The National Renewable Energy Laboratory (NREL) embarked on a year-long collaboration with Honeywell Aerospace in 2023 to prototype and support the commercialization of a novel cartridge-based hydrogen fuel storage solution for UAVs. The project, Fuel Additives for Solid Hydrogen (FLASH) Carriers in Electric Aviation, is a new hydrogen carrier technology developed at NREL within the HyMARC Energy Materials Network and is funded by the US Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy’s Hydrogen and Fuel Cell Technologies Office through DOE’s Technology Commercialization Fund.

Today’s long-range drones are typically powered by combustion engines. While they provide the required range that battery-powered electric UAVs lack, these engines have issues with excessive noise, vibration, and emissions, including carbon emissions.

FLASH seeks to deliver an alternative approach, in which efficient and long-lasting hydrogen storage is coupled to a fuel cell that continuously converts hydrogen to electricity to power electric UAV flight. That system would enable long-range flights, but without the carbon emissions of combustion engines. It would also enable sensitive drone applications such as atmospheric monitoring, where exhaust gases and rumbling engines would reduce performance.

FLASH is based on a mixture of borohydride and salts. Borohydrides are a class of solid materials with the highest gravimetric densities, however, the cost of borohydride fuel for such a drone application would be too high. The FLASH researchers are developing a formulation that can deliver 6 wt% H₂ at a maximum of $150/kg of fuel.

“FueL Additives for Solid Hydrogen (FLASH) Carriers for Electric Aviation”, Noemi Leick (P.I.), 2023 Annual Merit Review and Peer Evaluation Meeting

Mixtures of borohydride and salts can overcome current borohydride challenges such as high dehydrogenation temperature and mass transport, thereby allowing NaBH₄-based fuels that could meet the target of $150/kg.

This class of materials is remarkably tunable and therefore highly versatile to industrial hydrogen delivery requirements.

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The FLASH hydrogen storage technology and fuel cell could be bundled in a single, swappable cartridge that looks just like the batteries UAV owners are used to but offers significantly longer flight times. Honeywell Aerospace has already developed solid-state cartridge fuel systems for drones and is looking to improve their performance with the unique low-temperature, fast-release technology of FLASH.

Currently, FLASH operates as a one-way fuel that, once spent, needs to be recycled or refilled. A project in NREL’s Laboratory Directed Research and Development program is currently examining methods to recycle the fuel using electrochemical processes that could ultimately be powered with renewables.

If the NREL-Honeywell project is successful, FLASH will be qualified for future technological development in optimization, scaling, and cost reduction. This work supports decarbonization of the aviation sector and the creation of high-tech jobs in the United States. Some of the potential large-use cases for hydrogen-fueled UAVs include inspections of electric power lines, gas pipelines, solar panel farms, wind turbines, and other applications where flying on long missions, beyond the line of sight of the operator, would save money and improve reliability, lowering the cost of renewable energy applications.

Honeywell Aerospace will provide the technological expertise, platform materials testing for fuel cartridge technology, supply chain logistics insight, prototyping, and fuel cell evaluation to qualify FLASH for further development. In Phase I of the project, NREL will provide technical expertise on FLASH formulations, fabrication, and characterization of the hydrogen fuel storage.

Taken together, the collaborative research will determine the most promising FLASH formulations, develop a prototype FLASH fuel cartridge for Honeywell application platforms, and conduct a fuel cell test with the FLASH cartridge.

A non-provisional patent application on FLASH was filed with the US Patent and Trademark Office. Through the support of this TCF award, Honeywell Aerospace will have the foundation to continue the development of FLASH toward commercial deployment.