Performance analysis of a hybrid aircraft propulsion system using solid oxide fuel cell, lithium ion battery and gas turbine

Abstract

A novel integration of a solid oxide fuel cell (SOFC), lithium ion batteries and a gas turbine propulsion system is proposed for a hybrid electric aircraft. Methane as hydrogen storage medium is fed to the propulsion system so as to avoid the limitations associated with the use of pure hydrogen storage and utilization. An internal reformer is used in the SOFC to produce hydrogen through the steam reforming and water–gas-shift reactions of the methane and steam mixture. An afterburner is used to generate the heat required for generation of electrical power in the gas turbine and preheating the SOFC reactants by burning the remaining fuel from the SOFC. Also, a pathway for liquid water input to the hybrid system is designed in a way to first circulate through the lithium ion batteries to remove generated heat from them before it is used in the remainder of system. The variations of heat generation rate and temperature of the battery with time are predicted through electrochemical and thermal models. A performance assessment of the proposed propulsion system is conducted to investigate the compatibility and applicability of the system. It is found that at 1C (charge/discharge rate of battery), the average temperature of the lithium ion battery is maintained at about 28 °C through a water-based cooling process. The optimum net electrical power output and energy efficiency of the hybrid propulsion system are achieved at compressor pressurization ratio of 7.5. Furthermore, the net electrical power produced and energy efficiency of the hybrid propulsion system reach their maximum values (i.e., 6.6 × 106 W and 46.5 %, respectively) at a SOFC temperature of 775 °C.