Molten Carbonate Fuel Cell Stack Research Articles

Nonlinear fuzzy modeling of a MCFC stack by an identification method

This paper reports a nonlinear fuzzy modeling study of a molten carbonate fuel cell (MCFC) stack by an identification method. MCFC is a complex nonlinear, multi-input and multi-output (MIMO) system that is hard to model by traditional methodologies. The Takagi–Sugeno (T–S) fuzzy model is suitable to model a large class of nonlinear MIMO system. In this paper, a MIMO T–S fuzzy model is used to represent MCFC. An identification method is used to determine both the nonlinear parameters of the antecedents and the linear parameters of the rules consequent in the T–S fuzzy model. The simulation tests reveal that obtained T–S fuzzy model using the identification method can efficiently approximate the static and dynamic behavior of a MCFC stack. Furthermore, based on this proposed T–S fuzzy model, valid control strategy studies such as predictive control, robust control can be developed.

Temperature control of MCFC based on an affine nonlinear thermal model

The molten carbonate fuel cell (MCFC) is a promising device for stationary power and heat supply. In this work, the temperature control in MCFC stack is studied. The operating temperature of the stack is an important controlled variable, which impacts the performance of the MCFC due to thermal cycling. In order to improve the generating performance of the MCFC, prolong its life and guarantee safety, credibility and low degradation of the fuel cell, the temperature of MCFC must be controlled efficiently. Based on analyzing the temperature dynamic model of MCFC, a model-based variable structure control (VSC) controller is designed for MCFC in this paper. The optimal parameters of VSC are selected by genetic algorithm (GA). Numerical results demonstrate the effectiveness and advantages of this approach.

Design and Partial Load Performance of a Hybrid System Based on a Molten Carbonate Fuel Cell and a Gas Turbine

AbstractThis paper addresses the design and part load performance analysis of a hybrid system (HS) combining a molten carbonate fuel cell stack with a micro gas turbine. A numerical simulation is carried out in order to define the optimal parameters of the HS. The calculation results show that the generating efficiency of the HS is close to 60% at the design point and over 56% at part load conditions. At the design point, the net power supplied by the HS is 12.6kW, with about 80% coming from the stack and 20% from the gas turbine. At part load conditions, the contribution of the MCFC increases, since the working performance of the turbine is reduced.

Study on a new structure of the separator plate assembly for molten carbonate fuel cell (MCFC) stacks

A new structure of separator plate assembly (SPA), which consisted of a separator plate, flow field plates, perforated plates, frame plates and seal gaskets, was developed for a molten carbonate fuel cell (MCFC) in this study. In this structure, the separator plate, flow field plates and perforated plates were hard-contacted (directly contacted each other); meanwhile the frame plates and the separator plates were bound with the inorganic seal gaskets. SPA and electrodes could be combined together to form a unit of electrode-SPA. The new structure SPA promoted the smooth volatilizing and complete burning of the organic compounds in the matrix. It was effective and reliable to press the stack with a suitable stacking pressure. It was facile and simple to assemble a stack by using electrode-SPA. With the electrode-SPAs, two MCFC stacks were assembled in co-flow and counter-flow, respectively. The performance of Stack B in counter-flow was higher than that of Stack A in co-flow at the same current density. The more uniform temperature distribution and current density distribution in Stack B were responsible for its higher performance.

Manifold gasket accommodating differential movement of molten carbonate fuel cell stack

Manifold gasket accommodating differential movement of molten carbonate fuel cell stack

Development of a Three-Dimensional Molten Carbonate Fuel Cell Model and Application to Hybrid Cycle Simulations

In this paper, a three-dimensional finite volume model of a molten carbonate fuel cell (MCFC) is presented. The model applies a detailed electrochemical and thermal analysis to a planar MCFC stack of given geometry and assigned input flows conditions, material properties and assigned external heat losses, calculating global energy balances and reactant utilization, as well as internal temperature and chemical composition profiles, pressure profiles, polarization losses, and current density and voltage distribution over the stack. The model is calibrated on the available data for an experimented MCFC stack manufactured by Ansaldo Fuel Cells. The comparison of 2D versus 3D simulations is first discussed, showing the importance of the 3D model for an accurate analysis of real stack operation under significant heat loss conditions, but also showing the mutual influence of heat transfer between adjoining cells and evidencing the variable electrical performances between different cells of the same stack. As a counterpart, application of the 2D model, which takes advantage by much shorter calculation time while keeping a reasonable accuracy in the overall energy balances, is anyway indicated for complex cycle analysis and cycle optimization, where a complete 3D stack analysis may be limited to selected cases. Then, the model is applied to the off-design analysis of hybrid cycles based on a recuperated gas turbine arrangement where variable pressure ratios and fuel supply conditions are assumed for the fuel cell. The effects of the operating pressure and of the adoption of different fuel compositions are considered, with a cycle layout that may include natural gas reforming or is directly fed by a syngas provided by an external source, simulating different fuel feedstocks (e.g., coal gasification). Complete results are presented, in terms of fuel cell and overall cycle performances.

Nonlinear modeling of molten carbonate fuel cell stack and FGA-based fuzzy control

To improve the performance of fuel cells, the operating temperature of molten carbonate fuel cell (MCFC) stack should be controlled within a specified range. In this paper, with the RBF neural network’s ability of identifying complex nonlinear systems, a neural network identification model of MCFC stack is developed based on the sampled input-output data. Also, a novel online fuzzy control procedure for the temperature of MCFC stack is developed based on the fuzzy genetic algorithm (FGA). Parameters and rules of the fuzzy controller are optimized. With the neural network identification model, simulation of MCFC stack control is carried out. Validity of the model and the superior performance of the fuzzy controller are demonstrated.

MOLTEN CARBONATE FUEL CELL MODELLING

Hybrid plants where a fuel cell and a gas turbine are combined have attracted the attention of the power system community. In this paper, a model is provided of a Molten Carbonate Fuel Cell stack and of the thermo-hydraulic equipment in which it is embedded. The model is worked out from basic physical considerations; however, it is also simple enough for simulation and control purposes. Besides, it has been validated against experimental data.

Control-oriented nonlinear modelling of molten carbonate fuel cells

Performance and availability of molten carbonate fuel cells (MCFC) stack are greatly dependent on its operating temperature. Control of the operating temperature within a specified range and reduction of its temperature fluctuation are highly desirable. The models of MCFC stack existing are too complicated to be suitable for design of a controller because of its lack of clear input–output relations. In this paper, according to the demands of control design, a quantitative relations model of control-oriented MCFC between the temperatures of the stack and flowrates of the input gases is developed, based on conservation laws. It is an affine nonlinear model with multi-input and multi-output, the flowrates of fuel and oxidant gases as the manipulated vector and the temperatures of MCFC electrode–electrolyte plates, separator plates as the controlled vector. The modelling and simulation procedures are given in detail. The simulation tests reveal that the model developed is accurate and it is suitable to be used as a model in designing a controller of MCFC stack. Copyright © 2004 John Wiley & Sons, Ltd.

Numerical analysis of the single electrode heat effect in molten carbonate fuel cells: temperature analysis of the electrolyte plate by applying irreversible thermodynamics

A temperature analysis model of a molten carbonate fuel cells (MCFC) stack is used to calculate the single electrode heat effects. The magnitude of heat which evolves from the cathode and absorbed at the anode is large, and in similar value to the electrical output of a MCFC. This suggests that the heat evolution of a single electrode causes a temperature difference between the electrodes. The temperature distribution in the electrolyte plate is evaluated to establish more accurate results concerning the temperature analysis model of the stack. The temperature distribution in the electrolyte plate is studied by applying irreversible thermodynamics. When the operating current density is less than 3000 A m−2 and the thermal conductivity of the electrolyte is more than 2 W m−1 K−1, the temperature difference between cathode and anode is estimated to be less than approximately 1 K. This result proves that the temperature difference between the electrodes can be supposed constant in constructing the temperature analysis model of the MCFC stack. This results also allows us to construct a two-dimensional heat production distribution in the cell plane and discrete heat production distribution in the stacking direction for the practical use of the temperature analysis model. Copyright © 2004 John Wiley & Sons, Ltd.

Coal Cell

This article focuses on coal mining that is incredibly disruptive, and coal is heavy and bulky, involving rumbling freight trains to transport it. The idea that fuel cells are every bit as clean as coal is dirty is just as widespread. Fuel cells, after all, take hydrogen and oxygen, and combine those elements to make electricity and water. The program, called the Clean Coal Technology Program, was, in part, an effort to promote commercial-scale integrated gasification combined-cycle (IGCC) coal power plants in the United States. Molten carbonate fuel cell stacks routinely weigh in at 250 kW. For the Wabash River demonstration, eight stacks will be combined for 2 MW. It will be the largest carbonate fuel cell power plant operating on coal in the world. FuelCell Energy has been planning for this sort of project for more than 20 years.

Life Cycle Assessment of a Molten Carbonate Fuel Cell Stack

AbstractFuel cells are considered to be ultra‐clean energy conversion systems because the pollutants emitted during their operating time are very low in concentration. For this reason, fuel cells can represent the answer to several environmental issues. What is important, however, is to carefully evaluate if the problem is really being solved, or just shifted. In other words, it is vital to consider not only the operating life, but also the pollution related to the construction, the disposal, the conversion of primary fuel into hydrogen and all the other related operations and systems.The present study is the first step for evaluating the environmental impact related to the whole life cycle of a fuel cell system. In this paper, in fact, the authors, making use of the Life Cycle Assessment (LCA) approach, analyze the impact associated with a Molten Carbonate Fuel Cell Stack.Since the MCFC construction can be considered a novel practice, this study can provide a significant indication for pollution reduction in the stack construction phase.

Off-Design Performance Analysis of a Hybrid System Based on an Existing Molten Fuel Cell Stack

This paper addresses the off-design analysis of a hybrid system (HS) based on the coupling of an existing Ansaldo Fuel Cells (formerly Ansaldo Ricerche) molten carbonate fuel cell (MCFC) stack (100 kW) and a micro gas turbine. The MCFC stack model at fixed design conditions has previously been presented by the authors. The present work refers to an off-design stack model, taking into account the influence of the reactor layout, current density, air and fuel utilization factor, CO2 recycle loop, cell operating temperature, etc. Finally, the design and off-design model of the whole hybrid system is presented. Efficiency at part load condition is presented and discussed, taking into account all the constraints for the stack and the micro gas turbine, with particular emphasis on CO2 recycle control.

Verification of a simple numerical fuel cell model in a flowsheeting program by performance testing of a 110 cm 2 molten carbonate fuel cell

This article presents a verification of a simple numerical model that uses the cell resistance as the only experimental parameter. Two methods for determining this experimental parameter are evaluated by comparing the actual measured cell voltages with the calculated cell voltages at various gas utilizations and current loads. Furthermore, the results of the model are compared with the analytical fuel cell model that was previously developed at Delft University. Both the simple numerical model and the analytical fuel cell model use isothermal electrochemical relations for determination of the performances. In order to assess this numerical model for application to non-isothermal molten carbonate fuel cell stacks found in practice, the discrepancy between the results from the isothermal model and the non-isothermal model is discussed. The maximum relative discrepancy between the measured and calculated cell voltage by the numerical model was 3%. This discrepancy was reduced to 1.7% when using a fitted value for the cell resistance. Comparison of the results of the isothermal and non-isothermal models shows that the differences in results can, in general, be neglected.

Manufacture of 1 kW Molten Carbonate Fuel Cell Stack

Manufacture of 1 kW Molten Carbonate Fuel Cell Stack

Theoretical study of a molten carbonate fuel cell stack for pressurized operation

Theoretical study of a molten carbonate fuel cell stack for pressurized operation

Nonlinear modeling and adaptive fuzzy control of MCFC stack

Abstract To improve availability and performance of fuel cells, the operating temperature of molten carbonate fuel cells (MCFC) stack should be controlled within a specified range. However, the most existing models of MCFC are not ready to be applied in synthesis. In this paper, a radial basis function neural networks identification model of MCFC stack is developed based on the input–output sampled data. A novel adaptive fuzzy control procedure for the temperature of MCFC stack is also developed. The parameters of the fuzzy control system are regulated by back-propagation algorithm, and the rule database of the fuzzy system is also adaptively adjusted by the nearest-neighbor-clustering algorithm. Finally using the neural networks model of MCFC stack, the simulation results of the control algorithm are presented. The results show the effectiveness of the proposed modeling and design procedures for MCFC stack based on neural networks identification and the novel adaptive fuzzy control.

Pressure losses at dividing and combining junctions in a molten carbonate fuel cell stack

The pressure losses at manifold junctions in a molten carbonate fuel cell (MCFC) stack depend on the stacking positions of the cells and the flow rate in the manifold. These pressure losses affect the uniformity of gas flow rate in each stacked cell and consequently also affect the cell performance. In this study, the pressure losses at dividing and combining junctions in a plate heat-exchanger type MCFC stack were examined by numerical analysis. A stack consisting of 100 cells was assumed, and the junction pressure losses at various stacking positions of cells were calculated under various flow rate conditions ranging from the minimum possible flow rate (80% utilization of fuel gas) to the maximum possible flow rate (10% utilization of oxidant gas). The results were arranged according to the equations for loss coefficients, and were compared with the experimental results of previous studies.

Analysis of temperature and pressure fields in molten carbonate fuel cell stacks

AbstractA mathematical model based on fluid dynamics and heat‐transfer theories was applied to predict gas dynamic pressure and temperature distribution in a coflow molten carbonate fuel cell (MCFC) stack. The mass balance was simplified to obtain exact solutions with an assumption of uniform current density in the cell. The simulations were compared with data from a pilot‐scale MCFC stack. The effect of internal geometry of gas channels was simulated to accurately predict the gas‐pressure drop. A close prediction of pressure drop was possible from a partially blocked gas channel model that approximates the significant flow resistance. The effect of external boundary conditions on stack temperature profile was also analyzed. Temperatures were accurately predicted from a boundary heat conduction model with a reasonable assumption of wet seal temperatures. The 2‐D boundary conditions could be extended to 3‐D simulations to predict temperature distribution with the same accuracy. The model was applied to see the effect of scale‐up on the maximum temperature rise and average cell potential. The result verified a significant effect of cell size on the maximum stack temperature.

Theoretical study of a molten carbonate fuel cell stack for pressurized operation

A mathematical stack model of a molten carbonate fuel cell was numerically solved for temperature, gas dynamic pressure, and cell performance. The model assumed a steady state, constant load operation for a co-flow stack with an external reformer. The numerical computation was done for a two-dimensional domain with a real size of cell specifications. The effect of two stack operation variables, gas utilization and system pressure, was thoroughly analysed. The computation results were demonstrated in the form of flow fields, temperature contours, axial profiles, and plots of characteristic values. Our analysis began with an underlying fact that a high cathode gas flow is necessary for stack temperature control. The analysis result verified the effect of stack cooling by the cathode gas, and showed various aspects of stack operation and performance under pressurization. The pressurization effect is most significant in a moderate pressure range of 1–5 atm. The gas dynamic pressure, as it inevitably increases at a high gas flow rate, is regulated by pressurization. All the pressurization effects can generally be represented using a dimensionless parameter, named a pressurization factor. The relation between gas dynamic pressure and total system pressure was clarified from the related flow equations. Copyright © 2001 John Wiley & Sons, Ltd.