A solar balloon is a black balloon that is filled with ordinary air. As sunlight shines on the balloon, <answer>the air inside is heated and expands causing an upward buoyancy force</answer>, much like an artificially heated hot air balloon. Some solar balloons are large enough for human flight, but usage is generally limited to the toy market as the surface-area to payload-weight ratio is relatively high.
What happens when sunlight shines on a solar balloon?
the air inside is heated and expands causing an upward buoyancy force