How does the kite pull a vehicle around a figure eight track, given a constant wind direction?

"vehicles on the ground that are pulled around a circuit on rails by the power of the wind" The kite can pull the vehicle only half the circuit, what will bring the vehicle around the second half?against the wind.

I believe the article explained that. "The developers of the system say a kite flying in a figure-eight or sine-wave flight pattern can generate a pulling power of up to 10 kilonewtons"
And the kite can be controlled in its movement as noted below
"The ground vehicles would also contain the measuring and control technology with a horizontal and vertical angle sensor located in each cable line and a force sensor within the cable distributor enabling precise control of the kite’s movements"
So the kites can fly in figure eights and probably can pull the cars in either directions.

It can pull around a track because it is not a parachute.

I would think somthing like a tacking manuver, like a sailboart, adjusting the tension on the lines would allow for a complete "circuit" of the track...

This works like 'tacking' in sailing. The angle of the kite is changed to pull the vehicles around the circle. See "sail karts" for example of this.

The kite may be doing a figure 8, much like a stunt kite, but I am guessing the track will be more like a hot dog or ellipse shape rather than circular. The kite can be feathered when the cart reaches the ends, maintaining enough kinetic energy to get around the curve, then off we go again, like a wind surfer. And the rail/cart interface might be like a modern rollercoaster with a captured rail. How the kinetic energy is converted to power a generator is unanswered, maybe a friction wheel on the rail. I wonder if inductance is a viable option? And how does the electricity get from the cart to the grid? A video simulation would have been nice. Still, way cool.

Sail powered craft manage to move against the wind, and a kite is only a form of sail.

To answer your question: by a steering maneuver. Just imagine a kid standing on the beach flying a figure eight. The kid doesn't move yet the kite does. Conversely, a steered kite under strong wind pressure will pull a vehicle through a figure eight or round track continuously. Trust me, if Fraunhofer is involved, it works.

Anyone notice "Sine Wave" Or "Figure 8"?