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Energy and exergy analyses of a hybrid system containing solid oxide and molten carbonate fuel cells, a gas turbine, and a compressed air energy storage unit
(2021-10-11)
Jienkulsawad, Prathak
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Patcharavorachot, Yaneeporn
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Chen, Yong Song
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Arpornwichanop, Amornchai
Design of a hybrid system composed of a solid oxide fuel cell (SOFC), molten carbonate fuel cell (MCFC), gas turbine (GT), and an advanced adiabatic compressed air energy storage (AA-CAES) based on only energy analysis could not completely identify optimal operating conditions. In this study, the energy and exergy analyses of the hybrid fuel cell system are performed to determine suitable working conditions for stable system operation with load flexibility. Pressure ratios of the compressors and energy charging ratios are varied to investigate their effects on the performance of the hybrid system. The hybrid fuel cell system is found to produce electricity up to 60% of the variation in demand. A GT pressure ratio of 2 provides agreeable conditions for efficient operation of the hybrid system. An AA-CAES pressure ratio of 15 and charging ratio of 0.9 assist in lengthening the discharging time during a high load demand based on an electricity variation of 50%.
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Thermodynamic analysis of a proton conducting SOFC integrated system fuelled by different renewable fuels
(2021-03-19)
Saebea, Dang
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Arpornwichanop, Amornchai
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Patcharavorachot, Yaneeporn
This work proposes a power generation system consisting of steam reformer and SOFC–H+ fuelled by different types of fuel, i.e., ethanol, glycerol and biogas. The performance analysis of integrated system is performed based on thermodynamic calculation through Aspen Plus simulator. The total of the Gibbs free energy minimization is used to determine product composition at equilibrium. The electrochemical model not only considers all voltage losses but also includes the effect of current leakage as a result from the electrolyte used. Considering the operating condition of steam reformer, it is found that the gas product contains the highest amount of hydrogen without the carbon formation when reformer is operated at 973 K with steam to carbon ratio of 1. In addition, the simulation results show that the SOFC–H+ operated at 973 K and 1 A/cm2 can provide a suitable compromise between system performances and exhaust gas composition. The use of glycerol reformate has the highest cell and system efficiencies and fuel utilization compared to the others. In addition, the integrated system fuelled by glycerol can release low CO amount whereas there is more heat provided to the surrounding. Therefore, it can be concluded that glycerol is suitable renewable fuel for SOFC–H+ integrated system.
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Performance assessment of a hybrid solid oxide and molten carbonate fuel cell system with compressed air energy storage under different power demands
(2020-01-01)
Jienkulsawad, Prathak
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Saebea, Dang
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Patcharavorachot, Yaneeporn
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Arpornwichanop, Amornchai
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.
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Hydrogen and power generation from supercritical water reforming of glycerol and pressurized SOFC integrated system: Use of different CO2 adsorption process
(2018-09-13)
Patcharavorachot, Yaneeporn
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Saebea, Dang
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Authayanun, Suthida
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Arpornwichanop, Amornchai
The performance analysis of an integrated system of glycerol supercritical water reforming and pressurized SOFC was presented. The use of different CO<inf>2</inf> adsorption processes that include in situ and ex situ processes was compared to determine the suitable process for hydrogen and power generations. The influence of operating condition, e.g., temperature and pressure of reformer, supercritical water to glycerol (S/G) molar ratio, and calcium oxide to glycerol (CaO/G) molar ratio was examined. Then, the electrical performance of each integrated process was considered with respect to the SOFC conditions comprising temperature, pressure, and current density. The simulation results revealed that both processes have same favourable conditions for temperature and pressure operated at 800 °C and 240 atm, respectively. The suitable S/G and CaO/G molar ratios for in situ process are 10 and 2 whereas those for ex situ process are 20 and 1. Under these conditions, maximum hydrogen can be achieved as 87% and 75% for in situ and ex situ processes, respectively. When both integrated processes are operated at the optimal SOFC conditions as 900 °C, 4 atm, and current density of 10,000 A/m2, the SOFC efficiency of 71.56% and 62.12% can provide for in situ and ex situ processes, respectively.
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Analysis of a solid oxide fuel cell and a molten carbonate fuel cell integrated system with different configurations
(2018-01-01)
Jienkulsawad, Prathak
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Saebea, Dang
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Patcharavorachot, Yaneeporn
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Kheawhom, Soorathep
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Arpornwichanop, Amornchai
A solid oxide fuel cell with internal reforming operation is run at partial fuel utilization; thus, the remaining fuel can be further used for producing additional power. In addition, the exhaust gas of a solid oxide fuel cell still contains carbon dioxide, which is the primary greenhouse gas, and identifying a way to utilize this carbon dioxide is important. Integrating the solid oxide fuel cell with the molten carbonate fuel cell is a potential solution for carbon dioxide utilization. In this study, the performance of the integrated fuel cell system is analyzed. The solid oxide fuel cell is the main power generator, and the molten carbonate fuel cell is regarded as a carbon dioxide concentrator that produces electricity as a by-product. Modeling of the solid oxide fuel cell and the molten carbonate fuel cell is based on one-dimensional mass balance, considering all cell voltage losses. Primary operating conditions of the integrated fuel cell system that affect the system efficiencies in terms of power generation and carbon dioxide utilization are studied, and the optimal operating parameters are identified based on these criteria. Various configurations of the integrated fuel cell system are proposed and compared to determine the suitable design of the integrated fuel cell system.
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Effect of anode-cathode exhaust gas recirculation on energy recuperation in a solid oxide fuel cell-gas turbine hybrid power system
(2016-01-01)
Saebea, Dang
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Authayanun, Suthida
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Patcharavorachot, Yaneeporn
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Arpornwichanop, Amornchai
A solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system supplying liquid fuel as ethanol exhibits promise as an auxiliary power unit. In this study, the recirculation of anode and cathode exhaust gas in the SOFC-GT system is proposed to improve the efficiency of heat management in the SOFC-GT hybrid system. The key operating parameters, such as fuel utilization factor and the cell and GT temperatures, are analyzed in terms of the performance of the SOFC-GT hybrid systems. The simulation results show that the recirculation of anode and cathode exhaust gas has a direct impact on the turbine performance. To maintain the inlet temperature of the small turbine in the range of 873-1223 K, the amount of fuel and air added to the combustor to control the turbine inlet temperature on the system performance is also investigated. A SOFC-GT hybrid system with both anode and cathode exhaust gas recirculation achieves the highest system and thermal efficiency.
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Analysis of a pressurized solid oxide fuel cell-gas turbine hybrid power system with cathode gas recirculation
(2013-04-15)
Saebea, Dang
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Patcharavorachot, Yaneeporn
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Assabumrungrat, Suttichai
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Arpornwichanop, Amornchai
A pressurized solid oxide fuel cell-gas turbine hybrid system (SOFC-GT system) has been received much attention for a distributed power generation due to its high efficiency. When considering an energy management of the system, it is found that a heat input is highly required to preheat air before being fed to the SOFC stack. The recirculation of a high-temperature cathode exhaust gas is probably an interesting option to reduce the requirement of an external heat for the SOFC-GT system. This study aims to analyze the pressurized SOFC-GT hybrid system fed by ethanol with the recycle of a cathode exhaust gas via a simulation study. Effect of important operating parameters on the electrical efficiency and heat management of the system is investigated. The results indicate that an increase in the operating pressure dramatically improves the system electrical efficiency. The suitable pressure is in a range of 4-6 bar, achieving the highest system electrical efficiency and the lowest recuperation energy from the waste heat of the GT exhaust gas. In addition, it is found that the waste heat obtained from the GT is higher than the heat required for the system, leading to a possibility of the SOFC-GT system to be operated at a self-sustainable condition. Under a high pressure operation, the SOFC-GT system requires a high recirculation of the cathode exhaust gas to maintain the system without supplying the external heat; however, the increased recirculation ratio of the cathode exhaust gas reduces the system electrical efficiency. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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Use of different renewable fuels in a steam reformer integrated into a solid oxide fuel cell: Theoretical analysis and performance comparison
(2013-01-01)
Saebea, Dang
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Authayanun, Suthida
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Patcharavorachot, Yaneeporn
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Paengjuntuek, Woranee
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Arpornwichanop, Amornchai
Hydrogen production from renewable energy resources has received significant attention with advances in fuel cell technology. The fuel type and operational reforming conditions directly affect fuel cell electricity generation. This study analyzes the theoretical performance of a solid oxide fuel cell (SOFC) integrated with a steam reforming process using three different renewable fuels: ethanol, glycerol and biogas. The effects of key steam reformer operating parameters on the hydrogen production for SOFCs are investigated. The performances of SOFC systems run on different fuels are compared in terms of electrical and thermal efficiencies. It is found that the biogas-fueled SOFC system requires the most energy, whereas the ethanol-fueled SOFC system achieves the highest electrical and thermal efficiencies. © 2012 Elsevier Ltd.
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Neural network hybrid model of a direct internal reforming solid oxide fuel cell
(2012-02-01)
Chaichana, Kattiyapon
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Patcharavorachot, Yaneeporn
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Chutichai, Bhawasut
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Saebea, Dang
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Assabumrungrat, Suttichai
A mathematical model is an important tool for analysis and design of fuel cell stacks and systems. In general, the complete description of fuel cells requires an electrochemical model to predict their electrical characteristics, i.e., cell voltage and current density. However, obtaining the electrochemical model is quite a difficult and complicated task as it involves various operational, structural and electrochemical reaction parameters. In this study, a neural network model was first proposed to predict the electrochemical characteristics of solid oxide fuel cell (SOFC). Various NN structures were trained based on the back-propagation feed-forward approach. The results showed that the NN with optimal structure reliably provides a good estimation of fuel cell electrical characteristics. Then, a neural network hybrid model of a direct internal reforming SOFC, combining mass conservation equations with the NN model, was developed to determine the distributions of gaseous components in fuel and air channels of SOFC as well as the performance of the SOFC in terms of power density and fuel cell efficiency. The effects of various key parameters, e.g., temperature, pressure, steam to carbon ratio, degree of pre-reforming, and inlet fuel flow rate on the SOFC performance under steady-state and isothermal conditions were also investigated. A combination of the first principle model and NN presents a significant advantage of predicting the SOFC performance with accuracy and less computational time. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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Design and Thermal Analysis of a Solid Oxide Fuel Cell System Integrated with Ethanol Steam Reforming
(2012-01-01)
Thanomjit, Chollaphan
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Patcharavorachot, Yaneeporn
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Arpornwichanop, Amornchai
In this study, a thermal management of the solid oxide fuel cell (SOFC) system integrated with a steam reformer was investigated. Due to its renewable and green energy sources, ethanol was chosen as a fuel for the SOFC system in which it was converted into a hydrogen rich gas via a steam reforming. Modeling of the SOFC system was performed using a process simulator. The SOFC system performance was evaluated with respect to key operating parameters such as reforming temperature, SOFC temperature and steam to ethanol ratio. It was found that the ethanol reformer and pre-heaters require high energy consumption. To improve its thermal efficiency, the SOFC system with heat integration was analyzed and the exhaust gas from an SOFC stack was considered a useful heat source. Pinch analysis was applied to design the SOFC system with the aim to minimize the requirement of external energy sources. © 2012 Elsevier B.V.

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