No ****, Sherlock: Air Powered Cars are Ineffecient
November 21st, 2009
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Of course, this was covered not too long ago on this site, but it seems that someone else has woken up to the realization that compressed air, is a really horrible vehicle fuel.
Berkeley Engineers Have Some Bad News About Air Cars
“We’ve argued before over compressed air vehicles, a.k.a. air cars. Air cars are an enchanting idea, providing mobility with zero fuel consumption or environmental impacts. The NYTimes’ Green Inc. blog reports that the reality is less rosy. New research from UC Berkeley and ICF International puts a period at the end of the discussion, showing that compressed air is a very poor fuel, storing less than 1% of the energy in gasoline; air cars won’t get you far, with a range of just 29 miles in typical city driving; and despite appearing green the vehicles are worse for the environment, with twice the carbon footprint as gasoline vehicles, from producing the electricity used to compress the air. Given these barriers, manufacturer claims should definitely be taken with a grain of salt.”
The Slashdot Article links to a story that appeared in the New York Times “Green Inc” which states:
“It sounds ideal, like we could be free from the constraints of petroleum dependence,” said Andrew Papson, a transportation engineer and associate at the consulting firm ICF International.
But as much as the idea is attractive, Mr. Papson is skeptical about air cars. He finished graduate studies at the University of California, Berkeley, last year and was part of a team at the school that published a paper this week that was critical of air-car claims.
I really hope that this didn’t actually take a whole team of graduate students and faculty members at UC Berkely to figure out. In fact, if it took any of them more than about 30 seconds to come to the conclusion that air is just not a good way of powering a car, then we’re in trouble. The report appeared in Environmental Research Letters.
While I’m glad someone has woken up to this, I’m still floored that this even took a formal report to get any recondition. I just hope that the creation of the report didn’t actually cost anything beyond the price of a few pieces of paper.
If there is anything that should be learned from this, it is that those who actually understand these things and have the clout and credibility to shoot down this kind of BS really should not drag their feet on it. It would have been nice if this whole concept got a bit more healthy skepticism and a good dose of reality when it first started showing up in the media a few years ago. Since then, this idiocy has been allowed to fester because those who know better have either failed to get any publicity or haven’t even tried.
Needless to say, there will still be some who cling to their faith in pneumatic cars as a way to save the world from rising fuel costs and emissions.
This entry was posted on Saturday, November 21st, 2009 at 5:13 pm and is filed under Bad Science, Enviornment, Good Science, Just LAME, Misc, Not Even Wrong, Obfuscation. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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July 12th, 2010 at 3:13 pm
Sorry for my english being so much poorer than my thermodynamic, i don’t understand you very well.
Can you repeat please ?
How can a thing like “compressed air” being a “method” ?
Your posts are so much fun DV82XL, this is incredible : are you doing that on purpose, only to help me improve my english ? Thanks for your kindness.
I must not forget that i was there to try to understand :
- Where is “horrible inefficiency” ?
- And how do you obtain the result that “an air powered car only has a range of 30 miles” ?
Quote Comment
July 17th, 2010 at 4:09 pm
Hello,
As it seems that nobody has consistent explanation about where is any “horrible inefficiency”, i made some graphic with theoritical numbers. Please tell me if any error or question.
I am not sure if an image may be visible here.
[img]http://www.econologie.info/share/partager2/1279400426NcrHr9.gif[/img]
You may see that for a 4,8KWh energy in tank, the engine would absorb 6,2KWh of thermal energy to achieve full thermodynamic efficiency to output 11KWh : thermal design is mandatory.
Quote Comment
July 17th, 2010 at 5:28 pm
brnd said:
I’m not going to explain it any more basically than this.
the method of energy storage being the compression of air from the atmosphere into an enclosed vessel as a means of storing energy which is later to be recovered by means of releasing the pressurized air from the vessel and passing the air through a pneumatic engine – reciprocating, turbine or otherwise and thereby providing power while recovering a portion of the energy used to drive the compressor.
If you cannot understand that then I can’t help you.
brnd said:
Okay. The full-cycle efficiency (the amount of useful energy you get out as a percent of what you put in) for various forms of energy are as follows. These are approximate, as the actual amount depends on numerous application-specific subtleties. However, these numbers are reliable +/- about 5%
Lead Acid Battery (fully charged by direct current and discharged to design cycle within a week of charge): 90%
Lead Acid Battery (fully charged by direct current and discharged to design cycle within a two to three months of charge): 80%
Lithium Ion battery (industry standard lithium ion polymer with cobalt alloy electrodes, discharged within a few days to a week): 80-90%
Sodium-Sulfur Battery (industry standard, BASE, passive thermal management, discharged within 48 hours of charge): 88-92%
Regenerative hydrogen cycle (regenerative fuel cell / high pressure electrolysis with Proton exchange membrane): 18-30%
Diesel Engine (turbo charged, high compression large block engine): 25-38%
compressed air cycle: 3% – 15%
I’ll add that I am skeptical of claims of getting consistent 15% cycle return. Perhaps it is possible, but that seems like a lot. Even by the best estimates, it is considerably worse than almost all other methods of storing energy.
Yes, I am aware some say they can get 35% or even 75%. That’s based on the ridiculous presumption that the heat generated by compression can always be used to 100% capacity for some other purpose of equal value. That’s ridiculous. Cooling compressors almost never generates useful heat. The operating temperatures are too low to make thermal engines practical. There are also claims that the whole cycle is loss-less because the gas can be put through some kind of perfect heat-exchanger – which, of course, does not exist and even if a heat exchanger could completely regain all of the temperature, there’s still the fact that it impedes the flow of the air and on top of that, the difference in temperature turns out to be a loss of energy no matter how you slice it.
brnd said:
ONCE AGAIN:
This is the approximate maximum distance that any of the best prototypes can get.
AND I will restate, the following:
You can’t make them much lighter, because they’re already stripped down to being just a person sitting on some big air tanks with nothing but a small fiberglass shell on them.
You can’t make the tanks much bigger because they already occupy most of the vehicles volume
YES, I have seen companies claim that they can build a car with a range of 100+ miles. Nobody has yet done this or even described how they plan on doing so.
The only “compressed air vehicles” ever demonstrated to exceed a range of a dozen to about thirty miles are ones that used a combined system with a “pre-heater” or some other mechanism powered by burning fuel. This being the case, they are not actually getting all of their energy (or even most of it) from the compressed air!
Let me restate the 30 mile point: A vehicle powered by compressed air and of a size compatible with city driving (in other words, not a tanker truck) and of a great enough capacity to carry human beings will necessarily be limited to extremely short ranges, generally being under 20 miles, but in some circumstances, topping out at about 30 miles. While this is an approximation, it is based on the inherent limits.
Quote Comment
July 17th, 2010 at 5:41 pm
brnd said:
We have done nothing but provide you with consistent explanations of why compressed air energy storage is inefficient. It is not our fault that you are just to stupid to understand them.
Quote Comment
July 26th, 2010 at 8:24 pm
Your point makes sense regarding air power now that I look at it and sure even if it did work, it is only how you transfer it because you still need something to drive the compressing of it.
What do you think of water powered cars? I have been told it is not possible. Water sure does not burn and I do not understand how it could be a fuel by itself. It can be broken down into hydrogen and oxygen and that will work to power a car.
I am told that this is possible but you again need to power the breakdown of the water and the car could not keep a device to breakdpown the water on it and just run on water and break it down as it goes to manufacture its fuel there as needed. However, if you look on youtube a lot of people show this happening on videos. They say that they can break it down using a catalyst or by some kind of device that formats the water with magnets or some other special design to excite it to be used as fuel. Are they all lying? Some videos are very convincing.
I understand science as we know it says this is not possible.
I just don’t understand how we can be so sure. What if someone invented a new way or found a new catalyst that works better than the ones we already know about? How can we be sure?
Please do not insult me. I just do not know about engines or water. I am trying to figure this all out. It is hard to tell on the internet what is reliable and what is not.
Quote Comment
July 26th, 2010 at 9:07 pm
Brian Walters said:
All of the videos you have seen on this subject are faked, or at best not telling the whole story.
We can be sure because of the First Law of thermodynamics which states that energy cannot be created or destroyed, rather the amount of energy lost in a steady state process cannot be greater than the amount of energy gained.
Thus there is no way that more energy can be taken out of these water – hydrogen/oxygen systems than is put in. It is just that simple. It is the same reason perpetual motion machines cannot be. The First Law always rules, and it rules everywhere.
Quote Comment
July 27th, 2010 at 2:48 am
Brian,
One concept that is useful when you ponder the water car is the “ground state.” Consider the trebuchet in which the energy to fling a missile is provided by a large stone as it falls toward the ground. There is a finite, calculable amount of energy stored in the hoisted stone. It is the mass of the stone times the acceleration due to gravity times the change in elevation (a distance). A 200kg mass hoisted 3m into the air has a potential energy of:
When you hoist the stone, you change it from its ground state to an elevated state with 5,886J of potential energy.
As the stone falls, a large portion of that 5,886J is transferred to the missile as kinetic energy, and some portion of that is transferred to the target on impact. Some of the energy is lost as friction and some remains with the stone as it swings near the bottom of its arc. The stone eventually comes back to rest at its ground state where it has no more energy. To reset the trebuchet, you must hoist the stone back into the air.
Regardless of what method you use to hoist that stone, the energy you expend will always equal 5,886J + L, where L is the sum of any losses involved in hoisting, and L is always greater than zero. You can improve technology and efficiency as much as you want, but even as L approaches zero, you will always have that 5,886J that you must provide.
Now lets think about water as you might use it to power a car. Water, for these purposes, is a chemical “ground state” of hydrogen, which is the fuel you are after. Separating it from oxygen is similar to hoisting the trebuchet stone into the air. The oxidized state (H2O) is analogous to the unhoisted stone, and the elemental state (H2) is analogous to the hoisted stone. There is a finite, calculable change in the chemical energy of hydrogen relative to its “ground state.” Recombining hydrogen with oxygen, like dropping the trebuchet stone, releases energy that can be transferred to the kinetic energy of a car.
Again, regardless of what method you use to separate hydrogen from oxygen, the energy you expend will always equal that change in chemical energy + L. You can reduce L through technological advances, but you will always have to provide energy greater than what you get out of the reaction.
Further, when the trebuchet stone is at rest at the bottom of its arc, there is no way to get it to fling a missile without hoisting the stone out of its ground state. Just so, there is no more chemical energy to be squeezed out of water without disassociating it first.
These limitations are pretty fundamental and overcoming them is basically magic.
Quote Comment
July 27th, 2010 at 4:48 am
@Shafe : You are perfectly clear in your explanations, and i hope Brian Walters will understand.
Some optimisations may be found in the way energy is transferred to the system, to break for instance the water molecule : vibration is a way to achieve resonance, where the mechanical energy necessary to break something may be surprisingly lower than expected. The well known bridge resonance is always surprising : http://www.youtube.com/watch?v=3mclp9QmCGs
Some people expect to find some resonance frequency for the water molecule to help break it with low energy input, but it has not been found or published as far as i know.
Sometimes, new laws are discovered, that help explain natural phenomenoms that are not explained by standard laws that you have presented with the rock and trebuchet. For instance, natural radioactivity is impossible in that mechanical modelling, as atomic kernel is naturally mechanically stable. Only quantic physic gave some explanations about this, with the “tunnel effect” :
http://www.bun.kyoto-u.ac.jp/~suchii/Bohr/tunnel.html
http://en.wikipedia.org/wiki/Quantum_tunnelling
This is a clear demonstration that at atomic scale, some high energy process can happen with less energy than expected from classical mechanical modelisation : all transistors of today electronic systems are based on that effect
But until now, the dream about finding energy from new physical effects, is the only energy that create move in some people
Quote Comment
July 27th, 2010 at 5:12 am
@Brian Walters :
“Please do not insult me”
yes, i am also finding too much insults on this blog, and not any reaction from blog author to limit them.
Quote Comment
July 27th, 2010 at 6:13 am
@drbuzz0 :
Thank you for beginning a real technical discussion, away from the insults of others.
Concerning the name of the process, i would propose “open loop compression/decompression”.
You may also find “closed loop compression/decompression” process, like proposed by :
http://www.isentropic.co.uk/index.php?page=storage
They present a system that achieve round trip efficiency over 72% – 80%,by storing compress gaz (argon in this case) and both heat and cold.
Concerning the electrical batteries efficiency, this is only one part of a car design. You may only compare it to the storage stage between compression and decompression stages, that is 99,999% efficient.
The main part of the design is transportation efficiency, meaning that if the goal is to transport 80kg of human flesh, transporting 1500kg of steel must be avoided. This way, the electric bicycle or motorcycle is the best transportation system, and to this aspect, China is the most evolved country i know.
Still concerning the batteries, what are your sources ? lead acid battery efficiency seems closer to 50% than to 80%. And for the global efficiency, we need to take into account the AC-DC loading system, in the order of 80%, and the regulation system from battery to engine, that may not exceed 90%.
The last point about batteries is that their weight keep the same even when they are emptying, so that the power of the car may be very limited in the last part of the autonomy curve.
Concerning the ICE engine, you only show a large diesel, but current cars use small engine with fast RPM, and actual efficiency is around 10% from independant sources :
9 to 11% in page 378 of book :
http://www.oecdbookshop.org/oecd/display.asp?K=5LMQCR2K899X&cid=sourceoecd&lang=EN&sf1=Title&sort=sort_date%2Fd&st1=fuel&sf4=SubVersionCode&st4=not+E4+or+E5+or+P5&m=64&dc=80&plang=en
Concerning the efficiency of an open loop compression/decompression process, it is stated at 26% by the berkeley study, that is clearly pessimistic about compressed air car.
But as air car is lighter than electric car, the real car efficiency is around 44%, at the same level than the electric smart at 44%, when basic calculations errors are corrected :
http://www.mdi.lu/charge.php?nomfichier=Mistakes.pdf
This does not take into account the possible optimisations of compression stage, that will occur as soon as market is ready.
The difference is in cost : batteries are very expensive with a limited life to 1000 at 2000 loads. Compressed air tanks have 12000 loads certification at least, that is 32 years with 1 load each day of the year.
Clearly, the compressed air car is a small car, very convenient for european cities. But the autonomy will be longer than 30 miles : it should be around 2 hours of running, but only 3mn to reload.
The other point is that we are able to store 10 days of energy in less than 3m3 at home, allowing storage of compressed air at home from sun or wind, even if sun or wind are not available everyday. If not used, this energy would be lost, so efficiency of 44% is always better than 0%.
Quote Comment
July 27th, 2010 at 6:16 am
brnd said:
Again, make all the technological advances and efficiency improvements you want, you still must provide an amount of energy equivalent to the difference in the energy states of the beginning and end conditions plus an entropy tax. If you find a resonant frequency that reduces the electric energy required for electrolysis below that amount, you can bet that you’re paying for it through the device that is causing the molecules to resonate.
In the bridge example, you are using resonant frequency to increase the entropy of the bridge by breaking it apart. Breaking apart a water molecule serves to decrease entropy, more akin to assembling a bridge than tearing one down.
brnd said:
Wrong. Rock is up: high energy isotope. Rock is down: low energy isotope. Flying missile: electrons powering my TV.
brnd said:
And yet my computer still can’t power itself. Quantum mechanics, don’t trump the laws of thermodynamics in automobiles. When my local garage hires a quantum mechanic, I’ll change my tune.
Quote Comment
July 27th, 2010 at 6:35 am
brnd said:
Apparently your grasp of the rest of physics is no better than your grasp of thermodynamics. Nor does the fact that some processes like radioactive decay seem to violate the laws classic physics, (it doesn’t actually when you look close enough) or things like quantum tunnelling, mean that there is a possibility that these laws can be violated on the macro level in electrochemical systems. The best any catalyst, or resonant effect can do is to minimize thermal losses during conversion BUT NO MORE ENERGY WILL BE MADE never, ever.
brnd said:
That is because there are some that persist on arguing long past the point where they have been shown they are wrong. Going over and over the same ground, showing that certain ideas are just plain false, and having the same person coming back, insisting they are right, without any proof to back themselves up gets annoying. When someone like this shows up, and won’t make the effort to learn why they are wrong, they do leave themselves open to insult.
Quote Comment
July 27th, 2010 at 6:58 am
@Shafe :
I did begin by saying that i was agreeing with your preceding post.
“And yet my computer still can’t power itself. Quantum mechanics, don’t trump the laws of thermodynamics in automobiles.”
I also agree with that and did not say anything against that.
Optimisations decrease the losses, it never change the global balance.
Quote Comment
July 27th, 2010 at 7:08 am
@DV82XL
“BUT NO MORE ENERGY WILL BE MADE “
Did i ever say the opposite ?
Pretending that somebody says something, and then showing it is wrong, is current desinformation method.
“they do leave themselves open to insult”
Insulting is only showing disability to cope with reality.
This is also a part of desinformation strategy, trying to create emotions so that target makes errors.
Quote Comment
July 27th, 2010 at 7:28 am
brnd said:
True, you did agree. At the same time, the rest of your post seems to be apologetic of efforts to promote perpetual motion machines.
My post made plenty of allowances for the possibility of efficiency improvements. When you brought up quantum tunneling and “classically impossible” phenomena you only served to muddy the issue. And that is that no machine will never achieve unity, regardless of how vividly an inventor the dreams.
Quote Comment
July 27th, 2010 at 7:50 am
@Shafe :
Sorry not to be clear on that, this is basis for me and i thought your post was clear enough.
But i was answering @Brian Walters writing that :
“I understand science as we know it says this is not possible. “
He is true that sometimes, new advancements explain observations that would be forbidden under known laws, and tunnel effect was indeed forbidden by known laws before quantic physic.
But it never changed the basic thermodynamic principles we know about energy dissipation, or entropy. Even the most advanced phenomenons like kasimir effect or particles intrication are following the entropy principle.
Quote Comment
July 27th, 2010 at 8:45 am
brnd said:
It doesn’t quite work like that. The bridge analogy is not a very good one for molecules. First of all, it’s not an issue of “breaking apart” the water. It’s a chemical process. energy is needed to liberate the hydrogen from the oxygen which are bonded.
With resonance with something like a bridge, it comes down to how often it is being pushed in a given direction. When the bridge is pushed it moves and then comes back. This happens at a given frequency. Random pushes will not tend to reinforce the oscillations, but if the pushes happen in timing that has them push when the bridge naturally oscillates they reinforce each-other and each one deposits more energy.
The Tacoma Narrows Bridge is used as an example of resonance, but that’s a bit overly simplistic. The fact is the bridge had some other big issues. The bridge had sidepannels that caught too much of the wind, it lacked dampening factors and it also had an unexpected tendency toward aeroelastic flutter. It was actually the flutter that destroyed the bridge. It fluttered in a way that was close to the resonant frequency.
Molecules have resonant frequencies too, but this does not mean that they necessarily are going to be easy to “break” by using a resonant frequency. The most direct resonance is very high frequency, because atoms molecules are small. The Mössbauer effect is where an atom recoils and emits a gamma ray. Since particles have magnetic properties they also have magnetic moment and magnetic resonance. Then there are lower frequency harmonics.
When it comes to splitting water into hydrogen and oxygen, a great deal of research has been done at improving the process and general efficiency. Various materials have been tried for electrodes in electrolysis. Various additives have been added to the water. Developments have included regenerative fuel cells, thermochemical methods of splitting water, photocatalytic methods etc etc etc.
There has been some improvement in efficiency, but its fairly marginal. Thermochemical methods and high temperature steam electrolysis are attractive. They don’t necessarily have much better total efficiency than conventional electrolysis, but what they do have is that they use heat and not electricity as the energy.
Thermal energy is “cheaper” because when electricity is used, you’ve already incurred significant loss from the thermal engine, not to mention regulation, rectification and so on.
Quote Comment
July 27th, 2010 at 9:02 am
@drbuzz0 :
Yes i agree that collapsing bridge detailled explanations are quite complicated. But it was a rough image of the link between atoms of hydrogen and oxygen in water, explaining why lot of ideas for hydrogen production consist in adding some high frequency components to the electrolysis current.
The heat strategy for hydrogen production is intended to be produced by concentrated solar light, thus allowing a direct way of storing sun power, with the easy competition of 14% low efficiency of photovoltaic. There is no useful result until now, as far as i know.
Quote Comment
August 3rd, 2010 at 3:23 am
@drbuzz0 :
Thank you for beginning a real technical discussion, away from the insults of others.
Concerning the name of the process, i would propose “open loop compression/decompression”.
You may also find “closed loop compression/decompression” process, like proposed by :
http://www.isentropic.co.uk/index.php?page=storage
They present a system that achieve round trip efficiency over 72% – 80%,by storing compress gaz (argon in this case) and both heat and cold.
Concerning the electrical batteries efficiency, this is only one part of a car design. You may only compare it to the storage stage between compression and decompression stages, that is 99,999% efficient.
The main part of the design is transportation efficiency, meaning that if the goal is to transport 80kg of human flesh, transporting 1500kg of steel must be avoided. This way, the electric bicycle or motorcycle is the best transportation system, and to this aspect, China is the most evolved country i know.
Still concerning the batteries, what are your sources ? lead acid battery efficiency seems closer to 50% than to 80%. And for the global efficiency, we need to take into account the AC-DC loading system, in the order of 80%, and the regulation system from battery to engine, that may not exceed 90%.
The last point about batteries is that their weight keep the same even when they are emptying, so that the power of the car may be very limited in the last part of the autonomy curve.
Concerning the ICE engine, you only show a large diesel, but current cars use small engine with fast RPM, and actual efficiency is around 10% from independant sources :
9 to 11% in page 378 of book :
http://www.oecdbookshop.org/oecd/display.asp?K=5LMQCR2K899X&cid=sourceoecd&lang=EN&sf1=Title&sort=sort_date%2Fd&st1=fuel&sf4=SubVersionCode&st4=not+E4+or+E5+or+P5&m=64&dc=80&plang=en
Concerning the efficiency of an open loop compression/decompression process, it is stated at 26% by the berkeley study, that is clearly pessimistic about compressed air car.
But as air car is lighter than electric car, the real car efficiency is around 44%, at the same level than the electric smart at 44%, when basic calculations errors are corrected :
http://www.mdi.lu/charge.php?nomfichier=Mistakes.pdf
This does not take into account the possible optimisations of compression stage, that will occur as soon as market is ready.
The difference is in cost : batteries are very expensive with a limited life to 1000 at 2000 loads. Compressed air tanks have 12000 loads certification at least, that is 32 years with 1 load each day of the year.
Clearly, the compressed air car is a small car, very convenient for european cities. But the autonomy will be longer than 30 miles : it should be around 2 hours of running, but only 3mn to reload.
The other point is that we are able to store 10 days of energy in less than 3m3 at home, allowing storage of compressed air at home from sun or wind, even if sun or wind are not available everyday. If not used, this energy would be lost, so efficiency of 44% is always better than 0%.
Quote Comment
August 3rd, 2010 at 4:09 am
As usual brnd, you are doing nothing except pulling numbers out of your ass, and referencing material that has no relation to the argument at hand.
To store heat in any material will require a large mass, that will have to be hauled around, make in this scheme by Isentropic Ltd impractical for mobile use. That is of course it works at all, something that I would like to see the thermal transfer rates stated more clearly before I will believe it.
The rest of your assertions are, as usual, unsupported colourful dreams, without any foundation beyond your over-active imagination.
Quote Comment
August 6th, 2010 at 2:19 am
You really like to make fun of you, DV82XL ?
I hope for you this is just a theatre trick.
If you only try 1 time to really read before answering, it will go better for you.
Quote Comment
August 6th, 2010 at 3:42 am
brnd said:
I did read what you linked to above, and I did read the rest of your post and gave you an answer. You are just plain wrong, and nothing you liked to proves any different. That is not making fun of you, that is just the bald truth.
Quote Comment
August 6th, 2010 at 9:27 am
“You are just plain wrong”
There is no use to that, i may also be red, yellow or blue : what is the point ?
It would be far more useful to explain why a specific part of text may be wrong.
Quote Comment
August 6th, 2010 at 11:54 am
brnd said:
You tiresome little man. What do you think I did in comment #70?
To store heat in mass requires a large mass. Large masses reduce the power-to-weight ratio of any motive power scheme. In this case to the point where it is unlikely that such a vehicle would every move.
Furthermore, I doubt that the fixed system you linked to, can achieve the sort of numbers that are being claimed there. I would have to see a much better treatment of the engineering and calculations than what is available from that company but 80% recovery seems unlikely given what is known about thermal systems.
The rest of you post is your belief that there are major gains to be made in optimisation of compression stage, which you have not proven before, and which has been replied to, in detail up thread, showing you why your ideas are in error.
Endlessly repeating yourself will never make you more right.
Quote Comment
August 6th, 2010 at 11:13 pm
brnd said:
Well, I gave it a shot…
Quote Comment
August 10th, 2010 at 6:01 am
drbuzz0 said:
What do you mean ?
You gave some figures about batteries and diesel, and i have answered to that without any answer from you.
For instance :
Concerning the ICE engine, you only show a large diesel, but current cars use small engine with fast RPM, and actual efficiency is around 10% from independant sources :
9 to 11% in page 378 of book :
http://www.oecdbookshop.org/oecd/display.asp?K=5LMQCR2K899X&cid=sourceoecd&lang=EN&sf1=Title&sort=sort_date%2Fd&st1=fuel&sf4=SubVersionCode&st4=not+E4+or+E5+or+P5&m=64&dc=80&plang=en
Concerning the efficiency of an open loop compression/decompression process, it is stated at 26% by the berkeley study, that is clearly pessimistic about compressed air car.
But as air car is lighter than electric car, the real car efficiency is around 44%, at the same level than the electric smart at 44%, when basic calculations errors are corrected :
http://www.mdi.lu/charge.php?nomfichier=Mistakes.pdf
Quote Comment
November 6th, 2010 at 2:23 pm
CNN is showing the last development of the Airpod :
http://edition.cnn.com/video/#/video/international/2010/10/27/ef.air.pod.car.bk.c.cnn?iref=allsearch
Airpod is the new car using compressed air. It is dedicated to urban transportation, where speed is low, less than 80km/h or 50mph.
Price should be around 10,000usd, far less than just the batteries for an electric car.
The real interest is that by having some extra compressed air tank at home, you can compress air when sun is shining with solar panels, and use it when you need. This is the first step to real home autonomy in transportation.
Quote Comment
November 6th, 2010 at 3:50 pm
brnd said:
Idiotic. at ten grand it’s more expensive than a reasonably priced used car, which has much greater utility and is far safer. if you really wanted to save money you could just get a moped or something. Yes, it will take gas, but nowhere near ten grand worth over the next several years.
Why on earth would you charge it with solar panels? Air compressors are so power hungry and so extremely inefficient that you’d pay through the nose for all the solar cells it would take to drive an air compressor for that kind of vehicle. It’d be cheaper to buy grid power.
If you really want to go with a non-gasoline system, battery-electric is still the way to go. Ten grand might be less than “just the batteries” for a full sized high-end electric car. But if you’re looking for something small, slow and of limited range (like that ridiculous thing) you could buy something like this:
http://salestores.com/xtremexm4000.html
Half the cost! Best of all, good battery charger cycles are better than 90% efficient, not about 10% like compressed air.
Quote Comment
November 7th, 2010 at 11:45 am
brnd said:
This is far from the scientific method you try to explain on you web site. Don’t become religious.
brnd said:
You can’t compare a used car with a new car. And buying price is not total cost of ownership. In europe, gasoline is around 8$ per gallon (2$ per litre) : saving on power is very cost efficient.
brnd said:
Yes, you can. But who want to be on the list of 2 wheels accident victims ? Or who want to be able to take 2 children to school or some shopping home ?
brnd said:
To have a real autonomy for power : with solar panels, you can compress air at home, while sun is shining, and load enough air tanks to run for 1 or 2 months.
brnd said:
Change your compressor for a better one
brnd said:
What is cost of grid power in USA now ? In Europe, it is more than 0,15$/kWh. With solar panel at 3$/Wp, this is same cost, except that you don’t waste earth ressources with solar panels electricity.
brnd said:
Still the scientific method vocabulary ?
brnd said:
Please do some real testing in real life : i know no battery charger + battery at 90% efficiency.
Isothermal cycling for power storing can be around 90% efficiency :
http://www.sustainx.com/isothermal_cycling.html
Just read some nice explanation about compressed air thermodynamic :
http://www.sustainx.com/thermo101.html
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November 7th, 2010 at 11:47 am
Sorry for the error in editing, all quotes were from drbuzz0, as you may notice.
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November 7th, 2010 at 1:59 pm
brnd said:
In case you have not noticed, I’m not above calling them as I see them.
Some things are idiotic.
brnd said:
Why not? I paid less than ten grand for a very nice car that’s a couple years old and in very good condition.
New cars are a luxury item. However, if you really want, you can get a brand new (base model with no options) Hundi or Kia for about ten grand. That still has infinitely more utility than this joke.
brnd said:
If you buy that thing, safety is obviously not a concern at all. It’s not exactly “roomy” either.
brnd said:
Are you freakin kidding me? Those are going to be some damn big tanks and I’d expect it would take at least many months to charge them.
brnd said:
No… it’s the nature of the beast. Compressors use a lot of energy and most is wasted as lost heat.
brnd said:
Where I am it’s more like $.10 per kWh, but that’s besides the point. Residential solar is only economically feasible when heavily subsidized and even then, it’s at best questionable.
Now lets stop and consider the math of this.
If you actually want to power that thing, you’re looking at filling the 175 liter tanks with air at 350 bar of pressure.
That’s more than 5,000 PSI, by the way – beyond the capabilities of any standard air compressor used for air tools or other standard duty work. Infact, it’s more than most scuba tanks will take.
You’re going to need a super high pressure compressor for that.
After a lot of looking around the cheapest compressor I could find that would fill that kind of pressure requirement goes for about $8,000-$10,000 new. Here’s one that is used for $4,500: http://forsale.oodle.com/view/scuba-paintball-compressor-8-cfm-single-phase-5000-psi/2242043831-north-bonneville-wa/
1 bar = 0.987 atm. Therefore, 175 liters = 60,453.75 liters of air crammed into those tanks
That is 2,135 cubic feet (sorry for using non-si units, but that’s what compressors are measured in)
Now you get roughly one cfm (cubic foot per minute) per horsepower with a good scuba-grade compressor at maximum pressure. Five horsepower = 3 728.5 watts. In the real world it’s going to be more like 4kw because of the fact that motors are not 100% efficient.
So… We run the 4 kilowatt compressor for 427 minutes. Just over seven hours.
All in all roughly 29 kilowatt hours used.
$4.35 at 15 cents per kilowatt hour.
That will get you a maximum of 50 kilometers (assuming that you drive slow, because that’s the maximum distance, meaning under ideal conditions)
A small car can easily drive that on a single gallon of gas, which in the US is well under four bucks a gallon.
BUT WHAT ABOUT EUROPE YOU SAY???
Notice that this thingy is not a car. It’s a very very light weight vehicle with a tiny motor and a tiny amount of cargo, low speed and no protection at all.
By comparison a medium sized motorcycle with sidecar (a more fair comparison for size) will be faster and will still get you as much as 100 km on a liter of gasoline.
So…economics fail.
That’s even putting aside the fact that you pay ten grand for the vehicle plus another ten grand for the compressor and that for that cost you have something considerably less useful than a cheap used car.
brnd said:
Yes, and so is the word “stupid.”
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November 8th, 2010 at 6:41 am
drbuzz0 said:
I don’t know any used car that use less than 5 litres per 100km, that is 50kWh at least. And you canot drive without costly technical check up. With this car, new will be cheaper than used.
The goal of this type of light car is being able to rent them like bicycles in large cities.
drbuzz0 said:
In city, speed limit is under 50km/h. No metal doesn’t mean fragile : F1 race car use plastic, like aircrafts.
See http://www.lhaviation.com/en
drbuzz0 said:
drbuzz0 said:
Bad compressors use lot of energy, please try good compressors like this :
http://www.bauer-compresseurs.com/en/produkte/erdgas_cng/us_produkte/index.php
Other solutions exist to achieve 90% efficiency :
http://www.sustainx.com/isothermal_cycling.html
This is technically possible but you need work to achieve it.
drbuzz0 said:
yes, if this is new for you, it means that you have never made any inquiry in this area : do you speak just for flaming ?
drbuzz0 said:
Now that silicium panels are available at less than 2$/Wp, electricity cost is less than 0,06$/kWh for 1500h of sun each year during 25 years (ie 2 / (1500×25)= 0,053$/kWh).
drbuzz0 said:
Having a car is not the same than motorcycle, specially with rain.
But airpod will not use more energy than motorcycle of same weight.
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December 26th, 2010 at 10:04 pm
What if air at 350 bar and 20 C or so is liquid? That would mean that there would be a lot more of air inside the tank to expand through the air car’s engine, right?
Has anyone made this kind of calculation or taken this into account?
Ivo
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December 27th, 2010 at 12:02 am
Ivo said:
No, there would be liquid, which would need HEAT to expand into a gas, which it would have to do to preform any work. The energy to do that work would come from the HEAT not the change in pressure of the stored air.
Look people there are THREE parts to a gas/energy system Pressure, Volume and Heat. All three must be accounted for in any calculations – all of them, every single time.
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December 27th, 2010 at 1:13 am
DV82XL said:
Besides – 350 Bars??? Energy issues aside, I’m sure as hell not getting near anything under that kind of pressure going over a pothole, much less sitting on top of it.
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January 1st, 2011 at 11:45 am
There are a lot of big claims being made about making compressed air powered cars or fixed energy storage very efficient by managing the thermal aspects with big heat exchangers or using thermal mass or something to have isothermal compression and expansion of the fluids. It appears to have something to it when you look at the purely theoretical mathematics that only take into account a very simplified and perfect situation where you start off with the presumption that you have perfectly efficient heat exchangers, an infinitely large and perfect cooling fluid that circulates on its own without any resistance.
It does not really work that way. You always lose energy in compression and managing the heat is always going to cost you something. The more compression and the more heat the more it costs you and you never get it back. Notice that none of these pie in the sky ideas have ever actually happened in the real world.
I’m glad at least one page does a good job in dismissing this ridiculous idea.
It’s concerning to see so much focus on this because it could just destroy the pneumatic industry. Air power is great for many things but not for storing energy for reuse. Air cylinders are not batteries and don’t do a good job in that capacity. They are very good at producing large amounts of reliable power quickly to activate brakes or servos or to do any number of other things. There are now subsidies and investments trying to turn them into a way of keeping energy. Mark my words, if this idiocy grows enough, it will kill the whole industry, because you can’t keep focusing your R&D on an empty idea that will not give you results. If you spend enough time on something like an air powered car, you will end up burning all your money and have wasted your time when you could have been applying it to building something useful like nailguns or jackhammers or air brakes.
Keep up the good work. Some idiotic ideas need to be torn down before they tear down the good ones.
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January 1st, 2011 at 11:54 am
Pneumatic Engineer Bill said:
I doubt that the compressed air industry can be killed by something like this. Where compressed air is used, it is just the best for the application, since it is likely going to be the most expensive energy per watthour of the options. In every case I can think of, its utility has offset the cost.
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January 1st, 2011 at 1:05 pm
DV82XL said:
I’d be surprised if it could kill an industry, but it could do some harm (just the diversion of research to useless crap alone could set things back).
Maybe for a few applications the alternatives to compressed air might be able to get ahead due to the improvements needed for air to remain competitive being starved of resources due to the air car nonsense (though even that’s probably a stretch and the compressed air industry seems to be reasonably mature).
Though I wouldn’t be too surprised if the air car companies end up taking other companies with them.
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January 1st, 2011 at 3:57 pm
Okay, you got me. I might have been too dramatic. It won’t kill the whole industry, because it won’t change the fact that there are times when pneumatic energy is the best way to go. It can cause harm though.
If it is promoted and subsidized enough and enough companies get into the act, then there is the danger of a big bubble bursting. You can’t keep working on an empty concept without any merit forever. When you start pushing a new product you expect to be in the red at first. You always must spend some money to get started, so you might lose it in the beginning but regain it once you get a market. If the product is a bad idea then you never make back that investment and the debt just grows until you can’t take it on anymore and it all comes down in bankruptcy.
There is government money being spent on this and companies are now being enticed to start looking at compressed energy storage and that’s a dead end. Someone is going to get hosed when the bill comes and the dreams don’t pan out. Some companies know enough to realize they should just do enough work on it to get the subsidies but there are others that could take the pill on this thinking it is the wave of the future.
Don’t think that companies are always going to know better. The suits don’t always get the message, and it doesn’t matter how hard their engineers and techs try if there’s enough irrational excitement over something stupid.
This is one of the worst ideas I have seen in my life.
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January 1st, 2011 at 4:02 pm
Pneumatic Engineer Bill said:
Agreed on both counts.
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