Environmental assessment of a hybrid system composed of solid oxide fuel cell, gas turbine and multiple effect evaporation desalination system

Abstract

This study deals with a solid oxide fuel cell- gas turbine (SOFC-GT) hybrid system coupled with a multi-effect evaporation desalination plant with steam condensation. The environmental evaluation is also done due to the importance of waste energy recovery especially waste heat in power generation systems. The evaporation desalination plant is studied for using the excess heat to produce freshwater. The thermodynamic relationships governing different components of the system are first provided, including fuel cells, heat exchangers, gas turbine, and desalination plant. Next, given the absence of previous research on the environmental effects of cogeneration systems, despite its necessity, the study system is analyzed from an environmental point of view. Accordingly, the impacts of the system performance parameters, including the fuel consumption coefficients, compressor pressure ratio, fuel pre-reforming percentage, and the steam to carbon ratio are investigated on the CO2, CO, and NOx emission rates. Based on the findings, it is concluded that of different species, the impacts of CO, CO2, and NOx emission rates are significant on the environment. Thus, the impacts of pressure ratio and pre-reforming percentage on their emission rates have been studied. The results revealed with increasing the compressor pressure ratio, increasing the fuel consumption coefficients, and decreasing the fuel cell's exhaust temperature, the CO and NOx emission rates and corresponding social costs diminished. On the other hand, with elevation of the ratio of steam to carbon, the recovery rate, the fuel cell's exhaust temperature, the concerned gas emission rates, and corresponding social costs increased.