Norway
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.
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