Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Optimal design of molten carbonate fuel cell combined cycle power plant and thermophotovoltaic system Mehdi Mehrpooya a, ⁎ , Roozbeh Khodayari b , S.M. Ali Moosavian b , Ali Dadak a a Renewable Energies and Environment Department, Faculty of New Science and Technologies, University of Tehran, Tehran, Iran b School of Chemical Engineering, University College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, Iran ARTICLE INFO Keywords: Molten carbonate fuel cell HRSG Gas turbine Combined cycle Thermophotovoltaic system Optimal design ABSTRACT 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 sub-system 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 in- creasing 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 perfor- mance of the TPV system was obtained at cell and emitter distance of 1 cm. Incorporating the GT to the MCFC enhanced the system’sefficiency to 54.83%. The efficiency of the proposed hybrid system was found to be 67.3%. 1. Introduction Energy plays a key role as a driving force in industry [1,2] and is one of the most important factors in the social, industrial and welfare development of society in the new century [3,4]. Improving living standards, global population growth, and industrialization have con- siderably enhanced global energy consumption, and this demand de- picts a proliferating trend [5,6]. Today, the political and economic backing of countries mainly depends on their productivity of fossil fuels, and the depletion of fossil fuels, or even desire to do so, poses a threat not only to their economics, but also to the economic system of other nations [7,8]. Moreover, the growing consumption of fossil fuels has led to rapid growth in various societies [9], but through the spread of combustion pollutants and the increment in carbon dioxide in the atmosphere and its aftermath, the world has undergone threating changes [10,11]. Creating any problems in the energy supply system will cause widespread disruption and damage in all economic and social sectors. Hence, countries have made diversification of energy resources one of their main strategies to prevent their dependence on a particular type of energy and to minimize their vulnerability to the upcoming energy crises [12,13]. To achieve that, a significant number of recent studies have been allocated to reduce dependence on previous common energies and the use of renewable energies [14,15]. Although gas-steam combined cycles have been developed at an increasing rate in recent years [16], many studies have been conducted to improve this condition due to the high rate of fuel consumption, greenhouse gas emissions [17], and increased production costs [18]. One of the solutions to overcome these problems is to hybridize high temperature fuel cells, such as MCFCs, with conventional gas-steam combined cycles with different arrangements [19]. High efficiency and low cost have made MCFCs one of the most popular high temperature fuel cells [20,21]. The high operating temperature of MCFCs has made https://doi.org/10.1016/j.enconman.2020.113177 Received 2 May 2020; Received in revised form 30 June 2020; Accepted 1 July 2020 ⁎ Corresponding author. E-mail address: mehrpoya@ut.ac.ir (M. Mehrpooya). Energy Conversion and Management 221 (2020) 113177 0196-8904/ © 2020 Elsevier Ltd. All rights reserved. T