Production & Supply Chain
Economic Viability and Environmental Efficiency Analysis of Hydrogen Production Processes for the Decarbonization of Energy Systems
Aug 2019
Publication
The widespread penetration of hydrogen in mainstream energy systems requires hydrogen production processes to be economically competent and environmentally efficient. Hydrogen if produced efficiently can play a pivotal role in decarbonizing the global energy systems. Therefore this study develops a framework which evaluates hydrogen production processes and quantifies deficiencies for improvement. The framework integrates slack-based data envelopment analysis (DEA) with fuzzy analytical hierarchy process (FAHP) and fuzzy technique for order of preference by similarity to ideal solution (FTOPSIS). The proposed framework is applied to prioritize the most efficient and sustainable hydrogen production in Pakistan. Eleven hydrogen production alternatives were analyzed under five criteria including capital cost feedstock cost O&M cost hydrogen production and CO2 emission. FAHP obtained the initial weights of criteria while FTOPSIS determined the ultimate weights of criteria for each alternative. Finally slack-based DEA computed the efficiency of alternatives. Among the 11 three alternatives (wind electrolysis PV electrolysis and biomass gasification) were found to be fully efficient and therefore can be considered as sustainable options for hydrogen production in Pakistan. The rest of the eight alternatives achieved poor efficiency scores and thus are not recommended.
High-Purity and Clean Syngas and Hydrogen Production From Two-Step CH4 Reforming and H2O Splitting Through Isothermal Ceria Redox Cycle Using Concentrated Sunlight
Jul 2020
Publication
The thermochemical conversion of methane (CH4) and water (H2O) to syngas and hydrogen via chemical looping using concentrated sunlight as a sustainable source of process heat attracts considerable attention. It is likewise a means of storing intermittent solar energy into chemical fuels. In this study solar chemical looping reforming of CH4 and H2O splitting over non-stoichiometric ceria (CeO2/CeO2−δ) redox cycle were experimentally investigated in a volumetric solar reactor prototype. The cycle consists of (i) the endothermic partial oxidation of CH4 and the simultaneous reduction of ceria and (ii) the subsequent exothermic splitting of H2O and the simultaneous oxidation of the reduced ceria under isothermal operation at ~1000°C enabling the elimination of sensible heat losses as compared to non-isothermal thermochemical cycles. Ceria-based reticulated porous ceramics with different sintering temperatures (1000 and 1400°C) were employed as oxygen carriers and tested with different methane flow rates (0.1–0.4 NL/min) and methane concentrations (50 and 100%). The impacts of operating conditions on the foam-averaged oxygen non-stoichiometry (reduction extent δ) syngas yield methane conversion solar-to-fuel energy conversion efficiency as well as the effects of transient solar conditions were demonstrated and emphasized. As a result clean syngas was successfully produced with H2/CO ratios approaching 2 during the first reduction step while high-purity H2 was subsequently generated during the oxidation step. Increasing methane flow rate and CH4 concentration promoted syngas yields up to 8.51 mmol/gCeO2 and δ up to 0.38 at the expense of enhanced methane cracking reaction and reduced CH4 conversion. Solar-to-fuel energy conversion efficiency namely the ratio of the calorific value of produced syngas to the total energy input (solar power and calorific value of converted methane) and CH4 conversion were achieved in the range of 2.9–5.6% and 40.1–68.5% respectively.
Kinetic Modeling and Quantum Yields: Hydrogen Production via Pd‐TiO2 Photocatalytic Water Splitting under Near‐UV and Visible Light
Jan 2022
Publication
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.
Promotion Effect of Proton-conducting Oxide BaZr0.1Ce0.7Y0.2O3−δ on the Catalytic Activity of Ni Towards Ammonia Synthesis from Hydrogen and Nitrogen
Aug 2018
Publication
In this report for the first time it has been observed that proton-conducting oxide BaZr0.1Ce0.7Y0.2O3−δ (BZCY) has significant promotion effect on the catalytic activity of Ni towards ammonia synthesis from hydrogen and nitrogen. Renewable hydrogen can be used for ammonia synthesis to save CO2 emission. By investigating the operating parameters of the reaction the optimal conditions for this catalyst were identified. It was found that at 620 °C with a total flow rate of 200 mL min−1 and a H2/N2 mol ratio of 3 an activity of approximately 250 μmol g−1 h−1 can be achieved. This is ten times larger than that for the unpromoted Ni catalyst under the same conditions although the stability of both catalysts in the presence of steam was not good. The specific activity of Ni supported on proton-conducting oxide BZCY is approximately 72 times higher than that of Ni supported on non-proton conductor MgO-CeO2. These promotion effects were suspected to be due to the proton conducting nature of the support. Therefore it is proposed that the use of proton conducting support materials with highly active ammonia synthesis catalysts such as Ru and Fe will provide improved activity of at lower temperatures.
Simulations of Hydrogen Production by Methanol Steam Reforming
Jan 2019
Publication
Methanol is regarded as an important feedstock for hydrogen production due to its high energy density and superior transportability. A tubular packed-bed reactor performing the methanol steam reforming (MSR) process was modeled by adopting computational fluid dynamics (CFD) software to analyze its performance. Kinetic parameters of the reactions were adjusted according to the literatures and our previous experimental results. The methanol conversion the hydrogen production rate and the CO concentration in the produced mixture were evaluated by considering different levels of the length and temperature of the catalyst bed the steam-to-carbon ratio and the space velocity of the feedstocks. Moreover the correlation between the dimensionless parameter Damköhler number and the methanol conversion was also investigated.
CCS Deployment at Dispersed Industrial Sites: Element Energy for the Department for Business Energy and Industrial Strategy (BEIS)
Aug 2020
Publication
This report identifies and assesses a range of high-level deployment options for industrial carbon capture usage and storage (CCUS) technology located in non-clustered ‘dispersed’ sites that are isolated from potential carbon dioxide transport infrastructure in the UK.
It provides:
It provides:
- an identification of the challenges and barriers to CCUS deployment specifically at these dispersed sites
- an appraisal of the range of high-level options for CCUS deployment and the risks associated with each challenge
- an assessment of the most promising options based on their cost risk and emission reduction potential
- BEIS commissioned Element Energy to produce the report.
Magnesium Gasar as a Potential Monolithic Hydrogen Absorbent
Feb 2021
Publication
The study focuses on the aspect of using the structure of gasars i.e. materials with directed open porosity as a potential hydrogen storage. The structure of the tested gasar is composed of a large number of thin open tubular pores running through the entire longitudinal section of the sample. This allows hydrogen to easily penetrate into the entire sample volume. The analysis of pore distribution showed that the longest diffusion path needed for full penetration of the metal structure with hydrogen is about L = 50–70 μm regardless of the external dimensions of the sample. Attempts to hydrogenate the magnesium gasar structure have shown its ability to accumulate hydrogen at a level of 1 wt%. The obtained results were compared with the best result was obtained for the ZK60 alloy after equal channel angular pressing (ECAP) and crushed to a powder form. The result obtained exceeded 4 wt% of hydrogen accumulated in the metal structure at theoretical 6.9 wt% maximum capacity. A model analysis of the theoretic absorption capacity of pure magnesium was also carried out based on the concentration of vacancies in the metal structure. The theoretical results obtained correlate well with experimental data.
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.
Acid Acceleration of Hydrogen Generation Using Seawater as a Reactant
Jul 2016
Publication
The present study describes hydrogen generation from NaBH4 in the presence of acid accelerator boric oxide or B2O3 using seawater as a reactant. Reaction times and temperatures are adjusted using various delivery methods: bulk addition funnel and metering pump. It is found that the transition metal catalysts typically used to generate hydrogen gas are poisoned by seawater. B2O3 is not poisoned by seawater; in fact reaction times are considerably faster in seawater using B2O3. Reaction times and temperatures are compared for pure water and seawater for each delivery method. It is found that using B2O3 with pure water bulk addition is 97% complete in 3 min; pump metering provides a convenient method to extend the time to 27 min a factor of 9 increase above bulk addition. Using B2O3 with seawater as a reactant bulk addition is 97% complete in 1.35 min; pump metering extends the time to 23 min a factor of 17 increase above bulk. A second acid accelerator sodium bisulfate or NaHSO4 is investigated here for use with NaBH4 in seawater. Because it is non-reactive in seawater i.e. no spontaneous H2 generation NaHSO4 can be stored as a solution in seawater; because of its large solubility it is ready to be metered into NaBH4. With NaHSO4 in seawater pump metering increases the time to 97% completion from 3.4 min to 21 min. Metering allows the instantaneous flow rate of H2 and reaction times and temperatures to be tailored to a particular application. In one application the seawater hydrogen generator characterized here is ideal for supplying H2 gas directly to Proton Exchange Membrane fuel cells in sea surface or subsea environments where a reliable source of power is needed.
Techno-economic Analysis of In-situ Production by Electrolysis, Biomass Gasification and Delivery Systems for Hydrogen Refuelling Stations: Rome Case Study
Oct 2018
Publication
Starting from the Rome Hydrogen Refuelling Station demand of 65 kg/day techno-economics of production systems and balance of plant for small scale stations have been analysed. A sensitivity analysis has been done on Levelised Cost of Hydrogen (LCOH) in the range of 0 to 400 kg/day varying capacity factor and availability hours or travel distance for alkaline electrolysers biomass gasification and hydrogen delivery. As expected minimum LCOH for electrolyser and gasifier is found at 400 kg/day and 24 h/day equal to 12.71 €/kg and 5.99 €/kg however for operating hours over 12 and 10 h/day the differential cost reaches a plateau (below 5%) for electrolyser and gasifier respectively. For the Rome station design 160 kWe of electrolysers 24 h/day and 100 kWth gasifier at 8 h/day LCOH (11.85 €/kg) was calculated considering the modification of the cost structure due to the existing equipment which is convenient respect the use of a single technology except for 24 h/day gasification.
Kinetics Study and Modelling of Steam Methane Reforming Process Over a NiO/Al2O3 Catalyst in an Adiabatic Packed Bed Reactor
Dec 2016
Publication
Kinetic rate data for steam methane reforming (SMR) coupled with water gas shift (WGS) over an 18 wt. % NiO/α-Al2O3 catalyst are presented in the temperature range of 300–700 °C at 1 bar. The experiments were performed in a plug flow reactor under the conditions of diffusion limitations and away from the equilibrium conditions. The kinetic model was implemented in a one-dimensional heterogeneous mathematical model of catalytic packed bed reactor developed on gPROMS model builder 4.1.0®. The mathematical model of SMR process was simulated and the model was validated by comparing the results with the experimental values. The simulation results were in excellent agreement with the experimental results. The effect of various operating parameters such as temperature pressure and steam to carbon ratio on fuel and water conversion (%) H2 yield (wt. % of CH4) and H2 purity was modelled and compared with the equilibrium values.
Electronic Structure and d-Band Center Control Engineering over Ni-Doped CoP3 Nanowall Arrays for Boosting Hydrogen Production
Jun 2021
Publication
To address the challenge of highly efficient water splitting into H2 successful fabrication of novel porous three-dimensional Ni-doped CoP3 nanowall arrays on carbon cloth was realized resulting in an effective self-supported electrode for the electrocatalytic hydrogen-evolution reaction. The synthesized samples exhibit rough curly and porous structures which are beneficial for gaseous transfer and diffusion during the electrocatalytic process. As expected the obtained Ni-doped CoP3 nanowall arrays with a doping concentration of 7% exhibit the promoted electrocatalytic activity. The achieved overpotentials of 176 mV for the hydrogen-evolution reaction afford a current density of 100 mA cm−2 which indicates that electrocatalytic performance can be dramatically enhanced via Ni doping. The Ni-doped CoP3 electrocatalysts with increasing catalytic activity should have significant potential in the field of water splitting into H2. This study also opens an avenue for further enhancement of electrocatalytic performance through tuning of electronic structure and d-band center by doping.
An Extended Flamelet-based Presumed Probability Density Function for Predicting Mean Concentrations of Various Species in Premixed Turbulent Flames
Sep 2020
Publication
Direct Numerical Simulation (DNS) data obtained by Dave and Chaudhuri (2020) from a lean complex-chemistry hydrogen-air flame associated with the thin-reaction-zone regime of premixed turbulent burning are analyzed to perform a priori assessment of predictive capabilities of the flamelet approach for evaluating mean species concentrations. For this purpose dependencies of mole fractions and rates of production of various species on a combustion progress variable c obtained from the laminar flame are averaged adopting either the actual Probability Density Function (PDF) P (c) extracted from the DNS data or a common presumed β-function PDF. On the one hand the results quantitatively validate the flamelet approach for the mean mole fractions of all species including radicals but only if the actual PDF P (c) is adopted. The use of the β-function PDF yields substantially worse results for the radicals’ concentrations. These findings put modeling the PDF P (c) on the forefront of the research agenda. On the other hand the mean rate of product creation and turbulent burning velocity are poorly predicted even adopting the actual PDF. These results imply that in order to evaluate the mean species concentrations the flamelet approach could be coupled with another model that predicts the mean rate and turbulent burning velocity better. Accordingly the flamelet approach could be implemented as post-processing of numerical data yielded by that model. Based on the aforementioned findings and implications a new approach to building a presumed PDF is developed. The key features of the approach consist in (i) adopting a re-normalized flamelet PDF for intermediate values of c and (ii) directly using the mean rate of product creation to calibrate the presumed PDF. Capabilities of the newly developed PDF for predicting mean species concentrations are quantitively validated for all species including radicals.
Integration of Gas Switching Combustion and Membrane Reactors for Exceeding 50% Efficiency in Flexible IGCC Plants with Near-zero CO2 Emissions
Jul 2020
Publication
Thermal power plants face substantial challenges to remain competitive in energy systems with high shares of variable renewables especially inflexible integrated gasification combined cycles (IGCC). This study addresses this challenge through the integration of Gas Switching Combustion (GSC) and Membrane Assisted Water Gas Shift (MAWGS) reactors in an IGCC plant for flexible electricity and/or H2 production with inherent CO2 capture. When electricity prices are high H2 from the MAWGS reactor is used for added firing after the GSC reactors to reach the high turbine inlet temperature of the H-class gas turbine. In periods of low electricity prices the turbine operates at 10% of its rated power to satisfy the internal electricity demand while a large portion of the syngas heating value is extracted as H2 in the MAWGS reactor and sold to the market. This product flexibility allows the inflexible process units such as gasification gas treating air separation unit and CO2 compression transport and storage to operate continuously while the plant supplies variable power output. Two configurations of the GSC-MAWGS plant are presented. The base configuration achieves 47.2% electric efficiency and 56.6% equivalent hydrogen production efficiency with 94.8–95.6% CO2 capture. An advanced scheme using the GSC reduction gases for coal-water slurry preheating and pre-gasification reached an electric efficiency of 50.3% hydrogen efficiency of 62.4% and CO2 capture ratio of 98.1–99.5%. The efficiency is 8.4%-points higher than the pre-combustion CO2 capture benchmark and only 1.9%-points below the unabated IGCC benchmark.
Renewable Hydrogen Production from the Organic Fraction of Municipal Solid Waste through a Novel Carbon-negative Process Concept
Apr 2022
Publication
Bioenergy with carbon capture and storage (BECCS) is one of the prevailing negative carbon emission technologies. Ensuring a hydrogen economy is essential to achieving the carbon-neutral goal. In this regard the present study contributed by proposing a carbon negative process for producing high purity hydrogen from the organic fraction of municipal solid waste (OFMSW). This integrated process comprises anaerobic digestion pyrolysis catalytic reforming water-gas shift and pressure swing adsorption technologies. By focusing on Sweden the proposed process was developed and evaluated through sensitivity analysis mass and energy balance calculations techno-economic assessment and practical feasibility analysis. By employing the optimum operating conditions from the sensitivity analysis 72.2 kg H2 and 701.47 kg negative CO2 equivalent emissions were obtained by treating 1 ton of dry OFMSW. To achieve these results 6621.4 MJ electricity and 325 kg of steam were utilized during this process. Based on this techno-economic assessment of implementing the proposed process in Stockholm when the negative CO2 equivalent emissions are recognized as income the internal rate of return and the discounted payback period can be obtained as 26% and 4.3 years respectively. Otherwise these values will be 13% and 7.2 years.
A Novel Self-Assembly Strategy for the Fabrication of Nano-Hybrid Satellite Materials with Plasmonically Enhanced Catalytic Activity
Jun 2021
Publication
The generation of hydrogen from water using light is currently one of the most promising alternative energy sources for humankind but faces significant barriers for large-scale applications due to the low efficiency of existing photo-catalysts. In this work we propose a new route to fabricate nano-hybrid materials able to deliver enhanced photo-catalytic hydrogen evolution combining within the same nanostructure a plasmonic antenna nanoparticle and semiconductor quantum dots (QDs). For each stage of our fabrication process we probed the chemical composition of the materials with nanometric spatial resolution allowing us to demonstrate that the final product is composed of a silver nanoparticle (AgNP) plasmonic core surrounded by satellite Pt decorated CdS QDs (CdS@Pt) separated by a spacer layer of SiO2 with well-controlled thickness. This new type of photoactive nanomaterial is capable of generating hydrogen when irradiated with visible light displaying efficiencies 300% higher than the constituting photo-active components. This work may open new avenues for the development of cleaner and more efficient energy sources based on photo-activated hydrogen generation.
Integration of Chemical Looping Combustion for Cost-effective CO2 Capture from State-of-the-art Natural Gas Combined Cycles
May 2020
Publication
Chemical looping combustion (CLC) is a promising method for power production with integrated CO2 capture with almost no direct energy penalty. When integrated into a natural gas combined cycle (NGCC) plant however CLC imposes a large indirect energy penalty because the maximum achievable reactor temperature is far below the firing temperature of state-of-the-art gas turbines. This study presents a techno-economic assessment of a CLC plant that circumvents this limitation via an added combustor after the CLC reactors. Without the added combustor the energy penalty amounts to 11.4%-points causing a high CO2 avoidance cost of $117.3/ton which is more expensive than a conventional NGCC plant with post-combustion capture ($93.8/ton) with an energy penalty of 8.1%-points. This conventional CLC plant would also require a custom gas turbine. With an added combustor fired by natural gas a standard gas turbine can be deployed and CO2 avoidance costs are reduced to $60.3/ton mainly due to a reduction in the energy penalty to only 1.4%-points. However due to the added natural gas combustion after the CLC reactor CO2 avoidance is only 52.4%. Achieving high CO2 avoidance requires firing with clean hydrogen instead increasing the CO2 avoidance cost to $96.3/ton when a hydrogen cost of $15.5/GJ is assumed. Advanced heat integration could reduce the CO2 avoidance cost to $90.3/ton by lowering the energy penalty to only 0.6%-points. An attractive alternative is therefore to construct the plant for added firing with natural gas and retrofit the added combustor for hydrogen firing when CO2 prices reach very high levels.
Hydrogen Production as a Clean Energy Carrier through Heterojunction Semiconductors for Environmental Remediation
Apr 2022
Publication
Today as a result of the advancement of technology and increasing environmental problems the need for clean energy has considerably increased. In this regard hydrogen which is a clean and sustainable energy carrier with high energy density is among the well-regarded and effective means to deliver and store energy and can also be used for environmental remediation purposes. Renewable hydrogen energy carriers can successfully substitute fossil fuels and decrease carbon dioxide (CO2 ) emissions and reduce the rate of global warming. Hydrogen generation from sustainable solar energy and water sources is an environmentally friendly resolution for growing global energy demands. Among various solar hydrogen production routes semiconductor-based photocatalysis seems a promising scheme that is mainly performed using two kinds of homogeneous and heterogeneous methods of which the latter is more advantageous. During semiconductor-based heterogeneous photocatalysis a solid material is stimulated by exposure to light and generates an electron–hole pair that subsequently takes part in redox reactions leading to hydrogen production. This review paper tries to thoroughly introduce and discuss various semiconductor-based photocatalysis processes for environmental remediation with a specific focus on heterojunction semiconductors with the hope that it will pave the way for new designs with higher performance to protect the environment.
Smart Designs of Mo Based Electrocatalysts for Hydrogen Evolution Reaction
Dec 2021
Publication
As a sustainable and clean energy source hydrogen can be generated by electrolytic water splitting (i.e. a hydrogen evolution reaction HER). Compared with conventional noble metal catalysts (e.g. Pt) Mo based materials have been deemed as a promising alternative with a relatively low cost and comparable catalytic performances. In this review we demonstrate a comprehensive summary of various Mo based materials such as MoO2 MoS2 and Mo2C. Moreover state of the art designs of the catalyst structures are presented to improve the activity and stability for hydrogen evolution including Mo based carbon composites heteroatom doping and heterostructure construction. The structure–performance relationships relating to the number of active sites electron/ion conductivity H/H2O binding and activation energy as well as hydrophilicity are discussed in depth. Finally conclusive remarks and future works are proposed.
Self-sustainable Protonic Ceramic Electrochemical cells Using a Triple Conducting Electrode for Hydrogen and Power Production
Apr 2020
Publication
The protonic ceramic electrochemical cell (PCEC) is an emerging and attractive technology that converts energy between power and hydrogen using solid oxide proton conductors at intermediate temperatures. To achieve efficient electrochemical hydrogen and power production with stable operation highly robust and durable electrodes are urgently desired to facilitate water oxidation and oxygen reduction reactions which are the critical steps for both electrolysis and fuel cell operation especially at reduced temperatures. In this study a triple conducting oxide of PrNi0.5Co0.5O3-δ perovskite is developed as an oxygen electrode presenting superior electrochemical performance at 400~600 °C. More importantly the self-sustainable and reversible operation is successfully demonstrated by converting the generated hydrogen in electrolysis mode to electricity without any hydrogen addition. The excellent electrocatalytic activity is attributed to the considerable proton conduction as confirmed by hydrogen permeation experiment remarkable hydration behavior and computations.
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