Production & Supply Chain
Comparative Analysis of Energy and Exergy Performance of Hydrogen Production Methods
Nov 2020
Publication
The study of the viability of hydrogen production as a sustainable energy source is a current challenge to satisfy the great world energy demand. There are several techniques to produce hydrogen either mature or under development. The election of the hydrogen production method will have a high impact on practical sustainability of the hydrogen economy. An important profile for the viability of a process is the calculation of energy and exergy efficiencies as well as their overall integration into the circular economy. To carry out theoretical energy and exergy analyses we have estimated proposed hydrogen production using different software (DWSIM and MATLAB) and reference conditions. The analysis consolidates methane reforming or auto-thermal reforming as the viable technologies at the present state of the art with reasonable energy and exergy efficiencies but pending on the impact of environmental constraints as CO2 emission countermeasures. However natural gas or electrolysis show very promising results and should be advanced in their technological and maturity scaling. Electrolysis shows a very good exergy efficiency due to the fact that electricity itself is a high exergy source. Pyrolysis exergy loses are mostly in the form of solid carbon material which has a very high integration potential into the hydrogen economy.
Evaluation of Stability and Catalytic Activity of Ni Catalysts for Hydrogen Production by Biomass Gasification in Supercritical Water
Mar 2019
Publication
Supercritical water gasification is a promising technology for wet biomass utilization. In this paper Ni and other metal catalysts were synthesized by wet impregnation. The stability and catalytic activities of Ni catalysts were evaluated. Firstly catalytic activities of Ni Fe Cu catalysts supported on MgO were tested using wheat straw as raw material in a batch reactor at 723 K and water density of 0.07 cm3/g. Experimental results showed that the order of metal catalyst activity for hydrogen generation was Ni/MgO > Fe/MgO > Cu/MgO. Secondly the influence of different supports on Ni catalysts performance was investigated. The results showed that the order of the Ni catalysts’ activity with different supports was Ni/MgO > Ni/ZnO > Ni/Al2O3 > Ni/ZrO2. Finally the effects of Ni loading and the amount of Ni catalyst addition on hydrogen production and the stability of Ni/MgO catalyst were studied. It was found that serious deactivation of Ni catalyst in the process of supercritical water gasification took place. Even if carbon deposited on the catalyst surface was removed by high temperature calcination and the catalyst was reduced with hydrogen the activity of used catalyst was only partially restored.
Thermodynamic Analysis of Solid Oxide Electrolyzer Integration with Engine Waste Heat Recovery for Hydrogen Production
Jul 2021
Publication
Water electrolysis based on solid oxide electrolysis cell (SOEC) exhibits high conversion efficiency due to part of energy demand can be derived from thermal energy. Therefore it can be integrated with other sources of thermal energy to reduce the consumption of electrical energy. In this paper a diesel engine is integrated with the SOEC stacks for heat recovery steam generator (HRSG). The thermal energy from the engine exhaust gas used to heat the inlet H2O of the SOEC is carried out as the integration case. A SOEC plant using electricity as the thermal heat input is selected as the base case. Thermodynamic analysis of the benchmark and integration scheme reveals that an electrical efficiency of 73.12% and 85.17% can be achieved respectively. The diesel to power efficiency can be increased to 70% when the exhaust gas is completely utilized by the SOEC system. The impacts of some key parameters including current density and operating temperature on system performance have also been conducted and found that the system has optimized parameters of current density and operating temperature to achieve better performance.
Boosting the H2 Production Efficiency via Photocatalytic Organic Reforming: The Role of Additional Hole Scavenging System
Nov 2021
Publication
The simultaneous photocatalytic H2 evolution with environmental remediation over semiconducting metal oxides is a fascinating process for sustainable fuel production. However most of the previously reported photocatalytic reforming showed nonstoichiometric amounts of the evolved H2 when organic substrates were used. To explain the reasons for this phenomenon a careful analysis of the products and intermediates in gas and aqueous phases upon the photocatalytic hydrogen evolution from oxalic acid using Pt/TiO2 was performed. A quadrupole mass spectrometer (QMS) was used for the continuous flow monitoring of the evolved gases while high performance ion chromatography (HPIC) isotopic labeling and electron paramagnetic resonance (EPR) were employed to understand the reactions in the solution. The entire consumption of oxalic acid led to a ~30% lower H2 amount than theoretically expected. Due to the contribution of the photoKolbe reaction mechanism a tiny amount of formic acid was produced then disappeared shortly after the complete consumption of oxalic acid. Nevertheless a much lower concentration of formic acid was generated compared to the nonstoichiometric difference between the formed H2 and the consumed oxalic acid. Isotopic labeling measurements showed that the evolved H2 HD and/or D2 matched those of the solvent; however using D2O decreased the reaction rate. Interestingly the presence of KI as an additional hole scavenger with oxalic acid had a considerable impact on the reaction mechanism and thus the hydrogen yield as indicated by the QMS and the EPR measurements. The added KI promoted H2 evolution to reach the theoretically predictable amount and inhibited the formation of intermediates without affecting the oxalic acid degradation rate. The proposed mechanism by which KI boosts the photocatalytic performance is of great importance in enhancing the overall energy efficiency for hydrogen production via photocatalytic organic reforming.
Cost Benefit Analysis for Green Hydrogen Production from Treated Effluent: The Case Study of Oman
Nov 2022
Publication
Recently the management of water and wastewater is gaining attention worldwide as a way of conserving the natural resources on the planet. The traditional wastewater treatment in Oman is such that the treated effluent produced is only reused for unfeasible purposes such as landscape irrigation cooling or disposed of in the sea. Introducing more progressive reuse applications can result in achieving a circular economy by considering treated effluent as a source of producing new products. Accordingly wastewater treatment plants can provide feedstock for green hydrogen production processes. The involvement of the wastewater industry in the green pathway of production scores major points in achieving decarbonization. In this paper the technical and economic feasibility of green hydrogen production in Oman was carried out using a new technique that would help explore the benefits of the treated effluent from wastewater treatment in Oman. The feasibility study was conducted using the Al Ansab sewage treatment plant in the governate of Muscat in Wilayat (region) Bousher. The results have shown that the revenue from Al Ansab STP in a conventional case is 7.02 million OMR/year while sustainable alternatives to produce hydrogen from the Proton Exchange Membrane (PEM) electrolyzer system for two cases with capacities of 1500 kg H2/day and 50000 kg H2/day would produce revenue of 8.30 million OMR/year and 49.73 million OMR/year respectively.
Hydrogen Production from Sea Wave for Alternative Energy Vehicles for Public Transport in Trapani (Italy)
Oct 2016
Publication
The coupling of renewable energy and hydrogen technologies represents in the mid-term a very interesting way to match the tasks of increasing the reliable exploitation of wind and sea wave energy and introducing clean technologies in the transportation sector. This paper presents two different feasibility studies: the first proposes two plants based on wind and sea wave resource for the production storage and distribution of hydrogen for public transportation facilities in the West Sicily; the second applies the same approach to Pantelleria (a smaller island) including also some indications about solar resource. In both cases all buses will be equipped with fuel-cells. A first economic analysis is presented together with the assessment of the avoidable greenhouse gas emissions during the operation phase. The scenarios addressed permit to correlate the demand of urban transport to renewable resources present in the territories and to the modern technologies available for the production of hydrogen from renewable energies. The study focuses on the possibility of tapping the renewable energy potential (wind and sea wave) for the hydrogen production by electrolysis. The use of hydrogen would significantly reduce emissions of particulate matter and greenhouse gases in urban districts under analysis. The procedures applied in the present article as well as the main equations used are the result of previous applications made in different technical fields that show a good replicability.
Methanol Electrolysis for Hydrogen Production Using Polymer Electrolyte Membrane: A Mini-Review
Nov 2020
Publication
Hydrogen (H2) has attained significant benefits as an energy carrier due to its gross calorific value (GCV) and inherently clean operation. Thus hydrogen as a fuel can lead to global sustainability. Conventional H2 production is predominantly through fossil fuels and electrolysis is now identified to be most promising for H2 generation. This review describes the recent state of the art and challenges on ultra-pure H2 production through methanol electrolysis that incorporate polymer electrolyte membrane (PEM). It also discusses about the methanol electrochemical reforming catalysts as well as the impact of this process via PEM. The efficiency of H2 production depends on the different components of the PEM fuel cells which are bipolar plates current collector and membrane electrode assembly. The efficiency also changes with the nature and type of the fuel fuel/oxygen ratio pressure temperature humidity cell potential and interfacial electronic level interaction between the redox levels of electrolyte and band gap edges of the semiconductor membranes. Diverse operating conditions such as concentration of methanol cell temperature catalyst loading membrane thickness and cell voltage that affect the performance are critically addressed. Comparison of various methanol electrolyzer systems are performed to validate the significance of methanol economy to match the future sustainable energy demands.
Non-alloy Mg Anode for Ni-MH Batteries: Multiple Approaches Towards a Stable Cycling Performance
Apr 2021
Publication
Mg attracts much research interest as anode material for Ni-MH batteries thanks to its lightweight cost-effectiveness and high theoretical capacity (2200 mA h g−1). However its practical application is tremendously challenged by the poor hydrogen sorption kinetics passivation from aggressive aqueous electrolytes and insulating nature of MgH2. Mg-based alloys exhibit enhanced hydrogen sorption kinetics and electrical conductivity but significant amount of costly transition metal elements are required. In this work we have for the first time utilized non-alloyed but catalyzed Mg as anode for Ni-MH batteries. 5 mol.% TiF3 was added to nanosized Mg for accelerating the hydrogen sorption kinetics. Several strategies for preventing the problematic passivation of Mg have been studied including protective encapsulation of the electrode and utilizing room-temperature/high-temperature ionic liquids and an alkaline polymer membrane as working electrolyte. Promising electrochemical performance has been achieved in this Mg–TiF3 composite anode based Ni-MH batteries with room for further improvements.
Assessment of Fossil-free Steelmaking Based on Direct Reduction Applying High-temperature Electrolysis
Jun 2021
Publication
Preventing humanity from serious impact of climate crisis requires carbon neutrality across all economic sectors including steel industry. Although fossil-free steelmaking routes receiving increasing attention fundamental process aspects especially approaches towards the improvement of efficiency and flexibility are so far not comprehensively studied. In this paper optimized process concepts allowing for a gradual transition towards fossil-free steelmaking based on the coupling of direct reduction process electric arc furnace and electrolysis are presented. Both a high-temperature and low-temperature electrolysis were modeled and possibilities for the integration into existing infrastructure are discussed. Various schemes for heat integration especially when using high-temperature electrolysis are highlighted and quantified. It is demonstrated that the considered direct reduction-based process concepts allow for a high degree of flexibility in terms of feed gas composition when partially using natural gas as a bridge technology. This allows for an implementation in the near future as well as the possibility of supplying power grid services in a renewable energy system. Furthermore it is shown that an emission reduction potential of up to 97.8% can be achieved with a hydrogen-based process route and 99% with a syngas-based process route respectively provided that renewable electricity is used.
Carbon-Negative Hydrogen Production (HyBECCS) from Organic Waste Materials in Germany: How to Estimate Bioenergy and Greenhouse Gas Mitigation Potential
Nov 2021
Publication
Hydrogen derived from biomass feedstock (biohydrogen) can play a significant role in Germany’s hydrogen economy. However the bioenergy potential and environmental benefits of biohydrogen production are still largely unknown. Additionally there are no uniform evaluation methods present for these emerging technologies. Therefore this paper presents a methodological approach for the evaluation of bioenergy potentials and the attainable environmental impacts of these processes in terms of their carbon footprints. A procedure for determining bioenergy potentials is presented which provides information on the amount of usable energy after conversion when applied. Therefore it elaborates a four-step methodical conduct dealing with available waste materials uncertainties of early-stage processes and calculation aspects. The bioenergy to be generated can result in carbon emission savings by substituting fossil energy carriers as well as in negative emissions by applying biohydrogen production with carbon capture and storage (HyBECCS). Hence a procedure for determining the negative emissions potential is also presented. Moreover the developed approach can also serve as a guideline for decision makers in research industry and politics and might also serve as a basis for further investigations such as implementation strategies or quantification of the benefits of biohydrogen production from organic waste material in Germany
Effect of TiO2 on Electrocatalytic Behavior of Ni-Mo Alloy Coating for Hydrogen Energy
Jun 2018
Publication
Ni-Mo-TiO2 composite coating has been developed through electrodeposition method by depositing titanium dioxide (TiO2) nanoparticles parallel to the process of Ni-Mo alloy coating. The experimental results explaining the increased electrocatalytic activity of Ni-Mo alloy coating on incorporation of TiO2 nanoparticles into its alloy matrix is reported here. The effect of addition of TiO2 on composition morphology and phase structure of TiO2 – composite coating is studied with special emphasis on its electrocatalytic activity for hydrogen evolution reaction (HER) in 1.0 M KOH solution. The electrocatalytic activity of alloy coatings were validated using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Under optimal condition TiO2 – composite alloy coating represented as (Ni-Mo-TiO2)2.0 A dm 2 is found to exhibit the highest electrocatalytic activity for HER compared to its binary alloy counterpart. The increased electrocatalytic activity of (Ni-Mo-TiO2)2.0 A dm 2 composite coating was attributed to the increased Mo content porosity and roughness of coating affected due to addition of TiO2 nanoparticles supported by SEM EDX XRD and AFM study. The increased electrocatalytic activity of (Ni-Mo-TiO2)2.0 A dm 2 coating was found due to decreased Rct and increased Cdl values demonstrated by EIS study. Better electrocatalytic activity of (Ni-Mo-TiO2)2.0 A dm 2 coating compared to (Ni-Mo)2.0 A dm 2 coating has been explained through mechanism. Experimental study revealed that (Ni-Mo-TiO2)2.0 A dm 2 composite coating follows Volmer-Heyrovsky mechanism compared to Tafel mechanism in case of (Ni-Mo-TiO2)2.0 A dm 2 coating assessed on the basis of Tafel slopes.
Cost-optimized Design Point and Operating Strategy of Polymer Electrolyte Membrane Electrolyzers
Nov 2022
Publication
Green hydrogen is a key solution for reducing CO2 emissions in various industrial applications but high production costs continue to hinder its market penetration today. Better competitiveness is linked to lower investment costs and higher efficiency of the conversion technologies among which polymer electrolyte membrane electrolysis seems to be attractive. Although new manufacturing techniques and materials can help achieve these goals a less frequently investigated approach is the optimization of the design point and operating strategy of electrolyzers. This means in particular that the questions of how often a system should be operated and which cell voltage should be applied must be answered. As existing techno-economic models feature gaps which means that these questions cannot be adequately answered a modified model is introduced here. In this model different technical parameters are implemented and correlated to each other in order to simulate the lowest possible levelized cost of hydrogen and extract the required designs and strategies from this. In each case investigated the recommended cost-based cell voltage that should be applied to the system is surprisingly low compared to the assumptions made in previous publications. Depending on the case the cell voltage is in a range between 1.6 V and 1.8 V with an annual operation of 2000e8000 h. The wide range of results clearly indicate how individual the design and operation must be but with efficiency gains of several percent the effect of optimization will be indispensable in the future.
Techno-economic Assessment of Offshore Wind-to-hydrogen Scenarios: A UK Case Study
Jan 2023
Publication
The installed capacity electricity generation from wind and the curtailment of wind power in the UK between 2011 and 2021 showed that penetration levels of wind energy and the amount of energy that is curtailed in future would continue to rise whereas the curtailed energy could be utilised to produce green hydrogen. In this study data were collected technologies were chosen systems were designed and simulation models were developed to determine technical requirements and levelised costs of hydrogen produced and transported through different pathways. The analysis of capital and operating costs of the main components used for onshore and offshore green hydrogen production using offshore wind including alternative strategies for hydrogen storage and transport and hydrogen carriers showed that a significant reduction in cost could be achieved by 2030 enabling the production of green hydrogen from offshore wind at a competitive cost compared to grey and blue hydrogen. Among all scenarios investigated in this study compressed hydrogen produced offshore is the most cost-effective scenario for projects starting in 2025 although the economic feasibility of this scenario is strongly affected by the storage period and the distance to the shore of the offshore wind farm. Alternative scenarios for hydrogen storage and transport such as liquefied hydrogen and methylcyclohexane could become more cost-effective for projects starting in 2050 when the levelised cost of hydrogen could reach values of about £2 per kilogram of hydrogen or lower.
Large-scale Hydrogen Production via Water Electrolysis: A Techno-economic and Environmental Assessment
Jul 2022
Publication
Low-carbon (green) hydrogen can be generated via water electrolysis using photovoltaic wind hydropower or decarbonized grid electricity. This work quantifies current and future costs as well as environmental burdens of large-scale hydrogen production systems on geographical islands which exhibit high renewable energy potentials and could act as hydrogen export hubs. Different hydrogen production configurations are examined considering a daily hydrogen production rate of 10 tonnes on hydrogen production costs life cycle greenhouse gas emissions material utilization and land transformation. The results demonstrate that electrolytic hydrogen production costs of 3.7 Euro per kg H2 are within reach today and that a reduction to 2 Euro per kg H2 in year 2040 is likely hence approaching cost parity with hydrogen from natural gas reforming even when applying ‘‘historical’’ natural gas prices. The recent surge of natural gas prices shows that cost parity between green and grey hydrogen can already be achieved today. Producing hydrogen via water electrolysis with low costs and low GHG emissions is only possible at very specific locations nowadays. Hybrid configurations using different electricity supply options demonstrate the best economic performance in combination with low environmental burdens. Autonomous hydrogen production systems are especially effective to produce low-carbon hydrogen although the production of larger sized system components can exhibit significant environmental burdens and investments. Some materials (especially iridium) and the availability of land can be limiting factors when scaling up green hydrogen production with polymer electrolyte membrane (PEM) electrolyzers. This implies that decision-makers should consider aspects beyond costs and GHG emissions when designing large-scale hydrogen production systems to avoid risks coming along with the supply of for example scarce materials
On the Potential of Blue Hydrogen Production in Colombia: A Fossil Resource-Based Assessment for Low-Emission Hydrogen
Sep 2022
Publication
Latin America is starting its energy transition. In Colombia with its abundant natural resources and fossil fuel reserves hydrogen (H2 ) could play a key role. This contribution analyzes the potential of blue H2 production in Colombia as a possible driver of the H2 economy. The study assesses the natural resources available to produce blue H2 in the context of the recently launched National Hydrogen Roadmap. Results indicate that there is great potential for low-emission blue H2 production in Colombia using coal as feedstock. Such potential besides allowing a more sustainable use of non-renewable resources would pave the way for green H2 deployment in Colombia. Blue H2 production from coal could range from 700 to 8000 ktH2 /year by 2050 under conservative and ambitious scenarios respectively which could supply up to 1.5% of the global H2 demand by 2050. However while feedstock availability is promising for blue H2 production carbon dioxide (CO2 ) capture capacities and investment costs could limit this potential in Colombia. Indeed results of this work indicate that capture capacities of 15 to 180 MtCO2 /year (conservative and ambitious scenarios) need to be developed by 2050 and that the required investment for H2 deployment would be above that initially envisioned by the government. Further studies on carbon capture utilization and storage capacity implementation of a clear public policy and a more detailed hydrogen strategy for the inclusion of blue H2 in the energy mix are required for establishing a low-emission H2 economy in the country.
Environmental Impact Assessment of Hydrogen Production via Steam Methane Reforming Based on Emissions Data
Oct 2022
Publication
Steam methane reforming (SMR) using natural gas is the most commonly used technology for hydrogen production. Industrial hydrogen production contributes to pollutant emissions which may differ from the theoretical estimates due to process conditions type and state of installed pollution control equipment. The aim of this study was to estimate the impacts of hydrogen production using facilitylevel real emissions data collected from multiple US EPA databases. The study applied the ReCiPe2016 impact assessment method and considered 12 midpoint and 14 endpoint impacts for 33 US SMR hydrogen production facilities. Global warming impacts were mostly driven by CO2 emissions and contributed to 94.6% of the endpoint impacts on human health while global warming impact on terrestrial ecosystems contributed to 98.3% of the total endpoint impacts on ecosystems. The impacts estimated by direct emissions from the 33 facilities were 9.35 kg CO2e/kg H2 which increased to 11.2 kg CO2e/kg H2 when the full life cycle of hydrogen production including upstream emissions was included. The average global warming impact could be reduced by 5.9% and 11.1% with increases in hydrogen production efficiency by 5% and 10% respectively. Potential impact reductions are also found when natural gas hydrogen production feedstock is replaced by renewable sources with the greatest reduction of 78.1% found in hydrogen production via biomass gasification followed by 68.2% reduction in landfill gas and 53.7% reduction in biomethane-derived hydrogen production.
Carbon-negative Hydrogen from Biomass Using Gas Switching Integrated Gasification: Techno-economic Assessment
Sep 2022
Publication
Ambitious decarbonization pathways to limit the global temperature rise to well below 2 ◦C will require largescale CO2 removal from the atmosphere. One promising avenue for achieving this goal is hydrogen production from biomass with CO2 capture. The present study investigates the techno-economic prospects of a novel biomass-to-hydrogen process configuration based on the gas switching integrated gasification (GSIG) concept. GSIG applies the gas switching combustion principle to indirectly combust off-gas fuel from the pressure swing adsorption unit in tubular reactors integrated into the gasifier to improve efficiency and CO2 capture. In this study these efficiency gains facilitated a 5% reduction in the levelized cost of hydrogen (LCOH) relative to conventional O2-blown fluidized bed gasification with pre-combustion CO2 capture even though the larger and more complex gasifier cancelled out the capital cost savings from avoiding the air separation and CO2 capture units. The economic assessment also demonstrated that advanced gas treatment using a tar cracker instead of a direct water wash can further reduce the LCOH by 12% and that the CO2 prices in excess of 100 €/ton consistent with ambitious decarbonization pathways will make this negative-emission technology economically highly attractive. Based on these results further research into the GSIG concept to facilitate more efficient utilization of limited biomass resources can be recommended.
Electric-field-promoted Photo-electrochemical Production of Hydrogen from Water Splitting
Jul 2021
Publication
Given that conversion efficiencies of incident solar radiation to liquid fuels e.g. H2 are of the order of a few percent or less as quantified by ‘solar to hydrogen’ (STH) economically inexpensive and operationally straightforward ways to boost photo-electrochemcial (PEC) H2 production from solar-driven water splitting are important. In this work externally-applied static electric fields have led to enhanced H2 production in an energy-efficient manner with up to ~30–40% increase in H2 (bearing in mind fieldinput energy) in a prototype open-type solar cell featuring rutile/titania and hematite/iron-oxide (Fe2O3) respectively in contact with an alkaline aqueous medium (corresponding to respective relative increases of STH by ~12 and 16%). We have also performed non-equilibrium ab-initio molecular dynamics in both static electric and electromagnetic (e/m) fields for water in contact with a hematite/iron-oxide (0 0 1) surface observing enhanced break-up of water molecules by up to ~70% in the linear-response régime. We discuss the microscopic origin of such enhanced water-splitting based on experimental and simulation-based insights. In particular we external-field direction at the hematite surfaces and scrutinise properties of the adsorbed water molecules and OH– and H3O+ species e.g. hydrogen bonds between water-protons and the hematite surfaces’ bridging oxygen atoms as well as interactions between oxygen atoms in adsorbed water molecules and underlying iron atoms.
Photocatalytic Hydrogen Evolution from Biomass Conversion
Feb 2021
Publication
Biomass has incredible potential as an alternative to fossil fuels for energy production that is sustainable for the future of humanity. Hydrogen evolution from photocatalytic biomass conversion not only produces valuable carbon-free energy in the form of molecular hydrogen but also provides an avenue of production for industrially relevant biomass products. This photocatalytic conversion can be realized with efficient sustainable reaction materials (biomass) and inexhaustible sunlight as the only energy inputs. Reported herein is a general strategy and mechanism for photocatalytic hydrogen evolution from biomass and biomass-derived substrates (including ethanol glycerol formic acid glucose and polysaccharides). Recent advancements in the synthesis and fundamental physical/mechanistic studies of novel photocatalysts for hydrogen evolution from biomass conversion are summarized. Also summarized are recent advancements in hydrogen evolution efciency regarding biomass and biomass-derived substrates. Special emphasis is given to methods that utilize unprocessed biomass as a substrate or synthetic photocatalyst material as the development of such will incur greater benefts towards a sustainable route for the evolution of hydrogen and production of chemical feedstocks.
Decarbonizing Natural Gas: A Review of Catalytic Decomposition and Carbon Formation Mechanisms
Apr 2022
Publication
In the context of energy conservation and the reduction of CO2 emissions inconsistencies between the inevitable emission of CO2 in traditional hydrogen production methods and eco-friendly targets have become more apparent over time. The catalytic decomposition of methane (CDM) is a novel technology capable of producing hydrogen without releasing CO2 . Since hydrogen produced via CDM is neither blue nor green the term “turquoise” is selected to describe this technology. Notably the by-products of methane cracking are simply carbon deposits with different structures which can offset the cost of hydrogen production cost should they be harvested. However the encapsulation of catalysts by such carbon deposits reduces the contact area between said catalysts and methane throughout the CDM process thereby rendering the continuous production of hydrogen impossible. This paper mainly covers the CDM reaction mechanisms of the three common metal-based catalysts (Ni Co Fe) from experimental and modelling approaches. The by-products of carbon modality and the key parameters that affect the carbon formation mechanisms are also discussed.
Hydrogen Production and Carbon Sequestration by Steam Methane Reforming and Fracking with Carbon Dioxide
Feb 2020
Publication
An opportunity to sequester large amounts of carbon dioxide (CO2) is made possible because hydraulic fracturing is used to produce most of America's natural gas. CO2 could be extracted from natural gas and water using steam methane reforming pressurized to its supercritical phase and used instead of water to fracture additional hydrocarbon-bearing rock. The useful energy carrier that remains is hydrogen with carbon returned to the ground. Research on the use of supercritical CO2 is reviewed with proppant entrainment identified as the major area where technical advances may be needed. The large potential for greenhouse-gas reduction through sequestration of CO2 and avoidance of methane leakage from the natural gas system is quantified.
Critical Materials in PEMFC Systems and a LCA Analysis for the Potential Reduction of Environmental Impacts with EoL Strategies
Jul 2019
Publication
Commonly used materials constituting the core components of polymer electrolyte membrane fuel cells (PEMFCs) including the balance‐of‐plant were classified according to the EU criticality methodology with an additional assessment of hazardousness and price. A life‐cycle assessment (LCA) of the materials potentially present in PEMFC systems was performed for 1 g of each material. To demonstrate the importance of appropriate actions at the end of life (EoL) for critical materials a LCA study of the whole life cycle for a 1‐kW PEMFC system and 20000 operating hours was performed. In addition to the manufacturing phase four different scenarios of hydrogen production were analyzed. In the EoL phase recycling was used as a primary strategy with energy extraction and landfill as the second and third. The environmental impacts for 1 g of material show that platinum group metals and precious metals have by far the largest environmental impact; therefore it is necessary to pay special attention to these materials in the EoL phase. The LCA results for the 1‐kW PEMFC system show that in the manufacturing phase the major environmental impacts come from the fuel cell stack where the majority of the critical materials are used. Analysis shows that only 0.75 g of platinum in the manufacturing phase contributes on average 60% of the total environmental impacts of the manufacturing phase. In the operating phase environmentally sounder scenarios are the hydrogen production with water electrolysis using hydroelectricity and natural gas reforming. These two scenarios have lower absolute values for the environmental impact indicators on average compared with the manufacturing phase of the 1‐kW PEMFC system. With proper recycling strategies in the EoL phase for each material and by paying a lot of attention to the critical materials the environmental impacts could be reduced on average by 37.3% for the manufacturing phase and 23.7% for the entire life cycle of the 1‐kW PEMFC system.
Hydrogen Production from Water Electrolysis: Role of Catalysts
Feb 2021
Publication
As a promising substitute for fossil fuels hydrogen has emerged as a clean and renewable energy. A key challenge is the efcient production of hydrogen to meet the commercial-scale demand of hydrogen. Water splitting electrolysis is a promising pathway to achieve the efcient hydrogen production in terms of energy conversion and storage in which catalysis or electrocatalysis plays a critical role. The development of active stable and low-cost catalysts or electrocatalysts is an essential prerequisite for achieving the desired electrocatalytic hydrogen production from water splitting for practical use which constitutes the central focus of this review. It will start with an introduction of the water splitting performance evaluation of various electrocatalysts in terms of activity stability and efciency. This will be followed by outlining current knowledge on the two half-cell reactions hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in terms of reaction mechanisms in alkaline and acidic media. Recent advances in the design and preparation of nanostructured noble-metal and non-noble metal-based electrocatalysts will be dis‑ cussed. New strategies and insights in exploring the synergistic structure morphology composition and active sites of the nanostructured electrocatalysts for increasing the electrocatalytic activity and stability in HER and OER will be highlighted. Finally future challenges and perspectives in the design of active and robust electrocatalysts for HER and OER towards efcient production of hydrogen from water splitting electrolysis will also be outlined.
Recent Advances in Methane Pyrolysis: Turquoise Hydrogen with Solid Carbon Production
Aug 2022
Publication
Beside steam reforming methane pyrolysis is an alternative method for hydrogen production. ‘Turquoise’ hydrogen with solid carbon is formed in the pyrolysis process contrary to ‘grey’ or ‘blue’ hydrogen via steam methane reforming where waste carbon dioxide is produced. Thermal pyrolysis is conducted at higher temperatures but catalytic decomposition of methane (CDM) is a promising route for sustainable hydrogen production. CDM is generally carried out over four types of catalyst: nickel carbon noble metal and iron. The applied reactors can be fixed bed fluidized bed plasma bed or molten-metal reactors. Two main advantages of CDM are that (i) carbon-oxide free hydrogen ideal for fuel cell applications is formed and (ii) the by-product can be tailored into carbon with advanced morphology (e.g. nanofibers nanotubes). The aim of this review is to reveal the very recent research advances of the last two years achieved in the field of this promising prospective technology.
The Role of Offshore Wind Power in Renewable Hydrogen Production
Jan 2023
Publication
We investigate the role of offshore wind in a hybrid system comprising solar PV offshore wind electrical storage (pumped hydro energy storage or battery) and an electrolyser in an off-grid hydrogen production system. Further we capture a wide range of future cost reduction scenarios for offshore wind power and solar PV generation in addition to accounting for future projected falls in electrolyser costs allowing future hydrogen costs to be estimated with a variety of different assumptions. The empirical setting of Australia and incorporation of solar PV as an additional potential source of electricity enables us to examine the contribution of offshore wind to renewable hydrogen production when an low-cost renewable alternative is available. This study complements a small number of studies on opportunities for offshore wind power in the Australian setting (Briggs et al. 2021; Golestani et al. 2021; Aryai et al. 2021) and contributes to research on the potential for offshore wind to contribute to green hydrogen production focused on the crucial Asia-Pacific region (Kim and Kim 2017; Song et al. 2021).<br/>In the following sections we describe the optimization model and the process used for selecting sites used in the study. We then summarize the modelling scenarios and assumptions before outlining the modelling results. We conclude by discussing the implications of the findings.
Forecasting Hydrogen Production from Wind Energy in a Suburban Environment Using Machine Learning
Nov 2022
Publication
The environment is seriously threatened by the rising energy demand and the use of conventional energy sources. Renewable energy sources including hydro solar and wind have been the focus of extensive research due to the proliferation of energy demands and technological advancement. Wind energy is mostly harvested in coastal areas and little work has been done on energy extraction from winds in a suburban environment. The fickle behavior of wind makes it a less attractive renewable energy source. However an energy storage method may be added to store harvested wind energy. The purpose of this study is to evaluate the feasibility of extracting wind energy in terms of hydrogen energy in a suburban environment incorporating artificial intelligence techniques. To this end a site was selected latitude 33.64◦ N longitude 72.98◦ N and elevation 500 m above mean sea level in proximity to hills. One year of wind data consisting of wind speed wind direction and wind gust was collected at 10 min intervals. Subsequently long short-term memory (LSTM) support vector regression (SVR) and linear regression models were trained on the empirically collected data to estimate daily hydrogen production. The results reveal that the overall prediction performance of LSTM was best compared to that of SVR and linear regression models. Furthermore we found that an average of 6.76 kg/day of hydrogen can be produced by a 1.5 MW wind turbine with the help of an artificial intelligence method (LSTM) that is well suited for time-series data to classify process and predict.
Sizing of Hybrid Supercapacitors and Lithium-Ion Batteries for Green Hydrogen Production from PV in the Australian Climate
Feb 2023
Publication
Instead of storing the energy produced by photovoltaic panels in batteries for later use to power electric loads green hydrogen can also be produced and used in transportation heating and as a natural gas alternative. Green hydrogen is produced in a process called electrolysis. Generally the electrolyser can generate hydrogen from a fluctuating power supply such as renewables. However due to the startup time of the electrolyser and electrolyser degradation accelerated by multiple shutdowns an idle mode is required. When in idle mode the electrolyser uses 10% of the rated electrolyser load. An energy management system (EMS) shall be applied where a storage technology such as a lithium-ion capacitor or lithium-ion battery is used. This paper uses a state-machine EMS of PV microgrid for green hydrogen production and energy storage to manage the hydrogen production during the morning from solar power and in the night using the stored energy in the energy storage which is sized for different scenarios using a lithium-ion capacitor and lithium-ion battery. The mission profile and life expectancy of the lithium-ion capacitor and lithium-ion battery are evaluated considering the system’s local irradiance and temperature conditions in the Australian climate. A tradeoff between storage size and cutoffs of hydrogen production as variables of the cost function is evaluated for different scenarios. The lithium-ion capacitor and lithium-ion battery are compared for each tested scenario for an optimum lifetime. It was found that a lithium-ion battery on average is 140% oversized compared to a lithium-ion capacitor but a lithium-ion capacitor has a smaller remaining capacity of 80.2% after ten years of operation due to its higher calendar aging while LiB has 86%. It was also noticed that LiB is more affected by cycling aging while LiC is affected by calendar aging. However the average internal resistance after 10 years for the lithium-ion capacitor is 264% of the initial internal resistance while for lithium-ion battery is 346% making lithium-ion capacitor a better candidate for energy storage if it is used for grid regulation as it requires maintaining a lower internal resistance over the lifetime of the storage.
Parametric Study and Electrocatalyst of Polymer Electrolyte Membrane (PEM) Electrolysis Performance
Jan 2023
Publication
An investigation was conducted to determine the effects of operating parameters for various electrode types on hydrogen gas production through electrolysis as well as to evaluate the efficiency of the polymer electrolyte membrane (PEM) electrolyzer. Deionized (DI) water was fed to a single-cell PEM electrolyzer with an active area of 36 cm2 . Parameters such as power supply (50–500 mA/cm2 ) feed water flow rate (0.5–5 mL/min) water temperature (25−80 ◦C) and type of anode electrocatalyst (0.5 mg/cm2 PtC [60%] 1.5 mg/cm2 IrRuOx with 1.5 mg/cm2 PtB 3.0 mg/cm2 IrRuOx and 3.0 mg/cm2 PtB) were varied. The effects of these parameter changes were then analyzed in terms of the polarization curve hydrogen flowrate power consumption voltaic efficiency and energy efficiency. The best electrolysis performance was observed at a DI water feed flowrate of 2 mL/min and a cell temperature of 70 ◦C using a membrane electrode assembly that has a 3.0 mg/cm2 IrRuOx catalyst at the anode side. This improved performance of the PEM electrolyzer is due to the reduction in activation as well as ohmic losses. Furthermore the energy consumption was optimal when the current density was about 200 mA/cm2 with voltaic and energy efficiencies of 85% and 67.5% respectively. This result indicates low electrical energy consumption which can lower the operating cost and increase the performance of PEM electrolyzers. Therefore the optimal operating parameters are crucial to ensure the ideal performance and durability of the PEM electrolyzer as well as lower its operating costs.
Exergy Estimate of a Novel Hybrid Solar-gas Power and Organic Rankine Cycle-based Hydrogen-production System
Mar 2022
Publication
This study proposes a novel hybrid solar-gas power and hydrogen-production system which is comprised by the solar tower thermal system gas-steam turbine combined cycle and organic Rankine cycle-based hydrogen-production system. Based on the Ebsilon code the operation processes of the hybrid system are simulated. The results show that the output power and electric efficiency of the hybrid system are 103.9 MW and 41.3% and the daily hydrogen output is 62.2 kg. The operation simulation results of the hybrid system reveal that the gas-steam combined cycle and solar island can both achieve stable operations and the power generation section and hydrogen-production device can both work effectively which means the hybrid system is technically feasible. The exergy estimate results of the hybrid system show that the combustion chamber and solar receiver have the two largest exergy destructions which are 56.5 MW and 45.3 MW. That means the performances of the two components can be further improved. For the hydrogen-production system the exergy destructions of the proton exchange membrane electrolyzer turbine condenser and evaporator of the organic Rankine cycle are 0.156 MW 0.111 MW 2.338 MW and 1.891 MW and the corresponding exergy efficiencies are 51.2% 92.6% 80.7% and 79.5% respectively.
Green Hydrogen Production Potential in West Africa – Case of Niger
Jul 2022
Publication
Niger offers the possibility of producing green hydrogen due to its high solar energy potential. Due to the still growing domestic oil and coal industry the use of green hydrogen in the country currently seems unlikely at the higher costs of hydrogen as an energy vector. However the export of green hydrogen to industrialized countries could be an option. In 2020 a hydrogen partnership has been established between Germany and Niger. The potential import of green hydrogen represents an option for Germany and other European countries to decarbonize domestic energy supply. Currently there are no known projects for the electrolytic production of hydrogen in Niger. In this work potential hydrogen demand across electricity and transport sectors is forecasted until 2040. The electricity demand in 2040 is expected at 2934 GWh and the gasoline and diesel demand at 964 m3 and 2181 m3 respectively. Accordingly the total hydrogen needed to supply electricity and the transport sector (e.g. to replace 1% gasoline and diesel demand in 2040) is calculated at 0.0117 Mt. Only a small fraction of 5% of the land area in Niger would be sufficient to generate the required electricity from solar PV to produce hydrogen.
Techno-Economic Assessment of Green Hydrogen Production by an Off-Grid Photovoltaic Energy System
Jan 2023
Publication
Green hydrogen production is essential to meeting the conference of the parties’ (COP) decarbonization goals; however this method of producing hydrogen is not as cost-effective as hydrogen production from fossil fuels. This study analyses an off-grid photovoltaic energy system designed to feed a proton-exchange membrane water electrolyzer for hydrogen production to evaluate the optimal electrolyzer size. The system has been analyzed in Baghdad the capital of Iraq using experimental meteorological data. The 12 kWp photovoltaic array is positioned at the optimal annual tilt angle for the selected site. The temperature effect on photovoltaic modules is taken into consideration. Several electrolyzers with capacities in the range of 2–14 kW were investigated to assess the efficiency and effectiveness of the system. The simulation process was conducted using MATLAB and considering the project life span from 2021 to 2035. The results indicate that various potentially cost-competitive alternatives exist for systems with market combinations resembling renewable hydrogen wholesale. It has been found that the annual energy generated by the analyzed photovoltaic system is 18892 kWh at 4313 operating hours and the obtained hydrogen production cost ranges from USD 5.39/kg to USD 3.23/kg. The optimal electrolyzer capacity matches a 12 kWp PV system equal to 8 kW producing 37.5 kg/year/kWp of hydrogen for USD 3.23/kg.
Synthesis and Characterization of Biogenic Iron Oxides of Different Nanomorphologies from Pomegranate Peels for Efficient Solar Hydrogen Production
Feb 2020
Publication
An eco-friendly green synthesis of mesoporous iron oxide (hematite) using pomegranate peels through a low-cost and massive product method was investigated. The mass of pomegranate peels was varied to control the morphology of the produced hematite (Fe2O3). The structures textures and optical properties of the products were investigated by FTIR XRD FE-SEM and UV–Vis spectroscopy. Three different Fe2O3 morphologies were obtained; Fe2O3(I) nanorod like shape Fe2O3(II) nanoparticles and Fe2O3(III) nanoporous structured layer. The bandgap values for Fe2O3 (I) (II) and (III) were 2.71 2.95 and 2.29 eV respectively. The newly hematite samples were used as promising photoelectrodes supported on graphite substrate for the photoelectrochemical (PEC) water splitting toward the efficient production of solar hydrogen. The number of generated hydrogen moles was calculated per active area to be 50 molh−1 cm−2 for electrode III which decreased to 15.3molh−1 cm−2 for electrode II. The effects of temperature (30–70 ◦C) on the PEC behavior of the three electrodes were addressed. Different thermodynamic parameters were calculated for the three electrodes which showed activation energies of 13.4 16.8 and 15.2 kJmol−1 respectively. The electrode stability was addressed as a function of the number of runs and exposure time in addition to electrochemical impedance study. Finally the conversion efficiency of the incident photon to-current(IPCE) was estimated under the monochromatic illumination. The optimum value was ∼11% @ 390nm for Fe2O3(III) electrode
Calculation and Analysis of Efficiencies and Annual Performances of Power-to-Gas Systems
Mar 2017
Publication
This paper describes a generic and systematic method to calculate the efficiency and the annual performance for Power-to-Gas (PtG) systems. This approach gives the basis to analytically compare different PtG systems using different technologies under different boundary conditions. To have a comparable basis for efficiency calculations a structured break down of the PtG system is done. Until now there has not been a universal approach for efficiency calculations. This has resulted in a wide variety of efficiency calculations used in feasibility studies and for business-case calculations. For this the PtG system is divided in two sub-systems: the electrolysis and the methanation. Each of the two sub-systems consists of several subsystem boundary levels. Staring from the main unit i.e. the electrolysis stack and/or methanation reactor further units that are required to operate complete PtG system are considered with their respective subsystem boundary conditions. The paper provides formulas how the efficiency of each level can be calculated and how efficiency deviations can be integrated which are caused by the extended energy flow calculations to and from energy users and thermal losses. By this a sensitivity analysis of the sub-systems can be gained and comprehensive goal functions for optimizations can be defined. In a second step the annual performance of the system is calculated as the ratio of useable output and energetic input over one year. The input is the integral of the annual need of electrical and thermal energy of a PtG system depending on the different operation states of the plant. The output is the higher heating value of the produced gas and – if applicable – heat flows that are used externally. The annual performance not only evaluates the steady-state operating efficiency under full load but also other states of the system such as cold standby or service intervals. It is shown that for a full system operation assessment and further system concept development the annual performance is of much higher importance than the steady-state system efficiency which is usually referred to. In a final step load profiles are defined and the annual performance is calculated for a specific system configuration. Using this example different operation strategies are compared.
Ecological and Economic Evaluation of Hydrogen Production by Different Water Electrolysis Technologies
Jul 2020
Publication
The economic and ecological production of green hydrogen by water electrolysis is one of the major challenges within Carbon2Chem and other power-to-X projects. This paper presents an evaluation of the different water electrolysis technologies with respect to their specific energy demand carbon footprint and the forecast production costs in 2030. From a current perspective alkaline water electrolysis is evaluated as the most favorable technology for the cost-effective production of low-carbon hydrogen with fluctuating renewables.
Techno-economic Assessment of Electrolytic Hydrogen in China Considering Wind-solar-load Characteristic
Jan 2023
Publication
Hydrogen production by electrolysis is considered an essential means of consuming renewable energy in the future. However the current assessment of the potential of renewable energy electrolysis for hydrogen production is relatively simple and the perspective is not comprehensive. Here we established a Combined Wind and Solar Electrolytic Hydrogen system considering the influence of regional wind-solar-load characteristics and transmission costs to evaluate the hydrogen production potential of 31 provincial-level regions in China in 2050. The results show that in 2050 the levelized cost of hydrogen (LCOH) in China’s provincial regions will still be higher than 10 ¥/kg which is not cost-competitive compared to the current hydrogen production from fossil fuels. It is more cost-effective to deploy wind turbines than photovoltaic in areas with similar wind and solar resources or rich in wind resources. Wind-solar differences impact LCOH equipment capacity configuration and transmission cost composition while load fluctuation significantly impacts LCOH and electricity storage configuration. In addition the sensitivity analysis of 11 technical and economic parameters showed differences in the response performance of LCOH changes to different parameters and the electrolyzer conversion efficiency had the most severe impact. The analysis of subsidy policy shows that for most regions (except Chongqing and Xizang) subsidizing the unit investment cost of wind turbines can minimize LCOH. Nevertheless from the perspective of comprehensive subsidy effect subsidy cost and hydrogen energy development it is more cost-effective to take subsidies for electrolysis equipment with the popularization of hydrogen
Techno-economic Viability of Islanded Green Ammonia as a Carbon-free Energy Vector and as a Substitute for Conventional Production
Jul 2020
Publication
Decarbonising ammonia production is an environmental imperative given that it independently accounts for 1.8% of global carbon dioxide emissions and supports the feeding of over 48% of the global population. The recent decline of production costs and its potential as an energy vector warrant investigation of whether green ammonia production is commercially competitive. Considering 534 locations in 70 countries and designing and operating the islanded production process to minimise the levelised cost of ammonia (LCOA) at each we show the range of achievable LCOA the cost of process flexibility the components of LCOA and therein the scope of LCOA reduction achievable at present and in 2030. These results are benchmarked against ammonia spot prices cost per GJ of refined fuels and the LCOE of alternative energy storage methods. Currently a LCOA of $473 t1 is achievable at the best locations the required process flexibility increases the achievable LCOA by 56%; the electrolyser CAPEX and operation are the most significant costs. By 2030 $310 t1 is predicted to be achievable with multiple locations below $350 t1 . At $25.4 GJ11 ) that do not have the benefit of being carbon-free.
Recent Advances in Alkaline Exchange Membrane Water Electrolysis and Electrode Manufacturing
Oct 2021
Publication
Water electrolysis to obtain hydrogen in combination with intermittent renewable energy resources is an emerging sustainable alternative to fossil fuels. Among the available electrolyzer technologies anion exchange membrane water electrolysis (AEMWE) has been paid much attention because of its advantageous behavior compared to other more traditional approaches such as solid oxide electrolyzer cells and alkaline or proton exchange membrane water electrolyzers. Recently very promising results have been obtained in the AEMWE technology. This review paper is focused on recent advances in membrane electrode assembly components paying particular attention to the preparation methods for catalyst coated on gas diffusion layers which has not been previously reported in the literature for this type of electrolyzers. The most successful methodologies utilized for the preparation of catalysts including co-precipitation electrodeposition sol–gel hydrothermal chemical vapor deposition atomic layer deposition ion beam sputtering and magnetron sputtering deposition techniques have been detailed. Besides a description of these procedures in this review we also present a critical appraisal of the efficiency of the water electrolysis carried out with cells fitted with electrodes prepared with these procedures. Based on this analysis a critical comparison of cell performance is carried out and future prospects and expected developments of the AEMWE are discussed.
Development and Mechanistic Studies of Ternary Nanocomposites for Hydrogen Production from Water Splitting to Yield Sustainable/Green Energy and Environmental Remediation
Mar 2022
Publication
Photocatalysts lead vitally to water purifications and decarbonise environment each by wastewater treatment and hydrogen (H2 ) production as a renewable energy source from waterphotolysis. This work deals with the photocatalytic degradation of ciprofloxacin (CIP) and H2 production by novel silver-nanoparticle (AgNPs) based ternary-nanocomposites of thiolated reducegraphene oxide graphitic carbon nitride (AgNPs-S-rGO2%@g-C3N4 ) material. Herein the optimised balanced ratio of thiolated reduce-graphene oxide in prepared ternary-nanocomposites played matchlessly to enhance activity by increasing the charge carriers’ movements via slowing down charge-recombination ratios. Reduced graphene oxide (rGO) >2 wt.% or < 10 nm. Therefore AgNPs-S-rGO2%@g-C3N4 has 3772.5 µmolg−1 h −1 H2 production which is 6.43-fold higher than g-C3N4 having cyclic stability of 96% even after four consecutive cycles. The proposed mechanism for AgNPs-S-rGO2%@g-C3N4 revealed that the photo-excited electrons in the conduction-band of g-C3N4 react with the adhered water moieties to generate H2 .
The Hydrogen Color Spectrum: Techno-Economic Analysis of the Available Technologies for Hydrogen Production
Feb 2023
Publication
Hydrogen has become the most promising energy carrier for the future. The spotlight is now on green hydrogen produced with water electrolysis powered exclusively by renewable energy sources. However several other technologies and sources are available or under development to satisfy the current and future hydrogen demand. In fact hydrogen production involves different resources and energy loads depending on the production method used. Therefore the industry has tried to set a classification code for this energy carrier. This is done by using colors that reflect the hydrogen production method the resources consumed to produce the required energy and the number of emissions generated during the process. Depending on the reviewed literature some colors have slightly different definitions thus making the classifications imprecise. Therefore this techno-economic analysis clarifies the meaning of each hydrogen color by systematically reviewing their production methods consumed energy sources and generated emissions. Then an economic assessment compares the costs of the various hydrogen colors and examines the most feasible ones and their potential evolution. The scientific community and industry’s clear understanding of the advantages and drawbacks of each element of the hydrogen color spectrum is an essential step toward reaching a sustainable hydrogen economy
Economics of Renewable Hydrogen Production Using Wind and Solar Energy: A Case Study for Queensland, Australia
Dec 2023
Publication
This study presents a technoeconomic analysis of renewables-based hydrogen production in Queensland Australia under Optimistic Reference and Pessimistic scenarios to address uncertainty in cost predictions. The goal of the work was to ascertain if the target fam-gate cost of AUD 3/kg (approx. USD 2/kg) could be reached. Economies of scale and the learning rate concept were factored into the economic model to account for the effect of scale-up and cost reductions as electrolyser manufacturing capacity grows. The model assumes that small-scale to large-scale wind turbine (WT)-based and photovoltaic (PV)-based power generation plants are directly coupled with an electrolyser array and utilises hourly generation data for the Gladstone hydrogen-hub region. Employing first a commonly used simplified approach the electrolyser array was sized based on the maximum hourly power available for hydrogen production. The initial results indicated that scale-up is very beneficial: the levelised cost of green hydrogen (LCOH) could decrease by 49% from $6.1/kg to $3.1/kg when scaling PV-based plant from 10 MW to 1 GW and for WT-based plant by 36% from $5.8/kg to $3.7/kg. Then impacts on the LCOH of incorporating curtailment of ineffective peak power and electrolyser overload capacity were investigated and shown to be significant. Also significant was the beneficial effect of recognising that electrolyser efficiency depends on input power. The latter two factors have mostly been overlooked in the literature. Incorporating in the model the influence on the LCOH of real-world electrolyser operational characteristics overcomes a shortcoming of the simplified sizing method namely that a large portion of electrolyser capacity is under-utilised leading to unnecessarily high values of the LCOH. It was found that AUD 3/kg is achievable if the electrolyser array is properly sized which should help to incentivise large-scale renewable hydrogen projects in Australia and elsewhere.
Flexible Power and Biomass-To-Methanol Plants With Different Gasification Technologies
Jan 2022
Publication
The competitiveness of biofuels may be increased by integrating biomass gasification plants with electrolysis units which generate hydrogen to be combined with carbon-rich syngas. This option allows increasing the yield of the final product by retaining a higher amount of biogenic carbon and improving the resilience of the energy sector by favoring electric grid services and sector coupling. This article illustrates a techno-economic comparative analysis of three flexible power and biomass to methanol plants based on different gasification technologies: direct gasification indirect gasification and sorptionenhanced gasification. The design and operational criteria of each plant are conceived to operate both without green hydrogen addition (baseline mode) and with hydrogen addition (enhanced mode) following an intermittent use of the electrolysis system which is turned on when the electricity price allows an economically viable hydrogen production. The methanol production plants include a gasification section syngas cleaning conditioning and compression section methanol synthesis and purification and heat recovery steam cycle to be flexibly operated. Due to the high oxygen demand in the gasifier the direct gasification-based plant obtains a great advantage to be operated between a minimum load to satisfy the oxygen demand at high electricity prices and a maximum load to maximize methanol production at low electricity prices. This allows avoiding large oxygen storages with significant benefits for Capex and safety issues. The analysis reports specific fixed-capital investments between 1823 and 2048 €/kW of methanol output in the enhanced operation and LCOFs between 29.7 and 31.7 €/GJLHV. Economic advantages may be derived from a decrease in the electrolysis capital investment especially for the direct gasification-based plants which employ the greatest sized electrolyzer. Methanol breakeven selling prices range between 545 and 582 €/t with the 2019 reference Denmark electricity price curve and between 484 and 535 €/t with an assumed modified electricity price curve of a future energy mix with increased penetration of intermittent renewables.
Integration of Renewable Hydrogen Production in Steelworks Off-Gases for the Synthesis of Methanol and Methane
May 2021
Publication
The steel industry is among the highest carbon-emitting industrial sectors. Since the steel production process is already exhaustively optimized alternative routes are sought in order to increase carbon efficiency and reduce these emissions. During steel production three main carbon-containing off-gases are generated: blast furnace gas coke oven gas and basic oxygen furnace gas. In the present work the addition of renewable hydrogen by electrolysis to those steelworks off-gases is studied for the production of methane and methanol. Different case scenarios are investigated using AspenPlusTM flowsheet simulations which differ on the end-product the feedstock flowrates and on the production of power. Each case study is evaluated in terms of hydrogen and electrolysis requirements carbon conversion hydrogen consumption and product yields. The findings of this study showed that the electrolysis requirements surpass the energy content of the steelwork’s feedstock. However for the methanol synthesis cases substantial improvements can be achieved if recycling a significant amount of the residual hydrogen.
Sustainable Hydrogen Production from Seawater Electrolysis: Through Fundamental Electrochemical Principles to the Most Recent Development
Nov 2022
Publication
Among the many potential future energy sources hydrogen stands out as particularly promising. Because it is a green and renewable chemical process water electrolysis has earned much interest among the different hydrogen production techniques. Seawater is the most abundant source of water and the ideal and cheapest electrolyte. The first part of this review includes the description of the general theoretical concepts: chemical physical and electrochemical that stands on the basis of water electrolysis. Due to the rapid development of new electrode materials and cell technology research has focused on specific seawater electrolysis parameters: the cathodic evolution of hydrogen; the concurrent anodic evolution of oxygen and chlorine; specific seawater catalyst electrodes; and analytical methods to describe their catalytic activity and seawater electrolyzer efficiency. Once the specific objectives of seawater electrolysis have been established through the design and energy performance of the electrolyzer the study further describes the newest challenges that an accessible facility for the electrochemical production of hydrogen as fuel from seawater must respond to for sustainable development: capitalizing on known and emerging technologies; protecting the environment; utilizing green renewable energies as sources of electricity; and above all economic efficiency as a whole.
Design and Analysis of a New Renewable-Nuclear Hybrid Energy System for Production of Hydrogen, Fresh Water and Power
Nov 2021
Publication
This paper investigates an integrated system where solar energy system (with 75MWp bifacial PV arrays) and nuclear power plant (with 2×10MWt HTR-10 type pebble bed reactors) are hybridized and integrated with a 72MWe capacity high-temperature solid oxide electrolysis (SOE) unit to produce hydrogen fresh water and electrical power. Bifacial PV plant is integrated to system for supplying electricity with a low LCOE and zero-carbon system. A Rankine cycle is integrated to generate power from the steam that generated from nuclear heat. According to the available irradiance; the steam is diverted between steam turbine and high-temperature electrolyzer for hydrogen and power generation. Multi-effect desalination unit is integrated to exploit the excess heat to generate fresh water. A system performance assessment is carried out by energy and exergy efficiencies thermodynamically. The bifacial PV plant is analyzed in six selected latitudes in order to assess the feasibility and applicability of the system. Numerous time-dependent analyses are carried out to study the effects of varying inputs such as solar radiation intensity. For 20MWt nuclear 75MWp solar capacity; hydrogen productions are found to be between 0.036 and 0.562kg/s. Among the Northern Hemisphere latitudes the peak daily hydrogen production rate is expected to reach 25.9 tons of hydrogen per day for the 75 °N case mostly with the influence of low temperature and high albedo. The pitch distance change is increased the hydrogen production rate by 28% between 3 m and 7 m tracker spacing. The overall system energy efficiency is obtained between 21.8% and 24.2% where the overall system exergy efficiency is found between 18.6% and 21.1% under dynamic conditions for the 45°N latitude case.
Economic Performance Evaluation of Flexible Centralised and Decentralised Blue Hydrogen Production Systems Design Under Uncertainty
Sep 2023
Publication
Blue hydrogen is viewed as an important energy vector in a decarbonised global economy but its large-scale and capital-intensive production displays economic performance vulnerabities in the face of increased market and regulatory uncertainty. This study analyses flexible (modular) blue hydrogen production plant designs and evaluates their effectiveness to enhance economic performance under uncertainty. The novelty of this work lies in the development of a comprehensive techno-economic evaluation framework that considers flexible centralised and decentralised blue hydrogen plant design alternatives in the presence of irreducible uncertainty whilst explicitly considering the time value of money economies of scale and learning effects. A case study of centralised and decentralised blue hydrogen production for the transport sector in the San Francisco area is developed to highlight the underlying value of flexibility. The proposed methodological framework considers various blue hydrogen plant designs (fixed phased and flexible) and compares them using relevant economic indicators (net present value (NPV) capex value-at-risk/gain etc.) through a detailed Monte Carlo simulation framework. Results indicate that flexible centralised hydrogen production yields greater economic value than alternative designs despite the associated cost-premium of modularity. It is also shown that the value of flexibility increases under greater uncertainty higher learning rates and weaker economies of scale. Moreover sensitivity analysis reveals that flexible design remains the preferred investment option over a wide range of market and regulatory conditions except for high initial hydrogen demand. Finally this study demonstrates that major regulatory and market uncertainties surrounding blue hydrogen production can be effectively managed through the application of flexible engineering system design that protects the investment from major downside risks whilst allowing access to favourable upside opportunities.
Green Hydrogen Production and Liquefaction Using Offshore Wind Power, Liquid Air, and LNG Cold Energy
Sep 2023
Publication
Coastal regions have abundant off-shore wind energy resources and surrounding areas have large-scale liquefied natural gas (LNG) receiving stations. From the engineering perspectives there are limitations in unstable off-shore wind energy and fluctuating LNG loads. This article offers a new energy scheme to combine these 2 energy units which uses surplus wind energy to produce hydrogen and use LNG cold energy to liquefy and store hydrogen. In addition in order to improve the efficiency of utilizing LNG cold energy and reduce electricity consumption for liquid hydrogen (LH2) production at coastal regions this article introduces the liquid air energy storage (LAES) technology as the intermediate stage which can stably store the cold energy from LNG gasification. A new scheme for LNG-LAES-LH2 hybrid LH2 production is built. The case study is based on a real LNG receiving station at Hainan province China and this article presents the design of hydrogen production/liquefaction process and carries out the optimizations at key nodes and proves the feasibility using specific energy consumption and exergy analysis. In a 100 MW system the liquid air storage round-trip efficiency is 71.0% and the specific energy consumption is 0.189 kWh/kg and the liquid hydrogen specific energy consumption is 7.87 kWh/kg and the exergy efficiency is 46.44%. Meanwhile the corresponding techno-economic model is built and for a LNGLAES-LH2 system with LH2 daily production 140.4 tons the shortest dynamic payback period is 9.56 years. Overall this novel hybrid energy scheme can produce green hydrogen using a more efficient and economical method and also can make full use of surplus off-shore wind energy and coastal LNG cold energy.
A Numerical Study on Turquoise Hydrogen Production by Catalytic Decomposition of Methane
Feb 2023
Publication
Catalytic decomposition of methane (CDM) is a novel technology for turquoise hydrogen production with solid carbon as the by-product instead of CO2. A computational fluid dynamics model was developed to simulate the CDM process in a 3D fixed bed reactor accounting for the impact of carbon deposition on catalytic activity. The model was validated with experimental data and demonstrated its capability to predict hydrogen concentration and catalyst deactivation time under varying operating temperatures and methane flow rates. The catalyst lifespan was characterized by the maximum carbon yield (i.e. gC/gcat) which is a crucial indicator for determining the cost of hydrogen generation. Parametric studies were performed to analyse the effect of inlet gas composition and operating pressure on CDM performance. Various CH4/H2 ratios were simulated to improve the methane conversion efficiency generating a higher amount of hydrogen while increasing the maximum carbon yield up to 49.5 gC/gcat. Additionally higher operating pressure resulted in higher methane decomposition rates which reflects the nature of the chemical kinetics.
Exergy Analysis in Intensification of Sorption-enhanced Steam Methane Reforming for Clean Hydrogen Production: Comparative Study and Efficiency Optimisation
Feb 2024
Publication
Hydrogen has a key role to play in decarbonising industry and other sectors of society. It is important to develop low-carbon hydrogen production technologies that are cost-effective and energy-efficient. Sorption-enhanced steam methane reforming (SE-SMR) is a developing low-carbon (blue) hydrogen production process which enables combined hydrogen production and carbon capture. Despite a number of key benefits the process is yet to be fully realised in terms of efficiency. In this work a sorption-enhanced steam methane reforming process has been intensified via exergy analysis. Assessing the exergy efficiency of these processes is key to ensuring the effective deployment of low-carbon hydrogen production technologies. An exergy analysis was performed on an SE-SMR process and was then subsequently used to incorporate process improvements developing a process that has theoretically an extremely high CO2 capture rate of nearly 100 % whilst simultaneously demonstrating a high exergy efficiency (77.58 %) showcasing the potential of blue hydrogen as an effective tool to ensure decarbonisation in an energy-efficient manner.
Techno-Economic Analysis of Hydrogen Production from Swine Manure Biogas via Steam Reforming in Pilot-Scale Installation
Sep 2023
Publication
The main purpose of this paper is the techno-economic analysis of hydrogen production from biogas via steam reforming in a pilot plant. Process flow modeling based on mass and energy balance is used to estimate the total equipment purchase and operating costs of hydrogen production. The pilot plant installation produced 250.67 kg/h hydrogen from 1260 kg/h biomethane obtained after purification of 4208 m3/h biogas using a heat and mass integration process. Despite the high investment cost the plant shows a great potential for biomethane reduction and conversion to hydrogen an attractive economic path with ecological possibilities. The conversion of waste into hydrogen is a possibility of increasing importance in the global energy economy. In the future such a plant will be expanded with a CO2 reduction module to increase economic efficiency and further reduce greenhouse gases in an economically viable manner.
Research on Fast Frequency Response Control Strategy of Hydrogen Production Systems
Mar 2024
Publication
With the large-scale integration of intermittent renewable energy generation presented by wind and photovoltaic power the security and stability of power system operations have been challenged. Therefore this article proposes a control strategy of a hydrogen production system based on renewable energy power generation to enable the fast frequency response of a grid. Firstly based on the idea of virtual synchronous control a fast frequency response control transformation strategy for the grid-connected interface of hydrogen production systems for renewable energy power generation is proposed to provide active power support when the grid frequency is disturbed. Secondly based on the influence of VSG’s inertia and damping coefficient on the dynamic characteristics of the system a VSG adaptive control model based on particle swarm optimization is designed. Finally based on the Matlab/Simulink platform a grid-connected simulation model of hydrogen production systems for renewable energy power generation is established. The results show that the interface-transformed electrolytic hydrogen production device can actively respond to the frequency disturbances of the power system and participate in primary frequency control providing active support for the frequency stability of the power system under high-percentage renewable energy generation integration. Moreover the system with parameter optimization has better fast frequency response control characteristics.
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