Lightweight, Modular Fuel Cell Systems for Unmanned Aircraft Systems

The Navy and Marine Corps are actively seeking to enhance the range, endurance, and payload capacity of their unmanned aircraft systems (UAS). In recent years, hydrogen fuel cells have emerged as a promising technology for propulsion and power systems that can improve UAS operational capabilities [Refs 1-4]. While various fuel cell types exist, proton exchange membrane (PEM) fuel cells are most prominently used for UAS applications [Refs 5-6]. However, further improvements to performance and reliability are necessary before widespread adoption into the services. This STTR topic seeks to explore any fuel cell solution that can meet the key performance, reliability, and design metrics required for integration into military UAS. The Navy is seeking a modular fuel cell system where the stack and balance-of-plant can be adjusted to meet a range of electrical power outputs from an initial 1kW to 20kW, with the potential to exceed 100kW. Proposals should address the following key system parameters: • Full system power-to-weight ratio of 500 W/kg, including the thermal management system. • Overall efficiency of 50% or greater (versus the fuel’s lower heating value) when operating at half of the maximum power output. • Rugged and reliable, capable of achieving over 200 full on/off cycles and a lifetime of 1,000+ hours with minimal maintenance. • Startup and shutdown time of less than 10 minutes. • Capable of operation up to 15,000 feet altitude. • Safe and hardened for military UAS applications. • Capable of starting and operating at both full power and idle in MIL-STD-810H basic hot and basic cold environments. • Adherence to shock and vibration requirements [Ref 7]. • An advanced monitoring and control system to autonomously optimize control parameters, maximize system performance, and provide health monitoring and diagnostics. Additional Considerations: • While gaseous hydrogen is the expected fuel, solutions using other fuels will be considered, especially if they offer logistical benefits. • Preference will be given to systems with minimal thermal and audible signatures. • Additional consideration will be given to solutions that can withstand the high g-force requirements of tube-launched systems.