Proposal: a giant photovoltaic balloon oriented towards the sun by motorized belts, and flying during the day with the aerostatic thrust from the air heated by the solar diametrical wall (like on the photo below); and flying at night by utilizing the wind, possibly nocturnal low-level winds (NLLJs), using the Magnus effect through rotation in yo-yo mode, keeping heat enough to compensate for its weight.
That said, a double envelope (like on the photo below, but with also a cylindrical shape) would be a (more expensive) solution to escape to the requirement of orientation to the sun, and flying by Magnus effect night and day, while producing solar energy by day with the internal envelope.
