Feedback control of solid oxide fuel cell spatial temperature variation

Fardadi, Mahshid; Mueller, Fabian; Jabbari, Faryar

doi:10.1016/j.jpowsour.2009.12.111

Cited by 82 publications

(59 citation statements)

References 36 publications

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“…Cell failure can, however, arise from load following or characterisation procedures that neglect degradation. Spatial temperature control is relevant to mitigate such harmful situations [64]. During operation at constant system specific power, the computed probability of failure of the anode increases for completely pre-reformed anode gas, by up to approximately 20%.…”

Section: Cell Failuresmentioning

confidence: 99%

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Nakajo

Mueller

Brouwer

et al. 2012

International Journal of Hydrogen Energy

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107

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Creep Contact analysis a b s t r a c tIntricate relationships between mechanical and electrochemical degradation aspects likely affect the durability of solid oxide fuel cell stacks. This study presents a modelling framework that combines thermo-electrochemical models including degradation and a contact thermo-mechanical model that considers rate-independent plasticity and creep of the components materials and the shrinkage of the nickel-based anode during thermal IntroductionThe end of operation of a solid oxide fuel cell (SOFC) stack ultimately occurs due to the loss of structural integrity of one or several of the cells, as highlighted by several short-stack experiments, e.g [1e4]. We believe this is the result of the accumulation during operation, of physico-chemical alterations inducing a weakening of the materials and interfaces, of plastic and creep deformations, and of the modification of the temperature profile, due to the degradation of the electrochemical performance of the cells. Mechanical issues do not, however, exclusively occur after prolonged use. Inappropriate control during start-up and shut-down and/or following of the electrical power demand, harsh characterisation procedures and thermal cycling can induce discrete failures [5,6]. Despite the evidence of mechanical issues in SOFCs, which are experienced even during laboratory button cell tests, this topic is still receiving limited attention. Efforts are seen as standalone tasks, owing to the different experimental and modelling techniques that are required to gather the essential information, whereas mechanical failures in SOFCs are likely intricately related to chemical and electrochemical aspects.The central component in a stack is the membrane electrode assembly (MEA). As for any multilayered system made of brittle materials, the MEA is prone to failures related to residual * Corresponding author. Tel.: þ41 21 693 35 05.E-mail address: arata.nakajo@epfl.ch (A. Nakajo).Available online at www.sciencedirect.com journal h om epa ge: www.elsev ier.com/locate/he 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 3 7 ( 2 0 1 2 ) 9 2 6 9 e9 2 8 6

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Section: Cell Failuresmentioning

confidence: 99%

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Nakajo

Mueller

Brouwer

et al. 2012

International Journal of Hydrogen Energy

Self Cite

107

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“…The control of the maximum SRU temperature assumes a proper instrumentation (direct or not) of the stack which is needed if spatial temperature control is foreseen [19]. The air inlet temperature determines the air ratio and influences the temperature difference over the SRU.…”

Section: Investigated Casesmentioning

confidence: 99%

“…An efficient mitigation strategy must determine a suitable nominal operating point that balances power density and efficiency requirements with lifetime. Spatial temperature control can alleviate the progressive accumulation of damage under comparatively more harmful operation during load following, which can affect the durability of the SOFC stack [19].…”

Section: Introductionmentioning

confidence: 99%

Progressive activation of degradation processes in solid oxide fuel cells stacks: Part I: Lifetime extension by optimisation of the operating conditions

Nakajo

Mueller

Brouwer

et al. 2012

Journal of Power Sources

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h i g h l i g h t s< Analysis of the combined effect of multiple degradation processes in SOFC stacks. < Acceleration of the degradation and sequential activation of processes is predicted. < Optimisation of the operating conditions can extend lifetime by a factor up to 10. < Operating conditions for the highest performance and the best durability differ. < Overpotential rather than current density influences the degradation behaviour. a r t i c l e i n f o t r a c tThe degradation of solid oxide fuel cells (SOFC) depends on stack and system design and operation. A methodology to evaluate synergistically these aspects to achieve the lowest production cost of electricity has not yet been developed.A repeating unit model, with as degradation processes the decrease in ionic conductivity of the electrolyte, metallic interconnect corrosion, anode nickel particles coarsening and cathode chromium contamination, is used to investigate the impact of the operating conditions on the lifetime of an SOFC system. It predicts acceleration of the degradation due to the sequential activation of multiple processes. The requirements for the highest system efficiency at start and at long-term differ. Among the selected degradation processes, those on the cathode side here dominate. Simulations suggest that operation at lower system specific power and higher stack temperature can extend the lifetime by a factor up to 10, because the beneficial decrease in cathode overpotential prevails over the higher release of volatile chromium species, faster metallic interconnect corrosion and higher thermodynamic risks of zirconate formation, for maximum SRU temperature below 1150 K. The counter-flow configuration, combined with the beneficial effect of internal reforming on lowering the parasitic air blower consumption, similarly yields longer lifetime than co-flow.

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“…Therefore, a key issue in the fuel cell improvement and maximizing its efficiency as well as fuel cell endurance is thermal management. The temperature of the mSOFCs is usually controlled by varying the air flow rate supplied to the cathode channels [1]. The average fuel cell temperature can be effectively controlled using this method, but temperature distributions across the stack still will depend on its design.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of thermal stresses in a new design of microtubular stack

2015

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Microtubular Solid Oxide Fuel Cells (mSOFCs) are one of the most promising and efficient devices that convert chemical energy of fuels into electrical energy. However, mSOFC stacks work at high operating temperature over 650°C, which leads to thermally induced mechanical stresses and in consequence may cause failure of stack components. In order to reduce the local thermal gradients and prevent high stresses in the stack components, it is desirable to study the effect of stack design on its performance. For this purpose a 3D numerical approach was developed to estimate thermal expansion of fuel cell inside an mSOFC stack and to reduce the associated experimental efforts and costs. Initially, a Computational Fluid Dynamics (CFD) model was used to calculate the temperature and species concentration profiles. During the second modeling step temperature profiles were used in the thermo-mechanical model to calculate the thermal stress distribution in the mSOFC stack. The results maximum thermal axial elongation that equals 1.4 mm for the mSOFC stack. The modelled maximum radial elongation was equal to 0.5 mm in the contact areas of the cylindrical housing and manifolds on the fuel inlet side.

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Feedback control of solid oxide fuel cell spatial temperature variation

Cited by 82 publications

References 36 publications

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Progressive activation of degradation processes in solid oxide fuel cells stacks: Part I: Lifetime extension by optimisation of the operating conditions

Numerical analysis of thermal stresses in a new design of microtubular stack

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