene Oxide/metal Nanocrystal Multilaminates as the Atomic Limit for Safe and Selective Hydrogen Storage
Mar 2016
Publication
Interest in hydrogen fuel is growing for automotive applications; however safe dense solid-state hydrogen storage remains a formidable scientific challenge. Metal hydrides offer ample storage capacity and do not require cryogens or exceedingly high pressures for operation. However hydrides have largely been abandoned because of oxidative instability and sluggish kinetics. We report a new environmentally stable hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets. This material protected from oxygen and moisture by the rGO layers exhibits exceptionally dense hydrogen storage (6.5 wt% and 0.105 kg H2 per litre in the total composite). As rGO is atomically thin this approach minimizes inactive mass in the composite while also providing a kinetic enhancement to hydrogen sorption performance. These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments.
Tetrahydroborates: Development and Potential as Hydrogen Storage Medium
Oct 2017
Publication
The use of fossil fuels as an energy supply becomes increasingly problematic from the point of view of both environmental emissions and energy sustainability. As an alternative hydrogen is widely regarded as a key element for a potential energy solution. However differently from fossil fuels such as oil gas and coal the production of hydrogen requires energy. Alternative and intermittent renewable energy sources such as solar power wind power etc. present multiple advantages for the production of hydrogen. On the one hand the renewable sources contribute to a remarkable reduction of pollutants released to the air and on the other hand they significantly enhance the sustainability of energy supply. In addition the storage of energy in form of hydrogen has a huge potential to balance an effective and synergetic utilization of renewable energy sources. In this regard hydrogen storage technology is a key technology towards the practical application of hydrogen as “energy carrier”. Among the methods available to store hydrogen solid-state storage is the most attractive alternative from both the safety and the volumetric energy density points of view. Because of their appealing hydrogen content complex hydrides and complex hydride-based systems have attracted considerable attention as potential energy vectors for mobile and stationary applications. In this review the progresses made over the last century on the synthesis and development of tetrahydroborates and tetrahydroborate-based systems for hydrogen storage purposes are summarized.
Study of Hydrogen Enriched Premixed Flames
Sep 2005
Publication
In the present paper the theoretical study of the un-stretched laminar premixed flames of hydrogen-methane mixtures is carried out by using the detailed reaction mechanism GRI-Mech 3.0 implemented in the CHEMKIN software to find out the effect of hydrogen addition on the hybrid fuel burning velocity. The model results show that the laminar burning velocity of the hydrogen-methane mixtures is not the linear regression of those of the pure fuels since it results substantially less than the proportional averaging of the values for the fuel constituents. Moreover the effect of hydrogen addition in terms of enhancement of the mixture laminar burning velocity with respect to the methane is relevant only at very high values of the hydrogen content in the hybrid mixtures (> 70 % mol.). The performed sensitivity analysis shows that these results can be attributed to kinetics and in particular to the concentration of H radicals: depending on the hydrogen content in the fuels mixture the production of the H radicals can affect the limiting reaction step for methane combustion. Two regimes are identified in the hydrogen-methane combustion. The first regime is controlled by the methane reactivity the hydrogen being not able to significantly affect the laminar burning velocity (< 70 % mol.). In the second regime the hydrogen combustion has a relevant role as its high content in the hybrid fuel leads to a significant H radicals pool thus enhancing the reaction rate of the more slowly combusting methane.
Risk Analysis of the Storage Unit in Hydrogen Refuelling Station
Sep 2007
Publication
Nowadays consumer demand for local and global environmental quality in terms of air pollution and in particular greenhouse gas emissions reduction may help to drive to the introduction of zero emission vehicles. At this regard the hydrogen technology appears to have future market valuablepotential. On the other hand the use of hydrogen vehicles which requires appropriate infrastructures for production storage and refuelling stages presents a lot of safety problems due to the peculiar chemicophysical hydrogen characteristics. Therefore safe at the most practices are essential for the successful proliferation of hydrogen vehicles. Indeed to avoid limit hazards it is necessary to implement practices that if early adopted in the development of a fuelling station project can allow very low environmental impact safety being incorporated in the project itself. Such practices generally consist in the integrated use of Failure Mode and Effect Analysis (FMEA) HAZard OPerability (HAZOP) and Fault Tree Analysis (FTA) which constitute well established standards in reliability engineering. At this regard however a drawback is the lack of experience and the scarcity of the relevant data collection. In this work we present the results obtained by the integrated use of FMEA HAZOP and FTA analyses relevant for the moment the high-pressure storage equipment in a hydrogen gas refuelling station. The study that is intended to obtain elements for improving safety of the system can constitute a basis for further more refined works.
Inhomogeneous Hydrogen Deflagrations in the Presence of Obstacles in 25 m3 Enclosure. Experimental Results
Sep 2019
Publication
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. Blind-prediction exercises recently published show a large spread in the prediction of both engineering formula than CFD tools. University of Pisa performed experimental tests in a 25 m3 facility in inhomogeneous conditions and with the presence of simple obstacles constituted by plates bolted to HEB beams. The present paper is aimed to share the results of hydrogen dispersion and deflagration tests and discuss the comparison of maximum peak overpressure generated with different blockage ratio and repeated obstacles sets. Description of the experimental set-up includes all the details deemed necessary to reproduce the phenomenon with a CFD tool.
Integrating IT-SOFC and Gasification Combined Cycle with Methanation Reactor and Hydrogen Firing for Near Zero-emission Power Generation from Coal
Apr 2011
Publication
Application of Solid Oxide Fuel Cells (SOFC) in gasification-based power plants would represent a turning point in the power generation sector allowing to considerably increase the electric efficiency of coal-fired power stations while reducing CO2 and other pollutant emissions. The aim of this paper is the thermodynamic assessment of a SOFC-based IGFC plant with methanation reactor hydrogen post-firing and CO2 capture by physical absorption. The configuration proposed allows to obtain a very high net efficiency (51.6%) overcoming the main limits of configurations assessed in previous works.
Material Testing and Design Recommendations for Components Exposed to Hydrogen Enhanced Fatigue – the Mathryce Project
Sep 2013
Publication
The three years European MATHRYCE project dedicated to material testing and design recommendations for components exposed to hydrogen enhanced fatigue started in October 2012. Its main goal is to provide an “easy” to implement methodology based on lab-scale experimental tests under hydrogen gas to assess the service life of a real scale component taking into account fatigue loading under hydrogen gas. Dedicated experimental tests will be developed for this purpose. In the present paper the proposed approach is presented and compared to the methodologies currently developed elsewhere in the world.
Experimental Study of Hydrogen Releases in the Passenger Compartment of a Piaggio Porter
Sep 2011
Publication
There are currently projects and demonstration programs aiming at introducing Hydrogen powered Fuel Cell (HFC) vehicles into the market. Regione Toscana has been cofounder of the project “H2 Filiera Idrogeno” whose goal is to achieve a clean and sustainable mobility through HFC vehicle studies covering their production storage and use. Among the goals of the project was the substitution of the electric propulsion system with a hydrogen fuel cells propulsion system. This work presents a brief overview of the necessary modifications of the electric propulsion version of a Piaggio Porter to host a H2 fuel cell and experimental studies of realistic H2 releases from the vehicle. The scenarios covered H2 unintended releases underneath the vehicle when at rest and focused on three types of releases diffusive major and minor that might reach the interior of the vehicle and potentially pose a direct risk to the passengers.
Trends in Gas Sensor Development for Hydrogen Safety
Sep 2013
Publication
Gas sensors are applied for facilitating the safe use of hydrogen in for example fuel cell and hydrogen fuelled vehicles. New sensor developments aimed at meeting the increasingly stringent performance requirements in emerging applications are presented based on in-house technical developments and a literature study. The strategy of combining different detection principles i.e. sensors based on electrochemical cells semiconductors or field effects in combination with thermal conductivity sensor or catalytic combustion elements in one new measuring system is reported. This extends the dynamic measuring range of the sensor while improving sensor reliability to achieve higher safety integrity through diverse redundancy. The application of new nanoscaled materials nano wires carbon tubes and graphene as well as the improvements in electronic components of field-effect resistive-type and optical systems are evaluated in view of key operating parameters such as sensor response time low energy consumption and low working temperature.
CFD Simulations on Small Hydrogen Releases Inside a Ventilated Facility and Assessment of Ventilation Efficiency
Sep 2009
Publication
The use of stationary H2 and fuel cell systems is expected to increase rapidly in the future. In order to facilitate the safe introduction of this new technology the HyPer project funded by the EC developed a public harmonized Installation Permitting Guidance (IPG) document for the installation of small stationary H2 and fuel cell systems for use in various environments. The present contribution focuses on the safety assessment of a facility inside which a small H2 fuel cell system (4.8 kWe) is installed and operated. Dispersion experiments were designed and performed by partner UNIPI. The scenarios considered cover releases occurring inside the fuel cell at the valve of the inlet gas pipeline just before the pressure regulator which controls the H2 flow to the fuel cell system. H2 was expected to leak out of the fuel cell into the facility and then outdoors through the ventilation system. The initial leakage diameter was chosen based on the Italian technical guidelines for the enforcement of the ATEX European directive. Several natural ventilation configurations were examined. The performed tests were simulated by NCSRD using the ADREA-HF code. The numerical analysis took into account the full interior of the fuel cell in order to investigate for any potential accumulation effects. Comparisons between predicted and experimental H2 concentrations at 4 sensor locations inside the facility are reported. Finally an overall assessment of the ventilation efficiency was made based on the simulations and experiments.
Recent Developments in Pd-CeO2 Nano-composite Electrocatalysts for Anodic Reactions in Anion Exchange Membrane Fuel Cells
Jan 2022
Publication
In 2016 for the first time a polymer electrolyte fuel cell free of Pt electrocatalysts was shown to deliver more than 0.5 W cm-2 of peak power density from H2 and air (CO2 free). This was achieved with a silver-based oxygen reduction (ORR) cathode and a Pd-CeO2 hydrogen oxidation reaction (HOR) anodic electrocatalyst. The poor kinetics of the HOR under alkaline conditions is a considerable challenge to Anion Exchange Membrane Fuel Cell (AEMFC) development as high Pt loadings are still required to achieve reasonable performance. Previously the ameliorative combination of Pd and CeO2 nanocomposites has been exploited mostly in heterogeneous catalysis where the positive interaction is well documented. Carbon supported PdCeO2 HOR catalysts have now been prepared by different synthetic techniques and employed in AEMFCs as alternative to Pt and PtRu standards. Important research has also been recently reported delving into the origin of the HOR enhancement on Pd-CeO2. Such work has highlighted the importance of the bifunctional mechanism of the HOR at high pHs. Carefully prepared nano-structures of Pd and CeO2 that promote the formation of the Pd-O-Ce interface provide optimal binding of both Had and OHad species aspects which are crucial for enhanced HOR kinetics. This review paper discusses the recent advances in Pd-CeO2 electrocatalysts for AEMFC anodes.
Homogeneous and Inhomogeneous Hydrogen Deflagrations in 25 m3 Enclosure
Sep 2019
Publication
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.
Safety Distances: Comparison of the Methodologies for Their Determination
Sep 2011
Publication
In this paper a study on the comparison between the different methodologies for the determination of the safety distances proposed by Standard Organizations and national Regulations is presented. The application of the risk-informed approach is one of the methodologies used for the determination of safety distances together with the risk-based approach. One of the main differences between the various methodologies is the risk criterion chosen. In fact a critical point is which level of risk should be used and then which are the harm events that must be considered. The harm distances are evaluated for a specified leak diameter that is a consequence of some parameters used in the various methodologies. The values of the safety distances proposed by Standard Organizations and national Regulations are a demonstration of the different approaches of the various methodologies especially in the choice of the leak diameter considered.
Integration of Open Slag Bath Furnace with Direct Reduction Reactors for New‐Generation Steelmaking
Jan 2022
Publication
The present paper illustrates an innovative steel processing route developed by employing hydrogen direct reduced pellets and an open slag bath furnace. The paper illustrates the direct reduction reactor employing hydrogen as reductant on an industrial scale. The solution allows for the production of steel from blast furnace pellets transformed in the direct reduction reactor. The reduced pellets are then melted in open slag bath furnaces allowing carburization for further refining. The proposed solution is clean for the decarbonization of the steel industry. The kinetic chemical and thermodynamic issues are detailed with particular attention paid to the slag conditions. The proposed solution is also supported by the economic evaluation compared to traditional routes.
Non-monotonic Overpressure vs. H2 Concentration Behaviour During Vented Deflagration. Experimental Results
Oct 2015
Publication
Explosion relief panels or doors are often used in industrial buildings to reduce damages caused by gas explosions. Decades of research have contributed to the understanding of the phenomena involved in gas explosions in order to establish an effective method to predict reliably the explosion overpressure. All the methods predict a monotonic increase of the overpressure with the concentration of the gas in the range from the lower explosion limit to the stoichiometric one. Nevertheless in few cases a non-monotonic behaviour of the maximum developed pressure as a function of hydrogen concentration was reported in the literature. The non-monotonic behaviour was also observed during experimental tests performed at the Scalbatraio laboratory at the University of Pisa in a 25 m3 vented combustion test facility with a vent area of 112 m2. This paper presents the results obtained during the tests and investigates the possible explanations of the phenomena.
Green H2 Production by Water Electrolysis Using Cation Exchange Membrane: Insights on Activation and Ohmic Polarization Phenomena
Dec 2021
Publication
Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play an important role in hydrogen energy transition. This work presents a study on the performance of a proton exchange membrane in the water electrolysis process at room temperature and atmospheric pressure. In the perspective of applications that need a device with small volume and low weight a miniaturized electrolysis cell with a 36 cm2 active area of PEM over a total surface area of 76 cm2 of the device was used. H2 and O2 production rates electrical power energy efficiency Faradaic efficiency and polarization curves were determined for all experiments. The effects of different parameters such as clamping pressure and materials of the electrodes on polarization phenomena were studied. The PEM used was a catalyst-coated membrane (Ir-Pt-Nafion™ 117 CCM). The maximum H2 production was about 0.02 g min−1 with a current density of 1.1 A cm−2 and a current power about 280 W. Clamping pressure and the type of electrode materials strongly influence the activation and ohmic polarization phenomena. High clamping pressure and electrodes in titanium compared to carbon electrodes improve the cell performance and this results in lower ohmic and activation resistances.
European Hydrogen Safety Training Programme for First Responders: Hyresponse Outcomes and Perspectives
Sep 2017
Publication
The paper presents the outcomes of the HyResponse project i.e. the European Hydrogen Safety Training Programme for first responders. The threefold training is described: the content of the educational training is presented the operational training platform and its mock-up real scale transport and hydrogen stationary installations are detailed and the innovative virtual tools and training exercises are highlighted. The paper underlines the outcomes the three pilot sessions as well as the Emergency Response Guide available on the HyResponse’s public website. The next steps for widespread dissemination into the community are discussed.
Cylinders and Tubes Used as Buffers in Filling Stations
Oct 2015
Publication
Buffers are key components for hydrogen filling stations that are currently being developed. Type 1 or composite cylinders are used for this application. The type used depends on many parameters including pressure level cost and space available for the filling station. No international standards exist for such high pressure vessels whereas many standards exist covering Types 123 and 4 used for transport of gas or on-board fuel tanks. It is suggested to use the cylinders approved for transport or on-board applications as buffers. This solution appears to be safe if at least one issue is solved. The main difference is that transport or on-board cylinders are cycled from a low pressure to a high pressure during service whereas buffers are cycled from a relatively high pressure (corresponding to the vehicle’s filling pressure) to the MAWP. Another difference is that buffers are cycled many times per day. For standards developers requesting to systematically verify that buffers pass millions of cycles at low pressure amplitude would be impractical. Several standards and codes give formulae to estimate the number of shallow cycles when number of deep cycles are known. In this paper we describe tests performed on all types of composite cylinders to verify or determine the appropriate formulae.
Soft-linking of a Behavioral Model for Transport with Energy System Cost optimization Applied to Hydrogen in EU
Sep 2019
Publication
Fuel cell electric vehicles (FCEV) currently have the challenge of high CAPEX mainly associated to the fuel cell. This study investigates strategies to promote FCEV deployment and overcome this initial high cost by combining a detailed simulation model of the passenger transport sector with an energy system model. The focus is on an energy system with 95% CO2 reduction by 2050. Soft-linking by taking the powertrain shares by country from the simulation model is preferred because it considers aspects such as car performance reliability and safety while keeping the cost optimization to evaluate the impact on the rest of the system. This caused a 14% increase in total cost of car ownership compared to the cost before soft-linking. Gas reforming combined with CO2 storage can provide a low-cost hydrogen source for FCEV in the first years of deployment. Once a lower CAPEX for FCEV is achieved a higher hydrogen cost from electrolysis can be afforded. The policy with the largest impact on FCEV was a purchase subsidy of 5 k€ per vehicle in the 2030–2034 period resulting in 24.3 million FCEV (on top of 67 million without policy) sold up to 2050 with total subsidies of 84 bln€. 5 bln€ of R&D incentives in the 2020–2024 period increased the cumulative sales up to 2050 by 10.5 million FCEV. Combining these two policies with infrastructure and fuel subsidies for 2030–2034 can result in 76 million FCEV on the road by 2050 representing more than 25% of the total car stock. Country specific incentives split of demand by distance or shift across modes of transport were not included in this study.
Micro-wrinkled Pd Surface for Hydrogen Sensing and Switched Detection of Lower Explosive Limit
Sep 2011
Publication
We report the development and testing of a novel hydrogen sensor that shows a very peculiar response to hydrogen exposure due to its micro-structured palladium surface. The fabrication of the wrinkled Pd surface is obtained using an innovative fast and cheap technique based on the deposition of a thin Pd film on to a thermo-retractable polystyrene sheet that shrinks to 40% of its original size when heated. The buckling of the Pd surface induced by shrinking of the substrate produces nano and micro-wrinkles on the sensor surface. The micro-structured sensor surface is very stable even after repeated hydrogen sorption/desorption cycles. The hydrogen sensing mechanism is based on the transitory absorption of hydrogen atoms into the Pd layer leading to the reversible change of its electrical resistance. Interestingly depending on hydrogen concentration the proposed sensor shows the concurrent effect of both the usually described behaviors of increase or decrease of resistance related to different phenomena occurring upon hydrogen exposure and formation of palladium hydride. The study reports and discusses evidences for an activation threshold of hydrogen concentration in air switching the behavior of sensor performances from e.g. poor negative to large positive sensitivity and from slow to fast detection.
Hydrogen Permeation in X65 Steel under Cyclic Loading
May 2020
Publication
This experimental work analyzes the hydrogen embrittlement mechanism in quenched and tempered low-alloyed steels. Experimental tests were performed to study hydrogen diffusion under applied cyclic loading. The permeation curves were fitted by considering literature models in order to evaluate the role of trapping—both reversible and irreversible—on the diffusion mechanism. Under loading conditions a marked shift to the right of the permeation curves was noticed mainly at values exceeding the tensile yield stress. In the presence of a relevant plastic strain the curve changes due to the presence of irreversible traps which efficiently subtract diffusible atomic hydrogen. A significant reduction in the apparent diffusion coefficient and a considerable increase in the number of traps were noticed as the maximum load exceeded the yield strength. Cyclic loading at a tensile stress slightly higher than the yield strength of the material increases the hydrogen entrapment phenomena. The tensile stress causes a marked and instant reduction in the concentration of mobile hydrogen within the metal lattice from 55% of the yield strength and it increases significantly in the plastic field.
Experimental Measurements of Structural Displacement During Hydrogen Vented Deflagrations for FE Model Validation
Sep 2017
Publication
Vented deflagration tests were conducted by UNIPI at B. Guerrini Laboratory during the experimental campaign for HySEA project. Experiments included homogeneous hydrogen-air mixture in a 10-18% vol. range of concentrations contained in an about 1 m3 enclosure called SSE (Small Scale Enclosure). Displacement measurements of a test plate were taken in order to acquire useful data for the validation of FE model developed by IMPETUS Afea. In this paper experimental facility displacement measurement system and FE model are briefly described then comparison between experimental data and simulation results is discussed.
Seasonal Energy Storage for Zero-emissions Multi-energy Systems Via Underground Hydrogen Storage
Jan 2020
Publication
The deployment of diverse energy storage technologies with the combination of daily weekly and seasonal storage dynamics allows for the reduction of carbon dioxide (CO2) emissions per unit energy provided. In particular the production storage and re-utilization of hydrogen starting from renewable energy has proven to be one of the most promising solutions for offsetting seasonal mismatch between energy generation and consumption. A realistic possibility for large-scale hydrogen storage suitable for long-term storage dynamics is presented by salt caverns. In this contribution we provide a framework for modelling underground hydrogen storage with a focus on salt caverns and we evaluate its potential for reducing the CO2 emissions within an integrated energy systems context. To this end we develop a first-principle model which accounts for the transport phenomena within the rock and describes the dynamics of the stored energy when injecting and withdrawing hydrogen. Then we derive a linear reduced order model that can be used for mixed-integer linear program optimization while retaining an accurate description of the storage dynamics under a variety of operating conditions. Using this new framework we determine the minimum-emissions design and operation of a multi-energy system with H2 storage. Ultimately we assess the potential of hydrogen storage for reducing CO2 emissions when different capacities for renewable energy production and energy storage are available mapping emissions regions on a plane defined by storage capacity and renewable generation. We extend the analysis for solar- and wind-based energy generation and for different energy demands representing typical profiles of electrical and thermal demands and different CO2 emissions associated with the electric grid.
Modelling and Optimization of a Flexible Hydrogen-fueled Pressurized PEMFC Power Plant for Grid Balancing Purposes
Feb 2021
Publication
In a scenario characterized by an increasing penetration of non-dispatchable renewable energy sources and the need of fast-ramping grid-balancing power plants the EU project GRASSHOPPER aims to setup and demonstrate a highly flexible PEMFC Power Plant hydrogen fueled and scalable to MW-size designed to provide grid support.<br/>In this work different layouts proposed for the innovative MW-scale plant are simulated to optimize design and off-design operation. The simulation model details the main BoP components performances and includes a customized PEMFC model validated through dedicated experiments.<br/>The system may operate at atmospheric or mild pressurized conditions: pressurization to 0.7 barg allows significantly higher net system efficiency despite the increasing BoP consumptions. The additional energy recovery from the cathode exhaust with an expander gives higher net power and net efficiency adding up to 2%pt and reaching values between 47%LHV and 55%LHV for currents between 100% and 20% of the nominal value.
Feasibility Investigation of Hydrogen Refuelling Infrastructure for Heavy‐Duty Vehicles in Canada
Apr 2022
Publication
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.
Statistics, Lessons Learned and Recommendations from Analysis of HIAD 2.0 Database
Mar 2022
Publication
The manuscript firstly describes the data collection and validation process for the European Hydrogen Incidents and Accidents Database (HIAD 2.0) a public repository tool collecting systematic data on hydrogen-related incidents and near-misses. This is followed by an overview of HIAD 2.0 which currently contains 706 events. Subsequently the approaches and procedures followed by the authors to derive lessons learned and formulate recommendations from the events are described. The lessons learned have been divided into four categories including system design; system manufacturing installation and modification; human factors and emergency response. An overarching lesson learned is that minor events which occurred simultaneously could still result in serious consequences echoing James Reason's Swiss Cheese theory. Recommendations were formulated in relation to the established safety principles adapted for hydrogen by the European Hydrogen Safety Panel considering operational modes industrial sectors and human factors. This work provide an important contribution to the safety of systems involving hydrogen benefitting technical safety engineers emergency responders and emergency services. The lesson learned and the discussion derived from the statistics can also be used in training and risk assessment studies being of equal importance to promote and assist the development of sound safety culture in organisations.
Hydrogen as a Clean and Sustainable Energy Vector for Global Transition from Fossil-Based to Zero-Carbon
Dec 2021
Publication
Hydrogen is recognized as a promising and attractive energy carrier to decarbonize the sectors responsible for global warming such as electricity production industry and transportation. However although hydrogen releases only water as a result of its reaction with oxygen through a fuel cell the hydrogen production pathway is currently a challenging issue since hydrogen is produced mainly from thermochemical processes (natural gas reforming coal gasification). On the other hand hydrogen production through water electrolysis has attracted a lot of attention as a means to reduce greenhouse gas emissions by using low-carbon sources such as renewable energy (solar wind hydro) and nuclear energy. In this context by providing an environmentally-friendly fuel instead of the currently-used fuels (unleaded petrol gasoline kerosene) hydrogen can be used in various applications such as transportation (aircraft boat vehicle and train) energy storage industry medicine and power-to-gas. This article aims to provide an overview of the main hydrogen applications (including present and future) while examining funding and barriers to building a prosperous future for the nation by addressing all the critical challenges met in all energy sectors.
Experimental Study of Vented Hydrogen Deflagration with Ignition Inside and Outside the Vented Volume
Sep 2013
Publication
Experiments were carried out inside a 25 m3 vented combustion test facility (CVE) with a fixed vent area sealed by a plastic sheet vent. Inside the CVE a 0.64 m3 open vent box called RED-CVE was placed. The vent of the RED-CVE was left open and three different vent area were tested. Two different mixing fans one for each compartment were used to establish homogeneous H2 concentrations. This study examined H2 concentrations in the range between 8.5% vol. to 12.5% vol. and three different ignition locations (1) far vent ignition (2) inside the RED-CVE box ignition and (3) near vent ignition (the vent refers to the CVE vent). Peak overpressures generated inside the test facility and the smaller compartment were measured. The results indicate that the near vent ignition generates negligible peak overpressures inside the test facility as compared to those originated by far vent ignition and ignition inside the RED-CVE box. The experiments with far vent ignition showed a pressure increase with increasing hydrogen concentration which reached a peak value at 11% vol. concentration and then decreased showing a non-monotonic behaviour. The overpressure measured inside the RED-CVE was higher when the ignition was outside the box whereas the flame entered the box through the small vent.
Integration of Experimental Facilities: A Joint Effort for Establishing a Common Knowledge Base in Experimental Work on Hydrogen Safety
Sep 2009
Publication
With regard to the goals of the European HySafe Network research facilities are essential for the experimental investigation of relevant phenomena for testing devices and safety concepts as well as for the generation of validation data for the various numerical codes and models. The integrating activity ‘Integration of Experimental Facilities (IEF)’ has provided basic support for jointly performed experimental work within HySafe. Even beyond the funding period of the NoE HySafe in the 6th Framework Programme IEF represents a long lasting effort for reaching sustainable integration of the experimental research capacities and expertise of the partners from different research fields. In order to achieve a high standard in the quality of experimental data provided by the partners emphasis was put on the know-how transfer between the partners. The strategy for reaching the objectives consisted of two parts. On the one hand a documentation of the experimental capacities has been prepared and analysed. On the other hand a communication base has been established by means of biannual workshops on experimental issues. A total of 8 well received workshops has been organised covering topics from measurement technologies to safety issues. Based on the information presented by the partners a working document on best practice including the joint experimental knowledge of all partners with regard to experiments and instrumentation was created. Preserving the character of a working document it was implemented in the IEF wiki website which was set up in order to provide a central communication platform. The paper gives an overview of the IEF network activities over the last 5 years.
Risk Analysis of Complex Hydrogen Infrastructures
Oct 2015
Publication
Building a network of hydrogen refuelling stations is essential to develop the hydrogen economy within transport. Additional hydrogen is regarded a likely key component to store and convert back excess electrical power to secure future energy supply and to improve the quality of biomass-based fuels. Therefore future hydrogen supply and distribution chains will have to address several objectives. Such a complexity is a challenge for risk assessment and risk management of these chains because of the increasing interactions. Improved methods are needed to assess the supply chain as a whole. The method of “Functional modelling” is discussed in this paper. It will be shown how it could be a basis for other decision support methods for comprehensive risk and sustainability assessments.
Mixing of Dense or Light Gases with Turbulent Air- a Fast-Running Model for Lumped Parameter Codes
Sep 2005
Publication
The release of gases heavier than air like propane at ground level or lighter than air like hydrogen close to a ceiling can both lead to fire and explosion hazards that must be carefully considered in safety analyses. Even if the simulation of accident scenarios in complex installations and long transients often appears feasible only using lumped parameter computer codes the phenomenon of denser or lighter gas dispersion is not implicitly accounted by these kind of tools. In the aim to set up an ad hoc model to be used in the computer code ECART fluid-dynamic simulations by the commercial FLUENT 6.0 CFD code are used. The reference geometry is related to cavities having variable depth (2 to 4 m) inside long tunnels filled with a gas heavier or lighter than air (propane or hydrogen). Three different geometrical configurations with a cavity width of 3 6 and 9 m are considered imposing different horizontal air stream velocities ranging from 1 to 5 m/s. A stably-stratified flow region is observed inside the cavity during gas shearing. In particular it is found that the density gradient tends to inhibit turbulent mixing thus reducing the dispersion rate. The obtained data are correlated in terms of main dimensionless groups by means of a least squares method. In particular the Sherwood number is correlated as a function of Reynolds a density ratio modified Froude numbers and in terms of the geometrical parameter obtained as a ratio between the depth of the air-dense gas interface and the length of the cavity. This correlation is implemented in the ECART code to add the possibility to simulate large installations during complex transients lasting many hours with reasonable computation time. An example of application to a typical case is presented.
Development of an Italian Fire Prevention Technical Rule For Hydrogen Pipelines
Sep 2011
Publication
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.
On the Use of Hydrogen in Confined Spaces: Results from the Internal Project InsHyde
Sep 2009
Publication
Alexandros G. Venetsanos,
Paul Adams,
Inaki Azkarate,
A. Bengaouer,
Marco Carcassi,
Angunn Engebø,
E. Gallego,
Olav Roald Hansen,
Stuart J. Hawksworth,
Thomas Jordan,
Armin Keßler,
Sanjay Kumar,
Vladimir V. Molkov,
Sandra Nilsen,
Ernst Arndt Reinecke,
M. Stöcklin,
Ulrich Schmidtchen,
Andrzej Teodorczyk,
D. Tigreat,
N. H. A. Versloot and
L. Boon-Brett
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.
Effects of Steam Injection on the Permissible Hydrogen Content and Gaseous Emissions in a Micro Gas Turbine Supplied by a Mixture of CH4 and H2: A CFD Analysis
Apr 2022
Publication
The use of hydrogen in small scale gas turbines is currently limited by several issues. Blending hydrogen with methane or other gaseous fuels can be considered a low medium-term viable solution with the goal of reducing greenhouse gas emissions. In fact only small amounts can be mixed with methane in premixed combustors due to the risk of flashback. The aim of this article is to investigate the injection of small quantities of steam as a method of increasing the maximum permissible hydrogen content in a mixture with methane. The proposed approach involves introducing the steam directly into the combustion chamber into the main fuel feeding system of a Turbec T100. The study is carried out by means of CFD analysis of the combustion process. A thermodynamic analysis of the energy system is used to determine boundary conditions. The combustion chamber is discretized using a three-dimensional mesh consisting of 4.7 million nodes and the RANS RSM model is used to simulate the effects of turbulence. The results show that the addition of steam may triple the permissible percentage of hydrogen in the mixture for the considered MGT passing from 10% to over 30% by volume also leading to a reduction in NOx emissions without a significant variation in CO emissions.
Fire Prevention Technical Rule for Gaseous Hydrogen Transport in Pipelines
Sep 2007
Publication
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.
Consequence Assessment of the BBC Hydrogen Refuelling Station, Using The Adrea-Hf Code
Sep 2009
Publication
Within the framework of the internal project HyQRA of the HYSAFE Network of Excellence (NoE) funded by the European Commission (EC) the participating partners were requested to apply their Quantitative Risk Assessment (QRA) methodologies on a predefined hypothetical gaseous H2 refuelling station named BBC (Benchmark Base Case). The overall aim of the HyQRA project was to perform an inter-comparison of the various QRA approaches and to identify the knowledge gaps on data and information needed in the QRA steps specifically related to H2. Partners NCSRD and UNIPI collaborated on a common QRA. UNIPI identified the hazards on site selected the most critical ones defined the events that could be the primary cause of an accident and provided to NCSRD the scenarios listed in risk order for the evaluation of the consequences. NCSRD performed the quantitative analysis using the ADREA-HF CFD code. The predicted risk assessment parameters (flammable H2 mass and volume time histories and maximum horizontal and vertical distances of the LFL from the source) were provided to UNIPI to analyze the consequences and to evaluate the risk and distances of damage. In total 15 scenarios were simulated. Five of them were H2 releases in confined ventilated spaces (inside the compression and the purification/drying buildings). The remaining 10 scenarios were releases in open/semi-confined spaces (in the storage cabinet storage bank and refuelling hose of one dispenser). This paper presents the CFD methodology applied for the quantitative analysis of the common UNIPI/NCSRD QRA and discusses the results obtained from the performed calculations.
Numerical Analysis of VPSA Technology Retrofitted to Steam Reforming Hydrogen Plants to Capture CO2 and Produce Blue H2
Feb 2022
Publication
The increasing demand for energy and commodities has led to escalating greenhouse gas emissions the chief of which is represented by carbon dioxide (CO2). Blue hydrogen (H2) a lowcarbon hydrogen produced from natural gas with carbon capture technologies applied has been suggested as a possible alternative to fossil fuels in processes with hard-to-abate emission sources including refining chemical petrochemical and transport sectors. Due to the recent international directives aimed to combat climate change even existing hydrogen plants should be retrofitted with carbon capture units. To optimize the process economics of such retrofit it has been proposed to remove CO2 from the pressure swing adsorption (PSA) tail gas to exploit the relatively high CO2 concentration. This study aimed to design and numerically investigate a vacuum pressure swing adsorption (VPSA) process capable of capturing CO2 from the PSA tail gas of an industrial steam methane reforming (SMR)-based hydrogen plant using NaX zeolite adsorbent. The effect of operating conditions such as purge-to-feed ratio and desorption pressure were evaluated in relation to CO2 purity CO2 recovery bed productivity and specific energy consumption. We found that conventional cycle configurations namely a 2-bed 4-step Skarstrom cycle and a 2-bed 6-step modified Skarstrom cycle with pressure equalization were able to concentrate CO2 to a purity greater than 95% with a CO2 recovery of around 77% and 90% respectively. Therefore the latter configuration could serve as an efficient process to decarbonize existing hydrogen plants and produce blue H2.
Comprehensive Review on Fuel Cell Technology for Stationary Applications as Sustainable and Efficient Poly-Generation Energy Systems
Aug 2021
Publication
Fuel cell technologies have several applications in stationary power production such as units for primary power generation grid stabilization systems adopted to generate backup power and combined-heat-and-power configurations (CHP). The main sectors where stationary fuel cells have been employed are (a) micro-CHP (b) large stationary applications (c) UPS and IPS. The fuel cell size for stationary applications is strongly related to the power needed from the load. Since this sector ranges from simple backup systems to large facilities the stationary fuel cell market includes few kWs and less (micro-generation) to larger sizes of MWs. The design parameters for the stationary fuel cell system differ for fuel cell technology (PEM AFC PAFC MCFC and SOFC) as well as the fuel type and supply. This paper aims to present a comprehensive review of two main trends of research on fuel-cell-based poly-generation systems: tracking the market trends and performance analysis. In deeper detail the present review will list a potential breakdown of the current costs of PEM/SOFC production for building applications over a range of production scales and at representative specifications as well as broken down by component/material. Inherent to the technical performance a concise estimation of FC system durability efficiency production maintenance and capital cost will be presented.
The Deltah Lab, a New Multidisciplinary European Facility to Support the H2 Distribution & Storage Economy
Apr 2021
Publication
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.
Engineering Thoughts on Hydrogen Embrittlement
Jul 2018
Publication
Hydrogen Embrittlement (HE) is a topical issue for pipelines transporting sour products. Engineers need a simple and effective approach in materials selection at design stage. In other words they must know if a material is susceptible to cracking to be able of:
As an example material selection for sour service pipeline is the object of well-known standards e.g. by Nace International and EFC: they pose some limits in the sour service of steels with reference to surface hardness. These standards have shown some weak points namely:
- selecting the right material
- and apply correct operational measures during the service life.
As an example material selection for sour service pipeline is the object of well-known standards e.g. by Nace International and EFC: they pose some limits in the sour service of steels with reference to surface hardness. These standards have shown some weak points namely:
- In the definition of sour service;
- In defining the role of crack initiation and propagation considering that in Hydrogen embrittlement stress state and stress variations are very important.
Hydrogen Embrittlement in Advanced High Strength Steels and Ultra High Strength Steels: A New Investigation Approach
Dec 2018
Publication
In order to reduce CO2 emissions and fuel consumption and to respect current environmental norms the reduction of vehicles weight is a primary target of the automotive industry. Advanced High Strength Steels (AHSS) and Ultra High Strength Steel (UHSS) which present excellent mechanical properties are consequently increasingly used in vehicle manufacturing. The increased strength to mass ratio compensates the higher cost per kg and AHSS and UHSS are proving to be cost-effective solutions for the body-in-white of mass market products.
In particular aluminized boron steel can be formed in complex shapes with press hardening processes acquiring high strength without distortion and increasing protection from crashes. On the other hand its characteristic martensitic microstructure is sensitive to hydrogen delayed fracture phenomena and at the same time the dew point in the furnace can produce hydrogen consequently to the high temperature reaction between water and aluminum. The high temperature also promotes hydrogen diffusion through the metal lattice under the aluminum-silicon coating thus increasing the diffusible hydrogen content. However after cooling the coating acts as a strong barrier preventing the hydrogen from going out of the microstructure. This increases the probability of delayed fracture. As this failure brings to the rejection of the component during production or even worse to the failure in its operation diffusible hydrogen absorbed in the component needs to be monitored during the production process.
For fast and simple measurements of the response to diffusible hydrogen of aluminized boron steel one of the HELIOS innovative instruments was used HELIOS II. Unlike the Devanathan cell that is based on a double electrochemical cell HELIOS II is based on a single cell coupled with a solid-state sensor. The instrument is able to give an immediate measure of diffusible hydrogen content in sheet steels semi-products or products avoiding time-consuming specimen palladium coating with a guided procedure that requires virtually zero training.
Two examples of diffusible hydrogen analyses are given for Usibor®1500-AS one before hot stamping/ quenching and one after hot stamping suggesting that the increase in the number of dislocations during hot stamping could be the main responsible for the lower apparent diffusivity of hydrogen.
In particular aluminized boron steel can be formed in complex shapes with press hardening processes acquiring high strength without distortion and increasing protection from crashes. On the other hand its characteristic martensitic microstructure is sensitive to hydrogen delayed fracture phenomena and at the same time the dew point in the furnace can produce hydrogen consequently to the high temperature reaction between water and aluminum. The high temperature also promotes hydrogen diffusion through the metal lattice under the aluminum-silicon coating thus increasing the diffusible hydrogen content. However after cooling the coating acts as a strong barrier preventing the hydrogen from going out of the microstructure. This increases the probability of delayed fracture. As this failure brings to the rejection of the component during production or even worse to the failure in its operation diffusible hydrogen absorbed in the component needs to be monitored during the production process.
For fast and simple measurements of the response to diffusible hydrogen of aluminized boron steel one of the HELIOS innovative instruments was used HELIOS II. Unlike the Devanathan cell that is based on a double electrochemical cell HELIOS II is based on a single cell coupled with a solid-state sensor. The instrument is able to give an immediate measure of diffusible hydrogen content in sheet steels semi-products or products avoiding time-consuming specimen palladium coating with a guided procedure that requires virtually zero training.
Two examples of diffusible hydrogen analyses are given for Usibor®1500-AS one before hot stamping/ quenching and one after hot stamping suggesting that the increase in the number of dislocations during hot stamping could be the main responsible for the lower apparent diffusivity of hydrogen.
An Energy Autonomous House Equipped with a Solar PV Hydrogen Conversion System
Dec 2015
Publication
The use of RES in buildings is difficult for their random nature; therefore the plants using photovoltaic solar collectors must be connected to a power supply or interconnected with Energy accumulators if the building is isolated. The conversion of electricity into hydrogen technology is best suited to solve the problem and allows you to transfer the solar energy captured from day to night from summer to winter. This paper presents the feasibility study for a house powered by PV cogeneration solar collectors that reverse the electricity on the control unit that you command by a PC to power the household using a heat pump an electrolytic cell for the production of hydrogen to accumulate; control units sorting to the utilities the electricity produced by the fuel cell. The following are presented: The Energy analysis of the building the plant design economic analysis.
Micro Gas Turbine Role in Distributed Generation with Renewable Energy Sources
Jan 2023
Publication
To become sustainable the production of electricity has been oriented towards the adoption of local and renewable sources. Distributed electric and thermal energy generation is more suitable to avoid any possible waste and the Micro Gas Turbine (MGT) can play a key role in this scenario. Due to the intrinsic properties and the high flexibility of operation of this energy conversion system the exploitation of alternative fuels and the integration of the MGT itself with other energy conversion systems (solar field ORC fuel cells) represent one of the most effective strategies to achieve higher conversion efficiencies and to reduce emissions from power systems. The present work aims to review the results obtained by the researchers in the last years. The different technologies are analyzed in detail both separately and under a more complete view considering two or more solutions embedded in micro-grid configurations.
Willingness to Pay and Public Acceptance for Hydrogen Buses: A Case Study of Perugia
Sep 2015
Publication
Sustainability transportation is characterized by a positive externality on the environment health social security land use and social inclusion. The increasing interest in global warming has caused attention to be paid to the introduction of the hydrogen bus (H2B). When introducing new environmental technologies such as H2B it is often necessary to assess the environmental benefits related to this new technology. However such benefits are typically non-priced due to their public good nature. Therefore we have to address this problem using the contingent valuation (CV) method. This method has been developed within environmental economics as a means to economically assess environmental changes which are typically not traded in the market. So far several big cities have been analyzed to evaluate the perceived benefit related to H2B introduction but to the best of our knowledge no one has performed a CV analysis of a historical city where smog also damages historical buildings. This paper presents the results obtained using a multi-wave survey. We have investigated user preferences to elicit their willingness to pay for H2B introduction in Perugia taking into account all types of negative externalities due to the traffic pollution. The results confirm that residents in Perugia are willing to pay extra to support the introduction of H2B.
Magnesium Based Materials for Hydrogen Based Energy Storage: Past, Present and Future
Jan 2019
Publication
Volodymyr A. Yartys,
Mykhaylo V. Lototskyy,
Etsuo Akiba,
Rene Albert,
V. E. Antonov,
Jose-Ramón Ares,
Marcello Baricco,
Natacha Bourgeois,
Craig Buckley,
José Bellosta von Colbe,
Jean-Claude Crivello,
Fermin Cuevas,
Roman V. Denys,
Martin Dornheim,
Michael Felderhoff,
David M. Grant,
Bjørn Christian Hauback,
Terry D. Humphries,
Isaac Jacob,
Petra E. de Jongh,
Jean-Marc Joubert,
Mikhail A. Kuzovnikov,
Michel Latroche,
Mark Paskevicius,
Luca Pasquini,
L. Popilevsky,
Vladimir M. Skripnyuk,
Eugene I. Rabkin,
M. Veronica Sofianos,
Alastair D. Stuart,
Gavin Walker,
Hui Wang,
Colin Webb,
Min Zhu and
Torben R. Jensen
Magnesium hydride owns the largest share of publications on solid materials for hydrogen storage. The “Magnesium group” of international experts contributing to IEA Task 32 “Hydrogen Based Energy Storage” recently published two review papers presenting the activities of the group focused on magnesium hydride based materials and on Mg based compounds for hydrogen and energy storage. This review article not only overviews the latest activities on both fundamental aspects of Mg-based hydrides and their applications but also presents a historic overview on the topic and outlines projected future developments. Particular attention is paid to the theoretical and experimental studies of Mg-H system at extreme pressures kinetics and thermodynamics of the systems based on MgH2 nanostructuring new Mg-based compounds and novel composites and catalysis in the Mg based H storage systems. Finally thermal energy storage and upscaled H storage systems accommodating MgH2 are presented.
Toward a Non-destructive Diagnostic Analysis Tool of Exercises Pipelines: Models and Experiences
Dec 2018
Publication
Strategic networks of hydrocarbon pipelines in long time service are adversely affected by the action of aggressive chemicals transported with the fluids and dissolved in the environment. Material degradation phenomena are amplified in the presence of hydrogen and water elements that increase the material brittleness and reduce the safety margins. The risk of failure during operation of these infrastructures can be reduced if not prevented by the continuous monitoring of the integrity of the pipe surfaces and by the tracking of the relevant bulk properties. A fast and potentially non-destructive diagnostic tool of material degradation which may be exploited in this context is based on the instrumented indentation tests that can be performed on metals at different scales. Preliminary validation studies of the significance of this methodology for the assessment of pipeline integrity have been carried out with the aid of interpretation models of the experiments. The main results of this ongoing activity are illustrated in this contribution.
Optimisation-based System Designs for Deep Offshore Wind Farms including Power to Gas Technologies
Feb 2022
Publication
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.
Evaluation of the Impact of Green Hydrogen Blending Scenarios in the Italian Gas Network: Optimal Design and Dynamic Simulation of Operation Strategies
Apr 2022
Publication
Blending hydrogen (H2) produced from PEM electrolysis coupled to Renewable Energy Sources (RES) in the existing Natural Gas (NG) network is a promising option for the deep decarbonization of the gas sector. However blending H2 with NG significantly affects the thermophysical properties of the gas mixture changing the gas supply requirements to meet the demand. In this work different scenarios of green hydrogen blending (Blend Ratio BR equal to 5/10/15/20%vol) are analyzed at the national level with different temporal constraints (hour/day/week/month/year) based on real gas demand data in Italy addressing both design requirements (RES and PEM electrolyzer capacity) via Linear Programming (LP) and carrying out dynamic simulations of different operational strategies (constant or variable blend). Although H2/NG blending provides a huge opportunity in terms of deployed H2 volume higher BRs show rapidly increasing design requirements (1.3-1.5 GWe/%vol and 2.5-3 GWe/%vol for PEM electrolyzers and RES capacity respectively) and a significative increase of the total gas mixture volume (0.83 %/%vol) which hinders the CO2 reduction potential (0.37 %/%vol). A variable blend operation strategy (allowing a variation of BR within the analyzed period) allows to balance a variable H2 production from RES. Wider temporal constraints imply several beneficial effects such as relaxing design constraints and avoiding the implementation of an external storage. The Levelized Cost Of Hydrogen (LCOH) is preliminarily estimated at around 7.3 $/kg for yearly scenarios (best-case) although shorter temporal constraints entail significant excess hydrogen which would increase the LCOH if not deployed for other applications.
Green Hydrogen in Europe – A Regional Assessment: Substituting Existing Production with Electrolysis Powered by Renewables
Nov 2020
Publication
The increasing ambition of climate targets creates a major role for hydrogen especially in achieving carbon-neutrality in sectors presently difficult to decarbonise. This work examines to what extent the currently carbon-intensive hydrogen production in Europe could be replaced by water electrolysis using electricity from renewable energy resources (RES) such as solar photovoltaic onshore/offshore wind and hydropower (green hydrogen). The study assesses the technical potential of RES at regional and national levels considering environmental constraints land use limitations and various techno-economic parameters. It estimates localised clean hydrogen production and examines the capacity to replace carbon-intensive hydrogen hubs with ones that use RES-based water electrolysis. Findings reveal that -at national level- the available RES electricity potential exceeds the total electricity demand and the part for hydrogen production from electrolysis in all analysed countries. At regional level from the 109 regions associated with hydrogen production (EU27 and UK) 88 regions (81%) show an excess of potential RES generation after covering the annual electricity demand across all sectors and hydrogen production. Notably 84 regions have over 50% excess RES electricity potential after covering the total electricity demand and that for water electrolysis. The study provides evidence on the option to decarbonize hydrogen production at regional level. It shows that such transformation is possible and compatible with the ongoing transition towards carbon–neutral power systems in the EU. Overall this work aims to serve as a tool for designing hydrogen strategies in harmony with renewable energy policies.
Methanol Steam Reforming for Hydrogen Generation Via Conventional and Membrane Reactors: A Review
Sep 2013
Publication
Variable renewable energy (VRE) is expected to play a major role in the decarbonization of the electricity sector. However decarbonization via VRE requires a fleet of flexible dispatchable plants with low CO2 emissions to supply clean power during times with limited wind and sunlight. These plants will need to operate at reduced capacity factors with frequent ramps in electricity output posing techno-economic challenges. This study therefore presents an economic assessment of a new near-zero emission power plant designed for this purpose. The gas switching reforming combined cycle (GSR-CC) plant can produce electricity during times of low VRE output and hydrogen during times of high VRE output. This product flexibility allows the plant to operate continuously even when high VRE output makes electricity production uneconomical. Although the CO2 avoidance cost of the GSR-CC plant (€61/ton) was similar to the benchmark post-combustion CO2 capture plant under baseload operation GSR-CC clearly outperformed the benchmark in a more realistic scenario where continued VRE expansion forces power plants into mid-load operation (45% capacity factor). In this scenario GSR-CC promises a 5 %-point higher annualized investment return than the post-combustion benchmark. GSR-CC therefore appears to be a promising concept for a future scenario with high VRE market share and CO2 prices provided that a large market for clean hydrogen is established.
Hydrous Hydrazine Decomposition for Hydrogen Production Using of Ir/CeO2: Effect of Reaction Parameters on the Activity
May 2021
Publication
In the present work an Ir/CeO2 catalyst was prepared by the deposition–precipitation method and tested in the decomposition of hydrazine hydrate to hydrogen which is very important in the development of hydrogen storage materials for fuel cells. The catalyst was characterised using different techniques i.e. X-ray photoelectron spectroscopy (XPS) transmission electron microscopy (TEM) scanning electron microscopy (SEM) equipped with X-ray detector (EDX) and inductively coupled plasma—mass spectroscopy (ICP-MS). The effect of reaction conditions on the activity and selectivity of the material was evaluated in this study modifying parameters such as temperature the mass of the catalyst stirring speed and concentration of base in order to find the optimal conditions of reaction which allow performing the test in a kinetically limited regime.
Numerical Evaluation of the Effect of Fuel Blending with CO2 and H2 on the Very Early Corona‐Discharge Behavior in Spark Ignited Engines
Feb 2022
Publication
Reducing green‐house gases emission from light‐duty vehicles is compulsory in order to slow down the climate change. The application of High Frequency Ignition systems based on the Corona discharge effect has shown the potential to extend the dilution limit of engine operating conditions promoting lower temperatures and faster combustion events thus higher thermal and indicating efficiency. Furthermore predicting the behavior of Corona ignition devices against new sustainable fuel blends including renewable hydrogen and biogas is crucial in order to deal with the short‐intermediate term fleet electric transition. The numerical evaluation of Corona‐induced discharge radius and radical species under those conditions can be helpful in order to capture local effects that could be reached only with complex and expensive optical investigations. Using an ex‐ tended version of the Corona one‐dimensional code previously published by the present authors the simulation of pure methane and different methane–hydrogen blends and biogas–hydrogen blends mixed with air was performed. Each mixture was simulated both for 10% recirculated exhaust gas dilution and for its corresponding dilute upper limit which was estimated by means of chemical kinetics simulations integrated with a custom misfire detection criterion.
A Battery-Free Sustainable Powertrain Solution for Hydrogen Fuel Cell City Transit Bus Application
Apr 2022
Publication
The paper presents a sustainable electric powertrain for a transit city bus featuring an electrochemical battery-free power unit consisting of a hydrogen fuel cell stack and a kinetic energy storage system based on high-speed flywheels. A rare-earth free high-efficiency motor technology is adopted to pursue a more sustainable vehicle architecture by limiting the use of critical raw materials. A suitable dynamic energetic model of the full vehicle powertrain has been developed to investigate the feasibility of the traction system and the related energy management control strategy. The model includes losses characterisation as a function of the load of the main components of the powertrain by using experimental tests and literature data. The performance of the proposed solution is evaluated by simulating a vehicle mission on an urban path in real traffic conditions. Considerations about the effectiveness of the traction system are discussed.
Moving Gas Turbine Package from Conventional Gas to Hydrogen Blend
Sep 2021
Publication
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.
Lock-In Effects on the Energy Sector: Evidence from Hydrogen Patenting Activities
Apr 2022
Publication
The aim of the paper is to analyze how regulatory design and its framework’s topics other than macroeconomic factors might impact green innovation by taking into consideration a brand-new renewable source of energy that is becoming more and more important in recent years: hydrogen and fuel cell patenting activities. Such activities have been used as a proxy for green technological change in a panel data of 52 countries over a 6-year period. A series of sectorial energy regulation and macroeconomic variables were tested to assess their impact on that technological frontier of green energy transition policy. As might have been expected the empirical analysis carried out with the model that was prefigured confirms significant evidence of lock-in effects on fossil fuel policies. The model confirms however another evidence: countries already investing in renewables might be willing to invest in hydrogen projects. A sort of reinforcement to the further development of green sustainable strategies seems to derive from having already concretely undertaken this direction. Future research should exploit different approaches to the research question and address the econometric criticalities mentioned in the paper along with exploiting results of the paper with further investigations.
Improved Hydrogen-Production-Based Power Management Control of a Wind Turbine Conversion System Coupled with Multistack Proton Exchange Membrane Electrolyzers
Mar 2020
Publication
This paper deals with two main issues regarding the specific energy consumption in an electrolyzer (i.e. the Faraday efficiency and the converter topology). The first aspect is addressed using a multistack configuration of proton exchange membrane (PEM) electrolyzers supplied by a wind turbine conversion system (WTCS). This approach is based on the modeling of the wind turbine and the electrolyzers. The WTCS and the electrolyzers are interfaced through a stacked interleaved DC–DC buck converter (SIBC) due to its benefits for this application in terms of the output current ripple and reliability. This converter is controlled so that it can offer dynamic behavior that is faster than the wind turbine avoiding overvoltage during transients which could damage the PEM electrolyzers. The SIBC is designed to be connected in array configuration (i.e. parallel architecture) so that each converter operates at its maximum efficiency. To assess the performance of the power management strategy experimental tests were carried out. The reported results demonstrate the correct behavior of the system during transient operation.
Multi-Objective Optimization of a Hydrogen Hub for the Decarbonization of a Port Industrial Area
Feb 2022
Publication
Green hydrogen is addressed as a promising solution to decarbonize industrial and mobility sectors. In this context ports could play a key role not only as hydrogen users but also as suppliers for industrial plants with which they have strong commercial ties. The implementation of hydrogen technologies in ports has started to be addressed as a strategy for renewable energy transition but still requires a detailed evaluation of the involved costs which cannot be separated from the correct design and operation of the plant. Hence this study proposes the design and operation optimization of a hydrogen production and storage system in a typical Italian port. Multi-objective optimization is performed to determine the optimal levelized cost of hydrogen in environmental and techno-economic terms. A Polymer Electrolyte Membrane (PEM) electrolyzer powered by a grid-integrated photovoltaic (PV) plant a compression station and two-pressure level storage systems are chosen to provide hydrogen to a hydrogen refueling station for a 20-car fleet and satisfy the demand of the hydrogen batch annealing in a steel plant. The results report that a 341 kWP PV plant 89 kW electrolyzer and 17 kg hydrogen storage could provide hydrogen at 7.80 €/kgH2 potentially avoiding about 153 tCO2eq/year (120 tCO2eq/year only for the steel plant).
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