Transient Response Analysis of an 100cm&lt;sup&gt;2&lt;/sup&gt; Class Molten Carbonate Fuel Cell

Lee, Choong Gon; Nakano, Hiroshi; Nishina, Tatsuo; Uchida, Isamu; Izaki, Yoshiyuki; Kuroe, Satoshi

doi:10.5796/kogyobutsurikagaku.64.486

Cited by 9 publications

(3 citation statements)

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“…It took about 0.2 s before this seemingly constant potential was reached. Lee et al 4 ascribe the process with the shortest time constant to the real ohmic drop and the second process to charge-and mass-transfer resistances. The effect of ohmic drop and charge/mass-transfer processes combined is accounted for in both the simple model and the extended model by a single quasi-ohmic resistance r. Therefore, 0.2 s is about the time constant we need to determine the quasi-ohmic resistance.…”

Section: Resultsmentioning

confidence: 99%

Verification of Analytical Fuel Cell Models by Performance Testing at a 110 cm2 Molten Carbonate Fuel Cell

Peelen

Standaert

et al. 2001

J. Electrochem. Soc.

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This paper presents a performance test of a 110 cm 2 molten carbonate fuel cell bench cell as a function of output current and gas utilization. These results are compared with the predictions of cell performance of two analytical models, the simple and extended model, for which a revised derivation is given. A comparison of measurements and models results in a value for the quasi-ohmic resistance, r, of 1.02 and 1.07 ⍀ cm 2 , respectively, for the simple model and the extended model. Using this as the only fitted parameter and other theoretical parameters, the simple and the extended model describe the cell performance with a relative error of at most 5 and 1%, respectively, for fuel utilization above 10%. Both models have therefore shown their reliability.Successful industrial applications of molten carbonate fuel cells ͑MCFCs͒ need accurate prediction of unit-cell performance and operation characteristics. This unit-cell characteristic is the basis for accurate mathematical models of fuel cell systems, which facilitates the integration and optimization of the MCFC in existing industrial processes by enabling the systematic study of the total system's benefits, efficiency, and costs. In other words, applications of MCFCs can only be explored when accurate unit-cell models are available. Such models are derived from descriptions of the physical processes inside the unit-cell using both thermodynamic parameters and kinetic parameters. Therefore, both types of parameter determine the cell's efficiency and performance. Although thermodynamic parameters can be calculated using available thermodynamical properties, kinetic parameters can only be obtained experimentally. Therefore, reliable experimental results are essential for accurate performance prediction and thus for the application of fuel cells. Furthermore, in these mathematical models, assumptions are made regarding physical processes in order to simplify the models. To justify these assumptions experimental data is needed to verify the reliability of the models.This article presents the verification of the operation characteristics predicted by the analytical fuel cell models for a unit-cell proposed by Standaert et al. 1,2 The predicted operation characteristics are compared with measurements on a 110 cm 2 MCFC bench cell using only one experimental parameter. This experimental parameter is the internal resistance of the MCFC.In previous derivations of the analytical fuel cell models, little attention was paid to distinguish the difference between theoretical parameters and measurable quantities, hence compromising the practical use of these models. Therefore, we first give a revised derivation to models containing only operational parameters that can be measured or calculated. TheoryBasic fuel cell model.-In a fuel cell under load, gaseous reactants are converted into products species, heat, and electric power. The objective of the fuel cell model is to determine which fraction of chemical energy stored in the reactant is converted into electric power and ...

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Section: Resultsmentioning

confidence: 99%

Verification of Analytical Fuel Cell Models by Performance Testing at a 110 cm2 Molten Carbonate Fuel Cell

Peelen

Standaert

et al. 2001

J. Electrochem. Soc.

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“…The information of the MCFC was generally obtained by performing polarization measurements or gas analyses of the gas compositions at the inlet and outlet of the cell. However, an attempt has been made to obtain the information by carrying out transient response analyses such as electrochemical impedance spectroscopy ͑EIS͒ [1][2][3][4][5] and Current Interrupt ͑CI͒ measurements. 3,6 Nishina et al 7 reported that the EIS measurements performed on the MCFC bench-scale cells presented two semicircular arcs: The high-frequency arc, which reflects the degree of polarization caused by the effects of exchange current density or mass transfer in both electrodes, and the lowfrequency arc, which reflects the degree of polarization caused by the effects of Nernst loss in both.…”

mentioning

confidence: 99%

“…However, an attempt has been made to obtain the information by carrying out transient response analyses such as electrochemical impedance spectroscopy ͑EIS͒ [1][2][3][4][5] and Current Interrupt ͑CI͒ measurements. 3,6 Nishina et al 7 reported that the EIS measurements performed on the MCFC bench-scale cells presented two semicircular arcs: The high-frequency arc, which reflects the degree of polarization caused by the effects of exchange current density or mass transfer in both electrodes, and the lowfrequency arc, which reflects the degree of polarization caused by the effects of Nernst loss in both. The Nernst loss results from the hydrogen or oxygen concentration profile of the reaction gases in gas flow direction corresponding to the current density distribution.…”

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confidence: 99%

EIS as a Tool to Determine Fuel Flow Distribution in Molten Carbonate Fuel Cells

Morita

Nakano

Mugikura

et al. 2003

J. Electrochem. Soc.

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Electrochemical impedance spectroscopy measurements made on bench-scale molten carbonate fuel cells have been used to obtain more information on the inside state of a cell than polarization measurements alone offer. In the frequency range 1 kHz to 10 mHz, the impedance response exhibited two semicircular arcs before and after approx. 3 Hz. An equivalent circuit model and a reactor model were employed to enhance the understanding of the nature of the low-frequency arc ͑3 Hz-10 mHz͒ in the impedance response at nearly open-circuit voltage. The size of the low-frequency arc, which was obtained by the measurements, increases as the flow rate of the gas fed into the cell decreases. The diameter of the low-frequency arc and the fuel flow rate are in inverse proportion to each other. This relation provides useful information for estimating the fuel gas distribution among the stack's cells.

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High Oxide Ion Conduction in Molten Na₂W₂O₇

Wang

et al. 2018

Adv Elect Materials

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requires highly oxide-ion conducting materials at relatively low temperatures, which has stimulated extensive searches for new oxide ion conductors. Exploiting oxide ion conduction in various substances and unraveling the generic structural features that facilitate oxide ion mobility are important in reaching these low operating temperatures regimes.Conventionally oxide ion conductors are crystalline materials with lattice defects of oxygen vacancies or interstitials, such as the leading oxide-ion conducting electrolytes yttria-stabilized zirconia (YSZ) fluorite and strontium and magnesium codoped LaGaO 3 (LSGM) perovskite phases transporting oxygen via vacancies, [2,3] and the relatively rare oxygen-interstitial conductors of La 10−x (SiO 4 ) 6 O 3−1.5x apatite [4] and La 1+x Sr 1−x Ga 3 O 7+0.5x melilite [5] structures. Although the commonly ionic transport in molten materials has been utilized in electrolysis for more than two centuries, there is very little attention on the oxide ion conduction in molten electrolytes and its usage in energy technologies. Inspired by the fast oxygen transport in the liquid-channel grain-boundary structure (LGBS) [6] that was discovered in the oxide scale on copper surfaces in the catastrophic oxidation process, recently interest in exploiting oxide ion conduction in molten materials is growing for the next generation materials for electrochemical energy devices. Oxide ion conduction has been observed in melts based on the Bi 2 O 3 , V 2 O 5 (V 2 O 5 -BiVO 4 and V 2 O 5 -ZrV 2 O 7 ) and TeO 2 oxides. [6] More recently a new molten oxide fuel cell (MOFC) concept has been proposed by Belousov et al. based on the advantages of molten oxide ion conductors, including high ionic conductivity and ductility over the conventional ceramic materials. [7] The ductility of molten electrolytes is beneficial for overcoming problem of thermal incompatibility of SOFCs. The feasibility of MOFC was demonstrated on a LGBS material consisting of TeO 2 solid grains and molten TeO 2 -Te 4 Bi 2 O 11 electrolyte, [7] although it reached a low output power density ≈11.5 mW cm −2 at 640 °C. A polymer model [8] was considered to explain the oxide ion conduction in the oxide melts: a polymerlike structure was assumed for the oxide ion conducting melts; disconnection of the polymer chain could take place, forming two new chains and an oxygen pseudo-vacancy at the end of one of them; this oxygen pseudo-vacancy will capture a free oxygen ion that is chemisorbed on the atmosphere-melt interface; reconnection of these two polymer chains promoting the oxide ion migration to the nearest vacancy in the melts.

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Transient Response Analysis of an 100cm<sup>2</sup> Class Molten Carbonate Fuel Cell

Cited by 9 publications

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Verification of Analytical Fuel Cell Models by Performance Testing at a 110 cm2 Molten Carbonate Fuel Cell

Verification of Analytical Fuel Cell Models by Performance Testing at a 110 cm2 Molten Carbonate Fuel Cell

EIS as a Tool to Determine Fuel Flow Distribution in Molten Carbonate Fuel Cells

High Oxide Ion Conduction in Molten Na₂W₂O₇

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Transient Response Analysis of an 100cm<sup>2</sup> Class Molten Carbonate Fuel Cell

Cited by 9 publications

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Verification of Analytical Fuel Cell Models by Performance Testing at a 110 cm2 Molten Carbonate Fuel Cell

Verification of Analytical Fuel Cell Models by Performance Testing at a 110 cm2 Molten Carbonate Fuel Cell

EIS as a Tool to Determine Fuel Flow Distribution in Molten Carbonate Fuel Cells

High Oxide Ion Conduction in Molten Na2W2O7

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High Oxide Ion Conduction in Molten Na₂W₂O₇