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Published in Eduardo Rincón-Mejía, Alejandro de las Heras, Sustainable Energy Technologies, 2017
Christian Sattler, Anis Houaijia, Martin Roeb
The most interesting representative of the indirect (electrochemical) processes is high-temperature electrolysis, which is more efficient than ambient temperature electrolysis, especially from an economic point of view due to the fact that a part of the total energy demand is supplied as heat, which is cheaper to generate than electricity [3]. The leading technologies in the field of high-temperature electrolysis are the Solid Oxide Electrolysis (SOE) and the Molten Carbonate Electrolysis (MCE) [4]. The focus of this chapter will be solar high-temperature electrolysis, including the SOE and MCE technologies and solar thermochemical H2O and CO2 splitting. Other processes, solar steam methane reforming, solar gasification, and solar cracking of natural gas, will not be a part of the analysis within this chapter. The concentration of solar irradiation can be carried out using many technologies, well known as concentrating solar power (CSP) technologies. Concentrating technologies for scale-up plants are available in four common forms, namely, parabolic trough, linear Fresnel, solar dish, and solar power tower.
Alternative Fuel for Transportation
Published in Atul Sharma, Amritanshu Shukla, Renu Singh, Low Carbon Energy Supply Technologies and Systems, 2020
Sumit Lonkar, Prashant Baredar
The PEM electrolyzer is mainly a polymer electrolyte membrane fuel cell operating in the reverse condition. At present, the PEM electrolyzer has higher electricity consumption than the alkaline-based electrolyzer; however, the potential for increased energy efficiency in the long term is better. High-temperature electrolysis also offers higher efficiency. At higher temperature, energy consumption increases, and electricity consumption decreases. Hence, high-temperature electrolysis (800°C–1000°C) may offer a good energy balance if high-temperature waste heat is available from other processes [13].
2 Conversion with SOCs 1
Published in Yun Zheng, Bo Yu, Jianchen Wang, Jiujun Zhang, Carbon Dioxide Reduction through Advanced Conversion and Utilization Technologies, 2019
Yun Zheng, Bo Yu, Jianchen Wang, Jiujun Zhang
Figure 6.2 illustrates the energy demands of the two electrolysis reactions for H2O or CO2.15,17,18 It is well known that enthalpy is made up of a Gibbs free energy and an entropy term in accordance with Equation (6.5). As indicated in Figure 6.2, ΔH, ΔG, and TΔS are the total energy demand, electrical energy demand, and heat demand, respectively. With the increase in temperature, the total energy demand is almost invariant, but the increasing heat demand and the decreasing electrical energy demand are shown for both H2O splitting and CO2 splitting, which is due to positive entropy change (ΔS > 0). Compared to low- or intermediate-temperature electrolysis, high-temperature electrolysis can use both electricity and heat effectively (the efficiency of electricity-to-syngas is up to about 100%), and can achieve high reaction rates, which in turn results in reduced cell internal resistance and greater productivity at the same voltage.15 In other words, as for H2O or CO2 electrolysis, from a thermodynamic viewpoint, high-temperature operation is the better choice for both efficiency and cost.16 With respect to the relationship between ΔH, ΔG, and ΔS of H2O/CO2 co-electrolysis, similar trends can be seen in Figure 6.2b. The ΔH is also insensitive to the increasing temperature, which includes ΔG and TΔS. Thus, as a complement, the decrease of electrical energy demand is almost equal to the increase of heat demand, with temperature increasing. The ΔG is still more than 300 kJ/mol at 1000°C, which definitely restricts the competitiveness of co-electrolysis. However, the competitiveness can be increased using the industrial waste heat or the electricity from renewable energy.17
Review of green hydrogen technologies application in maritime transport
Published in International Journal of Green Energy, 2023
Doha Elrhoul, Manuel Romero Gómez, Manuel Naveiro
Unlike low-temperature electrolysis, high-temperature electrolysis consists of a solid oxide electrolysis cell (SOEC) using superheated steam as feedstock instead of water (d’Amore-Domenech, Santiago, and Leo 2020; Nikolaidis and Poullikkas 2017). Operating temperatures vary between 600 and 1000°C resulting in a high energy efficiency compared to other electrolysis technologies previously mentioned (Dincer and Acar 2018; d’Amore-Domenech, Santiago, and Leo 2020; Nicita et al. 2020). SOECs are able to generate electrolytic hydrogen on a large-scale (Dincer and Zamfirescu 2016b). The main challenge of using this technology at sea is the difficulty of finding high-temperature external sources to maintain a permanent operating temperature, which affects the system durability as well as the plant dynamics (Dincer and Acar 2018; d’Amore-Domenech, Santiago, and Leo 2020).
CFD analysis for optimizing superheater components for high temperature steam production for use in an SOEC
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Yunji Kim, Hyunseung Byun, SeongRyong Park, Chongpyo Cho, Youngsoon Baek
Figure 2 indicates that the total energy demand is constant at various temperatures. As the temperature increases, the electrical energy demand decreases and the thermal energy demand increases(Chen, Ai, and Jiang 2012; Dutta 1990; Zhu et al. 2012). Therefore, high-temperature SOECs are advantageous as they provide more opportunities to utilize industrial waste heat to produce hydrogen(Abdullah and Dincer 2016; Toklu et al. 2016; Yildiz and Kazimi 2004). If the water can be converted into steam by waste heat from other processes, it is more efficient for high-temperature electrolysis to convert steam directly owing to the more favorable thermodynamic and electrochemical kinetic conditions for the reaction.