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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.
Vented Explosion of Hydrogen/Air Mixtures: Influence of Vent Cover and Stratification
Sep 2017
Publication
Explosion venting is a prevention/mitigation solution widely used in the process industry to protect indoor equipment or buildings from excessive internal pressure caused by an accidental explosion. Vented explosions are widely investigated in the literature for various geometries hydrogen/air concentrations ignition positions initial turbulence etc. In real situations the vents are normally covered by a vent panel. In the case of an indoor leakage the hydrogen/air cloud will be stratified rather than homogeneous. Nowadays there is a lack in understanding about the vented explosion of stratified clouds and about the influence of vent cover inertia on the internal overpressure. This paper aims at shedding light on these aspects by means of experimental investigation of vented hydrogen/air deflagration using an experimental facility of 1m3 and via numerical simulations using the computational fluid dynamics (CFD) code FLACS
A Methodology for Assessing the Sustainability of Hydrogen Production from Solid Fuels
May 2010
Publication
A methodology for assessing the sustainability of hydrogen production using solid fuels is introduced in which three sustainability dimensions (ecological sociological and technological) are considered along with ten indicators for each dimension. Values for each indicator are assigned on a 10-point scale based on a high of 1 and a low of 0 depending on the characteristic of the criteria associated with each element or process utilizing data reported in the literature. An illustrative example is presented to compare two solid fuels for hydrogen production: coal and biomass. The results suggest that qualitative sustainability indicators can be reasonably defined based on evaluations of system feasibility and that adequate flexibility and comprehensiveness is provided through the use of ten indicators for each of the dimensions for every process or element involved in hydrogen production using solid fuels. Also the assessment index values suggest that biomasses have better sustainability than coals and that it may be advantageous to use coals in combination with biomass to increase their ecological and social sustainability. The sustainability assessment methodology can be made increasingly quantitative and is likely extendable to other energy systems but additional research and development is needed to lead to a more fully developed approach.
Experimental Investigation of Unconfined Spherical and Cylindrical Flame Propagation in Hydrogen-air Mixtures
Sep 2019
Publication
This paper presents results of experimental investigations on spherical and cylindrical flame propagation in pre-mixed H2/air-mixtures in unconfined and semi-confined geometries. The experiments were performed in a facility consisting of two transparent solid walls with 1 m2 area and four weak side walls made from thin plastic film. The gap size between the solid walls was varied stepwise from thin layer geometry (6 mm) to cube geometry (1 m). A wide range of H2/air-mixtures with volumetric hydrogen concentrations from 10% to 45% H2 was ignited between the transparent solid walls. The propagating flame front and its structure was observed with a large scale high speed shadow system. Results of spherical and cylindrical flame propagation up to a radius of 0.5 m were analyzed. The presented spherical burning velocity model is used to discuss the self-acceleration phenomena in unconfined and unobstructed pre-mixed H2/air flames.
Removing the Bottleneck on Wind Power Potential to Create Liquid Fuels from Locally Available Biomass
Jun 2021
Publication
In order to reduce global greenhouse gas emissions renewable energy technologies such as wind power and solar photovoltaic power systems have recently become more widespread. However Japan as a nation faces high reliance on imported fossil fuels for electricity generation despite having great potential for further renewable energy development. The focus of this study examines untapped geographical locations in Japan’s northern most prefecture Hokkaido that possess large wind power potential. The possibility of exploiting this potential for the purpose of producing green hydrogen is explored. In particular its integration with a year-round conversion of Kraft lignin into bio-oil from nearby paper pulp mills through a near critical water depolymerization process is examined. The proposed bio-oil and aromatic chemical production as well as the process’ economics are calculated based upon the total available Kraft lignin in Hokkaido including the magnitude of wind power capacity that would be required for producing the necessary hydrogen for such a large-scale process. Green hydrogen integration with other processes in Japan and in other regions is also discussed. Finally the potential benefits and challenges are outlined from an energy policy point-of-view.
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.
Ordered Clustering of Single Atomic Te Vacancies in Atomically Thin PtTe2 Promotes Hydrogen Evolution Catalysis
Apr 2021
Publication
Exposing and stabilizing undercoordinated platinum (Pt) sites and therefore optimizing their adsorption to reactive intermediates offers a desirable strategy to develop highly efficient Pt-based electrocatalysts. However preparation of atomically controllable Pt-based model catalysts to understand the correlation between electronic structure adsorption energy and catalytic properties of atomic Pt sites is still challenging. Herein we report the atomically thin two-dimensional PtTe2 nanosheets with well-dispersed single atomic Te vacancies (Te-SAVs) and atomically well-defined undercoordinated Pt sites as a model electrocatalyst. A controlled thermal treatment drives the migration of the Te-SAVs to form thermodynamically stabilized ordered Te-SAV clusters which decreases both the density of states of undercoordinated Pt sites around the Fermi level and the interacting orbital volume of Pt sites. As a result the binding strength of atomically defined Pt active sites to H intermediates is effectively reduced which renders PtTe2 nanosheets highly active and stable in hydrogen evolution reaction.
Analysis of Hydrogen-Induced Changes in the Cyclic Deformation Behaviour of AISI 300–Series Austenitic Stainless Steels Using Cyclic Indentation Testing
Jun 2021
Publication
The locally occurring mechanisms of hydrogen embrittlement significantly influence the fatigue behaviour of a material which was shown in previous research on two different AISI 300-series austenitic stainless steels with different austenite stabilities. In this preliminary work an enhanced fatigue crack growth as well as changes in crack initiation sites and morphology caused by hydrogen were observed. To further analyze the results obtained in this previous research in the present work the local cyclic deformation behaviour of the material volume was analyzed by using cyclic indentation testing. Moreover these results were correlated to the local dislocation structures obtained with transmission electron microscopy (TEM) in the vicinity of fatigue cracks. The cyclic indentation tests show a decreased cyclic hardening potential as well as an increased dislocation mobility for the conditions precharged with hydrogen which correlates to the TEM analysis revealing courser dislocation cells in the vicinity of the fatigue crack tip. Consequently the presented results indicate that the hydrogen enhanced localized plasticity (HELP) mechanism leads to accelerated crack growth and change in crack morphology for the materials investigated. In summary the cyclic indentation tests show a high potential for an analysis of the effects of hydrogen on the local cyclic deformation behaviour.
Thermal Radiation from Cryogenic Hydrogen Jet Fires
Sep 2017
Publication
The thermal hazards from ignited under-expanded cryogenic releases are not yet fully understood and reliable predictive tools are missing. This study aims at validation of a CFD model to simulate flame length and radiative heat flux for cryogenic hydrogen jet fires. The simulation results are compared against the experimental data by Sandia National Laboratories on cryogenic hydrogen fires from storage with pressure up to 5 bar abs and temperature in the range 48–82 K. The release source is modelled using the Ulster's notional nozzle theory. The problem is considered as steady-state. Three turbulence models were applied and their performance was compared. The realizable k-ε model showed the best agreement with experimental flame length and radiative heat flux. Therefore it has been employed in the CFD model along with Eddy Dissipation Concept for combustion and Discrete Ordinates (DO) model for radiation. A parametric study has been conducted to assess the effect of selected numerical and physical parameters on the simulations capability to reproduce experimental data. DO model discretisation is shown to strongly affect simulations indicating 10 × 10 as minimum number of angular divisions to provide a convergence. The simulations have shown sensitivity to experimental parameters such as humidity and exhaust system volumetric flow rate highlighting the importance of accurate and extended publication of experimental data to conduct precise numerical studies. The simulations correctly reproduced the radiative heat flux from cryogenic hydrogen jet fire at different locations.
Debunking the Myths of Hydrogen Production and Water Consumption
Dec 2020
Publication
In our factsheet where we debunk 3 myths around hydrogen production and water consumption: electrolysis uses vast amounts of water; electrolysis uses freshwater resources only and electrolysis is bound to create water stress in water-scarce regions.
Life Cycle Assessment of Hydrogen Production and Consumption in an Isolated Territory
Apr 2018
Publication
Hydrogen produced from renewables works as an energy carrier and as energy storage medium and thus hydrogen can help to overcome the intermittency of typical renewable energy sources. However there is no comprehensive environmental performance study of hydrogen production and consumption. In this study detailed cradle to grave life cycle analyses are performed in an isolated territory. The hydrogen is produced on-site by Polymer Electrolyte Membrane (PEM) water electrolysis based on electricity from wind turbines that would otherwise have been curtailed and subsequently transported with gas cylinder by road and ferry. The hydrogen is used to provide electricity and heat through fuel cell stacks as well as hydrogen fuel for fuel cell vehicles. In order to evaluate the environmental impacts related to the hydrogen production and utilisation this work conducts an investigation of the entire life cycle of the described hydrogen production transportation and utilisation. All the processes related to the equipment manufacture operation maintenance and disposal are considered in this study.
A Review on Recent Advances in Hydrogen Energy, Fuel Cell, Biofuel and Fuel Refining via Ultrasound Process Intensification
Mar 2021
Publication
Hydrogen energy is one of the most suitable green substitutes for harmful fossil fuels and has been investigated widely. This review extensively compiles and compares various methodologies used in the production storage and usage of hydrogen. Sonochemistry is an emerging synthesis process and intensification technique adapted for the synthesis of novel materials. It manifests acoustic cavitation phenomena caused by ultrasound where higher rates of reactions occur locally. The review discusses the effectiveness of sonochemical routes in developing fuel cell catalysts fuel refining biofuel production chemical processes for hydrogen production and the physical chemical and electrochemical hydrogen storage techniques. The operational parameters and environmental conditions used during ultrasonication also influence the production rates which have been elucidated in detail. Hence this review's major focus addresses sonochemical methods that can contribute to the technical challenges involved in hydrogen usage for energy.
The Role of the Testing Rate on Small Punch Tests for the Estimation of Fracture Toughness in Hydrogen Embrittlement
Dec 2020
Publication
In this paper different techniques to test notched Small Punch (SPT) samples in fracture conditions in aggressive environments are studied based on the comparison of the micromechanisms at different rates. Pre-embrittled samples subsequently tested in air at rates conventionally employed (0.01 and 0.002 mm/s) are compared to embrittled ones tested in environment at the same rates (0.01 and 0.002 mm/s) and at a very slow rate (5E-5 mm/s). A set of samples tested in environment under a set of constant loads that produce very slow rates completes the experimental results. As a conclusion it is recommended to test SPT notched specimens in environment at very slow rates of around E-6 mm/s when characterizing in Hydrogen Embrittlement (HE) scenarios in order to allow the interaction material-environment to govern the process.
Enhancing Energy Recovery in Form of Biogas, from Vegetable and Fruit Wholesale Markets By-Products and Wastes, with Pretreatments
Jun 2021
Publication
Residues and by-products from vegetables and fruit wholesale markets are suitable for recovery in the form of energy through anaerobic digestion allowing waste recovery and introducing them into the circular economy. This suitability is due to their composition structural characteristics and to the biogas generation process which is stable and without inhibition. However it has been observed that the proportion of methane and the level of degradation of the substrate is low. It is decided to study whether the effect of pretreatments on the substrate is beneficial. Freezing ultrafreezing and lyophilization pretreatments are studied. A characterization of the substrates has been performed the route of action of pretreatment determined and the digestion process studied to calculate the generation of biogas methane hydrogen and the proportions among these. Also a complete analysis of the process has been performed by processing the data with mathematical and statistical methods to obtain disintegration constants and levels of degradation. It has been observed that the three pretreatments have positive effects when increasing the solubility of the substrate increasing porosity and improving the accessibility of microorganisms to the substrate. Generation of gases are greatly increased reaching a methane enrichment of 59.751%. Freezing seems to be the best pretreatment as it increases the biodegradation level the speed of the process and the disintegration constant by 306%.
An Integrated Hydrogen Fuel Cell to Distribution Network System: Challenging and Opportunity for D-STATCOM
Oct 2021
Publication
The electric power industry sector has become increasingly aware of how counterproductive voltage sag affects distribution network systems (DNS). The voltage sag backfires disastrously at the demand load side and affects equipment in DNS. To settle the voltage sag issue this paper achieved its primary purpose to mitigate the voltage sag based on integrating a hydrogen fuel cell (HFC) with the DNS using a distribution static synchronous compensator (D-STATCOM) system. Besides this paper discusses the challenges and opportunities of D-STATCOM in DNS. In this paper using HFC is well-designed modeled and simulated to mitigate the voltage sag in DNS with a positive impact on the environment and an immediate response to the issue of the injection of voltage. Furthermore this modeling and controller are particularly suitable in terms of cost-effectiveness as well as reliability based on the adaptive network fuzzy inference system (ANFIS) fuzzy logic system (FLC) and proportional–integral (P-I). The effectiveness of the MATLAB simulation is confirmed by implementing the system and carrying out a DNS connection obtaining efficiencies over 94.5% at three-phase fault for values of injection voltage in HFC D-STATCOM using a P-I controller. Moreover the HFC D-STATCOM using FLC proved capable of supporting the network by 97.00%. The HFC D-STATCOM based ANFIS proved capable of supporting the network by 98.00% in the DNS.
Industrial Decarbonisation Policies for a UK Net-Zero Target
Dec 2020
Publication
To inform our Sixth Carbon Budget advice the Climate Change Committee (CCC) asked the University of Leeds to undertake independent research to evaluate which policies (and combinations of policies) would enable industrial decarbonisation in line with the UK’s net zero target without inducing carbon leakage. The research focused on policies applicable to the manufacturing sector but with some consideration also given to the policies required to decarbonise the Fossil Fuel Production and Supply and Non-Road Mobile Machinery sectors. This report:
Sets out a comprehensive review of existing policies;
The paper can be downloaded from the CCC website
Sets out a comprehensive review of existing policies;
- Identifies future policy mechanisms that address key challenges in decarbonising industry;
- Explores how combinations of policies might work together strategically in the form of ‘policy packages’ and how these packages might evolve over the period to 2050;
- Evaluates a series of illustrative policy packages and considers any complementary policies required to minimise carbon leakage and deliver ‘just’ industrial decarbonisation.
- The findings were developed through a combination of literature review and extensive stakeholder engagement with industry government and academic experts.
The paper can be downloaded from the CCC website
A Study on the Joule-Thomson Effect of During Filling Hydrogen in High Pressure Tank
Dec 2022
Publication
With the development of the hydrogen fuel cell automobile industry higher requirements are put forward for the construction of hydrogen energy infrastructure the matching of parameters and the control strategy of hydrogen filling rate in the hydrogenation process of hydrogenation station. Fuel for hydrogen fuel cell vehicles comes from hydrogen refueling stations. At present the technological difficulty of hydrogenation is mainly reflected in the balanced treatment of reducing the temperature rise of hydrogen and shortening the filling time during the fast filling process. The Joule-Thomson (JT) effect occurs when high-pressure hydrogen gas passes through the valve assembly which may lead to an increase in hydrogen temperature. The JT effect is generally reflected by the JT coefficient. According to the high pressure hydrogen in the pressure reducing valve the corresponding JT coefficients were calculated by using the VDW equation RK equation SRK equation and PR equation and the expression of JT effect temperature rise was deduced which revealed the hydrogen temperature variation law in the process of reducing pressure. Make clear the relationship between charging parameters and temperature rise in the process of decompression; the flow and thermal characteristics of hydrogen in the process of decompression are revealed. This study provides basic support for experts to achieve throttling optimization of related pressure control system in hydrogen industry
Impact of Hydrogen Fuel for CO2 Emission Reduction in Power Generation Sector in Japan
Jun 2017
Publication
Japan’s energy consumption derives mostly from fossil fuels which are un-secure and release a much greenhouse gas emissions. To meet goals of reducing GHG hydrogen gas can be utilized in power generation in hydrogen fired and firing / co-combustion power plants. This paper analyses the impact of hydrogen in the power generation sector using the MARKAL-TIMES Japan optimization model framework. Two models are used: a base scenario without hydrogen and hydrogen scenario in which hydrogen is supplied from 2020 onwards. In the hydrogen scenario other processes which are normally supplied by natural gas are reduced because the gas is instead used to generate power. Adding hydrogen to the energy supply leads to a decrease in projected use of fossil fuels. The hydrogen scenario produces fewer emissions than the base scenario; by 2050 the hydrogen scenario’s estimated 388 metric tons of CO2 emissions is over 250 tons less than the base scenario’s emissions of 588 metric tons.
Power-to-liquid via Synthesis of Methanol, DME or Fischer–Tropsch-fuels: A Review
Jul 2020
Publication
The conversion of H2 and CO2 to liquid fuels via Power-to-Liquid (PtL) processes is gaining attention. With their higher energy densities compared to gases the use of synthetic liquid fuels is particularly interesting in hard-to-abate sectors for which decarbonisation is difficult. However PtL poses new challenges for the synthesis: away from syngas-based continuously run large-scale plants towards more flexible small-scale concepts with direct CO2-utilisation. This review provides an overview of state of the art synthesis technologies as well as current developments and pilot plants for the most prominent PtL routes for methanol DME and Fischer–Tropsch-fuels. It should serve as a benchmark for future concepts guide researchers in their process development and allow a technological evaluation of alternative reactor designs. In the case of power-to-methanol and power-to-FT-fuels several pilot plants have been realised and the first commercial scale plants are planned or already in operation. In comparison power-to-DME is much less investigated and in an earlier stage of development. For methanol the direct CO2 hydrogenation offers advantages through less by-product formation and lower heat development. However increased water formation and lower equilibrium conversion necessitate new catalysts and reactor designs. While DME synthesis offers benefits with regards to energy efficiency operational experience from laboratory tests and pilot plants is still missing. Furthermore four major process routes for power-to-DME are possible requiring additional research to determine the optimal concept. In the case of Fischer–Tropsch synthesis catalysts for direct CO2 utilisation are still in an early stage. Consequently today’s Fischer–Tropsch-based PtL requires a shift to syngas benefiting from advances in co-electrolysis and reverse water-gas shift reactor design.
Optimal Synergy between Photovoltaic Panels and Hydrogen Fuel Cells for Green Power Supply of a Green Building—A Case Study
Jun 2021
Publication
Alternative energy resources have a significant function in the performance and decarbonization of power engendering schemes in the building application domain. Additionally “green buildings” play a special role in reducing energy consumption and minimizing CO2 emissions in the building sector. This research article analyzes the performance of alternative primary energy sources (sun and hydrogen) integrated into a hybrid photovoltaic panel/fuel cell system and their optimal synergy to provide green energy for a green building. The study addresses the future hydrogen-based economy which involves the supply of hydrogen as the fuel needed to provide fuel cell energy through a power distribution infrastructure. The objective of this research is to use fuel cells in this field and to investigate their use as a green building energy supply through a hybrid electricity generation system which also uses photovoltaic panels to convert solar energy. The fuel cell hydrogen is supplied through a distribution network in which hydrogen production is outsourced and independent of the power generation system. The case study creates virtual operating conditions for this type of hybrid energy system and simulates its operation over a one-year period. The goal is to demonstrate the role and utility of fuel cells in virtual conditions by analyzing energy and economic performance indicators as well as carbon dioxide emissions. The case study analyzes the optimal synergy between photovoltaic panels and fuel cells for the power supply of a green building. In the simulation an optimally configured hybrid system supplies 100% of the energy to the green building while generating carbon dioxide emissions equal to 11.72% of the average value calculated for a conventional energy system providing similar energy to a standard residential building. Photovoltaic panels account for 32% of the required annual electricity production and the fuel cells generate 68% of the total annual energy output of the system.
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