Study and Analysis of Unmanned Air Vehicles (UAV) Power System Energized by Fuel Cell

Abstract

Unmanned Air Vehicles (UAVs) have gained much popularity in several military and civilian applications. Reconnaissance and surveillance are among military applications that require small aircraft size, low acoustic and heat emissions, to decrease the possibility of visual, audio, and thermal detection to perform their missions. Internalcombustion- engines have usually heavy weight and large size, in addition of having high acoustic and heat emissions, therefore UAVs powered by electric motors are preferred for such applications. Electric motors play significant role in electric UAVs. Brushless Direct Current (BLDC) motors have gained many advantages over other motor types; such as higher reliability and efficiency, compactness, longer operating life, higher dynamic response, better speed versus torque characteristics, noiseless operation, and higher torque-to-weight ratio. Due to these advantages, BLDC motors are selected as propulsive motors for electric UAVs. Batteries are considered the conventional sources for powering electric UAVs. Unfortunately, batteries do not offer enough power for a long duration flight due to their low energy density and their longer charging time. Therefore, this thesis is focused on the development of powering UAVs by renewable and clean energy sources. Several renewable energy sources are available such as supercapacitors, solar energy, and fuel cells. Each source has its advantages and disadvantages. Based upon reconnaissance application requirements and constraints, fuel cells have been selected as main energy source. Due to disadvantages associated to fuel-cells, a power supply system that combines fuel cells and batteries is utilized to allow exploitation of the advantages of both devices and undermines their disadvantages.