Production & Supply Chain
A Review on Recent Progress in the Integrated Green Hydrogen Production Processes
Feb 2022
Publication
The thermochemical water‐splitting method is a promising technology for efficiently con verting renewable thermal energy sources into green hydrogen. This technique is primarily based on recirculating an active material capable of experiencing multiple reduction‐oxidation (redox) steps through an integrated cycle to convert water into separate streams of hydrogen and oxygen. The thermochemical cycles are divided into two main categories according to their operating temperatures namely low‐temperature cycles (<1100 °C) and high‐temperature cycles (<1100 °C). The copper chlorine cycle offers relatively higher efficiency and lower costs for hydrogen production among the low‐temperature processes. In contrast the zinc oxide and ferrite cycles show great potential for developing large‐scale high‐temperature cycles. Although several challenges such as energy storage capacity durability cost‐effectiveness etc. should be addressed before scaling up these technologies into commercial plants for hydrogen production. This review critically examines various aspects of the most promising thermochemical water‐splitting cycles with a particular focus on their capabilities to produce green hydrogen with high performance redox pairs stability and the technology maturity and readiness for commercial use.
A Review on Numerical Simulation of Hydrogen Production from Ammonia Decomposition
Jan 2023
Publication
Ammonia (NH3 ) is regarded as a promising medium of hydrogen storage due to its large hydrogen storage density decent performance on safety and moderate storage conditions. On the user side NH3 is generally required to decompose into hydrogen for utilization in fuel cells and therefore it is vital for the NH3 -based hydrogen storage technology development to study NH3 decomposition processes and improve the decomposition efficiency. Numerical simulation has become a powerful tool for analyzing the NH3 decomposition processes since it can provide a revealing insight into the heat and mass transfer phenomena and substantial guidance on further improving the decomposition efficiency. This paper reviews the numerical simulations of NH3 decomposition in various application scenarios including NH3 decomposition in microreactors coupled combustion chemical reactors solid oxide fuel cells and membrane reactors. The models of NH3 decomposition reactions in various scenarios and the heat and mass transport in the reactor are elaborated. The effects of reactor structure and operating conditions on the performance of NH3 decomposition reactor are analyzed. It can be found that NH3 decomposition in microchannel reactors is not limited by heat and mass transfer and NH3 conversion can be improved by using membrane reactors under the same conditions. Finally research prospects and opportunities are proposed in terms of model development and reactor performance improvement for NH3 decomposition.
Exergy and Exergoeconomic Analysis for the Proton Exchange Membrane Water Electrolysis under Various Operating Conditions and Design Parameters
Nov 2022
Publication
Integrating the exergy and economic analyses of water electrolyzers is the pivotal way to comprehend the interplay of system costs and improve system performance. For this a 3D numerical model based on COMSOL Multiphysics Software (version 5.6 COMSOL Stockholm Sweden) is integrated with the exergy and exergoeconomic analysis to evaluate the exergoeconomic performance of the proton exchange membrane water electrolysis (PEMWE) under different operating conditions (operating temperature cathode pressure current density) and design parameter (membrane thickness). Further the gas crossover phenomenon is investigated to estimate the impact of gas leakage on analysis reliability under various conditions and criteria. The results reveal that increasing the operating temperature or decreasing the membrane thickness improves both the efficiency and cost of hydrogen exergy while increasing the gas leakage through the membrane. Likewise raising the current density and the cathode pressure lowers the hydrogen exergy cost and improves the economic performance. The increase in exergy destroyed and hydrogen exergy cost as well as the decline in second law efficiency due to the gas crossover are more noticeable at higher pressures. As the cathode pressure rises from 1 to 30 bar at a current density of 10000 A/m2 the increase in exergy destroyed and hydrogen exergy cost as well as the decline in second law efficiency are increased by 37.6 kJ/mol 4.49 USD/GJ and 7.1% respectively. The cheapest green electricity source which is achieved using onshore wind energy and hydropower reduces hydrogen production costs and enhances economic efficiency. The growth in the hydrogen exergy cost is by about 4.23 USD/GJ for a 0.01 USD/kWh increase in electricity price at the current density of 20000 A/m2. All findings would be expected to be quite useful for researchers engaged in the design development and optimization of PEMWE.
Life Cycle Performance of Hydrogen Production via Agro-Industrial Residue Gasification—A Small Scale Power Plant Study
Mar 2018
Publication
This study evaluates the environmental profile of a real biomass-based hydrogen production small-scale (1 MWth) system composed of catalytic candle indirectly heated steam gasifier coupled with zinc oxide (ZnO) guard bed water gas shift (WGS) and pressure swing absorber (PSA) reactors. Environmental performance from cradle-to-gate was investigated by life cycle assessment (LCA) methodology. Biomass production shows high influence over all impact categories. In the syngas production process the main impacts observed are global warming potential (GWP) and acidification potential (AP). Flue gas emission from gasifier burner has the largest proportion of total GWP. The residual off gas use in internal combustion engine (ICE) leads to important environmental savings for all categories. Hydrogen renewability score is computed as 90% due to over 100% decline in non-renewable energy demand. Sensitivity analysis shows that increase in hydrogen production efficiency does not necessarily result in decrease in environmental impacts. In addition economic allocation of environmental charges increases all impact categories especially AP and photochemical oxidation (POFP).
Carbon-free Green Hydrogen Production Process with Induction Heating-based Ammonia Decomposition Reactor
Dec 2022
Publication
This study presents an induction heating-based reactor for ammonia decomposition and to achieve a 150 Nm3 /h carbon-free green hydrogen production process. The developed metallic monolith reactor acts by increasing the reactor temperature through an electromagnetic induction method using renewable-based electricity. As a result hydrogen is produced without the generation of air pollutants such as CO2 which are formed via the conventional production pathway. Furthermore techno-economic analysis was conducted based on exergy and economic analysis to evaluate the feasibility of the developed process. Experimentally the proposed reactor showed an ammonia conversion of 90.0 % at 600 ℃ and 7 barg. Exergy analysis indicated that the total unused exergy accounted for 45.79 % of the total exergy input giving an exergy efficiency of 54.21 % for the overall process. Furthermore the CAPEX and OPEX values are calculated as 1599567 USD and 644719 USD/y respectively; therefore the levelized cost of hydrogen (LCOH) was calculated to be 6.98 USD/kgH2. This study also demonstrated that the LCOH varies with the ammonia feed price and the process capacity and so it would be expected to decrease from 6.98 to 5.33 USD/kgH2 as the hydrogen production capacity is increased from 150 to 500 Nm3 / h. Overall our results confirm the feasibility of carbon-free green hydrogen production on on-site hydrogen refueling stations and they will be expected to advance the development of an environmental hydrogen economy.
Progress and Prospects of Hydrogen Production: Opportunities and challenges
Jan 2021
Publication
This study presents an overview of the current status of hydrogen production in relation to the global requirement for energy and resources. Subsequently it symmetrically outlines the advantages and disadvantages of various production routes including fossil fuel/biomass conversion water electrolysis microbial fermentation and photocatalysis (PC) in terms of their technologies economy energy consumption and costs. Considering the characteristics of hydrogen energy and the current infrastructure issues it highlights that onsite production is indispensable and convenient for some special occasions. Finally it briefly summarizes the current industrialization situation and presents future development and research directions such as theoretical research strengthening renewable raw material development process coupling and sustainable energy use.
Implementation of Transition Metal Phosphides as Pt-Free Catalysts for PEM Water Electrolysis
Mar 2022
Publication
Proton Exchange Membrane (PEM) water electrolysis (WE) produces H2 with a high degree of purity requiring only water and energy. If the energy is provided from renewable energy sources it releases “Green H2” a CO2 -free H2 . PEMWE uses expensive and rare noble metal catalysts which hinder their use at a large industrial scale. In this work the electrocatalytic properties of Transition Metal Phosphides (TMP) catalysts supported on Carbon Black (CB) for Hydrogen Evolution Reaction (HER) were investigated as an alternative to Platinum Group Metals. The physico-chemical properties and catalytic performance of the synthesized catalysts were characterized. In the ex situ experiments the 25% FeP/CB 50% FeP/CB and 50% CoP/CB with overpotentials of −156.0 −165.9 and −158.5 mV for a current density of 100 mA cm−2 showed the best catalytic properties thereby progressing to the PEMWE tests. In those tests the 50% FeP/CB required an overpotential of 252 mV for a current density of 10 mA cm−2 quite close to the 220 mV of the Pt catalyst. This work provides a proper approach to the synthesis and characterization of TMP supported on carbon materials for the HER paving the way for further research in order to replace the currently used PGM in PEMWE.
Bench-Scale Steam Reforming of Methane for Hydrogen Production
Jul 2019
Publication
The effects of reaction parameters including reaction temperature and space velocity on hydrogen production via steam reforming of methane (SRM) were investigated using lab- and bench-scale reactors to identify critical factors for the design of large-scale processes. Based on thermodynamic and kinetic data obtained using the lab-scale reactor a series of SRM reactions were performed using a pelletized catalyst in the bench-scale reactor with a hydrogen production capacity of 10 L/min. Various temperature profiles were tested for the bench-scale reactor which was surrounded by three successive cylindrical furnaces to simulate the actual SRM conditions. The temperature at the reactor bottom was crucial for determining the methane conversion and hydrogen production rates when a sufficiently high reaction temperature was maintained (>800 ◦C) to reach thermodynamic equilibrium at the gas-hourly space velocity of 2.0 L CH4/(h·gcat). However if the temperature of one or more of the furnaces decreased below 700 ◦C the reaction was not equilibrated at the given space velocity. The effectiveness factor (0.143) of the pelletized catalyst was calculated based on the deviation of methane conversion between the lab- and bench-scale reactions at various space velocities. Finally an idling procedure was proposed so that catalytic activity was not affected by discontinuous operation.
Hydrogen Generation from Wood Chip and Biochar by Combined Continuous Pyrolysis and Hydrothermal Gasification
Jun 2021
Publication
Hydrothermal gasification (HTG) experiments were carried out to extract hydrogen from biomass. Although extensive research has been conducted on hydrogen production with HTG limited research exists on the use of biochar as a raw material. In this study woodland residues (wood chip) and biochar from wood-chip pyrolysis were used in HTG treatment to generate hydrogen. This research investigated the effect of temperature (300–425 °C) and biomass/water (0.5–10) ratio on gas composition. A higher temperature promoted hydrogen production because the water–gas shift reaction and steam-reforming reaction were promoted with an increase in temperature. The methane concentration was related positively to temperature because of the methanation and hydrogenation reactions. A lower biomass/water ratio promoted hydrogen production but suppressed carbon-monoxide production. Most reactions that produce hydrogen consume water but water also affects the water–gas shift reaction balance which decreases the carbon-monoxide concentration. By focusing on the practical application of HTG we attempted biochar treatment by pyrolysis (temperature of heating part: 700 °C) and syngas was obtained from hydrothermal treatment above 425 °C.
Options for Producing Low-carbon Hydrogen at Scale
Feb 2018
Publication
Low-carbon hydrogen has the potential to play a significant role in tackling climate change and poor air quality. This policy briefing considers how hydrogen could be produced at a useful scale to power vehicles heat homes and supply industrial processes.
Four groups of hydrogen production technologies are examined:
Thermochemical Routes to Hydrogen
These methods typically use heat and fossil fuels. Steam methane reforming is the dominant commercial technology and currently produces hydrogen on a large scale but is not currently low carbon. Carbon capture is therefore essential with this process. Innovative technology developments may also help and research is underway. Alternative thermal methods of creating hydrogen indicate biomass gasification has potential. Other techniques at a low technology readiness level include separation of hydrogen from hydrocarbons using microwaves.
Electrolytic Routes to Hydrogen
Electrolytic hydrogen production also known as electrolysis splits water into hydrogen and oxygen using electricity in an electrolysis cell. Electrolysis produces pure hydrogen which is ideal for low temperature fuel cells for example in electric vehicles. Commercial electrolysers are on the market and have been in use for many years. Further technology developments will enable new generation electrolysers to be commercially competitive when used at scale with fluctuating renewable energy sources.
Biological Routes to Hydrogen
Biological routes usually involve the conversion of biomass to hydrogen and other valuable end products using microbial processes. Methods such as anaerobic digestion are feasible now at a laboratory and small pilot scale. This technology may prove to have additional or greater impact and value as route for the production of high value chemicals within a biorefinery concept.
Solar to Fuels Routes to Hydrogen
A number of experimental techniques have been reported the most developed of which is ‘solar to fuels’ - a suite of technologies that typically split water into hydrogen and oxygen using solar energy. These methods have close parallels with the process of photosynthesis and are often referred to as ‘artificial photosynthesis’ processes. The research is promising though views are divided on its ultimate utility. Competition for space will always limit the scale up of solar to fuels.
The briefing concludes that steam methane reforming and electrolysis are the most likely technologies to be deployed to produce low-carbon hydrogen at volume in the near to mid-term providing that the challenges of high levels of carbon capture (for steam methane reforming) and cost reduction and renewable energy sources (for electrolysis) can be overcome.
Four groups of hydrogen production technologies are examined:
Thermochemical Routes to Hydrogen
These methods typically use heat and fossil fuels. Steam methane reforming is the dominant commercial technology and currently produces hydrogen on a large scale but is not currently low carbon. Carbon capture is therefore essential with this process. Innovative technology developments may also help and research is underway. Alternative thermal methods of creating hydrogen indicate biomass gasification has potential. Other techniques at a low technology readiness level include separation of hydrogen from hydrocarbons using microwaves.
Electrolytic Routes to Hydrogen
Electrolytic hydrogen production also known as electrolysis splits water into hydrogen and oxygen using electricity in an electrolysis cell. Electrolysis produces pure hydrogen which is ideal for low temperature fuel cells for example in electric vehicles. Commercial electrolysers are on the market and have been in use for many years. Further technology developments will enable new generation electrolysers to be commercially competitive when used at scale with fluctuating renewable energy sources.
Biological Routes to Hydrogen
Biological routes usually involve the conversion of biomass to hydrogen and other valuable end products using microbial processes. Methods such as anaerobic digestion are feasible now at a laboratory and small pilot scale. This technology may prove to have additional or greater impact and value as route for the production of high value chemicals within a biorefinery concept.
Solar to Fuels Routes to Hydrogen
A number of experimental techniques have been reported the most developed of which is ‘solar to fuels’ - a suite of technologies that typically split water into hydrogen and oxygen using solar energy. These methods have close parallels with the process of photosynthesis and are often referred to as ‘artificial photosynthesis’ processes. The research is promising though views are divided on its ultimate utility. Competition for space will always limit the scale up of solar to fuels.
The briefing concludes that steam methane reforming and electrolysis are the most likely technologies to be deployed to produce low-carbon hydrogen at volume in the near to mid-term providing that the challenges of high levels of carbon capture (for steam methane reforming) and cost reduction and renewable energy sources (for electrolysis) can be overcome.
Outlook of Fermentative Hydrogen Production Techniques: An Overview of Dark, Photo and Integrated Dark-photo Fermentative Approach to Biomass
Jan 2019
Publication
Biomass can be a sustainable choice for bioenergy production worldwide. Biohydrogen production using fermentative conversion of biomass has gained great interest during the last decade. Besides being an efficient transportation fuel biohydrogen can also be also be a low-carbon source of heat and electricity. Microbes assisted conversion (bioconversion) can be take place either in presence or absence of light. This is called photofermentation or dark-fermentation respectively. This review provides an overview of approaches of fermentative hydrogen production. This includes: dark photo and integrated fermentative modes of hydrogen production; the molecular basis behind its production and diverse range of its applicability industrially. Mechanistic understanding of the metabolic pathways involved in biomass-based fermentative hydrogen production are also reviewed.
Research Requirements to Move the Bar Forward Using Aqueous Formate Salts as H2 Carriers for Energy Storage Applications
Nov 2020
Publication
In this perspective on hydrogen carriers we focus on the needs for the development of robust active catalysts for the release of H2 from aqueous formate solutions which are non-flammable non-toxic thermally stable and readily available at large scales at reasonable cost. Formate salts can be stockpiled in the solid state or dissolved in water for long term storage and transport using existing infrastructure. Furthermore formate salts are readily regenerated at moderate pressures using the same catalyst as for the H2 release. There have been several studies focused on increasing the activity of catalysts to release H2 at moderate temperatures i.e. < 80 °C below the operating temperature of a proton exchange membrane (PEM) fuel cell. One significant challenge to enable the use of aqueous formate salts as hydrogen carriers is the deactivation of the catalyst under operating conditions. In this work we provide a review of the most efficient heterogeneous catalysts that have been described in the literature their proposed modes of deactivation and the strategies reported to reactivate them. We discuss potential pathways that may lead to deactivation and strategies to mitigate it in a variety of H2 carrier applications. We also provide an example of a potential use case employing formate salts solutions using a fixed bed reactor for seasonal storage of energy for a microgrid application.
How Flexible Electricity Demand Stabilizes Wind and Solar Market Values: The Case of Hydrogen Electrolyzers
Nov 2021
Publication
Wind and solar energy are often expected to fall victim to their own success: the higher their share in electricity generation the more their revenue in electricity markets (their “market value”) declines. While market values may converge to zero in conventional power systems this study argues that “green” hydrogen production can effectively and permanently halt the decline by adding flexible electricity demand in low-price hours. To support this argument this article further develops the merit order model and uses price duration curves to include flexible hydrogen electrolysis and to derive an analytical formula for the minimum market value of renewables in the long-term market equilibrium. This hydrogen-induced minimum market value is quantified for a wide range of parameters using Monte Carlo simulations and complemented with results from a more detailed numerical electricity market model. It is shown that—due to flexible hydrogen production alone—market values across Europe will likely stabilize above €19 ± 9 MWh− 1 for solar energy and above €27 ± 8 MWh− 1 for wind energy in 2050 (annual mean estimate ± standard deviation). This is in the range of the projected levelized cost of renewables and other types of flexible electricity demand may further increase renewable market values. Market-based renewables may hence be within reach.
Onshore, Offshore or In-turbine Electrolysis? Techno-economic Overview of Alternative Integration Designs for Green Hydrogen Production into Offshore Wind Power Hubs
Aug 2021
Publication
Massive investments in offshore wind power generate significant challenges on how this electricity will be integrated into the incumbent energy systems. In this context green hydrogen produced by offshore wind emerges as a promising solution to remove barriers towards a carbon-free economy in Europe and beyond. Motivated by the recent developments in Denmark with the decision to construct the world’s first artificial Offshore Energy Hub this paper investigates how the lowest cost for green hydrogen can be achieved. A model proposing an integrated design of the hydrogen and offshore electric power infrastructure determining the levelised costs of both hydrogen and electricity is proposed. The economic feasibility of hydrogen production from 2 Offshore Wind Power Hubs is evaluated considering the combination of different electrolyser placements technologies and modes of operations. The results show that costs down to 2.4 €/kg can be achieved for green hydrogen production offshore competitive with the hydrogen costs currently produced by natural gas. Moreover a reduction of up to 13% of the cost of wind electricity is registered when an electrolyser is installed offshore shaving the peak loads.
Solar Fuel Processing: Comparative Mini-review on Research, Technology Development, and Scaling
Oct 2022
Publication
Solar energy provides an unprecedented potential as a renewable and sustainable energy resource and will substantially reshape our future energy economy. It is not only useful in producing electricity but also (hightemperature) heat and fuel both required for non-electrifiable energy services. Fuels are particularly valuable as they are energy dense and storable and they can also act as a feedstock for the chemical industry. Technical pathways for the processing of solar fuels include thermal pathways (e.g. solar thermochemistry) photo pathways (e.g. photoelectrochemistry) and combinations thereof. A review of theoretical limits indicates that all technical solar fuel processing pathways have the potential for competitive solar-to-fuel efficiencies (>10 %) but require very different operating conditions (e.g. temperature levels or oxygen partial pressures) making them complementary and highly versatile for process integration. Progress in photoelectrochemical devices and solar thermochemical reactors over the last 50 + years are summarized showing encouraging trends in terms of performance technological viability and scaling.
How Green is Blue Hydrogen?
Jul 2021
Publication
Hydrogen is often viewed as an important energy carrier in a future decarbonized world. Currently most hydrogen is produced by steam reforming of methane in natural gas (“gray hydrogen”) with high carbon dioxide emissions. Increasingly many propose using carbon capture and storage to reduce these emissions producing so-called “blue hydrogen” frequently promoted as low emissions. We undertake the first effort in a peer-reviewed paper to examine the lifecycle greenhouse gas emissions of blue hydrogen accounting for emissions of both carbon dioxide and unburned fugitive methane. Far from being low carbon greenhouse gas emissions from the production of blue hydrogen are quite high particularly due to the release of fugitive methane. For our default assumptions (3.5% emission rate of methane from natural gas and a 20-year global warming potential) total carbon dioxide equivalent emissions for blue hydrogen are only 9%-12% less than for gray hydrogen. While carbon dioxide emissions are lower fugitive methane emissions for blue hydrogen are higher than for gray hydrogen because of an increased use of natural gas to power the carbon capture. Perhaps surprisingly the greenhouse gas footprint of blue hydrogen is more than 20% greater than burning natural gas or coal for heat and some 60% greater than burning diesel oil for heat again with our default assumptions. In a sensitivity analysis in which the methane emission rate from natural gas is reduced to a low value of 1.54% greenhouse gas emissions from blue hydrogen are still greater than from simply burning natural gas and are only 18%-25% less than for gray hydrogen. Our analysis assumes that captured carbon dioxide can be stored indefinitely an optimistic and unproven assumption. Even if true though the use of blue hydrogen appears difficult to justify on climate ground
Introducing Power-to-H3: Combining Renewable Electricity with Heat, Water and Hydrogen Production and Storage in a Neighbourhood
Oct 2019
Publication
In the transition from fossil to renewable energy the energy system should become clean while remaining reliable and affordable. Because of the intermittent nature of both renewable energy production and energy demand an integrated system approach is required that includes energy conversion and storage. We propose a concept for a neighbourhood where locally produced renewable energy is partly converted and stored in the form of heat and hydrogen accompanied by rainwater collection storage purification and use (Power-to-H3). A model is developed to create an energy balance and perform a techno-economic analysis including an analysis of the avoided costs within the concept. The results show that a solar park of 8.7 MWp combined with rainwater collection and solar panels on roofs can supply 900 houses over the year with heat (20 TJ) via an underground heat storage system as well as with almost half of their water demand (36000m3) and 540 hydrogen electric vehicles can be supplied with hydrogen (90 tonnes). The production costs for both hydrogen (8.7 €/kg) and heat (26 €/GJ) are below the current end user selling price in the Netherlands (10 €/kg and 34 €/GJ) making the system affordable. When taking avoided costs into account the prices could decrease with 20–26% while at the same time avoiding 3600 tonnes of CO2 a year. These results make clear that it is possible to provide a neighbourhood with all these different utilities completely based on solar power and rainwater in a reliable affordable and clean way.
Oxygen Carriers for Chemical-looping Water Splitting to Hydrogen Production: A Critical Review
Oct 2021
Publication
Chemical looping water splitting (CLWS) process using metal oxides or perovskites as oxygen carriers (OCs) is capable of producing pure H2 in an efficient simple and flexible way. The OCs are first reduced by hydrocarbon fuels and then oxidized by steam in a cyclic way. After the condensation of the gaseous mixture of steam and H2 from the oxidation step pure H2 is obtained. In recent years great efforts for CLWS have been made to improve the redox activity and stability of OCs. In this paper the development of the OCs for hydrogen production from CLWS were discussed. Effects of supports and additives on the performances of OCs were compared based on redox reactions in CLWS. Fe-based OCs with CeO2 Al2O3 ZrO2 CuO MoO3 Rh etc. are very attractive for the CLWS process. Issues and challenges for the development of OCs were analyzed.
Life Cycle Assessment of Improved High Pressure Alkaline Electrolysis
Aug 2015
Publication
This paper investigates environmental impacts of high pressure alkaline water electrolysis systems. An advanced system with membranes on polymer basis is compared to a state-of-the-art system with asbestos membranes using a Life Cycle Assessment (LCA) approach. For the advanced system a new improved membrane technology has been investigated within the EU research project “ELYGRID”. Results indicate that most environmental impacts are caused by the electricity supply necessary for operation. During the construction phase cell stacks are the main contributor to environmental impacts. New improved membranes have relatively small contributions to impacts caused by cell construction within the advanced systems. As main outcome the systems comparison illustrates a better ecological performance of the new developed system
Site-Dependent Environmental Impacts of Industrial Hydrogen Production by Alkaline Water Electrolysis
Jun 2017
Publication
Industrial hydrogen production via alkaline water electrolysis (AEL) is a mature hydrogen production method. One argument in favor of AEL when supplied with renewable energy is its environmental superiority against conventional fossil-based hydrogen production. However today electricity from the national grid is widely utilized for industrial applications of AEL. Also the ban on asbestos membranes led to a change in performance patterns making a detailed assessment necessary. This study presents a comparative Life Cycle Assessment (LCA) using the GaBi software (version 6.115 thinkstep Leinfelden-Echterdingen Germany) revealing inventory data and environmental impacts for industrial hydrogen production by latest AELs (6 MW Zirfon membranes) in three different countries (Austria Germany and Spain) with corresponding grid mixes. The results confirm the dependence of most environmental effects from the operation phase and specifically the site-dependent electricity mix. Construction of system components and the replacement of cell stacks make a minor contribution. At present considering the three countries AEL can be operated in the most environmentally friendly fashion in Austria. Concerning the construction of AEL plants the materials nickel and polytetrafluoroethylene in particular used for cell manufacturing revealed significant contributions to the environmental burden.
Energy-Efficient Distributed Carbon Capture in Hydrogen Production from Natural Gas
Apr 2011
Publication
Lowering the energy penalty associated with CO2 capture is one of the key issues of Carbon Capture and Storage (CCS) technologies. The efficiency of carbon capture must be improved to reduce the energy penalty because capture stage is the most energy-consuming stage in the entire process of CCS. Energy-efficient distributed carbon capture in hydrogen production has been demonstrated with an advanced membrane reformer system. We have already developed and operated an advanced 40 Nm3 /h-class membrane reformer system and demonstrated its high hydrogen production efficiency of 81.4% (HHV) which is the world highest efficiency in terms of hydrogen production from natural gas. The system has another significant feature that the CO2 concentration in the reactor off-gas is as high as 70~90% and CO2 can be liquefied and separated easily with little energy loss. An apparatus for CO2 capture was combined to the membrane reformer system and over 90% of CO2 in the reactor off-gas was captured by cryogenic separation. The total energy efficiency of hydrogen production even with CO2 capture was still as high as 78.6% (HHV) which is 510% higher than the conventional reforming technologies. The total CO2 emission from hydrogen production was decreased by 50% with only a 3% energy loss. A sensitivity analysis was also carried out to evaluate the effects of the operating conditions of the system on hydrogen production efficiency and CO2 reduction rate.
Sensing Hydrogen Seeps in the Subsurface for Natural Hydrogen Exploration
Jun 2022
Publication
The recent detection of natural hydrogen seeps in sedimentary basin settings has triggered significant interest in the exploration of this promising resource. If large economical resources exist and can be extracted from the sub-surface this would provide an opportunity for natural hydrogen to contribute to the non-carbon-based energy mix. The detection and exploration of hydrogen gas in the sub-surface is a significant challenge that requires costly drilling sophisticated instrumentation and reliable analytical/sampling methods. Here we propose the application of a commercial-based sensor that can be used to detect and monitor low levels of hydrogen gas emissions from geological environments. The sensitivity selectivity (K > 1000) and stability (<1 ppm/day) of the sensor was evaluated under various conditions to determine its suitability for geological field monitoring. Calibration tests showed that the hydrogen readings from the sensor were within ±20% of the expected values. We propose that chemical sensing is a simple and feasible method for understanding natural hydrogen seeps that emanate from geological systems and formations. However we recommend using this sensor as part of a complete geological survey that incorporates an understanding of the geology along with complementary techniques that provide information on the rock properties.
Delivering Clean Growth: CCUS Cost Challenge Taskforce Report
Jul 2018
Publication
An independent report by the CCUS Cost Challenge Taskforce setting out the industry’s view on how best to progress carbon capture usage and storage (CCUS) in the UK in order to enable the UK to have the option of deploying CCUS at scale during the 2030s subject to costs coming down sufficiently.
Transient Reversible Solid Oxide Cell Reactor Operation – Experimentally Validated Modeling and Analysis
Oct 2018
Publication
A reversible solid oxide cell (rSOC) reactor can operate efficiently in both electrolysis mode and in fuel cell mode. The bidirectional operability enables rSOC reactors to play a central role as an efficient energy conversion system for energy storage and sector coupling for a renewable energy driven society. A combined system for electrolysis and fuel cell operation can result in complex system configurations that should be able to switch between the two modes as quickly as possible. This can lead to temperature profiles within the reactor that can potentially lead to the failure of the reactor and eventually the system. Hence the behavior of the reactor during the mode switch should be analyzed and optimal transition strategies should be taken into account during the process system design stage. In this paper a one dimensional transient reversible solid oxide cell model was built and experimentally validated using a commercially available reactor. A simple hydrogen based system model was built employing the validated reactor model to study reactor behavior during the mode switch. The simple design leads to a system efficiency of 49% in fuel cell operation and 87% in electrolysis operation where the electrolysis process is slightly endothermic. Three transient operation strategies were studied. It is shown that the voltage response to transient operation is very fast provided the reactant flows are changed equally fast. A possible solution to ensure a safe mode switch by controlling the reactant inlet temperatures is presented. By keeping the rate of change of reactant inlet temperatures five to ten times slower than the mode switch a safe transition can be ensured.
Everything About Hydrogen Podcast: Going "Green"
May 2021
Publication
Founded in 2007 and based in Denmark Green Hydrogen Systems designs and manufactures efficient standardized and modular electrolysers for the production of green hydrogen with renewable energy. Niels-Arne Baden has led the company to the upper echelons of the electrolysis sector and he now leads the company's strategy and and public-facing initiatives as the Vice President for Strategy and Public Affairs. On this episode of the Everything About Hydrogen podcast the EAH team sits down with Niels to talk about the journey of the clean hydrogen sector over the recent decades and its rise to prominence in the transition to a decarbonized energy future and how modular electrolysis fits into that picture.
The podcast can be found on their website
The podcast can be found on their website
SNG Generation via Power to Gas Technology: Plant Design and Annual Performance Assessment
Nov 2020
Publication
Power to gas (PtG) is an emerging technology that allows to overcome the issues due to the increasingly widespread use of intermittent renewable energy sources (IRES). Via water electrolysis power surplus on the electric grid is converted into hydrogen or into synthetic natural gas (SNG) that can be directly injected in the natural gas network for long-term energy storage. The core units of the Power to synthetic natural gas (PtSNG) plant are the electrolyzer and the methanation reactors where the renewable electrolytic hydrogen is converted to synthetic natural gas by adding carbon dioxide. A technical issue of the PtSNG plant is the different dynamics of the electrolysis unit and the methanation unit. The use of a hydrogen storage system can help to decouple these two subsystems and to manage the methanation unit for assuring long operation time and reducing the number of shutdowns. The purpose of this paper is to evaluate the energy storage potential and the technical feasibility of the PtSNG concept to store intermittent renewable sources. Therefore different plant sizes (1 3 and 6 MW) have been defined and investigated by varying the ratio between the renewable electric energy sent to the plant and the total electric energy generated by the renewable energy source (RES) facility based on a 12 MW wind farm. The analysis has been carried out by developing a thermochemical and electrochemical model and a dynamic model. The first allows to predict the plant performance in steady state. The second allows to forecast the annual performance and the operation time of the plant by implementing the control strategy of the storage unit. The annual overall efficiencies are in the range of 42–44% low heating value (LHV basis). The plant load factor i.e. the ratio between the annual chemical energy of the produced SNG and the plant capacity results equal to 60.0% 46.5% and 35.4% for 1 3 and 6 MW PtSNG sizes respectively.
A Combined Chemical-Electrochemical Process to Capture CO2 and Produce Hydrogen and Electricity
Sep 2021
Publication
Several carbon sequestration technologies have been proposed to utilize carbon dioxide (CO2 ) to produce energy and chemical compounds. However feasible technologies have not been adopted due to the low efficiency conversion rate and high-energy requirements. Process intensification increases the process productivity and efficiency by combining chemical reactions and separation operations. In this work we present a model of a chemical-electrochemical cyclical process that can capture carbon dioxide as a bicarbonate salt. The proposed process also produces hydrogen and electrical energy. Carbon capture is enhanced by the reaction at the cathode that displaces the equilibrium into bicarbonate production. Literature data show that the cyclic process can produce stable operation for long times by preserving ionic balance using a suitable ionic membrane that regulates ionic flows between the two half-cells. Numerical simulations have validated the proof of concept. The proposed process could serve as a novel CO2 sequestration technology while producing electrical energy and hydrogen.
Recent Advances in Hybrid Water Electrolysis for Energy-saving Hydrogen Production
Nov 2022
Publication
Electricity-driven water splitting to convert water into hydrogen (H2) has been widely regarded as an efficient approach for H2 production. Nevertheless the energy conversion efficiency of it is greatly limited due to the disadvantage of the sluggish kinetic of oxidation evolution reaction (OER). To effectively address the issue a novel concept of hybrid water electrolysis has been developed for energy– saving H2 production. This strategy aims to replace the sluggish kinetics of OER by utilizing thermodynamically favorable organics oxidation reaction to replace OER. Herein recent advances in such water splitting system for boosting H2 evolution under low cell voltage are systematically summarized. Some notable progress of different organics oxidation reactions coupled with hydrogen evolution reaction (HER) are discussed in detail. To facilitate the development of hybrid water electrolysis the major challenges and perspectives are also proposed.
System Dynamic Model for the Accumulation of Renewable Electricity using Power-to-Gas and Power-to-Liquid Concepts
Feb 2016
Publication
When the renewable energy is used the challenge is match the supply of intermittent energy with the demand for energy therefore the energy storage solutions should be used. This paper is dedicated to hydrogen accumulation from wind sources. The case study investigates the conceptual system that uses intermitted renewable energy resources to produce hydrogen (power-to-gas concept) and fuel (power-to-liquid concept). For this specific case study hydrogen is produced from surplus electricity generated by wind power plant trough electrolysis process and fuel is obtained by upgrading biogas to biomethane using hydrogen. System dynamic model is created for this conceptual system. The developed system dynamics model has been used to simulate 2 different scenarios. The results show that in both scenarios the point at which the all electricity needs of Latvia are covered is obtained. Moreover the methodology of system dynamics used in this paper is white-box model that allows to apply the developed model to other case studies and/or to modify model based on the newest data. The developed model can be used for both scientific research and policy makers to better understand the dynamic relation within the system and the response of system to changes in both internal and external factors.
Investigation on Green Hydrogen Generation Devices Dedicated for Integrated Renewable Energy Farm: Solar and Wind
Oct 2022
Publication
This study presents a comprehensive methodology to evaluate plants that integrate renewable energy sources and hydrogen generation devices. The paper focuses on presenting the methods for devices’ operation assessment taking into account the annual operation. Multiple effectiveness indices have been presented. On the basis of experimental investigation with the hydrogen generator the methods for assessing its operation during start-up phase and sudden change in the supply current were proposed. The results of the experiments and the provided mathematical models show that dynamics of the hydrogen generator should be taken into account when selecting the suitable device for cooperation with variable renewable energy. It is especially important for multiple start-ups throughout the day due to significant differences in the amount of hydrogen produced by devices characterized by the same efficiency yet various time constants. Methodology for selecting the optimal nominal power for hydrogen generator to cooperate with given renewable sources was developed. It was proven the optimal power depends on the type of the renewable source and minimal load of the hydrogen generator. Several case studies including the integration of wind and solar energy farms to yield a 10 MW renewable energy farm were considered and the minimal load of the hydrogen generator impacts the annual operation of the device has been presented. The paper provides a set of tools to contribute to the development of sustainable energy plants. The methods proposed in this paper are universal and can be used for various renewable energy sources.
Advances in Hydrogen Production from Natural Gas Reforming
Jun 2021
Publication
Steam natural gas reforming is the preferred technique presently used to produce hydrogen. Proposed in 1932 the technique is very well established but still subjected to perfections. Herein first the improvements being sought in catalysts and processes are reviewed and then the advantage of replacing the energy supply from burning fuels with concentrated solar energy is discussed. It is especially this advance that may drastically reduce the economic and environmental cost of hydrogen production. Steam reforming can be easily integrated into concentrated solar with thermal storage for continuous hydrogen production.
Decarbonization in Ammonia Production, New Technological Methods in Industrial Scale Ammonia Production and Critical Evaluations
Oct 2021
Publication
With the synthesis of ammonia with chemical methods global carbon emission is the biggest threat to global warming. However the dependence of the agricultural industry on ammonia production brings with it various research studies in order to minimize the carbon emission that occurs with the ammonia synthesis process. In order to completely eliminate the carbon emissions from ammonia production both the hydrogen and the energy needed for the operation of the process must be obtained from renewable sources. Thus hydrogen can be produced commercially in a variety of ways. Many processes are discussed to accompany the Haber Bosch process in ammonia production as potential competitors. In addition to parameters such as temperature and pressure various plasma catalysts are being studied to accelerate the ammonia production reaction. In this study various alternative processes for the capture storage and complete removal of carbon gas released during the current ammonia production are evaluated and the current conditions related to the applicability of these processes are discussed. In addition it has been discussed under which conditions it is possible to produce larger capacities as needed in the processes studied in order to reduce carbon gas emissions during ammonia production in order to provide raw material source for fertilizer production and energy sector. However if the hydrogen gas required for ammonia production is produced using a solid oxide electrolysis cell the reduction in the energy requirement of the process and in this case the reduction of energy costs shows that it will play an important role in determining the method to be used for ammonia production. In addition it is predicted that working at lower temperature (<400 °C) and pressure (<10 bar) values in existing ammonia production technologies despite increasing possible energy costs will significantly reduce process operating costs.
An Overview of Water Electrolysis Technologies for Green Hydrogen Production
Oct 2022
Publication
Decarbonizing the planet is one of the major goals that countries around the world have set for 2050 to mitigate the effects of climate change. To achieve these goals green hydrogen that can be produced from the electrolysis of water is an important key solution to tackle global decarbonization. Consequently in recent years there is an increase in interest towards green hydrogen production through the electrolysis process for large-scale implementation of renewable energy based power plants and other industrial and transportation applications. The main objective of this study was to provide a comprehensive review of various green hydrogen production technologies especially on water electrolysis. In this review various water electrolysis technologies and their techno-commercial prospects including hydrogen production cost along with recent developments in electrode materials and their challenges were summarized. Further some of the most successful results also were described. Moreover this review aims to identify the gaps in water electrolysis research and development towards the techno-commercial perspective. In addition some of the commercial electrolyzer performances and their limitations also were described along with possible solutions for cost-effective hydrogen production Finally we outlined our ideas and possible solutions for driving cost-effective green hydrogen production for commercial applications. This information will provide future research directions and a road map for the development/implementation of commercially viable green hydrogen projects.
Biohydrogen—A Green Fuel for Sustainable Energy Solutions
Oct 2022
Publication
Energy plays a crucial role in the sustainable development of modern nations. Today hydrogen is considered the most promising alternative fuel as it can be generated from clean and green sources. Moreover it is an efficient energy carrier because hydrogen burning only generates water as a byproduct. Currently it is generated from natural gas. However it can be produced using other methods i.e. physicochemical thermal and biological. The biological method is considered more environmentally friendly and pollution free. This paper aims to provide an updated review of biohydrogen production via photofermentation dark fermentation and microbial electrolysis cells using different waste materials as feedstocks. Besides the role of nanotechnology in enhancing biohydrogen production is examined. Under anaerobic conditions hydrogen is produced during the conversion of organic substrate into organic acids using fermentative bacteria and during the conversion of organic acids into hydrogen and carbon dioxide using photofermentative bacteria. Different factors that enhance the biohydrogen production of these organisms either combined or sequentially using dark and photofermentation processes are examined and the effect of each factor on biohydrogen production efficiency is reported. A comparison of hydrogen production efficiency between dark fermentation photofermentation and two-stage processes is also presented.
Prospect of Green Hydrogen Generation from Hybrid Renewable Energy Sources: A Review
Feb 2023
Publication
Hydrogen is one of the prospective clean energies that could potentially address two pressing areas of global concern namely energy crises and environmental issues. Nowadays fossil‐ based technologies are widely used to produce hydrogen and release higher greenhouse gas emis‐ sions during the process. Decarbonizing the planet has been one of the major goals in the recent decades. To achieve this goal it is necessary to find clean sustainable and reliable hydrogen pro‐ duction technologies with low costs and zero emissions. Therefore this study aims to analyse the hydrogen generation from solar and wind energy sources and observe broad prospects with hybrid renewable energy sources in producing green hydrogen. The study mainly focuses on the critical assessment of solar wind and hybrid‐powered electrolysis technologies in producing hydrogen. Furthermore the key challenges and opportunities associated with commercial‐scale deployment are addressed. Finally the potential applications and their scopes are discussed to analyse the important barriers to the overall commercial development of solar‐wind‐based hydrogen production systems. The study found that the production of hydrogen appears to be the best candidate to be employed for multiple purposes blending the roles of fuel energy carrier and energy storage modality. Further studies are recommended to find technical and sustainable solutions to overcome the current issues that are identified in this study.
Green and Blue Hydrogen Production: An Overview in Colombia
Nov 2022
Publication
Colombia a privileged country in terms of diversity availability of natural resources and geographical location has set a roadmap for hydrogen as part of the energy transition plan proposed in 2021. To reduce its emissions in the mid-term and foster its economy hydrogen production should be green and blue with specific targets set for 2030 for the hydrogen costs and produced quantities. This work compares the state-of-the-art production of blue and green hydrogen and how Colombia is doing in each pathway. A deeper analysis considers the advantages of Colombia’s natural resources the possible paths the government could follow and the feedstock’s geographical location for hydrogen production and transportation. Then one discusses what may be the next steps in terms of policies and developments to succeed in implementing the plan. Overall it is concluded that green hydrogen could be the faster more sustainable and more efficient method to implement in Colombia. However blue hydrogen could play an essential role if oil and gas companies assess the advantages of carbon dioxide utilization and promote its deployment.
Proton Exchange Membrane Electrolyzer Emulator for Power Electronics Testing Applications
Mar 2021
Publication
This article aims to develop a proton exchange membrane (PEM) electrolyzer emulator. This emulator is realized through an equivalent electrical scheme. It allows taking into consideration the dynamic operation of PEM electrolyzers which is generally neglected in the literature. PEM electrolyzer dynamics are reproduced by the use of supercapacitors due to the high value of the equivalent double-layer capacitance value. Steady-state and dynamics operations are investigated in this work. The design criteria are addressed. The PEM electrolyzer emulator is validated by using a 400-W commercial PEM electrolyzer. This emulator is conceived to test new DC-DC converters to supply the PEM ELs and their control as well avoiding the risk to damage a real electrolyzer for experiment purposes. The proposed approach is valid both for a single cell and for the whole stack emulation.
Optimising Onshore Wind with Energy Storage Considering Curtailment
May 2022
Publication
Operating energy storage alongside onshore wind can improve its economics whilst providing a pathway for otherwise curtailed generation. In this work we present a framework to evaluate the economic potential of onshore wind co-located with battery storage (BS) and a hydrogen electrolyser (HE). This model is applied to a case study in Great Britain using historic data and considering local network charges and the cost of using curtailed power capturing an often neglected element of competition. We use a Markov Chain to model wind curtailment and determine the optimised scheduling of the storage as we vary price parameters and storage sizing. Finally by considering storage CAPEX and comparing against the case with no storage we can determine the value added (or lost) by different sized BS and HE for an onshore wind owner as a function of power purchase agreement (PPA) and green hydrogen market price. Results show that value added increases when HE is increased and when BS is decreased. Additionally a 10 MW electrolysers uses 27% more curtailed wind than 10 MW BS.
Optimization of Renewable Energy Supply Chain for Sustainable Hydrogen Energy Production from Plastic Waste
Dec 2023
Publication
Disposing of plastic waste through burial or burning leads to air pollution issues while also contributing to gas emissions and plastic waste spreading underground into seas via springs. Henceforth this research aims at reducing plastic waste volume while simultaneously generating clean energy. Hydrogen energy is a promising fuel source that holds great value for humanity. However achieving clean hydrogen energy poses challenges including high costs and complex production processes especially on a national scale. This research focuses on Iran as a country capable of producing this energy examining the production process along with related challenges and the general supply chain. These challenges encompass selecting appropriate raw materials based on chosen technologies factory capacities storage methods and transportation flow among different provinces of the country. To deal with these challenges a mixed-integer linear programming model is developed to optimize the hydrogen supply chain and make optimal decisions about the mentioned problems. The supply chain model estimates an average cost—IRR 4 million (approximately USD 8)—per kilogram of hydrogen energy that is available in syngas during the initial period; however subsequent periods may see costs decrease to IRR 1 million (approximately USD 2) factoring in return-on-investment rates.
Profitability Model of Green Hydrogen Production on an Existing Wind Power Plant Location
Feb 2024
Publication
This paper presents a new economic profitability model for a power-to-gas plant producing green hydrogen at the site of an existing wind power plant injected into the gas grid. The model is based on a 42 MW wind power plant for which an optimal electrolyzer of 10 MW was calculated based on the 2500 equivalent full load hours per year and the projection of electricity prices. The model is calculated on an hourly level for all variables of the 25 years of the model. With the calculated breakeven electricity price of 74.23 EUR/MWh and the price of green hydrogen production of 99.44 EUR/MWh in 2045 the wind power plant would produce 22410 MWh of green hydrogen from 31% of its total electricity production. Green hydrogen injected into the gas system would reduce the level of CO2 emissions by 4482 tons. However with the projected prices of natural gas and electricity the wind power plant would cover only 20% of the income generated by the electricity delivered to the grid by producing green hydrogen. By calculating different scenarios in the model the authors concluded that the introduction of a premium subsidy model is necessary to accelerate deployment of electrolyzers at the site of an existing wind power plant in order to increase the wind farm profitability.
An Overview of Hydrogen Energy Generation
Feb 2024
Publication
The global issue of climate change caused by humans and its inextricable linkage to our present and future energy demand presents the biggest challenge facing our globe. Hydrogen has been introduced as a new renewable energy resource. It is envisaged to be a crucial vector in the vast low-carbon transition to mitigate climate change minimize oil reliance reinforce energy security solve the intermittency of renewable energy resources and ameliorate energy performance in the transportation sector by using it in energy storage energy generation and transport sectors. Many technologies have been developed to generate hydrogen. The current paper presents a review of the current and developing technologies to produce hydrogen from fossil fuels and alternative resources like water and biomass. The results showed that reformation and gasification are the most mature and used technologies. However the weaknesses of these technologies include high energy consumption and high carbon emissions. Thermochemical water splitting biohydrogen and photo-electrolysis are long-term and clean technologies but they require more technical development and cost reduction to implement reformation technologies efficiently and on a large scale. A combination of water electrolysis with renewable energy resources is an ecofriendly method. Since hydrogen is viewed as a considerable game-changer for future fuels this paper also highlights the challenges facing hydrogen generation. Moreover an economic analysis of the technologies used to generate hydrogen is carried out in this study.
Influence of Cs Promoter on Ethanol Steam-Reforming Selectivity of Pt/m-ZrO2 Catalysts at Low Temperature
Sep 2021
Publication
The decarboxylation pathway in ethanol steam reforming ultimately favors higher selectivity to hydrogen over the decarbonylation mechanism. The addition of an optimized amount of Cs to Pt/m-ZrO2 catalysts increases the basicity and promotes the decarboxylation route converting ethanol to mainly H2 CO2 and CH4 at low temperature with virtually no decarbonylation being detected. This offers the potential to feed the product stream into a conventional methane steam reformer for the production of hydrogen with higher selectivity. DRIFTS and the temperature-programmed reaction of ethanol steam reforming as well as fixed bed catalyst testing revealed that the addition of just 2.9% Cs was able to stave off decarbonylation almost completely by attenuating the metallic function. This occurs with a decrease in ethanol conversion of just 16% relative to the undoped catalyst. In comparison with our previous work with Na this amount is—on an equivalent atomic basis—just 28% of the amount of Na that is required to achieve the same effect. Thus Cs is a much more efficient promoter than Na in facilitating decarboxylation.
A New Energy System Based on Biomass Gasification for Hydrogen and Power Production
Apr 2020
Publication
In this paper a new gasification system is developed for the three useful outputs of electricity heat and hydrogen and reported for practical energy applications. The study also investigates the composition of syngas leaving biomass gasifier. The composition of syngas is represented by the fractions of hydrogen carbon dioxide carbon monoxide and water. The integrated energy system comprises of an entrained flow gasifier a Cryogenic Air Separation (CAS) unit a double-stage Rankine cycle Water Gas Shift Reactor (WGSR) a combined gas–steam power cycle and a Proton Exchange Membrane (PEM) electrolyzer. The whole integrated system is modeled in the Aspen plus 9.0 excluding the PEM electrolyzer which is modeled in Engineering Equation Solver (EES). A comprehensive parametric investigation is conducted by varying numerous parameters like biomass flow rate steam flow rate air input flow rate combustion reactor temperature and power supplied to the electrolyzer. The system is designed in a way to supply the power produced by the steam Rankine cycle to the PEM electrolyzer for hydrogen production. The overall energy efficiency is obtained to be 53.7% where the exergy efficiency is found to be 45.5%. Furthermore the effect of the biomass flow rate is investigated on the various system operational parameters.
Renewable Hydrogen Implementations for Combined Energy Storage, Transportation and Stationary Applications
Dec 2019
Publication
The purpose of this paper is to discuss the potential of hydrogen obtained from renewable sources for energy generation and storage systems. The first part of analysis will address such issues as various methods of green hydrogen production storage and transportation. The review of hydrogen generation methods will be followed by the critical analysis and the selection of production method. This selection is justified by the results of the comparative research on alternative green hydrogen generation technologies with focus on their environmental impacts and costs. The comparative analysis includes the biomass-based methods as well as water splitting and photo-catalysis methods while water electrolysis is taken as a benchmark. Hydrogen storage and transportation issues will be further discussed in purpose to form the list of recommended solutions. In the second part of the paper the technology readiness and technical feasibility for joint hydrogen applications will be analysed. This will include the energy storage and production systems based on renewable hydrogen in combination with hydrogen usage in mobility systems as well as the stationary applications in buildings such as combined heat and power (CHP) plants or fuel cell electric generators. Based on the analysis of the selected case studies the author will discuss the role of hydrogen for the carbon emission reduction with the stress on the real value of carbon footprint of hydrogen depending on the gas source storage transportation and applications.
Optimal Day-ahead Dispatch of an Alkaline Electrolyser System Concerning Thermal–electric Properties and State-transitional Dynamics
Oct 2021
Publication
Green hydrogen is viewed as a promising energy carrier for sustainable development goals. However it has suffered from high costs hindering its implementation. For a stakeholder who considers both renewable energy and electrolysis units it is important to exploit the flexibility of such portfolios to maximize system operational revenues. To this end an electrolyser model that can characterize its dynamic behavior is required in both electric and thermal aspects. In this paper we develop a comprehensive alkaline electrolyser model that is capable of describing its hydrogen production properties temperature variations and state transitions (among production stand-by and off states). This model is further used to study the optimal dispatch of an electrolyser based on a real-world hybrid wind/electrolyser system. The results show the model can effectively capture the coupling between thermal–electric dynamics and on–off performance of an electrolyser. The flexible operation strategy based on this model is proven to significantly increase daily revenues under different spot price conditions for electricity. Comparing the model with the ones derived from conventional modeling methods reveals this model offers more operating details and highlights several operational features such as the preference for working at partial load conditions although at the expense of more computing resources. It is suggested to use this model in studies related to energy integration operation planning and control scheme development in which the multi-domain dynamic properties of electrolysers in electricity/gas/heat need to be properly characterized. A sensitivity analysis on key parameters of such electrolyser system is also introduced to connect the daily operation with long-term planning.
Towards Computer-Aided Graphene Covered TiO2-Cu(CuxOy) Composite Design for the Purpose of Photoinduced Hydrogen Evolution
May 2021
Publication
In search a hydrogen source we synthesized TiO2-Cu-graphene composite photocatalyst for hydrogen evolution. The catalyst is a new and unique material as it consists of copper-decorated TiO2 particles covered tightly in graphene and obtained in a fluidized bed reactor. Both reduction of copper from Cu(CH3COO) at the surface of TiO2 particles and covering of TiO2-Cu in graphene thin layer by Chemical Vapour Deposition (CVD) were performed subsequently in the flow reactor by manipulating the gas composition. Obtained photocatalysts were tested in regard to hydrogen generation from photo-induced water conversion with methanol as sacrificial agent. The hydrogen generation rate for the most active sample reached 2296.27 µmol H2 h−1 gcat−1. Combining experimental and computational approaches enabled to define the optimum combination of the synthesis parameters resulting in the highest photocatalytic activity for water splitting for green hydrogen production. The results indicate that the major factor affecting hydrogen production is temperature of the TiO2-Cu-graphene composite synthesis which in turn is inversely correlated to photoactivity.
Analysis of Trends and Emerging Technologies in Water Electrolysis Research Based on a Computational Method: A Comparison with Fuel Cell Research
Feb 2018
Publication
Water electrolysis for hydrogen production has received increasing attention especially for accumulating renewable energy. Here we comprehensively reviewed all water electrolysis research areas through computational analysis using a citation network to objectively detect emerging technologies and provide interdisciplinary data for forecasting trends. The results show that all research areas increase their publication counts per year and the following two areas are particularly increasing in terms of number of publications: “microbial electrolysis” and “catalysts in an alkaline water electrolyzer (AWE) and in a polymer electrolyte membrane water electrolyzer (PEME).”. Other research areas such as AWE and PEME systems solid oxide electrolysis and the whole renewable energy system have recently received several review papers although papers that focus on specific technologies and are cited frequently have not been published within the citation network. This indicates that these areas receive attention but there are no novel technologies that are the center of the citation network. Emerging technologies detected within these research areas are presented in this review. Furthermore a comparison with fuel cell research is conducted because water electrolysis is the reverse reaction to fuel cells and similar technologies are employed in both areas. Technologies that are not transferred between fuel cells and water electrolysis are introduced and future water electrolysis trends are discussed.
Alkaline Water Electrolysis Powered by Renewable Energy: A Review
Feb 2020
Publication
Alkaline water electrolysis is a key technology for large-scale hydrogen production powered by renewable energy. As conventional electrolyzers are designed for operation at fixed process conditions the implementation of fluctuating and highly intermittent renewable energy is challenging. This contribution shows the recent state of system descriptions for alkaline water electrolysis and renewable energies such as solar and wind power. Each component of a hydrogen energy system needs to be optimized to increase the operation time and system efficiency. Only in this way can hydrogen produced by electrolysis processes be competitive with the conventional path based on fossil energy sources. Conventional alkaline water electrolyzers show a limited part-load range due to an increased gas impurity at low power availability. As explosive mixtures of hydrogen and oxygen must be prevented a safety shutdown is performed when reaching specific gas contamination. Furthermore the cell voltage should be optimized to maintain a high efficiency. While photovoltaic panels can be directly coupled to alkaline water electrolyzers wind turbines require suitable converters with additional losses. By combining alkaline water electrolysis with hydrogen storage tanks and fuel cells power grid stabilization can be performed. As a consequence the conventional spinning reserve can be reduced which additionally lowers the carbon dioxide emissions.
Blue Hydrogen
Apr 2021
Publication
The urgency of reaching net-zero emissions requires a rapid acceleration in the deployment of all emissions reducing technologies. Near-zero emissions hydrogen (clean hydrogen) has the potential to make a significant contribution to emissions reduction in the power generation transportation and industrial sectors.
As part of the Circular Carbon Economy: Keystone to Global Sustainability series with the Center on Global Energy Policy at Columbia University SIPA this report explores the potential contribution of blue hydrogen to climate mitigation.
The report looks at:
As part of the Circular Carbon Economy: Keystone to Global Sustainability series with the Center on Global Energy Policy at Columbia University SIPA this report explores the potential contribution of blue hydrogen to climate mitigation.
The report looks at:
- Cost drivers for renewable hydrogen and hydrogen produced with fossil fuels and CCS;
- Resource requirements and cost reduction opportunities for clean hydrogen; and
- Policy recommendations to drive investment in clean hydrogen production.
- Blue hydrogen is well placed to kickstart the rapid increase in the utilisation of clean hydrogen for climate mitigation purposes but requires strong and sustained policy to incentivise investment at the rate necessary to meet global climate goals.
Performance Study on Methanol Steam Reforming Rib Micro-Reactor with Waste Heat Recovery
Mar 2020
Publication
Automobile exhaust heat recovery is considered to be an effective means to enhance fuel utilization. The catalytic production of hydrogen by methanol steam reforming is an attractive option for onboard mobile applications due to its many advantages. However the reformers of conventional packed bed type suffer from axial temperature gradients and cold spots resulting from severe limitations of mass and heat transfer. These disadvantages limit reformers to a low efficiency of catalyst utilization. A novel rib microreactor was designed for the hydrogen production from methanol steam reforming heated by automobile exhaust and the effect of inlet exhaust and methanol steam on reactor performance was numerically analyzed in detail with computational fluid dynamics. The results showed that the best operating parameters were the counter flow water-to-alcohol (W/A) of 1.3 exhaust inlet velocity of 1.1 m/s and exhaust inlet temperature of 773 K when the inlet velocity and inlet temperature of the reactant were 0.1 m/s and 493 K respectively. At this condition a methanol conversion of 99.4% and thermal efficiency of 28% were achieved together with a hydrogen content of 69.6%.
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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