Production & Supply Chain

Proton exchange membrane water electrolysis (PEMWE) is a key technology for future sustainable energy systems. Proton exchange membrane (PEM) electrolysis cells use iridium one of the scarcest elements on earth as catalyst for the oxygen evolution reaction. In the present study the expected iridium demand and potential bottlenecks in the realization of PEMWE for hydrogen production in the targeted GW a−1 scale are assessed in a model built on three pillars: (i) an in-depth analysis of iridium reserves and mine production (ii) technical prospects for the optimization of PEM water electrolyzers and (iii) PEMWE installation rates for a market ramp-up and maturation model covering 50 years. As a main result two necessary preconditions have been identified to meet the immense future iridium demand: first the dramatic reduction of iridium catalyst loading in PEM electrolysis cells and second the development of a recycling infrastructure for iridium catalysts with technical end-of-life recycling rates of at least 90%.

The production of blue hydrogen through sorption-enhanced processes has emerged as a suitable option to reduce greenhouse gas emissions. Sorption-enhanced steam–methane reforming (SESMR) is a process intensification of highly endothermic steam–methane reforming (SMR) ensured by in situ carbon capture through a solid sorbent making hydrogen production efficient and more environmentally sustainable. In this study a comprehensive energy model of SESMR was developed to carry out a detailed energy characterization of the process with the aim of filling a current knowledge gap in the literature. The model was applied to a bench-scale multicycle SESMR/sorbent regeneration test to provide an energy insight into the process. Besides the experimental advantages of higher hydrogen concentration (90 mol% dry basis 70 mol% wet basis) and performance of CO2 capture the developed energy model demonstrated that SESMR allows for substantially complete energy self-sufficiency through the process. In comparison to SMR with the same process conditions (650 ◦C 1 atm) performed in the same experimental rig SESMR improved the energy efficiency by about 10% further reducing energy needs.

To efficiently convert and utilize intermittent solar energy a novel solar-driven ethanol steam reforming (ESR) system integrated with a membrane reactor is proposed. It has the potential to convert low-grade solar thermal energy into high energy level chemical energy. Driven by chemical potential hydrogen permeation membranes (HPM) can separate the generated hydrogen and shift the ESR equilibrium forward to increase conversion and thermodynamic efficiency. The thermodynamic and environmental performances are analyzed via numerical simulation under a reaction temperature range of 100–400 ◦C with permeate pressures of 0.01–0.75 bar. The highest theoretical conversion rate is 98.3% at 100 ◦C and 0.01 bar while the highest first-law efficiency solar-to-fuel efficiency and exergy efficiency are 82.3% 45.3% and 70.4% at 215 ◦C and 0.20 bar. The standard coal saving rate (SCSR) and carbon dioxide reduction rate (CDRR) are maximums of 101 g·m−2 ·h −1 and 247 g·m−2 ·h −1 at 200 ◦C and 0.20 bar with a hydrogen generation rate of 22.4 mol·m−2 ·h −1 . This study illustrates the feasibility of solar-driven ESR integrated with a membrane reactor and distinguishes a novel approach for distributed hydrogen generation and solar energy utilization and upgradation.

Hydrogen production using renewable power is becoming an essential pillar for future sustainable energy sector development worldwide. The Sultanate of Oman is presently integrating renewable power generations with a large share of solar photovoltaic (PV) systems. The possibility of using the solar potential of the Sultanate can increase energy security and contribute to the development of the sustainable energy sector not only for the country but also for the international community. This study presents the hydrogen production potential using solar resources available in the Sultanate. About 15 locations throughout the Sultanate are considered to assess the hydrogen production opportunity using a solar PV system. A rank of merit order of the locations for producing hydrogen is identified. It reveals that Thumrait and Marmul are the most suitable locations whereas Sur is the least qualified. This study also assesses the economic feasibility of hydrogen production which shows that the levelized cost of hydrogen (LCOH) in the most suitable site Thumrait is 6.31 USD/kg. The LCOH in the least convenient location Sur is 7.32 USD/kg. Finally a sensitivity analysis is performed to reveal the most significant influential factor affecting the future’s green hydrogen production cost. The findings indicate that green hydrogen production using solar power in the Sultanate is promising and the LCOH is consistent with other studies worldwide.

Dedicated offshore wind farms for hydrogen production are a promising option to unlock the full potential of offshore wind energy attain decarbonisation and energy security targets in electricity and other sectors and cope with grid expansion constraints. Current knowledge on these systems is limited particularly the economic aspects. Therefore a new integrated and analytical model for viability assessment of hydrogen production from dedicated offshore wind farms is developed in this paper. This includes the formulae for calculating wind power output electrolysis plant size and hydrogen production from time-varying wind speed. All the costs are projected to a specified time using both Discounted Payback (DPB) and Net Present Value (NPV) to consider the value of capital over time. A case study considers a hypothetical wind farm of 101.3 MW situated in a potential offshore wind development pipeline off the East Coast of Ireland. All the costs of the wind farm and the electrolysis plant are for 2030 based on reference costs in the literature. Proton exchange membrane electrolysers and underground storage of hydrogen are used. The analysis shows that the DPB and NPV flows for several scenarios of storage are in good agreement and that the viability model performs well. The offshore wind farm – hydrogen production system is found to be profitable in 2030 at a hydrogen price of €5/kg and underground storage capacities ranging from 2 days to 45 days of hydrogen production. The model is helpful for rapid assessment or optimisation of both economics and feasibility of dedicated offshore wind farm – hydrogen production systems.

Hydrogen production is the key in utilizing an excess renewable energy. Many studies and projects looked at the energy management systems (EMSs) that allow to couple hydrogen production with renewable generation. In the majority of these studies however hydrogen demand is either produced for powering fuel cells or sold to the external hydrogen market. Hydrogen demand from actual industrial plants is rarely considered. In this paper we propose an EMS based on the industrial cluster of GreenLab Skive (GLS) that can minimize the system’s operational cost or maximize its green hydrogen production. EMS utilizes a conventional and P2X demand response (DR) flexibility from electrolysis plant hydrogen storage tank electric battery and hydrogen-consuming plants to design the optimal schedule with maximized benefits. A potential addition to the existing components at GLS - an ammonia plant is modelled to identify its P2X potential and assess the economic viability of its construction. The results show a potential reduction of 51.5–61.6% for the total operational cost of the system and an increase of the share of green hydrogen by 10.4–37.6% due to EMS operation.

This article reviews a method of hydrogen production based on partial non-catalytic oxidation of natural gas in an original synthesis gas generator. The working principles of the unit are similar to those of liquid-propellant rocket engines. This paper presents a description of the operation and technical characteristics of the synthesis gas generator. Its application in the creation of small-scaled plants with a capacity of up to 5–7 thousand m3/h of hydrogen is justified. Hydrogen production in the developed installation requires a two-stage method and includes a technological unit for producing a hydrogen-containing gas. Typical balance compositions of hydrogen-containing gas at the synthesis gas generator’s outlet are given. To increase the hydrogen concentration it is proposed to carry out a two-stage steam catalytic conversion of carbon monoxide contained in the hydrogen-containing gas at the synthesis gas generator’s outlet using a single Cu–Zn–cementcontaining composition. Based on thermodynamic calculations quasi-optimal modes of natural gas partial oxidation with oxygen are formulated and the results of material balance calculation for the installation are presented. In order to produce “blue” hydrogen the scheme of carbon dioxide separation and liquefaction is developed. The conclusion section of the paper contains the test results of a pilot demonstration unit and the recommendations for improving the technology and preventing soot formation.

This paper discusses the techno-economic assessment of hydrogen production from biogas with conventional systems. The work is part of the European project BIONICO whose purpose is to develop and test a membrane reactor (MR) for hydrogen production from biogas. Within the BIONICO project steam reforming (SR) and autothermal reforming (ATR) have been identified as well-known technologies for hydrogen production from biogas. Two biogases were examined: one produced by landfill and the other one by anaerobic digester. The purification unit required in the conventional plants has been studied and modeled in detail using Aspen Adsorption. A pressure swing adsorption system (PSA) with two and four beds and a vacuum PSA (VPSA) made of four beds are compared. VPSA operates at sub-atmospheric pressure thus increasing the recovery: results of the simulations show that the performances strongly depend on the design choices and on the gas feeding the purification unit. The best purity and recovery values were obtained with the VPSA system which achieves a recovery between 50% and 60% at a vacuum pressure of 0.1 bar and a hydrogen purity of 99.999%. The SR and ATR plants were designed in Aspen Plus integrating the studied VPSA model and analyzing the behavior of the systems at the variation of the pressure and the type of input biogas. The SR system achieves a maximum efficiency calculated on the LHV of 52% at 12 bar while the ATR of 28% at 18 bar. The economic analysis determined a hydrogen production cost of around 5 €/kg of hydrogen for the SR case.

In this research we conducted water electrolysis experiments of a carbon black (CB) based sodium sulfate electrolyte using a Hoffman voltameter. The main objective was to investigate hydrogen production in such systems as well as analyse the electrical properties and thermal properties of nanofluids. A halogen lamp mimicking solar energy was used as a radiation source and a group of comparative tests were also conducted with different irradiation areas. The results showed that by using CB and light it was possible to increase the hydrogen production rate. The optimal CB concentration was 0.1 wt %. At this concentration the hydrogen production rate increased by 30.37% after 20 min of electrolysis. Hence we show that using CB in electrolytes irradiated by solar energy could save the electrical energy necessary for electrolysis processes.

Green hydrogen technology has recently gained in popularity due to the current economic and ecological trends that aim to remove the fossil fuels share in the energy mix. Among various alternatives biogas reforming is an attractive choice for hydrogen production. To meet the authorities’ requirements reforming biogas-enriched natural gas and sole biogas is tempting. Highly effective process conditions of biogas reforming are yet to be designed. The current state of the art lacks proper optimization of the process conditions. The optimization should aim to allow for maximization of the process effectiveness and limitation of the phenomena having an adverse influence on the process itself. One of the issues that should be addressed in optimization is the uniformity of temperature inside a reactor. Here we show an optimization design study that aims to unify temperature distribution by novel arrangements of catalysts segments in the model biogas reforming reactor. The acquired numerical results confirm the possibility of the enhancement of reaction effectiveness coming from improving the thermal conditions. The used amount of catalytic material is remarkably reduced as a side effect of the presented optimization. To ensure an unhindered perception of the reaction improvement the authors proposed a ratio of the hydrogen output and the amount of used catalyst as a measure.

Hydrogen energy as clean and efcient energy is considered signifcant support for the construction of a sustainable society in the face of global climate change and the looming energy revolution. Hydrogen is one of the most important chemical substances on earth and can be obtained through various techniques using renewable and nonrenewable energy sources. However the necessity for a gradual transition to renewable energy sources signifcantly hampers eforts to identify and implement green hydrogen production paths. Therefore this paper’s objective is to provide a technological review of the systems of hydrogen production from solar and wind energy utilizing several types of water electrolyzers. The current paper starts with a short brief about the diferent production techniques. A detailed comparison between water electrolyzer types and a complete illustration of hydrogen production techniques using solar and wind are presented with examples after which an economic assessment of green hydrogen production by comparing the costs of the discussed renewable sources with other production methods. Finally the challenges that face the mentioned production methods are illuminated in the current review.

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

The main objective of this paper is to develop a dynamic emulator of a proton exchange membrane (PEM) electrolyzer (EL) through an equivalent electrical model. Experimental investigations have highlighted the capacitive effect of EL when subjecting to dynamic current profiles which so far has not been reported in the literature. Thanks to a thorough experimental study the electrical domain of a PEM EL composed of 3 cells has been modeled under dynamic operating conditions. The dynamic emulator is based on an equivalent electrical scheme that takes into consideration the dynamic behavior of the EL in cases of sudden variation in the supply current. The model parameters were identified for a suitable current interval to consider them as constant and then tested with experimental data. The obtained results through the developed dynamic emulator have demonstrated its ability to accurately replicate the dynamic behavior of a PEM EL.

Global hydrogen production is dominated by the Steam-Methane Reforming (SMR) route which is associated with significant CO2 emissions and excess process heat. Two paths to lower specific CO2 emissions in SMR hydrogen production are investigated: (1) the integration of CO2 capture and compression for subsequent sequestration or utilization and (2) the integration of electrolysis for increased hydrogen production. In both cases the excess process heat is utilized to drive the emissions reduction options. Four different design regimes for integration of carbon capture and compression with the SMR process are identified. Techno-economic analyses are performed to study the effect of CO2 mitigation on hydrogen production costs compared to grey hydrogen production without emissions mitigation options. Integration with electrolysis is shown to be less attractive compared to the proposed heat and power integration schemes for the SMR process with CO2 capture and compression for subsequent sequestration or utilization which can reduce emissions by 90% with hydrogen production costs increasing only moderately by 13%. This blue hydrogen production is compared in terms of costs and emissions against the emerging alternative production by electrolysis in the context of renewable and fossil electricity generation and electricity mixes while considering life-cycle emissions.

The rising technology of green hydrogen supply systems is expected to be on the horizon. Hydrogen is a clean and renewable energy source with the highest energy content by weight among the fuels and contains about six times more energy than ammonia. Meanwhile ammonia is the most popular substance as a green hydrogen carrier because it does not carry carbon and the total hydrogen content of ammonia is higher than other fuels and is thus suitable to convert to hydrogen. There are several pathways for hydrogen production. The considered aspects herein include hydrogen production technologies pathways based on the raw material and energy sources and different scales. Hydrogen can be produced from ammonia through several technologies such as electro-chemical photocatalytic and thermochemical processes that can be used at production plants and fueling stations taking into consideration the conversion efficiency reactors catalysts and their related economics. The commercial process is conducted by using expensive Ru catalysts in the ammonia converting process but is considered to be replaced by other materials such as Ni Co La and other perovskite catalysts which have high commercial potential with equivalent activity for extracting hydrogen from ammonia. For successful engraftment of ammonia to hydrogen technology into industry integration with green technologies and economic methods as well as safety aspects should be carried out.

The energy transition calls for natural hydrogen exploration with most occurrences discovered either inadvertently or more recently at the location of potentially diffusive circles observed from a change of vegetation cover at the surface. However some notable hydrogen occurrences are not directly associated with the presence of diffusive circles like the Bourakebougou field in Mali. Thus the objective of this work was to highlight geological areas that have some potential to find natural hydrogen in Quebec a Canadian province where no diffusive circles have yet been documented but which is rich in potential source rocks and where no exploration for natural hydrogen has been undertaken so far. A review of the different geological regions of Quebec was undertaken to highlight the relevant characteristics and geographical distribution of geological assemblages that may produce or have produced natural hydrogen in particular iron-rich rocks but also uranium-rich rocks supramature shales and zones where significant structural discontinuities are documented or suspected which may act as conduits for the migration of fluids of mantle origin. In addition to regional and local geological data an inventory of available geochemical data is also carried out to identify potential tracers or proxies to facilitate subsequent exploration efforts. A rating was then proposed based on the quality of the potential source rocks which also considers the presence of reservoir rocks and the proximity to end-users. This analysis allowed rating areas of interest for which fieldwork can be considered thus minimizing the exploratory risks and investments required to develop this resource. The size of the study area (over 1.5 million km2 ) the diversity of its geological environments (from metamorphic cratons to sedimentary basins) and their wide age range (from Archean to Paleozoic) make Quebec a promising territory for natural hydrogen exploration and to test the systematic rating method proposed here.

The water-gas shift reaction (WGSR) is an intermediate reaction in hydrocarbon reforming processes considered one of the most important reactions for hydrogen production. Here water and carbon monoxide molecules react to generate hydrogen and carbon dioxide. From the thermodynamics aspect pressure does not have an impact whereas low-temperature conditions are suitable for high hydrogen selectivity because of the exothermic nature of the WGSR reaction. The performance of this reaction can be greatly enhanced in the presence of suitable catalysts. The WGSR has been widely studied due do the industrial significance resulting in a good volume of open literature on reactor design and catalyst development. A number of review articles are also available on the fundamental aspects of the reaction including thermodynamic analysis reaction condition optimization catalyst design and deactivation studies. Over the past few decades there has been an exceptional development of the catalyst characterization techniques such as near-ambient x-ray photoelectron spectroscopy (NA-XPS) and in situ transmission electron microscopy (in situ TEM) providing atomic level information in presence of gases at elevated temperatures. These tools have been crucial in providing nanoscale structural details and the dynamic changes during reaction conditions which were not available before. The present review is an attempt to gather the recent progress particularly in the past decade on the catalysts for low-temperature WGSR and their structural properties leading to new insights that can be used in the future for effective catalyst design. For the ease of reading the article is divided into subsections based on metals (noble and transition metal) oxide supports and carbon-based supports. It also aims at providing a brief overview of the reaction conditions by including a table of catalysts with synthesis methods reaction conditions and key observations for a quick reference. Based on our study of literature on noble metal catalysts atomic Pt substituted Mn3O4 shows almost full CO conversion at 260 °C itself with zero methane formation. In the case of transition metals group the inclusion of Cu in catalytic system seems to influence the CO conversion significantly and in some cases with CO conversion improvement by 65% at 280 °C. Moreover mesoporous ceria as a catalyst support shows great potential with reports of full CO conversion at a low temperature of 175 °C.

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.

Steam methane reforming (SMR) is the dominant process for hydrogen production which produce large amount of carbon dioxide (CO2) as a by-product. To address concerns about carbon emissions there is an increasing focus on blue hydrogen to mitigate carbon emissions during hydrogen production. However the commercialization of blue hydrogen production (BHP) is hindered by the challenges of high cost and energy consumption. This study proposes a new configuration to address these challenges which is characterized by: (a) the use of piperazine (PZ) as a solvent which has a high CO2 absorption efficiency; (b) a more efficient heat exchange configuration which recovers the waste exergy from flue gas; (c) the advanced flash stripper (AFS) was adopted to reduce the capital cost due to its simpler stripper configuration. In addition the technical and economic performance of the proposed energy and cost-saving blue hydrogen production (ECSB) process is investigated and compared with the standard SMR process. The detailed models of the SMR process and the post-combustion carbon capture (PCC) process were developed and integrated in Aspen plus® V11. The results of the technical analysis showed that the ECSB process with 30 wt.% PZ achieves a 36.3 % reduction in energy penalty when compared to the standard process with 30 wt.% Monoethanolamine (MEA). The results of the economic analysis showed that the lowest levelized cost of blue hydrogen (LCBH) was achieved by the ECSB process with 30 wt.% PZ. Compared to the BHP process with 30 wt.% MEA the LCBH was reduced by 19.7 %.

In this review we want to explain how the burning of fossil fuels is pushing us towards green energy. Actually for a long time we have believed that everything is profitable that resources are unlimited and there are no consequences. However the reality is often disappointing. The use of non-renewable resources the excessive waste production and the abandonment of the task of recycling has created a fragile thread that once broken may never restore itself. Metaphors aside we are talking about our planet the Earth and its unique ability to host life including ourselves. Our world has its balance; when the wind erodes a mountain a beach appears or when a fire devastates an area eventually new life emerges from the ashes. However humans have been distorting this balance for decades. Our evolving way of living has increased the number of resources that each person consumes whether food shelter or energy; we have overworked everything to exhaustion. Scientists worldwide have already said actively and passively that we are facing one of the biggest problems ever: climate change. This is unsustainable and we must try to revert it or if we are too late slow it down as much as possible. To make this happen there are many possible methods. In this review we investigate catalysts for using water as an energy source or instead of water alcohols. On the other hand the recycling of gases such as CO2 and N2O is also addressed but we also observe non-catalytic means of generating energy through solar cell production.

Fossil resources are unevenly distributed on the earth and are finite primary energy which is widely used in the fields of industry transportation and power generation etc.<br/>Primary energies that can replace fossil resources include renewable energy and nuclear energy. Hydrogen has the potential to be secondary energy that can be widely used in industry for various purposes. Nuclear energy can be used for producing hydrogen; it is becoming more important to convert this primary energies into hydrogen. This paper describes the roles of nuclear energy as a primary energy in hydrogen production from the viewpoint of the basics of energy form conversion.

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.

Hydrogen is a source of clean energy as it can produce electricity and heat with water as a by-product and no carbon content is emitted when hydrogen is used as burning fuel in a fuel cell. Hydrogen is a potential energy carrier and powerful fuel as it has high flammability fast flame speed no carbon content and no emission of pollutants. Hydrogen production is possible through different technologies by utilizing several feedstock materials but the main concern in recent years is to reduce the emission of carbon dioxide and other greenhouse gases from energy sectors. Hydrogen production by thermochemical conversion of biomass and greenhouse gases has achieved much attention as researchers have developed several novel thermochemical methods which can be operated with low cost and high efficiency in an environmentally friendly way. This review explained the novel technologies which are being developed for thermochemical hydrogen production with minimum or zero carbon emission. The main concern of this paper was to review the advancements in hydrogen production technologies and to discuss different novel catalysts and novel CO2 -absorbent materials which can enhance the hydrogen production rate with zero carbon emission. Recent developments in thermochemical hydrogen production technologies were discussed in this paper. Biomass gasification and pyrolysis steam methane reforming and thermal plasma are promising thermochemical processes which can be further enhanced by using catalysts and sorbents. This paper also reviewed the developments and influences of different catalysts and sorbents to understand their suitability for continuous clean industrial hydrogen production.

Increasing shares of variable renewable electricity (VRE) generation are necessary for achieving high renewable shares in all energy sectors. This results in increased excess renewable electricity (ERE) at times when supply exceeds demand. ERE can be utilized as a low-emission energy source for sector coupling through hydrogen production via electrolysis which can be used directly or combined with a carbon source to produce electrofuels. Such fuels are crucial for the transport sector where renewable alternatives are scarce. However while ERE increases with raising VRE shares carbon emissions decrease and may become a limited resource with several usage options including carbon storage (CCS). Here we perform a model based analysis for the German case until 2050 with a general analysis for regions with a high VRE reliance. Results indicate that ERE-based electrofuels could achieve a greenhouse gas (GHG) abatement of 74 MtCO2eq yearly (46% of current German transport emissions) by displacing fossil fuels at high fuel-cell electric vehicle (FCEV) shares at a cost of 250–320 V per tCO2eq. The capital expenditure of electrolysers was found not to be crucial for the cost despite low capacity factors due to variable ERE patterns. Carbon will likely become a limiting factor when aiming for stringent climate targets and renewable electricity-based hydrocarbon electrofuels replacing fossil fuels achieve up to 70% more GHG abatement than CCS. Given (1) an unsaturated demand for renewable hydrocarbon fuels (2) a saturated renewable hydrogen demand and (3) unused ERE capacities which would otherwise be curtailed we find that carbon is better used for renewable fuel production than being stored in terms of overall GHG abatement.

In the pathway towards decarbonization hydrogen can provide valid support in different sectors such as transportation iron and steel industries and domestic heating concurrently reducing air pollution. Thanks to its versatility hydrogen can be produced in different ways among which steam reforming of natural gas is still the most commonly used method. Today less than 0.7% of global hydrogen production can be considered low-carbon-emission. Among the various solutions under investigation for low-carbon hydrogen production membrane reactor technology has the potential especially at a small scale to efficiently convert biogas into green hydrogen leading to a substantial process intensification. Fluidized bed membrane reactors for autothermal reforming of biogas have reached industrial maturity. Reliable modelling support is thus necessary to develop their full potential. In this work a mathematical model of the reactor is used to provide guidelines for their design and operations in off-design conditions. The analysis shows the influence of temperature pressures catalyst and steam amounts and inlet temperature. Moreover the influence of different membrane lengths numbers and pitches is investigated. From the results guidelines are provided to properly design the geometry to obtain a set recovery factor value and hydrogen production. For a given reactor geometry and fluidization velocity operating the reactor at 12 bar and the permeate-side pressure of 0.1 bar while increasing reactor temperature from 450 to 500 °C leads to an increase of 33% in hydrogen production and about 40% in HRF. At a reactor temperature of 500 °C going from 8 to 20 bar inside the reactor doubled hydrogen production with a loss in recovery factor of about 16%. With the reactor at 12 bar a vacuum pressure of 0.5 bar reduces hydrogen production by 43% and HRF by 45%. With the given catalyst it is sufficient to have only 20% of solids filled into the reactor being catalytic particles. With the fixed operating conditions it is worth mentioning that by adding membranes and maintaining the same spacing it is possible to increase hydrogen production proportionally to the membrane area maintaining the same HRF.