Makes sense. So you're saying there is no way to put the baloon inside without air getting in and created electricity comes from using force to put the baloon in vacuum.
I hadn't considered that part; perhaps there could be two airtight compartments at each end of the tube. Place the balloon in the tube and then seal it shut.
Let's say you've created a very large balloon that doesn't explode in a vacuum and filled it with a gas lighter than air. Next, attach the balloon to a basic electric generator with a very light rope and place the balloon in a vacuum tube. Due to the balloon's weight, it will descend in the...