Weight Estimation Method for a Hydrogen‒Lithium Hybrid Aircraft Based on a Power/Energy Mix

Electric aircraft are important technological means for achieving green aviation. However, owing to the low energy density of lithium batteries, lithium-powered aircraft face challenges such as a short range and low payload capacity. The high energy density of hydrogen fuel cells makes the hydrogen‒lithium hybrid power system an effective solution to these problems. This paper proposes a takeoff weight estimation method based on the hydrogen-lithium power and energy mixing strategy for the conceptual design of hydrogen-lithium hybrid aircraft. In this method, the concepts of the hydrogen–lithium power mixing ratio and energy mixing ratio are introduced. By analyzing the power and energy requirements of different flight phases, the optimal power and energy mixing ratios for the hydrogen–lithium hybrid system are determined to reduce the weight of the power system and increase the aircraft payload. This method was applied to estimate the weights of three different types of aircraft, and the impacts of the power/energy mixing ratios on the weights were analyzed in detail. The results show that the weight estimation error for the RX1E-A aircraft is less than 7%. By comparing the total weight of the aircraft under different mixing ratios, it is demonstrated that with appropriate hydrogen–lithium power and energy ratios, hybrid aircraft can effectively reduce the weight of the power system and increase the payload ratio.