Start with a frame similar to what you'd use for a landsailer: triangular, with two fixed-direction front wheels, and a steerable rear wheel.
Add to the vehicle a deep cycle battery, such as you'd use on an electric vehicle. Also add a motor/alternator to the rear wheel, and a speed controller which can slow the vehicle in a way that charges the battery (regenerative braking).
Add a Flettner rotor as a sail, with an electric motor / alternator to speed/slow it. This should have a speed controller, which can transfer the rotational kinetic energy of the rotor, into battery energy.
Use some battery power to maneuver to some place where you've got a good side wind, then spin up the rotor. This will provide lots of forward thrust -- more watts of thrust, than are being expended keeping the rotor spinning.
Use the wheel motor, in regenerative braking mode, to change some of the generated forward kinetic energy into battery energy.
If the battery is full, and we're moving as fast as we want to, excess energy can be dealt with by spinning the rotor faster. If the rotor's at full speed, either run extra electricity through a resistor, or apply brakes.-- goldbb, Oct 07 2009 Flettner rotor http://en.wikipedia...wiki/Flettner_rotor [normzone, Oct 08 2009] North American Land Sailing Association http://www.nalsa.org/Landyacht world speed record set. 126.2mph (March 2009) [goldbb, Oct 08 2009] A transport for a windy day or else it would be electrically expensive.-- wjt, Oct 08 2009 such a device would be fantastically drag inducing. Only in very high winds, or tail winds, would this be a viable idea.-- WcW, Oct 08 2009 //very high winds// and pretty respectable overhead clearances, as well.-- lurch, Oct 08 2009 wtj, lurch: consider that a Flettner rotor is little more than a cylinder with circular fins (disks) attached to it. It could be made collapsible, like a collapsible camping cup.
This would reduce drag when you need to drive when there's no wind, or when you need to drive in the exact same direction as the wind (either into the wind, or away from and faster than the wind).
WcW, in a direct tailwind, a Flettner rotor provides no more forward acceleration than any other large, drag-inducing object. However, if the wind angle is more than 20-30 degrees away from being a pure tailwind, the rotor does provide a substantial thrust boost. Given that a wind powered vehicle, with a conventional sail needs to be about 45 degrees to the wind for best acceleration, this is pretty good.-- goldbb, Oct 08 2009 How fast do you intend to go? In what speed winds? You see my point, right?-- WcW, Oct 08 2009 I intend for it to go just as fast as any other landsailer, or perhaps faster, and in the same wind speeds :)-- goldbb, Oct 08 2009 Sadly, this hybrid electric design wouldn't be able to set any records according to nalsa's rules, due to the batteries.
However, if the rotor were powered by the wheels in a battery free way, perhaps with a CVT transmission, it might be acceptable.-- goldbb, Oct 08 2009 random, halfbakery