Wind Power from a Motorized Vehicle

It would be more efficient to use the vehicle's alternator to charge the battery directly, and to cut out the propeller step. Which is sort-of-why the propeller idea isn't done.

However, the propellor-generator was a useful device in the saving of many lives when an aircraft ran out of fuel in mid-Atlantic and had to glide to the Azores.

It would more than counter any power generated... else you'd have the possibiliy perpetual motion..
We've had this idea posted several times.
Del

How about always parking on top of a hill so that you always only drive down hill? That will surely save gas...

I think we had this discussion.

Chris

"I think we had this discussion."

Yes, we did. And this one: another discussion

Would the increased air friction (gas consumption), counter any increase in power generation?

Of course.

Efficiency may be attained if you mounted a small generator and a propeller on the outside of a static vehicle in moving air...

I realize this borders on perpetual motion which I know is a no-no. I was thinking more along the lines of a very small propeller driving a small generator to provide a trickle charge similar to that you would get from a solar panel. Placed on a big rig truck, very little drag would be added.

I believe similar devices are used on boats and airplanes. On a boat it is located underwater to indicate speed and on a plane, to do the same.

One really interesting version of this is called an Autogyro. Basically you can do what you are asking. The rotor is a net drag on the system, which is tilted to the rear. All forward motion is provided by the propeller. I believe modern versions can feather the rotor blades, but you can maybe change the rotor tilt to alter lift profile too.

Chris

Many vawt types placed at locations large trucks pass would be a net gain.

I've never seen a propeller driven speed measuring device on an airplane, though I won't say it hasn't been done. Normally, a pitot tube and static port pressure are compared and the difference displayed as airspeed. Time lag, and erroneous readings if the airplane is not flying in a straight line without pitch or yaw, will eliminate use of a propeller as a viable means of obtaining speed information. Add the need for moving parts, and it is dead.

In any case, consider: if a propeller / wind turbine is attached to a moving vehicle, there are losses in coupling the relative wind to the prop; there would be less loss by coupling to a moving wheel in case of a car or truck, or better still, to the engine itself. Power transmission between prime mover and electrical output will involve more loss through airstream and propeller than it would to use direct drive, gearing, chain, or belt drive - and perhaps even hydraulic or pneumatic drives. And the load imposed upon the engine by the added drag will further skew results in favor of more direct means. Period.

Placed on a big rig truck, very little drag would be added.

Very little drag added, and even less power produced. As soon as you claim to generate more power than the loss from the drag created, you are talking about "over unity," "free energy" and perpetual motion. If there is some need for electrical generation, it is most efficiently handled by direct drive from the prime mover.

Planes do not use propellers for speed indication. Some boats do, and the tiny propeller reduces the boat's speed potential ever so slightly.

A case in which a propeller would "make sense" (in a theoretical sense, but not in a practical one) is if you used it as an air brake. When you wanted to slow down you'd deploy the retractable propeller/generator unit to slow down, and charge batteries. When acceleration was subsequently required, you'd power the prop from the batteries. It would be a crude, complicated, and inefficient form or regenerative braking.

Ron, TANSTAAFL and the third law of thermodynamics (they are essentially the same.) always applies, you never get back as much energy as you put in.

Also, after the alternator has recharged the energy used to start the vehicle, for all intents and purposes the car is running on the alternator. The battery is essentially a parasitic load at that point.

I think you've stumbled onto something most have missed so far.

You're description is not of replacing or generating extra-power for the vehicle. It is a given the vehicle in motion will use energy.

What hasn't been observed is the energy which maybe reaped without interfering in the normal use of said vehicle. A freight hauler for instance could provide a means to collect, store then discharge energy to a storage unit periodically.

Is this the thought keeping you awake?

I didn't post the message but I have been staying awake at night figuring this one out. I get the whole third law jargon, but thats an easy way to say it won't work, my theory(which has yet to be said in this thread) is to decrease the aerodynamic drag and create more of an airfoil/airstream to increase up to about 100 mph winds. Supercapacitors could drive a hybrid truck and excess could be dissappated through a discharge point along the highway. I have a few other ideas that make it seem like a viable idea to take to a higher level, but for now I'm going to see what info is out there on drag coefficient on trailers. Truck redesign will take too long and be way too costly for my "testing". I have no engineering background, but I am stubborn enough to keep going till I prove it can't be done. I won't check this site and I'm not a member, please email me at thejunkdrawer09@yahoo.com if I'm missing a piece of the puzzle that will save me some trouble.

For ANY system,

Energy In is what you pay for.

Energy Out is what you want. (motion, electricity, whatever)

Energy In will always be greater than Energy Out, because the universe takes its cut. (friction, entropy, etc) (It's the law)

Why would you expect to get more out (motion + electricity) than you paid for.

Why would you try to capture energy from moving vehicles with energy you paid for, when you could simply convert the energy directly (from fuel presumably) in a much more efficient method. (generator)

If you try to give energy from a moving vehicle at a 'discharge point', you will have more losses than you would have in a simple generator which has optimized efficiency not possible with the moving vehicle.

In short, it might sound uber cool to do it, but the waste would make it uber doobie. If you analyze this in 'black box' type of thinking, you should be able to see the problem.

Chris

I have the same problem with sleep right now. I read all the replies from the experts but am convinced you are onto something big. Big rigs are aerodynamically inefficient in my mind, lets figure a way to channel some of the airflow to either decrease drag or increase airflow, harness that energy, and send it back into grid. I'm thinking along the lines of capacitators, and of course, a more efficient method of moving the vehicle. Got my head stuck on biodiesel engine with active hydrogen generator, regen braking, more use of supercapacitors, Wind Tunnel Technology, and composites/structural PV cells in the buildup. My simple thought is that everything that moves can/should be harnessed for energy. Trucks and trains move the world for now, lets integrate them and keep on this rush to be more energy independent. Wow, just caught myself on the soapbox, have a great day.

This sounds perfect, except for the fact that you didn't mention nanotech. The key to making perpetual motion schemes work is nanotech.

My simple thought is that everything that moves can/should be harnessed for energy.

I agree. Every truck should be forced to tow a large trailer with a wheel-driven generator. These would be about twice as efficient as a generator driven by a wind turbine, although not as efficient as a generator driven directly from the engine (which would avoid the transmission losses and the trailer tire losses). These trailers should be made large enough to consume 100 hp (and would produce electrical power at a rate of about 75 hp, for a net loss of only 25 hp.) They would improve highway safety by slowing trucks down. Truck fuel efficiency would drop substantially. We'd be throwing away fuel, but who cares about that? At least we'd be helping to support Saudi Arabia, instead of using our own natural gas in power plants (that are substantially more efficient than truck engines.)

The brilliance of the trailer is that people don't think about all the energy in the ground rushing by the truck. They do, apparently, think about all the energy in the wind rushing by the truck, even though the ground and the air rush past the truck at the same speed.

People walking on city streets could also be forced to tow trailers behind them to generate electricity from their walking. If that doesn't improve overall fitness enough, then we'd make them carry windmills, so that they have to work twice as hard to generate their daily quota of electricity. Those smarty pants bikers with their fancy lightweight bikes could be made to tow trailers too. See how fast they go up hills, then!

This scheme is equivalent to selling a load of firewood for the cash, and then burning the cash for heat, with the theoretical exception that someone might incredibly overpay you in a nearly worthless currency, and you'd get as much energy from burning it as you would have from burning the wood directly. But then, BOTH of you would have put effort into an absurd endeavor; merely transporting the loads of wood and hyper-inflated banknotes will waste those hypothetical gains. It's a lose-lose situation.