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Hydrogen can be found in many organic compounds other than water. It is the most
abundant element on Earth, but it does not occur naturally as a gas. It is always
combined with other elements, such as with oxygen to make water. Once separated
from another element, hydrogen can be burned as a fuel or converted into electricity.
A fuel cell uses the...
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Within the Cluster of Excellence – “The Fuel Science Center,” concerted efforts are being made to develop novel e-fuels based on renewable energy and CO2 as carbon sources. Some of these fuels are highly susceptible to flash boiling at low-pressure conditions. In this study, the flash boiling phenomenon of these e-fuels is numerically investigated...
Citations
... In the elucidation of the procedure at temperatures of 700-900 • C (Carapellucci and Giordano, 2020) and pressures of 3-35 bar, fossil fuels are catalytically broken into H 2 and carbon monoxide (CO) in the presence of steam (H 2 O). Nickel (Ni) (Zohuri, 2018) and metal oxides made composites such as Ni/Al 2 O 3 (Yoo et al., 2015) or Ru/ZrO 2 (Kurzweil, 2016) are common heterogeneous catalysts. Methane is a popular hydrocarbon feedstock on an industrial scale. ...
... As a result, H 2 S must be eliminated from the hydrocarbon input. Hydro-treating or absorbing activated ZnO is two common methods for removing H 2 S (Zohuri, 2018). The steam reforming phase begins when the feed has been properly pre-treated. ...
Hydrogen (H2) is a possible energy transporter and feedstock for energy decarbonization, transportation, and chemical sectors while reducing global warming's consequences. The predominant commercial method for producing H2 today is steam methane reforming (SMR). However, there is still room for development in process intensification, energy optimization, and environmental concerns related to CO2 emissions. Reactors using metallic membranes (MRs) can handle both problems. Compared to traditional reactors, MRs operates at substantially lower pressures and temperatures. As a result, capital and operational costs may be significantly cheaper than traditional reactors. Furthermore, metallic membranes (MMs), particularly Pd and its alloys, naturally permit only H2 permeability, enabling the production of a stream with a purity of up to 99.999%. This review describes several methods for H2 production based on the energy sources utilized. SRM with CO2 capture and storage (CCUS), pyrolysis of methane, and water electrolysis are all investigated as process technologies. A debate based on a color code was also created to classify the purity of H2 generation. Although producing H2 using fossil fuels is presently the least expensive method, green H2 generation has the potential to become an affordable alternative in the future. From 2030 onward, green H2 is anticipated to be less costly than blue hydrogen. Green H2 is more expensive than fossil-based H2 since it uses more energy. Blue H2 has several tempting qualities, but the CCUS technology is pricey, and blue H2 contains carbon. At this time, almost 80–95% of CO2 can be stored and captured by the CCUS technology. Nanomaterials are becoming more significant in solving problems with H2 generation and storage. Sustainable nanoparticles, such as photocatalysts and bio-derived particles, have been emphasized for H2 synthesis. New directions in H2 synthesis and nanomaterials for H2 storage have also been discussed. Further, an overview of the H2 value chain is provided at the end, emphasizing the financial implications and outlook for 2050, i.e., carbon-free H2 and zero-emission H2.
... Cryogenic hydrogen (referred as liquid hydrogen; LH 2 ) requires cryogenic storage (− 253 • C; 20K) to maintain hydrogen in a liquid form [314]. This is due to hydrogen's high specific volume at standard atmospheric pressure and temperature. ...
Climate neutrality is becoming a core long-term competitiveness asset within the aviation industry, as demonstrated by the several innovations and targets set within that sector, prior to and especially after the COVID-19 crisis. Ambitious timelines are set, involving important investment decisions to be taken in a 5-years horizon time. Here, we provide an in-depth review of alternative technologies for sustainable aviation revealed to date, which we classified into four main categories, namely i) biofuels, ii) electrofuels, iii) electric (battery-based), and iv) hydrogen aviation. Nine biofuel and nine electrofuel pathways were reviewed, for which we supply the detailed process flow picturing all input, output, and co-products generated. The market uptake and use of these co-products was also investigated, along with the overall international regulations and targets for future aviation. As most of the inventoried pathways require hydrogen, we further reviewed six existing and emerging carbon-free hydrogen production technologies. Our review also details the five key battery technologies available (lithium-ion, advanced lithium-ion, solid-state battery, lithium-sulfur, lithium-air) for aviation. A semi-quantitative ranking covering environmental-, economic-, and technological performance indicators has been established to guide the selection of promising routes. The possible configuration schemes for electric propulsion systems are documented and classified as: i) battery-based, ii) fuel cell-based and iii) turboelectric configurations. Our review studied these four categories of sustainable aviation systems as modular technologies, yet these still have to be used in a hybridized fashion with conventional fossil-based kerosene. This is among others due to an aromatics content below the standardized requirements for biofuels and electrofuels, to a too low energy storage capacity in the case of batteries, or a sub-optimal gas turbine engine in the case of cryogenic hydrogen. Yet, we found that the latter was the only available option, based on the current and emerging technologies reviewed, for long-range aviation completely decoupled of fossil-based hydrocarbon fuels. The various challenges and opportunities associated with all these technologies are summarized in this study.
... 63,117 In addition, fuel cells can re-electrify hydrogen at efficiency of roughly 50% 118 or, alternately burnt in combined cycle gas power plants with efficiency of 60%. 119,120 It is noted that hydrogen produced through electrolysis is demonstrating great promise as a cost-effective fuel option, with data from the International Energy Agency and the International Atomic Energy Agency predicting that hydrogen produced from wind will be less expensive than natural gas by 2030. 121,122 It should be emphasized that hydrogen energy storage has been proved in realworld initiatives outside of the laboratory. ...
Energy storage is an idea that dates back over two thousand years. Engineers, investors, and politicians are increasingly researching energy storage solutions in response to growing concerns about fossil fuels' environmental effects as well as the capacity and reliability of global power systems. Various energy storage technologies are explored in depth in this study, with a focus on their application to the energy storage of electric grids. Specific consideration is paid to the a few chosen technologies including flywheel energy storage, pumped hydro energy storage, compressed air energy storage, thermal energy storage in molten salt, hydrogen energy storage, battery energy storages, and capacitor and supercapator energy storage. Furthermore, this article delves into the concept of energy storage, focusing on a comprehensive examination of various deployments of these technologies around the world. Some of the barriers to commercial adoption of energy storage technologies, as well as the future, are covered in the article's conclusion.
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Hydrogen storage in general is an indispensable prerequisite for the introduction of a hydrogen energy-based infrastructure. In this respect, high-pressure metal hydride (MH) tank systems appear to be one of the most promising hydrogen storage techniques for automotive applications using proton exchange membrane (PEM) fuel cells. These systems bear the potential of achieving a beneficial compromise concerning the comparably large volumetric storage density, wide working temperature range, comparably low liberation of heat, and increased safety. The debatable term “unstable metal hydride” is used in the literature in reference to metal hydrides with high dissociation pressure at a comparably low temperature. Such compounds may help to improve the merits of high-pressure MH tank systems. Consequently, in the last few years, some materials for possible on-board applications in such tank systems have been developed. This review summarizes the state-of-the-art developments of these metal hydrides, mainly including intermetallic compounds and complex hydrides, and offers some guidelines for future developments. Since typical laboratory hydrogen uptake measurements are limited to 200 bar, a possible threshold for defining unstable hydrides could be a value of their equilibrium pressure of peq > 200 bar for T < 100 °C. However, these values would mark a technological future target and most current materials, and those reported in this review, do not fulfill these requirements and need to be seen as current stages of development toward the intended target. For each of the aforementioned categories in this review, special care is taken to not only cover the pioneering and classic research but also to portray the current status and latest advances. For intermetallic compounds, key aspects focus on the influence of partial substitution on the absorption/desorption plateau pressure, hydrogen storage capacity and hysteresis properties. For complex hydrides, the preparation procedures, thermodynamics and theoretical calculation are presented. In addition, challenges, perspectives, and development tendencies in this field are also discussed.
We present a new method for hydrogen production that combines photocatalysis and electrolysis in a cell. TiO2 was doped with Ni and nitrogen to form Ni-TiO2 and N-Ni-TiO2 photocatalysts. XRD, UV-Vis, and SEM techniques were used to characterize the resulting samples. The Ni-TiO2 and N-Ni-TiO2 samples had anatase structures with energy gaps of 2.77 eV and 2.03 eV, respectively. A 50-watt UV lamp with a wavelength of 254 nm was used as the photon source. Our results indicate that this method produces more hydrogen than the sum of hydrogen generated by separate electrolysis and photocatalysis methods. The N-Ni-TiO2 sample produced the highest yield of HHO gas among the Ni-TiO2 and TiO2 p.a samples. The underlying mechanisms responsible for this improvement, including the role of the Ni and nitrogen doping, are discussed and analyzed.
Hydrogen carriers are one of the keys to the success of using hydrogen as an energy vector. Indeed, sustainable hydrogen production exploits the excess of renewable energy sources, after which temporary storage is required. The conventional approaches to hydrogen storage and transport are compressed hydrogen (CH2) and liquefied hydrogen (LH2), which require severe operating conditions related to pressure (300–700 bar) and temperature (T < −252 °C), respectively. To overcome these issues, which have hindered market penetration, several alternatives have been proposed in the last few decades. In this review, the most promising hydrogen carriers (ammonia, methanol, liquid organic hydrogen carriers, and metal hydrides) have been considered, and the main stages of their supply chain (production, storage, transportation, H2 release, and their recyclability) have been described and critically analyzed, focusing on the latest results available in the literature, the highlighting of which is our current concern. The last section reviews recent techno-economic analyses to drive the selection of hydrogen carrier systems and the main constraints that must be considered. The analyzed results show how the selection of H2 carriers is a multiparametric function, and it depends on technological factors as well as international policies and regulations.
This review article aims to describe the main applications of gas hydrates in industrial processes and the related advantages and limitations. In particular, gas storage, energy storage, gas transportation, final disposal of greenhouse gases, desalination, wastewater treatments, food concentration, and other technologies are described in detail. Similarly, the benefits and disadvantages of the solutions, currently adopted to improve the process efficiency, are discussed in the text. A particular focus on the use of additives and their capability to intervene during the formation of hydrates and on the replacement process is provided. The second part of the article deals with the use of small-chain hydrocarbons as aid gases during formation, to improve the efficiency and the competitivity of hydrate-based processes. First, the thermodynamic properties of hydrates, containing only these compounds, are described. Then, based on a collection of experimental data available elsewhere in the literature, their effect on the hydrate formation process, when present in the mixture, is shown and detailed. Finally, direct and experimental applications of these gases during hydrate-based processes are described to definitively prove the possibility of solving, partially or completely, most of the main limiting problems for the diffusion of hydrate-based technologies.
