Optimal Heat-Up Planning of a Solid Oxide Fuel Cell with and without Hot Air Recycling by Considering Energy, Time, and Temperature Gradient

A solid oxide fuel cell (SOFC) needs to be heated to a high temperature to be able to start generating electricity. This study aims to manage the heat-up process of a SOFC by considering the three objectives of time duration, energy consumption, and temperature gradient, simultaneously. Mass flow rate (MFR) and rate of temperature rise (RTR) of the hot air, passing through the cathode channel of the SOFC, are considered as decision variables. The transient heat-up process is numerically simulated for six different MFR values (5-50 mg s(-1)) and six different RTR values (0.1-5 K s(-1)). The results indicate that higher RTR leads to lower heat-up duration, lower energy consumption, but higher temperature gradient. Also, higher MFR results in lower heat-up duration, lower temperature gradient, but higher energy consumption. The results also reveal that hot air recycling increases thermal efficiency from below 40% to nearly 100%. Finally, when hot air recycling is employed and all the objectives are considered simultaneously, the heat-up plan with a RTR of 0.5 K s(-1) and a MFR of 50 mg s(-1) is selected as the best choice by using linear programming technique for multidimensional analysis of preference.