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Fundamentals of Water Electrolysis
Published in Lei Zhang, Hongbin Zhao, David P. Wilkinson, Xueliang Sun, Jiujun Zhang, Electrochemical Water Electrolysis, 2020
Xiaoxia Yan, Rida Javed, Yanmei Gong, Daixin Ye, Hongbin Zhao
Solid oxide electrolysis was developed in the 1970s by General Electric and Brookhaven National Laboratory, followed by Dornier in Germany. In recent years, a solid oxide electrolyzer cell (SOEC) is composed of an anode and cathode separated by an O2− conducting electrolyte. Yttria-stabilized zirconia, Ni-yttria-stabilized zirconia, and lanthanum strontium manganite-yttria-stabilized zirconia are generally used as the electrolyte, anode, and cathode respectively. The reactions at the electrodes are24: H2O+2e−→H2+2O2−(Cathode)O2−→(1/2)O2+2e−(Anode)
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
As identified, high temperature CO2/H2O co-electrolysis (HTCE) using SOECs has greater potential for future cost reductions and efficiency improvements6 as it is more energy efficient than those of the two separate electrolysis processes in terms of both lower energy consumption and fewer electrolysis steps, as well as the fact that it requires only one necessary reactor to operate.7–11 The syngas (H2 + CO) that is produced is an effective energy carrier beyond electricity that can be used for large-scale energy storage. It can also be further processed to generate chemicals or liquid fuels via Fischere-Tropsch (F-T) synthesis.12 Additionally, the fuels produced can be used to generate power within the same SOEC device in the reversible mode.13 Considering the above, SOEC technology can provide an attractive route to reduce CO2 emissions, enable scalable energy storage capabilities, and facilitate the integration of renewable energies into the electric grid. Minh and Mogensen13believed that SOECs should have the following attractive features: (1) compatibility (environmentally compatible with reduced CO2 emissions), (2) flexibility (fuel flexible and suitable for integration with various energy sources, especially sustainable energies), (3) capability (can be used for different functions), (4) adaptability (suitable for a variety of applications or different local energy needs), and (5) affordability (competitiveness in cost).
Hydrogen
Published in Arumugam S. Ramadhas, Alternative Fuels for Transportation, 2016
Fernando Ortenzi, Giovanni Pede, Arumugam Sakunthalai Ramadhas
Electrolysis of water can produce very high purity hydrogen with high efficiency. Electrical current passes through two electrodes to separate water into hydrogen and oxygen. Commercial low temperature electrolyzers have system efficiencies of 56–73%. Solid oxide electrolysis cells (SOEC) electroly-sers are more efficient. The SOEC technology has challenges with corrosion, seals, thermal cycling, and chrome migration. Electrolyzers are not only capable of producing high purity hydrogen, but recently, high-pressure units. H2O→H2+12O2.
Grey, blue, and green hydrogen: A comprehensive review of production methods and prospects for zero-emission energy
Published in International Journal of Green Energy, 2023
Priyanka Saha, Faysal Ahamed Akash, Shaik Muntasir Shovon, Minhaj Uddin Monir, Mohammad Tofayal Ahmed, Mohammad Forrukh Hossain Khan, Shaheen M. Sarkar, Md. Kamrul Islam, Md. Mehedi Hasan, Dai-Viet N. Vo, Azrina Abd Aziz, Md. Jafar Hossain, Rafica Akter
On the other side, PEM technology has been in use from 1960 and appropriate for city parts because of its small size of the system. In addition, PEMs are more efficient and responsive, which makes them appropriate for capturing excess supply of renewable energy (Holm et al. 2021). High-pressure PEMs can deliver hydrogen in pressurized form, enhancing overall effectiveness. Nevertheless, because the electrode catalysts and membrane materials used in this method are costly, it has significant capital expenditures. The SOEC technology involves solid electrolytes and uses the separation of water to produce hydrogen and oxygen. Oxygen penetrates the membrane and is produced at the anode donating electrons (Ratnakar et al. 2021). SOEC technology has higher efficiencies ranging from 74% to 81% and is commercially available at 150 kW (Furat, Anda, and Shafiullah 2020; Ratnakar et al. 2021).
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
Recently, solid oxide electrolyzer cells (SOECs) have attracted considerable attention. An SOEC is a reversible hydroelectric fuel cell system that produces electricity from renewable energy sources, including solar and wind energy and waste heat, and uses surplus energy to produce hydrogen(Vialetto et al. 2019). In particular, it can solve the transportation and storage problems of solar and wind energy. To properly utilize the renewable energy produced using SOECs, the produced hydrogen must be used as an alternative fuel and energy carrier for energy supply. In an SOEC cathode, steam is converted into hydrogen and oxygen ions through electrochemical reactions at the cathode; the produced hydrogen flows out and transfers ions to the anode through the electrolyte. Then, oxygen ions in the anode are converted to oxygen and electrons. Equations (1)–(3) and Figure 1 show the overall steam electrolysis reaction in an SOEC(Kang 2013; Menon, Janardhanan, and Deutschmann 2014; Schiller et al. 2019).
CFD-simulation-based optimization of superheater for steam production from waste heat of SRF combustor
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Yunji Kim, Sengryong Park, Chongpyo Cho, Gyuin Yeom, Youngsoon Baek
From a thermodynamics point of view, a portion of the energy required for endothermic water splitting can be obtained from high-temperature heat from excess heat from combustor flue gas, hence significantly reducing the electric energy demand. Furthermore, high-temperature electrolysis not only splits water molecules but also those of carbon dioxide or a mixture of both to produce synthesis gas or other energy carriers such as methane or methanol by subsequent catalytic conversion (Ebbesen et al. 2014; Foit et al. 2017; Kondratenko et al. 2013). If the water can be converted into steam by waste heat from other processes it is more efficient for high-temperature electrolysis (HTE) to convert steam directly. The reasons are the more favorable thermodynamic and electrochemical kinetic conditions for the reaction. Thermodynamic conditions are more favorable in that the molar Gibbs energy of the reaction (ΔG) drops from ~1.23 eV (237 kJ/mol) at ambient temperature to ~0.95 eV at 900°C (183 kJ/mol), while the molar enthalpy of the reaction (ΔH) remains essentially unchanged (ΔH ~1.3 eV or 249 kJ/mol at 900°C). A significant part of the energy required for an ideal (loss-free) HTE can thus be provided by heat (TΔS) coming from external sources or due to the unavoidable Joule effect in the electrolyzer cell. As a consequence, less electricity is required per m3 of H2 generated compared with the other electrolyzer technologies as shown in Figure 1. The transfer from water to steam electrolysis significantly reduces the electricity demand, followed by a continuous decrease with increasing temperature. The theoretical SOEC electrical efficiency is close to 100% for a hydrogen production efficiency of 90% (Schiller, Lang, and Sundarraj 2019).