Performance Analysis of a Hybrid System Consisting of a Molten Carbonate Direct Carbon Fuel Cell and an Absorption Refrigerator (original) (raw)
Related papers
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.
Harvesting waste heat from molten carbonate fuel cells for bifunction applications
Journal of Renewable and Sustainable Energy, 2019
A generic combined system composed primarily of a molten carbonate fuel cell (MCFC) and an absorption cycle is proposed, in which the absorption cycle can operate as either an absorption heat pump (AHP) for heat amplification or an absorption refrigerator (APR) for cooling applications. The equivalent power output and efficiency expressions for the combined system are formulated by considering various electrochemical-thermodynamic irreversible losses within and between each subsystem. As a result, the generic performance characteristics are revealed, and the optimum criteria are determined. When the absorption cycle operates as an AHP or an APR, the maximum achievable power densities of the combined system are 21.23% and 10.2% higher than those of a single MCFC, respectively. Furthermore, comprehensive parametric studies are performed to show the dependency of the combined system performance on some of the important operating conditions and composite parameters.
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%.
Energies
The study presents a concept and calculations concerning the operation of the direct carbon fuel cell (DCFC) with molten hydroxide electrolyte (MH-DCFC) as the basic source of electricity integrated with heat and cool air generation systems. The technology of direct carbon fuel cells assumes the direct use of a carbon fuel (such as fossil coal, carbonized biomass, graphite, coke etc.) to generate electricity with high efficiency and low impact on the environment. These cells operate by utilizing carbon fuel in the range of temperatures of 673–973 K and allow for generation of electricity with an efficiency of about 56%. In order to improve the fuel conversion efficiency, the heat generated in the process of cell cooling can be used to prepare hot water, for heating during the heating season, while during the summer period, heat from cooling of the direct carbon fuel cells can be utilized in the process of cool air production (chilled air) using absorption chillers for e.g. air condi...
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%.
International Journal of Low-Carbon Technologies
The production of liquefied natural gas (LNG) is a high energy-consuming process. The study of ways to reduce energy consumption and consequently to reduce operational costs is imperative. Toward this purpose, this study proposes a hybrid system adopting a mixed refrigerant for the liquefaction of natural gas that is precooled with an ammonia/water absorption refrigeration (AR) cycle utilizing the exhaust heat of a molten carbonate fuel cell, 700°C and 2.74 bar, coupled with a gas turbine and a bottoming Brayton super-critical carbon dioxide cycle. The inauguration of the ammonia/water AR cycle to the LNG process increases the cooling load of the cycle by 10%, providing a 28.3-MW cooling load duty while having a 0.45 coefficient of performance. Employing the hybrid system reduces energy consumption, attaining 85% overall thermal efficiency, 53% electrical efficiency and 35% fuel cell efficiency. The hybrid system produces 6300 kg.mol.h−1 of LNG and 146.55 MW of electrical power. The...
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.
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.
2015
In general, a solid oxide fuel cell (SOFC) based on an internal reforming operation cannot be run with complete fuel utilization; therefore, the remaining fuel needs to be effectively handled. Furthermore, the SOFC exhaust gas still contains carbon dioxide, which is the primary greenhouse gas, and searching for the way to utilize this carbon dioxide is important. A molten carbonate fuel cell (MCFC) appears to be a potential technology to mitigate the emissions of carbon dioxide. In this study, the performance of the integrated SOFC and MCFC system is analyzed. The SOFC is considered a main power generation and the MCFC is regarded as a carbon dioxide concentrator along with producing electricity as a by-product. Mathematical models of the SOFC and MCFC are based on one-dimensional mass balances taking into all various cell voltage losses under steady-state and isothermal conditions. Primary operating conditions of the integrated fuel cell system that affects the system efficiencies ...