Green Technology

... "Launched by hand, Zephyr is an ultra-lightweight carbon-fibre aircraft with a wingspan of up to 18 metres but weighing just 30 kg. By day it flies on solar power generated by amorphous silicon arrays no thicker than sheets of paper that cover the aircraft's wings. By night it is powered by rechargeable lithium-sulphur batteries that are recharged during the day using solar power. The trials validated recent modifications that have improved the efficiency of Zephyr's power system. These have included new solar arrays supplied by United Solar Ovonic, a full flight-set of Sion Power batteries as well as a novel solar-charger and bespoke autopilot developed by QinetiQ, all of which were being flown for the first time. " ...

Via QinetiQ: Solar plane record for longest duration unmanned flight