This news article is proving to be quite controversial here. Basically it's an electric car with a turbine bolted onto the front. On the face of it sticking a turbine on the front is going to increase drag and the intuitive assumption in that scenario is that the electricity generated in this case won't beat the extra electricity used to counter the increased drag.
However in the light of Blackbird, a land yacht noted for going downwind faster than the wind it seems harder to rule out the possibility that such a system could, at least in theory be more efficient.
What's the link between the two? Is the former as much of a hoax as it seems it ought to be? How does that get reconciled with Blackbird and other similar "dead downwind faster than the wind" vehicles?
I can see at least one important difference between the two cases that I missed when I first considered this problem. I initially assumed that the case of both vehicles going dead downwind at more than the true windspeed was identical, but that's not the case.
A key feature of the explanations of "downwind faster than the wind"1 I've seen is the fixed transmission in the case of vehicles like Blackbird. This transmission can run either way - with wind turning the wheels or wheels turning the blades. This is an important difference in the transmission of the two though. For the electric transmission in the car there's only ever transfer from the turbine to the wheels. For Blackbird that transmission can run both ways because it's just a few gears, so the wheels can drive the propeller as well. Without that DWFTTW won't work.
(Even with that the position of the turbine on the car is such that it would just be blowing air at the front of the car which wouldn't be terribly helpful either)
Which means that for the car case as far as I can see the only way it can possibly be a net gain is if the turbine inadvertently has the effect of reducing the drag (which might just be possible if it makes a blunt nose more curvy overall). Either way though there are far better ways of making it more streamlined so it seems incredibly unlikely that there's anything but pure quackery at play.
This might be a topic for a question on its own, but my original question presupposed that Blackbird is not a hoax. There is an existing question on this topic on physics.SE but the answers aren't brilliant.