Production & Supply Chain

An integrated system for H2 production from microalgae and its storage is proposed employing enhanced process integration technology (EPI). EPI consists of two core technologies i.e. exergy recovery and process integration. The proposed system includes a supercritical water gasification H2 separation hydrogenation and combined cycle. Microalga Chlorella vulgaris is used as a material for evaluation. The produced syngas is separated to produce highly pure H2. Furthermore to store the produced H2 liquid organic H2 carrier of toluene-and-methylcyclohexane cycle is adopted. The remaining gas is used as fuel for combustion in combined cycle to generate electricity. The effects of fluidization velocity and gasification pressure to energy efficiency are evaluated. From process modelling and calculation it is shown that high total energy efficiency about 60% can be achieved. In addition about 40% of electricity generation efficiency can be realized.

There is a need to derive hydrogen from renewable sources and the innovative stewardship of two natural resources namely the Sun and forest could provide a new pathway. This paper provides the first comparative analysis of solar-driven hydrogen production from environmental angles. A novel hydrogen production process proposed in this paper named Solar-Driven Advanced Biomass Indirect-Gasification (SABI-Hydrogen) shows promise toward achieving continuous operation and scalability the two key challenges to meet future energy needs. The calculated Global Warming Potential for 1 kg of solar-driven hydrogen production is 1.04 kg CO2-eq/kg H2 less than half of the current biomass gasification process which emits 2.67 kg CO2-eq/kg H2. Further SABI-Hydrogen demonstrates the least-carbon intensive pathway among all current hydrogen production methods. Thus solar-driven hydrogen production from biomass could lead to a sustainable supply essential for a low-carbon energy transition.

The bioanode is important for a microbial electrolysis cell (MEC) and its robustness to maintain its catalytic activity affects the performance of the whole system. Bioanodes enriched at a potential of +0.2 V (vs. standard hydrogen electrode) were able to sustain their oxidation activity when the anode potential was varied from 0.3 up to +1.0 V. Chronoamperometric test revealed that the bioanode produced peak current density of 0.36 A/m2 and 0.37 A/m2 at applied potential 0 and +0.6 V respectively. Meanwhile hydrogen production at the biocathode was proportional to the applied potential in the range from 0.5 to 1.0 V. The highest production rate was 7.4 L H2/(m2 cathode area)/day at 1.0 V cathode potential. A limited current output at the bioanode could halt the biocathode capability to generate hydrogen. Therefore maximum applied potential that can be applied to the biocathode was calculated as 0.84 V without overloading the bioanode

Reversible solid oxide cells (r-SOCs) can be operated in either solid oxide fuel cell or solid oxide electrolysis cell mode. They are expected to become important in the support of renewable energy due to their high efficiency for both power generation and hydrogen generation. The exchange current density is one of the most important parameters in the quantification of electrode performance in solid oxide cells. In this study four different fuel electrodes and two different air electrodes are fabricated using different materials and the microstructures are compared. The temperature fuel humidification and oxygen concentration at the air electrode are varied to obtain the apparent exchange current density for the different electrode materials. In contrast to ruthenium-and-gadolinia-doped ceria (Rh-GDC) as well as nickel-and-gadolinia-doped ceria (Ni-GDC) electrodes significant differences in the apparent exchange current density were observed between electrolysis and fuel cell modes for the nickel-scandia-stabilized zirconia (Ni-ScSZ) cermet. Variation of gas concentration revealed that surface adsorption sites were almost completely vacant for all these electrodes. The apparent exchange current densities obtained in this study are useful as a parameter for simulation of the internal properties of r-SOCs.

Photocatalysis for “green” hydrogen production is a technology of increasing importance that has been studied using both TiO2–based and heterojunction composite-based semiconductors. Different irradiation sources and reactor units can be considered for the enhancement of photocatalysis. Current approaches also consider the use of electron/hole scavengers organic species such as ethanol that are “available” in agricultural waste in communities around the world. Alternatively organic pollutants present in wastewaters can be used as organic scavengers reducing health and environmental concerns for plants animals and humans. Thus photocatalysis may help reduce the carbon footprint of energy production by generating H2 a friendly energy carrier and by minimizing water contamination. This review discusses the most up-to-date and important information on photocatalysis for hydrogen production providing a critical evaluation of: (1) The synthesis and characterization of semiconductor materials; (2) The design of photocatalytic reactors; (3) The reaction engineering of photocatalysis; (4) Photocatalysis energy efficiencies; and (5) The future opportunities for photocatalysis using artificial intelligence. Overall this review describes the state-of-the-art of TiO2–based and heterojunction composite-based semiconductors that produce H2 from aqueous systems demonstrating the viability of photocatalysis for “green” hydrogen production.

The search for alternatives to fossil energy traditional sources led to the development of a set of energy conversion processes which include biomass thermochemical conversion technologies such as torrefaction pyrolysis hydrothermal liquefaction or gasification. These conversion technologies have shown significant evolutions and there are already several examples available of application on an industrial scale. Biomass gasification processes have also presented significant developments mainly when associated with the production of syngas with potential for energy recovery or to produce synthetic fuels but mainly due to its potential to be used as a sustainable hydrogen production technology. In the present work a bibliographic review of the current state-of-the-art of the biomass gasification is carried out focusing in the gasification technologies syngas cleaning processes simulation methodologies on process parameters. Finally future developments and possibilities are also analyzed and discussed with the introduction of a new approach to hydrogen production based on the use of an adapted combustion process with air deficit.

Application of Solid Oxide Fuel Cells (SOFC) in gasification-based power plants would represent a turning point in the power generation sector allowing to considerably increase the electric efficiency of coal-fired power stations while reducing CO2 and other pollutant emissions. The aim of this paper is the thermodynamic assessment of a SOFC-based IGFC plant with methanation reactor hydrogen post-firing and CO2 capture by physical absorption. The configuration proposed allows to obtain a very high net efficiency (51.6%) overcoming the main limits of configurations assessed in previous works.

Cell immobilization and co-culture techniques have gained attention due to its potential to obtain high volumetric hydrogen productivities (Q_H2). Chitosan retained biomass in the fermentation of co-cultures of Caldicellulosiruptor saccharolyticus and C. owensensis efficiently up to a maximum dilution rate (D) of 0.9 h⁻¹. Without chitosan wash out of the co-culture occurred earlier accompanied with approximately 50% drop in Q_H2 (D > 0.4 h⁻¹). However butyl rubber did not show as much potential as carrier material; it did neither improve Q_H2 nor biomass retention in continuous culture. The population dynamics revealed that C. owensensis was the dominant species (95%) in the presence of chitosan whereas C. saccharolyticus was the predominant (99%) during cultivation without chitosan. In contrast the co-culture with rubber as carrier maintained the relative population ratios around 1:1. This study highlighted chitosan as an effective potential carrier for immobilization thereby paving the way for cost – effective hydrogen production.

<br/>Cyclic Voltammetry Measurements performed on a Cobaloxime Catalyst designed for photochemical hydrogen production.

In this paper we present a detailed design study of a novel apparatus for safely generating hydrogen (H2) on demand according to a novel method using a controlled chemical reaction between water (H2O) and sodium (Na) metal that yields hydrogen gas of sufficient purity for direct use in fuel cells without risk of contaminating sensitive catalysts. The apparatus consists of a first pressure vessel filled with liquid H2O with an overpressure of nitrogen (N2) gas above the H2O reactant and a second pressure vessel that stores solid Na reactant. Hydrogen gas is generated above the solid Na when H2O reactant is introduced using a regulator that senses when the downstream pressure of H2 gas above the solid Na reactant has dropped below a threshold value. The sodium hydroxide (NaOH) byproduct of the hydrogen producing reaction is collected within the apparatus for later reprocessing by electrolysis to recover the Na reactant.

As the offshore energy landscape transitions to renewable energy useful decommissioned or abandoned oil and gas infrastructure can be repurposed in the context of the circular economy. Oil and gas platforms for example offer opportunity for hydrogen (H2) production by desalination and electrolysis of sea water using offshore wind power. However as H2 storage and transport may prove challenging this study proposes to react this H2 with the carbon dioxide (CO2) stored in depleted reservoirs. Thus producing a more transportable energy carriers like methane or methanol in the reservoir. This paper presents a novel thermodynamic analysis of the Goldeneye reservoir in the North Sea in Aspen Plus. For Goldeneye which can store 30 Mt of CO2 at full capacity if connected to a 4.45 GW wind farm it has the potential to produce 2.10 Mt of methane annually and abate 4.51 Mt of CO2 from wind energy in the grid.

We investigated a simple and safe method for producing hydrogen using Si powder which is discarded in the semiconductor industry. Using the reaction of generating hydrogen from Si powder and an aqueous NaOH solution a simple hydrogen generator that imitated Kipp’s apparatus was produced. Then by combining this apparatus with a polymer electrolyte fuel cell an automatic hydrogen generation system based on the amount of electric power required was proposed. Furthermore it was found that hydrogen can also be generated using non-poisonous and deleterious substances Ca(OH)2 and Na2CO3 instead of the deleterious substance NaOH and adding water to the mixture with Si powder. The by-products Na2SiO3 and CaCO3 can be used as raw materials for glass. The simple hydrogen generator produced in this study can be used as a fuel supply source for small-scale power generation systems as an auxiliary power source.

An energy production from the combination of dehydrogenation and combined cycle power generation is proposed. The delivered system is established from three main modules: dehydrogenation combustion and combined cycle. The heat in the system is circulated thoroughly to enhance the energy efficiency due to optimum energy recovery. The Pt/Al2O3 catalyst is applied in the dehydrogenation module due to superior activity to accelerate the dehydrogenation of MCH. The toluene emitted from the MCH is recirculated to the hydrogenation plant while the hydrogen is further utilized as the fuel in the combustion. Although the high-temperature condition is necessary to perform high yield dehydrogenation the proposed system is capable of carrying out self-heating mechanism with no external heat. With the optimum configuration the delivered system can produce 100.0 MW of electricity from 100 t/h of MCH with 50.19% of energy efficiency.

This paper proposes a parameter adjustable dynamic mass and energy balance simulation model for an industrial alkaline water electrolyzer plant that enables cost and energy efficiency optimization by means of system dimensioning and control. Thus the simulation model is based on mathematical models and white box coding and it uses a practicable number of fixed parameters. Zero-dimensional energy and mass balances of each unit operation of a 3 MW and 16 bar plant process were solved in MATLAB functions connected via a Simulink environment. Verification of the model was accomplished using an analogous industrial plant of the same power and pressure range having the same operational systems design. The electrochemical mass flow and thermal behavior of the simulation and the industrial plant were compared to ascertain the accuracy of the model and to enable modification and detailed representation of real case scenarios so that the model is suitable for use in future plant optimization studies. The thermal model dynamically predicted the real case with 98.7 % accuracy. Shunt currents were the main contributor to relative low Faraday efficiency of 86 % at nominal load and steady-state operation and heat loss to ambient from stack was only 2.6 % of the total power loss.

Bioenergy with carbon capture and storage (BECCS) removes carbon dioxide (CO2) from the atmosphere i.e. negative CO2 emissions. It will likely have an important role in the transition to a net-zero economy by offsetting hard-to-abate greenhouse gas emissions. However there are concerns about the sustainability of large scale BECCS deployment using bioenergy from predominantly primary biomass sources (i.e. dedicated energy crops). Secondary sources of biomass (e.g. waste biomass municipal solid wastes forest/agricultural residues) are potentially an economical and sustainable alternative resource. Furthermore supplementing primary biomass demand with secondary sources could enable the supply of biomass from solely indigenous sources (i.e. from the UK) which could provide economic advantages in a growing global bio-economy.<br/><br/>There is also a growing interest in biomass-derived hydrogen production with CCS (BHCCS) which generates hydrogen and removes CO2 from the atmosphere. Hydrogen could help decarbonise fuel-dependent sectors such as heat industry or transportation. The aim of this study was to determine whether BHCCS could possibly deliver net negative CO2 emissions making comparisons against the other BECCS technologies.

The high variability and intermittency of wind and solar farms raise questions of how to operate electrolyzers reliably economically and sustainably using pre-dominantly or exclusively variable renewables. To address these questions we develop a comprehensive cost framework that extends to include factors such as performance degradation efficiency financing rates and indirect costs to assess the economics of 10 MW scale alkaline and proton-exchange membrane electrolyzers to generate hydrogen. Our scenario analysis explores a range of operational configurations considering (i) current and projected wholesale electricity market data from the Australian National Electricity Market (ii) existing so-lar/wind farm generation curves and (iii) electrolyzer capital costs/performance to determine costs of H2production in the near (2020–2040) and long term(2030–2050). Furthermore we analyze dedicated off-grid integrated electro-lyzer plants as an alternate operating scenario suggesting oversizing renewable nameplate capacity with respect to the electrolyzer to enhance operational capacity factors and achieving more economical electrolyzer operation.

The Isle of Grain (IoG) presents a technically feasible commercially viable strategic location to build and operate a hydrogen production facility which would be a key enabler to the UK meeting the Net Zero 2050 target.

As highlighted in the ‘Net Zero – The UK’s contribution to stopping global warming’ report published by The Committee on Climate Change in May 2019 hydrogen is set to have a major part to play in reducing UK carbon dioxide emissions. Carbon Capture and Storage (CCS) is also seen as essential to support those supplies.

The report further recognises that this will involve increased investments and that CCS and hydrogen will require both capital funding and revenue support.

For hydrogen to have a part to play in the decarbonisation of London and the south east of England a large-scale hydrogen production facility will be required which will provide a multi vector solution through the decarbonisation of the gas grid.

This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.

Power- and biomass-to-liquid fuel processes (PBtL) can utilize renewable energy and residual forestry waste to produce liquid synthetic fuels which have the potential to mitigate the climate impacts of the current transportation infrastructure including the long-haul aviation sector. In a previous study we demonstrated that implementing a solid oxide electrolysis cell (SOEC) in the PBtL process can significantly increase the energy efficiency of fuel production by supplying the produced hydrogen to a reverse water gas shift (RWGS) reactor to generate syngas which is then fed downstream to a Fischer–Tropsch (FT) reactor. The tail gas emitted from the FT reactor consists primarily of a mixture of hydrogen carbon monoxide and methane and is often recycled to the entrained flow gasifier located at the beginning of the process. In this analysis we investigate the efficiency gains of the PBtL process as a result of redirecting the tail gas of the FT reactor to the anode of an SOEC to serve as fuel. Supplying fuel to an SOEC can lower the electrical work input required to facilitate steam electrolysis when reacting electrochemically with oxide ions in the anode which in turn can reduce oxygen partial pressures and thus alleviate material degradation. Accordingly we develop a thermodynamic framework to reveal the performance limits of fuel-assisted SOECs (FASOECs) and provide strategies to minimize oxygen partial pressures in the SOEC anode. Additionally we elucidate how much fuel is required to match the heating demands of a cell when steam is supplied to the cathode over a broad range of inlet temperatures and demonstrate the influence of a set of reaction pathways of the supplied fuel on the operating potential of an FASOEC and the corresponding efficiency gain of the PBtL process. Based on preliminary calculations we estimate that implementing an FASOEC in the PBtL process can increase the energy efficiency of fuel production to more than 90% depending on the amount of FT tail gas available to the system.

Solid oxide electrolysis cells (SOECs) are an efficient technology for the production of green hydrogen that has great potential to contribute to the energy transition and decarbonization of industry. To date however time- and resource-intensive experimental campaigns slow down the development and market penetration of the technology. In order to speed-up the evaluation of SOEC performance and durability accelerated testing protocols are required. This work provides the results of experimental studies on the performance of a SOEC stack operated under accelerated degradation conditions. In order to initiate and accelerate degradation experiments were performed with high steam partial pressures at the gas inlet higher voltages and lower temperatures and high steam conversion rates. Thereby different types and degrees of impact on performance were observed which were analyzed in detail and linked to the underlying processes and degradation mechanisms. In this context significantly higher degradation rates were found compared to operation under moderate operating conditions with the different operating strategies varying in their degradation acceleration potential. The results also suggest that a few hundred hours of operation may be sufficient to predict long-term performance with the proposed operating strategies providing a solid basis for accelerated assessment of SOEC performance evolution and lifetime.

A palladium (Pd) doped mesoporous titanium dioxide (TiO2) photocatalyst was used to produce hydrogen (H2) via water splitting under both near‐UV and visible light. Experiments were carried out in the Photo‐CREC Water‐II Reactor (PCW‐II) using a 0.25 wt% Pd‐TiO2 photocatalyst initial pH = 4 and 2.0 v/v% ethanol as an organic scavenger. After 6 h of near‐UV irradiation this photocatalyst yielded 113 cm3 STP of hydrogen (H2). Furthermore after 1 h of near‐UV photoreduc‐ tion followed by 5 h of visible light the 0.25 wt% Pd‐TiO2 photocatalyst yielded 5.25 cm3 STP of H2. The same photocatalyst photoreduced for 24 h under near‐UV and subsequently exposed to 5 h of visible light yielded 29 cm3 STP of H2. It was observed that the promoted redox reactions led to the production of hydrogen and by‐products such as methane ethane ethylene acetaldehyde carbon monoxide carbon dioxide and hydrogen peroxide. These redox reactions could be modeled using an “in series‐parallel” reaction network and Langmuir Hinshelwood based kinetics. The proposed rate equations were validated using statistical analysis for the experimental data and calculated kinetic parameters. Furthermore Quantum yields (QYୌ%) based on the H produced were also established at promising levels: (a) 34.8% under near‐UV light and 1.00 g L−1 photocatalyst concen‐ tration; (b) 8.8% under visible light and 0.15 g L−1. photocatalyst concentration following 24 h of near‐UV.

Development of efficient and affordable photocatalysts is of great significance for energy production and environmental sustainability. Transition metal chalcogenides (TMCs) with particle sizes in the 1–100 nm have been used for various applications such as photocatalysis photovoltaic and energy storage due to their quantum confinement effect optoelectronic behavior and their stability. In particular TMCs and their heterostructures have great potential as an emerging inexpensive and sustainable alternative to metal-based catalysts for hydrogen evolution. Herein the methods used for the fabrication of TMCs characterization techniques employed and the different methods of solar hydrogen production by using different TMCs as photocatalyst are reviewed. This review provides a summary of TMC photocatalysts for hydrogen production.

Direct internal reforming enables optimal heat integration and reduced complexity in solid oxide fuel cell (SOFC) systems but thermal stresses induced by the increased temperature gradients may inflict damage to the stack. Therefore the development of adequate control strategies requires models that can accurately predict the temperature profiles in the stack. A 1D dynamic modelling platform is developed in this study and used to simulate SOFCs in both single cell and stack configurations. The single cell model is used to validate power law and Hougen-Watson reforming kinetics derived from experiments in previous work. The stack model based on the same type of cells accounts for heat transfer in the inactive area and to the environment and is validated with data reported by the manufacturer. The reforming kinetics are then implemented in the stack model to simulate operation with direct internal reforming. Although there are differences between the temperature profiles predicted by the two kinetic models both are more realistic than assuming chemical equilibrium. The results highlight the need to identify rate limiting steps for the reforming and hydrogen oxidation reactions on anodes of functional SOFC assemblies. The modelling approach can be used to study off-design conditions transient operation and system integration as well as to develop adequate energy management and control strategies.

Iron oxide has been widely used as an oxygen carrier material (OCM) for hydrogen production by chemical looping due to its favourable thermodynamic properties. In spite of this iron oxide loses much of its activity after redox cycling mainly due to sintering and agglomeration. Perovskites such as La_0.7Sr_0.3FeO_3-d (LSF731) have been suggested as potential candidate OCMs for hydrogen production due to their excellent oxygen transport properties and stability under cycling. However hydrogen production per cycle for a similar carrier weight is lower than with iron oxide. This work proposes the use of composite OCMs made of iron oxide clusters embedded in an LSF731 matrix. The perovskite matrix facilitates oxygen transport to the iron oxide clusters while preventing agglomeration. Two preparation methods mechanical mixing and a modified Pechini method were used to obtain composite materials with different iron oxide weight fractions 11 and 30 wt.%. The reactivity of these OCMs was studied in a thermogravimetric analyser. Hydrogen production and carrier stability were investigated in a microreactor over 25 redox cycles while periodically feeding carbon monoxide and water in order to produce carbon dioxide and hydrogen in separate streams. Hydrogen production was stable over 25 cycles for LSF731 and the composite OCM with 30 wt.% iron oxide produced by the modified Pechini method but iron oxide particles alone underwent a decrease in the hydrogen production with cycling. The hydrogen production during the 25th cycle was eight times higher for the composite material than for iron oxide alone and four times higher than for LSF731. The hydrogen production was therefore also higher than that expected from a simple combination of the iron oxide and LSF731 alone indicating a synergetic effect whereby the LSF731 may have a higher effective oxygen capacity when in the form of the composite material.

This study outlines an approach to identifying the difficulties associated with the bench-marking of alkaline single cells under real electrolyzer conditions. A challenging task in the testing and comparison of different catalysts is obtaining reliable and meaningful benchmarks for these conditions. Negative effects on reproducibility were observed due to the reduction in conditioning time. On the anode side a stable passivation layer of NiO can be formed by annealing of the Ni foams which is even stable during long-term operation. Electrical contact resistance and impedance measurements showed that most of the contact resistance derived from the annealed Ni foam. Additionally analysis of various overvoltages indicated that most of the total overvoltage comes from the anode and cathode activation overpotential. Different morphologies of the substrate material exhibited an influence on the performance of the alkaline single cell based on an increase in the ohmic resistance.