Where the extra energy comes from?

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 tube, generating some electricity. After that, remove the balloon from the tube and allow it to rise in the atmosphere to the upper end of the tube. Now, the balloon is back at the starting position with the same potential energy, and you have generated some electricity. Where does the electricity come from?

How do you get the balloon in and out of the vacuum?

PeroK said:

How are you getting the balloon in and out of the 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.

habiler said:

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.

Do you think that might take some energy?

PeroK said:

Do you think that might take some energy?

Why? If you make compartments just enough size to fit the baloon inside and tube will not get any air inside.

habiler said:

Why? If you make compartments just enough size to fit the baloon inside and tube will not get any air inside.

I don't see how you can get a balloon into a vacuum chamber without the air getting in. The balloon is, by your own design, lighter than air. I would say that the chamber would fill with air unless you forced the balloon in. I don't think you've thought this through!

PeroK said:

I don't see how you can get a balloon into a vacuum chamber without the air getting in. The balloon is, by your own design, lighter than air. I would say that the chamber would fill with air unless you forced the balloon in. I don't think you've thought this through!

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.

habiler said:

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.

That's one problem. Attaching the balloon to an external generator is another.

PeroK said:

That's one problem. Attaching the balloon to an external generator is another.

Ok i got it thanks for the help.

We don’t discuss perpetual motion machines here, so I have closed the thread.

habiler said:

So you're saying there is no way to put the baloon inside without air getting in

Even if you could form an airtight seal and never get any leaking, you still would not get free energy. To extract the balloon itself requires you to displace the air. Essentially you have to lift the atmosphere. This is more than the energy extracted on the way down. All buoyancy based perpetual motion machines that I have seen neglect that. They neglect the fact that at some point you have to lift or displace the external fluid.