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Solid Oxide Fuel Cell Stack with High Electrical Efficiency
Abstract
This article introduces the development of a solid oxide fuel cell (SOFC) stack with anode-supported cells. The SOFC can provide the highest electrical efficiency among all fuel cell types, and high electric efficiency leads to less CO2 produced during power generation.
... High power output lets SOFC suite to large power generation capacity systems, for example, various power plants and container ships. The SOFC is also a good candidate for large distributed energy systems [4,5]. ...
... High power output lets SOFC suite to large power generation capacity systems, for example, various power plants and container ships. The SOFC is also a good candidate for large distributed energy systems [4,5]. There are three consisting parts in a SOFC that are anode, electrolyte and cathode. ...
... Total power generation efficiency of various fuel cells for the electric power output[4]. ...
Lowering the interface charge transfer, ohmic and diffusion impedances are the main considerations to achieve an intermediate temperature solid oxide fuel cell (ITSOFC). Those are determined by the electrode materials selection and manipulating the microstructures of electrodes. The composite electrodes are utilized by a variety of mixed and impregnation or infiltration methods to develop an efficient electrocatalytic anode and cathode. The progress of our proposed core-shell structure pre-formed during the preparation of electrode particles compared with functional layer and repeated impregnation by capillary action. The core-shell process possibly prevented the electrocatalysis decrease, hindering and even blocking the fuel gas path through the porous electrode structure due to the serious agglomeration of impregnated particles. A small amount of shell nanoparticles can form a continuous charge transport pathway and increase the electronic and ionic conductivity of the electrode. The triple-phase boundaries (TPBs) area and electrode electrocatalytic activity are then improved. The core-shell anode SLTN-LSBC and cathode BSF-LC configuration of the present report effectively improve the thermal stability by avoiding further sintering and thermomechanical stress due to the thermal expansion coefficient matching with the electrolyte. Only the half-cell consisting of 2.75 μm thickness thin electrolyte iLSBC with pseudo-core-shell anode LST could provide a peak power of 325 mW/cm² at 700 °C, which is comparable to other reference full cells’ performance at 650 °C. Then, the core-shell electrodes preparation by simple chelating solution and cost-effective one process has a potential enhancement of full cell electrochemical performance. Additionally, it is expected to apply for double ions (H⁺ and O²⁻) conducting cells at low temperature.
... In context of energy sources with the least CO 2 production and continuous increased in global demand for energy, fuel cells demonstrate great opportunity and potential for green energy technology [1,2]. Fuel cells generate electrical energy from chemically modern energy carrier, such as hydrogen, and compatible renewable source, such as solid oxide fuel cell (SOFC) which is an energy conversion energy device that can emerge efficiency as high as 70% with regeneration [3]. It has been proven that solid oxide fuel cells (SOFCs) indeed clasps larger potential compared with other fuel cell technology primarily due to usage of low cost apparatus and component and high electrical delivery efficiency without incidental to Combined Heat and Power (CHP) [4]. ...
... Metals are glassy or crystalline which respect to treatment strategies. Metal mixtures or alloys are heated or treated to develop better material properties than pure elemental Fig. 1 e Efficiency of SOFC and other electric generator [3]. i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( x x x x ) x x x metals. ...
... Fig. 14 shows formation of (CreMn) 3 O 4 when LSM was used as coating material. The phase of (CreMn) 3 O was determined using X-ray diffraction (XRD) analysis, and SEM image proved the existence of oxidation layers in which the outer layer is (CreMn) 3 O, whereas the inner layer is Cr 2 O 3 . ...
Progressive efforts on lowering working temperature of Solid Oxide Fuel Cell (SOFC) to approximately 600 °C enable application of stainless steel as interconnector instead of expensive ceramic. Prolonged exposure of stainless steel to SOFC operating conditions can lead to chromium poisoning owing to migration of chromium (IV) species to cathode and significantly reduces electrical conductivity of cells. Ferritic stainless steel is potential candidate as interconnector because it has appropriate chromium content and is less expensive compared other stainless steels. Protective coating layer on interconnector is essential in minimizing chromium poisoning phenomenon in aspect of area specific resistance (ASR), thermal expansion coefficient (TEC) and coating uniformity. Addition of transition metal to coating layer is an enhanced method to improve coating behavior. Nickel, copper, manganese and silver are promising metals that can be used as coating layer to inhibit chromium (IV) species from diffusing outward and improve electrical conductivity and excellent oxidation resistance. This paper reviews oxidation behavior of coating layer of interconnector of SOFC, sintering effect, protective coating technique and influence of transition metal in the coating layer.
... The high operating temperature of SOFCs contributes to their high electrical efficiency [52]. SOFCs operate at elevated temperatures, eliminating the need for costly platinum group metal catalysts essential for lower-temperature fuel cells. ...
... where LHV is the low heating value of the fuel, V is the average voltage, F f uel is the molar flow rate of fuel, U f is the fuel utilisation, and n is the number of electrons involved in the electrochemical reaction. The high operating temperature of SOFCs contributes to their high electrical efficiency [52]. SOFCs operate at elevated temperatures, eliminating the need for costly platinum group metal catalysts essential for lower-temperature fuel cells. ...
Solid oxide fuel cells (SOFCs) have garnered significant attention as a promising technology for clean and efficient power generation due to their ability to utilise renewable fuels such as hydrogen and ammonia. As carbon-free energy carriers, hydrogen and ammonia are expected to play a pivotal role in achieving net-zero emissions. However, a critical research question remains: how does the electrochemical performance of SOFCs compare when fuelled by hydrogen vs. ammonia, and what are the implications for their practical application in power generation? This mini-review paper is premised on the hypothesis that while hydrogen-fuelled SOFCs currently demonstrate superior stability and performance at low and high temperatures, ammonia-fuelled SOFCs offer unique advantages, such as higher electrical efficiencies and improved fuel utilisation. These benefits make ammonia a viable alternative fuel source for SOFCs, particularly at elevated temperatures. To address this, the mini-review paper provides a comprehensive comparative analysis of the electrochemical performance of SOFCs under direct hydrogen and ammonia fuels, focusing on key parameters such as open-circuit voltage (OCV), power density, electrochemical impedance spectroscopy, fuel utilisation, stability, and electrical efficiency. Recent advances in electrode materials, electrolytes, fabrication techniques, and cell structures are also highlighted. Through an extensive literature survey, it is found that hydrogen-fuelled SOFCs exhibit higher stability and are less affected by temperature cycling. In contrast, ammonia-fuelled SOFCs achieve higher OCVs (by 7%) and power densities (1880 mW/cm² vs. 1330 mW/cm² for hydrogen) at 650 °C, along with 6% higher electrical efficiency. Despite these advantages, ammonia-fuelled SOFCs face challenges such as NOx emissions, nitride formation, environmental impact, and OCV stabilisation, which are discussed alongside potential solutions. This mini review aims to provide insights into the future direction of SOFC research, emphasising the need for further exploration of ammonia as a sustainable fuel alternative.
... Yttria-stabilized zirconia (YSZ) is a typical electrolyte utilized in standard SOFC systems. Operating temperatures often reach 1000 ο C to achieve the required quantity of YSZ ionic conductivity [1][2][3][4]. Yet there are numerous challenges at these elevated working temperatures, such as thermal misfit between parts of the cell, and chemical instabilities. ...
This study involved the synthesis of rare-earth (Sm 3+ and Nd 3+) co-doped ceria (CeO 2) through the co-precipitation method, utilizing sodium hydroxide (NaOH) as the precipitating agent to improve the ionic conductivity of the materials intended for use as an electrolyte of solid oxide fuel cells (SOFCs) applications. The crystal structure and morphology of the synthesized materials were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The absence of secondary phases indicates the material's phase purity. Structural analysis revealed that the lattice constant (a) and average crystallite size (L) increased with higher Nd 3+ concentrations as a result of substituting a minor amount of Nd 3+ with Sm 3+ , which possesses larger ionic radii in comparison to Sm 3+. SEM images showed that particle size grew from 52 nm to 102 nm as the Nd 3+ concentration increased predicting the grain growth suppressing grain boundaries. Energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental composition that agreed with the starting composition of the synthesized materials. Impedance analysis indicated a decrease in grain and grain boundary resistances with increasing Nd 3+ content up to 10 %. Consequently, ionic conductivity was enhanced, reaching a maximum value of 6.24 × 10 − 2 S/cm at 750 • C as compared to single-doped ceria (SDC) for the composition. Ce 0.80 Sm 0.10 Nd 0.10 O 2− δ , with the lowest activation energy recorded at 0.53 ± 0.01 eV. These findings indicate that NaOH-assisted co-precipitation is a beneficial technique for synthesizing co-doped ceria materials. The resulting materials possess ionic conductivity comparable to that synthesized with ammonium carbonate and urea as precipitating agents, making them interesting candidates for SOFC electrolyte applications requiring high ionic conductivity.
... Solid oxide fuel cells (SOFCs) have emerged as a viable sustainable energy technology for stationary power production and other applications because of their high efficiency, low emissions, and fuel adaptability. SOFCs operate at high temperatures and include multiple critical components, including the anode, cathode, and electrolyte [1][2][3][4]. The electrolyte material separates the fuel (usually hydrogen or hydrocarbons) and oxidant (often air or oxygen) streams, enabling oxygen ions to migrate. ...
This study explores the impact of co-doping on ceria-based electrolyte materials with samarium (Sm) and gad-olinium (Gd) to improve their structural, morphological, and ionic conductivity properties synthesized through a co-precipitation technique using sodium hydro-oxide (NaOH) as the precipitating agent for solid oxide fuel cell (SOFC) applications. The aforementioned approach provides benefits like uniformity, high purity, and simplicity of synthesis. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize the crystal structure and morphology of the synthesized materials. No secondary phases were observed revealing the phase purity of the material. A decrease in lattice constant was detected due to the replacement of a small concentration of Gd with Sm having small ionic radii compared to Sm. Homogeneity and decrease in particle size of prepared samples were observed via SEM analysis predicting the enhancement in the grain size with the reduction in grain boundaries and elemental composition through EDX agreed with the starting composition. Impedance spectroscopy was employed to measure the ionic conductivity of the electrolyte samples. Our results demonstrate a significant decrease in grain and grain boundary resistances causing the increase in ionic conductivity with the introduction of Gd and Sm as co-dopants into the ceria structure. The optimal doping concentration was found to be 10 % Gd and 10 % Sm. The co-doped ceria had a high ionic conductivity of 6.28 × 10 − 2 S/cm at 750 ο C and a low activation energy of 0.44 eV, indicating improved ionic mobility. This study provides valuable insights into the role of Gd and Sm co-doping in enhancing the ionic conductivity of ceria-based electrolyte materials, which is crucial for the advancement of high-performance SOFCs.
... The conversion efficiency for a fuel cell is typically of the order of 30e60% LHV (Lower Heating Value), but depends on the type and design. Fig. 3 [30] shows that fuel cells operate at low to medium temperature (50e210 C o ) and low power generation efficiency 30e50% when methanol or hydrocarbons are used as fuel and 50% when hydrogen is the fuel. Fuel cells work with high operating temperature (600e1000 C o ) when direct conversion of hydrocarbons occurs. ...
Recently, to reach zero emission levels, some new energy systems based on fuel cells have been developed. This paper presents a review of investigations of these systems by thermodynamics performance, mainly, energy and exergy analysis. With energy analysis, the performance of an energy conversion system cannot be effectively and accurately evaluated. But exergy analysis complements and reinforces energy analysis. Using exergy analysis in relation to the degree of irreversibility in each section is a quality method and can be useful in fuel cell analysis. Analysis based on the first and second laws of thermodynamics seems useful in most cases and here reviews for low-temperature and high-temperature fuel cells are given. As a result, regardless of the type of the FC-system and its application, there is always a need of thermo-economic analysis to investigate the effect of various parameters on the system performance, such as different fuel sources, different operating conditions, different subsystems and energy sources to combine with the fuel cell.
... The intermediate solid oxide fuel cells (ITSOFCs) are economical and green power sources for large scale distributed power generation [1,2]. The energy conversion efficiency of sandwich-structured solid oxide fuel cell (SOFC), which consists of anode, electrolyte and cathode, is determined by interface, ohmic and diffusion impedances. ...
The composites consisted of oxygen ion conductive (La0.75Sr0.2Ba0.05)0.175Ce0.825O1.891 (LSBC) and proton conductive BaZr0.1Ce0.7Y0.2O3-δ (BZCY) prepared by solid state reaction and impregnation are sintered to form composite and phase gradient membranes, respectively. The conductivity of (100-x)LSBC-xBZCY composite membranes exhibit non-ohmic in air and semiconductive diode behavior in Ar/5%H2 higher than 500 °C. The elemental concentration gradient of Ba, Ce and O at grain boundaries of LSBC/BZCY corresponds to the inter-diffusion and Schottky barrier formation. The Schottky barrier of dual phase boundary (DPB) may be beneficial for dual-ion conduction. The microstructures of sintered and polished (100-x)LSBC-xBZCY surface exhibit convex hard LSBC and concave soft BZCY. The percolated 70LSBC-30BZCY of the composite membrane obtains the power density of 20.51 mW/cm². The phase gradient membrane of BZCY impregnated LSBC presents the higher power density of 40.6 mW/cm² (700 °C). The new two-phase composite and phase gradient membranes generate more simple and compact layer structure than sandwiched solid oxide fuel cell. Such two-phase dual-ion membranes provided by our economical process can be considered to develop new single membrane fuel cells possibly.
... Fuel cells are electrochemical devices that produce clean electricity and water as a byproduct [45,46]. They offer clean energy by the mean of simple electrochemical reaction (transfer of electrons and protons) [47], no moving parts, and high efficiency (45% − 65%) [48]. However, they generate a significant amount of heat while producing electricity and this amount of heat should be removed to avoid overheating [49]. ...
Nowadays the World faces critical issues, such as increasing power costs, environmental impacts of fossil fuel, and global warming. In this respect, scientists are trying to improve the efficiency of the energy harvesting. The enhancement of power generation sectors is focused on the waste heat recovery systems based on thermoelectric generators (TEGs) that have demonstrated the capacity to transfer thermal energy directly into electric energy via the Seebeck effect. TEG uses the available waste heat sources in different applications to produce power, thus it considered as an eco-friendly power source. In the present study, the integration of thermoelectric systems with other technologies for green power production is introduced. This work introduces a background about the common materials used in the fabrication of the TEG. Furthermore, the application of the TEG to harvest waste heat from different sources, i.e., fuel cells, heat exchangers, photovoltaics, internal combustion engine, electric vehicles, and hybrid waste heat recovery systems have been summarized. The characteristics of thermoelectric generators are discussed, considering the different operating and design parameters. Finally, the barriers and challenges facing the applications of the thermoelectric generators for waste heat recovery are also discussed.
... Water (H 2 O) and carbon dioxide (CO 2 ) are the only reaction products. Several types of SOFC stacks have been developed to date such as quadrilateral planar [6], all ceramic quadrilateral planar [7], circular planar [8,9], tubular [10], microtubular [11][12][13][14], cone shaped segmented-in-series tubular [15], segment-in-series tubular [16], segmented-in-series flattened tubular [17][18][19], flattened tubular [20,21], honeycomb [22,23], and micro [24] designs. Microtubular SOFC stacks are quite rare in applications compared to planar SOFC stacks. ...
Computational fluid dynamics (CFD) and finite element analysis (FEA) are important modelling and simulation techniques to design and develop fuel cell stacks and their balance of plant (BoP) systems. The aim of this work is to design a microtubular solid oxide fuel cell (SOFC) stack by coupling CFD and FEA models to capture the multiphysics nature of the system. The focus is to study the distribution of fluids inside the fuel cell stack, the dissipation of heat from the fuel cell bundle, and any deformation of the fuel cells and the stack canister due to thermal stresses, which is important to address during the design process. The stack is part of an innovative all-in-one SOFC generator with an integrated BoP system to power a fixed wing mini unmanned aerial vehicle. Including the computational optimisation at an early stage of the development process is hence a prerequisite in developing a reliable and robust all-in-one SOFC generator system. The presented computational model considers the bundle of fuel cells as the heat source. This could be improved in the future by replacing the heat source with electrochemical reactions to accurately predict the influence of heat on the stack design.
... The importance of creating low-carbon clean energy and not simply relying on commercial power became apparent in the aftermath of the Great East Japan Earthquake of March 20. One such energycreating technology under development at NTT Energy and Environment Systems Laboratories is the high-efficiency solid oxide fuel cell [5]. ...
The Feature Articles in this issue focus on NTT's efforts to introduce environmentally friendly and energy-efficient technology in line with objectives to establish effective business continuity planning and, ultimately, to achieve a sustainable society. The Great East Japan Earthquake in March 2011 was a forceful reminder of the importance of both of these areas. This article presents an overview of NTT's energy management technologies that are bringing us closer to a sustainable society and reviews green infrastructure technologies that help conserve natural resources.
... The required output can be obtained by stacking the appropriate number of cell units. The 40unit stack shown in Fig. 6 attains an output of about .5 kW with an efficiency of over 60% [5], [6]. ...
The long-lasting commercial power outage caused by the catastrophic earthquake in eastern Japan in 2011 demonstrated the importance of the power supply in providing continuous telecommunication services. This article introduces an approach to power supply to ensure that telecommunication services operate normally in all situations and describes the development of high energy density secondary batteries and highly efficient fuel cells to achieve energy storage and generation for that purpose.
This article introduces the status of research and development being performed by NTT Energy and Environment Systems Laboratories based on the concept of information and communications technology (ICT) combined with energy called "ICT × energy". This should lead to systems capable of ensuring stable power supply, saving energy, and shifting load peaks as well as to technologies that use smart energy management.
The conventional relations for calculating the fracture stresses consider only elastic deformation but ignore viscoelastic and viscoplastic behaviors. Measuring the joining strength of a composite glass sealant‐metallic interconnect specimen at solid oxide cell application relevant at high temperatures is a case where such effects can become significant. In the current study, three‐point and four‐point bending test results were analyzed using the finite element method (FEM) to assess systematic and random errors. It is shown that plastic deformation of the steel interconnect material at high temperature, although having a large effect on the stress distribution in the steel/glass–ceramic/steel specimen, does not cause a significant difference in the FEM‐derived true and the standard equation‐based analytically derived flexural stress values. It is also observed that even if the viscous flow of the glass–ceramic is considered in the simulations, the samples’ behavior in a realistic testing condition is not biased significantly by inelastic behavior due to the short testing time.
The conventional static relations, using for calculating the strength value, ignore factors such as the elastic, viscoelastic, and viscoplastic behaviors of the sample components. The impact of these behaviors would be significant when the specimen is not uniform and rigid. Measuring the joining strength of a glass sealant-metallic interconnect at high temperatures for solid oxide cell applications is one of these cases. In this study, the results obtained from three-point and four-point bending tests were compared with simulation outputs to determine the systemic and random errors. This study shows that plastic deformation of steel at high-temperature, although having a large effect on the stress distribution in the steel/glass-ceramic/steel specimen, does not cause a significant difference in the actual and measured flexural strength values. It was also found that even if the glass-ceramic viscous flow is assumed, the sample does not show severe inelastic behavior due to the high test speed.
The current fuel cell technologies are reviewed, with emphasis on their use for combined cycles of heat and power. The advantages of not generating polluting gases in their operation, providing high-energy efficiency and low level of noises are emphasized, as these make them the most adequate solution for several applications, in particular for co-generation of heat and power in combined cycles. The technologies reviewed are alkaline fuel cells, proton exchange membrane fuel cells, microbial fuel cells, molten carbonate fuel cells, phosphoric acid fuel cells and solid oxide fuel cells; the use of high-temperature fuel cells in combined cycles is discussed, emphasizing the increase in the efficiency.
This article provides an overview of NTT Energy and Environment Systems Laboratories' research and development (R&D) objectives and initiatives to move the country toward a green society. Our ambitious R&D agenda is based on three key concepts-Green ICT, Green materials, and Governance by Green-with the goal of completely eliminating CO2 emissions and waste generated by the NTT Group's business activities by the year 2050.
This article reports on the development of a 3-kW class solid oxide fuel cell (SOFC) power generation module being developed jointly by NTT, Sumitomo Precision Products Co., Ltd., and Toho Gas Ltd. as an industrial stationary power generation system. NTT has been developing cell materials, anode-supported cells, and SOFC stack technologies. The 3-kW class SOFC power generation module uses two 40-cell SOFC stacks. This module provided long-term and maximum electrical efficiencies of 56% and 59%, respectively.
One of the most important and promising electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFC) are those based in gadolinium-doped ceria. The electrolytes were obtained by mechanical alloying in a high-energy planetary ball mill, analyzing the relation between the milling time (0, 2, 4, 8, 16 and 20 h) and the crystallite size, lattice parameter and particle size. The effect of the concentration of gadolinium (5, 10, 15 mol %) and the use of another rare earth (praseodymium, neodymium, europium or erbium) as co-dopant also were evaluated. Two sintering methods were used to increase the green body density: the conventional route and PECS; showing a highly dependence on the density and grain size respect to die sintering route. The best results were observed with the conventional route, with high densities for samples sintered at 1723 K for 6 h. Although PECS produced smaller grain sizes due to lower sintering temperatures, the relative densities were only about 90% after a heat treatment; due to the partial reduction of ceria in low oxygen partial pressures. The ionic conductivity was measured on the CS samples, with the highest values for samples with 10% and 15% of Gd and Pr or Nd as codopant.
During the last years, the development of electric propulsion systems is pushed strongly, most notably for
automotive applications. For ground based transportation, the system mass is relevant, but of relatively
low importance. This paper addresses the application of electric propulsion systems in aeronautics, where
all systems are much more constrained by their mass. After comparing different propulsion system
architectures the focus is cast on the energy storage problem and here especially on battery storage
systems. Using first order principles the limitations and required technology developments are
demonstrated by introducing battery powered electric propulsion systems to small and medium sized
aircraft.
This article introduces the research and development being undertaken at NTT on solid oxide fuel cells, which are expected to achieve the highest efficiency among fuel cells. Fuel cells are efficient devices for generating electric power by using the chemical reaction between a fuel and oxygen. They are not only expected to bring environmental benefits such as reduced CO 2 emissions, but are also attracting the attention of distributed power generation businesses as a result of the trend towards the deregulation of the electric power industry.
We investigated a solid oxide fuel cell stack that employs anode-supported planar cells in which two intermediate plates are installed every 10 cells to determine the influence of the separation and reconnection of the intermediate plates after high temperature operation. We showed that this separation and reconnection caused no significant degradation in stack performance. A 30-cell stack, which was constructed by removing two 10-cell sub-stacks from a 50-cell stack that had operated stably 1200h, functioned well. The difference between the average voltages of the cells in the 50- and 30-cell stacks was less than 3% when the current density, fuel utilization, and oxygen utilization were 0.30Acm−2, 60%, and 15%, respectively. The 30-cell stack operated stably for about 1200h with almost no degradation. These findings indicate that our stack can be restored after cells in the stack have broken down simply by removing the 10-cell sub-stacks that contain the broken cells and replacing them with undamaged 10-cell sub-stacks.