Would a wind turbine on a moving car generate energy efficiently?

[RonL]

What changes need to take place? First look at what happens with no attempt at energy generation or recovery.

Put the car in motion at say 60 MPH, electric drive system and plenty of battery supply for a short time. If 50 HP is being expended to maintain speed, the generated apparent wind will turn the fan we have been talking about at less than the wind speed, but if a second motor is engaged to turn the fan, only a small amount of power will need to be added to bring the fan to a neutral speed in relation to the apparent wind, (maybe 5 HP) if a little more power is added (5 HP) the fan produces a very small suction in front and a very small thrust in rear, somewhere in there will be a zero point where the two motors are in balance with respect to total power needed, at that point any increase of power to the small motor will reflect an equal drop in the larger motor.
No energy recovered = a total negative expense.

Now to extract any energy, which is the topic at hand, I have suggested a fan design that serves in multiple capacities, all in some way to contribute a thermal transfer from the heat in the air that is being pulled through and thrust out the back.
Without trying to describe the mechanics within the design, I will list some things that can be used in the conversion process. (some may not be needed)

Somewhere around 2000 BTU/minute will be needed, maybe less.
Everyone should know that heat can be extracted from air and that heat can be converted to useful work.

Work to put the vehicle in motion must be expended first and when in motion things can start to happen. Thermal conversion and energy generation inside the fan body.
First thing to consider is that no resistance is created in the fans function, if the mechanics inside the fan structure are not engaged and even the heat engine functions carried on inside the fan design will not have any affect on the fan as it turns.

A list of things inside the fan design, these can be single units or multiple interacting systems.
A. Stirling Cycle
B. Vapor Compression
C. Gas Cycle (compressed air)
D. Vapor Absorption ?

E. Vane Motors
F. Generator(s)
G. Electric Motor(s)

energy transfer
H. Slip Rings/Brushes
I. Magnetics
J. Air Pressure
K. A variety of motion control things.

With those things in mind, I say yes we can transform heat into work in an efficient manner.
Basically we are doing the same as driving a plane with no wings.
The design questions will all revolve around how many BTU can be extracted from what volume of air flow needed to pull and push the vehicle at an acceptable speed.

Using Heat engine tech, compressed air and very common energy transfer equipment, there is lots of room to exchange normally wasted heat from one unit and use it to enhance another.
Just to be clear, a main power source turns the fan and energy generated inside the fan is transferred out to assist or replenish the energy used to turn the fan.

I have tried to avoid explaining things in detail, just hope there is enough logic here to trigger some different kinds of thought in regard to energy waste.

Ron

 

[RonL]

For Russ and anyone that likes to crunch numbers, I hope this is a close and basic enough set of values to show potential of some energy recovery.

1. Vehicle weight between 4,000 and 5,000 pounds.

2. 4 wheels, traction drive for 2 or 4.

3. Main power, 2 or 3, 20 HP DC motors and a possible AC combination.

4. Battery storage ?, will depend on several things.

5. Heat engine design will involve multiple fans, (5 > 7)

6. Heat engine design will have axle tube of 12" - 18" diameter and be about 15' in length.

7. Front intake area ? I have chosen 19.625 sq ft as a start for showing airflow volume.

8. Starting power applied to both traction drive and fan system.

9. As speed increases, heat engine functions start to develop.

10. Based on vehicle motion, fan is balanced or slightly positive to eliminate any negative frontal resistance.

11. Power to sustain forward motion is kept close to equal between motors serving as drivetrain or fan drive.

12 Volume of airflow through fan system at 30 mph and 60 mph,
(a.) 30 miles per hour = 51,810 cubic feet per minute.
(b.) 60 miles per hour = 103,620 cubic feet per minute.

13. To find a 2,000 or close BTU per minute transfer rate, seems to me not to be needing a very large thermal Delta, especially on really warm days.

14. A 48" fan system might need to be enlarged a little, depending on axle diameter.


Stuffing all mechanical and heat exchange parts inside the axle tube will be a bit complicated and will result in a heavy axle tube, but is within reason.

Compressed air, electric motors and generators along with heat exchange properties taking place inside the axle tube and through the fan blades and fan rings, should provide an easy transfer of BTU from such a very large mass air flow.

I'm sure this leaves a lot to question, Russ I hope this is close to your suggested form of presentation. In trying to describe the inner working of the axle tube, I wound up with almost 10 pages of notes and descriptive wording.

There are lots of reasons that a fan driven car will not work for general transportation, but having this endless quest for better fuel mileage and cheap power needs to end. The use of Hydrogen for transportation, I think is as impractical as trying to stop global warming.

Hopeing this is a better presentation.

Ron

 

[RonL]

OK, after 4 days and 400+ views...no comments or questions, so here is my simple math, maybe someone will see the error of my thinking in regard to extracting heat from the air.

A steady speed of 60 MPH
A fan that is in balance with air flow in relation to speed.
A frontal area intake of 19.625 square feet
A mass air flow of 103,000 cubic feet per minute (not exact, but close)
Weight of a cubic foot of dry air @ 70 degrees F .07495
BTU's to raise temperature of 1 pound of air 1 degree F .240
BTU's per minute to equal 1 Horsepower...42.4

Using these numbers to raise temperature shows 43.697 HP per 1 degree

I believe the reverse would apply, dumping 43.697 HP into the heat engine.

A delta of 30 degrees would put temperature of the mass air flow at 100 degrees F
The new weight per cubic foot is .07094, the new HP figure is 41.359
Adding the two HP figures and dividing by two gives an average HP for each degree of change 42.528, multiple by 30 for a total of 1275.845 HP in a 30 degree Delta.

As I stated before, it is impossible to absorb more power than is being used, unless there is some sort of storage system in the design and then ONLY until it is full, after which the absorption will never exceed a dispersement (which is keeping the vehicle in motion)

If only 75 HP is needed then the Delta that delivers that other 1200 HP CANNOT come into play. The same as a Gasoline engine with 500 HP cannot apply more than the same 75 HP at a steady speed.

So unless someone explains why a heat pump cannot feed a heat engine and an air compressor cannot be inside said heat engine and produce two pressure values based on compression and heat of compression, Then pressure converted to work (mechanical or electric or both) satisfying R Clausius Heat/Work statement, then I will need a stronger understanding of the first two laws of Thermodynamics.

Heat being absorbed from the mass air flow, Then being converted to work, which is being directed into sustaining motion, which is producing the air flow...I can't see the violation in any of the three things above.

I think I have shown the potential of the heat in the air and to satisfy the 2nd law, ONLY the heat needed to overcome the resistance of motion can be extracted.
This is different from the electric motor driving a generator, then the generator giving the motor the power it needs...because electricity can put out heat, but not absorb heat and cannot be compressed or expanded.

So back to the question of the thread, I say yes, and this is the thinking that goes on in my head, someone speak up. My simple math and logic might have overlooked that key thing...which is?

Thanks
Ron

 

[Andrew Mason]

You are trying to create a perpetual motion machine of the second kind. You cannot run a steamship across the ocean by extracting heat from the ocean using a heat pump and then using the heat from the heat pump to run the steam engines. This would violate the second law of thermodynamics, but would not violate the law of conservation of energy.

The most amount of work you could get out of such a machine would be the amount of work done by the heat pump (in your case, that would be using a Carnot heat pump running off the car engine and Carnot heat engine supplementing the car engine's output). In reality, you could not achieve Carnot efficiency in either, so you would be wasting energy.

AM

 

[RonL]

You are trying to create a perpetual motion machine of the second kind. You cannot run a steamship across the ocean by extracting heat from the ocean using a heat pump and then using the heat from the heat pump to run the steam engines. This would violate the second law of thermodynamics, but would not violate the law of conservation of energy.

The most amount of work you could get out of such a machine would be the amount of work done by the heat pump (in your case, that would be using a Carnot heat pump running off the car engine and Carnot heat engine supplementing the car engine's output). In reality, you could not achieve Carnot efficiency in either, so you would be wasting energy.

AM

Thanks AM,
This is the same as Russ stated, when he said I need to understand the Carnot Cycle, so that will be the only mission for me, and as Halls of Ivy said to someone else in another thread this weekend "understanding every detail and word of an established law or definition" that might not be exact but I think it is close, did not go unnoticed by me.

I'm really having trouble understanding why, if normal losses are being recovered and recirculated within the heat conversion process inside the system, this represents an internal energy that keeps momentum strong and cycles moving so that only what is added can be sent out as work. Maybe that doesn't make sense.

My mind See's the 1st and 2nd law as saying, it's as impossible to sustain waste as it is to have more than 100% in a system.

Anyway I have a lot in front of me and a lot of misunderstandings to push to the side, if in fact my thinking is completely wrong.
Thanks for the answer.

Ron

PS Looking back at that statement about the ship, in essense the steam engine would be inside my heat engine (or heat pump) I think that is what makes the difference ??

 

[RonL]

Last post, I promise.

I guess I never really defined the T high and T low of the system and these can be any value based on design.
Inside the heat engine, the range might be 1200 F degrees high and -50 F low, with any number of exchange points, then if outside air is 90 F intake and 85 F discharge should equal, or be close to the needs of energy out.
Energy volume inside can be quite large and maintain a large amount of momentum.

I'll go to wiki and any books I have, and not say another word until I have this straight in my mind.

Thanks
Ron

 

[Andrew Mason]

I'm really having trouble understanding why, if normal losses are being recovered and recirculated within the heat conversion process inside the system, this represents an internal energy that keeps momentum strong and cycles moving so that only what is added can be sent out as work. Maybe that doesn't make sense.

You cannot convert all the heat energy into work. The work done by the wind on the windmill (which is really the work done by the car engine on the windmill) may result in cooling of the air (I'm not sure about that). But if it did, the amount of work you would be able to extract from a heat engine operating between the two temperatures cannot possibly be more than the amount of work done by the engine in creating the temperature difference. This is the second law of thermodynamics.

My mind See's the 1st and 2nd law as saying, it's as impossible to sustain waste as it is to have more than 100% in a system.

The first law is simply the conservation of energy. The second law is more subtle. It says that work is required to make heat flow from a colder to a hotter reservoir. The second law says that the amount of work you can get out of a heat engine that uses a heat flow between a hot and cold reservoir cannot exceed the amount of work required to reverse the heat flow from the cold to the hot reservoir.

AM

 

[RonL]

You cannot convert all the heat energy into work. The work done by the wind on the windmill (which is really the work done by the car engine on the windmill) may result in cooling of the air (I'm not sure about that). But if it did, the amount of work you would be able to extract from a heat engine operating between the two temperatures cannot possibly be more than the amount of work done by the engine in creating the temperature difference. This is the second law of thermodynamics.


The first law is simply the conservation of energy. The second law is more subtle. It says that work is required to make heat flow from a colder to a hotter reservoir. The second law says that the amount of work you can get out of a heat engine that uses a heat flow between a hot and cold reservoir cannot exceed the amount of work required to reverse the heat flow from the cold to the hot reservoir.

AM

Thanks AM,
I certainly don't want to sound too resistant, but would like to present three thoughts.

1. This is not working between two reservoirs, just one.
2. The fan, as stated further back in the thread, is both the thrust provider and at the same time the heat absorber.
3. The entire system is in motion as all this takes place, the net energy balances at 0, no need for a positive supply.

If you take the wheels off and bolt it to a foundation, it becomes no more than a pretty good heat pump or refrigerator, depending on what is desired.
I think what keeps me confused is the one reservoir I see and the two reservoirs mentioned in all thermodynamics textbooks.
If I have two reservoirs in what I have suggested, they exist inside the heat engine and are well insulated from each other, this is what I have to try and sort out, so far I have had little success as my level of education is pretty short. I do feel confident in my mechanical aptitude, just too many lose ends that I have a hard time connecting properly.

Thanks AM and anyone else that has tried to understand my thoughts.
Now back to some books.

Ron

 

[RonL]

Thanks AM,
I certainly don't want to sound too resistant, but would like to present three thoughts.

1. This is not working between two reservoirs, just one.
2. The fan, as stated further back in the thread, is both the thrust provider and at the same time the heat absorber.
3. The entire system is in motion as all this takes place, the net energy balances at 0, no need for a positive supply.

If you take the wheels off and bolt it to a foundation, it becomes no more than a pretty good heat pump or refrigerator, depending on what is desired.
I think what keeps me confused is the one reservoir I see and the two reservoirs mentioned in all thermodynamics textbooks.
If I have two reservoirs in what I have suggested, they exist inside the heat engine and are well insulated from each other, this is what I have to try and sort out, so far I have had little success as my level of education is pretty short. I do feel confident in my mechanical aptitude, just too many lose ends that I have a hard time connecting properly.

Thanks AM and anyone else that has tried to understand my thoughts.
Now back to some books.

Ron

This might be what I need to study and find the way to say what I have been trying to imply.

http://en.wikipedia.org/wiki/Fluctuation_theorem

Going down to dissipation function, I find the term "non equilibrium" to represent the state of a machine in motion, that for a period of time to operate in a positive energy mode.
Poorly worded, I have some more study time in the near future, but for the moment some that are more advanced in Thermodynamics, might throw out some insights.

Later
Ron

 

[OmCheeto]

This might be what I need to study and find the way to say what I have been trying to imply.

http://en.wikipedia.org/wiki/Fluctuation_theorem

Going down to dissipation function, I find the term "non equilibrium" to represent the state of a machine in motion, that for a period of time to operate in a positive energy mode.
Poorly worded, I have some more study time in the near future, but for the moment some that are more advanced in Thermodynamics, might throw out some insights.

Later
Ron

Well, I must admit that I do not fully understand the Fluctuation Theorem, but I don't think I'll further my studies of the subject, as you cannot utilize it for anything on the scales we are talking about.

In the article referenced by the wiki entry, the FT is only valid at the nano-scale. I believe I once heard something about all of the atoms in a pot of water having a mathematically finite possibility of all of the atoms moving in the same direction, hence having the water jump out of the pot. Unfortunately, the probability is so low that you would have to wait for a bazillion (that's the age of the universe times a gazillion) years.

http://www.newscientist.com/article/dn2572"
09:21 19 July 2002 by Matthew Chalmers

"In a typical room, for example, the air molecules are most likely to be distributed evenly, which is the overall result of their individual random motion", says theoretical physicist Andrew Davies of Glasgow University. "But because of this randomness there is always a probability that suddenly all the air will bunch up in one corner." Thankfully this probability is so small it never happens on human timescales.

 

[RonL]

Well, I must admit that I do not fully understand the Fluctuation Theorem, but I don't think I'll further my studies of the subject, as you cannot utilize it for anything on the scales we are talking about.

In the article referenced by the wiki entry, the FT is only valid at the nano-scale. I believe I once heard something about all of the atoms in a pot of water having a mathematically finite possibility of all of the atoms moving in the same direction, hence having the water jump out of the pot. Unfortunately, the probability is so low that you would have to wait for a bazillion (that's the age of the universe times a gazillion) years.

Thanks OmCheeto, for the response.

I'm still a long way from making my defense sound intelligent, but think there has been an improvement of my understanding during this last couple of weeks.

I'm sorry I made one post yesterday, but I did, so it stands.

What I'm finding so far does not make me feel less sure of my thoughts, I do put full faith in the first law (no creation and no destruction of energy) and the second law as I have always believed, only limits exceeding 100%, so if the general accepted rule is that in all cases extra energy has to be added to any process, then maybe that limit needs to be lowered a little bit (98% ?)

I did find something in a handbook of physics, recently, that makes mention of a fourth phase in equilibrium with a first phase. I'm not quite sure of how to visualize what is being said, as only a phase diagram showing a triple-point of some component has come to my efforts of study.
I'm trying to find if it is referring to a plasma condition, or a vacuum so hard as to bypass the sublimation of ice, and send it straight to a vapor phase ?

I'm out of time for now, but will make a few quick checks during the rest of the day.

Later
Ron

 

[OmCheeto]

Thanks OmCheeto, for the response.

I'm still a long way from making my defense sound intelligent, but think there has been an improvement of my understanding during this last couple of weeks.

I'm sorry I made one post yesterday, but I did, so it stands.

What I'm finding so far does not make me feel less sure of my thoughts, I do put full faith in the first law (no creation and no destruction of energy) and the second law as I have always believed, only limits exceeding 100%, so if the general accepted rule is that in all cases extra energy has to be added to any process, then maybe that limit needs to be lowered a little bit (98% ?)

I did find something in a handbook of physics, recently, that makes mention of a fourth phase in equilibrium with a first phase. I'm not quite sure of how to visualize what is being said, as only a phase diagram showing a triple-point of some component has come to my efforts of study.
I'm trying to find if it is referring to a plasma condition, or a vacuum so hard as to bypass the sublimation of ice, and send it straight to a vapor phase ?

I'm out of time for now, but will make a few quick checks during the rest of the day.

Later
Ron

Ron, I'm trying hard not use Russ's phrase. Actually, I can't remember what exactly it is. All that comes to mind is spaghetti physics. Pulling all manner of ideas from every avenue of the physics community into a tangled web of incomprehensibility.

I would say more, but the river is calling.

------------------------

All work and no play makes OmCheeto a dull boy.

 

[russ_watters]

1. This is not working between two reservoirs, just one.

As already explained, that's an explicit violation of the second law of thermodynamics. Every heat engine and heat pump has two reservoirs.

Ron, I'm trying hard not use Russ's phrase. Actually, I can't remember what exactly it is. All that comes to mind is spaghetti physics. Pulling all manner of ideas from every avenue of the physics community into a tangled web of incomprehensibility.

You mean "word salad"? Unfortunately, I have to agree. Ron, you're apparently operating on an incorrect assumption/understanding about the 2nd law of thermodynamics, which is driving your efforts here. We've had trouble figuring that out because unfortunately, you have not been able to convey what you are trying to do. If you can't come up with a simple description in the spirit of my request a few posts back, perhaps a sketch would work. If you can come up with something more coherent (a sketch or description), please feel free to post it in the engineering forums (probably mechanical), but for now, there really isn't any coherent content in this thread and thus no reason to keep it open.

Locked.

Note:
The classic thought experiment involving the second law of thermodynamics is a perfectly insulated box, from which mechanical or electrical energy is extracted, causing whatever is inside to get cooler. One heat reservoir + decreasing entropy + work out = violation of 2nd law.