I did: Your batteries have to provide 600W continuous for 18 hours (actually more as that was the power needed for a controlled decent), and your solar panels

I did: Your batteries have to provide 600W continuous for 18 hours (actually more as that was the power needed for a controlled decent), and your solar panels have to provide that same energy in your 6 hour 'solar day'. In addition, the solar panels would need to provide another 600W for 6 hours in order to run the motors whilst charging the batteries. So that's 10.8KWhrs of batteries, and 2400W/hr or 14.5sq m of solar panels. That translates to 108KG of batteries and 29KG of solar panels using your weight to power ratios - 137KG in total, compared to the rider at 75KW, so your 24 hour solar bird is a sadly flightless before even adding motors, gearboxes electronics and cabling.