Wind powered car

[Ryland]

Originally Posted by whostean

"It runs on batteries and electric generators that are recharged by a fan at the front of the vehicle and two ‘solar energy wings’ on the back that sustain electricity generation"

If those solar panels are good for a mile per day of range then what they say could be 100% true... if the fan idea really does work then why have solar panels at all?

[ChazInMT]

Originally Posted by whostean

Sorry to bring this thread back from the grave, but I was under the impression this guy's car only used the wind turbine to recharge his battery?

Whostean, ya do realize that the energy required to run a turbine has to come from the motor of the car, so it would be a perpetual motion machine for a turbine powered generator to charge the battery to run the motor to push the car to make wind to run the turbine to charge the battery to run the motor.....if you reach down and try to pick yourself up by your own shoelaces you get where the problem lies within this system.

[jamesqf]

Originally Posted by ChazInMT

Whostean, ya do realize that the energy required to run a turbine has to come from the motor of the car...

No, at least not if I understand it correctly. The energy comes from whatever wind is blowing when you subtract the motion of the car.

One way to think about this is if you took the turbine off the car, put it in your yard, and used it to charge batteries. That would work, wouldn't it? So why wouldn't it work with the turbine on the car? Of course efficiency is another matter :-)

[UFO]

Originally Posted by jamesqf

No, at least not if I understand it correctly. The energy comes from whatever wind is blowing when you subtract the motion of the car.

One way to think about this is if you took the turbine off the car, put it in your yard, and used it to charge batteries. That would work, wouldn't it? So why wouldn't it work with the turbine on the car? Of course efficiency is another matter :-)

How do you separate it from the drag induced by said wind? Even if the turbine is 100% efficient, that nets 0 gain.

[zapato]

Originally Posted by UFO

How do you separate it from the drag induced by said wind? Even if the turbine is 100% efficient, that nets 0 gain.

And the theoretical limit for a wind turbine is ~67% efficiency. After that, not enough air is making it through the turbine to actually turn it.

The only way this could work is with a retractable air dam that only opens when braking. Otherwise any headwind benefits would be swallowed by the increased drag to the tune of ~1.5 [unit] lost per [unit] gained.

... besides, it's from FOX News...

[rmay635703]

The full scale models i saw that worked used the prop attached directly to the wheels to go into the wind.

this is a proven unicorn, as for charging batteries i can't say I ever noticed that on any of the working models in existence.

[Patrick]

Here are the real wind powered cars: The remarkable first race for wind-powered vehicles

[jamesqf]

Just think about it in steps. Say you've got your wind-powered vehicle, as in the picture in that linked article. It's stationary, and the wind is blowing - say a 30 mph headwind, just to make things simple. So the wind turbine can capture energy from a 30 mph wind at whatever efficiency, and transfer it to the wheels. This means that the vehicle starts moving at say 1 mph. Drag increases, but so does the apparent wind, which means the speed can keep increasing until the energy captured is just sufficient to overcome the total drag. Seems pretty obvious, and as the article shows, it does work.

[UFO]

It's fascinating and counter-intuitive.

[Ryland]

Originally Posted by jamesqf

Just think about it in steps. Say you've got your wind-powered vehicle, as in the picture in that linked article. It's stationary, and the wind is blowing - say a 30 mph headwind, just to make things simple. So the wind turbine can capture energy from a 30 mph wind at whatever efficiency, and transfer it to the wheels. This means that the vehicle starts moving at say 1 mph. Drag increases, but so does the apparent wind, which means the speed can keep increasing until the energy captured is just sufficient to overcome the total drag. Seems pretty obvious, and as the article shows, it does work.

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.