Production & Supply Chain
Study on Hydrogen from Renewable Resources in the EU
Feb 2016
Publication
Hydrogen can be produced from a broad range of renewable energy sources acting as a unique energy hub providing low or zero emission energy to all energy consuming sectors. Technically and efficiently producing hydrogen from renewable sources is a key enabler for these developments.<br/>Traditionally hydrogen has been produced from fossil sources by steam methane reforming of natural gas. At present the technology of choice to produce renewable ‘green’ hydrogen is water electrolysis using renewable electricity. The FCH JU has been supporting research and development of electrolyser technology and application projects aiming to increase the energy efficiency of electrolytic hydrogen production from renewable sources and to reduce costs.<br/>This study complements these activities by focusing on renewable hydrogen generation other than electrolysis. In this report these alternative hydrogen generation technologies are described characterized by their technical capabilities maturity and economic performance and assessed for their future potential.<br/>A methodology has been devised to first identify and structure a set of relevant green hydrogen pathways (eleven pathways depicted in the figure below) analyse them at a level of detail allowing a selection of those technologies which fit into and promise early commercialization in the framework of FCH 2 JU’s funding program.<br/>These originally proposed eleven pathways use solar thermal energy sunlight or biomass as major energy input.
Photocatalytic Hydrogen Production by Biomimetic Indium Sulfide Using Mimosa Pudica Leaves as Template
Jan 2019
Publication
Biomimetic sulfur-deficient indium sulfide (In2.77S4) was synthesized by a template-assisted hydrothermal method using leaves of Mimosa pudica as a template for the first time. The effect of this template in modifying the morphology of the semiconductor particles was determined by physicochemical characterization revealing an increase in surface area decrease in microsphere size and pore size and an increase in pore volume density in samples synthesized with the template. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of organic sulfur (Ssingle bondO/Ssingle bondC/Ssingle bondH) and sulfur oxide species (single bondSO2 SO32− SO42−) at the surface of the indium sulfide in samples synthesized with the template. Biomimetic indium sulfide also showed significant amounts of Fe introduced as a contaminant present on the Mimosa pudica leaves. The presence of these sulfur and iron species favors the photocatalytic activity for hydrogen production by their acting as a sacrificial reagent and promoting water oxidation on the surface of the templated particles respectively. The photocatalytic hydrogen production rates over optimally-prepared biomimetic indium sulfide and indium sulfide synthesized without the organic template were 73 and 22 μmol g−1 respectively indicating an improvement by a factor of three in the templated sample.
Optimization of Geothermal- and Solar-driven Clean Electricity and Hydrogen Production Multi-generation Systems to Address the Energy Nexus
Jan 2022
Publication
Given the limited sources of fossil fuels mankind should find new ways to meet its energy demands. In this regard geothermal and solar energy are acknowledged as reliable safe promising and clean means for this purpose. In this research study a comparative analysis is applied on geothermal and solar-driven multi-generation systems for clean electricity and hydrogen production through energy and exergy assessments. The system consists of an organic Rankine cycle a proton electrolyte membrane electrolyzer and a thermoelectric generator subsystem. The Engineering Equation Solver software has been utilized in order to model the system and obtain the output contours sensitivity analysis and exergy destruction. The results were calculated considering the ambient temperature of Bandar Abbas city as a case study considering the geothermal system due to better performance in comparison to the solar system. According to the sensitivity analysis the turbine efficiency evaporator inlet temperature thermoelectric generator suitability criterion pump efficiency and evaporator inlet mass flow rate are the most influential parameters. Also the exergy analysis showed that the utmost system's exergy destruction is pertinent to the evaporator and the least is related to the pump. In addition the system produces 352816 kWh and 174.913 kg of electrical power and hydrogen during one year.
Production of Hydrogen and Methane from Lignocellulose Waste by Fermentation. A Review of Chemical Pretreatment for Enhancing the Efficiency of the Digestion Process
May 2020
Publication
In Poland lignocellulose wastes constitute about 43% of municipal waste (∼4 417 Gg). Anaerobic and/or dark fermentation are sustainable methods of lignocellulosic waste-management and contribute greatly to ever increasing demand for energy and products. This paper presents the results of the theoretical potential of methane and hydrogen yields from lignocellulosic wastes. Also state-of-the-art methods in the field of lignocellulose fermentation as well as its development and pretreatment are discussed. The main reason for applying pretreatment is the decomposition (decrystallization) of cellulose and hemicellulose and cleavage of polymers into monomers which may be more easily digested by bacteria in DF and AD fermentation processes. At current price levels the cheapest methods are basic and acidic pretreatments. Acidic pretreatment is very efficient (especially using sulfuric acids) solubilizing up to 80% of lignocellulose but strong acids produce inhibitors and are highly corrosive. Alkaline pretreatment is a competitive and even more efficient (>80%) method to acidic pretreatment especially for some rigid materials that acid cannot solubilize. Oxidative pretreatment is usually expensive but can support the sacharisation process by either alkaline or acidic methods; in the case of NMMO efficiency reaching 82%. Ion-liquid pretreatment is selective (almost 100% sacharisation) but very costly and is too expensive for hydrogen production. The last methods can be profitable if some valuable by-products results. An efficient chemical pretreatment should be preceded by physical comminution e.g. mechanical which is the cheapest one.
FPGA-Based Implementation of an Optimization Algorithm to Maximize the Productivity of a Microbial Electrolysis Cell
Jun 2021
Publication
In this work the design of the hardware architecture to implement an algorithm for optimizing the Hydrogen Productivity Rate (HPR) in a Microbial Electrolysis Cell (MEC) is presented. The HPR in the MEC is maximized by the golden section search algorithm in conjunction with a super-twisting controller. The development of the digital architecture in the implementation step of the optimization algorithm was developed in the Very High Description Language (VHDL) and synthesized in a Field Programmable Gate Array (FPGA). Numerical simulations demonstrated the feasibility of the proposed optimization strategy embedded in an FPGA Cyclone II. Results showed that only.
Development of an Operation Strategy for Hydrogen Production Using Solar PV Energy Based on Fluid Dynamic Aspects
Apr 2017
Publication
Alkaline water electrolysis powered by renewable energy sources is one of the most promising strategies for environmentally friendly hydrogen production. However wind and solar energy sources are highly dependent on weather conditions. As a result power fluctuations affect the electrolyzer and cause several negative effects. Considering these limiting effects which reduce the water electrolysis efficiency a novel operation strategy is proposed in this study. It is based on pumping the electrolyte according to the current density supplied by a solar PV module in order to achieve the suitable fluid dynamics conditions in an electrolysis cell. To this aim a mathematical model including the influence of electrode-membrane distance temperature and electrolyte flow rate has been developed and used as optimization tool. The obtained results confirm the convenience of the selected strategy especially when the electrolyzer is powered by renewable energies.
Layered Transition Metal Selenophosphites for Visible Light Photoelectrochemical Production of Hydrogen
Jun 2021
Publication
The growing consumption of global energy has posed serious challenges to environmental protection and energy supplies. A promising solution is via introducing clean and sustainable energy sources including photoelectrochemical hydrogen fuel production. 2D materials such as transition metal trichalcogenphosphites (MPCh3) are gaining more and more interest for their potential as photocatalysts. Crystals of transition metal selenophosphites namely MnPSe3 FePSe3 and ZnPSe3 were tested as photocatalysts for the hydrogen evolution reaction (HER). ZnPSe3 is the one that exhibited the lowest overpotential and the higher response to the light during photocurrent experiments in acidic media. For this reason among the crystals in this work it is the most promising for the photocatalyzed production of hydrogen.
Enhanced Hydrogen Generation from Hydrolysis of MgLi Doped with Expanded Graphite
Apr 2021
Publication
Hydrolysis of Mg-based materials is considered as a potential means of safe and convenient real-time control of H2 release enabling efficient loading discharge and utilization of hydrogen in portable electronic devices. At present work the hydrogen generation properties of MgLi-graphite composites were evaluated for the first time. The MgLi-graphite composites with different doping amounts of expanded graphite (abbreviated as EG hereinafter) were synthesized through ball milling and the hydrogen behaviors of the composites were investigated in chloride solutions. Among the above doping systems the 10 wt% EG-doped MgLi exhibited the best hydrogen performance in MgCl2 solutions. In particular the 22 h-milled MgLi-10 wt% EG composites possessed both desirable hydrogen conversion and rapid reaction kinetics delivering a hydrogen yield of 966 mL H2 g−1 within merely 2 min and a maximum hydrogen generation rate of 1147 mL H2 min−1 g−1 as opposed to the sluggish kinetics in the EG-free composites. Moreover the EG-doped MgLi showed superior air-stable ability even under a 75 RH% ambient atmosphere. For example the 22 h-milled MgLi-10 wt% EG composites held a fuel conversion of 89% after air exposure for 72 h rendering it an advantage for Mg-based materials to safely store and transfer in practical applications. The similar favorable hydrogen performance of MgLi-EG composites in (simulate) seawater may shed light on future development of hydrogen generation technologies.
A Direct Synthesis of Platinum/Nickel Co-catalysts on Titanium Dioxide Nanotube Surface from Hydrometallurgical-type Process Streams
Aug 2018
Publication
Solutions that simulate hydrometallurgical base metal process streams with high nickel (Ni) and minor platinum (Pt) concentrations were used to create Pt/Ni nanoparticles on TiO2 nanotube surfaces. For this electrochemical deposition – redox replacement (EDRR) was used that also allowed to control the nanoparticle size density and Pt/Ni content of the deposited nanoparticles. The Pt/Ni nanoparticle decorated titanium dioxide nanotubes (TiO2 nanotubes) become strongly activated for photocatalytic hydrogen (H2) evolution. Moreover EDRR facilitates nanoparticle formation without the need for any additional chemicals and is more effective than electrodeposition alone. Actually a 10000-time enrichment level of Pt took place on the TiO2 surface when compared to Pt content in the solution with the EDRR method. The results show that hydrometallurgical streams offer great potential as an alternative raw material source for industrial catalyst production when coupled with redox replacement electrochemistry.
Acorn: Developing Full-chain Industrial Carbon Capture and Storage in a Resource- and Infrastructure-rich Hydrocarbon Province
Jun 2019
Publication
Juan Alcalde,
Niklas Heinemann,
Leslie Mabon,
Richard H. Worden,
Heleen de Coninck,
Hazel Robertson,
Marko Maver,
Saeed Ghanbari,
Floris Swennenhuis,
Indira Mann,
Tiana Walker,
Sam Gomersal,
Clare E. Bond,
Michael J. Allen,
Stuart Haszeldine,
Alan James,
Eric J. Mackay,
Peter A. Brownsort,
Daniel R. Faulkner and
Steve Murphy
Research to date has identified cost and lack of support from stakeholders as two key barriers to the development of a carbon dioxide capture and storage (CCS) industry that is capable of effectively mitigating climate change. This paper responds to these challenges through systematic evaluation of the research and development process for the Acorn CCS project a project designed to develop a scalable full-chain CCS project on the north-east coast of the UK. Through assessment of Acorn's publicly-available outputs we identify strategies which may help to enhance the viability of early-stage CCS projects. Initial capital costs can be minimised by infrastructure re-use particularly pipelines and by re-use of data describing the subsurface acquired during oil and gas exploration activity. Also development of the project in separate stages of activity (e.g. different phases of infrastructure re-use and investment into new infrastructure) enables cost reduction for future build-out phases. Additionally engagement of regional-level policy makers may help to build stakeholder support by situating CCS within regional decarbonisation narratives. We argue that these insights may be translated to general objectives for any CCS project sharing similar characteristics such as legacy infrastructure industrial clusters and an involved stakeholder-base that is engaged with the fossil fuel industry.
Assessment of Hydrogen Direct Reduction for Fossil-free Steelmaking
Aug 2018
Publication
Climate policy objectives require zero emissions across all sectors including steelmaking. The fundamental process changes needed for reaching this target are yet relatively unexplored. In this paper we propose and assess a potential design for a fossil-free steelmaking process based on direct reduction of iron ore with hydrogen. We show that hydrogen direct reduction steelmaking needs 3.48 MWh of electricity per tonne of liquid steel mainly for the electrolyser hydrogen production. If renewable electricity is used the process will have essentially zero emissions. Total production costs are in the range of 361–640 EUR per tonne of steel and are highly sensitive to the electricity price and the amount of scrap used. Hydrogen direct reduction becomes cost competitive with an integrated steel plant at a carbon price of 34–68 EUR per tonne CO2 and electricity costs of 40 EUR/MWh. A key feature of the process is flexibility in production and electricity demand which allows for grid balancing through storage of hydrogen and hot-briquetted iron or variations in the share of scrap used.
Hollow CdS-Based Photocatalysts
Oct 2020
Publication
In recent years photocatalytic technology driven by solar energy has been extensively investigated to ease energy crisis and environmental pollution. Nevertheless efficiency and stability of photocatalysts are still unsatisfactory. To address these issues design of advanced photocatalysts is important. Cadmium sulphide (CdS) nanomaterials are one of the promising photocatalysts. Among them hollow-structured CdS featured with enhanced light absorption ability large surface area abundant active sites for redox reactions and reduced diffusion distance of photogenerated carriers reveals a broad application prospect. Herein main synthetic strategies and formation mechanism of hollow CdS photocatalysts are summarized. Besides we comprehensively discuss the current development of hollow-structured CdS nanomaterials in photocatalytic applications including H2 production CO2 reduction and pollutant degradation. Finally brief conclusions and perspectives on the challenges and future directions for hollow CdS photocatalysts are proposed.
Stronger Together: Multi-annual Variability of Hydrogen Production Supported by Wind Power in Sweden
Mar 2021
Publication
Hydrogen produced from renewable electricity will play an important role in deep decarbonisation of industry. However adding large electrolyser capacities to a low-carbon electricity system also increases the need for additional electricity generation from variable renewable energies. This will require hydrogen production to be variable unless other sources provide sufficient flexibility. Existing sources of flexibility in hydro-thermal systems are hydropower and thermal generation which are both associated with sustainability concerns. In this work we use a dispatch model for the case of Sweden to assess the power system operation with large-scale electrolysers assuming that additional wind power generation matches the electricity demand of hydrogen production on average. We evaluate different scenarios for restricting the flexibility of hydropower and thermal generation and include 29 different weather years to test the impact of variable weather regimes. We show that (a) in all scenarios electrolyser utilisation is above 60% on average (b) the inter-annual variability of hydrogen production is substantial if thermal power is not dispatched for electrolysis and (c) this problem is aggravated if hydropower flexibility is also restricted. Therefore either long-term storage of hydrogen or backup hydrogen sources may be necessary to guarantee continuous hydrogen flows. Large-scale dispatch of electrolysis capacity supported by wind power makes the system more stable if electrolysers ramp down in rare hours of extreme events with low renewable generation. The need for additional backup capacities in a fully renewable electricity system will thus be reduced if wind power and electrolyser operation are combined in the system.
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.
Self-Supported High-Entropy Alloy Electrocatalyst for Highly Efficient H2 Evolution in Acid Condition
Jul 2020
Publication
Developing non-precious catalysts as Pt substitutes for electrochemical hydrogen evolution reaction (HER) with superior stability in acidic electrolyte is of critical importance for large-scale low-cost hydrogen production from water. Herein we report a CoCrFeNiAl high-entropy alloy (HEA) electrocatalyst with self-supported structure synthesized by mechanical alloying and spark plasma sintering (SPS) consolidation. The HEA after HF treatment and in situ electrochemical activation for 4000 cycles of cyclic voltammetry (HF-HEAa2) presents favourable activity with overpotential of 73 mV to reach a current density of 10 mA cm−2 and a Tafel slope of 39.7 mV dec−1. The alloy effect of Al/Cr with Co/Fe/Ni at atomic level high-temperature crystallization as well as consolidation by SPS endow CoCrFeNiAl HEA with high stability in 0.5 M H2SO4 solution. The superior performance of HF-HEAa2 is related with the presence of metal hydroxides/oxides groups on HEA.
In Situ Irradiated X-Ray Photoelectron Spectroscopy on Ag-WS2 Heterostructure For Hydrogen Production Enhancement
Oct 2020
Publication
The hot electron transition of noble materials to catalysis accelerated by localized surface plasmon resonances (LSPRs) was detected by in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) in this article. This paper synthesized an Ag Nanowire (AgNW) @ WS2 core-shell structure with an ultra-thin shell of WS2(3 ∼ 7 nm) and characterized its photocatalytic properties. The AgNW@WS2 core-shell structure exhibited different surface-enhanced Raman spectroscopy (SERS) effects by changing shell thickness indicating that the effect of AgNW could be controlled by WS2 shell. Furthermore the hydrogen production of AgNW@WS2 could reach to 356% of that of pure WS2. The hot electrons arising from the LSPRs effect broke through the Schottky barrier between WS2 and AgNW and transferred to the WS2 shell whose photocatalytic effect was thus enhanced. In addition when the LSPRs effect was intensified by reducing the shell thickness the hot electron transition of noble materials to catalysis was accelerated.
Membrane-Based Electrolysis for Hydrogen Production: A Review
Oct 2021
Publication
Hydrogen is a zero-carbon footprint energy source with high energy density that could be the basis of future energy systems. Membrane-based water electrolysis is one means by which to produce high-purity and sustainable hydrogen. It is important that the scientific community focus on developing electrolytic hydrogen systems which match available energy sources. In this review various types of water splitting technologies and membrane selection for electrolyzers are discussed. We highlight the basic principles recent studies and achievements in membrane-based electrolysis for hydrogen production. Previously the NafionTM membrane was the gold standard for PEM electrolyzers but today cheaper and more effective membranes are favored. In this paper CuCl–HCl electrolysis and its operating parameters are summarized. Additionally a summary is presented of hydrogen production by water splitting including a discussion of the advantages disadvantages and efficiencies of the relevant technologies. Nonetheless the development of cost-effective and efficient hydrogen production technologies requires a significant amount of study especially in terms of optimizing the operation parameters affecting the hydrogen output. Therefore herein we address the challenges prospects and future trends in this field of research and make critical suggestions regarding the implementation of comprehensive membrane-based electrolytic systems.
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.
Methanol Steam Reforming for Hydrogen Generation Via Conventional and Membrane Reactors: A Review
Sep 2013
Publication
Variable renewable energy (VRE) is expected to play a major role in the decarbonization of the electricity sector. However decarbonization via VRE requires a fleet of flexible dispatchable plants with low CO2 emissions to supply clean power during times with limited wind and sunlight. These plants will need to operate at reduced capacity factors with frequent ramps in electricity output posing techno-economic challenges. This study therefore presents an economic assessment of a new near-zero emission power plant designed for this purpose. The gas switching reforming combined cycle (GSR-CC) plant can produce electricity during times of low VRE output and hydrogen during times of high VRE output. This product flexibility allows the plant to operate continuously even when high VRE output makes electricity production uneconomical. Although the CO2 avoidance cost of the GSR-CC plant (€61/ton) was similar to the benchmark post-combustion CO2 capture plant under baseload operation GSR-CC clearly outperformed the benchmark in a more realistic scenario where continued VRE expansion forces power plants into mid-load operation (45% capacity factor). In this scenario GSR-CC promises a 5 %-point higher annualized investment return than the post-combustion benchmark. GSR-CC therefore appears to be a promising concept for a future scenario with high VRE market share and CO2 prices provided that a large market for clean hydrogen is established.
Baseload Electricity and Hydrogen Supply Based on Hybrid PV-wind Power Plants
Sep 2019
Publication
The reliable supplies of electricity and hydrogen required for 100% renewable energy systems have been found to be achievable by utilisation of a mix of different resources and storage technologies. In this paper more demanding parameter conditions than hitherto considered are used in measurement of the reliability of variable renewable energy resources. The defined conditions require that supply of baseload electricity (BLEL) and baseload hydrogen (BLH2) occurs solely using cost-optimised configurations of variable photovoltaic solar power onshore wind energy and balancing technologies. The global scenario modelling is based on hourly weather data in a 0.45° × 0.45° spatial resolution. Simulations are conducted for Onsite and Coastal Scenarios from 2020 to 2050 in 10-year time-steps. The results show that for 7% weighted average cost of capital Onsite BLEL can be generated at less than 119 54 41 and 33 €/MWhel in 2020 2030 2040 and 2050 respectively across the best sites with a maximum 20000 TWh annual cumulative generation potential. Up to 20000 TWhH2HHV Onsite BLH2 can be produced at less than 66 48 40 and 35 €/MWhH2HHV in 2020 2030 2040 and 2050 respectively. A partially flexible electricity demand at 8000 FLh could significantly reduce the costs of electricity supply in the studied scenario. Along with battery storage power-to-hydrogen-to-power is found to have a major role in supply of BLEL beyond 2030 as both a daily and seasonal balancing solution. Batteries are not expected to have a significant role in the provision of electricity to water electrolysers.
Black TiO2 for Solar Hydrogen Conversion
Feb 2017
Publication
Titanium dioxide (TiO2 ) has been widely investigated for photocatalytic H2 evolution and photoelectrochemical (PEC) water splitting since 1972. However its wide bandgap (3.0–3.2 eV) limits the optical absorption of TiO2 for sufficient utilization of solar energy. Blackening TiO2 has been proposed as an effective strategy to enhance its solar absorption and thus the photocatalytic and PEC activities and aroused widespread research interest. In this article we reviewed the recent progress of black TiO2 for photocatalytic H2 evolution and PEC water splitting along with detailed introduction to its unique structural features optical property charge carrier transfer property and related theoretical calculations. As summarized in this review article black TiO2 could be a promising candidate for photoelectrocatalytic hydrogen generation via water splitting and continuous efforts are deserved for improving its solar hydrogen efficiency.
Power-to-gas for Injection into the Gas Grid: What Can We Learn from Real-life Projects, Economic Assessments and Systems Modelling
Sep 2018
Publication
Power-to-gas is a key area of interest for decarbonisation and increasing flexibility in energy systems as it has the potential both to absorb renewable electricity at times of excess supply and to provide backup energy at times of excess demand. By integrating power-to-gas with the natural gas grid it is possible to exploit the inherent linepack flexibility of the grid and shift some electricity variability onto the gas grid. Furthermore provided the gas injected into the gas grid is low-carbon such as hydrogen from renewable power-to-gas then overall greenhouse gas emissions from the gas grid can be reduced.<br/>This work presents the first review of power-to-gas to consider real-life projects economic assessments and systems modelling studies and to compare them based on scope assumptions and outcomes. The review focuses on power-to-gas for injection into the gas grid as this application has specific economic technical and modelling opportunities and challenges.<br/>The review identified significant interest in and potential for power-to-gas in combination with the gas grid however there are still challenges to overcome to find profitable business cases and manage local and system-wide technical issues. Whilst significant modelling of power-to-gas has been undertaken more is needed to fully understand the impacts of power-to-gas and gas grid injection on the operational behaviour of the gas grid taking into account dynamic and spatial effects.
A Production and Delivery Model of Hydrogen from Solar Thermal Energy in the United Arab Emirates
May 2022
Publication
Hydrogen production from surplus solar electricity as energy storage for export purposes can push towards large-scale application of solar energy in the United Arab Emirates and the Middle East region; this region’s properties of high solar irradiance and vast empty lands provide a good fit for solar technologies such as concentrated solar power and photovoltaics. However a thorough comparison between the two solar technologies as well as investigating the infrastructure of the United Arab Emirates for a well-to-ship hydrogen pathway is yet to be fully carried out. Therefore in this study we aim to provide a full model for solar hydrogen production and delivery by evaluating the potential of concentrated solar power and photovoltaics in the UAE then comparing two different pathways for hydrogen delivery based on the location of hydrogen production sites. A Solid Oxide Cell Electrolyzer (SOEC) is used for technical comparison while the shortest routes for hydrogen transport were analyzed using Geographical Information System (GIS). The results show that CSP technology coupled with SOEC is the most favorable pathway for large-scale hydrogen from solar energy production in the UAE for export purposes. Although PV has a slightly higher electricity potential compared to CSP around 42 GWh/km2 to 41.1 GWh/km2 respectively CSP show the highest productions rates of over 6 megatons of hydrogen when the electrolyzer is placed at the same site as the CSP plant while PV generates 5.15 megatons when hydrogen is produced at the same site with PV plants; meanwhile hydrogen from PV and CSP shows similar levels of 4.8 and 4.6 megatons of hydrogen respectively when electrolyzers are placed at port sites. Even considering the constraints in the UAE’s infrastructure and suggesting new shorter electrical transmission lines that could save up to 0.1 megatons of hydrogen in the second pathway production at the same site with CSP is still the most advantageous scenario.
Power-to-Gas: Electrolysis and Methanation Status Review
Jun 2019
Publication
This review gives a worldwide overview on Power-to-Gas projects producing hydrogen or renewable substitute natural gas focusing projects in central Europe. It deepens and completes the content of previous reviews by including hitherto unreviewed projects and by combining project names with details such as plant location. It is based on data from 153 completed recent and planned projects since 1988 which were evaluated with regards to plant allocation installed power development plant size shares and amounts of hydrogen or substitute natural gas producing examinations and product utilization phases. Cost development for electrolysis and carbon dioxide methanation was analyzed and a projection until 2030 is given with an outlook to 2050.<br/>The results show substantial cost reductions for electrolysis as well as for methanation during the recent years and a further price decline to less than 500 euro per kilowatt electric power input for both technologies until 2050 is estimated if cost projection follows the current trend. Most of the projects examined are located in Germany Denmark the United States of America and Canada. Following an exponential global trend to increase installed power today's Power-to-Gas applications are operated at about 39 megawatt. Hydrogen and substitute natural gas were investigated on equal terms concerning the number of projects.
Achievements of European Projects on Membrane Reactor for Hydrogen Production
May 2017
Publication
Membrane reactors for hydrogen production can increase both the hydrogen production efficiency at small scale and the electric efficiency in micro-cogeneration systems when coupled with Polymeric Electrolyte Membrane fuel cells. This paper discusses the achievements of three European projects (FERRET FluidCELL BIONICO) which investigate the application of the membrane reactor concept to hydrogen production and micro-cogeneration systems using both natural gas and biofuels (biogas and bio-ethanol) as feedstock. The membranes used to selectively separate hydrogen from the other reaction products (CH4 CO2 H2O etc.) are of asymmetric type with a thin layer of Pd alloy (<5 μm) and supported on a ceramic porous material to increase their mechanical stability. In FERRET the flexibility of the membrane reactor under diverse natural gas quality is validated. The reactor is integrated in a micro-CHP system and achieves a net electric efficiency of about 42% (8% points higher than the reference case). In FluidCELL the use of bio-ethanol as feedstock for micro-cogeneration Polymeric Electrolyte Membrane based system is investigated in off-grid applications and a net electric efficiency around 40% is obtained (6% higher than the reference case). Finally BIONICO investigates the hydrogen production from biogas. While BIONICO has just started FERRET and FluidCELL are in their third year and the two prototypes are close to be tested confirming the potentiality of membrane reactor technology at small scale.
The Role of the Substrate on the Mechanical and Thermal Stability of Pd Thin Films During Hydrogen (De)sorption
Nov 2020
Publication
In this work we studied the mechanical and thermal stability of ~100 nm Pd thin films magnetron sputter deposited on a bare oxidized Si(100) wafer a sputtered Titanium (Ti) intermediate layer and a spin-coated Polyimide (PI) intermediate layer. The dependence of the film stability on the film morphology and the film-substrate interaction was investigated. It was shown that a columnar morphology with elongated voids at part of the grain boundaries is resistant to embrittlement induced by the hydride formation (α↔β phase transitions). For compact film morphology depending on the rigidity of the intermediate layer and the adherence to the substrate complete transformation (Pd-PI-SiO2/Si) or partly suppression (Pd-Ti-SiO2/Si) of the α to β-phase was observed. In the case of Pd without intermediate layer (Pd-SiO2/Si) buckling delamination occurred. The damage and deformation mechanisms could be understood by the analysis of the stresses and dislocation (defects) behavior near grain boundaries and the film-substrate interface. From diffraction line-broadening combined with microscopy analysis we showed that in Pd thin films stresses relax at critical stress values via different relaxation pathways depending on film-microstructure and film-substrate interaction. On the basis of the in-situ hydriding experiments it was concluded that a Pd film on a flexible PI intermediate layer exhibits free-standing film-like behavior besides being strongly clamped on a stiff SiO2/Si substrate.
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.
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.
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.
MELCOR Analysis of a SPARC Experiment for Spray-PAR Interaction During a Hydrogen Release
Oct 2020
Publication
A series of experiments were performed in the SPARC (spray-aerosol-recombiner-combustion) test facility to simulate a hydrogen mitigation system with the actuation of a PAR (passive auto-catalytic re-combiner) and spray system. In this study the SPARC-SPRAY-PAR (SSP1) experiment is chosen to benchmark the MELCOR (a lumped-parameter code for severe accident analysis) predictions against test data. For this purpose firstly we prepared the base input model of the SPARC test vessel and tested it by a simple verification problem with well-defined boundary conditions. The implementation of a currently used PAR correlation in MELCOR is shown to be appropriate for the simulation of a PAR actuation experiment. In an SSP1 experiment the PAR is reacting with hydrogen and the spray actuation starts as soon as hydrogen injection is complete. The MELCOR simulation well predicts the pressure behavior and the gas flow affected by operating both a PAR and spray system. However the local hydrogen concentration measurement near the inlet nozzle is much higher than the volume average-value by MELCOR since high jet flow from the nozzle is dispersed in the corresponding cell volume. The experimental reproduction of the phenomena we expect or conversely the identification of phenomena we do not understand will continue to support the verification of analytical models using experimental data and to analyze the impact of spray on PAR operations in severe accident conditions.
Electrocatalytic Properties for the Hydrogen Evolution of the Electrodeposited Ni–Mo/WC Composites
May 2021
Publication
The catalytical activity for the hydrogen evolution reaction (HER) of the electrodeposited Ni–Mo/WC composites is examined in 1 M KOH solution. The structure surface morphology and surface composition is investigated using the scanning electron microscopy X-ray diffraction and X-ray photoelectron spectroscopy. The electrocatalytic properties for the HER is evaluated based on the cathodic polarization electrochemical impedance cyclic voltammetry and chronopotentiometry methods. The obtained results prove the superior catalytic activity for the HER of Ni–Mo/WC composites to Ni–Mo alloy. The catalytic activity of Ni–Mo/WC electrodes is determined by the presence of WC nanoparticles and Mo content in the metallic matrix. The best electrocatalytic properties are identified for Ni–Mo/WC composite with the highest Mo content and the most oxidized surface among the studied coatings. The impedance results reveal that the observed improvement in the catalytic activity is the consequence of high real surface area and high intrinsic catalytic activity of the composite.
Experimental and Theoretical Insights to Demonstrate the Hydrogen Evolution Activity of Layered Platinum Dichalcogenides Electrocatalysts
Mar 2021
Publication
Hydrogen is a highly efficient and clean renewable energy source and water splitting through electrocatalytic hydrogen evolution is a most promising approach for hydrogen generation. Layered transition metal dichalcogenides-based nano-structures have recently attracted significant interest as robust and durable catalysts for hydrogen evolution. We systematically investigated the platinum (Pt) based dichalcogenides (PtS2 PtSe2 and PtTe2) as highly energetic and robust hydrogen evolution electrocatalysts. PtTe2 catalyst unveiled the rapid hydrogen evolution process with the low overpotentials of 75 and 92 mV (vs. RHE) at a current density of 10 mA cm−2 and the small Tafel slopes of 64 and 59 mV/dec in acidic and alkaline medium respectively. The fabricated PtTe2 electrocatalyst explored a better catalytic activity than PtS2 and PtSe2. The density functional theory estimations explored that the observed small Gibbs free energy for H-adsorption of PtTe2 was given the prominent role to achieve the superior electrocatalytic and excellent stability activity towards hydrogen evolution due to a smaller bandgap and the metallic nature. We believe that this work will offer a key path to use Pt based dichalcogenides for hydrogen evolution electrocatalysts.
Tautomeric Equilibrium of an Asymmetric β-Diketone in Halogen-Bonded Cocrystals with Perfluorinated Iodobenzenes
Jun 2021
Publication
In order to study the effect of halogen bond on tautomerism in β-diketones in the solid-state we have prepared a series of cocrystals derived from an asymmetric β-diketone benzoyl-4-pyridoylmethane (b4pm) as halogen bond acceptor and perfluorinated iodobenzenes: iodopentaflourobenzene (ipfb) 12- 13- and 14-diiodotetraflorobenzene (12tfib 13tfib and 14tfib) and 135-triiodo-246-trifluorobenzene (135titfb). All five cocrystals are assembled by I···N halogen bonds involving pyridyl nitrogen and iodoperfluorobenzene iodine resulting in 1:1 (four compounds) or 1:2 (one compound) cocrystal stoichiometry. Tautomer of b4pm in which hydrogen atom is adjacent to the pyridyl fragment was found to be more stable in vacuo than tautomer with a benzoyl hydroxyl group. This tautomer is also found to be dominant in the majority of crystal structures somewhat more abundantly in crystal structures of cocrystals in which additional I···O halogen bond with the benzoyl oxygen has been established. Attempts have also been made to prepare an equivalent series of cocrystals using a closely related asymmetric β-diketone benzoyl-3-pyridoylmethane (b3pm); however all attempts were unsuccessful which is attributed to more effective crystal packing of b3pm isomer compared to b4pm which reduced the probability of cocrystal formation.
A Solar Thermal Sorption-enhanced Steam Methane Reforming (SE-SMR) Approach and its Performance Assessment
Feb 2022
Publication
This paper proposes an integration of concentrating solar power (CSP) with a sorption-enhanced steam methane reforming (SE-SMR) process and assesses its overall solar-to-fuel conversion performance. A thermodynamic treatment of the SE-SMR process for H2 production is presented and evaluated in an innovative two reactors system configuration using CSP as a heat input. Four metal carbonate/metal oxide pairs are considered and the equilibrium thermodynamics reveals that CaCO3/CaO pair is the most suitable candidate for this process. Additionally a reactor-scale thermodynamic model is developed to determine the optimum operating conditions for the process. For the carbonation step temperatures between 700 and 900 K and steam-to-methane ratio ≥4 are found to be the most favorable. Furthermore an advanced process model which utilizes operating conditions determined from the reactor-scale model is developed to evaluate the process efficiency. The model predicts that the proposed process can achieve a solar-to-fuel efficiency ~41% for calcination temperature of 1500 K and carbonation temperature of 800 K without considering any solid heat recovery. An additional 2.5% increase in the process efficiency is feasible with the consideration of the solid heat recovery. This study shows the thermodynamic feasibility of integrating the SE-SMR process with CSP technologies.
Production of Ultra-dense Hydrogen H(0): A Novel Nuclear Fuel
Mar 2021
Publication
Condensation of hydrogen Rydberg atoms (highly electronically excited) into the lowest energy state of condensed hydrogen i.e. the ultra-dense hydrogen phase H(0) has gained increased attention not only from the fundamental aspects but also from the applied point of view. The physical properties of ultra-dense hydrogen H(0) were recently reviewed summarizing the results reported in 50 publications during the last ten years. The main application of H(0) so far is as the fuel and working medium in nuclear particle generators and nuclear fusion reactors which are under commercial development. The first fusion process showing sustained operation above break-even was published in 2015 (AIP Advances) and used ultra-dense deuterium D(0) as fuel. The first generator giving a high-intensity muon flux intended for muon-catalyzed fusion reactors was patented in 2017 using H(0) as the working medium. Here we first focus on the different nuclear processes using hydrogen isotopes for energy generation and then on the detailed processes of formation of H(0). The production of H(0) employs heterogeneous catalysts which are active in hydrogen transfer reactions. Iron oxide-based alkali promoted catalysts function well but also platinum group metals and carbon surfaces are active in this process. The clusters of highly excited Rydberg hydrogen atoms H(l) are formed upon interaction with alkali Rydberg matter. The final conversion step from ordinary hydrogen Rydberg matter H(l) to H(0) is spontaneous and does not require a solid surface. It is concluded that the exact choice of catalyst is not very important. It is also concluded that the crucial feature of the catalyst is to provide excited alkali atoms at a sufficiently high surface density and in this way enabling formation and desorption of H(0) clusters. Finally the relation to industrial catalytic processes which use H(0) formation catalysts is described and some important consequences like the muon and neutron radiation from H(0) are discussed.
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%.
Modeling and Statistical Analysis of the Three-side Membrane Reactor for the Optimization of Hydrocarbon Production from CO2 Hydrogenation
Feb 2020
Publication
Direct CO2 hydrogenation to hydrocarbons is a promising method of reducing CO2 emissions along with producing value-added products. However reactor design and performance have remained a challenging issue because of low olefin efficiency and high water production as a by-product. Accordingly a one-dimensional non-isothermal mathematical model is proposed to predict the membrane reactor performance and statistical analysis is used to assess the effects of important variables such as temperatures of reactor (Tr:A) shell (Ts:B) and tube (Tt:C) as well as sweep ratio (θ:D) and pressure ratio (φ:E) and their interactions on the products yields. In addition the optimized operating conditions are also obtained to achieve maximum olefin yields. Results reveal that interacting effects comprising AB (TrTs) AC (TrTt) AE (Trφ) BC (TsTt) CE (Ttφ) CD (Ttθ) and DE (θφ) play important roles on the product yields. It is concluded that higher temperatures at low sweep and pressure ratios can maximize the yields of olefins while simultaneously the yields of paraffins are minimized. In this regard optimized values for Tr Ts Tt θ and φ are determined as 325 °C 306.96 °C 325 °C 1 and 1 respectively.
A Critical Review on the Principles, Applications, and Challenges of Waste-to-hydrogen Technologies
Sep 2020
Publication
Hydrogen sourced from energy recovery processes and conversion of waste materials is a method of providing both a clean fuel and a sustainable waste management alternative to landfill and incineration. The question is whether waste-to–hydrogen can become part of the zero-carbon future energy mix and serve as one of the cleaner hydrogen sources which is economically viable and environmentally friendly. This work critically assessed the potential of waste as a source of hydrogen production via various thermochemical (gasification and pyrolysis) and biochemical (fermentation and photolysis) processes. Research has shown hydrogen production yields of 33.6 mol/kg and hydrogen concentrations of 82% from mixed waste feedstock gasification. Biochemical methods such as fermentation can produce hydrogen up to 418.6 mL/g. Factors including feedstock quality process requirements and technology availability were reviewed to guide technology selection and system design. Current technology status and bottlenecks were discussed to shape future development priorities. These bottlenecks include expensive production and operation processes heterogeneous feedstock low process efficiencies inadequate management and logistics and lack of policy support. Improvements to hydrogen yields and production rates are related to feedstock processing and advanced energy efficiency processes such as torrefaction of feedstock which has shown thermal efficiency of gasification up to 4 MJ/kg. This will affect the economic feasibility and concerns around required improvements to bring the costs down to allow waste to viewed as a serious competitor for hydrogen production. Recommendations were also made for financially competitive waste-to-hydrogen development to be part of a combined solution for future energy needs.
Kinetic Parameters Estimation via Dragonfly Algorithm (DA) and Comparison of Cylindrical and Spherical Reactors Performance for CO2 Hydrogenation to Hydrocarbons
Oct 2020
Publication
Climate change and global warming as well as growing global demand for hydrocarbons in industrial sectors make great incentives to investigate the utilization of CO2 for hydrocarbons production. Therefore finding an in-depth understanding of the CO2 hydrogenation reactors along with simulating reactor responses to different operating conditions are of paramount importance. However the reaction mechanisms for CO2 hydrogenation and their corresponding kinetic parameters have been disputable yet. In this regard considering the previously proposed Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism which considered CO2 hydrogenation as a combination of reverse water gas shift (RWGS) and Fischer-Tropsch (FT) reactions and using a one-dimensional pseudo-homogeneous non-isothermal model kinetic parameters of the rate expressions are estimated via fitting experimental and modelling data through a novel swarm intelligence optimization technique called dragonfly algorithm (DA). The predicted reactants conversion using DA algorithm are closer to the experimental data (with about 4% error) comparing to those obtained by the artificial bee colony (ABC) algorithm and are in significant agreement with available literature data. The proposed model is used to assess the effect of reactor configuration on the performance and temperature fluctuations. Results show that axial flow spherical reactor (AFSR) and radial flow spherical reactor (RFSR) exhibiting the same surface area with that of the cylindrical reactor (CR) i.e. AFSR-2 and RFSR-2-i are the most efficient exhibiting hydrocarbons selectivity of 40.330% and 40.286% at CO2 conversion of 53.763% and 53.891%. In addition it is revealed that the location of the jacket has an essential role in controlling the reactor temperature.
Microwave Absorption of Aluminum/Hydrogen Treated Titanium Dioxide Nanoparticles
Dec 2018
Publication
Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis solar cells optics radar detection communications information processing and transport et al. Traditional mechanisms for such interactions in the microwave frequency mainly rely on dipole rotations and magnetic domain resonance. In this study we present the first report of the microwave absorption of Al/H2 treated TiO2 nanoparticles where the Al/H2 treatment not only induces structural and optical property changes but also largely improves the microwave absorption performance of TiO2 nanoparticles. Moreover the frequency of the microwave absorption can be finely controlled with the treatment temperature and the absorption efficiency can reach optimal values with a careful temperature tuning. A large reflection loss of −58.02 dB has been demonstrated with 3.1 mm TiO2 coating when the treating temperature is 700 °C. The high efficiency of microwave absorption is most likely linked to the disordering-induced property changes in the materials. Along with the increased microwave absorption properties are largely increased visible-light and IR absorptions and enhanced electrical conductivity and reduced skin-depth which is likely related to the interfacial defects within the TiO2 nanoparticles caused by the Al/H2 treatment.
Thermodynamic Analysis of Hydrogen Production via Chemical Looping Steam Methane Reforming Coupled with In Situ CO2 Capture
Dec 2014
Publication
A detailed thermodynamic analysis of the sorption enhanced chemical looping reforming of methane (SE-CL-SMR) using CaO and NiO as CO2 sorbent and oxygen transfer material (OTM) respectively was conducted. Conventional reforming (SMR) and sorption enhanced reforming (SE-SMR) were also investigated for comparison reasons. The results of the thermodynamic analysis show that there are significant advantages of both sorption enhanced processes compared to conventional reforming. The presence of CaO leads to higher methane conversion and hydrogen purity at low temperatures. Addition of the OTM in the SECL-SMR process concept minimizes the thermal requirements and results in superior performance compared to SE-SMR and SMR in a two-reactor concept with use of pure oxygen as oxidant/sweep gas.
Energy Optimization of a Sulfur-Iodine Thermochemical Nuclear Hydrogen Production Cycle
Dec 2021
Publication
The use of nuclear reactors is a large studied possible solution for thermochemical water splitting cycles. Nevertheless there are several problems that have to be solved. One of them is to increase the efficiency of the cycles. Hence in this paper a thermal energy optimization of a SulfureIodine nuclear hydrogen production cycle was performed by means a heuristic method with the aim of minimizing the energy targets of the heat exchanger network at different minimum temperature differences. With this method four different heat exchanger networks are proposed. A reduction of the energy requirements for cooling ranges between 58.9-59.8% and 52.6-53.3% heating compared to the reference design with no heat exchanger network. With this reduction the thermal efficiency of the cycle increased in about 10% in average compared to the reference efficiency. This improves the use of thermal energy of the cycle.
Characterization of the Inducible and Slow-Releasing Hydrogen Sulfide and Persulfide Donor P*: Insights into Hydrogen Sulfide Signaling
Jun 2021
Publication
Hydrogen sulfide (H2S) is an important mediator of inflammatory processes. However controversial findings also exist and its underlying molecular mechanisms are largely unknown. Recently the byproducts of H2S per-/polysulfides emerged as biological mediators themselves highlighting the complex chemistry of H2S. In this study we characterized the biological effects of P* a slow-releasing H2S and persulfide donor. To differentiate between H2S and polysulfide-derived effects we decomposed P* into polysulfides. P* was further compared to the commonly used fast-releasing H2S donor sodium hydrogen sulfide (NaHS). The effects on oxidative stress and interleukin-6 (IL-6) expression were assessed in ATDC5 cells using superoxide measurement qPCR ELISA and Western blotting. The findings on IL-6 expression were corroborated in primary chondrocytes from osteoarthritis patients. In ATDC5 cells P* not only induced the expression of the antioxidant enzyme heme oxygenase-1 via per-/polysulfides but also induced activation of Akt and p38 MAPK. NaHS and P* significantly impaired menadione-induced superoxide production. P* reduced IL-6 levels in both ATDC5 cells and primary chondrocytes dependent on H2Srelease. Taken together P* provides a valuable research tool for the investigation of H2S and per-/polysulfide signalling. These data demonstrate the importance of not only H2S but also per-/polysulfides as bioactive signaling molecules with potent anti-inflammatory and in particular antioxidant properties.
From Post-Combustion Carbon Capture to Sorption-Enhanced Hydrogen Production: A State-of-the-Art Review of Carbonate Looping Process Feasibility
Oct 2018
Publication
Carbon capture and storage is expected to play a pivotal role in achieving the emission reduction targets established by the Paris Agreement. However the most mature technologies have been shown to reduce the net efficiency of fossil fuel-fired power plants by at least 7% points increasing the electricity cost. Carbonate looping is a technology that may reduce these efficiency and economic penalties. Its maturity has increased significantly over the past twenty years mostly due to development of novel process configurations and sorbents for improved process performance. This review provides a comprehensive overview of the calcium looping concepts and statistically evaluates their techno-economic feasibility. It has been shown that the most commonly reported figures for the efficiency penalty associated with calcium looping retrofits were between 6 and 8% points. Furthermore the calcium-looping-based coal-fired power plants and sorption-enhanced hydrogen production systems integrated with combined cycles and/or fuel cells have been shown to achieve net efficiencies as high as 40% and 50–60% respectively. Importantly the performance of both retrofit and greenfield scenarios can be further improved by increasing the degree of heat integration as well as using advanced power cycles and enhanced sorbents. The assessment of the economic feasibility of calcium looping concepts has indicated that the cost of carbon dioxide avoided will be between 10 and 30 € per tonne of carbon dioxide and 10–50 € per tonne of carbon dioxide in the retrofit and greenfield scenarios respectively. However limited economic data have been presented in the current literature for the thermodynamic performance of calcium looping concepts.
Effect of Copper Cobalt Oxide Composition on Oxygen Evolution Electrocatalysts for Anion Exchange Membrane Water Electrolysis
Nov 2020
Publication
Copper cobalt oxide nanoparticles (CCO NPs) were synthesized as an oxygen evolution electrocatalyst via a simple co-precipitation method with the composition being controlled by altering the precursor ratio to 1:1 1:2 and 1:3 (Cu:Co) to investigate the effects of composition changes. The effect of the ratio of Cu2+/Co3+ and the degree of oxidation during the co-precipitation and annealing steps on the crystal structure morphology and electrocatalytic properties of the produced CCO NPs were studied. The CCO1:2 electrode exhibited an outstanding performance and high stability owing to the suitable electrochemical kinetics which was provided by the presence of sufficient Co3+ as active sites for oxygen evolution and the uniform sizes of the NPs in the half cell. Furthermore single cell tests were performed to confirm the possibility of using the synthesized electrocatalyst in a practical water splitting system. The CCO1:2 electrocatalyst was used as an anode to develop an anion exchange membrane water electrolyzer (AEMWE) cell. The full cell showed stable hydrogen production for 100 h with an energetic efficiency of >71%. In addition it was possible tomass produce the uniform highly active electrocatalyst for such applications through the co-precipitation method.
Storable Energy Production from Wind over Water
Apr 2020
Publication
The current status of a project is described which aims to demonstrate the technical and economic feasibility of converting the vast wind energy available over the globe’s oceans and lakes into storable energy. To this end autonomous high-performance sailing ships are equipped with hydrokinetic turbines whose output is stored either in electric batteries or is fed into electrolysers to produce hydrogen which then is compressed and stored in tanks. In the present paper the previous analytical studies which showed the potential of this “energy ship concept” are summarized and progress on its hardware demonstration is reported involving the conversion of a model sailboat to autonomous operation. The paper concludes with a discussion of the potential of this concept to achieve the IPCC-mandated requirement of reducing the global CO2 emissions by about 45% by 2030 reaching net zero by 2050.
Electrosynthesized Ni-P Nanospheres with High Activity and Selectivity Towards Photoelectrochemical Plastics Reforming
May 2021
Publication
Photoelectrochemical reforming of plastic waste offers an environmentally-benign and sustainable route for hydrogen generation. Nonetheless little attention was paid to develop electrocatalysts that can efficiently and selectively catalyze oxidative transformation of valueless plastic wastes into valued chemicals. Herein we report on facile electrosynthesis of nickel-phosphorus nanospheres (nanoNi-P) and their versatility in catalyzing hydrogen generation water oxidation and reforming of polyethylene terephthalate (PET). Notably composite of nanoNi-P with carbon nanotubes (CNT/nanoNi-P) requires −180 mV overpotential to drive hydrogen generation at -100 mA cm−2. Besides CV-activated nanoNi-P (nanoNi-P(CV)) was shown to be capable of reforming PET into formate with high selectivity (Faradic efficiency= ∼100 %). Efficient and selective generation of hydrogen and formate from PET reforming is realized utilizing an Earth-abundant photoelectrochemical platform based on nanoNi-P(CV)-modified TiO2 nanorods photoanode and CNT/nanoNi-P cathode. This work paves a path for developing artificial leaf for simultaneous environmental mitigation and photosynthesis of renewable fuels and valued chemicals.
Raw Biomass Electroreforming Coupled to Green Hydrogen Generation
Mar 2021
Publication
Despite the tremendous progress of coupling organic electrooxidation with hydrogen generation in a hybrid electrolysis electroreforming of raw biomass coupled to green hydrogen generation has not been reported yet due to the rigid polymeric structures of raw biomass. Herein we electrooxidize the most abundant natural amino biopolymer chitin to acetate with over 90% yield in hybrid electrolysis. The overall energy consumption of electrolysis can be reduced by 15% due to the thermodynamically and kinetically more favorable chitin oxidation over water oxidation. In obvious contrast to small organics as the anodic reactant the abundance of chitin endows the new oxidation reaction excellent scalability. A solar-driven electroreforming of chitin and chitin-containing shrimp shell waste is coupled to safe green hydrogen production thanks to the liquid anodic product and suppression of oxygen evolution. Our work thus demonstrates a scalable and safe process for resource upcycling and green hydrogen production for a sustainable energy future.
Volumetric Analysis Technique for Analyzing the Transport Properties of Hydrogen Gas in Cylindrical-shaped Rubbery Polymers
Mar 2021
Publication
We report volumetric analysis techniques to analyze the transport properties of hydrogen dissolved in cylindrical-shaped polymers. The techniques utilize the volume measurement of the released hydrogen from rubber by gas collection in a graduated cylinder after charging sample with high-pressure hydrogen and subsequent decompression. We further improve the graduated cylinder with some modifications such as reading the electrical capacitance of the water level using electrodes and changing the sample loading position. From the measurement results the uptake (C∞) diffusion coefficient (D) and solubility (S) of hydrogen are quantified with an upgraded diffusion analysis program. These methods are applied to three cylindrical rubbers. Dual adsorption behaviors with increasing pressure are observed for all the samples. C∞ follows Henry’s law up to ~15 MPa whereas Langmuir model applies up to 90 MPa. D shows Knudsen and bulk diffusion behavior below and above pressure respectively. A COMSOL simulation is compared with experimental observations.
Synthesizing the High Surface Area g-C3N4 for Greatly Enhanced Hydrogen Production
Jul 2021
Publication
Adjusting the structure of g-C3N4 to significantly enhance its photocatalytic activity has attracted considerable attention. Herein a novel sponge-like g-C3N4 with a porous structure is prepared from the annealing of protonated melamine under N2/H2 atmosphere (PH-CN). Compared to bulk g-C3N4 via calcination of melamine under ambient atmosphere (B-CN) PH-CN displays thinner nanosheets and a higher surface area (150.1 m2/g) which is a benefit for shortening the diffusion distance of photoinduced carriers providing more active sites and finally favoring the enhancement of the photocatalytic activity. Moreover it can be clearly observed from the UV-vis spectrum that PH-CN displays better performance for harvesting light compared to B-CN. Additionally the PH-CN is prepared with a larger band gap of 2.88 eV with the Fermi level and conduction band potential increased and valence band potential decreased which could promote the water redox reaction. The application experiment results show that the hydrogen evolution rate on PH-CN was nearly 10 times higher than that of B-CN which was roughly 4104 μmol h−1 g−1. The method shown in this work provides an effective approach to adjust the structure of g-C3N4with considerable photocatalytic hydrogen evolution activity.
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