Molten Carbonate Fuel Cell Research Articles

Optimization of molten carbonate fuel cell (MCFC) and homogeneous charge compression ignition (HCCI) engine hybrid system for distributed power generation

In a previous study, a new hybrid system of molten carbonate fuel cell (MCFC) and homogeneous charge compression ignition (HCCI) engine was developed, where the HCCI engine replaces the catalytic burner and produces additional power by using the left-over heating values from the fuel cell stack. In the present study, to reduce the additional cost and footprint of the engine system in a hybrid configuration, the possibility of engine downsizing is investigated by using two strategies, i.e. the use of a turbocharger and the use of high geometric compression ratio for the engine design, both of which are to increase the density of the intake charge and thus the volumetric efficiency of the engine. Combining these two strategies, we suggest a new engine design with ∼60% of displacement volume of the original engine. In addition, operating strategies are developed to run the new hybrid system under part load conditions. It is successfully demonstrated that the system can operate down to 65% of the power level of the design point, while the system efficiency remains almost unchanged near 63%.

A unified model of high-temperature fuel-cell heat-engine hybrid systems and analyses of its optimum performances

On the basis of the models of various developed high-temperature fuel-cell heat-engine hybrid systems, a unified model of hybrid systems is proposed. General expressions for the power output and efficiency of hybrid systems, high-temperature fuel cells such as solid oxide fuel cells (SOFCs) and molten carbonate fuel cells (MCFCs), and heat engines including the Brayton, Otto, Diesel, Atkinson, Braysson, and Carnot engines are, respectively, derived by using the theories of electrochemistry and non-equilibrium thermodynamics. The effects of main irreversible losses existing in real fuel cells and heat engines on the performance of hybrid systems are investigated. The general performance characteristics and optimal operating regions of some of the key parameters of hybrid systems are discussed in detail. A variety of special typical cases are discussed. The important results in the literature can be readily reproduced, and the interesting findings of our study are presented.

Performance optimum analysis of an irreversible molten carbonate fuel cell–Stirling heat engine hybrid system

A new hybrid system mainly consists of a molten carbonate fuel cell (MCFC) and a Stirling heat engine is established, where the Stirling heat engine is driven by the high-quality waste heat generated in the MCFC. Based on the electrochemistry and non-equilibrium thermodynamics, analytical expressions for the efficiency and power output of the hybrid system are derived by taking various irreversible losses into account. It shows that the performance of the MCFC can be greatly enhanced by coupling a Stirling heat engine to further convert the waste heat for power generation. By employing numerical calculations, not only the influences of multiple irreversible losses on the performance of the hybrid system are analyzed, but also the impacts of some operating conditions such as the operating temperature, input gas compositions and operating pressure on the performance of the hybrid system are also discussed. The investigation method in the present paper is feasible for some other similar energy conversion systems as well.

Molten carbonate fuel cell: Towards negative emissions in wastewater treatment CHP plants

Wastewater treatment produces biogas fuel, commonly used for cogeneration in reciprocating engines, though small scale gas turbines can also be employed. In all cases, the carbon dioxide released through combustion is not regarded as a net greenhouse gas emission since the carbon content in the biogas has a natural origin. In light of that, it is possible to achieve negative carbon footprints as long as a carbon sequestration system is used and its corresponding emissions do not exceed the amount of carbon dioxide sequestered.As opposed to conventional carbon capture systems, featuring an energy consumptions in the range 1.4–6MJ/kg CO2 sequestered, molten carbonate fuel cells (MCFC) are able to capture CO2 generating electricity simultaneously. The downside of MCFC is their high costs and still ongoing industrialisation that have prevented its commercial deployment. However the current activities developed by manufacturers and researchers anticipate a reduction of both capital and operational costs in the mid-term.This paper provides a techno-economical comparison between conventional CHP technologies (reciprocating engines and gas turbines) and innovative solutions comprising MCFCs fed with biogas produced in wastewater plants. The thermodynamic and environmental analyses are focused on the CHP facility. An economic evaluation of the proposed solutions is done using the Monte Carlo method in order to identify the most cost-effective system, keeping into account uncertainties related to the key parameters of the scenario.

Mechanistic Mathematical Model for Deactivation of Catalysts in Direct Internal Reformer in Molten Carbonate Fuel Cells

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Corrosion Behavior of Cathode Current Collector Materials On Molten Carbonate Fuel Cell

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Electrochemical Impedance Spectroscopy Studies of Corrosion of Two-phase Ni-Dy Alloys in Molten (0.62Li,0.38K)2CO3 at 650 °C

AbstractThe dissolution of the NiO cathodes and the corrosion of bipolar plates are great obstacles to the commercialization of molten carbonate fuel cells (MCFC). Rare earth element dysprosium is effective in inhibiting the corrosion of Ni in molten carbonates. In this presentation, electrochemical impedance spectroscopy was employed to study the corrosion behavior of two-phase Ni-Dy alloys containing 1 and 3 wt.% Dy, respectively, in molten (0.62Li,0.38K)2CO3 at 650 °C in air. The experimental results indicate that the Nyquist plots for the corrosion of both Ni-1Dy and Ni-3Dy are all composed of a small capacitive loop at high frequencies and a line at low frequencies, but with larger impedance values for Ni-3Dy. The emergence of Warburg impedance at low frequencies suggests that the corrosion of alloys is controlled by the diffusion of oxidants in molten carbonates, as observed for pure nickel. The addition of dysprosium to nickel can decrease its corrosion rate, with a better effectiveness for the 3% Dy addition. Based on the diffusion impedance, the oxidants involved in corrosion are also discussed.

The Scale Up Characteristics of a Catalytic Combustor With Flow Uniformity Analysis

Catalytic combustors are used as off-gas combustors of molten carbonate fuel cells (MCFCs) because of their exhaust gas purity, geometric flexibility, and high combustion efficiency. In this study, a new design was investigated for possible application in internally reformed MCFC. The study started with performance analysis of a 5 kWe combustor, which could be precisely conducted due to availability of experimental apparatus. A 5 kWe combustor was used as a model combustor, and it was experimentally analyzed in terms of flow uniformity, catalyst screening, and reaction characteristics. The results show that the flow uniformity is able to reduce the exhaust gas concentration because temperature uniformity decreases the possibility of fuel slippages in locally lower temperature zones. As the capacity of the combustor is increased from 5 kWe to 25 kWe, the exhaust gas temperature at the same inlet condition as that of the 5 kWe combustor increases due to lower heat loss. As a result, the catalyst screening process shows different results due to higher operating temperatures, but three of four catalysts provide proper quality. On the other hand, flow uniformity improves economic competitiveness of the catalytic combustor. When the volume loading of catalytic monoliths was decreased, the performance was very similar to that of the original volume loading of catalytic monoliths.

Development of Solid Oxide Fuel Cells at Versa Power Systems and Fuel Cell Energy

Versa Power Systems (VPS) is a developer of solid oxide fuel cells (SOFCs) for clean power generation and was recently acquired by FuelCell Energy (FCE). FCE is a global leader in the design, manufacture and distribution of Molten Carbonate Fuel Cell (MCFC) power plants. From an economic perspective, MCFCs scale-up very well and as a result FCE’s MCFC products are in the multi-megawatt size range. SOFCs are complementary because they scale-down well and hence are well suited to sub-megawatt applications. This paper highlights the status of VPS and FCE’s SOFC technology in the areas of cell, stack and system development.

Experimental investigation of CO2 separation from lignite flue gases by 100 cm2 single Molten Carbonate Fuel Cell

The paper presents an experimental investigation of using a Molten Carbonate Fuel Cell (MCFC) to reduce CO2 emission from the flue gas of a lignite fired boiler. The MCFC is placed in the flue gas stream and separates CO2 from the cathode side to the anode side. As a result, a mixture of CO2 and H2O is obtained from which pure CO2 can be obtained through condensation of water and carbon dioxide. The main advantages of this solution are: additional electricity generated, reduced CO2 emissions and higher system efficiency. The results obtained show that the use of an MCFC could reduce CO2 emissions by 90% with over 30% efficiency in additional power generation.

Characterizations of polybenzimidazole based electrochemical hydrogen pumps with various Pt loadings for H2/CO2 gas separation

Carbon capture and storage (CCS) technologies have been intensively researched and developed to cope with climate change, by reducing atmospheric CO2 concentration. The electrochemical hydrogen pumps with phosphoric acid doped polybenzimidazole (PBI) membrane are evaluated as a process to concentrate CO2 and produce pure H2 from anode outlet gases (H2/CO2 mixture) of molten carbonate fuel cells (MCFC). The PBI-based hydrogen pump without humidification (160 °C) can provide higher hydrogen separation performances than the cells with perfluorosulfonic-acid membranes at a relative humidity of 43% (80 °C), suggesting that the pre-treatment steps can be decreased for PBI-based systems. With the H2/CO2 mixture feed, the current efficiency for the hydrogen separation is very high, but the cell voltage increase, compared to the pure hydrogen operation, mainly due to the larger polarization resistance at electrodes, as confirmed by electrochemical impedance spectroscopy (EIS). The performance evaluation with various Pt loadings indicates that the hydrogen oxidation reaction at anodes is rate determining, and therefore the Pt loading at cathodes can be decreased from 1.1 mg/cm2 to 0.2 mg/cm2 without significant performance decay. The EIS analysis also confirms that the polarization resistances are largely dependent on the Pt loading in anodes.

Development of a Hybrid System of Molten Carbonate Fuel Cell and Homogeneous Charge Compression Ignition Engine for Distributed Power Generation

A new hybrid system of molten carbonate fuel cell (MCFC) and homogenous charge compression ignition (HCCI) engine is suggested to improve the overall system efficiency and performance. In the proposed system, the catalytic burner in a standalone MCFC system is replaced with the HCCI engine. The HCCI engine is chosen over conventional spark-ignition or compression-ignition engines since it has been demonstrated to operate with highly diluted reactant mixture, which is suitable to run directly with the MCFC anode off-gas. A nonisothermal numerical model that incorporates major fuel cell losses is developed to predict the fuel cell performance. The fuel cell model assumes parallel anode and cathode flow configuration with LiNaCO3 as an electrolyte. It is integrated with an in-house HCCI engine model to investigate the hybrid system performance. At the selected design point operation around 300 kW power output, the maximum hybrid system efficiency is 21.2% (relative) higher than that of a standalone fuel cell system and, thus, achieving around 60% overall, which demonstrates the potential of the suggested hybrid system as a highly-efficient distributed power generation source in the near future.

Removal of H2S using molten carbonate at high temperature

Gasification is considered to be an effective process for energy conversion from various sources such as coal, biomass, and waste. Cleanup of the hot syngas produced by such a process may improve the thermal efficiency of the overall gasification system. Therefore, the cleanup of hot syngas from biomass gasification using molten carbonate is investigated in bench-scale tests. Molten carbonate acts as an absorbent during desulfurization and dechlorination and as a thermal catalyst for tar cracking. In this study, the performance of molten carbonate for removing H2S was evaluated. The temperature of the molten carbonate was set within the range from 800 to 1000°C. It is found that the removal of H2S is significantly affected by the concentration of CO2 in the syngas. When only a small percentage of CO2 is present, desulfurization using molten carbonate is inadequate. However, when carbon elements, such as char and tar, are continuously supplied, H2S removal can be maintained at a high level.To confirm the performance of the molten carbonate gas-cleaning system, purified biogas was used as a fuel in power generation tests with a molten carbonate fuel cell (MCFC). The fuel cell is a high-performance sensor for detecting gaseous impurities. When purified gas from a gas-cleaning reactor was continuously supplied to the fuel cell, the cell voltage remained stable. Thus, the molten carbonate gas-cleaning reactor was found to afford good gas-cleaning performance.

A Cylindrical Molten Carbonate Fuel Cell Supplied with Landfill Biogas

A small size cylindrical Molten Carbonate Fuel Cell stack was installed at Giugliano landfill in Italy. The stack was constituted by 16-cells with a 300 W nominal power. Preliminary tests were performed in order to verify the possibility to supply the stack by the landfill biogas, characterized by low methane content (32%). Results showed that the proposed plant is able to correctly operate also when supplied with low methane content biogas.

고온 연료전지 발전단지의 내부계통 고장에 의한 운전환경에 대한 분석

High temperature fuel cell system, such as molten carbonate fuel cells(MCFC) and solid oxide fuel cells(SOFC), are capable of operating at MW rated power output. The power output change of high temperature fuel cell imposes the thermal and mechanical stresses on the fuel cell stack. To minimize the thermal-mechanical stresses on the stack, increases in the power output of high temperature fuel cell typically must be made at a slow rate. So, the short time interruption of high temperature fuel cell causes considerable generated energy losses. Because of the characteristic of high temperature fuel cell, we analyzed the impact of electrical fault in the fuel cell plant on other fuel cell generators in the same plant site. A various grounding configuration and voltage sag are analyzed. Finally, we presented the solution to minimize the effect of fault on other fuel cell generators.

TiO2 protective coating processed by Atomic Layer Deposition for the improvement of MCFC cathode

One of the main issues for optimizing the molten carbonate fuel cell (MCFC) is the control of the corrosion and dissolution of the state-of-the-art porous nickel oxide cathode. A protective coating constituted by more stable oxides seems to be the best solution. In this paper, very thin layers of TiO2 (50 and 300 nm) are processed by a sequential CVD technique, Atomic Layer Deposition (ALD), which produces high quality, homogeneous and conformal layers. Structural, morphological and electrochemical behaviors of TiO2-coated samples are tested in a Li2CO3–K2CO3 (62:38 mol%) eutectic melt under a standard cathode atmosphere: CO2/air (70:30 bar%). Ni solubility is determined by ICP-AES. The protective role of TiO2 layers and the consequent decrease in Ni solubility have been clearly evidenced.

Research of Molten Carbonate Fuel Cells Modeling Based on Neural Computing

The molten carbonate fuel cell (MCFC) is an important research field of the new energy generation equipment, and is a difficulty in the research field of high-temperature fuel cells at present. To aim at the MCFC modeling problem, the MCFC electrochemical mechanism process was analyzed firstly, then the MCFC modeling applied neural computing is advanced. Thirdly, the structure, algorithm and simulation of MCFC modeling based on feedback neural networks were presented in detail. Finally, the computer simulation and conducted experiment verified that this model was fast and accurate, and can be as a suitable operational model of MCFC real-time control.

Experimental Investigation of CO<sub>2</sub> Separation from Lignite Flue Gases by 100 cm<sup>2</sup> Single Molten Carbonate Fuel Cell

The paper presents an experimental investigation of using a Molten Carbonate Fuel Cell (MCFC) for reducing CO2 emission from the flue gas of a lignite boiler. The MCFC is placed in the flue gas stream and separates CO2 from the cathode side to the anode side. As a result, a mixture of CO2 and H2O is obtained; from which pure CO2 can be obtained by cryogenic condensation of water and carbon dioxide. The main advantages of this solution are: additional electricity generated, reduced CO2 emissions and higher system efficiency. The results obtained show that the use of an MCFC could reduce CO2 emissions by 90% with over 30% efficiency in additional power generation.

Fuel Cells: Technologies and Applications

A deep analysis of the Fuel Cells technologies state of the art has been done in this article. After a general de- scription of the fuel cell base structure the six most important fuel cell technologies Polymeric Electrolyte Membrane Fuel Cells (PEMFC), Direct Methanol Fuel Cells (DMFC), Alkaline Fuel Cells (AFC), Phosphoric Acid Fuel Cell (PAFC), Molten Carbonate Fuel Cell (MCFC), Solid Oxide Fuel Cell (SOFC) are explained, describing advantages and disadvan- tages of each one and pointing out their principal use. The future development are also shown.

A reduced order model of Molten Carbonate Fuel Cell: A proposal

The mathematical model of the Molten Carbonate Fuel Cell (MCFC) is presented. The new approach for modeling the voltage of MCFC is proposed. Electrochemical, thermal, electrical and flow parameters are collected in the 0-D mathematical model. The aim was to combine all cell working conditions in as a low number of factors as possible and to have the factors relatively easy to determine. A validation process for various experimental data was made and adequate results are shown. The presented model was validated for various fuel mixtures in relatively wide ranges of parameters. A distinction is made between the “design-point” and “off-design operation”.