I've been following solar-powered aircraft for many years, ever since the BMDO's shadowy plan for a long-endurance anti-missile craft called Raptor ("Responsive Aircraft Program for Theater Operations" -this was long before the F-22 acquired the name). NASA's record-breaking solar HELIOS UAV disintegrated mid-air in 2003, but there has been a lot going on since then. Now British military spin-off Qinetiq has also started breaking records with the same concept.
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 combination of a UAV plugged into an endless source of energy with new electric-powered lasers or other DE weapons is a rather obvious one. (Megawatts not required: you don't need to burn through metal to knock out a target). I suspect there are already a number of black programs involving solar-powered UAVs in the US, and it will be interesting to see how soon the results emerge.