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MacG
MacG is offline
#42
Mar31-08, 02:35 PM
P: 3
Quote Quote by Sjonnie View Post
Such a car has been build at the Delft University of Technology. It worked. One of the important aerodynamic aspects of using wind energy is the LIFT principle. When a horizontal axis windturbine has wing-shaped rotorblades it will be able to rotate faster than the windspeed. This means a higher efficiency than drag-based windturbines.

However even with drag-based windturbines such a vehicle can be build. The drag of the vehicle should be minimized as much as possible. EXAMPLE: http://www.zeiltheorie.nl/wagentje.html

Yes. The final results from the theory I stated in my first post only apply to (ideal) lift based wind turbines.
However, the equation for determining the top speed
P/V=T
is always valid when neglecting drag on the rest of the car, rolling resistance and mechanical loss in the teansmission.
Including these contributions the equilibrium equation for determination of the top speed would look like this:
EtaMech*P/V=T+Dcar+RollResist
EtaMech is due to mechanical loss in the transmissin, Dcar is the car drag (~Vrel^2) and RollResist is the rolling resistance of f the car.
The interesting thing here is that from this expression it can be seen that any wind energy converter can make a car go in the upwind direction (as long as the power production is above zero), since the left hand side term can be as big as we want it to if the (car) velocity is low enough.
So it will move upstream with any wind energy conversion system. The question is how fast. One important parameter in that is the relationship between P and T, and this is much better for lift based conversion systems than for drag based, as you mentioned.

The link you supplied was fun.
Do you have any links for the Delft University wind turbine car?

-Mac G