  Unmanned aerial vehicle (UAV) techniques have developed rapidly within the
past few decades. Using UAVs provides benefits in numerous applications such as
site surveying, communication systems, parcel delivery, target tracking, etc.
The high manoeuvrability of the drone and its ability to replace a certain
amount of labour cost are the reasons why it can be widely chosen. There will
be more applications of UAVs if they can have longer flight time, which is a
very challenging hurdle because of the energy constraint of the onboard
battery. One promising solution is to equip UAVs with some lightweight solar
panels to maximize flight time. Therefore, more research is needed for
solar-powered UAVs (SUAVs) in different environments.
