Except when the wind isn't blowing.
And nobody steals the copper wiring on the ground.
I have the pleasure of operating a tethered balloon system in Afghanistan.
It won't only be when the wind isn't blowing, but, when the wind is blowing too hard.
Said balloon will have to be moored due to instability in high winds. Also, rain will cause too much of a positive pitch due to extra weight on the stabilizers, disrupting air flow through the turbine shaped balloon. Lightning in the area will necessitate the mooring also, it's a flying grounding rod. Lightning within 20 miles can be attracted by it's conductivity. The tether will have a ground in it, along with the power lines, that will provide a highly conductive electrical path at flying altitude.
The amount of flight time that will be achieved doesn't jibe well with their estimates.
The manpower needed to tend to it will offset the benefits of this intermittent source of power.
Another pipe dream.
Once you get above 1000 feet the wind tends to be steady, even if it’s calm on the ground. This sounds like a very good way to get power to off-grid locations.