Wind turbine towers have been getting higher because wind at altitude is more consistent and stronger than near the ground. So there’ve been some attempts to move the turbines up higher than towers can reach by attaching them to kites or whatever. The Makani that Google had is one such. SkySails is another company that’s doing it (not sure how viable they are). Now a Chinese company has a balloon-mounted system that they’ve even connected to the local grid:
Not sure how viable this is. It’s going to have a fair amount of ongoing costs (helium, for example), so it may not pan out in the long run.
The one and only diagram that I have seen (which was based on a patent) showed a cable with a two-conductor core surrounded by a sheath for added mechanical strength.
To keep the weight low, the wires must be small gauge, of course. So I am assuming the output from the generator(s) is boosted to a pretty high voltage before it is sent down the cable.
The cable is attached to a winch. You just winch the thing down and stow it until the storm blows over.
As long as the cable doesn’t break, that’s going to limit how far away it can go horizontally from its winch point. Keep them that far away from houses and you don’t have to worry.
Besides, we’ve had big stuff attached to balloons for quite some time. When I was doing defense work back in the 1990s (airborne RADAR and FLIR systems) the company I worked for made tethered RADAR systems that were used for border defense and combating drug smuggling. I don’t ever recall hearing about any issues of one going rogue and crashing down on a house.
The diagram I saw (which again, was just one diagram and may not be indicative of other designs) did have a box labeled “transformer” near the base, so I assume they were sending it down the cable at a higher voltage to save cable weight.
This Tethered Aerostat Radar System - Wikipedia is probably smaller and lighter than the Chinese machines will eventually become. The tether consists of strength cable(s?) that retain the balloon so it doesn’t blow away, power cable(s?) to carry power up to the radar, and data cable(s?) back down.
Obviously copper power cables are less efficient in terms of tensile strength per pound of cable than typical steel cabling like a crane might use. But they do contribute to the overall hold-down strength of the combined system. So size the copper to carry the electrical and supplement that with however much steel cable alongside you need to manage the tensile load you have. It probably won’t be much steel. Certainly less than a steel-only cable would need.
Also obviously, it’s nicer to put your radar balloons or power generating balloons in places with steady winds and few significant storms. The Florida Keys are good at steady winds, but have plenty of thunderstorms, lightning, and the periodic odd hurricane now and then. It evidently works well enough to survive; the facility on Cudjoe Key has been there since the 1980s.
Like solar and ground-based wind, aerostat-based wind will have an intermittency problem. Which can practically be ameliorated with an adequate grid, diversity of sites, and diversity of sources. The Chinese will be able to install that easily enough. The USA? Hard to say.
I know some of the original funders and founders of Makani and they were very secretive about the cable. Apparently there was some very special sauce there. Not knowing anything about electricity, I can’t speculate.
They were also very bitter about Google. Supposedly they had a contract for additional funding upon meeting milestones and feel that Google reneged and then bought all their IP when they went under. “What are you going to do, sue Google when you have no money?”
It would be surprising if they only used two conductors. Three phase power requires less total conductor mass for the same power transmission. Perhaps they combine two conducting wires with a sheath that is also a third conductor?
A helium-filled Army aerostat intended to help NORAD detect threats in East Coast airspace became something of a threat itself when it broke loose from Aberdeen Proving Ground, Md., Wednesday, causing power outages as its tether hit power lines as it drifted into Pennsylvania.
State police used shotguns to deflate the aerostat, which came down Thursday near Muncy, Pa., about 80 miles north of Harrisburg in the central part of the state, the Associated Press reported.