use the air we drive through

[cfg83]

Ryland -

Originally Posted by Ryland

At 55mph a square foot of well designed propeller (not counting the hub), could in theory, at best produce 200 watts, that would be enough to maintain the electrical system on a gas car, but the average speed of a gas car is not 55mph for most people it's closer to 35mph, unless they pull out of their driveway right on to a freeway.
But that 55mph wind speed would need to be straight line air flow, no obstructions in front or behind it, at all.

Ok, thanks. 200 Watts / 12 Volts = 16.67 Amps. I have a lot of commute miles, but my average speed is sub-50 MPH because of the congestion. This is mostly a mental exercise for me. If I were to try this, it would be on condition that I get my hands on a cheap 12 volt motor. My main goal would be to make a chart of X amps at Y speed.

I think this is a job for a Studebaker :

http://ecomodder.com/forum/showthrea...tor-12076.html


And/or it's smaller sibling :


(it's so fast they have to chain it down!)

CarloSW2

[Frank Lee]

I suspect it wouldn't spin as nicely on the front of a car as it does on airplanes. Plus, airplanes don't have (much for) x-winds in flight.

[cfg83]

Frank -

Originally Posted by Frank Lee

I suspect it wouldn't spin as nicely on the front of a car as it does on airplanes. Plus, airplanes don't have (much for) x-winds in flight.

Yeah, I was waiting for someone to say that. If you stick it out the side of the car the air flows through it, and you also get that big chunk of drag. If you put it up front it so that it doesn't increase frontal area, it cause less drag. But it won't spin as well, so less juice for the electrical system.

Also, I would think that just the act of spinning would increase the air turbulence as it flows around the front of your car, so there could still be a net drag effect that offsets any gain in juice supplementing the electrical system.

Rats. I really wanted an excuse to put a propeller on my car.

CarloSW2

[aerohead]

While the generator itself might be very efficient I'm not sure about the turbine.Wind machines are limited to about 59 % mechanical efficiency,Not real good.
And aerodynamically,we want to limit the air which goes through the vehicle.

[fidalgoman]

Like others have said, there's no free lunch. Any time you extract work from the airstream you convert freestream air into drag. So whether by turbulance or an energy sucking pump, (turbine) work is being extracted from the ram air and creating a differential at the rear. This results in a minus energy situation known as drag. This drag is one of the reason the Sneider Cup race planes from the thirties did away with finned radiators and used smooth flat liquid filled panels along the sides and bottom of the fuselage instead. Heat transfere without as much drag. Any time you cause an acceleration (or bend airflow), you create drag.

[ShadeTreeMech]

I've figured out how he could have a "free" lunch.

Get a couple deep cycle batteries put in the car. Install a switch to turn off the alternator while driving. And charge the batteries with a windmill/ solar panel array.

Were it not for the likelihood of extreme low efficiencies of air flow to power, this could have been a good idea. I think you would have to be a commuter traveling around 75-80 average for a long time for this to have any viability.

I consider talldude a friend, so I hope he realizes sometimes this forum is a good place for inserting a dose of reality into ideas that may not work as well as hoped.

[2003protege]

Originally Posted by ShadeTreeMech

Get a couple deep cycle batteries put in the car. Install a switch to turn off the alternator while driving. And charge the batteries with a windmill/ solar panel array.

solar I agree with. But we're weighing the effiency of a belt driven alternator with the efficiency oooof...

...the transmission driven tires to the tire driven vehicle to the vehicle created airflow to the airflow created propeller to the propeller driven alternator.

as for the chain of efficiency losses, just the tires at speed have a bigger loss than the alternator belt.

[cfg83]

talldudenumber5 -

It sounds like it won't work, but I still like your question.

Someone else posted this a long time ago, but your thread made me think of it :

Tiny, Plastic Wind Turbines Suitable for City Dwellers : TreeHugger

Like many places in the world, Hong Kong does not have strong wind speeds, so wind turbines have not been widely installed there. But now engineers at the University of Hong Kong and a private renewable energy company have developed a new micro wind turbine that can generate electricity even if wind speeds are as low as two meters per second.
Lucien Gambarota, the main inventor of the technology, says the small turbines are ideal for crowded cities such as Hong Kong because they can be installed on rooftops and balconies. Their design is simple: plastic gearwheels, each about 25 centimeters in diameter, are linked to one another and turn, moved by the wind. Groups of gearwheels can be arranged in an array of shapes and sizes, ranging from about two up to thousands of square meters, depending on how much energy is needed and how much space is available.

The "how much space is available" is what caught my attention, because engine bays are usually cramped. I can imagine a scenario where it is used to make a single row of fans that are oriented to exit the air to the underside of the car :



CarloSW2

[cfg83]

talldudenumber5 -

Here's a video :

http://www.youtube.com/watch?v=5xgZPR4Y6io

CarloSW2

[talldudenumber5]

Ok ok fine I will scrap the wind idea. I just need 6 pages of no's, lol. I just want to go beyond aerodynamics. Thanks guys one of the best parts about ecomodders is the additude here . It's all constructive criticism that builds on an idea. I wonder how many other people had thought of "using the wind we drive through". Now we know. Hope to make more friends like shadetree