High-efficiency utilization of biomass and seawater resources based on a distributed system with SOFC-assisted CO2 capture: Feasibility analysis and optimization

Abstract

This paper develops a distributed system with SOFC-assisted carbon capture (SACC) by integrating the Rankine cycle, double-effect absorption chiller and multi-effect distillation unit to produce electricity, cooling and freshwater. To study the feasibility of the developed system, thermodynamic, economic and carbon footprint analyses and optimization are conducted on six different cases for the system. The results reveal that regardless of the biomass sources used as fuel, the developed SACC system requires 5%-9% less power consumption for CO2 capture compared to traditional methods. Moreover, the system fueled by switch grass exhibits superior efficiencies, and the system thermal efficiency (ηth) with SACC achieves 56.35% with corresponding levelized cost of products (cp) and total global warming potential (GWPt) of 54.94 $/GJ and −0.129 kg/kWh. Exergy analysis demonstrates that the prime mover unit (PMU) deserves the greatest irreversibility for all cases with a relative exergy destruction rate (y*k) of over 65% of the whole system. Within the PMU, the gasifier and SOFC are responsible for the highest irreversibility, and the y*k of the gasifier is over 50% and the SOFC’s is close to 9%. The parameter study indicates that an increase in the gasification temperature is unfavorable to ηth, however, it is conducive to the improvement of net power output (Wnet) when the temperature exceeds a certain value (e.g., 914.3℃ and 885.7℃ for Case-5 and Case-6). An appropriate increase in current density improves ηth and Wnet, and reduces cp, albeit slightly detrimental to environment. The optimization results demonstrate that Case-2 and Case-6 have superior thermodynamics and economics but are detrimental to the environment. In contrast, Case-1 and Case-5 are the most environmentally friendly, but their economics and thermodynamics are degraded to some extent.