Energy and exergy analyses of solid oxide fuel cell-gas turbine hybrid systems fed by different renewable biofuels: A comparative study

Abstract

In recent years, many studies have been conducted on hybrid solid oxide fuel cell and gas turbine which fed by renewable fuels to reach the high-efficiency power and the low pollution. In this paper, a thermodynamic study based on energy and exergy analyses of a hybrid solid oxide fuel cell and gas turbine hybrid system has been conducted in the presence of reforming with steam, in which the effects of using natural gas and other biofuels including Sewage biogas, Agricultural and Industrial waste biogas, Syngas, Biofuel and Gasified biomass, have been compared to this system. The purpose of this paper is to investigate the effect of each of the mentioned fuels on the performance of individual equipment and the entire system from the thermodynamic perspective. Initially, the modeling and energy balance of all components in the system were carried out in detail. Further, calculating the exergy destruction of all components of the system and the effects of applying different biofuels on the key parameters of the system, including total production power, operating pressure and temperature, compression ratio, the water-to-fuel ratio in the reforming, energy and exergy efficiency, and the amount of irreversibility of each component in the system have been analyzed. To compare more accurately between different fuels, an equal amount of each fuel is considered, and the effect of each fuel system on the hybrid system is analyzed by calculating the operating parameters of the system. By studying the results of modeling, it was determined that natural gas with 879.03 kW produced the highest production capacity and Gasified biomass with 45.44 kW has the least amount of power generation. By studying the thermodynamics of the system, if it is fed with Natural gas, the highest exergy destruction (687.45 kW) occurs and the lowest total exergy destruction rate is related to the system fed by gasified biomass (101.12 kW). Comparing the fuels, it was concluded that the electrical efficiency of the system fed with natural gas has the highest efficiency (72.71%) and Biofuel has the lowest total electrical efficiency (56.6%). Furthermore, by examining the exergy efficiency of the whole system, it was found that Natural gas with the highest efficiency of 61.29% and Gasified biomass with 46.06% the lowest exergy efficiency can be detected. Finally, the effect of the percentage combination of each fuel on the performance of all equipment from the perspective of energy and exergy has been studied.