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Energy and the Environment
Published in Marc J. Assael, Geoffrey C. Maitland, Thomas Maskow, Urs von Stockar, William A. Wakeham, Stefan Will, Commonly Asked Questions in Thermodynamics, 2022
Marc J. Assael, Geoffrey C. Maitland, Thomas Maskow, Urs von Stockar, William A. Wakeham, Stefan Will
If we used a SOFC hydrogen fuel cell working at an efficiency of 80% (see Question 7.2.3.2) to power this typical house for a month, then with a liquid hydrogen energy density of 6 MJ/dm3, the volume of the hydrogen storage tank required would be 0.2 m3. So the tank would be 200 L, which is roughly one barrel of oil, similar in size to a domestic oven. A promising option that mitigates the safety risk of storing large volumes of hydrogen is the use of liquid organic hydrogen carriers (LOHC) with an energy density similar to those of liquid hydrogen (Haupt and Müller 2017). An alternative to batteries and fuel cells for stand-alone power generation is solar energy. To power our typical house consuming 350 kWh over a month requires 350 × 3.6 × 106/(30 × 24 × 3,600) W = 486 W, which for a typical 2020 PV Panel from Table 7.7 will require a roof area of 486/20 m2 = 24 m2, which is comparable with the south-facing roof area of a typical house. In many climates, the best use of the solar electricity is to recharge the batteries to provide low-carbon renewable electricity round the clock.
Introduction
Published in Shitanshu Sapre, Kapil Pareek, Rupesh Rohan, Compressed Hydrogen in Fuel Cell Vehicles, 2022
Shitanshu Sapre, Kapil Pareek, Rupesh Rohan
Liquid organic hydrogen carriers (LOHCs) are organic compounds used for storing hydrogen via a chemical reaction. LOHCs are unsaturated compounds with double or triple carbon that take the hydrogen during hydrogenation. The hydrogenation is an exothermic reaction carried out at pressure and temperature of 30–50 bar and 150–200°C in the presence of a catalyst, respectively [54,55]. The storage of hydrogen takes place by reversible hydrogenation and dehydrogenation of carbon double bonds. Hydrogenation is an exothermic process at high pressure and temperature and dehydrogenation is an endothermic process at atmospheric pressure. Hydrogenation and dehydrogenation are catalyst-based processes where catalysts play a significant role in conducting the reaction. Figure 1.9 presents the hydrogenation and dihydrogen process of hydrogen in typical LOHC compounds with heat generation and absorption during the process [56].
Toward modeling of solubility of carbon dioxide, methane, and nitrogen in liquid dibenzyl toluene (LDT) using rigorous technique
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
This decade due to the huge application of renewable sources of energy, hydrogen storage in the liquid organic hydrogen carriers (LOHCs) and corresponded research area attract rising attention (Zou et al. 2019). In this storage method, aromatic compounds such as dibenzyl toluene convert into saturate compounds and absorb hydrogen from the hydrogen stream at the specified pressure and temperature. In other words, hydrogen storage in the liquid dibenzyl toluene occurs using the chemical conversion of dibenzyl toluene to saturated hydrocarbon. However, the chemical conversion of the mentioned LOHC depends on the concentration of soluble hydrogen in the LOHC. In other words, the physical dissolution of hydrogen in the liquid stream plays an important role in the hydrogen storage in LOHC materials (Kim et al. 2018; Modisha et al. 2019; Niermann et al. 2019a; Palkovits, Artz, and Chen 2018; Søgaard et al. 2017).
Critical examination of equilibrium constants proposed for the methylcyclohexane dehydrogenation to toluene
Published in Chemical Engineering Communications, 2019
Among the various methods used for hydrogen storage, Liquid Organic Hydrogen Carrier (LOHC) based systems, which involves a catalytic cycle consisting of hydrogenation of a suitable unsaturated organic compound and its dehydrogenation, have gained considerable attention (Preuster et al., 2017). One of the first LOHC based systems; the dehydrogenation of methyl-cyclohexane (MCH) to toluene (TOL) has been extensively studied for seasonal hydrogen energy storage for both mobile (Taube and Taube, 1981; Grünenfelder and Schucan, 1989; Klvana et al., 1991; Usman, 2010; Usman and Cresswell, 2013) and stationary (Winter et al., 1990) systems. MCH acts as a liquid H2 carrier facilitating storage and transportation of H2 gas. More recently, Chiyoda Corporation constructed a demonstration plant to dehydrogenate MCH with a capacity of 50 N cubic meters H2 per hour (Chiyoda Corporation, 2014). Crucial for the efficiency of this methylcyclohexane-toluene-hydrogen (MTH) system are the kinetics and equilibrium conversions achievable in the dehydrogenation:
Review on the characteristics of existing hydrogen energy storage technologies
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
S.J. Wang, Z.Y. Zhang, Y. Tan, K.X. Liang, S.H. Zhang
Liquid organic hydrogen storage uses the reversible hydrogenation/dehydrogenation reaction of unsaturated-saturated pair of liquid organic hydrogen carriers (LOHCs) to store hydrogen, which has the advantages of high hydrogen storage density, good reversibility, and recyclable hydrogen carrier. Moreover, LOHCs can be efficiently stored and transported under normal temperatures and pressure by using the existing fossil fuel infrastructure (Bourane et al. 2016; Jiang et al. 2014). The working process of LOHCs includes catalytic hydrogenation, storage of hydrogen carrier, the release of hydrogen, return of dehydrogenated hydrogen carrier to its original place, and catalytic hydrogenation again. The whole process is a complete closed cycle, which is suitable for long-distance and large-scale transportation (Abdin et al. 2021; Niermann et al. 2021). Olefins, alkynes, aromatics, and some substances that can undergo dehydrogenation coupling esterification have the potential to become LOHCs in theory. Among them, about 5 w.t.% reversible hydrogen storage capacity can be obtained by using the dehydrogenative coupling reaction of methanol or ethylene glycol. These are cheap and easily available organic substances. However, this reaction is not conducive to the efficient storage of hydrogen. The reason is that there are many problems such as a large number of intermediate by-products, long reaction time, complex reaction process, and large difference between hydrogenation and dehydrogenation reaction conditions (Shao et al. 2020; Zou et al. 2019). For other substances, compared with alkenes and alkynes, aromatic hydrocarbons are more suitable as hydrogen carriers in terms of hydrogen storage capacity and reaction reversibility (Ananthachar and Duffy 2005). Nowadays, the widely studied aromatic LOHCs include benzene-cyclohexane (Ping, Xu, and Wu 2015; Wang et al. 2016), toluene-methylcyclohexane (Boufaden et al. 2015; Samimi, Kabiri, and Rahimpour 2014; Yolcular and Olgun 2008), naphthalene-decahydronaphthalene (Feiner et al. 2014; Ren et al. 2013; Shono et al. 2006), biphenyl-based eutectic mixture (Kwak et al. 2021), etc. These substances have high hydrogen storage capacity, good reversibility, low price and toxicity. The reversible mass hydrogen storage density of these organics is 6.1 ~ 7.3 w.t.%, and they can be transported under near-ambient conditions. However, these liquid organic materials require high temperatures and pressures (200 ~ 350°C, 7 ~ 50 MPa) for hydrogenation/dehydrogenation, which restricts their large-scale application (Biniwale et al. 2008). Therefore, it is necessary to choose alternatives with milder reaction conditions for hydrogenation/dehydrogenation.