A review of the impact of ambient conditions and degradation in hybrid fuel cell powered unmanned aerial vehicles

Abstract

Hydrogen fuel cells (FCs) integrated into unmanned aerial vehicles (UAVs) are considered a sustainable technology enabling long-endurance missions using electric propulsion. This paper reviews the current state of the art in the energy system design of fixed-wing UAVs using FCs. The power profiles of UAVs are highly dynamic, and power surges are possible, requiring hybridisation. We review the commercially available PEMFCs specifically designed for UAVs. Moreover, we discuss the management of operating conditions and show that, due to mass considerations, PEMFCs for UAVs are supported by a simplified balance of plant. Therefore, PEMFC UAVs may experience lower performance and shorter lifetimes due to increased exposure to ambient conditions and higher degradation rates. This necessitates further research as it could limit the deployment of PEMFC-powered UAVs. In addition, it is advised to consider these effects when designing PEMFC UAVs hybrid systems. Besides taking durability into account, we identified clear knowledge gaps. They originate from a lack of guidelines focusing specifically on the selection and dimensioning of hybrid electric systems for PEMFC UAVs. A stepwise approach is proposed to assess the commercial feasibility of PEMFC UAVs for realistic missions, focussing on the applicability, performance, and lifetime to move beyond the demonstration phase.