Production & Supply Chain

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.