Molten Carbonate Fuel Cell System Research Articles

Performance and Stability of Molten Carbonate Fuel Cell Cathode Electrode Under Carbon Capture Endurance Tests

Introduction The molten carbonate fuel cell (MCFC) has emerged as one of the promising alternatives for carbon capture from industrial and power generation CO2 sources. MCFC technology is less energy-intensive compared to conventional amine scrubbing that requires a significant amount of energy (steam) for solvent regeneration process.MCFC has been commercially used for distributed power generation, however its use in carbon capture applications has been limited to development activities and a few demonstrations during the past decades. The electrochemical reactions taking place during cell operation involve the CO2 transfer from cathode to anode in the form of carbonate ions resulting in a gas stream with high CO2 concentration on the anode exhaust. Therefore, MCFC stack systems can be combined with conventional combustion-powered generators (coal and/or natural gas-based power plants) for simultaneous CO2 separation, power and hydrogen generation.CO2 capture applications will typically take in flue gas from industrial furnaces, coal and gas fired combined cycle plants as the cathode inlet gas stream having low CO2 concentrations ranging from 4% to 10% by volume and high CO2 utilization (>90%). These CO2-lean conditions may pose a challenge for attaining good mass-transfer performance and life stability, therefore innovative approaches are needed in terms of hardware design and cathode structure to achieve long-term stability.FCE has tested numerous single cells (250 cm2) and technology stacks (30 kW) under carbon capture operating conditions (4-8% CO2 in the cathode inlet as opposed to >12% in baseline MCFC systems) to understand impact of design parameters on performance, life, and to investigate design solutions for further enhancement. Figure 1 highlights the effect of cathode water content on CO2 utilization. It appears that differences exist between the ideal and measured CO2 utilizations, indicating that less CO2 is transferring from the cathode to anode than expected. This CO2 transference reduction becomes more pronounced with higher water concentration, suggesting that a species other than CO3 2- ion, likely hydroxide (OH- ion), may be generated and transported through the electrolyte matrix.This paper will review the cathode material stability and electrochemical performance under long-term carbon-capture operation. The effect of parameters such as water content, gas composition, utilization, and electrolyte chemistry, as well as approaches to enhance the CO2 capture efficiency and life, will be discussed. Figure 1

Environmental and economic analyses of fuel cell and battery-based hybrid systems utilized as auxiliary power units on a chemical tanker vessel

This study aims to investigate the environmental and economic impacts of implementing fuel cell and battery-based hybrid configurations. Phosphoric acid and molten carbonate fuel cell systems in the place of diesel generators of a large tanker to supply the vessel's total electricity demand. Environmental and economic analyses of the utilization of the specified fuel cell systems with LiNiCoALO2 and LiNiMnCoO2 chemical types of battery cells on a large marine vessel are provided in this paper. In addition, the assessment of the most suitable battery cell and charge-discharge hours for fuel cell systems is carried out with a grid-search algorithm. Six different fuel cell and battery configurations are investigated to obtain the optimum system layout. The results show that the CO2 emissions could be reduced by up to 49.75% and the lowest electricity production cost is found as 0.181 $/kWh for the current fuel prices with the utilization of molten carbonate fuel cells and LiNiMnCoO2 battery cells.

Fuel cell integrated carbon negative power generation from biomass

Combining biomass-fuelled power plant with carbon capture and storage allows CO2 to be removed from the atmosphere, considering biomass a carbon–neutral fuel. In the present study, a biomass-based CO2 negative system has been proposed, which combines a biomass steam gasification facility with a solid oxide fuel cell, a post-combustion carbon capture facility with a molten carbonate fuel cell (MCFC), and waste heat recovery using the organic Rankine cycle. A techno-economic analysis of two scenarios, namely a) with MCFC-based CO2 capture and b) without CO2 capture, was conducted. Integration of MCFC and carbon capture system was able to capture 99.2% of CO2. It was found that the energy efficiency of the system was decreased by 9.43%, with the incorporation of CO2 capture facilities. Furthermore, exergy efficiencies for the configuration with CO2 capture and without CO2 capture are calculated as 62% and 70.22%, respectively. The economic analysis reveals that the levelized cost of electricity (LCOE) for the configuration with CO2 capture and without CO2 capture is estimated to be 0.062 $/kWh and 0.052 $/kWh, respectively. Finally, life cycle CO2 emissions for both the scenarios have been performed, and the analysis reveals that the proposed CO2 negative system is able to capture 1100 tonnes of CO2 per year.

Integration of molten carbonate fuel cell and looped multi-stage thermoacoustically-driven cryocooler for electricity and cooling cogeneration

Thermal management is essential for high-temperature molten carbonate fuel cell (MCFC) because the accumulated waste heat may degrade the durability. In this paper, looped multi-stage thermoacoustically-driven cryocooler (LMTC) is proposed to reuse the waste heat from MCFC for cooling production, which not only can tackle with the thermal management issue but also can provide additional usages. Accounting various irreversible dissipation, the models of MCFC, LMTC and MCFC-LMTC hybrid system are analytically formulated. Performance features of MCFC-LMTC hybrid system are revealed and the advantages are expounded via calculation examples. Calculations indicate that the maximum power density and corresponding efficiency of the hybrid system are 1688.9 W m−2 and 39.7%, which are 11.4% and 1.3% bigger than that of the sole MCFC system, respectively. By comparing with other available systems, the superiority of using LMTC to recover MCFC waste heat for refrigeration is clearly demonstrated. Considerable parametric studies show that the heat-transfer coefficient of hot heat exchange for LMTC is not suggested to be greater than 2.5 × 10−3 W m−2 K−1. In addition, an increase in the working temperature, working pressure of MCFC, reactant concentration or engine stage number of LMTC positively benefits the hybrid system performance, while an increase in the thermodynamic loss coefficient worsens the hybrid system performance. The obtained results may offer new insights into improving the performance of MCFCs through thermal management approaches.

Performance evaluation of a novel CCHP system integrated with MCFC, ISCC and LiBr refrigeration system

This paper proposes a novel combined cooling, heating, and power (CCHP) system integrated with molten carbonate fuel cell (MCFC), integrated solar gas-steam combined cycle (ISCC), and double-effect absorption lithium bromide refrigeration (DEALBR) system. According to the principle of energy cascade utilization, part of the high-temperature waste gas discharged by MCFC is led to the heat recovery steam generator (HRSG) for further waste heat utilization, and the other part of the high-temperature waste gas is led to the MCFC cathode to produce CO32−, and solar energy is used to replace part of the heating load of a high-pressure economizer in HRSG. Aspen Plus software is used for modeling, and the effects of key factors on the system performances are analyzed and evaluated by using the exergy analysis method. The results show that the new CCHP system can produce 494.1 MW of electric power, 7557.09 kW of cooling load and 57,956.25 kW of heating load. Both the exergy efficiency and the energy efficiency of the new system are 61.69% and 61.64%, respectively. Comparing the research results of new system with similar systems, it is found that the new CCHP system has better ability to do work, lower CO2 emission, and can meet the cooling load, heating load and electric power requirements of the user side at the same time.

Department of Defense Molten Carbonate Fuel Cell Demonstrations

Demonstration of molten carbonate fuel cells (MCFC) is underwayat three Department of Defense (DOD) sites. LOGANEnergy (LOGAN)has received contracts to install four MCFC systems at the three DODsites. The four 250-kW MCFC systems will be model DFC300MA unitsmanufactured by FuelCell Energy (FCE). The projects are still in-prog-ress but are already producing valuable experience. Experience to dateis shared in this article

Economic and environmental impact assessments of hybridized aircraft engines with hydrogen and other fuels

Hybridized engines have become the focus of research nowadays in order to update the existing engines in different transportation sectors. This paper presents a hybridized aircraft engine consisting of a molten carbonate fuel cell system and a commercial turbofan system. The MCFC units are connected to a steam reforming and a water gas shift system. Also, five clean fuels are selected, such as dimethyl ether, hydrogen, ethanol, methane, and methanol, which are combined with different mass ratios to form five different fuel blends. The hybridized aircraft is investigated using three approaches: exergy analysis, exergoeconomic analysis, and exergoenvironmental analysis. It is found that the proposed engine has an average exergetic efficiency of 88% and an average exergy destruction ratio of 12%. The specific exergetic cost of electricity of the engine has an average value of 710 $/GJ for the high-pressure turbine and 230$/GJ for the intermediate and low-pressure turbines, as well as 50 $/GJ for the MCFC. The average specific exergoenvironmental impact of electricity is 14 mPt/MJ for turbines and 4 mPt/MJ for the MCFC. In addition, a blend of ethanol and hydrogen appears to be a viable option economically and environmentally.

Stand-alone gas turbine and hybrid MCFC and SOFC-gas turbine systems: Comparative life cycle cost, environmental, and energy assessments

The life cycle cost, environmental, and energy performances of gas turbine (GT) hybridization with two high-temperature fuel cells, solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC), were investigated in detail. The purpose of the present study is to assess the feasibility of the hybridization based on a throughout comparative investigation between 10-MW GT, MCFC-GT, and SOFC-GT systems in their optimum conditions. A model for SOFC, MCFC, and combustion processes was developed using the Gibbs minimization method through Lagrange multipliers. This model calculates unreformed methane during the methane reforming process occurring within the fuel cells. In addition, it calculates pollutant gases emission rates caused by combustion (i.e. NO, NO2, CO2). The economic analysis of the systems was based on the life cycle-costing P1-P2 method which considers fuel and investment costs. The Genetic algorithm was utilized for single- and multi-objective optimization purposes in different cases. Also, a comprehensive sensitivity analysis was conducted to compare the three systems in their optimum conditions to guarantee results obtained from the optimization scenario. The findings revealed that the SOFC was the best candidate for the GT system hybridization. This hybridization reduced the system investment and fuel costs, and CO2 and NO emissions in the fixed power conditions. The maximum energy efficiency of the GT, MCFC-GT, and SOFC-GT systems was obtained to be 43.8%, 53.8%, and 70.3%, respectively. The minimum values for the CO2 emission of the stand-alone GT, the hybrid MCFC-GT, and the hybrid SOFC-GT systems were 460.8 kg/MWh, 367.9 kg/MWh, and 280.4 kg/MWh, besides NO emission was calculated 13.9 kg/MWh, 1.3 kg/MWh, and 1.2 kg/MWh, respectively. The least life cycle cost of the stand-alone GT, the hybrid MCFC-GT, and the hybrid SOFC-GT systems was 163.6, 160.7, and 106 million dollars, respectively.

Thermodynamic and Economic Analysis of State-of-the-Art Reversible SOFC-SOEC Systems Using Stable Rare-Earth Nickelate Oxygen Electrodes

Gaia Energy Research Institute (Gaia) will present a preliminary thermodynamic and techno-economic analysis of a state-of-the-art (SOA) reversible solid oxide electrolyzer (SOE) using stable rare-earth nickelate oxygen electrodes. Part of the significance of this work is that it quantifies the potential future cost of producing extremely pure hydrogen and oxygen using SOA reversible SOEs in dollars per kilogram of hydrogen ($/kg H2) and oxygen ($/kg O2). This work also analyzes the impact of thermal storage on increasing reversible SOE round-trip efficiency, and the value of electrochemically-compressing the H2 and O2.Primary cost drivers of solid oxide fuel cells (SOFC) systems tend to include the power density of the SOFC stack. Primary cost drivers of SOE systems tend to include (1) system capital costs and (2) the electricity consumed per unit of hydrogen / oxygen produced. In SOEs, electricity consumption can be displaced by heat consumption. In a combined reversible SOE system, heat produced by the SOFC can be stored and reused to provide heat to the SOE. The extent of this heat reuse is estimated to be a primary cost driver, because for every unit of electricity input displaced by reused heat as an input, the SOE produces more hydrogen and oxygen per unit of electricity input. Heat reuse by the reversible SOE can increase the hydrogen and oxygen output per unit of electricity by up to ~30%. Efficient design of this heat reuse subsystem is crucial to the reversible SOE achieving round-trip efficiencies of >70%, a necessity for viability in the long-duration energy storage market. The work examines the primary cost drivers for the reversible SOE system, including the heat storage and reuse subsystem. This research effort considers valid heat storage media including, but not limited to, (1) the ceramic materials of the reversible SOE stack, (2) steam exhausted from the SOE stack (in the same stream as the hydrogen but with the hydrogen potentially electrochemically separated at high temperature via proton-conducting ceramics), and (3) phase change materials, such as molten salts.The reversible SOE stack being evaluated is a unique, all-ceramic stack, and therefore, the materials of the stack have the potential to maintain greater stability as a thermal storage media compared with stacks composed of multiple material types each with potentially quite different thermal expansion coefficients. A primary failure mechanism of high temperature electrochemical systems is a mismatch in thermal expansion coefficients of electrochemical stack materials. For example, historically, the FuelCell Energy Inc. stationary, commercial Molten Carbonate Fuel Cell (MCFC) system has been limited to a turn down ratio of only 12% of maximum rated power over the course of one (1) hour, primarily due to mismatches in the thermal expansion coefficients of its MCFC stack materials.The all-ceramic reversible SOE stack evaluated here is also unique in that it has the capacity to supply hydrogen and oxygen at pressure. This analysis also quantifies the value of this electrochemically-compressed hydrogen and oxygen, compared with hydrogen and oxygen produced by mechanical compression. Based on techno-economic analyses of electrochemical and mechanical compression, electrochemical compression has the most compelling cost advantage over mechanical compression in the lower pressure range (i.e., for example, 1 to 100 bar). Electrochemical compression appears to have the highest theoretical efficiency advantage over mechanical compression across a larger pressure range going up to very high pressures (1 bar to 900 bar). When practical, measured, in-use efficiencies are considered, electrochemical compression appears to have a substantial potential advantage over mechanical compression in part because mechanical compression systems are often not designed to maintain high efficiencies at lower throughputs and are limited in their turn-down ratio (in some cases, their turn-down ratio is limited to only 25% of maximum flow rate.) Electrochemical compression with an all-ceramic stack is estimated to be less limited in response time and less limited in turn-down ratio due to more uniform thermal expansion coefficients, compared with some mechanical compressor systems built today.Model results indicate that the reversible SOE is expected to produce hydrogen at less than $2/kg H2, which is the DOE Fuel Cell Technologies Office (FCTO) H2 production cost target. Model results further indicate that, between near-term and far-term cases, the estimated energy storage costs are expected to decline due to decreases in (1) the reversible SOE system capital costs (mainly at the stack), (2) net system-wide energy consumption, (3) the extent of waste heat dissipated by the system, and (4) operations and maintenance costs. Energy storage costs are also analyzed using single-variable sensitivity studies and Tornado charts.

Low-carbon hydrogen via integration of steam methane reforming with molten carbonate fuel cells at low fuel utilization

Hydrogen production is critical to many modern chemical processes – ammonia synthesis, petroleum refining, direct reduction of iron, and more. Conventional approaches to hydrogen manufacture include steam methane reforming and autothermal reforming, which today account for the lion's share of hydrogen generation. Without CO2 capture, these processes emit about 8.7 kg of CO2 for each kg of H2 produced. In this study, a molten carbonate fuel cell system with CO2 capture is proposed to retrofit the flue gas stream of an existing Steam Methane Reforming plant rated at 100,000 Nm3 h−1 of 99.5% pure H2. The thermodynamic analysis shows direct CO2 emissions can be reduced by more than 95%, to 0.4 to 0.5 kg CO2/kg H2, while producing 17% more hydrogen (with an increase in natural gas input of approximately 37%). Because of the additional power and hydrogen generation of the carbonate fuel cell, the efficiency debit associated with CO2 capture is quite small, reducing the SMR efficiency from 76.6% without capture to 75.6% with capture. In comparison, the use of standard amine technology for CO2 capture reduces the efficiency below 70%. This demonstrates the synergistic nature of the carbonate fuel cells, which can reform natural gas to H2 while simultaneously capturing CO2 from the SMR flue gas and producing electricity, giving rise to a total system with very low emissions yet high efficiency.

Life cycle assessment of molten carbonate fuel cell system for power plants

This study evaluated the environmental impacts of a 2.5 MW molten carbonate fuel cell (MCFC) system on impact categories such as climate change (CC), abiotic resource depletion (ARD), acidification (AC), and eutrophication (EU) using a life cycle assessment (LCA) methodology with the functional unit of 1 kWh electricity. Because MCFC systems produce electricity and heat simultaneously, the allocation was performed based on the amounts of exergy contents between electricity and heat (0.636 and 0.364, respectively). The impact on CC, expressed in global warming potential (GWP), was estimated as 3.53E-01 kg CO2 eq./kWh, while the impact on ARD was 1.90E-03 kg Sb eq./kWh, the impact on AC was 3.05E-04 kg SO2 eq./kWh, and the impact on EU was 1.35E-05 kg PO43− eq./kWh. The main cause for the impact on CC was found to be the reforming of liquefied natural gas in the operation stage. For the other categories (ARD, AC, and EU), the contributions of the operation stage were also over 80%. A comparison of the MCFC system with the Korean grid mix showed that the environmental impacts of the grid mix were larger than those of the MCFC system. Several improvement strategies were simulated to reduce the GWPs. First, to improve the efficiency of the heat exchanger, instead of using the heat generated by the MCFC system to produce high-temperature steam as is currently done, the generated heat was proposed to be used to produce medium or low-temperature water. This change reduced the GWPs of the MCFC by approximately 1.72E-02 kg CO2 eq./kWh. Second, this study simulated with an improved electricity production efficiency, with an increase from its current level (45%) to the theoretical maximum value of 60%. This improvement achieved a reduction of approximately 4.00E-02 kg CO2 eq./kWh. Finally, the electricity production efficiency was further increased using unreacted hydrogen, resulting in a reduction of 2.70E-02 kg CO2 eq./kWh.

A feasibility assessment of a retrofit Molten Carbonate Fuel Cell coal-fired plant for flue gas CO2 segregation

This work considers the use of a Molten Carbonate Fuel Cell (MCFC) system as a power generation and CO2 concentrator unit downstream of the coal burner of an existing production plant. In this way, the capability of MCFCs for CO2 segregation, which today is studied primarily in reference to large-scale plants, is applied to an intermediate-size plant highlighting the potential for MCFC use as a low energy method of carbon capture. A technical feasibility analysis was performed using an MCFC system-integrated model capable of determining steady-state performance across varying feed composition. The MCFC user model was implemented in Aspen Custom Modeler and integrated into the reference plant in Aspen Plus. The model considers electrochemical, thermal, and mass balance effects to simulate cell electrical and CO2 segregation performance. Results obtained suggest a specific energy requirement of 1.41 MJ kg CO2−1 significantly lower than seen in conventional Monoethanolamine (MEA) capture processes.

Effect of Carbon Capture Endurance Conditions on Performance and Stability of Molten Carbonate Fuel Cell Cathode Electrode

IntroductionThe molten carbonate fuel cell (MCFC) is one of the most advanced high-temperature and clean power generating devices. To date >8 billion kWh of electricity has been produced commercially using this new technology. The high operating temperature of MCFC (550-650 °C) dramatically improves the reaction kinetics and eliminates the need for a noble metal catalyst. The electrochemical reactions taking place during cell operation involve the CO2 transfer from cathode to anode in the form of carbonate ions (Figure 1). Therefore, MCFC stack technology can be used for power generation and simultaneously, as an effective CO2 separator. MCFC systems can be combined with conventional combustion-powered generators (coal and/or natural gas based power plants) to efficiently separate CO2 in the exhaust gas and produce additional electricity.The state of the art MCFC cathode is porous lithiated nickel oxide. The cathode stability and performance are affected by several factors such as gas composition, temperature, electrode structure and electrolyte chemistry. To ensure long-term performance and material stability against NiO dissolution, polarization loss, and carbon capture efficiency, major considerations need to be taken into account in material selection, operating conditions, and electrode structure design.FCE has tested many single cells (250 cm2) and technology stacks (30 kW) under carbon capture operating conditions (4-5% CO2 in the cathode inlet as opposed to >15% in baseline MCFC systems) to understand parameters affecting performance, life, and to investigate design solutions for further enhancement. Figure 2 highlights the effect of CO2 concentration on the cathode lithiation. These measurements were conducted using an out-of-cell test (OCT) where cathode samples were exposed to different oxidizing environments. It appears that lean-CO2 gas atmospheres (<5%CO2) lead to increased lithium content in the NiO cathode. This may impact the electrolyte distribution and the cathode microstructure. Therefore, the electrolyte inventory (fill level), the lithium content and the basicity need to be considered to achieving optimal operating conditions.This paper will review the cathode material stability, microstructure, and durability under long-term carbon-capture operations. The effect of parameters such as electrolyte fill, gas composition, and electrolyte chemistry, as well as approaches to enhance the CO2 capture efficiency and life, will be discussed. Figure 1

Performance assessment of a hybrid solid oxide and molten carbonate fuel cell system with compressed air energy storage under different power demands

As electricity demand can vary considerably and unpredictably, it is necessary to integrate energy storage with power generation systems. This study investigates a solid oxide and molten carbonate fuel cell system integrated with a gas turbine (GT) for power generation. The advanced adiabatic compressed air energy storage (AA-CAES) system is designed to enhance the system flexibility. Simulations of the proposed power system are performed to demonstrate the amount of power that can supply to the loads during normal and peak modes of operation under steady-state conditions. The pressure ratios of the GT and AA-CAES and the additional air feed are used to design the system and analyze the system performance. The results show that a small additional air feed to the GT is certainly required for the hybrid system. The GT pressure ratio of 2 provides a maximum benefit. The AA-CAES pressure ratio of 5 is recommended to spare some air in the storage and minimize storage volume. Moreover, implementation of the GT and AA-CAES into the integrated fuel cell system allows the system to cope with the variations in power demand.

Energy, exergy, and environmental (3E) assessments of an integrated molten carbonate fuel cell (MCFC), Stirling engine and organic Rankine cycle (ORC) cogeneration system fed by a biomass-fueled gasifier

In this paper, a novel syngas-fed combined cogeneration plant, integrating a biomass gasifier, a molten carbonate fuel cell (MCFC), a heat recovery steam generator (HRSG) unit, a Stirling engine, and an organic Rankine cycle (ORC), is introduced and thermodynamically analyzed to recognize its potentials compared to the previous solo/combined systems. For the proposed system, energetic, exergetic as well as environmental evaluations are performed. Based on the results, the gasifier and the fuel cell have a significant contribution to the exergy destruction of the system. Through a parametric study, the current density and the stack temperature difference are known as the main effective factors on the plant performance. Meanwhile, dividing the whole system into three sub-models, i.e., model (1): power production plant including the gasifier and MCFC without including Stirling engine, HRSG, and ORC unit, model (2): the cogeneration system without ORC unit, and model (3): the whole cogeneration system, an environmental impact assessment is carried out regarding CO2 emission. Considering paper as biomass revealed that maximum value of exergy efficiency is 50.18% with CO2 emissions of 28.9 × 10−2 t.MWh−1 which compared to the solo MCFC system indicates 28.40% increase and 13.3 × 10−2 t.MWh−1 decrease in exergy efficiency and CO2 emission, respectively.

Analysis of Internal Gas Leaks in an MCFC System Package for an LNG-Fueled Ship

The airflow inside the housing of a 300-kW molten carbonate fuel cell (MCFC) system is designed to ensure safety in case of a gas leak by applying computational fluid dynamics (CFD) techniques. In particular, gas accumulating zones are identified to prevent damage to vulnerable components from high temperature and pressure. Furthermore, the location of the alarm unit with the gas-leak detector is recommended for construction of safe MCFC ships. In order to achieve this, a flow-tracking and contour field (for gas, temperature, and pressure) including a fuel-cell stack module, balance-of-plant, and various pipes is developed. With the simulated flow field, temperature flow is interpreted for the heating conditions of each component or pipe in order to find out where the temperature is concentrated inside the fuel cell system, as well as the increase in temperature at the exit. In addition, the gas leakage from the valves is investigated by using a flow simulation to analyze the gas and pressure distribution inside the fuel cell system.

Performance and Stability of Cathode Electrode Under Carbon Capture Operating Conditions

Introduction The high-temperature molten carbonate fuel cell (MCFC) is one of the most advanced clean power generating devices. To date >8 billion kWh of clean electricity has been produced commercially using this new technology. The high operating temperature of MCFC (550-650°C) dramatically improves the reaction kinetics and eliminates the need for a noble metal catalyst. The electrochemical reactions taking place during cell operation involve CO2 transfer from cathode to anode through electrolyte matrix in the form of carbonate ions (Figure 1). The transport of CO3 = is equivalent to that of O= and CO2 (CO3 = ⇔ O= + CO2). Therefore, MCFC stack technology can be utilized for efficient simultaneous power generation and CO2 separation/capture by integrating with conventional combustion-based coal and/or natural-gas power plants. The state of the art MCFC cathode is porous lithiated NiO. The cathode performance and stability are affected by several factors such as gas composition, temperature, electrode structure, and electrolyte chemistry. To ensure long-term performance and material stability (such as NiO cathode dissolution, polarization loss and CO2 capture efficiency), material selection, operating characteristics, and electrode design need to be carefully considered. FCE has operated numerous bench-scale single cells (100 W) and technology stacks (30 kW) under carbon capture operating conditions (4-5% CO2 in the cathode inlet as opposed to >15% in baseline MCFC systems) to understand parameters affecting performance, life, and to investigate design solutions for further enhancement. Figure 2 shows similar NiO cathode stability under standard as well as carbon capture conditions, projecting to useful life of >7-years under both operation conditions. More endurance carbon capture tests are being conducted for further verification. This paper will review the cathode material stability, microstructure, and durability under long-term carbon-capture operations. The effect of parameters such as electrolyte fill, gas composition and electrolyte chemistry, as well as approaches to enhance the CO2 capture efficiency and life, will be discussed. Figure 1

Methods of On-Site Electricity Generation with Landfill Gas

The US consumes large quantities of electricity. As a result, there is a growing concern that energy may not be readily available in the future. This worry is compounded by the depletion of traditional sources such as coal, petroleum, and natural gas. Municipal solid waste in landfills is a resource the country may utilize as a renewable source of energy, as the gas produced from landfills can be used to power generators for electricity production, rather than wasted and flared to comply with Resource Conservation and Recovery Act standards. Systems that utilize reciprocating internal combustion engines, microturbines, and molten carbonate fuel cells can feasibly and cleanly reduce landfill gas emissions while producing electricity. However, these methods require input work and initial investments. The main economic goal is to maximize energy production. After economic analysis, the molten carbonate fuel cell system was determined to be the most efficient due to its versatility and low emissions. The successful implementation of the system may result in the propagation of the system, the increase in value of landfill gas, and the waste that produces landfill gas. This may also lead to restructuring of municipal waste system to enhance the usage of landfill gas. Keywords: municipal solid waste, MSW, landfill gas, reciprocating internal combustion engines, microturbines, molten carbonate fuel cells, MCFCs, siloxanes, emissions, greenhouse gases.

Performance Enhancement of a Molten Carbonate Fuel Cell/Micro Gas Turbine Hybrid System With Carbon Capture by Off-Gas Recirculation

The demand for clean energy continues to increase as the human society becomes more aware of environmental challenges such as global warming. Various power systems based on high-temperature fuel cells have been proposed, especially hybrid systems combining a fuel cell with a gas turbine (GT), and research on carbon capture and storage (CCS) technology to prevent the emission of greenhouse gases is already underway. This study suggests a new method to innovatively enhance the efficiency of a molten carbonate fuel cell (MCFC)/micro GT hybrid system including carbon capture. The key technology adopted to improve the net cycle efficiency is off-gas recirculation. The hybrid system incorporating oxy-combustion capture was devised, and its performance was compared with that of a post-combustion system based on a hybrid system. A MCFC system based on a commercial unit was modeled. Externally supplied water for reforming was not needed as a result of the presence of the water vapor in the recirculated anode off-gas. The analyses confirmed that the thermal efficiencies of all the systems (MCFC stand-alone, hybrid, hybrid with oxy-combustion capture, hybrid with post-combustion capture) were significantly improved by introducing the off-gas recirculation. In particular, the largest efficiency improvement was observed for the oxy-combustion hybrid system. Its efficiency is over 57% and is even higher than that of the post-combustion hybrid system.

Crystal Morphology and Phase Transformation of LiAlO2: Combined Experimental and First-Principles Studies

Layered α-LiAlO2 matrix often suffers from detrimental structural and morphological changes during its lifetime, especially under H2-containing fuel inlet environments of molten carbonate fuel cell systems. However, the underlying mechanism of this phase and the morphological transformations has rarely been explored. In this study, transmission electron microscopy (TEM) techniques were used to determine the changes in structure and morphology of LiAlO2 samples lifted by a focused ion beam. In accordance with X-ray diffraction analysis, TEM images show that under H-rich conditions the rhombohedral α-LiAlO2 transforms to tetragonal γ-LiAlO2 phase with the appearance of the (101)-terminated octahedral-shaped γ-LiAlO2 crystallites. We further support, and plausibly rationalize, the observed transformations using density functional theory (DFT) calculation. The DFT computed surface energies of γ-LiAlO2 reveal that the {101} surface becomes the lowest energy surface upon H-adsorption, thus leading to formation of observed octahedral geometry. Contrary to stabilization of γ-LiAlO2 surfaces upon H passivation, DFT revealed H adsorption on α-LiAlO2 surfaces to be energetically unfavorable. This contrasting behavior of α-LiAlO2 and γ-LiAlO2 under H-rich environments could be a potential driving force for the observed α-LiAlO2 to γ-LiAlO2 phase transformation.