At first glance, hydrogen fuel cells sound like a great power source for fixed-wing drones making long flights – they have much longer run times than batteries, and they emit no emissions other than water vapor. Unfortunately, the hydrogen typically has to be stored in large heavy pressurized tanks. Last month, however, a Raptor E1 electric drone made a successful test flight running on a unique new system that's actually lighter than the lithium-ion battery it replaced.
The flight was carried out on Jan. 19th at Scotland's Oban Airport, by a team from the Scottish Association for Marine Science (SAMS). Although the flight only lasted 10 minutes with the drone cruising at an altitude of 80 m (262 ft), the fuel cell reportedly had enough fuel to fly for two hours.
That fuel took the form of approximately 100 small solid pellets contained within an unpressurized cartridge. Made by Britain's Cella Energy, those pellets are composed of a proprietary chemical compound, and they steadily produce hydrogen gas when a small amount of heat is applied. The Arcola Energy-manufactured fuel cell converts that gas into electricity, which was used to power the drone's motor.
According to Cella, the pellets (which measure 1 sq cm each) are stable during rough air travel, and at temperatures as warm as 50º C (122º F). Pressurized hydrogen, by contrast, must be stored at very low temperatures.
"This flight used a small prototype system and we were pleased with the initial flight, with another flight scheduled to take place in the near future," says Cella's Managing Director, Stephen Bennington. "The larger versions of this system that we are already designing will have three times the energy of a lithium-ion battery of the same weight."
Ultimately, the technology may even be integrated into full-size passenger-carrying aircraft.
Source: Cella Energy via New Scientist
This could definitely have applications in aviation or drone use (particularly military where cost is less of an issue).
Regarding flight time, in any experiment you certainly don't try to test all possible variables at once. As this drone is not some toy-store item, but a serious aircraft, it would be stupid to "see how long it will fly for", and most likely end up trashing the craft.
Also, it is not true that hydrogen cannot be produced cheaply enough to drive cars. It most certainly can.
The problems, and major cost and performance issues, are not related to PRODUCING it. Rather, they are with storing and transporting it.
Storage is relatively risky, and SAFE storage is relatively heavy. Transporting it is likewise difficult and (relatively) dangerous, plus there is the difficulty of transferring it from one storage container to another. (I.e., from storage tank to rail or truck, from truck to fuel station, from fuel station to automobile.)
Further, hydrogen represents a large amount of usable energy by weight, but not so much by volume. Even liquified, it takes a lot of hydrogen to go very far in a car.
A Tesla has a lot of batteries for a relatively (compared to ICE) short range, if the energy density is a lot lower than lithium-ion then the vehicle size would be prohibitive.
Hopefully not though!
As for the application itself, how big are the pellets by volume i.e. one square centimetre by how long? And what is their shelf-life?