A handful of little white pellets holds enough hydrogen to fill a good-sized balloon. At least, that’s the claim of executives at Cella Energy, a spinoff of Oxford University researchers. The blog has covered their work twice, once with their claim that their hydrogen pellets could replace gasoline for the equivalent of $1.50 a gallon, and once for showing a method for pumping fresh pellets into a fuel tank after extracting the spent pellets. Their latest project, partnering with L2 Aerospace, converts a small unpiloted aerial vehicle (UAV) to run on hydrogen powering a fuel cell. The partners have been flying the UAV since January, 2014 and are now showing it at different expos in America and Europe. The power supply, according to the partners, is quiet, emission-free, lightweight, and can be shaped to fit any application. In the current instance, the “tank” has a wing shape. The pellets have a shelf life of years. The prototype Cella Energy cartridge …