Design of all electric secondary power system for future advanced medium altitude long endurance unmanned aerial vehicles

System for unmanned aerial vehicles (UAV) advanced alternative energy (SAvE) is a research project funded in 2007 by Piemonte Regional Government, Italy, and assigned to Politecnico di Torino and Alenia Aeronautica. Aim of the project is the study of new, more efficient, more effective, and more environmentally friendly on board systems for future advanced UAV, particularly for future advanced medium altitude long endurance (MALE) UAVs. This article deals with the analysis and design of the all electric secondary power system of a future advanced MALE UAV that is considered as 'reference aircraft'. After a thorough trade-off analysis of different configurations of the secondary power system, the hybrid fuel cells configuration, characterized by starter/generators, fuel cells, and traditional and innovative batteries, has been selected as the most promising. Detailed investigations to find the best way to apportion the supply of secondary power, considering the various power sources (starter/generators, batteries, and fuel cells) in the different modes of operations, have been performed thanks to an integrated simulation environment, where physical, functional, and mission scenario simulations continuously exchange data and results.