Bi-objective optimization and environmental assessment of SOFC-based cogeneration system: performance evaluation with various organic fluids

Abstract

Heat recovery offers multiple advantages, such as reducing energy consumption, promoting environmental sustainability, and enhancing productivity. Consequently, in this study, a bi-evaporator organic flash cycle (BEOFC) is utilized to recover heat from a solid oxide fuel cell (SOFC) and serves as a heat recovery unit. The BEOFC is a groundbreaking system that generates cooling and electricity. It boasts a dual-evaporator design that cools air at two distinct temperatures. Examining various organic fluids for better BEOFC performance entails evaluating their thermodynamic, environmental, and economic aspects. Based on the results, R227ea is selected as the optimal working fluid for BEOFC due to its superior performance. Subsequently, a parametric study is conducted and a bi-objective optimization of the proposed system is performed, where the objective functions comprise minimizing the total unit cost of products (TUCP) and maximizing the exergy efficiency. Optimized performance can be achieved when TSS1= 364.5 K, Teva1= 273.1 K, TSOFC= 897.3 K, and JSOFC= 5004 A/m2. At this point, the exergy efficiency and TUCP surge by 2.63%-point and 27.1% compared to the initial state. However, there is a rise of 7.26% in CO2 emission rate, 13.15% in sustainability index, and 8.8% in the total exergoeconomic factor when compared to the base case.