Development and tri-objective exergoeconomic-environmental optimization of a novel molten carbonate fuel cell-based system for power, hydrogen and freshwater tri-generation.

The world power sector is going to change over from its conventional large scale power systems to novel small scale efficient ones, where the fuel cell technology is a promising option. In this paper, a novel tri-generation system based on MCFC is presented for power, hydrogen and freshwater production. The Solid Oxide Electrolyzer Cell (SOEC) is employed for hydrogen production and Multiple Effect Distillation (MED) system is used for freshwater generation to recover the MCFC waste heat. Comprehensive exergoeconomic evaluation and tri-objective optimization is conducted considering exergy efficiency, product cost and CO 2 emission as the objectives. Besides the operating conditions and optimal design variables are determined for single-objective optimizations. The results show that, tri-generation system yields at least 4.5 % gain in exergetic efficiency compared to the standalone MCFC. From the parametric study it is revealed that, higher values of hydrogen production is reached for lower fuel utilization factor and stack temperature and higher current densities. Meanwhile, higher values of freshwater is attained with higher steam to carbon ratio, fuel utilization factor, stack temperature, and lower current density values. The tri-objective optimization results demonstrated that the minimum cost and emissions can be reached to 9.37 $/GJ, and 1.425 ton/MWh, respectively while the maximum efficiency is 46.54% at the best point. [Display omitted] • A novel MCFC-based tri-generation system for power, hydrogen and freshwater is proposed. • Exergy, exergoeconomic and environmental analyses are performed on the proposed system. • Tri-objective optimization is conducted to determine the best operating conditions. • Unit product cost of 9.37 $/GJ is obtained under tri-objective optimal operating conditions. • Higher stack temperature brings about higher hydrogen and freshwater production. [ABSTRACT FROM AUTHOR]