Wind powered car

[rmay635703]

Originally Posted by Ryland

The problem is that at 30mph head wind it's going to take 1,400 watts to keep the car from moving backwards with the wind! so 1,400 watts just to keep it standing still and more energy to move it forward, so at that point it needs a prop that is larger then the frontal area of the car to generate enough power to move it forward and that would work if the wind generator was stationary next to the car with a long cord but as soon as you put that turbine on the car it increases the frontal area by the swept area of the turbine.

This is why you need a very aerodynamic shape so the frontal area is mainly prop so most of the power can be geared into moving the car.

obviously the speed you would move in a non-aero large car would be very slow but it still has a break even point.

cheers

[Ryland]

The point of the prop still being seen by the wind as a solid disk as far as drag goes does not change and it takes energy to keep that prop from being pushed backwards, so unless you sit there with your brakes on for a while charging up the battery it's not going to move forward! I understand the idea of moving faster then the wind while being pushed by the wind but not moving straight in to the wind that is powering you.

[zapato]

Originally Posted by rmay635703

This is why you need a very aerodynamic shape so the frontal area is mainly prop so most of the power can be geared into moving the car.

obviously the speed you would move in a non-aero large car would be very slow but it still has a break even point.

No, the way wind turbine works prevents them from having a break even point - they convert wind force (i.e. drag) to electricity at less than 100% efficiency. Therefore they will always produce less propulsion than drag.

[jamesqf]

Originally Posted by zapato

No, the way wind turbine works prevents them from having a break even point - they convert wind force (i.e. drag) to electricity at less than 100% efficiency. Therefore they will always produce less propulsion than drag.

Interesting that you can maintain that it doesn't work, despite links to examples of vehicles that are in fact doing it :-)

[UFO]

I would think you can always get some power out of it for movement into the wind due to mechanical advantage.

Actually it's quite brilliant. Read this article and the designer answering the critical comments...

http://www.wired.com/autopia/2010/07...ve-it/#respond

[zapato]

Originally Posted by jamesqf

Interesting that you can maintain that it doesn't work, despite links to examples of vehicles that are in fact doing it :-)

Find me a link from a reputable source and I'll reconsider.

[UFO]

Will this work?

Sailing faster than the wind - Wikipedia, the free encyclopedia

Details on the demonstration Downwind Noir: The Record

At least to demonstrate it is possible to exceed wind speed using wind power. Hint: levers give mechanical advantage. Iceboats and sailboat already do this, but they have to tack because they have fixed sails.

[Ryland]

those last few links are on going DOWN WIND faster then the wind, not going into the wind using the wind, the idea of going down wind faster then the wind does work and it's a fascinating bit of physics that makes it work.

taking one of this wind powered cars and turning it around to head in to the wind doesn't work because when you turn it around and start heading in to the wind it gets pushed backwards, with the wind.

[UFO]

Read about how high performance wind vehicles sail up wind, iceboats can sail within 10 degrees of the true wind. It's the same principle.

Here is the official site for the records the craft has set, both down the wind (2.8x wind speed) and into the wind (2x wind speed).

http://www.nalsa.org/DownWind.html

I was skeptical this morning, now I am coming to understand it better.

[Ryland]

appears legit... looks like I've been proven wrong! thanks! I kind of want to build one my self know, just to try it out.