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Toward a liquid hydrogen fuel economy
Abstract
http://deepblue.lib.umich.edu/bitstream/2027.42/5800/5/bac5758.0001.001.pdf http://deepblue.lib.umich.edu/bitstream/2027.42/5800/4/bac5758.0001.001.txt
... A diagram of the hydrogen production methods is shown in Figure 3. Although industrial hydrogen can be obtained from water, hydrocarbons and even biomass, currently, as much as 48% of its production is based on methane-reforming using steam, 30% comes from refining crude oil, 18% is released during coal transformations, e.g., in the Haber-Bosch method, and only 4% is the product of water electrolysis [29][30][31][32][33]. Its importance as an energy source grows year by year. ...
This manuscript shows the use of natural polysaccharides such as starch and cellulose as a carbon source for fuel cells. To achieve this, two innovative methods of obtaining hydrogen have been shown: by adsorption and by enzyme. The carbonization path of the material results in excellent sorption properties and allows gas with high efficiency to be obtained. The enzymatic method for the degradation of the compound is more expensive because specific enzymes (such as laccase, tyrosinase) must be used, but it allows greater control of the properties of the obtained material. A scientific novelty is the use of natural raw materials, the use of which increases the biodegradability of the electrochemical system and also reduces the cost of raw materials and increases the range of their acquisition. Energy should be generated where it is used. Another goal is decentralization, and thanks to the proposed solutions, hydrogen cells represent an innovative alternative to today’s energy giants—also for independent power supply to households. The proposed harvesting paths are intended to drive rail vehicles in order to reduce emissions and secondary pollution of the environment. The goals of both methods were easy recycling, high efficiency, increased environmental friendliness, low cost and a short hydrogen production path.
... In 1874 Jules Verne in The Mysterious Land envisages 'water will one day be employed as fuel, that hydrogen and oxygen of which it is constituted will be used.' In 1970, John Bockris and Lawrence W. Jones hypothesize a 'hydrogen economy' [1,2]. Fast forward to 2013, a 2 MW power-to-gas installation in Falkenhagen pumping 360 cc/hr hydrogen into natural gas grid [3], and in 2017, the 'Hydrogen Council' formed for an expedited hydrogen economy [4]. ...
Adding renewable hydrogen into natural gas pipeline would bring down the net gas C/H ratio and hence the CO2 emissions. Also, it can help stabilize electric grids and maximize the renewable output of intermittent energy sources (solar, wind, etc.) via power-to-gas pathway. However, hydrogen differs in its chemical and physical characteristics (flammability range, flame speed, density, adiabatic flame temperature, energy content, etc.) than natural gas. Before transitioning to hydrogen admixing into pipelines, a general agreement on maximum hydrogen tolerance pertaining to end use (residential appliances) operation needs to be established. Focusing on the combustion performance of two representative models of storage water heaters (conventional and low-NOx) in California, this research addresses how much H2 content in natural gas can be tolerated without loss of critical performance parameters with reliable operation. Characteristics like flashback, ignition delay, flame structure, and emissions (NOx, NO, CO, CO2, UHC, and NH3) at different concentrations of H2 admixed with natural gas is investigated. The present study shows <10% H2 can be added to natural gas without any loss of efficiency for both the low-NOx and conventional storage water heater. This work also aims to provide a brief review of burner configuration and emission regulation pertaining to water heating owing to a gap in the literature.
... The limited availability of fossil fuels as well as the impending climate change, compel humanity to focus on sustainable alternative energy sources. As early as in the 1970s Lawrence Jones predicted that the use of hydrogen is technically and economically feasible and will become inevitable in the future [3]. Produced by renewable energy sources, hydrogen becomes an ideal energy carrier. ...
In this thesis the transfer hydrogenation of different substrates with the LOHC compound perhydro-dibenzyltoluene (H18 DBT) was investigated. The applied substrates included aromatic, olefinic and carbonylic compounds. The reactions were carried out to identify suitable catalysts and reaction conditions for rapid and highly selective transformations. Toluene was used as aromatic model compound. A catalyst variation, including Pt/C, Pd/C, Rh/C, Ru/C, Ni/SiOx, Raney nickel and Au/AlOx, was carried out at 270 °C. It was found that only platinum, palladium and rhodium were active for this kind of reaction. Furthermore, a temperature variation was carried out with platinum and palladium catalysts. The temperature was varied between 210 °C and 290 °C. Even at the lowest temperature, where a sole dehydrogenation of the carrier is hardly possible, a significant activity was observed for both catalysts. The activity was always higher when platinum was used as active metal. It was further found that the amount of the hydrogen carrier has a minor influence as long as it is used in excess (threefold hydrogen excess). When stoichiometric ratios of the educts were used, an equilibrium conversion of toluene of 62 % was reached, which indicates a slight exothermicity of the reaction. The transfer hydrogenation proceeded without any noticeable side reactions or the formation of partly hydrogenated compounds. In a next set of experiments olefinic substrates were used for the transfer hydrogenation reaction. To avoid analytical difficulties due to a fast isomerisation of the double bond of linear alkenes, (Z) cyclooctene was used as substrate at temperatures between 210 °C and 290 °C. It was found, however, that the molecule is not stable under the applied conditions and a vast amount of side reactions occurred. Consequently, 1 octene was used for the transfer hydrogenation, despite the analytical problems. The same catalysts were applied as mentioned before and again platinum- and palladium-based catalysts were found most active for the reaction. A fast isomerisation of the double bond occurred, which did not seem to have an influence on the transfer hydrogenation activity. The formation of side products was far less pronounced compared to (Z) cyclooctene, however, a small amount of mostly aromatic C8 molecules formed during the reaction. Furthermore, with Pt/C the release of hydrogen was observed, when the substrate was fully consumed. With palladium as active metal, hydrogen was released to a significant extent during the entire reaction time. Platinum, in contrast, has a high selectivity towards the transfer hydrogenation and the hydrogen evolution only occurred when the substrate was fully consumed. At last the transfer hydrogenation of oxygen containing carbonyl compounds was studied. The use of aldehydes proved difficult as they are very reactive under the applied reaction conditions. With hexanal as substrate the decarbonylation was very pronounced, which led to the formation of the catalyst poison CO. Furthermore, the aldol condensation occurred. To avoid these side reactions, which are due to the very unstable –COH group, ketones were used for the transfer hydrogenation reaction. Acetone is a very stable molecule and the transfer hydrogenation with Pt/C and Pd/C proceeded without any noticeable side reactions under comparatively mild temperatures (150 °C with Pt/C). The reaction is, however, strongly limited by a reaction equilibrium and reaction conditions needed to be optimised. Furthermore, the release of hydrogen was observed with both catalyst. It could be shown that the gas was not released due to dehydrogenation of H18 DBT but rather through dehydrogenation of the produced isopropanol. The dehydrogenation is in general undesired for transfer hydrogenation reactions, but it opens a new dehydrogenation pathway for H18 DBT under significantly milder reaction conditions. The transfer hydrogenation was furthermore carried out with cyclohexanone as substrate. The reaction was, however, not as straightforward as with acetone due to the formation of side products. Mainly phenol and diethylethers were formed to a high extent. For the transfer hydrogenation with H18 DBT as hydrogen donor very stable substrates have to be used, as the reaction temperatures have to be at least 150 °C for Pt/C and 190 °C for Pd/C. The highest activity was always observed with Pt/C no matter which substrate was used. The activity with Pd/C was lower compared to Pt/C and a minor activity was usually observed with Rh/C. Other applied catalyst did not yield any hydrogenated reaction products. To gain a deeper insight into the reaction mechanism, a deuterium labelled hydrogen carrier was used for transfer hydrogenation reactions. To simplify the analytical evaluation diphenylmethane (DPM) was used as donor molecule, as it is chemically similar to H0 DBT and no structural isomers exist. A method for the complete deuteration of DPM was developed. It was found that palladium is more active for the deuteration of the methyl bridge, whereas platinum is more active for the deuteration of aromatic positions. Furthermore, all catalysts are more active when carbon is used as support instead of alumina. For the complete deuteration of DPM Pt/C proved to be the best catalyst. At higher temperatures and with a higher deuterium excess the H/D exchange proceeds significantly faster. The deuteration was therefore carried out at 150 °C for at least 24 h and with a deuterium excess of 20. H0 DPM and D0 DPM were subsequently loaded with either hydrogen or deuterium gas. The hydrogenation proceeded faster compared to the deuterogenation, which might be explained by a higher bond strength between deuterium atoms. Similar results were achieved for the dehydrogenation of H12 DPM and D12 DPM. It was again found that the reaction with hydrogen containing compounds showed a higher reaction rate. The H/D exchange was investigated between both loaded and both unloaded DPM species. With Pd/C and Pt/C a fast isotope exchange was observed between the unloaded DPM species under the applied reaction conditions. The H/D exchange was more pronounced between the loaded species, when Pt/C was used, even though palladium is commonly known to favour the isotope exchange of aliphatic positions. Finally the transfer hydrogenation of acetone h6 or acetone d6 with either H12 DPM or D12 DPM was investigated. It was found for all experiments that an H/D exchange between donor and acceptor molecule took place. A detailed retracement of the course of the reaction was therefore not possible. It is assumed that the catalytic surface gets covered with hydrogen/deuterium atoms before either the reduction of acetone or an isotope exchange occurs. With platinum a higher selectivity towards the transfer hydrogenation was shown, whereas with palladium a higher H/D exchange activity was observed. To gain more insight into the reaction mechanism further surface science studies are necessary. It could be shown in this thesis that platinum on carbon is by far the most active and selective catalyst for the transfer hydrogenation with H18 DBT as hydrogen donor molecule. This work has opened up the interesting research field of using LOHC-bound hydrogen for preparative hydrogenation reactions. This field promises further developments for applying the chemical hydrogen storage and transport vector H18-DBT directly for synthetic purposes. Following this work, these options are currently under even broader investigation at the Institute of Chemical reaction engineering in Erlangen.
... It was first mentioned as a proposition in a technical report named "Toward a liquid hydrogen fuel economy" by Lawrence W. Jones in 1970, where it says that fossil fuels are finite, and their reserves will last for a short time. Therefore, another energy vector is needed, as a proposition is hydrogen as it is widely abundant in our planet (Jones 1970). The central thesis is that a new set of economy and energy security should be created, basically because of the pollutant hazard of carbon-based fuels. ...
Now more than ever we must ensure energy efficiency. There are a lot of technologies environmentally friendly and renewable, but we need to focus on the security to supply it. Unfortunately, renewables are far less secure, as most of them only produce very intense energy for a small amount of time or they are far away from where it is needed. Renewables at this stage-point are more costly to bring them into the grid than oil/coal technology. Between several renewable energies, there is one that sounds to be consistent with promoting energy security and clean energy: hydrogen. Hydrogen is readily available, convenient to transform from different primary energy sources and has the highest energy content of any common fuel by weight. Some of their downsides are not cost-effective to store, volatile and metal embrittlement inducer.
Nevertheless, this should not push this energy storage element aside. Gasoline, diesel and
natural gas are also flammable and require chord storage units with other element inducers
characteristics. These hydrocarbon fuels also have their particular expenses, damages and
wear and tear characteristics that have been corrected due to a massive infrastructure
implemented.
The most pressing issue in the world today is to change the idea on the mind of consumers
and stakeholders on the high cost and low efficiency of hydrogen and the great potential to
back sustainable energy and the economy of countries through the already implemented
infrastructure. What we need at this point is a policy that can make hydrogen economy an
easier stage to follow into the energy-producing market.
This chapter sets the scene for the potential role of water electrolysis in the global future energy system. It introduces hydrogen, water electrolysis, and other hydrogen production routes and discusses historic drivers for hydrogen. It then identifies climate change mitigation as the key motivation for contemporary hydrogen developments. This chapter also provides a review of the potential future role of hydrogen and water electrolysis in publicly available global energy system studies. It shows that in order to reach net-zero CO2 emissions, between 1.7 and 13 Terawatt of water electrolysis capacity could be needed by 2050 worldwide. This would require the water electrolyzer industry to scale up manufacturing to a hundred or more gigawatts per year by 2040. This chapter closes with an outlook of water electrolysis deployments planned at the beginning of the 2020s.
Die Dehydrierung von Perhydro Dibenzyltoluol (H18-DBT) in einem Festbettrohrreaktor kann als Stand der Technik angesehen werden. Allerdings hat die kontinuierliche Dehydrierung von H18-DBT noch erhebliches Verbesserungspotential. In dieser Arbeit wurde die Verbesserung der Handhabbarkeit und die Steigerung der Produktivität durch die Modifizierung des LOHCs, die Verbesserung der Stabilität des Katalysators und die Entwicklung alternativer Reaktorkonzepte zur Absenkung der Reaktionstemperatur und Steigerung der Produktivität untersucht. Im Rahmen dieser Arbeit wurde der Einsatz von Mischungen aus Perhydro-Benzyltoluol (H12-BT) und H18-DBT in der Dehydrierung untersucht. Mit steigendem Anteil an H12-BT in H18-DBT sinkt die Viskosität und steigt der Dampfdruck der Mischung. So wird die Handhabbarkeit mit steigendem Anteil an H12-BT verbessert, jedoch reduziert sich mit steigendem Anteil an H12-BT die maximale Temperatur einer Flüssigphasen-Dehydrierung bei atmosphärischem Druck. Weiterhin wurde der Einfluss des Anteils an H12-BT auf die Wasserstofffreisetzung in der Batch-Dehydrierung betrachtet. Bei konstanter Temperatur erhöht sich die Produktivität mit steigendem Anteil an H12-BT. Ein weiterer Schwerpunkt der Arbeit lag in der Untersuchung der kontinuierlichen Dehydrierung von H18-DBT in einem Festbettreaktor mit rechteckigem Querschnitt. Durch die Verwendung eines rechteckigen Querschnitts kann die Wasserstofffreisetzungsrate im Gegensatz zum kreisförmigen Querschnitt gesteigert werden. Zusätzlich wurde in diesem Reaktor die Stabilität des Katalysators über mehrere Abkühl- und Aufheizvorgänge untersucht. Außerdem wurde der Reaktor hinsichtlich seines Verweilzeitverhaltens charakterisiert und ein Modell entwickelt, um abhängig von der Temperatur, dem Druck und dem zugeführten Volumenstrom an H18-DBT den freigesetzten Wasserstoffvolumenstrom ermitteln zu können. Abschließend wird das Reaktorkonzept der Reaktivrektifikation evaluiert. In diesem Reaktorkonzept entspricht die Prozesstemperatur aufgrund der integrierten Rektifikation der Siedetemperatur des LOHCs. Als LOHC wird in diesem Reaktorkonzept H12-BT verwendet, da bei H12-BT der Siedepunkt bei atmosphärischem Druck unter der erlaubten Verwendungstemperatur im Gegensatz zum technisch etablierten LOHC H18-DBT liegt. Zunächst wurde die Produktinhibierung in der Flüssigphasen-Dehydrierung von H12-BT nachgewiesen. Batch-Versuche deuten darauf hin, dass in einem Reaktivrektifikationskonzept die Produktinhibierung reduziert werden kann. Außerdem wurde der Einfluss des Drucks auf die Sumpf- und Katalysatortemperatur untersucht. Durch die Reduzierung des Drucks reduziert sich die Sumpf- und Katalysatortemperatur. Dadurch scheint die Einbringung der Dehydrierwärme durch Wärmeintegration mit einer HT-PEMFC möglich. So kann der Wirkungsgrad von im LOHC gespeicherten Wasserstoff zu Strom gesteigert werden. Aufgrund der niedrigeren Reaktionstemperatur reduziert sich die Wasserstofffreisetzung mit sinkendem Druck. Aufbauend auf den Erkenntnissen aus den Batch-Versuchen wurde ein kontinuierlicher Versuchsaufbau im Labormaßstab entwickelt. Es konnte eine stabile kontinuierliche Dehydrierung bei atmosphärischem Druck und Unterdruck gezeigt werden. Zusätzlich konnte eine Intensivierung der Dehydrierung durch das Reaktorkonzept der Reaktivrektifikation im Vergleich zur klassischen Flüssigphasen-Dehydrierung im Festbettreaktor gezeigt werden.
Hydrogen is currently enjoying a renewed and widespread momentum in the energy market. In the last years, demand for hydrogen has substantially increased worldwide, with several countries developing hydrogen national strategies, and private companies investing in the development of hydrogen related projects. Green hydrogen’s environmental sustainability and versatility contribute to its representation as the holy grail of decarbonisation. This working paper challenges this definition, by analysing the historical process which contributed to hydrogen’s rise, showing the current uses of hydrogen and the major obstacles to the implementation of a green hydrogen economy, and assessing the geopolitical implications of a future hydrogen society. Particularly, the paper shows that the hydrogen economy is still far from becoming reality. Even though investments in green hydrogen technologies and projects have increased over the last decade, there still remains a high number of unresolved issues, relating to technical challenges and geopolitical implications. Nonetheless, a clean hydrogen economy offers promising opportunities not only to fight climate change, but also to redraw geopolitical relations between states. The energy transition is already taking place, with renewable energies gradually eroding the global energy system based on fossil fuels. A global transformation, set in motion by the need to decarbonise the energy system, will have the potential to redraw international alliances and conflicts. In this context, hydrogen may play a crucial role. By 2050, hydrogen could indeed meet up to 24% of the world’s energy needs, thus highly influencing the geopolitical landscape. In this regard, the choice over which pathway to take for the creation of hydrogen value chains will have a huge geopolitical impact, resulting in new dependencies and rivalries between states. Conclusively, if national governments are willing to spur the emergence of a green hydrogen economy, they should heavily invest in research and development, encourage the development of a clean hydrogen value chain, and promote common international standards. Moreover, they should also take into account hydrogen’s geopolitical implications. If the hydrogen economy is well-managed, it could indeed increase energy security, diversify the economy, and strengthen partnerships with third countries.
Residential water heating is the single most significant end-use for natural gas in California-- more than half of the net energy consumption for a typical Californian household goes into fulfilling hot water demands. Aided by cost-effective natural gas available in the state, about 90% of water heaters are natural gas-fueled storage tank systems, with 40-50-gallon capacity. In order to decarbonize residential spaces, a strong focus on water heating is essential.
This research focuses on the impact of renewable fuel (biogas and renewable hydrogen) injection into pipelines for gas-fired storage water heaters. Two representative models of storage water heaters were chosen for experiments. First, a conventional storage unit; meeting 40 ng/J NOx emission requirement, second, a low-NOx storage water heater meeting 10 ng/J NOx emission requirement. This research answers how much CO2/H2 content in natural gas can be tolerated without loss of critical performance parameters with reliable operation.
Characteristics like ignition delay, flashback, blow-off, ignition, flame structure, and emissions (NO2, N2O, NO, CO, CO2, UHC, and NH3) at different concentrations of CO2/H2 mixed with natural gas is investigated. The study found less than 10% H2 tolerance for both the water heaters, less than 15% CO2 tolerance for low-NOx water heater and no CO2 tolerance for the conventional storage model. NOx/NO emission reduction is achieved for both the water heaters with increased CO2/H2 and a simultaneous CO/UHC increase is observed. Further, both the water heater emission and stability performance were simulated using a chemical reactor network (CRN).
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