---

This paper presents a transient model for planar solid oxide fuel cells anode, which allows the simulation of steady-state performance characteristics, transient operation behavior, as well as electrochemical impedance spectra. The developed model couples the mass transport with electrochemical kinetics. The 1D Navier-Stokes conservation equations and species conservation equations are used for gas transport in the anode channel, and the linear kinetic is used for the anode electrochemistry. In order to model the electrochemical impedance, a sinusoidal excitation is imposed to system of transient equations and the obtained harmonic response is used as a base for electrochemical impedance spectra simulation. In order to solve the system of the nonlinear equations, a numerical code based on finite volume method is developed and utilized. Results show that the mass transfer in channel leads to a low frequency capacitive semicircle in the Nyquist plot. Moreover, the influence of parameters such as overvoltage, temperature, velocity and hydrogen inlet concentration on the electrochemical impedance has also been studied and the results are discussed. The simulation results are in good agreement with published data.

---

The purpose of this study is thermo-economic analysis of a combined fuel cell and micro gas turbine power plant cycle for using in small scale CHP systems. Since the fuel cell is the main source of power generation in hybrid systems, in this study, complete electrochemical, thermal and thermodynamic calculations are performed to obtain more accurate results; and unlike most studies, the cell temperature is not assumed constant. The performance analysis of the hybrid system shows that increasing the pressure and air to fuel ratio, causes to loss of electrical efficiency and increase in the electricity price because of reduction in cell and turbine inlet gas temperatures. The other results of this study show that considering the economic life of the system, making use of this type of hybrid systems is economical and generates less electricity price in comparison with micro gas turbine.

---

Solid oxide fuel cells competence in combination with gas turbine cycle has caused the obtained synthetic system to become as a new power production system in consideration of different researchers. One of the important applications of this type of hybrid systems is to use them in UAV propulsion systems and in airliners as an APU. The main purpose of this research is design of a hybrid APU equipped to solid oxide fuel cell that would be one of the basic requirements for electric power generation in larger aircrafts in the future. Design parameters and decision-making variables in analysis of this system are the compressor pressure ratio, gas temperatures entrance to turbine and the number of selected cells. The results show that the system’s increasing pressure causes decrease in the temperature of outlet gases from the turbine and the cell’s operating temperature; and this problem severely affects the productivity and efficiency of the electrical system. At 1000 ° C for entrance gases to the turbine, electrical efficiency of system is about 49 percent. Also, the maximum electrical efficiency of the system in fuel cell is estimated to be about 55 percent. The obtained result shows that in case of controlling the generated heat in the cell and effective usage of it, the overall system efficiency will be augmentable about 84 percent. On the other hand, increasing the number of cells will cause increasing electrical efficiency and reducing the overall efficiency of the fuel cell hybrid system.

---

The present study was undertaken to design and analyze three different configurations of SOFC (solid oxide fuel cell) and MGT (micro-gas turbine) hybrid system. The first presented configuration is a hybrid system with one fuel cell which considered as a basic mode. Two other configurations are considered with two fuel cells that mounted upstream of the turbine in series and parallel forms. The aim of the current study was thermodynamic analyze of designed hybrid systems and achieving the optimum fuel consumption factor for fuel cells that used in hybrid systems. Therefore, other performance parameters such as turbine inlet temperature, compressor pressure ratio and the number of cells, which play an important role in implementation of SOFC and gas-turbine, were parametrically analyzed and the obtained optimum values were used in analyzes. In this regard, the parameters associated with electrochemical processes within cells considered as a function of their chemical and thermodynamic conditions, and their modeling code combined with the modeling code of micro gas turbine cycle. The results of this study revealed that fuel utilization factor has direct impact on the SOFC/MGT hybrid system performance. Also we demonstrate that the optimal fuel utilization factor for basic mode hybrid system was 0.85, hybrid system with 2 series fuel cells were obtained 0.7 and 0.8 respectively and hybrid system with two parallel fuel cells were calculated to be 0.85. Moreover, the SOFC/MGT hybrid system with two series fuel cells account for the highest electrical efficiency and was selected as the most efficient configuration.

---

In this study, performance of a coplanar single chamber solid oxide fuel cell with oxygen-methane-nitrogen under steady state conditions is investigated. The cell geometry is considered two dimensional and the computational domain is consists of gas chamber, anode electrode, cathode electrode and electrolyte. Oxygen-methane-nitrogen mixture is fed to the cell with initial mass fraction of 0.07, 0.14 and 0.77 respectively. All physical properties are considered as temperature dependent. The fully coupled nonlinear governing equations including mass, momentum, species and charge conservation equations are formulated in commercial software and solved using finite elements method. To show the model accuracy, the current model results are compared with a similar numerical model. Finally, the cell performance analysis including velocity, temperature and concentration of all species is discussed. The results show that the maximum temperature is occurred at anode side. This is due to methane oxidation reaction which is extremely exothermic. This temperature growth is an advantage for the cell to be able to reduce its working temperature. Furthermore, it is shown that a large amount of hydrogen leaves the chamber without any use. This is the main reason of low performance occurred in this type of cell.

---

In today’s world, using of biogas is increasing due to its methane content, renewability, and low price. Solid oxide fuel cell is one of the best energy conversion technologies, in order to use biogas and it has a high potential to integrate with the gas turbine. In this paper, solid oxide fuel cell-gas turbine hybrid system, which is fed by biogas is modeled with respect to energy and economic aspects. Maximization of electrical energy efficiency and minimization of total investment cost are objective functions, which are considered to find the optimal design variables of the hybrid system. First, each component of the hybrid system is modeled and validated individually. Then, in order to optimize the hybrid system, multi objective optimization via NSGAII is implemented and optimal values of design parameters of the hybrid system were calculated. Optimal point is obtained using Euclidian non-dimensionalization and LINMAP decision making method in Pareto front. So, optimal design values are 66 percent and 175227.4 $, which are electrical energy efficiency and total investment cost, respectively. In optimal point Levelized unit cost is 6.3 cent per kWh. Finally, in order to determine the effect of design parameters on the objective functions, sensitivity of each design parameters were analyzed using Sobol's sensitivity analysis method. Results show that compressor pressure ratio has the maximum effect on electrical energy efficiency. Furthermore, turbine isentropic efficiency and fuel cell current have the maximum effect on the total investment cost.

---

In recent years, the importance and requirements for high-quality energy and water has been increased significantly, and this trend will strongly continue. One of the promising solution for the water scarcity's problem is desalination of the oceans salt water by thermal methods, and if the required thermal energy is provided by wastes of a thermal power plant it will be competitive with other methods. In this paper, a combined cycle including solid oxide fuel cell (SOFC) and gas turbine is used as thermal resource. Here, combination of these two systems beside of multi effect desalination (MED) system leads to reduce in energy consumption, pollutant emissions, investment and operation and maintenance cost, as well as increase of efficiency in comparison with the conventional individual systems. Exergetic and economic analysis using a computer program in EES software was performed. The results proposed a system with thermal and exergy efficiency of 60 % and 57%, respectively. The system expenditures and revenues were estimated, and the effect of two important design parameters, i.e. operational temperature and current density of fuel cell, on exergy efficiency and levelized cost of electricity were investigated. Consequently, the reliability and availability of the proposed system are calculated as 0.842, using the Markov method. It is seen after reliability analysis and availability calculation the exergy and energy efficiency is reduced and LCOE increased by 8.8%.

---

In the present study, a novel integrated system containing biomass gasifier, sodium high-temperature heat pipes, and solid oxide fuel cells is introduced. The integrated system is taken into consideration due to its high efficiency and power in order to simultaneous producing electrical power and heat. The modeling of system is performed using equilibrium constants, mass and energy conservation law and the analysis of codes is done in EES software. The effect of gasifier STBR, current density, fuel utilization factor, and outlet fuel cell’s temperature as variable parameters is investigated on the power and total energy efficiency of integrated system using response surface method; after validation of modeling in comparison to the experimental results. The analysis of variance results indicate that fuel utilization factor (with 53% contribution) and current density (with 33% contribution) are the most effective parameter on the power and total efficiency, respectively. The power of integrated system is increased by increasing of temperature while power has an increasing behavior follows by decreasing behavior by increasing fuel utilization factor. The total efficiency is increased by increasing temperature and STBR while it is decreased by increasing current density and fuel utilization factor. The results revealed that the power and total efficiency is obtained at optimum states as high as 300 kW and 90%, respectively.

---

In this article, a new power, cooling and heating cogeneration system consisting of a solid oxide fuel cell (SOFC) - gas turbine (GT), a heat recovery steam generator (HRSG), Generator-Absorber-heat eXchange (GAX) absorption refrigeration cycle and a heat exchanger for heat recovery (HR) has been studied from a thermodynamic and economic perspective. The modeling of this cycle was done by solving the electrochemical, thermodynamic and exergoeconomic equations for fuel cell and system components, simultaneously. The results showed that the exergy of our proposed combined cycle is 14.9% more and the irreversibility rate of this cycle is 10.6% less than that of the combined SOFC-GT-GAX systems in the same conditions. Also, the fuel cell and the afterburner have the highest rate of exergy destruction among other components due to irreversibility. Exergoeconomic analysis showed that the sum of uint cost of products (SUCP), the exergoeconomic factor, the capital cost rate and the exergy destruction cost rate for the overall system is equal to 331.1 $/GJ, 29.3%, 10.47 $/h and 25.32 $/h, respectively. Parametric studies showed that increasing the current density will increase the net electrical power, heating capacity of HRSG and HR heat exchanger, cooling capacity and total irreversibility. Also, with increasing of the current density, both the exergy efficiency and SUCP decrease.

---