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Compact, Lightweight, Power-Dense, Integrated Fuel Cell System

Description:

TECHNOLOGY AREA(S): Space Platforms, Weapons 

OBJECTIVE: Develop a lightweight, compact, drop-in and highly efficient integrated fuel cell-based hybrid propulsion and power system. 

DESCRIPTION: Navy energy action goals, as released by SECNAV [Ref 1], include developing more efficient systems, reducing greenhouse emissions, eliminating/reducing fossil-fuel usage, and increasing the use of alternative green energy sources in the fleet. Therefore, future power sources must extend operational range and lower maintenance cycles [Ref 2]. Currently, combustion engines that use petroleum fuels are relied upon to provide thrust and drive motors to propel the aircraft. The fuel-to-power conversion efficiency of the combustion process is low (i.e., can be as low as 15%), resulting in high fuel consumption and harmful gas emissions. The use of batteries is attractive as an alternative energy source for unmanned aircraft systems (UAS), where geometric limitations prohibit the use of combustion engines. However, their low energy density (less than 200 Watt-Hour/Kilogram) prevents the widespread use of battery power sources as the primary mover for the aircraft. Fuel cell technologies (FCT) allow the reformation of jet fuel into hydrogen-rich gas, resulting in usable electric power with high conversion efficiencies (i.e., 60-70%). FCTs are solid-state devices with the following characteristics: high energy-density; clean fuel burn resulting in water, heat, and air as byproducts; contain no movable parts which enable quiet operations; maintenance free over the lifecycle; and are scalable. These characteristics translate to improved mission performance and warfighting capabilities, including potentially doubling endurance time to 44 hours in some cases, and reduced weight (<135 pounds) [Ref 3]. There are four key components in a fuel cell system: (1) reformer converting logistic fuel (i.e., JP-5/JP-8) into usable hydrogen (H2) gas; (2) fuel cell stack that produces electrical power output upon receiving a fuel such as H2 gas as an input; (3) balance-of-plant consisting of burners and heaters for combined heat and power to improve efficiency; and (4) electronic firmware with hardware components and software algorithms along with controls. There is a need for integrating the above key components to develop an integrated fuel cell system (IFCS) to leverage the full potential of fuel cell technologies. The current market lacks such IFCS that are highly dense (i.e., power and energy density), and operationally suitable for aircraft applications. The goal is to develop a baseline IFCS that produces a minimum electrical power output of 0.5-1 kilowatt (kW). The design concept must be scalable up to 5-10 kW as well as be modular and plug-and-play in nature. Based on the fuel source, a polymer membrane (PEM) fuel cell or solid-oxide fuel cell stack can be used. The fuel cell stack must be fully compatible with current industry and state-of-the-art onboard (e.g., reformer and H2 storage system) and off-board hydrogen technologies (i.e., electrolysis). The developed IFCS must have a total weight threshold of 35 pounds (lbs) {15.9 kilograms (Kg)} with an objective of 19lbs (8.6Kg). The IFCS must also be fully compatible for Groups I-IV UAS vehicles [Ref 4]. The developed IFCS must be compatible with all current operational aircraft, electrical and environmental requirements [Ref 2, Ref 3], and must meet other requirements that include (but are not limited to) the following: sustained operation over a wide ambient temperature range (e.g., -40°C to +71°C), capability to withstand carrier-based shock and vibration loads, altitude range up to 65,000 feet per MIL-STD-810G [Ref 5], electromagnetic inference (EMI) up to 200V/m per MIL-STD-461F [Ref 6], and electrical power quality per MIL-STD-704 [Ref 7]. 

PHASE I: Develop a baseline IFCS that produces a minimum of 0.5-1 kW of electric power. Leverage modeling and simulation tools for proof-of-concept. Show feasibility for air vehicle integration to unmanned aircraft system. The Phase I effort includes the development of prototype plans for Phase II. 

PHASE II: Build a prototype system that is compact and lightweight, and then demonstrate the functionality of the IFCS suitable for a UAS meeting its propulsion and power needs. Demonstrate the scalability of the IFCS to 10kW. 

PHASE III: Fully develop a functional and airworthy IFCS with performance specifications satisfying the targeted acquisition requirements coordinated with Navy technical points of contacts. Complete testing per military performance specifications and transition to appropriate platforms. Commercialize the fuel -cell and IFCS technologies. Leverage the advantage of scalable manufacturing processes to develop a cost-effective manufacturing process for technology transition to various system integrations for both DoD and civilian applications. The potential for commercial application and dual use is high. Beyond the Navy application, there are applications for electric vehicle, consumer portable electronics, and commercial aviation sectors. 

REFERENCES: 

1: Paige, Paula. "SECNAV Outlines Five Ambitious Energy Goals." Navy News Service. 16 Oct 2009. Story Number: NNS091016-30. Corporate Communications ONR. http://www.navy.mil/submit/display.asp?story_id=49044

2:  FY15 Navy Programs. RQ-21A Blackjack Unmanned Aircraft System (UAS). http://www.dote.osd.mil/pub/reports/FY2015/pdf/navy/2015rq21a_blackjack.pdf

3:  Naval Air Systems Command-Small Tactical Unmanned Aircraft Systems. "RQ-21A Blackjack". http://www.navair.navy.mil/index.cfm?fuseaction=home.displayPlatform&key=5909B969-2077-41C2-9474-C78E9F60798C

4:  "Unmanned Aircraft System Airspace Integration Plan", Version 2.0. Department of Defense UAS Task Force, Airspace Integration Integrated Product Team. March 2011. http://www.acq.osd.mil/sts/docs/DoD_UAS_Airspace_Integ_Plan_v2_(signed).pdf

5:  MIL-STD-810G. "Department of Defense Test Method Standard: Environmental Engineering Considerations Laboratory Tests". 31 Oct 2008. http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35978

6:  MIL-PRF-461F. "Department of Defense Interface Standard: Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment". 10 Dec 2007. http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35789

7:  MIL-STD-704F. "Department of Defense Aircraft Electrical Power Characteristics" 30 Dec 2008. http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=35901

KEYWORDS: Compact; Lightweight; Power Dense; Integrated Fuel Cell System; Propulsion And Power; Unmanned Aircraft System 

CONTACT(S): 

Venkatesan Manivannan 

(301) 342-0365 

venkat.manivannan@navy.mil 

Michael Melnyk 

(301) 342-5788 

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