They are energy collectors, I would assume you use some of that energy to heat the air in their balloons.
I'm more interested in how you optimally position the solar cells, would a sphere really be the best or would a pontoon dragging in the wind give a better chance for the solar panels to receive optimal light? You probably don't want that 20km tether to be twisted too many times either.
Interesting point about placement --- seems like a dense array of these would be at risk of getting tangled. And then there's the risk of the tether / cabling becoming a conduit for electrostatic discharge. Of all the engineering issues here, I think tethering is the most problematic.
> I can't imagine many people wanting to live near 20km electrically charged cables, never mind pilots flying between them in a high wind.
Not being able to imagine something, and other people not being able to do it, are not functionally equivalent.
Lots of people live within 20km of much more dangerous structures already. But there are plenty of places that people live > 20km away from because they're considered a high risk. So, take your pick on that one.
Pilots already have experience at not flying in certain places - environmental reserves, war zones, hurricanes, mountains, etc - they're pretty good at reading maps.
> Having to build a long way from urban areas rather reduces the advantages of such a system over solar farms in the desert.
I'd suggest you refer to the article again for the proposed benefits of having these things above cloud level, rather than on the ground.
Currently (npi) most power generation occurs much more than 20km from the primary urban areas that they provide power to.
Put some propellers on the balloons, and a computer to control them.
If we can get drones to avoid trees while flying through a forest at high speed, we can make balloons maintain a safe distance from one another at an altitude way above most storms.
I'm more interested in how you optimally position the solar cells, would a sphere really be the best or would a pontoon dragging in the wind give a better chance for the solar panels to receive optimal light? You probably don't want that 20km tether to be twisted too many times either.