Fully Electric car with wind generators

[A.T.]

Ya know if the wind was strong enough on the given day a car powered by wind power could work... NOT.

Why NOT?

 

[OmCheeto]

You don't seemed to have grasped the fact that taking erergy from the air you're traveling through merely increases the energy required to drive you forward. No free lunch.

Not only that, but vehicles optimized to utilize this effect(for speed) have to reach significant speeds to take advantage of it. Not to mention they are incredibly light for their footprint.

http://boatdesign.net/articles/tunnel-hull-design/index.htm

50 mph yields 110 lbf of lift
100 mph yields 340 lbf of lift

This is with a 2 degree angle of attack which yields a lift coefficient of about 0.2
Increasing the angle to about 9 degrees(optimizing for lift) yields a unity lift factor which gives the following:

50 mph yields 550 lbf of lift
100 mph yields 1700 lbf of lift

Since most land vehicles achieve maximum fuel efficiencies between http://www.speedvsmpg.com/wp-content/uploads/2008/07/speedvsmpg.jpg" , due to a combination of aerodynamic drag and ICE characteristics, it is my opinion that it's pointless to try and reduce the rolling resistance of the vehicle through lift, since power required to push a vehicle is related to the cube of the wind speed and only proportionally to that of the rolling speed.

It would be fun to run the numbers, but I've a hole in my roof and have to go patch it.

Anyone with spare time on their hands can try this spot:

http://ecomodder.com/forum/tool-aero-rolling-resistance.php

Plug in the numbers for your vehicle and replace the "Rolling HP" with a value corresponding to the lift generated at different speeds. Also change your frontal area to correspond with the duct-work required to port said winds underneath the vehicle. Get back to us with the speed required to make your vehicle more efficient.

hmmm... You'll need a couple more equations:
Coefficient of Lift = 2 * pi * a ('a' being the angle of attack)(only good between 0 and 15 degrees)
Lift = L = 1/2 rho v^2 Sref Cl (rho = 1.2, Sref is your lifting area, and Cl is your Coefficient of lift)

 

[sophiecentaur]

I'm not sure what to say.
Anything set in motion offers a potential of "energy return".

Flying in ground effect involves (in general) fast speed and extensive flat and open areas.
Driving in ground effect will involve much slower speed and contact with the ground, for reasons of operator control.

Any work performed with any compression of air will produce a change of temperature. Making use of pressure changes around a moving object can produce big returns in how much overall energy is needed to keep the object in motion.

You write as if you think there's some magical extra energy available. The best you can do , when you are running steadily, is to minimise your losses. Putting energy into producing a change in temperature (from which you seem to think you can get some useful energy) will involve more energy input than you get out (pretty much the most fundamental law you can think of).
Regeneration of energy has nothing to do with what you are talking about - it's about reducing your overall losses (a bit) when you need to slow down or stop. You minimise the wasted Kinetic Energy that you would have wasted, that's all. What are "big returns", in your context?

 

[OmCheeto]

You write as if you think there's some magical extra energy available. The best you can do , when you are running steadily, is to minimize your losses.

Exactly!

But like Ron, you have to change all parameters of an experiment, regardless of whether or not you think they will come close improving the system.

I thumbed through an insanely long 200 page pdf yesterday describing improvements in the aerodynamics of light trucks. (I own a light truck, so I was mildly interested.)

The last thing in the world I would have believed was that a cowl air dam across the front of the vehicle would contribute the greatest improvement of the 250 variations to the aerodynamics of the vehicle.(I actually still don't believe it)

http://www.tercelreference.com/downloads/gettrdoc.pdf (8 megabytes!)

They of course tried ducting, to no avail...

 

[sophiecentaur]

I remember reading Colin Chapman (Lotus designer) in his classic book of the 60s. He wrote that you cannot approach aerodynamics intuitively. 'Go faster' ideas usually don't.

It seems to be mostly a matter of reducing / shedding vortices rather than have them hanging around your back end. Those turned-up wing tips on all the big jets have more than paid for themselves.

 

[RonL]

Exactly!

But like Ron, you have to change all parameters of an experiment, regardless of whether or not you think they will come close improving the system.

I thumbed through an insanely long 200 page pdf yesterday describing improvements in the aerodynamics of light trucks. (I own a light truck, so I was mildly interested.)

The last thing in the world I would have believed was that a cowl air dam across the front of the vehicle would contribute the greatest improvement of the 250 variations to the aerodynamics of the vehicle.(I actually still don't believe it)

http://www.tercelreference.com/downloads/gettrdoc.pdf (8 megabytes!)

They of course tried ducting, to no avail...

You have to start the thought process as though everything is possible, then when something will not or cannot work, try to see if something will change the outcome.
For almost any application of energy recovery on ground based vehicles, they will involve suction and discharge conditions that make the process impractical.

One example for me to think of, is my loader bucket has a bottom area of around 60 sq. ft. If it is positioned where the front is about 24" up and the back is about 6" above the ground. A movement of only 1 or 2 MPH will cause an airflow to curl up behind the bucket, with such force as to lift massive amounts of dust, grass and weed fragments to the point of having to stop or raise the bucket higher. There is power in volume!

I remember reading Colin Chapman (Lotus designer) in his classic book of the 60s. He wrote that you cannot approach aerodynamics intuitively. 'Go faster' ideas usually don't.

It seems to be mostly a matter of reducing / shedding vortices rather than have them hanging around your back end. Those turned-up wing tips on all the big jets have more than paid for themselves.

Go faster ideas, is the heart of our problems, just my thinking.

The vortices are the product of the energy that has already been spent, the control of how smoothly these vortices are recombined with the hole just punched in the air is the key to "energy recovery".

Reducing friction drag on the skin of the vehicle will be the biggest area of inovation. We might start with something as non-se*y as a bus and work down.
Start with some amount of suction in the frontal area (the more the better) and move a very large volume of low pressure air flow into a hollow double wall shell, the inner wall is solid and the outer wall is perforated with tiny holes that allow an air ejection (low pressure) much the same as an air hockey table, this air will help to reduce the grip of the air that has been pushed aside.
Might sound crazy but ideas are the start of any type research, that makes use of old principles being applied in new ways.

 

[OmCheeto]

Reducing friction drag on the skin of the vehicle will be the biggest area of innovation. We might start with something as non-se*y as a bus and work down.

You're not an ex-NASA scientist are you?

from page 28 of the http://www.tercelreference.com/downloads/gettrdoc.pdf" I mentioned yesterday:

The test vehicle that NASA used is shown below:

Figure 7. NASA Dryden Research Vehicle – Box Shape​

NASA’s interest was primarily directed at improving semi trailer
performance but these results are even more appropriate for light trucks. They
found that a practical drag coefficient (Cd) of .25 was possible when a rounded
front was implemented along with a truncated “boattail” shaped back.

I was all like; "That's a NASA designed vehicle?" on Sunday. But seeing your bus comment today made me realize that science isn't always pretty, nor as sophie.c pointed out, intuitively logical.

 

[RonL]

You're not an ex-NASA scientist are you?

from page 28 of the http://www.tercelreference.com/downloads/gettrdoc.pdf" I mentioned yesterday:


I was all like; "That's a NASA designed vehicle?" on Sunday. But seeing your bus comment today made me realize that science isn't always pretty, nor as sophie.c pointed out, intuitively logical.

LOL, Om I thought you had read more of my posts, I can't even get much attention in the overunity crowds.

I didn't have time to go further when I made the post, but my thinking was to have the front like they said, but with suction intake in the center, then round the back into a taper circle and have two counter rotating, 7' diameter Tesla style turbines exhausting in the center.

Have you ever driven a few car links behind a trailer rig and felt the rough air gusts that are shed? If you move up too close, you ride in the draft area and it is pretty smooth.

No I did not know of their test design, but it makes me feel better about my thinking.
Sooo much room for design work.

Ron

 

[RonL]

Hey Om,
I just downloaded the pdf you posted, thanks!

I once made mention of the perforated skin surface, for reduction of surface drag, and the aviation crowds went silent, I just seem to have that affect on people.

Something you might be interested in, if you don't already know of these. Might be the seeds of a lot of my thoughts.

http://books.google.com/books/serial/ISSN:01617370?rview=1&source=gbs_navlinks_s

http://books.google.com/books/serial/ISSN:00324558?rview=1&rview=1&source=gbs_navlinks_s

 

[tropicalvikin]

Detractors of the idea seem to live in a flat world.
Where I live we have thousands on non flat roads, you can have vanes which close the ducts when going flat or uphill and open them downhill.
Downhill. You definitely can generate energy while making brake pads last longer.

I had a Pick Up truck, with a high (much taller that the cabin) canvas cover which was used on rainy days, the sail effect was amazing, and helped braking on downhills (it kept top speed very restricted also).

 

[sophiecentaur]

So, what are you saying, apart from the fact that regen braking is a good idea? Is this new? All the other stuff about flaps and stuff is either irrellevant or implies a bit if P.M.. (or yachting)