Norway
Pathways to Low-cost Clean Hydrogen Production with Gas Switching Reforming
Feb 2020
Publication
Gas switching reforming (GSR) is a promising technology for natural gas reforming with inherent CO2 capture. Like conventional steam methane reforming (SMR) GSR can be integrated with CO2 -gas shift and pressure swing adsorption units for pure hydrogen production. The resulting GSR-H2 process concept was techno-economically assessed in this study. Results showed that GSR-H2 can achieve 96% CO2 capture at a CO2 avoidance cost of 15 $/ton (including CO2 transport and storage). Most components of the GSR-H2 process are proven technologies but long-term oxygen carrier stability presents an important technical uncertainty that can adversely affect competitiveness when the material lifetime drops below one year. Relative to the SMR benchmark GSR-H2 replaces some fuel consumption with electricity consumption making it more suitable to regions with higher natural gas prices and lower electricity prices. Some minor alterations to the process configuration can adjust the balance between fuel and electricity consumption to match local market conditions. The most attractive commercialization pathway for the GSR-H2 technology is initial construction without CO2 capture followed by simple retrofitting for CO2 capture when CO2 taxes rise and CO2 transport and storage infrastructure becomes available. These features make the GSR-H2 technology robust to almost any future energy market scenario.
3D Risk Management for Hydrogen Installations (HY3DRM)
Oct 2015
Publication
This paper introduces the 3D risk management (3DRM) concept with particular emphasis on hydrogen installations (Hy3DRM). The 3DRM framework entails an integrated solution for risk management that combines a detailed site-specific 3D geometry model a computational fluid dynamics (CFD) tool for simulating flow-related accident scenarios methodology for frequency analysis and quantitative risk assessment (QRA) and state-of-the-art visualization techniques for risk communication and decision support. In order to reduce calculation time and to cover escalating accident scenarios involving structural collapse and projectiles the CFD-based consequence analysis can be complemented with empirical engineering models reduced order models or finite element analysis (FEA). The paper outlines the background for 3DRM and presents a proof-of-concept risk assessment for a hypothetical hydrogen filling station. The prototype focuses on dispersion fire and explosion scenarios resulting from loss of containment of gaseous hydrogen. The approach adopted here combines consequence assessments obtained with the CFD tool FLACS-Hydrogen from Gexcon and event frequencies estimated with the Hydrogen Risk Assessment Models (HyRAM) tool from Sandia to generate 3D risk contours for explosion pressure and radiation loads. For a given population density and set of harm criteria it is straightforward to extend the analysis to include personnel risk as well as risk-based design such as detector optimization. The discussion outlines main challenges and inherent limitations of the 3DRM concept as well as prospects for further development towards a fully integrated framework for risk management in organizations.
Effect of Anion Exchange Ionomer Content on Electrode Performance in AEM Water Electrolysis
Aug 2020
Publication
Anion exchange membrane water electrolysis (AEMWE) has acquired substantial consideration as a cost-effective hydrogen production technology. The anion ionomer content in the catalyst layers during hydrogen and oxygen evolution reaction (HER and OER) is of ultimate significance. Herein an in-situ half-cell analysis with reference electrodes was carried out for simultaneous potential measurements and identification of the influence of the anion exchange ionomer (AEI) content on anode and cathode performance. The measured half-cell potentials proved the influence of AEI content on the catalytic activity of HER and OER which was supported by the rotating disk electrode (RDE) measurements. Cathode overpotential of Ni/C was not negligible and more affected by the AEI content than anode with the optimized AEI content of 10 wt% while NiO anode OER overpotential was independent of the AEI content. For the same AEI content PGM catalysts showed higher electroactivity than Ni-based catalysts for HER and OER and the cathode catalyst's intrinsic activity is of high importance in the AEM electrolysis operation. Post-mortem analysis by SEM mapping of both AEI and catalyst distributions on the electrode surface showed the effect of AEI loading on the catalyst morphology which could be related to the electrode performance.
Modelling and Simulation of a Zero-emission Hybrid Power Plant for a Domestic Ferry
Jan 2021
Publication
This paper presents a simulation tool for marine hybrid power-plants equipped with polymer exchange membrane fuel cells and batteries. The virtual model through the combination of operational data and dynamically modelled subsystems can simulate power-plants of different sizes and configurations in order to analyze the response of different energy management strategies. The model aims to replicate the realistic behavior of the components included in the vessel's grid to asses if the hardware selected by the user is capable of delivering the power set-point requested by the energy management system. The model can then be used to optimize key factors such as hydrogen consumption. The case study presented in the paper demonstrates how the model can be used for the evaluation of a retrofitting operation replacing a diesel electric power-plant with fuel cells and batteries. The vessel taken into consideration is a domestic ferry operating car and passenger transport in Denmark. The vessel is outfitted with a diesel electric plant and an alternative hybrid power-plant is proposed. The hybrid configuration is tested using the model in a discrete time-domain.
Hydrogen as a Maritime Fuel–Can Experiences with LNG Be Transferred to Hydrogen Systems?
Jul 2021
Publication
As the use of fossil fuels becomes more and more restricted there is a need for alternative fuels also at sea. For short sea distance travel purposes batteries may be a solution. However for longer distances when there is no possibility of recharging at sea batteries do not have sufficient capacity yet. Several projects have demonstrated the use of compressed hydrogen (CH2) as a fuel for road transport. The experience with hydrogen as a maritime fuel is very limited. In this paper the similarities and differences between liquefied hydrogen (LH2) and liquefied natural gas (LNG) as a maritime fuel will be discussed based on literature data of their properties and our system knowledge. The advantages and disadvantages of the two fuels will be examined with respect to use as a maritime fuel. Our objective is to discuss if and how hydrogen could replace fossil fuels on long distance sea voyages. Due to the low temperature of LH2 and wide flammability range in air these systems have more challenges related to storage and processing onboard than LNG. These factors result in higher investment costs. All this may also imply challenges for the LH2 supply chain.
Loss of Integrity of Hydrogen Technologies: A Critical Review
Jul 2020
Publication
Hydrogen is one of the main candidates in replacing fossil fuels in the forthcoming years. However hydrogen technologies must deal with safety aspects due to the specific substance properties. This study aims to provide an overview on the loss of integrity (LOI) of hydrogen equipment which may lead to serious consequences such as fires and explosions. Substantial information regarding the hydrogen lifecycle its properties and safety related aspects has gathered. Furthermore focus has placed on the phenomena responsible for the LOI (e.g. hydrogen embrittlement) and material selection for hydrogen services. Moreover a systematic review on the hydrogen LOI topic has conducted to identify and connect the most relevant and active research group within the topic. In conclusion a significant dearth of knowledge in material behaviour of hydrogen technologies has highlighted. It is thought that is possible to bridge this gap by strengthening the collaborations between scientists from different research fields.
Residual Performance of Composite Pressure Vessels Submitted to Mechanical Impacts
Sep 2017
Publication
Type IV pressure vessels are commonly used for hydrogen on-board stationary or bulk storages. During their lifetime they can be submitted to mechanical impacts creating damage within the composite structure not necessarily correlated to what is visible from the outside. When an impact is suspected or when a cylinder is periodically inspected it is necessary to determine whether it can safely stay in service or not. The FCH JU project Hypactor aims at creating a large database of impacts characterized by various non destructive testing (NDT) methods in order to provide reliable pass-fail criteria for damaged cylinders. This paper presents some of the tests results investigating short term burst) and long term (cycling) performance of impacted cylinders and the recommendations that can be made for impact testing and NDT criteria calibration.
Minimum Entropy Generation in a Heat Exchanger in the Cryogenic Part of the Hydrogen Liquefaction Process: On the Validity of Equipartition and Disappearance of the Highway
May 2019
Publication
Liquefaction of hydrogen is a promising technology for transporting large quantities of hydrogen across long distances. A key challenge is the high power consumption. In this work we discuss refrigeration strategies that give minimum entropy production/exergy destruction in a plate-fin heat exchanger that cools the hydrogen from 47.8 K to 29.3 K. Two reference cases are studied; one where the feed stream enters at 20 bar and one where it enters at 80 bar. Catalyst in the hot layers speeds up the conversion of ortho-to para-hydrogen. Optimal control theory is used to formulate a minimization problem where the objective function is the total entropy production the control variable is the temperature of the refrigerant and the constrains are the balance equations for energy mass and momentum in the hot layers. The optimal refrigeration strategies give a reduction of the total entropy production of 8.7% in the 20-bar case and 4.3% in the 80-bar case. The overall heat transfer coefficient and duty is higher in the 20 bar case which compensates for the increase in entropy production due to a thermal mismatch that is avoided in the 80 bar case. This leads the second law efficiency of the 20 bar case (91%) to be similar to the 80 bar case (89%). We demonstrate that equipartition of the entropy production and equipartition of the thermal driving force are both excellent design principles for the process unit considered with total entropy productions deviating only 0.2% and 0.5% from the state of minimum entropy production. Equipartition of the thermal driving force i.e. a constant difference between the inverse temperatures of the hot and cold layers represents a particularly simple guideline that works remarkably well. We find that both heat transfer and the spin-isomer reaction contribute significantly to the entropy production throughout the length of the process unit. Unlike previous examples in the literature the process unit considered in this work is not characterized by a “reaction mode” at the inlet followed by a “heat transfer mode”. Therefore it does not follow a highway in state space i.e. a band that is particularly dense with energy efficient solutions. By artificially increasing the spin-isomer conversion rate the highway appears when the conversion rate becomes sufficiently high.
Flexible Power and Hydrogen Production: Finding Synergy Between CCS and Variable Renewables
Dec 2019
Publication
The expansion of wind and solar power is creating a growing need for power system flexibility. Dispatchable power plants with CO2 capture and storage (CCS) offer flexibility with low CO2 emissions but these plants become uneconomical at the low running hours implied by renewables-based power systems. To address this challenge the novel gas switching reforming (GSR) plant was recently proposed. GSR can alternate between electricity and hydrogen production from natural gas offering flexibility to the power system without reducing the utilization rate of the capital stock embodied in CCS infrastructure. This study assesses the interplay between GSR and variable renewables using a power system model which optimizes investment and hourly dispatch of 13 different technologies. Results show that GSR brings substantial benefits relative to conventional CCS. At a CO2 price of V100/ton inclusion of GSR increases the optimal wind and solar share by 50% lowers total system costs by 8% and reduces system emissions from 45 to 4 kgCO2/MWh. In addition GSR produces clean hydrogen equivalent to about 90% of total electricity demand which can be used to decarbonize transport and industry. GSR could therefore become a key enabling technology for a decarbonization effort led by wind and solar power.
Efficient Hydrogen Production with CO2 Capture Using Gas Switching Reforming
Jul 2019
Publication
Hydrogen is a promising carbon-neutral energy carrier for a future decarbonized energy sector. This work presents process simulation studies of the gas switching reforming (GSR) process for hydrogen production with integrated CO2 capture (GSR-H2 process) at a minimal energy penalty. Like the conventional steam methane reforming (SMR) process GSR combusts the off-gas fuel from the pressure swing adsorption unit to supply heat to the endothermic reforming reactions. However GSR completes this combustion using the chemical looping combustion mechanism to achieve fuel combustion with CO2 separation. For this reason the GSR-H2 plant incurred an energy penalty of only 3.8 %-points relative to the conventional SMR process with 96% CO2 capture. Further studies showed that the efficiency penalty is reduced to 0.3 %-points by including additional thermal mass in the reactor to maintain a higher reforming temperature thereby facilitating a lower steam to carbon ratio. GSR reactors are standalone bubbling fluidized beds that will be relatively easy to scale up and operate under pressurized conditions and the rest of the process layout uses commercially available technologies. The ability to produce clean hydrogen with no energy penalty combined with this inherent scalability makes the GSR-H2 plant a promising candidate for further research.
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.
Development of Tools for Risk Assessment and Risk Communication for Hydrogen Applications
Sep 2005
Publication
For decades risk assessment has been an important tool in risk management of activities in several industries world wide. It provides among others authorities and stakeholders with a sound basis for creating awareness about existing and potential hazards and risks and making decisions related to how they can prioritise and plan expenditures on risk reduction. The overall goal of the ongoing HySafe project is to contribute to the safe transition to a more sustainable development in Europe by facilitating the safe introduction of hydrogen technologies and applications. An essential element in this is the demonstration of safety: that all safety aspects related to production transportation and public use are controlled to avoid that introducing hydrogen as energy carrier should pose unacceptable risk to the society.<br/>History has proven that introducing risk analysis to new industries is beneficial e.g. in transportation and power production and distribution. However this will require existing methods and standards to be adapted to the specific applications. Furthermore when trying to quantify risk it is of utmost importance to have access to relevant accident and incident information. Such data may in many cases not be readily available and the utilisation of them will then require specific and long lasting data collection initiatives.<br/>In this paper we will present the work that has been undertaken in the HySafe project in developing methodologies and collecting data for risk management of hydrogen infrastructure. Focus is laid on the development of risk acceptance criteria and on the demonstration of safety and benefits to the public. A trustworthy demonstration of safety will have to be based on facts especially on facts widely known and emphasis will thus be put on the efforts taken to establish and operate a database containing hydrogen accident and incident information which can be utilised in risk assessment of hydrogen applications. A demonstration of safety will also have to include a demonstration of risk control measures and the paper will also present work carried out on safety distances and ignition source control.
Stress Corrosion Cracking Of Stainless Steels In High Pressure Alkaline Electrolysers
Sep 2005
Publication
Hydrogen-producing high-pressure electrolysers operating with 40% potassium hydroxide solution and an applied oxygen pressure up to 30 barg have been developed. Austenitic stainless steels of type AISI316L are deemed resistant to stress corrosion cracking (SCC) in concentrated KOH solutions. However SCC has on some occasions been observed on the oxygen side of the high-pressure electrolysers thereby representing a safety risk in the operation. Several materials have been tested for resistance to SCC using C-ring specimens in autoclaves under conditions similar to the high-pressure electrolysers and at temperatures up to 120°C. The tests confirmed the observed susceptibility of austenitic stainless steels to SCC in concentrated KOH solutions. Higher alloyed austenitic stainless steels also showed SCC. Duplex stainless steel and nickel based Alloy 28 showed good resistance to SCC in the given environment. Further tests are needed to define the optimum weld procedure.
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.
Simulation of Flame Acceleration and DDT in H2-air Mixture with a Flux Limiter Centred Method
Sep 2005
Publication
Flame acceleration and deflagration to detonation transition (DDT) is simulated with a numerical code based on a flux limiter centred method for hyperbolic differential equations. The energy source term is calculated by a Riemann solver for the in homogeneous Euler equations for the turbulent combustion and a two-step reaction model for hydrogen-air. The transport equations are filtered for large eddy simulation (LES) and the sub filter turbulence is modelled by a transport equation for the the turbulent kinetic energy. The flame tracking is handled by the G-equation for turbulent flames. Numerical results are compared to pressure histories from physical experiments. These experiments are performed in a closed circular 4m long tube with inner diameter of 0.107m. The tube is filled with hydrogen-air mixture at 1atm which is at rest when ignited. The ignition is located at one end of the tube. The tube is fitted with an obstruction with circular opening 1m down the tube from the ignition point. The obstruction has a blockage ratio of 0.92 and a thickness of 0.01m. The obstruction creates high pressures in the ignition end of the tube and very high gas velocities in and behind the obstruction opening. The flame experiences a detonation to deflagration transition (DDT) in the super sonic jet created by the obstruction. Pressure build-up in the ignition end of the tube is simulated with some discrepancies. The DDT in the supersonic jet is simulated but the position of the DDT is strongly dependent on the simulated pressure in the ignition end.
Assessment and Evaluation of 3rd Party Risk for Planned Hydrogen Demonstration Facility
Sep 2007
Publication
Potential risk exposure of 3rd parties i.e. people not involved in the actual operation of a plant is often a critical factor to gain authority approval and public acceptance for a development project. This is also highly relevant for development of demonstration facilities for hydrogen production and refuelling infrastructure. This paper presents and discusses results for risk exposure of 3rd parties based on risk assessment studies performed for the planned Hydrogen Technology Research Centre Hytrec in Trondheim. The methodology applied is outlined. Key assumptions and study uncertainties are identified and how these might affect the results are discussed.<br/>The purpose of Hytrec is to build a centre for research development and demonstration of hydrogen as an energy carrier. Hydrogen will be produced both by reforming of natural gas with CO2 capture and by electrolysis of water. The plant also includes a SOFC that will run on natural gas or hydrogen and produce heat and electricity for the Hytrec visitor centre. Hytrec will be located in a populated area without access control. Most of the units will be located within cabinets and modules.<br/>The authors acknowledge the Hytrec project and the Hytrec project partners Statoil Statkraft and DNV for their support and for allowing utilisation of results from the Hytrec QRA in this paper.
The Potential of Gas Switching Partial Oxidation Using Advanced Oxygen Carriers for Efficient H2 Production with Inherent CO2 Capture
May 2021
Publication
The hydrogen economy has received resurging interest in recent years as more countries commit to net-zero CO2 emissions around the mid-century. “Blue” hydrogen from natural gas with CO2 capture and storage (CCS) is one promising sustainable hydrogen supply option. Although conventional CO2 capture imposes a large energy penalty advanced process concepts using the chemical looping principle can produce blue hydrogen at efficiencies even exceeding the conventional steam methane reforming (SMR) process without CCS. One such configuration is gas switching reforming (GSR) which uses a Ni-based oxygen carrier material to catalyze the SMR reaction and efficiently supply the required process heat by combusting an off-gas fuel with integrated CO2 capture. The present study investigates the potential of advanced La-Fe-based oxygen carrier materials to further increase this advantage using a gas switching partial oxidation (GSPOX) process. These materials can overcome the equilibrium limitations facing conventional catalytic SMR and achieve direct hydrogen production using a water-splitting reaction. Results showed that the GSPOX process can achieve mild efficiency improvements relative to GSR in the range of 0.6–4.1%-points with the upper bound only achievable by large power and H2 co-production plants employing a highly efficient power cycle. These performance gains and the avoidance of toxicity challenges posed by Ni-based oxygen carriers create a solid case for the further development of these advanced materials. If successful results from this work indicate that GSPOX blue hydrogen plants can outperform an SMR benchmark with conventional CO2 capture by more than 10%-points both in terms of efficiency and CO2 avoidance.
Pathway to Net Zero Emissions
Oct 2021
Publication
A feasible path to limit planetary warming to 1.5°C requires certain countries and sectors to go below net zero and to do so well before the middle of the century according to new analysis from the authors of the Energy Transition Outlook. DNV’s pathway to net zero says North America and Europe must be carbon neutral by 2042 whereas Indian Subcontinent is set to be a net emitter by 2050 Net zero report says carbon capture storage and use is required as energy production will not be carbon neutral by 2050 Aim to halve emissions by 2030 is out of reach but massive early action is needed if we are to have any chance of reaching a 1.5°C future DNV’s new report “Pathway to Net Zero Emissions” describes a feasible way to limit global warming to 1.5°C Policy makers are set to meet in Glasgow for the COP 26 summit with an eye on achieving zero emissions by 2050. For this to happen North America and Europe must be carbon neutral by 2042 and then carbon negative thereafter according to DNV’s pathway to net zero. The pathway also finds that Greater China must reduce emissions by 98% from 2019 levels by 2050. There are regions that cannot realistically transition completely away from fossil fuels in the same timeframe such as the Indian Subcontinent which will reduce emissions by 64%. Pathway to Net Zero Emissions also lays out the pace at which different industry sectors need to decarbonize. The so-called hard-to-abate sectors will take longer to decarbonize and even if sectors like maritime (-90% CO2 emissions in 2050) and iron and steel production (-82%) scale up the introduction of greener technologies they will still be net emitters by 2050.
A Review on the Properties of Iron Aluminide Intermetallics
Jan 2016
Publication
Iron aluminides have been among the most studied intermetallics since the 1930s when their excellent oxidation resistance was first noticed. Their low cost of production low density high strength-to-weight ratios good wear resistance ease of fabrication and resistance to high temperature oxidation and sulfurization make them very attractive as a substitute for routine stainless steel in industrial applications. Furthermore iron aluminides allow for the conservation of less accessible and expensive elements such as nickel and molybdenum. These advantages have led to the consideration of many applications such as brake disks for windmills and trucks filtration systems in refineries and fossil power plants transfer rolls for hot-rolled steel strips and ethylene crackers and air deflectors for burning high-sulfur coal. A wide application for iron aluminides in industry strictly depends on the fundamental understanding of the influence of (i) alloy composition; (ii) microstructure; and (iii) number (type) of defects on the thermo-mechanical properties. Additionally environmental degradation of the alloys consisting of hydrogen embrittlement anodic or cathodic dissolution localized corrosion and oxidation resistance in different environments should be well known. Recently some progress in the development of new micro- and nano-mechanical testing methods in addition to the fabrication techniques of micro- and nano-scaled samples has enabled scientists to resolve more clearly the effects of alloying elements environmental items and crystal structure on the deformation behavior of alloys. In this paper we will review the extensive work which has been done during the last decades to address each of the points mentioned above.
Heat to Hydrogen by RED—Reviewing Membranes and Salts for the RED Heat Engine Concept
Dec 2021
Publication
The Reverse electrodialysis heat engine (REDHE) combines a reverse electrodialysis stack for power generation with a thermal regeneration unit to restore the concentration difference of the salt solutions. Current approaches for converting low-temperature waste heat to electricity with REDHE have not yielded conversion efficiencies and profits that would allow for the industrialization of the technology. This review explores the concept of Heat-to-Hydrogen with REDHEs and maps crucial developments toward industrialization. We discuss current advances in membrane development that are vital for the breakthrough of the RED Heat Engine. In addition the choice of salt is a crucial factor that has not received enough attention in the field. Based on ion properties relevant for both the transport through IEMs and the feasibility for regeneration we pinpoint the most promising salts for use in REDHE which we find to be KNO3 LiNO3 LiBr and LiCl. To further validate these results and compare the system performance with different salts there is a demand for a comprehensive thermodynamic model of the REDHE that considers all its units. Guided by such a model experimental studies can be designed to utilize the most favorable process conditions (e.g. salt solutions).
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.
A Review of Cohesive Zone Modelling as an Approach for Numerically Assessing Hydrogen Embrittlement of Steel Structures
Jun 2014
Publication
Simulation of hydrogen embrittlement (HE) requires a coupled approach; on one side the models describing hydrogen transport must account for local mechanical fields while on the other side the effect of hydrogen on the accelerated material damage must be implemented into the model describing crack initiation and growth. This study presents a review of coupled diffusion and cohesive zone modelling as a method for numerically assessing HE of a steel structure. While the model is able to reproduce single experimental results by appropriate fitting of the cohesive parameters there appears to be limitations in transferring these results to other hydrogen systems. Agreement may be improved by appropriately identifying the required input parameters for the particular system under study.
Link to document download on Royal Society Website
Link to document download on Royal Society Website
Decarbonization Synergies From Joint Planning of Electricity and Hydrogen Production: A Texas Case Study
Oct 2020
Publication
Hydrogen (H2) shows promise as an energy carrier in contributing to emissions reductions from sectors which have been difficult to decarbonize like industry and transportation. At the same time flexible H2 production via electrolysis can also support cost-effective integration of high shares of variable renewable energy (VRE) in the power system. In this work we develop a least-cost investment planning model to co-optimize investments in electricity and H2 infrastructure to serve electricity and H2 demands under various low-carbon scenarios. Applying the model to a case study of Texas in 2050 we find that H2 is produced in approximately equal amounts from electricity and natural gas under the least-cost expansion plan with a CO2 price of $30–60/tonne. An increasing CO2 price favors electrolysis while increasing H2 demand favors H2 production from Steam Methane Reforming (SMR) of natural gas. H2 production is found to be a cost effective solution to reduce emissions in the electric power system as it provides flexibility otherwise provided by natural gas power plants and enables high shares of VRE with less battery storage. Additionally the availability of flexible electricity demand via electrolysis makes carbon capture and storage (CCS) deployment for SMR cost-effective at lower CO2 prices ($90/tonne CO2) than for power generation ($180/tonne CO2 ). The total emissions attributable to H2 production is found to be dependent on the H2 demand. The marginal emissions from H2 production increase with the H2 demand for CO2 prices less than $90/tonne CO2 due to shift in supply from electrolysis to SMR. For a CO2 price of $60/tonne we estimate the production weighted-average H2 price to be between $1.30–1.66/kg across three H2 demand scenarios. These findings indicate the importance of joint planning of electricity and H2 infrastructure for cost-effective energy system decarbonization.
Concept of Hydrogen Fired Gas Turbine Cycle with Exhaust Gas Recirculation: Assessment of Process Performance
Nov 2019
Publication
High hydrogen content fuels can be used in gas turbine for power generation with CO2 capture IGCC plants or with hydrogen from renewables. The challenge for the engine is the high reactive combustion properties making dilution necessary to mitigate NOx emissions at the expense of a significant energy cost. In the concept analysed in this study high Exhaust Gas Recirculation (EGR) rate is applied to the gas turbine to generate oxygen depleted air. As a result combustion temperature is inherently limited keeping NOx emissions low without the need for dilution or unsafe premixing. The concept is analysed by process simulation based on a reference IGCC plant with CO2 Capture. Results with dry and wet EGR options are presented as a function EGR rate. Efficiency performance is assessed against the reference power cycle with nitrogen dilution. All EGR options are shown to represent an efficiency improvement. Nitrogen dilution is found to have a 1.3% efficiency cost. Although all EGR options investigated offer an improvement dry EGR is considered as the preferred option despite the need for higher EGR rate as compared with the wet EGR. The efficiency gain is calculated to be of 1% compared with the reference case.
Experimental Study of Light Gas Dispersion in a Channel
Sep 2019
Publication
Usage of hydrogen as fuel gives rise to possible accidental risks due to leakage and dispersion. A risk from hydrogen leak is the formation of a large volume of the hydrogen-air mixture which could be ignited and leading up to a severe explosion. Prevention and control of formation and ignition of combustible hydrogen cloud necessitate sufficient knowledge of mechanisms of the hydrogen leak dispersion ignition and over-pressures generated during combustion. This paper aims to investigate the momentum-controlled jet the buoyancy-controlled wave and the parameters influencing hydrogen concentration distribution in an elongated space. It demonstrates experimental results and analysis from helium and hydrogen dispersion in a channel. A set of experiments were carried out for the release of helium and hydrogen jets in a 3 m long channel to record their concentrations in the cloud by concentration sensors at different horizontal and vertical positions. Flow visualization technique was applied using shadowgraph to image the mixing process next to the release point and the helium- hydrogen-air cloud shape at the middle of the channel. Moreover results were used for comparison of helium and hydrogen concentration gradients. The results of the experiments show that swift mixing occurs at higher flow rates smaller nozzle sizes and downward release direction. Higher concentration recorded in the channel with negative inclination. Results also confirmed that hydrogen/helium behavior pattern in the channel accords with mutual intrusion theory about gravity currents.
Pressure Peaking Phenomena: Unignited Hydrogen Releases in Confined Spaces – Large-scale Experiments
Sep 2020
Publication
The aim of this study was to validate a model for predicting overpressure arising from accidental hydrogen releases in areas with limited ventilation. Experiments were performed in a large-scale setup that included a steel-reinforced container of volume 14.9 m3 and variable ventilation areas and mass flow rates. The pressure peaking phenomenon characterized as transient overpressure with a characteristic peak in a vented enclosure was observed during all the experiments. The model description presented the relationship between the ventilation area mass flow rate enclosure volume and discharge coefficient. The experimental results were compared with two prediction models representing a perfect mix and the real mix. The perfect mix assumed that all the released hydrogen was well stirred inside the enclosure during the releases. The real mix prediction s used the hydrogen concentration and temperature data measured during experiments. The prediction results with both perfect mix and real mix showed possible hazards during unignited hydrogen releases.
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.
Large Scale Experiments and Model Validation of Pressure Peaking Phenomena-ignited Hydrogen Releases
Jan 2021
Publication
The Pressure Peaking Phenomena (PPP) is the effect of introducing a light gas into a vented volume of denser gas. This will result in a nonequilibrium pressure as the light gas pushes the dense gas out at the vent. Large scale experiments have been performed to produce relevant evidence. The results were used to validate an analytical model. Pressure and temperature were measured inside a constant volume while the mass flow and vent area were varied. The analytical model was based on the conservation of mass and energy. The results showed that increasing the mass flow rate the peak pressure increases and with increasing the ventilation area the peak pressure decreases. Peak pressure was measured above 45 kPa. Longer combustion time resulted in higher temperatures increasing an underpressure effect. The experimental results showed agreement with the analytical model results. The model predicts the pressures within reasonable limits of+/-2 kPa. The pressure peaking phenomena could be very relevant for hydrogen applications in enclosures with limited ventilation. This could include car garages ship hull compartments as well as compressor shielding. This work shows that the effect can be modeled and results can be used in design to reduce the consequences.
Mathematical Modeling and Simulation of Hydrogen-fueled Solid Oxide Fuel Cell System for Micro-grid Applications - Effect of Failure and Degradation on Transient Performance
May 2020
Publication
We use a detailed solid oxide fuel cell (SOFC) model for micro-grid applications to analyze the effect of failure and degradation on system performance. Design and operational constraints on a component and system level are presented. A degrees of freedom analysis identifies controlled and manipulated system variables which are important for control. Experimental data are included to model complex degradation phenomena of the SOFC unit. Rather than using a constant value a spatially distributed degradation rate as function of temperature and current density is used that allows to study trajectory based performance deterioration. The SOFC unit is assumed to consist of multiple stacks. The failure scenario studied is the loss of one individual SOFC stack e.g. due to breakage of sealing or a series of fuel cells. Simulations reveal that degradation leads to significant drifts from the design operating point. Moreover failure of individual stacks may bring the still operating power generation unit into a regime where further failures and accelerated degradation is more likely. It is shown that system design dimensioning operation and control are strongly linked. Apart from specific quantitative results perhaps the main practical contribution are the collected constraints and the degrees of freedom analysis.
On Capital Utilization in the Hydrogen Economy: The Quest to Minimize Idle Capacity in Renewables-rich Energy Systems
Oct 2020
Publication
The hydrogen economy is currently experiencing a surge in attention partly due to the possibility of absorbing variable renewable energy (VRE) production peaks through electrolysis. A fundamental challenge with this approach is low utilization rates of various parts of the integrated electricity-hydrogen system. To assess the importance of capacity utilization this paper introduces a novel stylized numerical energy system model incorporating the major elements of electricity and hydrogen generation transmission and storage including both “green” hydrogen from electrolysis and “blue” hydrogen from natural gas reforming with CO2 capture and storage (CCS). Concurrent optimization of all major system elements revealed that balancing VRE with electrolysis involves substantial additional costs beyond reduced electrolyzer capacity factors. Depending on the location of electrolyzers greater capital expenditures are also required for hydrogen pipelines and storage infrastructure (to handle intermittent hydrogen production) or electricity transmission networks (to transmit VRE peaks to electrolyzers). Blue hydrogen scenarios face similar constraints. High VRE shares impose low utilization rates of CO2 capture transport and storage infrastructure for conventional CCS and of hydrogen transmission and storage infrastructure for a novel process (gas switching reforming) that enables flexible power and hydrogen production. In conclusion all major system elements must be considered to accurately reflect the costs of using hydrogen to integrate higher VRE shares.
The Case for High-pressure PEM Water Electrolysis
Apr 2022
Publication
Hydrogen compression is a key part of the green hydrogen supply chain but mechanical compressors are prone to failure and add system complexity and cost. High-pressure water electrolysis can alleviate this problem through electrochemical compression of the gas internally in the electrolyzer and thereby eliminating the need for an external hydrogen compressor. In this work a detailed techno-economic assessment of high-pressure proton exchange membrane-based water electrolysis (PEMEL) systems was carried out. Electrolyzers operating at 80 200 350 and 700 bar were compared to state-of-the-art systems operating at 30 bar in combination with a mechanical compressor. The results show that it is possible to achieve economically viable solutions with high-pressure PEMEL-systems operating up to 200 bar. These pressure levels fit well with the requirements in existing and future industrial applications such as e-fuel production (30–120 bar) injection of hydrogen into natural gas grids (70 bar) hydrogen gas storage (≥200 bar) and ammonia production (200–300 bar). A sensitivity analysis also showed that if the cost of electricity is sufficiently low (
Features of the Hydrogen-Assisted Cracking Mechanism in the Low-Carbon Steel at Ex- and In-situ Hydrogen Charging
Dec 2018
Publication
Hydrogen embrittlement has been intensively studied in the past. However its governing mechanism is still under debate. Particularly the details of the formation of specific cleavage-like or quasi-cleavage fracture surfaces related to hydrogen embrittled steels are unclear yet. Recently it has been found that the fracture surface of the hydrogen charged and tensile tested low-carbon steel exhibits quasi-cleavage facets having specific smoothly curved surface which is completely different from common flat cleavage facets. In the present contribution we endeavor to shed light on the origin of such facets. For this purpose the notched flat specimens of the commercial low carbon steel were tensile tested using ex- and in-situ hydrogen charging. It is found that in the ex-situ hydrogen charged specimens the cracks originate primarily inside the specimen bulk and expand radially form the origin to the specimen surface. This process results in formation of “fisheyes” – the round-shape areas with the surface composed of curved quasi-cleavage facets. In contrast during tensile testing with in-situ hydrogen charging the cracks initiate from the surface and propagate to the bulk. This process results in the formation of the completely brittle fracture surface with the quasi-cleavage morphology - the same as that in fisheyes. The examination of the side surface of the in-situ hydrogen charged specimens revealed the straight and S-shaped sharp cracks which path is visually independent of the microstructure and crystallography but is strongly affected by the local stress fields. Nano-voids are readily found at the tips of these cracks. It is concluded that the growth of such cracks occurs by the nano-void coalescence mechanism and is responsible for the formation of fisheyes and smoothly curved quasi-cleavage facets in hydrogen charged low-carbon steel.
High-pressure PEM Water Electrolyser Performance Up to 180 Bar Differential Pressure
Feb 2024
Publication
Proton exchange membrane (PEM) electrolysers (PEMEL) are key for converting and storing excess renewable energy. PEMEL water electrolysis offers benefits over alkaline water electrolysers including a large dynamic range high responsiveness and high current densities and pressures. High operating pressures are important because it contributes to reduce the costs and energy-use related to downstream mechanical compression. In this work the performance of a high-pressure PEMEL system has been characterized up to 180 bar. The electrolyser stack has been characterized with respect to electrochemical performance net H2 production rate and water crossover and the operability and performance of the thermal- and gas management systems of the test bench has been assessed. The tests show that the voltage increase upon pressurization from 5 to 30 bar is 30 % smaller than expected but further pressurization reduces performance. The study confirms that highpressure PEMEL has higher energy consumption than state-of-the-art electrolyser systems with mechanical compressors. However there can be a business case for high-pressure PEMEL if the trade-off between stack efficiency and system efficiency is balanced.
Hydrogen Venting Under Variable Flow Conditions
Sep 2011
Publication
Safety distances for hydrogen plumes are currently derived using models developed for hydrocarbon releases. It is well known that hydrogen behaves in a significantly different manner to that of hydrocarbons when released to atmosphere. There are two main aspects involved with the development of safety distances for credible hydrogen releases; the intensity of the thermal radiation from such a plume should it be ignited and the distance downwind from the release point to the point where a flammable mixture with air no longer exists. A number of distinct areas of venting behaviour were investigated; Thermal radiation from ignited plumes from vertical open ended vent pipes Far field radiation measurements for direct comparison with models Thermal radiation from ignited plumes from vertical vent pipes terminating in a T-piece Thermal radiation measurements from ignited hydrogen with a 45 vent termination Hydrogen concentration measurements with a T-piece.
A Study of Hydrogen Flame Length with Complex Nozzle Geometry
Sep 2017
Publication
The growing number of hydrogen fillings stations and cars increases the need for accurate models to determine risk. The effect on hydrogen flame length was measured by varying the diameter of the spouting nozzle downstream from the chocked nozzle upstream. The results was compared with an existing model for flame length estimations. The experimental rig was setup with sensors that measured accurately temperature mass flow heat radiation and the pressure range from 0.1 to 11 MPa. The flame length was determined with an in-house developed image-processing tool which analyzed a high-speed film of the each experiment. Results show that the nozzle geometry can cause a deviation as high as 50% compared to estimated flame lengths by the model if wrong assumptions are made. Discharge coefficients for different nozzles has been calculated and presented.
Consequence Models for Vented Hydrogen Deflagrations: CFD vs. Engineering Models
Sep 2017
Publication
This paper compares two approaches for predicting the consequences of vented hydrogen deflagrations: empirical engineering models (EMs) and computational fluid dynamics (CFD) simulations. The study is part of the project ‘Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations’ (HySEA) funded by the Fuel Cells and Hydrogen 2 Joint Undertaking (FCH JU) under grant agreement No 671461. The HySEA project focuses on vented hydrogen deflagrations in containers and smaller enclosures with internal congestion representative of industrial applications. Data from experiments conducted as part of the HySEA project are used to evaluate predictions from a selection of EMs and the CFD tool FLACS. The experiments involve various obstacle and venting configurations and initially quiescent homogeneous hydrogen-air mixtures with hydrogen concentrations in the range 15–24 vol%. There is a significant scatter in the maximum reduced overpressures predicted by the different EMs in the present study. For certain configurations there is an order of magnitude difference between the different EM predictions. Two versions of the CFD tool FLACS are used in the present study: i) the standard commercial release FLACS v10.7r2 and ii) an in-house development version termed FLACS-beta. The commercial release generally over-predicts the maximum overpressures measured in the experiments while the development version of FLACS gives improved results for several configurations.
Implementing Maritime Battery-electric and Hydrogen Solutions: A Technological Innovation Systems Analysis
Sep 2020
Publication
Maritime transport faces increasing pressure to reduce its greenhouse gas emissions to be in accordance with the Paris Agreement. For this to happen low- and zero-carbon energy solutions need to be developed. In this paper we draw on sustainability transition literature and introduce the technological innovation system (TIS) framework to the field of maritime transportation research. The TIS approach analytically distinguishes between different innovation system functions that are important for new technologies to develop and diffuse beyond an early phase of experimentation. This provides a basis for technology-specific policy recommendations. We apply the TIS framework to the case of battery-electric and hydrogen energy solutions for coastal maritime transport in Norway. Whereas both battery-electric and hydrogen solutions have developed rapidly the former is more mature and has a strong momentum. Public procurement and other policy instruments have been crucial for developments to date and will be important for these technologies to become viable options for shipping more generally.
The Effect of Hydrogen on the Nanoindentation Behavior of Heat Treated 718 Alloy
Oct 2020
Publication
In this study the effect of precipitates on the surface mechanical properties in the presence of hydrogen (H) is investigated by in situ electrochemical nanoindentation. The nickel superalloy 718 is subjected to three different heat treatments leading to different sizes of the precipitates: (i) solution annealing (SA) to eliminate all precipitates (ii) the as-received (AR) sample with fine dispersed precipitates and (iii) the over-aged (OA) specimen with coarser precipitates. The nanoindentation is performed using a conical tip and a new method of reverse imaging is employed to calculate the nano-hardness. The results show that the hardness of the SA sample is significantly affected by H diffusion. However it could be recovered by removing the H from its matrix by applying an anodic potential. Since the precipitates in the OA and AR samples are different they are influenced by H differently. The hardness increase for the OA sample is more significant in −1200mV while for the AR specimen the H is more effective in −1500mV. In addition the pop-in load is reduced when the samples are exposed to cathodic charging and it cannot be fully recovered by switching to an anodic potential.
Palladium (Pd) Membranes as Key Enabling Technology for Pre-combustion CO2 Capture and Hydrogen Production
Aug 2017
Publication
Palladium (Pd) membranes are a promising enabling technology for power generation and hydrogen production with CO2 capture. SINTEF has developed and patented a flexible technology to produce Pd-alloy membranes that significantly improves flux and thereby reduces material costs. Reinertsen AS and SINTEF aim to demonstrate the Pd membrane technology for H2 separation on a side stream of the Statoil Methanol Plant at Tjeldbergodden Norway. In the present article we present the upscaling of the membrane manufacturing process together with the membrane module and skid design and construction.
Balancing GHG Mitigation and Land-use Conflicts: Alternative Northern European Energy System Scenarios
Jan 2022
Publication
Long-term power market outlooks suggest a rapid increase in renewable energy deployment as a main solution to greenhouse gas mitigation in the Northern European energy system. However the consequential area requirement is a non-techno-economic aspect that currently is omitted by many energy system optimization models. This study applies modeling to generate alternatives (MGA) technique to the Balmorel energy system model to address spatial conflicts related to increased renewable energy deployment. The approach searches for alternative solutions that minimize land-use conflicts while meeting the low-carbon target by allowing a 1% to 15% increase in system costs compared to the least-cost solution. Two alternative objectives are defined to reflect various aspects of spatial impact. The results show that the least-cost solution requires 1.2%–3.6% of the land in the modeled countries in 2040 for onshore wind and solar PV installations. A 10% increase in costs can reduce the required land area by 58% by relying more on offshore wind. Nuclear energy may also be an option if both onshore and offshore areas are to be reduced or in a less flexible system. Both offshore wind and nuclear energy technologies are associated with higher risks and pose uncertainties in terms of reaching the climate targets in time. The changes in costs and required land areas imply significantly higher annual costs ranging from 200 to 750 kEUR/km2 to avoid land use for energy infrastructure. Overall this study confirms that the energy transition strategies prioritizing land savings from energy infrastructure are feasible but high risks and costs of averted land are involved.
The Use of Metal Hydrides in Fuel Cell Applications
Feb 2017
Publication
This paper reviews state-of-the-art developments in hydrogen energy systems which integrate fuel cells with metal hydride-based hydrogen storage. The 187 reference papers included in this review provide an overview of all major publications in the field as well as recent work by several of the authors of the review. The review contains four parts. The first part gives an overview of the existing types of fuel cells and outlines the potential of using metal hydride stores as a source of hydrogen fuel. The second part of the review considers the suitability and optimisation of different metal hydrides based on their energy efficient thermal integration with fuel cells. The performances of metal hydrides are considered from the viewpoint of the reversible heat driven interaction of the metal hydrides with gaseous H2. Efficiencies of hydrogen and heat exchange in hydrogen stores to control H2 charge/discharge flow rates are the focus of the third section of the review and are considered together with metal hydride – fuel cell system integration issues and the corresponding engineering solutions. Finally the last section of the review describes specific hydrogen-fuelled systems presented in the available reference data.
A Barrier Analysis of a Generic Hydrogen Refuelling Station
Sep 2009
Publication
Any technical installation need appropriate safety barriers installed to prevent or mitigate any adverse effects concerning people property and environment. In this context a safety barrier is a series of elements each consisting of a technical system or human action that implement a planned barrier function to prevent control or mitigate the propagation of a condition or event into an undesired condition or event. This is also important for new technologies as hydrogen refuelling stations being operated at very high pressures up to 900bar. In order to establish the needed barriers a hazard identification of the installation has to be carried out to identify the possible hazardous events. In this study this identification was done using the generic layout of a future large hydrogen refuelling station that has been developed by the EU NoE HySafe. This was based on experiences with smaller scale refuelling stations that has been in operation for several years e.g. being used in the former CUTE and ECTOS projects. Using this approach the object of the study is to support activities to further improve the safety performance of future larger refuelling stations. This will again help to inform the authorities and the public to achieve a proper public awareness and to support building up a realistic risk and safety perception of the safety on such future refuelling stations. In the second step the hazardous events that may take place and the barriers installed to stop hazards and their escalation are analysed also using in-house developed software to model the barriers and to quantify their performance. The paper will present an overview and discuss the state-of-the-art of the barriers established in the generic refuelling station.
Materials Considerations in Hydrogen Production
Sep 2007
Publication
Correct selection and application of materials is essential to ensure safety and economy in production transportation and storage of hydrogen. There are several sources of materials challenges related to hydrogen. Established component producers may have limited experience in this specific field. Process developments may involve new process conditions with new demands on the materials. Further new materials will be added to the engineering toolbox to be used. The behaviour of these materials for hydrogen service may need additional documentation. Finally focus on hydrogen susceptibility and hydrogen damages alone may take away awareness of other subjects as trace elements by-products and change in raw materials which may be of as high importance for safety and quality. This overview of challenges and recommendations is made with emphasis on water electrolysis.
Dynamic Load Analysis of Explosion in Inhomogeneous Hydrogen-air Mixtures
Sep 2017
Publication
This paper presents results from experiments on gas explosions in inhomogeneous hydrogen-air mixtures. The experimental channel is 3 m with a cross section of 100 mm by 100 mm and a 0.25 mm ID nozzle for hydrogen release into the channel. The channel is open in one end. Spectral analysis of the pressure in the channel is used to determine dynamic load factors for SDOF structures. The explosion pressures in the channel will fluctuate with several frequencies or modes and a theoretical high DLF is seen when the pressure frequencies and eigen frequencies of the structure matches.
Enhancing the Efficiency of Power- and Biomass-to-liquid Fuel Processes Using Fuel-assisted Solid Oxide Electrolysis Cells
Apr 2022
Publication
Power- and biomass-to-liquid fuel processes (PBtL) can utilize renewable energy and residual forestry waste to produce liquid synthetic fuels which have the potential to mitigate the climate impacts of the current transportation infrastructure including the long-haul aviation sector. In a previous study we demonstrated that implementing a solid oxide electrolysis cell (SOEC) in the PBtL process can significantly increase the energy efficiency of fuel production by supplying the produced hydrogen to a reverse water gas shift (RWGS) reactor to generate syngas which is then fed downstream to a Fischer–Tropsch (FT) reactor. The tail gas emitted from the FT reactor consists primarily of a mixture of hydrogen carbon monoxide and methane and is often recycled to the entrained flow gasifier located at the beginning of the process. In this analysis we investigate the efficiency gains of the PBtL process as a result of redirecting the tail gas of the FT reactor to the anode of an SOEC to serve as fuel. Supplying fuel to an SOEC can lower the electrical work input required to facilitate steam electrolysis when reacting electrochemically with oxide ions in the anode which in turn can reduce oxygen partial pressures and thus alleviate material degradation. Accordingly we develop a thermodynamic framework to reveal the performance limits of fuel-assisted SOECs (FASOECs) and provide strategies to minimize oxygen partial pressures in the SOEC anode. Additionally we elucidate how much fuel is required to match the heating demands of a cell when steam is supplied to the cathode over a broad range of inlet temperatures and demonstrate the influence of a set of reaction pathways of the supplied fuel on the operating potential of an FASOEC and the corresponding efficiency gain of the PBtL process. Based on preliminary calculations we estimate that implementing an FASOEC in the PBtL process can increase the energy efficiency of fuel production to more than 90% depending on the amount of FT tail gas available to the system.
Heading for Hydrogen - The Oil and Gas Industry’s Outlook for Hydrogen, From Ambition to Reality
May 2020
Publication
The future of hydrogen energy is wrapped up with the future of natural gas renewable energy and carbon capture and storage (CCS). This yields useful synergies but also political economic and technical complexity. Nevertheless our survey of more than 1000 senior oil and gas professionals suggests a more certain future for hydrogen and that the time is right to begin scaling the hydrogen economy.
Vented Hydrogen Deflagrations in Containers: Effect of Congestion for Homogeneous Mixtures
Sep 2017
Publication
This paper presents results from an experimental study of vented hydrogen deflagrations in 20-foot ISO containers. The scenarios investigated include 14 tests with explosion venting through the doors of the containers and 20 tests with venting through openings in the roof. The parameters investigated include hydrogen concentration vent area type of venting device and the level of congestion inside the containers. All tests involved homogeneous and initially quiescent hydrogen-air mixtures. The results demonstrate the strong effect of congestion on the maximum reduced explosion pressures which typically is not accounted for in current standards and guidelines for explosion protection. The work is a deliverable from work package 2 (WP2) in the project “Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations” or HySEA which receives funding from the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) under grant agreement no. 671461.
Probability of Occurrence of ISO 14687-2 Contaminants in Hydrogen: Principles and Examples from Steam Methane Reforming and Electrolysis (Water and Chlor-alkali) Production Processes Model
Apr 2018
Publication
According to European Directive 2014/94/EU hydrogen providers have the responsibility to prove that their hydrogen is of suitable quality for fuel cell vehicles. Contaminants may originate from hydrogen production transportation refuelling station or maintenance operation. This study investigated the probability of presence of the 13 gaseous contaminants (ISO 14687-2) in hydrogen on 3 production processes: steam methane reforming (SMR) process with pressure swing adsorption (PSA) chlor-alkali membrane electrolysis process and water proton exchange membrane electrolysis process with temperature swing adsorption. The rationale behind the probability of contaminant presence according to process knowledge and existing barriers is highlighted. No contaminant was identified as possible or frequent for the three production processes except oxygen (frequent for chlor-alkali membrane process) carbon monoxide (frequent) and nitrogen (possible) for SMR with PSA. Based on it a hydrogen quality assurance plan following ISO 19880-8 can be devised to support hydrogen providers in monitoring the relevant contaminants.
Accidental Hydrogen Release in Gc-laboratory: A Case Study
Oct 2015
Publication
A 50-litre standard hydrogen gas cylinder was temporarily placed in a laboratory to supply hydrogen gas to a flame ionization detector (FID) for use in gas chromatography (GC). On 20 January 2015 the safety relief valve on the pressure regulator failed and released about 0.34 kg of hydrogen into the laboratory. The gas cloud did not ignite so there was no injury or damage. The results of a full investigation with a complete course of action and reconstruction are presented that verify the cause of the leakage and estimate the gas concentration of the dispersion and gas cloud. A preliminary simulation of the likely explosion is provided. If the gas cloud had ignited the explosion would most likely have caused significant structural damage to doors windows and possibly the walls.
Hydrogen as an Energy Carrier: An Evaluation of Emerging Hydrogen Value Chains
Nov 2018
Publication
Some 3% of global energy consumption today is used to produce hydrogen. Only 0.002% of this hydrogen about 1000 tonnes per annum(i) is used as an energy carrier. Yet as this timely position paper from DNV GL indicates hydrogen can become a major clean energy carrier in a world struggling to limit global warming.<br/>The company’s recently published 2018 Energy Transition Outlook(1) projects moderate uptake of hydrogen in this role towards 2050 then significant growth towards 2100. Building on that this position paper provides a more granular analysis of hydrogen as an energy carrier.
Decarbonization of the Iron and Steel Industry with Direct Reduction of Iron Ore with Green Hydrogen
Feb 2020
Publication
Production of iron and steel releases seven percent of the global greenhouse gas (GHG) emissions. Incremental changes in present primary steel production technologies would not be sufficient to meet the emission reduction targets. Replacing coke used in the blast furnaces as a reducing agent with hydrogen produced from water electrolysis has the potential to reduce emissions from iron and steel production substantially. Mass and energy flow model based on an open-source software (Python) has been developed in this work to explore the feasibility of using hydrogen direct reduction of iron ore (HDRI) coupled with electric arc furnace (EAF) for carbon-free steel production. Modeling results show that HDRI-EAF technology could reduce specific emissions from steel production in the EU by more than 35% at present grid emission levels (295 kgCO2/MWh). The energy consumption for 1 ton of liquid steel (tls) production through the HDRI-EAF route was found to be 3.72 MWh which is slightly more than the 3.48 MWh required for steel production through the blast furnace (BF) basic oxygen furnace route (BOF). Pellet making and steel finishing processes have not been considered. Sensitivity analysis revealed that electrolyzer efficiency is the most important factor affecting the system energy consumption while the grid emission factor is strongly correlated with the overall system emissions.
The Role of Lock-in Mechanisms in Transition Processes: The Case of Energy for Road Transport
Jul 2015
Publication
This paper revisits the theoretical concepts of lock-in mechanisms to analyse transition processes in energy production and road transportation in the Nordic countries focussing on three technology platforms: advanced biofuels e-mobility and hydrogen and fuel cell electrical vehicles. The paper is based on a comparative analysis of case studies.<br/>The main lock-in mechanisms analysed are learning effects economies of scale economies of scope network externalities informational increasing returns technological interrelatedness collective action institutional learning effects and the differentiation of power.<br/>We show that very different path dependencies have been reinforced by the lock-in mechanisms. Hence the characteristics of existing regimes set the preconditions for the development of new transition pathways. The incumbent socio-technical regime is not just fossil-based but may also include mature niches specialised in the exploitation of renewable sources. This implies a need to distinguish between lock-in mechanisms favouring the old fossil-based regime well-established (mature) renewable energy niches or new pathways.
Assessment of Hydrogen Quality Dispensed for Hydrogen Refuelling Stations in Europe
Dec 2020
Publication
The fuel quality of hydrogen dispensed from 10 refuelling stations in Europe was assessed. Representative sampling was conducted from the nozzle by use of a sampling adapter allowing to bleed sample gas in parallel while refuelling an FCEV. Samples were split off and distributed to four laboratories for analysis in accordance with ISO 14687 and SAE J2719. The results indicated some inconsistencies between the laboratories but were still conclusive. The fuel quality was generally good. Elevated nitrogen concentrations were detected in two samples but not in violation with the new 300 μmol/mol tolerance limit. Four samples showed water concentrations higher than the 5 μmol/mol tolerance limit estimated by at least one laboratory. The results were ambiguous: none of the four samples showed all laboratories in agreement with the violation. One laboratory reported an elevated oxygen concentration that was not corroborated by the other two laboratories and thus considered an outlier.
Hydrogen Explosions in 20’ ISO Container
Oct 2015
Publication
This paper describes a series of explosion experiments in inhomogeneous hydrogen air clouds in a standard 20′ ISO container. Test parameter variations included nozzle configuration jet direction reservoir back pressure time of ignition after release and degree of obstacles. The paper presents the experimental setup resulting pressure records and high speed videos. The explosion pressures from the experiments without obstacles were in the range of 0.4–7 kPa. In the experiments with obstacles the gas exploded more violently producing pressures in order of 100 kPa.
Modelling of Hydrogen Jet Fires Using CFD
Sep 2011
Publication
The computational fluid dynamics (CFD) software FLACS has primarily been developed to model dispersion and explosion phenomena; however models for the simulation of jet fires are under development. The aim is to be able to predict industrial fires efficiently and with good precision. Newly developed models include e.g. flame models for non-premixed flames discrete transfer radiation model as well as soot models. Since the time scales for fire simulations are longer than for explosions the computational speed is important. The recent development of non-compressible and parallel solvers in FLACS may therefore be important to ensure efficiency. Hydrogen flames may be invisible will generate no soot and tend to radiate less than hydrocarbon fuels. Due to high pressure storage the flame lengths can be significant. Simpler jet flame relations can not predict the jet flame interaction with objects and barriers and thus the heat loads on impacted objects. The development of efficient and precise CFD-tools for hydrogen fires is therefore important. In this paper the new models for the simulation of fire are described. These models are currently under development and this manuscript describes the current status of the work. Jet fire experiments performed by Health and Safety Laboratories (HSL) both free jets and impinging jets will also be simulated to evaluate the applicability and validity of the new fire models.
Safe Hydrogen Fuel Handling and Use for Efficient Implementation – SH2IFT
Sep 2019
Publication
The SH2IFT project combines social and technical scientific methods to address knowledge gaps regarding safe handling and use of gaseous and liquid hydrogen. Theoretical approaches will be complemented by fire and explosion experiments with emphasis on topics of strategic importance to Norway such as tunnel safety maritime applications etc. Experiments include Rapid Phase Transition Boiling Liquid Expanding Vapour Explosion and jet fires. This paper gives an overview of the project and preliminary results.
PIV-measurements of Reactant Flow in Hydrogen-air Explosions
Sep 2017
Publication
The paper present the work on PIV-measurements of reactant flow velocity in front of propagating flames in hydrogen-air explosions. The experiments was performed with hydrogen-air mixture at atmospheric pressure and room temperature. The experimental rig was a square channel with 45 × 20 mm2 cross section 300 mm long with a single cylindrical obstacle of blockage ratio 1/3. The equipment used for the PIV-measurements was a Firefly diode laser from Oxford lasers Photron SA-Z high-speed camera and a particle seeder producing 1 μm droplets of water. The gas concentrations used in the experiments was 14 and 17 vol% hydrogen in air. The resulting explosion can be characterized as slow since the maximum flow velocity of the reactants was 13 m/s in the 14% mixture and 23 m/s in the 17% mixture. The maximum flow velocities was measured during the flame-vortex interaction and at two obstacle diameters behind the obstacle. The flame-vortex interaction contributed to the flame acceleration by increasing the overall reaction rate and the flow velocity. The flame area as a function of position is the same for both concentrations as the flame passes the obstacle.
CFD and VR for Risk Communication and Safety Training
Sep 2011
Publication
There are new safety challenges with an increased use of hydrogen e.g. that people may not see dangerous jet flames in case of an incident. Compared to conventional fuels hydrogen has very different characteristics and physical properties and is stored at very high pressure or at very low temperatures. Thus the nature of hazard scenarios will be very different. Consequence modelling of ventilation releases explosions and fires can be used to predict and thus understand hazards. In order to describe the detailed development of a hazard scenario and evaluate ways of mitigation 3D Computational Fluid Dynamics (CFD) models will be required. Even with accurate modelling the communication of risk can be challenging. For this visualization in virtual reality (VR) may be of good help in which the CFD model predictions are presented in a realistic 3D environment with the possibility to include sounds like noise from a high pressure release explosion or fire. In cooperation with Statoil Christian Michelsen Research (CMR) and GexCon have developed the VRSafety application. VRSafety can visualize simulation results from FLACS (and another CFD-tool KFX) in an immersive VR-lab or on a PC. VRSafety can further be used to interactively control and start new CFD-simulations during the sessions. The combination of accurate CFD-modelling visualization and interactive use through VRSafety represents a powerful toolbox for safety training and risk communication to first-responders employees media and other stakeholders. It can also be used for lessons learned sessions studying incidents and accidents and to demonstrate what went wrong and how mitigation could have prevented accidents from happening. This paper will describe possibilities with VRSafety and give examples of use.
Numerical Simulations of a Large Hydrogen Release in a Process Plant
Sep 2009
Publication
This paper describes a series of numerical simulations with release and ignition of hydrogen. The objective of this work was to re-investigate the accidental explosion in an ammonia plant which happened in Norway in 1985 with modern CFD tools. The severe hydrogen-air explosion led to two fatalities and complete destruction of the factory building where the explosion occurred. A case history of the accident was presented at the 1.st ICHS in Pisa 2005.<br/>The numerical simulations have been performed with FLACS a commercial CFD simulation tool for gas dispersion and gas explosions. The code has in the recent years been validated in the area of hydrogen dispersion and explosions.<br/>The factory building was 100 m long 10 m wide and 7 m high. A blown-out gasket in a water pump led to release of hydrogen from a large reservoir storing gaseous hydrogen at 3.0 MPa. The accident report estimated a total mass of released hydrogen between 10 and 20 kg. The location of the faulty gasket is known but the direction of the accidental release is not well known and has been one of the topics of our investigations. Several simulations have been performed to investigate the mixing process of hydrogen-air clouds and the development of a flammable gas cloud inside the factory building resulting in a simulation matrix with dispersions in all axis directions. Simulations of ignition of the different gas clouds were carried out and resulting pressure examined. These results have been compared with the damages observed during the accident investigation.<br/>We have also performed FLACS simulations to study the effect of natural venting and level of congestion. The height of the longitudinal walls has been varied leading to different vent openings at floor level at the ceiling and a combination of the two. This was done to investigate the effects of congestion with regards to gas cloud formation.<br/>The base case simulation appears to be in good accordance to the observed damages from the accident. The simulations also show that the build up of the gas cloud strongly depends on the direction of the jet and degree of ventilation. The CFD study has given new insights to the accident and the results are a clear reminder of the importance of natural venting in hydrogen safety.
Development of Uniform Harm Criteria for Use in Quantitative Risk Analysis of the Hydrogen Infrastructure
Sep 2009
Publication
This paper discusses the preliminary results of the Risk Management subtask efforts within the International Energy Agency (IEA) Hydrogen Implementing Agreement (HIA) Task 19 on Hydrogen Safety to develop uniform harm criteria for use in the Quantitative Risk Assessments (QRAs) of hydrogen facilities. The IEA HIA Task 19 efforts are focused on developing guidelines and criteria for performing QRAs of hydrogen facilities. The performance of QRAs requires that the level of harm that is represented in the risk evaluation be established using deterministic models. The level of harm is a function of the type and level of hazard. The principle hazard associated with hydrogen facilities is uncontrolled accumulation of hydrogen in (semi) confined spaces and consecutive ignition. Another significant hazard is combustion of accidentally released hydrogen gas or liquid which may or may not happen instantaneously. The primary consequences from fire hazards consist of personnel injuries or fatalities or facility and equipment damage due to high air temperatures radiant heat fluxes or direct contact with hydrogen flames. The possible consequences of explosions on humans and structures or equipment include blast wave overpressure effects impact from fragments generated by the explosion the collapse of buildings and the heat effects from subsequent fire balls. A harm criterion is used to translate the consequences of an accident evaluated from deterministic models to a probability of harm to people structures or components. Different methods can be used to establish harm criteria including the use of threshold consequence levels and continuous functions that relate the level of a hazard to a probability of damage. This paper presents a survey of harm criteria that can be utilized in QRAs and makes recommendations on the criteria that should be utilized for hydrogen-related hazards.
Metal Hydride Hydrogen Compressors
Feb 2014
Publication
Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine – the metal hydride material itself – should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage hydrogen sorption kinetics and effective thermal conductivity) the thermodynamics of the metal–hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimised to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors reduction of slope of the isotherms and hysteresis increase of cycling stability and life time together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation.<br/>The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal–hydrogen systems suitable for the hydrogen compression; and (b) applied aspects including their consideration from the applied thermodynamic viewpoint system design features and performances of the metal hydride compressors and major applications.
Can the Addition of Hydrogen to Natural Gas Reduce the Explosion Risk?
Sep 2009
Publication
One of the main benefits sought by including hydrogen in the alternative fuels mix is emissions reduction – eventually by 100%. However in the near term there is a very significant cost differential between fossil fuels and hydrogen. Hythane (a blend of hydrogen and natural gas) can act as a viable next step on the path to an ultimate hydrogen economy as a fuel blend consisting of 8−30 % hydrogen in methane can reduce emissions while not requiring significant changes in existing infrastructure. This work seeks to evaluate whether hythane may be safer than both hydrogen and methane under certain conditions. This is due to the fact hythane combines the positive safety properties of hydrogen (strong buoyancy high diffusivity) and methane (much lower flame speeds and narrower flammability limits as compared to hydrogen). For this purpose several different mixture compositions (e.g. 8 % 20 % and 30 % hydrogen) are considered. The evaluation of (a) dispersion characteristics (which are more positive than for methane) (b) combustion characteristics (which are closer to methane than hydrogen) and (c) Combined dispersion + explosion risk is performed. This risk is expected to be comparable to that of pure methane possibly lower in some situations and definitely lower than for pure hydrogen. The work is performed using the CFD software FLACS that has been well-validated for safety studies of both natural gas/methane and hydrogen systems. The first part of the work will involve validating the flame speeds and flammability limits predicted by FLACS against values available in literature. The next part of the work involves validating the overpressures predicted by the CFD tool for combustion of premixed mixtures of methane and hydrogen with air against available experimental data. In the end practical systems such as vehicular tunnels garages etc. is used to demonstrate positive safety benefits of hythane with comparisons to similar simulations for both hydrogen and methane.
Structural Response for Vented Hydrogen Deflagrations: Coupling CFD and FE Tools
Sep 2017
Publication
This paper describes a methodology for simulating the structural response of vented enclosures during hydrogen deflagrations. The paper also summarises experimental results for the structural response of 20-foot ISO (International Organization for Standardization) containers in a series of vented hydrogen deflagration experiments. The study is part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA). The project is funded by the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 671461. The HySEA project focuses on vented hydrogen deflagrations in containers and smaller enclosures with internal congestion representative of industrial applications. The structural response modelling involves one-way coupling of pressure loads taken either directly from experiments or from simulations with the computational fluid dynamics (CFD) tool FLACS to the non-linear finite element (FE) IMPETUS Afea Solver. The performance of the FE model is evaluated for a range of experiments from the HySEA project in both small-scale enclosures and 20-foot ISO containers. The paper investigates the sensitivity of results from the FE model to the specific properties of the geometry model. The performance of FLACS is evaluated for a selected set of experiments from the HySEA project. Furthermore the paper discusses uncertainties associated with the combined modelling approach.
Hytunnel Project to Investigate the Use of Hydrogen Vehicles in Road Tunnels
Sep 2009
Publication
Hydrogen vehicles may emerge as a leading contender to replace today’s internal combustion engine powered vehicles. A Phenomena Identification and Ranking Table exercise conducted as part of the European Network of Excellence on Hydrogen Safety (HySafe) identified the use of hydrogen vehicles in road tunnels as a topic of important concern. An internal project called HyTunnel was duly established within HySafe to review identify and analyse the issues involved and to contribute to the wider activity to establish the true nature of the hazards posed by hydrogen vehicles in the confined space of a tunnel and their relative severity compared to those posed by vehicles powered by conventional fuels including compressed natural gas (CNG). In addition to reviewing current hydrogen vehicle designs tunnel design practice and previous research a programme of experiments and CFD modelling activities was performed for selected scenarios to examine the dispersion and explosion hazards potentially posed by hydrogen vehicles. Releases from compressed gaseous hydrogen (CGH2) and liquid hydrogen (LH2) powered vehicles have been studied under various tunnel geometries and ventilation regimes. The findings drawn from the limited work done so far indicate that under normal circumstances hydrogen powered vehicles do not pose a significantly higher risk than those powered by petrol diesel or CNG but this needs to be confirmed by further research. In particular obstructions at tunnel ceiling level have been identified as a potential hazard in respect to fast deflagration or even detonation in some circumstances which warrants further investigation. The shape of the tunnel tunnel ventilation and vehicle pressure relief device (PRD) operation are potentially important parameters in determining explosion risks and the appropriate mitigation measures.
Explosion and Fire Risk Analyses of Maritime Fuel Cell Rooms with Hydrogen
Sep 2017
Publication
A methodology for explosion and fire risk analyses in enclosed rooms is presented. The objectives of this analysis are to accurately predict the risks associated with hydrogen leaks in maritime applications and to use the approach to provide decision support regarding design and risk-prevention and risk mitigating measures. The methodology uses CFD tools and simpler consequence models for ventilation dispersion and explosion scenarios as well as updated frequency for leaks and ignition. Risk is then efficiently calculated with a Monte Carlo routine capturing the transient behavior of the leak. This makes it possible to efficiently obtain effects of sensitivities and design options maintaining safety and reducing costs.
Simulating Vented Hydrogen Deflagrations: Improved Modelling in the CFD Tool Flacs-Hydrogen
Sep 2019
Publication
This paper describes validation of the computational fluid dynamics tool FLACS-Hydrogen. The validation study focuses on concentration and pressure data from vented deflagration experiments performed in 20-foot shipping containers as part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA) funded by the Fuel Cells and Hydrogen 2 Joint Undertaking (FCH 2 JU). The paper presents results for tests involving inhomogeneous hydrogen-air clouds generated from realistic releases performed during the HySEA project. For both experiments and simulations the peak overpressures obtained for the stratified mixtures are higher than those measured for lean homogeneous mixtures with the same amount of hydrogen. Using an in-house version of FLACS-Hydrogen with the numerical solver Flacs3 and improved physics models results in significantly improved predictions of the peak overpressures compared to the predictions by the standard Flacs2 solver. The paper includes suggestions for further improvements to the model system.
HYDRIDE4MOBILITY: An EU HORIZON 2020 Project on Hydrogen Powered Fuel Cell Utility Vehicles Using Metal Hydrides in Hydrogen Storage and Refuelling Systems
Feb 2021
Publication
Volodymyr A. Yartys,
Mykhaylo V. Lototskyy,
Vladimir Linkov,
Sivakumar Pasupathi,
Moegamat Wafeeq Davids,
Gojmir Radica,
Roman V. Denys,
Jon Eriksen,
José Bellosta von Colbe,
Klaus Taube,
Giovanni Capurso,
Martin Dornheim,
Fahmida Smith,
Delisile Mathebula,
Dana Swanepoel,
Suwarno Suwarno and
Ivan Tolj
The goal of the EU Horizon 2020 RISE project 778307 “Hydrogen fuelled utility vehicles and their support systems utilising metal hydrides” (HYDRIDE4MOBILITY) is in addressing critical issues towards a commercial implementation of hydrogen powered forklifts using metal hydride (MH) based hydrogen storage and PEM fuel cells together with the systems for their refuelling at industrial customers facilities. For these applications high specific weight of the metallic hydrides has an added value as it allows counterbalancing of a vehicle with no extra cost. Improving the rates of H2 charge/discharge in MH on the materials and system level simplification of the design and reducing the system cost together with improvement of the efficiency of system “MH store-FC” is in the focus of this work as a joint effort of consortium uniting academic teams and industrial partners from two EU and associated countries Member States (Norway Germany Croatia) and two partner countries (South Africa and Indonesia).<br/>The work within the project is focused on the validation of various efficient and cost-competitive solutions including (i) advanced MH materials for hydrogen storage and compression (ii) advanced MH containers characterised by improved charge-discharge dynamic performance and ability to be mass produced (iii) integrated hydrogen storage and compression/refuelling systems which are developed and tested together with PEM fuel cells during the collaborative efforts of the consortium.<br/>This article gives an overview of HYDRIDE4MOBILITY project focused on the results generated during its first phase (2017–2019).
Simulation of DDT in Hydrogen-Air Behind a Single Obstacle
Sep 2011
Publication
Two-dimensional numerical simulations of deflagration-to-detonation transition (DDT) in hydrogen–air mixtures are presented and compared with experiments. The investigated geometry was a 3 m long square channel. One end was closed and had a single obstacle placed 1 m from the end and the other end was open to the atmosphere. The mixture was ignited at the closed end. Experiments and simulations showed that DDT occurred within 1 m behind the obstacle. The onset of detonation followed a series of local explosions occurring far behind the leading edge of the flame in a layer of unburned reactants between the flame and the walls. A local explosion was also seen in the experiments and the pressure records indicated that there may have been more. Furthermore local explosions were observed in the experiments and simulations which did not detonate. The explosions should have sufficient strength and should explode in a layer of sufficient height to result in a detonation. The numerical resolution was 0.5 mm per square cell and further details of the combustion model used are provided in the paper.
Dissecting the Exergy Balance of a Hydrogen Liquefier: Analysis of a Scaled-up Claude Hydrogen Liquefier with Mixed Refrigerant Pre-cooling
Oct 2020
Publication
For liquid hydrogen (LH2) to become an energy carrier in energy commodity markets at scales comparable to for instance LNG liquefier capacities must be scaled up several orders of magnitude. While state-of-the-art liquefiers can provide specific power requirements down to 10 kWh/kg a long-term target for scaled-up liquefier trains is 6 kWh/kg. High capacity will shift the cost weighting more towards operational expenditures which motivates for measures to improve the efficiency. Detailed exergy analysis is the best means for gaining a clear understanding of all losses occurring in the liquefaction process. This work analyses in detail a hydrogen liquefier that is likely to be realisable without intermediate demonstration phases and all irreversibilities are decomposed to the component level. The overall aim is to identify the most promising routes for improving the process. The overall power requirement is found to be 7.09 kWh/kg with stand-alone exergy efficiencies of the mixed-refrigerant pre-cooling cycle and the cryogenic hydrogen Claude cycle of 42.5% and 38.4% respectively. About 90% of the irreversibilities are attributed to the Claude cycle while the remainder is caused by pre-cooling to 114 K. For a component group subdivision the main contributions to irreversibilities are hydrogen compression and intercooling (39%) cryogenic heat exchangers (21%) hydrogen turbine brakes (15%) and hydrogen turbines (13%). Efficiency improvement measures become increasingly attractive with scale in general and several options exist. An effective modification is to recover shaft power from the cryogenic turbines. 80% shaft-to-shaft power recovery will reduce the power requirement to 6.57 kWh/kg. Another potent modification is to replace the single mixed refrigerant pre-cooling cycle with a more advanced mixed-refrigerant cascade cycle. For substantial scaling-up in the long term promising solutions can be cryogenic refrigeration cycles with refrigerant mixtures of helium/neon/hydrogen enabling the use of efficient and well scalable centrifugal compressors.
Hazard Distance Nomograms for a Blast Wave from a Compressed Hydrogen Tank Rupture in a Fire
Sep 2017
Publication
Nomograms for assessment of hazard distances from a blast wave generated by a catastrophic rupture of stand-alone (stationary) and onboard compressed hydrogen cylinder in a fire are presented. The nomograms are easy to use hydrogen safety engineering tools. They were built using the validated and recently published analytical model. Two types of nomograms were developed – one for use by first responders and another for hydrogen safety engineers. The paper underlines the importance of an international effort to unify harm and damage criteria across different countries as the discrepancies identified by the authors gave the expected results of different hazard distances for different criteria.
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.
Mapping of Hydrogen Fuel Quality in Europe
Nov 2020
Publication
As part of FCH-JU funded HyCoRA project running from 2014 to 2017 28 gaseous and 13 particulate samples were collected from hydrogen refuelling stations in Europe. Samples were collected with commercial sampling instruments and analysis performed in compliance with prevailing fuel quality standards. Sampling was conducted with focus on diversity in feedstock as well as commissioning date of the HRS. Results indicate that the strategy for sampling was good. No evidence of impurity cross-over was observed. Parallel samples collected indicate some variation in analytical results. It was however found that fuel quality was generally good. Fourteen analytical results were in violation with the fuel tolerance limits. Therefore eight or 29% of the samples were in violation with the fuel quality requirements. Nitrogen oxygen and organics were the predominant impurities quantified. Particulate impurities were found to be within fuel quality specifications. No correlation between fuel quality and hydrogen feedstock or HRS commissioning date was found. Nitrogen to oxygen ratios gave no indication of samples being contaminated by air. A comparison of analytical results between two different laboratories were conducted. Some difference in analytical results were observed.
Recent Progress and Approaches on Transition Metal Chalcogenides for Hydrogen Production
Dec 2021
Publication
Development of efficient and affordable photocatalysts is of great significance for energy production and environmental sustainability. Transition metal chalcogenides (TMCs) with particle sizes in the 1–100 nm have been used for various applications such as photocatalysis photovoltaic and energy storage due to their quantum confinement effect optoelectronic behavior and their stability. In particular TMCs and their heterostructures have great potential as an emerging inexpensive and sustainable alternative to metal-based catalysts for hydrogen evolution. Herein the methods used for the fabrication of TMCs characterization techniques employed and the different methods of solar hydrogen production by using different TMCs as photocatalyst are reviewed. This review provides a summary of TMC photocatalysts for hydrogen production.
Hydrogen Fuelling Station, CEP-Berlin – Safety Risk Assessment and Authority Approval Experience and Lessons Learned
Sep 2005
Publication
The CEP (Clean Energy Partnership) – Berlin is one of the most diversified hydrogen demonstration projects at present. The first hydrogen fuelling station serving 16 cars is fully integrated in an ordinary highly frequented Aral service station centrally located at Messedamm in Berlin. Hydro has supplied and is the owner of the electrolyser with ancillary systems. This unit produces gaseous hydrogen at 12 bar with use of renewable energy presently serving 13 of the cars involved. The CEP project is planned to run for a period of five years and is supported by the German Federal Government and is part of the German sustainability strategy. During the planning and design phase there have been done several safety related assessments and analyses:
- Hydro has carried out a HAZOP (HAZard and OPerability) analysis of the electrolyser and ancillary systems delivered by Hydro Electrolysers.
- Hydro arranged with support from the partners a HAZOP analysis of the interface between the electrolyser and the compressor an interface with two different suppliers on each side.
- A QRA (Quantitative Risk Assessment) of the entire fuelling station has been carried out.
- Hydro has carried out a quantitative explosion risk analysis of the electrolyser container supplied by Hydro Electrolysers.
Risk Modelling of a Hydrogen Refuelling Station Using a Bayesian Network
Sep 2009
Publication
Fault trees and event trees have for decades been the most commonly applied modelling tools in both risk analysis in general and the risk analysis of hydrogen applications including infrastructure in particular. It is sometimes found challenging to make traditional Quantitative Risk Analyses sufficiently transparent and it is frequently challenging for outsiders to verify the probabilistic modelling. Bayesian Networks (BN) are a graphical representation of uncertain quantities and decisions that explicitly reveal the probabilistic dependence between the variables and the related information flow. It has been suggested that BN represent a modelling tool that is superior to both fault trees and event trees with respect to the structuring and modelling of large complex systems. This paper gives an introduction to BN and utilises a case study as a basis for discussing and demonstrating the suitability of BN for modelling the risks associated with the introduction of hydrogen as an energy carrier. In this study we explore the benefits of modelling a hydrogen refuelling station using BN. The study takes its point of departure in input from a traditional detailed Quantitative Risk Analysis conducted by DNV during the HyApproval project. We compare and discuss the two analyses with respect to their advantages and disadvantages. We especially focus on a comparison of transparency and the results that may be extracted from the two alternative procedures.
CFD Simulation Study to Investigate the Risk from Hydrogen Vehicles in Tunnels
Sep 2007
Publication
When introducing hydrogen-fuelled vehicles an evaluation of the potential change in risk level should be performed. It is widely accepted that outdoor accidental releases of hydrogen from single vehicles will disperse quickly and not lead to any significant explosion hazard. The situation may be different for more confined situations such as parking garages workshops or tunnels. Experiments and computer modelling are both important for understanding the situation better. This paper reports a simulation study to examine what if any is the explosion risk associated with hydrogen vehicles in tunnels. Its aim was to further our understanding of the phenomena surrounding hydrogen releases and combustion inside road tunnels and furthermore to demonstrate how a risk assessment methodology developed for the offshore industry could be applied to the current task. This work is contributing to the EU Sixth Framework (Network of Excellence) project HySafe aiding the overall understanding that is also being collected from previous studies new experiments and other modelling activities. Releases from hydrogen cars (containing 700 bar gas tanks releasing either upwards or downwards or liquid hydrogen tanks releasing only upwards) and buses (containing 350 bar gas tanks releasing upwards) for two different tunnel layouts and a range of longitudinal ventilation conditions have been studied. The largest release modelled was 20 kg H2 from four cylinders in a bus (via one vent) in 50 seconds with an initial release rate around 1000 g/s. Comparisons with natural gas (CNG) fuelled vehicles have also been performed. The study suggests that for hydrogen vehicles a typical worst-case risk assessment approach assuming the full gas inventory being mixed homogeneously at stoichiometry could lead to severe explosion loads. However a more extensive study with more realistic release scenarios reduced the predicted hazard significantly. The flammable gas cloud sizes were still large for some of the scenarios but if the actual reactivity of the predicted clouds is taken into account very moderate worst-case explosion pressures are predicted. As a final step of the risk assessment approach a probabilistic QRA study is performed in which probabilities are assigned to different scenarios time dependent ignition modelling is applied and equivalent stoichiometric gas clouds are used to translate reactivity of dispersed nonhomogeneous clouds. The probabilistic risk assessment study is based on over 200 dispersion and explosion CFD calculations using the commercially available tool FLACS. The risk assessment suggested a maximum likely pressure level of 0.1-0.3 barg at the pressure sensors that were used in the study. Somewhat higher pressures are seen elsewhere due to reflections (e.g. under the vehicles). Several other interesting observations were found in the study. For example the study suggests that for hydrogen releases the level of longitudinal tunnel ventilation has only a marginal impact on the predicted risk since the momentum of the releases and buoyancy of hydrogen dominates the mixing and dilution processes.
Technical and Economic Analysis of One-Stop Charging Stations for Battery and Fuel Cell EV with Renewable Energy Sources
Jun 2020
Publication
Currently most of the vehicles make use of fossil fuels for operations resulting in one of the largest sources of carbon dioxide emissions. The need to cut our dependency on these fossil fuels has led to an increased use of renewable energy sources (RESs) for mobility purposes. A technical and economic analysis of a one-stop charging station for battery electric vehicles (BEV) and fuel cell electric vehicles (FCEV) is investigated in this paper. The hybrid optimization model for electric renewables (HOMER) software and the heavy-duty refueling station analysis model (HDRSAM) are used to conduct the case study for a one-stop charging station at Technical University of Denmark (DTU)-Risø campus. Using HOMER a total of 42 charging station scenarios are analyzed by considering two systems (a grid-connected system and an off-grid connected system). For each system three different charging station designs (design A-hydrogen load; design B-an electrical load and design C-an integrated system consisting of both hydrogen and electrical load) are set up for analysis. Furthermore seven potential wind turbines with different capacity are selected from HOMER database for each system. Using HDRSAM a total 18 scenarios are analyzed with variation in hydrogen delivery option production volume hydrogen dispensing option and hydrogen dispensing option. The optimal solution from HOMER for a lifespan of twenty-five years is integrated into design C with the grid-connected system whose cost was $986065. For HDRSAM the optimal solution design consists of tube trailer as hydrogen delivery with cascade dispensing option at 350 bar together with high production volume and the cost of the system was $452148. The results from the two simulation tools are integrated and the overall cost of the one-stop charging station is achieved which was $2833465. The analysis demonstrated that the one-stop charging station with a grid connection is able to fulfil the charging demand cost-effectively and environmentally friendly for an integrated energy system with RESs in the investigated locations.
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.
Hydrogen Refuelling Stations for Public Transport Quality and Safety in the User-interface
Sep 2007
Publication
Hydrogen stations and supply systems for public transport have been demonstrated in a number of European cities during the last four years. The first refuelling facility was put into operation in Reykjavik in April 2003. Experience from the four years of operation shows that safety related incidents are more frequent in the user interface than in the other parts of the hydrogen refuelling station (HRS). This might be expected taking into account the fact that the refuelling is manually operated and that according to industrial statistics human failures normally stand for more than 80% of all safety related incidents. On the other hand the HRS experience needs special attention since the refuelling at the existing stations is carried out by well trained personnel and that procedures and systems are followed closely. So far the quality and safety approach to hydrogen refuelling stations has been based on industrial experience. This paper addresses the challenge related to the development of safe robust and easy to operate refuelling systems. Such systems require well adapted components and system solutions as well as user procedures. The challenge to adapt the industrial based quality and safety philosophy and methodologies to new hydrogen applications and customers in the public sector is addressed. Risk based safety management and risk acceptance criteria relevant to users and third party are discussed in this context. Human factors and the use of incident reporting as a tool for continuous improvement are also addressed. The paper is based on internal development programmes for hydrogen refuelling stations in Hydro and on participation in international EU and IPHE projects such as CUTE HyFLEET:CUTE HySafe and HyApproval.
Fire Tests Carried Out in FCH JU FIRECOMP Project, Recommendations and Application to Safety of Gas Storage Systems
Sep 2017
Publication
In the event of a fire composite pressure vessels behave very differently from metallic ones: the material is degraded potentially leading to a burst without significant pressure increase. Hence such objects are when necessary protected from fire by using thermally-activated devices (TPRD) and standards require testing cylinder and TPRD together. The pre-normative research project FireComp aimed at understanding better the conditions which may lead to burst through testing and simulation and proposed an alternative way of assessing the fire performance of composite cylinders. This approach is currently used by Air Liquide for the safety of composite bundles carrying large amounts of hydrogen gas.
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.
Hysafe SBEP-V20: Numerical Predictions of Release Experiments Inside a Residential Garage With Passive Ventilation
Sep 2009
Publication
This work presents the results of the Standard Benchmark Exercise Problem (SBEP) V20 of Work Package 6 (WP6) of HySafe Network of Excellence (NoE) co-funded by the European Commission in the frame of evaluating the quality and suitability of codes models and user practices by comparative assessments of code results. The benchmark problem SBEP-V20 covers release scenarios that were experimentally investigated in the past using helium as a substitute to hydrogen. The aim of the experimental investigations was to determine the ventilation requirements for parking hydrogen fuelled vehicles in residential garages. Helium was released under the vehicle for 2 h with 7.200 l/h flow rate. The leak rate corresponded to a 20% drop of the peak power of a 50 kW fuel cell vehicle. Three double vent garage door geometries are considered in this numerical investigation. In each case the vents are located at the top and bottom of the garage door. The vents vary only in height. In the first case the height of the vents is 0.063 m in the second 0.241 m and in the third 0.495 m. Four HySafe partners participated in this benchmark. The following CFD packages with the respective models were applied to simulate the experiments: ADREA-HF using k–ɛ model by partner NCSRD FLACS using k–ɛ model by partner DNV FLUENT using k–ɛ model by partner UPM and CFX using laminar and the low-Re number SST model by partner JRC. This study compares the results predicted by the partners to the experimental measurements at four sensor locations inside the garage with an attempt to assess and validate the performance of the different numerical approaches.
Simulation of Detonation after an Accidental Hydrogen Release in Enclosed Environments
Sep 2007
Publication
An accidental hydrogen release in equipment enclosures may result in the presence of a detonable mixture in a confined environment. Numerical simulation is potentially a useful tool for damage assessment in these situations. To assess the value of CFD techniques numerical simulation of detonation was performed for two realistic scenarios. The first scenario starts with a pipe failure in an electrolyzer resulting in a leak of 42 g of hydrogen. The second scenario deals with a failure in a reformer where 84 g of hydrogen is released. In both cases dispersion patterns were first obtained from separate numerical simulation and were then used as initial condition in a detonation simulation based upon the reactive Euler's equations. Energy was artificially added in a narrow region to simulate detonative ignition. In the electrolyzer ignition was assumed to occur 500 ms after beginning of the release. Results show a detonation failing on the top and bottom side but propagating left and right before eventually failing also. Average impulse was 500 Ns/m². For the reformer three cases were simulated with ignition 1.0 1.4 and 2.0 seconds after the beginning of the release. In two cases the detonation wave failed everywhere except in the direction of the release in which it continued propagating until reaching the side wall. In the third the detonation failed everywhere at first but later a deflagration to detonation transition occurred resulting in a strong wave that propagated rapidly toward the side wall. In all three cases the consequences are more serious than in the electrolyzer.
The Effect of Hydrogen Enrichment, Flame-flame Interaction, Confinement, and Asymmetry on the Acoustic Response of a Model Can Combustor
Apr 2022
Publication
To maximise power density practical gas turbine combustion systems have several injectors which can lead to complex interactions between flames. However our knowledge about the effect of flame-flame interactions on the flame response the essential element to predict the stability of a combustor is still limited. The present study investigates the effect of hydrogen enrichment flame-flame interaction confinement and asymmetries on the linear and non-linear acoustic response of three premixed flames in a simple can combustor. A parametric study of the linear response characterised by the flame transfer function (FTF) is performed for swirling and non-swirling flames. Flame-flame interactions were achieved by changing the injector spacing and the level of hydrogen enrichment by power from 10 to 50%. It was found that the latter had the most significant effect on the flame response. Asymmetry effects were investigated by changing one of the flames by using a different bluff-body to alter both the flame shape and flow field. The global flame response showed that the asymmetric cases can be reconstructed using a superposition of the two symmetric cases where all three bluff-bodies and flames are the same. Overall the linear response characterised by the flame transfer function (FTF) showed that the effect of increasing the level of hydrogen enrichment is more pronounced than the effect of the injector spacing. Increasing hydrogen enrichment results in more compact flames which minimises flame-flame interactions. More compact flames increase the cut-off frequency which can lead to self-excited modes at higher frequencies. Finally the non-linear response was characterised by measuring the flame describing function (FDF) at a frequency close to a self-excited mode of the combustor for different injector spacings and levels of hydrogen enrichment. It is shown that increasing the hydrogen enrichment leads to higher saturation amplitude whereas the effect of injector spacing has a comparably smaller effect.
Modelling and Numerical Simulation of Hydrogen Jet Fires for Industrial Safety Analyses – Comparison with Large-scale Experiments
Sep 2019
Publication
Reliable predictive tools for hydrogen safety engineering are needed to meet increased and more widespread use of hydrogen in the society. Industrial models and methods used to establish thermal radiation hazard safety distances from hydrogen jet fires are often based on models previously developed for hydrocarbon jet fires. Their capability of predicting radiative heat fluxes from hydrogen jet fires has often only been validated against small-scale or medium-scale jet flame experiments. However large-scale hydrogen jet fire experiments have shown that thermal radiation levels can be significantly higher than one might expect from extrapolation of experience on smaller hydrogen flames. Here two large-scale horizontal hydrogen jet fires (from a 20.9 mm and a 52.5 mm diameter release respectively) have been modelled and simulated with the advanced industrial CFD code KAMELEON FIREEX KFX® based on the Eddy Dissipation Concept by Magnussen for turbulent combustion modelling. The modelling of the high-pressure hydrogen gas releases is based on a pseudo-source concept using real-gas thermodynamic data for hydrogen. The discrete transport method of Lockwood and Shah is used to calculate the radiative heat transfer and radiative properties of water vapour are modelled according to Leckner. The predicted thermal radiation is compared to data from large-scale hydrogen jet fire experiments and discussed. This work was conducted as part of a KFX-H2 R&D project supported by the Research Council of Norway.
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.
Synthetic Natural Gas Production from CO2 and Renewable H2: Towards Large-scale Production of Ni–Fe Alloy Catalysts for Commercialization
Apr 2020
Publication
Synthetic natural gas (SNG) is one of the promising energy carriers for the excessive electricity generated from variable renewable energy sources. SNG production from renewable H2 and CO2 via catalytic CO2 methanation has gained much attention since CO2 emissions could be simultaneously reduced. In this study Ni–Fe/(MgAl)Ox alloy catalysts for CO2 methanation were prepared via hydrotalcite precursors using a rapid coprecipitation method. The effect of total metal concentration on the physicochemical properties and catalytic behavior was investigated. Upon calcination the catalysts showed high specific surface area of above 230 m2 g−1. Small particle sizes of about 5 nm were obtained for all catalysts even though the produced catalyst amount was increased by 10 times. The catalysts exhibited excellent space-time yield under very high gas space velocity (34000 h−1) irrespective of the metal concentration. The CO2 conversions reached 73–79% at 300 °C and CH4 selectivities were at 93–95%. Therefore we demonstrated the potential of large-scale production of earth-abundant Ni–Fe based catalysts for CO2 methanation and the Power-to-Gas technology.
Gas Switching Reforming for Flexible Power and Hydrogen Production to Balance Variable Renewables
May 2019
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.
Expectations, Attitudes, and Preferences Regarding Support and Purchase of Eco-friendly Fuel Vehicles
Apr 2019
Publication
This study analyses public expectations attitudes and preferences to support and purchase eco-friendly fuel vehicles. The study used a telephone survey of a sample of residents in Greater Stavanger Norway. Two cluster analyses were conducted to group the individuals based on expectations and attitudes toward eco-friendly fuel vehicles. In addition two multivariate analyses were performed to explore the determinants of support and willingness to purchase eco-friendly fuel vehicles. The study found three components of expectation to support eco-friendly fuel vehicles namely cost comfort and safety. The analysis further found four components to explain attitudes to support eco-friendly fuel vehicles: personal norm pro-technology awareness of priority and environmental degradation. Multivariate analyses confirmed that age gender and the number of cars in the household are likely to influence public preferences to support and purchase eco-friendly fuel vehicles. The results reveal that individuals tend to support the eco-friendly vehicles when the technologies meet their expectations towards cost and safety but the cost expectation is the significant factor that results in the decision to purchase the eco-friendly vehicles. The study also found that the pro-technology attitude has influenced the propensity to support and purchase the eco-friendly fuel vehicles.
Techno-economic Assessment of Hydrogen Production from Seawater
Nov 2022
Publication
Population growth and the expansion of industries have increased energy demand and the use of fossil fuels as an energy source resulting in release of greenhouse gases (GHG) and increased air pollution. Countries are therefore looking for alternatives to fossil fuels for energy generation. Using hydrogen as an energy carrier is one of the most promising alternatives to replace fossil fuels in electricity generation. It is therefore essential to know how hydrogen is produced. Hydrogen can be produced by splitting the water molecules in an electrolyser using the abondand water resources which are covering around ⅔ of the Earth's surface. Electrolysers however require high-quality water with conductivity in the range of 0.1–1 μS/cm. In January 2018 there were 184 offshore oil and gas rigs in the North Sea which may be excellent sites for hydrogen production from seawater. The hydrogen production process reported in this paper is based on a proton exchange membrane (PEM) electrolyser with an input flow rate of 300 L/h. A financially optimal system for producing demineralized water from seawater with conductivity in the range of 0.1–1 μS/cm as the input for electrolyser by WAVE (Water Application Value Engine) design software was studied. The costs of producing hydrogen using the optimised system was calculated to be US$3.51/kg H2. The best option for low-cost power generation using renewable resources such as photovoltaic (PV) devices wind turbines as well as electricity from the grid was assessed considering the location of the case considered. All calculations were based on assumption of existing cable from the grid to the offshore meaning that the cost of cables and distribution infrastructure were not considered. Models were created using HOMER Pro (Hybrid Optimisation of Multiple Energy Resources) software to optimise the microgrids and the distributed energy resources under the assumption of a nominal discount rate inflation rate project lifetime and CO2 tax in Norway. Eight different scenarios were examined using HOMER Pro and the main findings being as follows:<br/>The cost of producing water with quality required by the electrolyser is low compared with the cost of electricity for operation of the electrolyser and therefore has little effect on the total cost of hydrogen production (less than 1%).<br/>The optimal solution was shown to be electricity from the grid which has the lowest levelised cost of energy (LCOE) of the options considered. The hydrogen production cost using electricity from the grid was about US$ 5/kg H2.<br/>Grid based electricity resulted in the lowest hydrogen production cost even when costs for CO2 emissions in Norway that will start to apply in 2025 was considered being approximately US$7.7/kg H2.<br/>From economical point of view wind energy was found to be a more economical than solar.
Continuum Level Simulation of the Grain Size and Misorientation Effects on Hydrogen Embrittlement in Nickel
Jul 2016
Publication
This paper addresses the size and misorientation effects on hydrogen embrittlement of a four grain nickel aggregate. The grain interior is modelled with orthotropic elasticity and the grain boundary with cohesive zone technique. The grain misorientation angle is parameterized by fixing the lower grains and rotating the upper grains about the out-of-plane axis. The hydrogen effect is accounted for via the three-step hydrogen informed cohesive zone simulation. The grain misorientation exerts an obvious weakening effect on the ultimate strength of the nickel aggregate which reaches its peak at misorientation angles around 20◦ but such effect becomes less pronounced in the case with a pre-crack. The misorientation could induce size effect in the otherwise size independent case without a pre-crack. The contribution of misorientation to the size effect is negligible compare to that caused by the existence of a pre-crack. These findings indicate that the misorientation effect in cases with a deep pre-crack is weaker than expected in shallow-pre-crack situations. Most of these conclusions hold for the hydrogen charging situation except that the ultimate strength is lowered in all the sub-cases due to hydrogen embrittlement. Interestingly it is observed that the size effect becomes less pronounced with hydrogen taken into account which is caused by the fact that hydrogen takes more time to reach the failure initiation site in larger grains.
Blind-prediction: Estimating the Consequences of Vented Hydrogen Deflagrations for Homogeneous Mixtures in a 20-foot ISO Container
Sep 2017
Publication
Trygve Skjold,
Helene Hisken,
Sunil Lakshmipathy,
Gordon Atanga,
Marco Carcassi,
Martino Schiavetti,
James R. Stewart,
A. Newton,
James R. Hoyes,
Ilias C. Tolias,
Alexandros G. Venetsanos,
Olav Roald Hansen,
J. Geng,
Asmund Huser,
Sjur Helland,
Romain Jambut,
Ke Ren,
Alexei Kotchourko,
Thomas Jordan,
Jérome Daubech,
Guillaume Lecocq,
Arve Grønsund Hanssen,
Chenthil Kumar,
Laurent Krumenacker,
Simon Jallais,
D. Miller and
Carl Regis Bauwens
This paper summarises the results from a blind-prediction study for models developed for estimating the consequences of vented hydrogen deflagrations. The work is part of the project Improving hydrogen safety for energy applications through pre-normative research on vented deflagrations (HySEA). The scenarios selected for the blind-prediction entailed vented explosions with homogeneous hydrogen-air mixtures in a 20-foot ISO container. The test program included two configurations and six experiments i.e. three repeated tests for each scenario. The comparison between experimental results and model predictions reveals reasonable agreement for some of the models and significant discrepancies for others. It is foreseen that the first blind-prediction study in the HySEA project will motivate developers to improve their models and to update guidelines for users of the models.
Hydrogen Enhanced Fatigue Crack Growth Rates in a Ferritic Fe-3wt%Si Alloy
Dec 2018
Publication
It is well known that ferrous materials can be damaged by absorption of hydrogen. If a sufficient quantity of hydrogen penetrates into the material static fracture and the material's fatigue performances can be affected negatively in particular causing an increase in the material crack growth rates. The latter is often referred as Hydrogen Affected-Fatigue Crack Growth Rate (HA-FCGR). It is therefore of paramount importance to quantify the impact in terms of hydrogen induce fatigue crack growth acceleration in order to determine the life of components exposed to hydrogen and avoid unexpected catastrophic failures. In this study in-situ fatigue crack growth rate testing on Compact Tension (CT) specimens were carried out to determine the fatigue crack growth behaviour for a Fe-3 wt%Si alloy and X70 pipeline steel. Tests were carried out in two environmental conditions i.e. laboratory air and in-situ electrochemically charged hydrogen and different mechanical conditions in terms of load ratio (R = 0.1 and R = 0.5 for the Fe-3 wt%Si R = 0.1 for the X70 steel) and test frequency (f = 0.1 Hz 1 Hz and 10 Hz) were adopted under electrochemically charged hydrogen conditions. The results show a clear detrimental effect of H for the specimens tested in hydrogen when compared to the specimens tested in air for both materials and that the impact of hydrogen is test frequency-dependent: the hydrogen induced acceleration is more prominent as the frequency is decreased. Post-mortem surface investigations consistently relate the global crack growth acceleration to a shift from transgranular to Quasi-cleavage fracture mechanism. Despite such consistency the acceleration factor strongly depends on the material: Fe-3wt%Si features acceleration up to 1000 times while X70 accelerates up to 76 times when compare to the material fatigue crack growth rate recorded in air. Observation of the deformation activities in the crack wake in relation to the transition into hydrogen accelerated regime in fatigue crack growth show a tendency toward restricted plastic activity in presence of hydrogen.
The Influence of H2 Safety Research on Relevant Risk Assessment
Sep 2019
Publication
Hydrogen is a valuable option of clean fuel to keep the global temperature rise below 2°C. However one of the main barriers in its transport and use is to ensure safety levels that are comparable with traditional fuels. In particular liquid hydrogen accidents may not be fully understood (yet) and excluded by relevant risk assessment. For instance as hydrogen is cryogenically liquefied to increase its energy density during transport Boiling Liquid Expanding Vapor Explosions (BLEVE) is a potential and critical event that is important addressing in the hazard identification phase. Two past BLEVE accidents involving liquid hydrogen support such thesis. For this reason results from consequence analysis of hydrogen BLEVE will not only improve the understanding of the related physical phenomenon but also influence future risk assessment studies. This study aims to show the extent of consequence analysis influence on overall quantitative risk assessment of hydrogen technologies and propose a systematic approach for integration of overall results. The Dynamic Procedure for Atypical Scenario Identification (DyPASI) is used for this purpose. The work specifically focuses on consequence models that are originally developed for other substances and adapted for liquid hydrogen. Particular attention is given to the parameters affecting the magnitude of the accident as currently investigated by a number of research projects on hydrogen safety worldwide. A representative example of consequence analysis for liquid hydrogen release is employed in this study. Critical conditions detected by the numerical simulation models are accurately identified and considered for subsequent update of the overall system risk assessment.
Comparing Exergy Losses and Evaluating the Potential of Catalyst-filled Plate-fin and Spiral-wound Heat Exchangers in a Large-scale Claude Hydrogen Liquefaction Process
Jan 2020
Publication
Detailed heat exchanger designs are determined by matching intermediate temperatures in a large-scale Claude refrigeration process for liquefaction of hydrogen with a capacity of 125 tons/day. A comparison is made of catalyst filled plate-fin and spiral-wound heat exchangers by use of a flexible and robust modelling framework for multi-stream heat exchangers that incorporates conversion of ortho-to para-hydrogen in the hydrogen feed stream accurate thermophysical models and a distributed resolution of all streams and wall temperatures. Maps of the local exergy destruction in the heat exchangers are presented which enable the identification of several avenues to improve their performances.<br/>The heat exchanger duties vary between 1 and 31 MW and their second law energy efficiencies vary between 72.3% and 96.6%. Due to geometrical constraints imposed by the heat exchanger manufacturers it is necessary to employ between one to four parallel plate-fin heat exchanger modules while it is possible to use single modules in series for the spiral-wound heat exchangers. Due to the lower surface density and heat transfer coefficients in the spiral-wound heat exchangers their weights are 2–14 times higher than those of the plate-fin heat exchangers.<br/>In the first heat exchanger hydrogen feed gas is cooled from ambient temperature to about 120 K by use of a single mixed refrigerant cycle. Here most of the exergy destruction occurs when the high-pressure mixed refrigerant enters the single-phase regime. A dual mixed refrigerant or a cascade process holds the potential to remove a large part of this exergy destruction and improve the efficiency. In many of the heat exchangers uneven local exergy destruction reveals a potential for further optimization of geometrical parameters in combination with process parameters and constraints.<br/>The framework presented makes it possible to compare different sources of exergy destruction on equal terms and enables a qualified specification on the maximum allowed pressure drops in the streams. The mole fraction of para-hydrogen is significantly closer to the equilibrium composition through the entire process for the spiral-wound heat exchangers due to the longer residence time. This reduces the exergy destruction from the conversion of ortho-hydrogen and results in a higher outlet mole fraction of para-hydrogen from the process.<br/>Because of the higher surface densities of the plate-fin heat exchangers they are the preferred technology for hydrogen liquefaction unless a higher conversion to heat exchange ratio is desired.
The New Oil? The Geopolitics and International Governance of Hydrogen
Jun 2020
Publication
While most hydrogen research focuses on the technical and cost hurdles to a full-scale hydrogen economy little consideration has been given to the geopolitical drivers and consequences of hydrogen developments. The technologies and infrastructures underpinning a hydrogen economy can take markedly different forms and the choice over which pathway to take is the object of competition between different stakeholders and countries. Over time cross-border maritime trade in hydrogen has the potential to fundamentally redraw the geography of global energy trade create a new class of energy exporters and reshape geopolitical relations and alliances between countries. International governance and investments to scale up hydrogen value chains could reduce the risk of market fragmentation carbon lock-in and intensified geo-economic rivalry.
Techno-economic calculations of small-scale hydrogen supply systems for zero emission transport in Norway
Jun 2019
Publication
In Norway where nearly 100% of the power is hydroelectric it is natural to consider water electrolysis as the main production method of hydrogen for zero-emission transport. In a start-up market with low demand for hydrogen one may find that small-scale WE-based hydrogen production is more cost-efficient than large-scale production because of the potential to reach a high number of operating hours at rated capacity and high overall system utilization rate. Two case studies addressing the levelized costs of hydrogen in local supply systems have been evaluated in the present work: (1) Hydrogen production at a small-scale hydroelectric power plant (with and without on-site refuelling) and (2) Small hydrogen refuelling station for trucks (with and without on-site hydrogen production). The techno-economic calculations of the two case studies show that the levelized hydrogen refuelling cost at the small-scale hydroelectric power plant (with a local station) will be 141 NOK/kg while a fleet of 5 fuel cell trucks will be able to refuel hydrogen at a cost of 58 NOK/kg at a station with on-site production or 71 NOK/kg at a station based on delivered hydrogen. The study shows that there is a relatively good business case for local water electrolysis and supply of hydrogen to captive fleets of trucks in Norway particularly if the size of the fleet is sufficiently large to justify the installation of a relatively large water electrolyzer system (economies of scale). The ideal concept would be a large fleet of heavy-duty vehicles (with a high total hydrogen demand) and a refuelling station with nearly 100% utilization of the installed hydrogen production capacity.
Opportunities and Challenges for Thermally Driven Hydrogen Production Using Reverse Electrodialysis System
Jul 2019
Publication
Ongoing and emerging renewable energy technologies mainly produce electric energy and intermittent power. As the energy economy relies on banking energy there is a rising need for chemically stored energy. We propose heat driven reverse electrodialysis (RED) technology with ammonium bicarbonate (AmB) as salt for producing hydrogen. The study provides the authors’ perspective on the commercial feasibility of AmB RED for low grade waste heat (333 K–413 K) to electricity conversion system. This is to our best of knowledge the only existing study to evaluate levelized cost of energy of a RED system for hydrogen production. The economic assessment includes a parametric study and a scenario analysis of AmB RED system for hydrogen production. The impact of various parameters including membrane cost membrane lifetime cost of heating inter-membrane distance and residence time are studied. The results from the economic study suggests RED system with membrane cost less than 2.86 €/m2 membrane life more than 7 years and a production rate of 1.19 mol/m2/h or more are necessary for RED to be economically competitive with the current renewable technologies for hydrogen production. Further salt solubility residence time and inter-membrane distance were found to have impact on levelized cost of hydrogen LCH. In the present state use of ammonium bicarbonate in RED system for hydrogen production is uneconomical. This may be attributed to high membrane cost low (0.72 mol/m2/h) hydrogen production rate and large (1281436 m2) membrane area requirements. There are three scenarios presented the present scenario market scenario and future scenario. From the scenario analysis it is clear that membrane cost and membrane life in present scenario controls the levelized cost of hydrogen. In market scenario and future scenario the hydrogen production rate (which depends on membrane properties inter-membrane distance etc.) the cost of regeneration system and the cost of heating controls the levelized cost of hydrogen. For a thermally driven RED system to be economically feasible the membrane cost not more than 20 €/m2; hydrogen production rate of 3.7 mol/m2/h or higher and cost of heating not more than 0.03 €/kWh for low grade waste heat to hydrogen production.
The Norwegian Government’s Hydrogen Strategy - Towards a Low Emission Society
Jun 2020
Publication
On Wednesday 3rd of June 2020 Norwegian Minister for Petroleum and Energy Tina Bru and Minister for Climate and Environment Sveinung Rotevatn presented the Norwegian government's hydrogen strategy.<br/>The strategy sets the course for the government's efforts to stimulate development of hydrogen-related technologies. Hydrogen as an energy carrier can contribute to reduction of greenhouse gases and create value for the Norwegian business sector. The government wishes to prioritise efforts in areas where Norway Norwegian enterprises and technology clusters may influence the development of hydrogen related technologies and where there are opportunites for increased value creation and green growth. For hydrogen to be a low-carbon or emission-free energy carrier it must be produced with no or low emissions such as through water electrolysis with renewable electricity or from natural gas with carbon capture and storage.<br/>Today technology maturity and high costs represent barriers for increased use of hydrogen especially in the transport sector and as feedstock in parts of industry. If hydrogen and hydrogen-based solutions such as ammonia are to be used in new areas both the technology and the solutions must become more mature. In this respect further technology development will be vital.
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