Yes but no.

Like yes, it is a method of harvesting energy from the sun but no because practically it’s going to lose out in efficiency and practicality to PV, solar thermal, or even just heating an area of ground and using the updraft to turn a turbine.

It’s so low energy density given you need to turn it into a electricity anyway. You’re losing out by the inefficiency of heat -> electricity (I think this pathway sucks because large entropy changes but my thermodynamics always sucked. It’s just worse than other routes), and you have really low power density, and it’s fragile and slow.

Compared to solar thermal which is already a bit dubious you can just concentrate sunlight on something, get it very hot, store heat in that (no loss due to atmospheric pressure changes either), and use it to then drive a standard steam turbine we’re pretty good at making approach max efficiency.

I suppose a big one could generate a small amount of electricity, but:

1. You’d run out of tether pretty quickly
2. Any wind at all makes retrieval more difficult
3. You’d be limited to areas with unrestricted airspace, which only exists in very rural areas

In short, not meaningfully.

This is just moving air, but a very small amount (the volume of the balloon).

When you want to capture energy from moving things (air, water) mass is king. And if you don’t have a lot of that, you better have a huge energy differential.