There are a few ideas I really like and want to explore:
1) Foam Frame cut by CNC with covering film. This seems to work really well. It is very light and strong. Covering film is normally used over a balsa wood frame. I had not seen it used over a foam frame before. This is lighter, more resilient in crashes, and faster/easier. So far this seems like a great method.
2) Wing tip motor/propellers. I think this will be extra efficient. I can't find either real planes or RC planes that have tried to get extra efficiency from this. The propellers will rotate in the direction to counteract the wingtip vortices on that end of the wing.
3) Differential thrust so no vertical stabilizer. With two propellers we don't need a vertical tail, so can get rid of this drag. Extra efficient. Other people have done this. With 2 props on wing tips and a flight controller running iNav this is no extra trouble.
4) No solar charge controller. We will connect the solar directly to the battery or supercapacitor. We will use the flight controller computer to monitor the voltage and increase power to motors if the voltage is above the MPPT voltage and reduce is it is below. This should keep the solar panels at the optimal voltage without any extra power conversions or extra hardware/weight. By using a lithium-ion pack we can avoid the balance charger needed in a lipo battery. I asked about it on iNav Fixed Wing Facebook group.
5) Super-capacitor. A super capacitor can handle the full 92 watts solar we are thinking of and higher bursts of power for takeoff or aborted landing. Seems even enough power for VTOL. A solar VTOL would be very fun.
6) Computer vision/AI for precision landings, flying between clouds to maximize solar, searching for lost fishermen or illegal fishing ships, etc. The Jetson Nano is like 135 grams and 5, 10, or 20 watts and crazy powerful. So you can get plenty of computing power in a tiny airplane. The ArduPilot software supports Nvidia Jetson family as a Companion Processor. For example, here is how one Flight Controller is connected to a Jetson. You can buy a quadcopter with a Jetson Nano and FC. The Autonomous Drones Labs uses Jetson Nanos.
7) Crowd Researched project. I think we can do this where lots of different people all around the world can make advances on this project and earn prize money. If we can get crowd funding as well, then we could have larger prizes and more interest.