Harvesting waste heat from molten carbonate fuel cells for bifunction applications (original) (raw)
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Energies, 2019
By integrating an Absorption Refrigerator (AR), a new hybrid system model is established to reuse the waste heat from a Molten Carbonate Direct Carbon Fuel Cell (MCDCFC) for additional cooling production. Various irreversible losses in each element of the system are numerically described. The operating current density span of the MCDCFC that allows the AR to work is derived. Under different operating conditions, the mathematical expressions for equivalently evaluating the hybrid system performance are derived. In comparison with the stand-alone MCDCFC, the maximum attainable power density of the proposed system and its corresponding efficiency are increased by 5.8% and 6.8%, respectively. The generic performance features and optimum operating regions of the proposed system are demonstrated. A number of sensitivity analyses are performed to study the dependences of the proposed system performance on some physical parameters and operating conditions such as operating temperature, oper...
International Journal of Hydrogen Energy, 2017
In order to recover the waste heat produced in molten carbonate fuel cells (MCFCs), a new hybrid system mainly consisting of an MCFC, a thermoelectric generator, and a thermoelectric cooler is integrated for performance enhancement. The irreversible losses in each subsystem are fully considered. The relationship between the dimensionless electric current of the thermoelectric element and the electric current density of the MCFC is discussed in detail. Based on non-equilibrium thermodynamics, the analytical formulas for power density and efficiency of the hybrid system are specified under different operation conditions. The general performance characteristics of the hybrid system are revealed and the optimum regions for several parameters are given. Numerical calculations show that the power density and efficiency of the hybrid system are 3.4% and 4.0% larger than that of the stand-alone MCFC, respectively. The effects of some main operating and design parameters on the performance of the proposed system are discussed through parametric analyses. Abundant numerical calculation examples are provided to show how to improve the system performance. The results obtained may provide some theoretical bases for the MCFC performance improvement through heat management method.
Study of a molten carbonate fuel cell combined heat, hydrogen and power system: Energy analysis
Applied Thermal Engineering, 2013
To address the problem of fossil fuel usage and high greenhouse gas emissions at the Missouri University of Science and Technology campus, using of alternative fuels and renewable energy sources can lower energy consumption and greenhouse gas emissions. Biogas, produced by anaerobic digestion of wastewater, organic waste, agricultural waste, industrial waste, and animal by-products is a potential source of renewable energy. In this work, we have discussed the design of CHHP system for the campus using local resources. An energy flow and resource availability study is performed to identify the type and source of feedstock required to continuously run the fuel cell system at peak capacity. Following the resource assessment study, the team selects FuelCell Energy DFC1500™ unit as a molten carbonate fuel cell. The CHHP system provides electricity to power the university campus, thermal energy for heating the anaerobic digester, and hydrogen for transportation, back-up power and other needs. In conclusion, the CHHP system will be able to reduce fossil fuel usage, and greenhouse gas emissions at the university campus.
International Journal of Ambient Energy, 2020
Integrating a two-stage thermoelectric generator (TTEG) with a molten carbonate fuel cell (MCFC), a new hybrid system is put forward to harvest the waste heat from the MCFC for performance improvement. Both thermodynamic and electrochemical irreversible losses in each subsystem are fully taken into account. The thermoelectric element (TEM) number ratio between hot stage and cold stage is optimally designed using power output as objective function. The mathematical relationship between MCFC operating current density and the optimized TTEG dimensionless electric current is obtained, from which the MCFC operating current density interval that allows TTEG to function is determined. The analytical expressions for equivalent power output and efficiency to evaluate the hybrid system performance are obtained. The proposed hybrid system is demonstrated to be superior to either stand-alone MCFC or MCFC/single-stage TEG hybrid system. Effects of some crucial design and operation parameters on the system performance are revealed by parametric studies.
Energy Conversion and Management, 2015
A hybrid molten carbonate fuel cell power plant and carbon dioxide capturing process is investigated through the exergy and advanced exergy analysis. The results show that the greatest exergy destruction (181 MW) occurs in the combustion chamber. It is because of irreversibility of the chemical reactions in the combustion process. Also the lowest exergy efficiency is related to the fuel cell. Advanced exergy analysis shows that the most portion of the exergy destruction is avoidable (more than 65%). Optimal design of the process is done by adjusting the effective operating conditions for reducing the power consumption and carbon dioxide emission of the process. Results of the optimization shows that the power consumption in the compressors can be reduced up to 33%.
Energy Conversion and Management, 2020
A novel hybrid system consisting of a molten carbonate fuel cell (MCFC), a gas turbine (GT), a steam cycle and a thermophotovoltaic (TPV) system to generate power is introduced and investigated. For this purpose, a GT is coupled to a MCFC in order to utilize unused fuel, raise the gas components temperature, supply the required carbon dioxide, and further power generation. Moreover, in order to boost the power generation and ameliorate the overall efficiency, a TPV system together with a steam cycle has been added to the system for heat recovery from the combustion chamber radiation and cathode output stream, respectively. The simulation of the hybrid system was accomplished through ASPEN HYSYS and MATLAB software. The effect of different influential parameters on each subsystem as well as the proposed hybrid system was examined comprehensively through sensitivity analysis. The results obtained revealed that increasing MCFC temperature decreased the anode, cathode, and ohmic overpotentials, while augmented the output voltage of the MCFC led to enhanced MCFC performance. Furthermore, the output voltage, power density, and efficiency of the MCFC enhanced with increasing the operating pressure for both of the fuel consumption rates. The output voltage and power density of the MCFC decreased as the fuel consumption rate incremented due to increased polarization losses, while the electrical efficiency of the MCFC enhanced. Optimizing the output temperature of the first and second heat exchangers increased the power of the steam turbine by about 16 kW. The highest power density and performance of the TPV system was obtained at cell and emitter distance of 1 cm. Incorporating the GT to the MCFC enhanced the system's efficiency to 54.83%. The efficiency of the proposed hybrid system was found to be 67.3%.
Thermodynamic Study of a Molten Carbonate Fuel Cell (MCFC) System
Journal of emerging technologies and innovative research, 2018
In the present work, thermodynamic analysis of a molten carbonate fuel cell (MCFC) is considered. Accordingly, a thermodynamic model is developed to understand performance of the cell at different operating conditions. The effect of operating parameters like working temperature, fuel utilization, current density, gas constituents etc. on the performance of the basic MCFC are studied to understand the behaviour of the cell. It is noticed that the cell voltage shows a strong dependence on the operating temperature. The actual cell voltage is less than the reversible cell voltage because of the losses occurs in a cell which is taken constant in the present analysis. Result shows that an operating temperature of 650 0 C offers an optimization for better performance and cell life.
Energy and exergy analyses of a combined molten carbonate fuel cell – Gas turbine system
Fuel and Energy Abstracts, 2011
Exergy Efficiency a b s t r a c t This study deals with the thermodynamic analysis of molten carbonate fuel cell combined with a gas turbine, based on the first-and second-law of thermodynamics. The mass, energy, entropy and exergy balance equations are written and applied to the system and its components. Some parametric studies are performed to investigate the change of system performance through energy and exergy efficiencies with the change of operating conditions. The irreversibilities occuring in different devices of the integrated system are also investigated through the exergy destruction analysis in these devices. The maximum output work of the MCFC is estimated to be 314.3 kW for an operating temperature of 650 C. The overall energy and exergy efficiencies achieved for this system are 42.89% and 37.75%, respectively. address: Ibrahim.Dincer@uoit.ca (I. Dincer).
Energy Conversion and Management, 2014
To address the problem of fossil fuel usage and high greenhouse gas emissions at the Missouri University of Science and Technology campus, using of alternative fuels and renewable energy sources can lower energy consumption and greenhouse gas emissions. Biogas, produced by anaerobic digestion of wastewater, organic waste, agricultural waste, industrial waste, and animal by-products is a potential source of renewable energy. In this work, we have discussed the design of CHHP system for the campus using local resources. An energy flow and resource availability study is performed to identify the type and source of feedstock required to continuously run the fuel cell system at peak capacity. Following the resource assessment study, the team selects FuelCell Energy DFC1500TM unit as a MCFC. The CHHP system provides electricity to power the university campus, thermal energy for heating the anaerobic digester, and hydrogen for transportation, back-up power and other needs. In conclusion, the CHHP system will be able to reduce fossil fuel usage, and greenhouse gas emissions at the university campus.
Economic analysis of a combined heat and power molten carbonate fuel cell system
Journal of Power Sources, 2007
Fuel cells can be attractive for use as stationary combined heat and power (CHP) systems. Molten carbonate fuel cell (MCFC) power plants are prime candidates for the utilization of fossil based fuels to generate high efficiency ultra clean power. However, fuel cells are considerably more expensive than comparable conventional technologies and therefore a careful analysis of the economics must be taken. This work presents analysis on the feasibility of installing both a FuelCell Energy DFC ® 1500MA and 300MA system for use at Adams Thermal Systems, a manufacturing facility in the U.S. Midwest. The paper examined thoroughly the economics driving the appropriateness of this measure. In addition, a parametric study was conducted to determine scenarios including variation in electric and natural gas rates along with reduced installation costs.