January 19 marked the first flight by a Raptor UAS drone using pelletized hydrogen to power a fuel cell that generates electricity and makes the propeller turn.
Cella Energy, an Oxford-based enterprise, is now producing small quantities of their little green beads (just in time for Mardi Gras), filled with solid-state hydrogen. Claimed to have “two or three times” the energy per weight of the best of lithium-ion batteries, Cella’s pellets are designed to enable low-pressure transportation of hydrogen in a form that allows fueling to take place with a bit of magic sleight of hand. Looking like miniature green dumplings, Cella’s mix of plastic and encapsulated hydrogen has the advantage of using existing infrastructure, “with minimal alterations.” Think of the pellets as a dumpling with a hydrogen filling which can be repeatedly extracted and refilled. How many refillings is not stated at this time.
The pellets release their hydrogen into a fuel cell when they are heated to a “moderate” level. The “empty” pellets can be sucked from the fuel tank where they’ve done their magic and placed back in the fuel tank or truck in which they were stored. The depleted pellets are replaced by energy-laden ones. “One of the biggest challenges facing the roll-out of hydrogen cars is the investment in high-pressure filling stations.
Another magic trick regenerates the H2 in the pellets so they can once again be transferred to a waiting power plant or vehicle. Pellets are lyophilized, or freeze dried, to keep the stored hydrogen in place at room temperature.
Cella’s two stage hydrogen extraction uses a gas generator which turns the H2 gaseous, coupled to a fuel cell which burns the hydrogen and creates electrical power. The system is integrated by Arcola Energy, another partner in the project.
The Test Airplane
Raptor UAS’s Raptor E1 incorporated Cella’s power system and was flown by the Scottish Association for Marine Science (SAMS). Funded by a grant from Innovate UK, Trias Gkikopoulos of Raptor UAS teamed with Cella and Arcola to make a first-of-a-kind vehicle that points the way toward potentially longer missions and bigger craft.
According to UAS Vision, the airplane flew with 100 pellets, each capable of generating about a liter of hydrogen. The flight lasted 10 minutes, although it could have continued for two hours with the fuel on board. Cella points out that a larger system (which the partners are devising) could reach the goal of three times the energy density of lithium-ion batteries.
Cella claims its system is scalable, able to be increased in size to power larger aircraft, probably in the ultralight and personal aircraft range for now – but who knows where this development might lead?