N221-076 TITLE: Lightweight, Compact, and Cost-effective Gaseous Hydrogen Storage System

OUSD (R&E) MODERNIZATION PRIORITY: Autonomy;General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Air Platforms;Materials / Processes

OBJECTIVE: Develop a lightweight, compact, and cost-effective gaseous hydrogen storage system for Naval Aviation applications.

DESCRIPTION: Hydrogen fuel cells are gaining traction for propulsion and power requirements of small unmanned air systems (UAS) [Refs 1-4]. Compressed hydrogen is the most attractive form for hydrogen storage; however, flight-worthy storage vessels can be heavy, bulky, and expensive [Refs 5,6]. This can lead to sub-optimal vehicle designs by placing excessive volume constraints on UAS manufacturers for hydrogen fuel storage and added costs to users.

This SBIR topic seeks innovative concepts for low cost, high performance gaseous hydrogen (GH2) storage tanks for use in UAS. The Navy and USMC are interested in conformal and traditional storage vessels. Concepts include, but are not limited to, (1) conformal storage tanks that fit into either vehicle wings or non-traditional air vehicle form factors [Ref 7], and (2) novel coatings and materials for Type IV tanks that reduce cost without sacrificing robustness. The proposed concepts will be evaluated on their hydrogen storage performance metrics. Metrics include stored hydrogen weight per storage system (including regulator) weight, total volume of storage system, refill rate, manufacturability, and cost (dollar per system-weight of hydrogen stored). An understanding of how hydrogen storage systems can act as structural elements of the UAS is desired.

The GH2 storage tanks must be compatible with Groups I-III UAS including environmental, shock, and vibration requirements of MIL-STD-810H [Ref 8]. Solutions must demonstrate the safe operation of the vessels including fill, storage, and use of hydrogen [Ref 9]. Solutions must also show refill capabilities using standard interfaces and a cycle lifetime of over 1,000 cycles.

The storage system designs should focus on:

• 200 g minimum GH2 stored, can perform trade study on size and weight impacts for >200 g
• Operating pressures from 350 to 700 bar
• Storage minimum of 7 wt% GH2 per storage system
• UAS integration

PHASE I: Develop a conceptual design of a gaseous hydrogen (GH2) storage system for a minimum of two hundred grams (200 g) of compressed GH2. Identify and model the trade space for key storage system characteristics. Show feasibility for the integration into the Unmanned Aerial System (UAS) through the use of conceptual drawings or modeling and simulation. Perform initial analyses on GH2 consumption rates based on government-selected fuel cells and UAS propulsive and power requirements to meet UAS endurance targets. Produce a final Phase I report that includes plans for a storage system that stores 200 g GH2 and does so at operating pressures from 350-700 bar with a storage minimum of 7 wt.% GH2 per storage system. Develop a Phase II plan.

PHASE II: Build a prototype GH2 system that is lightweight, compact (>20g H2/L), safe, and cost-effective.

PHASE III DUAL USE APPLICATIONS: Incorporate the system into existing and/or future UASs of defined form factors. Target development of larger GH2 storage systems. Work with the DoD and partners to mature and manufacture products to produce systems that are lightweight, compact, and cost-effective and can be used on UASs that require longer duration flight and highly adaptable form factors. The platforms of potential applicability do not rely solely on military UAVs, but also in UAVs for commercial/private use and the use of city and local governments and law enforcement. Smart agriculture, critical infrastructure inspections, and perimeter security are all likely dual-use applications.

REFERENCES:

1. Blain, Loz. "ZeroAvia�s Val Miftakhov makes a compelling case for hydrogen aviation." New Atlas, June 15, 2020. https://newatlas.com/aircraft/interview-zeroavia-val-miftakhov-hydrogen-aviation/.
2. Harrington. "Boost Commercial UAV Flight Times With Hydrogen Fuel Cell Technology." sUAS News, 26 April 2019. https://www.suasnews.com/2019/04/boost-commercial-uav-flight-times-with-hydrogen-fuel-cell-technology/.
3. Arat, H.T. and Sürer, M.G. "Experimental investigation of fuel cell usage on an air Vehicle's hybrid propulsion system." International Journal of Hydrogen Energy, Volume 45, Issue 49, October 2, 2020. https://www.sciencedirect.com/science/article/abs/pii/S0360319919337784#!.
4. Swider-Lyons, Karen et al. "Hydrogen Fuel Cells for Small Unmanned Air Vehicles." ECS Transactions, Vol. 64, Issue 3, 2014. 10.1149/06403.0963ecst
5. Hydrogen and Fuel Cell Technologies Office. (n.d.). "Hydrogen storage." Department of Energy. https://www.energy.gov/eere/fuelcells/hydrogen-storage.
6. Rivard, Etienne; Trudeau, Michel and Zaghib, Karim. "Hydrogen Storage for Mobility: A Review. Materials." Materials, Vol. 12, Issue 12, 1973. 10.3390/ma12121973
7. Scheffel, Phillip. �TUBESTRUCT integral high-pressure tube tank The basic idea is a single-tube structure of a wing, where the tubes are loaded under high internal pressure as well as able to absorb thrust and torsion loads from stresses in the flight. The tubes can absorb hydrogen, methane or other volatile gases." Patent DE102015008178A1, February 2, 2017. https://patents.google.com/patent/DE102015008178A1/en.
8. US Army Test and Evaluation Command. "MIL-STD-810H, Department of Defense test method standard: environmental engineering considerations and laboratory tests." Department of Defense, January 31, 2019. http://everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810H_55998/.
9. Safety of Mobile Hydrogen and Fuel Cell Technology Applications: An Investigation by the Hydrogen Safety Panel, PNNL-29341, October 2019. https://h2tools.org/sites/default/files/Safety_of_Mobile_Hydrogen_and_Fuel_Cell_Technology_Applications-Oct_2019.pdf.

KEYWORDS: Hydrogen; Unmanned Aerial Systems; UAS; Conformal; Fuel Cells; Lightweight; Cost-effective; Sustainability