Living Car Free - Air powered car...

This may be a repost, but I suppose it has something to do with this living car free idea... (I don't really know why, its just that I have seen many similar threads pop up here from time to time so I might as well pile more of them in ! )


http://www.gizmag.com/go/7000/


Some thoughts:


1. still consumes lots of resources to build..
2. compressed air has to be compressed by something more powerfull than human power...
3. it has some powerful batteries in it to run the radio and other electronics...

etc... discuss ...

hmmm....compressed air.....could be good for an assisted pedaling bike or velomobile if the empty tank is significantly lighter than the full tank

This may be a repost, but I suppose it has something to do with this living car free idea... (I don't really know why, its just that I have seen many similar threads pop up here from time to time so I might as well pile more of them in ! )


http://www.gizmag.com/go/7000/


Some thoughts:


1. still consumes lots of resources to build..
2. compressed air has to be compressed by something more powerfull than human power...
3. it has some powerful batteries in it to run the radio and other electronics...

etc... discuss ...

Another potential problem, last night when I went to work it was +2C, when I got out of work at 7:30 this morning it was -10C, what happens to air pressure when the temperature drops? Well the pressure drops, so you would need enough pressure that it can withstand a drop in pressure from a temperature drop of 20C (36F) degrees at a minimum.

Another potential problem, last night when I went to work it was +2C, when I got out of work at 7:30 this morning it was -10C, what happens to air pressure when the temperature drops? Well the pressure drops, so you would need enough pressure that it can withstand a drop in pressure from a temperature drop of 20C (36F) degrees at a minimum.


I don't know how much outside temperature will affect the pressure in the tank once it has been filled up..

If you make it hotter, it will expand slightly in the tank, increasing the pressure - if you make it colder it will slightly drop the pressure... I don't see the outside temp having such a big effect on the air in the tank...

? I don't think that if it got below freezing that it would have zero pressure... lol

I don't think that if it got below freezing that it would have zero pressure... lol

The pressure of a gas is directly proportional to the temperature in kelvins. If air were to stay a gas down to absolute zero temperature (-460 degrees F or zero kelvins) that would be the point at which pressure dropped to zero.

I don't know how much outside temperature will affect the pressure in the tank once it has been filled up..

If you make it hotter, it will expand slightly in the tank, increasing the pressure - if you make it colder it will slightly drop the pressure... I don't see the outside temp having such a big effect on the air in the tank...

? I don't think that if it got below freezing that it would have zero pressure... lol

It doesn't have to be zero, suppose you need 500PSI for the car to work, the outside temperature is 100F, meaning if it sits for a while, say while your at work, the air temperature in the tank will be 100F, your tank contains 520PSI, a cold front moves through, and the temperature drops to 70F, real nasty thunderstorm, and a tornado took out a trailer park, two counties over. Temperature in the tank also ends up at 70F, now for every 10F degree drop you lose 10PSI, so your tank is now 490PSI, and you get the air car equivilent of errrrrrrr errrrrrrrr errrrrrrr cough errrrrrrrr errrrrrr errrrrrr cough errrrrrrrr...:o . Those of you from Canada and the Northern US who thought they could get another winter out of a 6 year old car battery will know what I mean here:rolleyes:

This is nothing more than a gadget like the hydrogen car. Hydrogen, compressed air etc are not energy sources they are just ways of moving energy. Energy had to be used to purify the hydrogen and compress the air. Neither really solve anything unless you are going to use renewable energy to produce all of this.

Nothing is as easy as the stuff we can just pump out of the ground and waste! :rolleyes:

Also, if we just built and bought cars that were as light as those compressed air cars they would get 100+ miles per gallon.

In The Air Car the air is stored at 300 bar or around 4500 psi !!!
I'm a fan of this car. Tata, India's largest car maker, has signed a contract to use the technology.
It has some advantages over an electric car. It doesn't use batteries to store the energy used to power the car. The batteries it doesn't use don't have to be manufactured or disposed of.
Evidently air is a pretty efficient way to store energy since it has double the range of the most advanced electric car. The Air Car can also run on fossil fuels if the need be.
The Air Car can be refilled with compressed air in 2-3 minutes by a industrial compressor and 3-4 hours by a home compressor. The Altair Nanotech batteries take 10 minutes to recharge with an industrial charger but large scale production of these batteries has not yet happened.

How about an air powered bike? Two pannier sized carbon fiber tanks at 4500 psi could probably hold a lot of energy and, of course, they would be light. Direct the air on a motor similar to those used in pneumatic tools. That could possibly be built into the bottom bracket. Figure out some way to muffle the noise.

This is nothing more than a gadget like the hydrogen car. Hydrogen, compressed air etc are not energy sources they are just ways of moving energy. Energy had to be used to purify the hydrogen and compress the air. Neither really solve anything unless you are going to use renewable energy to produce all of this.
I'd say that energy storage and distribution is the biggest hurdle. America has plenty of open desert to generate solar and wind power, not to mention that (all paranoia aside) nuclear waste is perfectly manageable.

The problem is having the energy available where you need it and when you need it; not when the sun comes out, or when the wind blows, or in the nevada desert, or at the wrong horsepower. And the trick is to do it without creating additional waste like batteries and petroleum do. After all, all the energy stored in petroleum products originally came from the sun (which is actually a source of nuclear energy).

But I'm curious as to how they have managed to overcome the notorious efficiency problems of using compressed air for energy storage. If they have managed to overcome these efficiency problems then it seems to me that this technology would be more useful for providing an assist for human powered vehicles, as the current problem with electrically assisted HPVs are that empty batteries are a burden to carry and only add to the pollution when they need to be replaced every year.


How about an air powered bike? Two pannier sized carbon fiber tanks at 4500 psi could probably hold a lot of energy and, of course, they would be light. Direct the air on a motor similar to those used in pneumatic tools. That could possibly be built into the bottom bracket. Figure out some way to muffle the noise.
That's what I'm saying. Although I don't think it would be light when full, but that's ok because when the tanks are full you have the assist.

I also wouldn't expect the noise to be muffled. Sound is extremely difficult to contain.

I love the idea of the air powered car. I tend more to the right in my political leanings; as such, I am more concerned with the continued reliance on fossil fuels than I am with a holy war on automobiles. At the present, with the current flawed infrastructure in America, automobiles, no matter how they are powered, fill a need for many people.

That being said, as much as I like the air powered car and I have been following it for a couple of years now; it has no chance of success in the market. First, it has four wheels. The problem with that is that it can not be marketed as a motorcycle (which would almost kill it anyways, due to the need for a special driver’s license). The problem with this is that to be sold as a car it will need to meet all applicable safety regulations. That would add weight and complexity, greatly limit the range, require the vehicle to be bigger, and raise cost. We would be able to argue the merits of the various laws that apply to automobiles; but, we cannot argue that they exist and automobiles sold must conform to them. If, be some means, the manufacturer were able to get an exception it would lead us to the second reason that this car will not sell in America.

Americans do not want it. As a general rule, Americans do not care about fuel costs. This is evidenced by the continued market for stupidly large vehicles and engines, the rejection of diesels in the market, the insistence on automatic transmissions; I could continue but it all adds up to the failure to accept mechanisms that would not require lifestyle alterations but would reduce fuel consumption, and thus cost. Volkswagen was able to develop a two seat commuter car that achieved over 200mpg in normal use; Ford also used this same basic design as an experiment in the early nineteen eighties. The facts are that no one wanted these cars.

First, these cars fall prey to marketers and salesman, the basic argument is simple, “if you love your family or care about anyone who may ride with you then you would not buy that car.” Again, we can argue about real safety until we collapse for lack of oxygen; however, the marketers have created a perception and fear that driving anything smaller than a light armored vehicle puts your family at risk.

This leads to a market that consists solely of commuters, as a second car, and youths. Youths look at the top speed of these high efficiency vehicles and blanch. They then face family objections due to the perception of safety issues and quickly loose their interest in these vehicles that, quite frankly, did not excite them in the first place.

This leaves commuters as the only remaining market. While commuters should be considering these high efficiency solutions, if they were to think logically (really, they should be looking into light rail, busses, and bicycles as last mile solutions; but, that is an entirely different rant), people seldom think so logically; or, the values that the logical solution is based on are values that consider other factors higher than efficiency. These values may include the perceived need to impress co-workers and supervisors, the need to run errands before and after work (coupled with the perception that they need a light armored vehicle to run errands in), the psychological need to be able to intimidate other road users, I could go on but I only wish to point out that there are other needs (some of which may be a call, more for psychological help; than a need as others would define it) and that to the buyer of these vehicles, these are real needs. High efficiency vehicles seldom meet these needs.

As much as I would like to see a real market for, and selection of, high efficiency vehicles I believe that it will require a major shift in American thinking. I do not believer that we are at this shift; or, making meaningful progress toward it.

Summary, the air car is doomed to failure if it were even to come to America, which I doubt it will.

so your tank is now 490PSI, and you get the air car equivilent of errrrrrrr errrrrrrrr errrrrrrr cough errrrrrrrr errrrrrr errrrrrr cough errrrrrrrr...

The thing is, if the car weren't designed to operate with a large range of tank pressures, it would be useless. It has to start with a high pressure and operate at a steadily dropping pressure. That's the basis of compressed air as an energy-storage method.

How about an air powered bike? Two pannier sized carbon fiber tanks at 4500 psi could probably hold a lot of energy and, of course, they would be light. Direct the air on a motor similar to those used in pneumatic tools. That could possibly be built into the bottom bracket. Figure out some way to muffle the noise.

Rather then an air powered bike, how about an air assisted bike, when your going down hill, you press a button on the bars, a little compressor then compresses air, and puts it in the tank, kinda like an extra brake.

When your going up hill, rather then slogging it, you just press a different button, and it gives you a boost, so that instead of going 40MPH down hill, and 4MPH uphill, your keeping to a more constant speed in the middle. Haven't we all, going up the hill from hell, wished we could turn on a motor, and give us some help.:D

I think it would probably be easier to implement electrically though, a motor/generator in the hub, with a mid-bike battery and a controller on the bars. Could replace one of the brake levers, since the generator could be used to slow the bike, you would only need one brake.

Gah marketing speak. I can hardly tell where the energy's coming from with all those magical words.

Let's see what we have. An internal combustion engine that can run on air, an electric motor, a compressor, an air storage tank, a gas tank, and a battery. Am I right so far? Also some useless-sounding heater between the tank and the engine. (Why not put that energy straight into the gas or electric motor?)

So this is just a hybrid car that can use compressed air to supplant batteries. That's interesting, if it can be made cheaper or lighter. I still wouldn't want to be around one in a crash.

I remember Ford trying something similar: http://www.gizmag.com/go/1194/ This truck uses "hydraulic pressure" to store energy during braking. Looks like it's a concept that didn't go anywhere.

I wonder how much energy in needed to compress air, especially to very high pressures. Air compressors are known to be very inefficient, in some cases it takes 7-8 HP to compress enough air to get one horsepower of energy from the compressed air.

Rather then an air powered bike, how about an air assisted bike, when your going down hill, you press a button on the bars, a little compressor then compresses air, and puts it in the tank, kinda like an extra brake.

Electric-assisted bikes riders refer to this as regenerative braking, and it doesn't work on ebikes any better than it would on this concept. I get better energy returns from mounting a solar panel on the top of my rack trunk vs. installing a costly regenerative braking system on my ebike.


When your going up hill, rather then slogging it, you just press a different button, and it gives you a boost, so that instead of going 40MPH down hill, and 4MPH uphill, your keeping to a more constant speed in the middle. Haven't we all, going up the hill from hell, wished we could turn on a motor, and give us some help.:D

Have you ever heard of an electric-assist bicycle? All this air-powered bike discussion seems to be an effort at reinventing the wheel. The electric assist is superior in so many aspects including sound/air polution, engine efficiency, initial/maintenance cost, long-term durability, easy of implementation, etc. And you can refuel the battery on the 110V under your desk at work--do you think you could get away running an AIR COMPRESSOR under the radar of management?



I think it would probably be easier to implement electrically though, a motor/generator in the hub, with a mid-bike battery and a controller on the bars. Could replace one of the brake levers, since the generator could be used to slow the bike, you would only need one brake.

Have you ever heard of an electric-assist bicycle? All this air-powered bike discussion seems to be an effort at reinventing the wheel. The electric assist is superior in so many aspects including sound/air polution, engine efficiency, initial/maintenance cost, long-term durability, easy of implementation, etc. And you can refuel the battery on the 110V under your desk at work--do you think you could get away running an AIR COMPRESSOR under the radar of management?

Yeah, but when you run out of juice you still have to lug around the battery and you have to dispose of and replace the battery about once per year. At least the compressed air tank gets lighter as it runs out because that's when you'll be complaining about the extra weight. Also, at least you don't have to buy a new tank every year (and pollute the environment when you chuck the old one).

Yeah, but when you run out of juice you still have to lug around the battery and you have to dispose of and replace the battery about once per year. At least the compressed air tank gets lighter as it runs out because that's when you'll be complaining about the extra weight. Also, at least you don't have to buy a new tank every year (and pollute the environment when you chuck the old one).

It seems you are laboring under some missconceptions concerning ebikes. First, an ebike isn't a electric motorcycle with vestigial pedals tacked onto the side to conform to state/federal law; when the bike weighs more than 45kg it is not an ebike by my definition, and it can certainly be ridden as a bike with or without use of the motor.

For the sake of argument if we were to consider using lead acid batteries--the lowest cycle life of all existing chemistries--as a power source for an ebike project, they would be good for 10,000 miles before capacity fell short of 60% which is the accepted end-of-life criteria. This calculation is based upon 50%depth of discharge and 5 watt/hours per mile (a reasonable efficiency for a decent ebike). In my personal experience 50% DOD would be good for 50+ miles. Here are the battery specs so you can satisfy yourself.

http://www.bb-battery.com/productpages/EB/EB12-12.pdf

Recycling is already ongoing with lead based batteries, and if you're really concerned just go with NiMH or LiPoly or any number of other emerging green chemistries that are presently available or coming fast to the market. If you take issue with this, you might as well rally against using aluminum bicycles which are produced from recycled drink cans. Furthermore, if you really want to get radical how much fossil fuel energy is input into the total process to produce 5 watts of human power vs. the amount put into my battery powered ebike to produce the 5 watts necessary to propel me a mile down the road.

Yeah, but when you run out of juice you still have to lug around the battery and you have to dispose of and replace the battery about once per year. At least the compressed air tank gets lighter as it runs out because that's when you'll be complaining about the extra weight. Also, at least you don't have to buy a new tank every year (and pollute the environment when you chuck the old one).

But you will need to send the tanks out for hydro testing every five years if you live in the US. Oh, and you'll need a lot of earplugs. Compressed air operated motors are real loud. We're talking about an impact wrench kind of device.

This would be great in certain areas of the world combined with the right wind generation system. If there are periodic winds at night (as is seen near some coasts), then the air compressor can be connected to the home wind genset and charged off of that, w/o the need for a large home battery pack to store enough energy to power the compressor. Combined with a small home system for lights, entertainment, and an efficient fridge, with propane/solar water heating, the household costs would be incredibly small. Much less than the same system with two to three times the battery pack size to power an EV that needs it's batteries replaced periodically. Otoh, if an owner doesn't have this periodic wind at night, and relies on homepower/a big battery pack, or the public utilities, the advantage isn't as pronounced. But, I'm guessing given current battery costs/lifetimes, it'd still be cheaper in the long run. Like an EV, the best way to get long range cruising (~200-1000 miles) would be to add a small engine with a couple gears that could propel the car at ~60-70mph on flat ground to optimize fossil fuel efficiency.


Oh, and you'll need a lot of earplugs. Compressed air operated motors are real loud. We're talking about an impact wrench kind of device.

It's loud (http://www.motormdi.com/bbc.avi), but not that loud. ;)

Wait, didn't Hyde talk alot bout an air powered car? Seems hazy 2 me

Someone raised the question of the true energy cost required to recharge the 200bar tanks in the air car so I did some armchair calculations. According to MDI it takes 5.5 hrs to recharge the tank off a home 230V circuit and they claim a 125 mile range minimum. My experience has shown that these manufacturers overinflate their claims, but if we use their own numbers we get 303 watt/hours per mile. From the real world reports on the Xebra forum owners of this electric car are getting about 220 watt/hours per mile, and the Xebra electric car is based on the cheapest, flooded-cell, lead-acid batteries (basically golfcart batteries.) So am I missing something here? What does MDI base its claims of superiority to "even the most advanced battery technologies?"

Air-powered or fart-powered, it doesn't much matter.

The point is that we need to make the political and economic conditions encouraging for the development of some type of alternative to the petrol-powered dinosaurs. If we pass carbon taxes or cap-and-trade regulations, somebody will come up with alternatives.

But to the topic here, it does seem that air tanks would be lighter than either the current fuel tanks or batteries, so there might be some kind of potential for this idea. But obviously a lot of bugs need to be worked out in the design, and also alternative power generating systems need to be built.

Someone raised the question of the true energy cost required to recharge the 200bar tanks in the air car so I did some armchair calculations. According to MDI it takes 5.5 hrs to recharge the tank off a home 230V circuit and they claim a 125 mile range minimum. My experience has shown that these manufacturers overinflate their claims, but if we use their own numbers we get 303 watt/hours per mile. From the real world reports on the Xebra forum owners of this electric car are getting about 220 watt/hours per mile, and the Xebra electric car is based on the cheapest, flooded-cell, lead-acid batteries (basically golfcart batteries.) So am I missing something here? What does MDI base its claims of superiority to "even the most advanced battery technologies?"

I don't think your comparison is kosher. The big, I'm guessing really big, difference is in the charger and air compressor. I'm betting the home air compressor isn't nearly as efficient at transferring energy compared to the charger. This difference is reflected in the range if you use the energy to run the compressor instead of a decent approximation of the potential energy in a full tank to calculate the wh/mile comparison. Because auto efficiency is just a function of it's use of the onboard energy sink, I bet using the potential energy of the air in the tank would yield numbers inline with the manufacturer's claims.

It seems you are laboring under some missconceptions concerning ebikes. First, an ebike isn't a electric motorcycle with vestigial pedals tacked onto the side to conform to state/federal law; when the bike weighs more than 45kg it is not an ebike by my definition, and it can certainly be ridden as a bike with or without use of the motor.

For the sake of argument if we were to consider using lead acid batteries--the lowest cycle life of all existing chemistries--as a power source for an ebike project, they would be good for 10,000 miles before capacity fell short of 60% which is the accepted end-of-life criteria. This calculation is based upon 50%depth of discharge and 5 watt/hours per mile (a reasonable efficiency for a decent ebike). In my personal experience 50% DOD would be good for 50+ miles. Here are the battery specs so you can satisfy yourself.

http://www.bb-battery.com/productpages/EB/EB12-12.pdf

Recycling is already ongoing with lead based batteries, and if you're really concerned just go with NiMH or LiPoly or any number of other emerging green chemistries that are presently available or coming fast to the market. If you take issue with this, you might as well rally against using aluminum bicycles which are produced from recycled drink cans. Furthermore, if you really want to get radical how much fossil fuel energy is input into the total process to produce 5 watts of human power vs. the amount put into my battery powered ebike to produce the 5 watts necessary to propel me a mile down the road.
No misconceptions here. It doesn't have to be 45kg in order to be a major burden to ride when your battery runs out. The fact is that:
1. Batteries do not get any lighter when they are discharged.
2. Aluminum bicycles usually last much longer than one year.
3. Current widely available battery technologies either can not be recycled or require recycling processes which pollute the environment themselves ( and emerging or upcoming technologies rarely work as well or give as much value for your dollar, as well established mature technologies).

All of these points are things which compressed air technology could potentially improve upon. How can you be opposed to improvements when there is obviously room for them?

I also wouldn't expect the noise to be muffled. Sound is extremely difficult to contain.
How about this idea? Put some baffling in the downtube and use it as the exhaust pipe.
Here's another idea. On hot days route the exhaust stream on the rider. The exhaust temperature on The Air Car is between 0-15 degrees. Air conditioned bike !!!

No misconceptions here. It doesn't have to be 45kg in order to be a major burden to ride when your battery runs out. The fact is that:
1. Batteries do not get any lighter when they are discharged.
2. Aluminum bicycles usually last much longer than one year.
3. Current widely available battery technologies either can not be recycled or require recycling processes which pollute the environment themselves ( and emerging or upcoming technologies rarely work as well or give as much value for your dollar, as well established mature technologies).

All of these points are things which compressed air technology could potentially improve upon. How can you be opposed to improvements when there is obviously room for them?

Not opposed at all; I would be thrilled to see the roads populated by anything but the ICE. However, I grow weary of the constant excuses from people about existing technologies not be good enough while they wait indefinitely for a pie-in-the-sky solution.

As an example, my ebike rides like a regular bike. It can cruise at 30 mph. It has a range from 50 miles to infinity. I arrive at my destination not soaked in sweat nor exhausted, and it gets 10 miles to a penny of electricity. What more do people want before jumping onboard? Teleportation?

I don't think your comparison is kosher. The big, I'm guessing really big, difference is in the charger and air compressor. I'm betting the home air compressor isn't nearly as efficient at transferring energy compared to the charger. This difference is reflected in the range if you use the energy to run the compressor instead of a decent approximation of the potential energy in a full tank to calculate the wh/mile comparison. Because auto efficiency is just a function of it's use of the onboard energy sink, I bet using the potential energy of the air in the tank would yield numbers inline with the manufacturer's claims.

That's what I thought as well; the big efficiency gains with this compressed air technology will be made in more efficient compressors. The only assumption that I made in my calculations was that the "230V home compressor" MDI referred to was running on a typical 30A 220/230V circuit. The first thing to come to mind when I heard about this vehicle was the tremendous inefficiency compressing air. It would be hard to come close to the 90% efficiency of a typical battery charger in my estimation.

When it comes to wh/mile you have to calculate from the power outlet to make a fair comparison. However, it would be interesting to compare the efficiencies of a compressed air engine that derived its energy from a source other than electricity to that of an electric.

Rather then an air powered bike, how about an air assisted bike, when your going down hill, you press a button on the bars, a little compressor then compresses air, and puts it in the tank, kinda like an extra brake.

When your going up hill, rather then slogging it, you just press a different button, and it gives you a boost, so that instead of going 40MPH down hill, and 4MPH uphill, your keeping to a more constant speed in the middle. Haven't we all, going up the hill from hell, wished we could turn on a motor, and give us some help.:D

I think it would probably be easier to implement electrically though, a motor/generator in the hub, with a mid-bike battery and a controller on the bars. Could replace one of the brake levers, since the generator could be used to slow the bike, you would only need one brake.
It's better to power a bike by the crank rather than the wheels. With hub motors, to go faster means speeding up the motor which takes more energy. If the crank is powered you merely shift to a higher gear, the engine speed doesn't change. That's the principle behind the Stokemonkey.
I would think that an air motor such as those used on pneumatic tools and an air tank would be a lot simpler than an electric motor, batteries, and a controller. It would certainly be a lot lighter.

When it comes to wh/mile you have to calculate from the power outlet to make a fair comparison. However, it would be interesting to compare the efficiencies of a compressed air engine that derived its energy from a source other than electricity to that of an electric.

I've never heard of that. The point of wh/mile is to compared on board energy efficiency and glider efficiency. I suppose you could calculate total efficiency including what comes from the power plant, but that's not equivalent vehicle efficiency.

So this is just a hybrid car that can use compressed air to supplant batteries. That's interesting, if it can be made cheaper or lighter. I still wouldn't want to be around one in a crash.

According to the Gizmag article The Air Car costs 5500 pounds.
From the MDI site.
Compressed air tanks have already been proven safe by one of our partners EADS(AIRBUS). This company's reputation in the aeronautical field is unprecedented, given the reliability of its tanks. What's more, the compressed air does not present any risk of explosion. Countless test have been carried out in the most extreme conditions (gun shoots, resistance to fire...) to guarantee passenger safety in every possible condition. The high pressure tanks have been developed using a similar technology to those used in natural gas vehicles and by firefighters. All are produced with carbon fiber over plastic.
The tanks that MDI puts in its vehicles are similar to those already in use in natural gas buses in Germany and other countries.

actually hyde said that the government has a car that runs on water. anyways, I can't understand how you can overlook the energy it would take to charge and recharge the air tank. But ah well. Use electricity, to charge an air tank, to run a car. Or just use electricity, to run a car. hmm....

Have you ever heard of an electric-assist bicycle? All this air-powered bike discussion seems to be an effort at reinventing the wheel. The electric assist is superior in so many aspects including sound/air polution, engine efficiency, initial/maintenance cost, long-term durability, easy of implementation, etc. And you can refuel the battery on the 110V under your desk at work--do you think you could get away running an AIR COMPRESSOR under the radar of management?

Why would an electric bike pollute less? It uses batteries. It seems to me that it would pollute more.
Why would it cost less? It's far more complicated.
How could it be cheaper to maintain? Batteries need to be replaced. Electronics go haywire.
How could it be more durable? Batteries need to be replaced. Electronics go haywire.

What could be simpler than an air tank and air motor?

I've never heard of that. The point of wh/mile is to compared on board energy efficiency and glider efficiency. I suppose you could calculate total efficiency including what comes from the power plant, but that's not equivalent vehicle efficiency.

For our purposes what would be the point if you didn't calculate from the power outlet? We might as well look at a chart of the energy density of various fuel sources without regard for the input energy of creating the fuel to begin with. With an electric vehicle one has to account for the loss of energy first in the charger, then the loss in the charging of the battery, the loss in the conversion to mechanical energy by the motor (which varies with the rpms/torque of the motor). With the air engine one must account for the losses of the compressor as well as the inefficiency of the motor itself.

Compressed air--particularly when the tanks are polymer based--seems to offer an advantage over batteries in energy density. The following table shows that at 20bar it still has the upper hand over many battery chemistries.

http://en.wikipedia.org/wiki/Energy_density#Energy_density_in_energy_storage_and_in_fuel

But this means nothing unless we factor in the energy losses to produce the compressed air. Therefore, as I stated before you have to calculate from the "outlet" to be fair in your comparisons.

If we're going to calculate from the outlet to be fair, why stop there? Include plant generation efficiency and transfer to the outlet too, which is regional. Like I said before, the point of comparing it in the vehicle is to get an idea of glider efficiency and engine or motor efficiency, both of which are universal over the same driving cycle.

Either we're comparing more than just vehicle efficiency, or we're comparing some portion, or all, of well to wheel efficiency. We can't include the compressor/charger and claim we're comparing vehicle efficiency. That would be vehicle efficiency and "fueling" efficiency. Or whatever we feel like calling it. :D

Why would an electric bike pollute less? It uses batteries. It seems to me that it would pollute more.
Why would it cost less? It's far more complicated.
How could it be cheaper to maintain? Batteries need to be replaced. Electronics go haywire.
How could it be more durable? Batteries need to be replaced. Electronics go haywire.

What could be simpler than an air tank and air motor?

Well, you have noise pollution as well as the wasted energy in the grossly inefficient conversion of electrical energy to compressed air; go try to run a typical four ton residential A/C compressor on a home PV setup and you'll get the idea. Go to the MDI website and take a hard look at the engine--looks like as many close tolerance moving parts as a typical ICE. With a brushless elecric motor you have a cylinder rotating around a shaft riding on two bearings that's definitely more complicated. Have you seriously stopped and considered how complicated an air engine conversion for a bike would be. You have regulators, electronics to start/ stop the piston at TDC, radiators and electric preheaters for incoming air to the cylinder, mufflers to dampen the hideous racket, insulators to protect the rider from sub-freezing temperatures, and who knows what else to solve various design issues not to mention any electric accessory on the bike would require a seperate battery/charging system of its own. Real simple and durable alright.

If we're going to calculate from the outlet to be fair, why stop there?

By all means, don't stop there. Calculate the complete well to wheel efficiency. However, keep in mind that the important quantity is the difference in well to wheel efficiency between the two vehicles (electric and CA) and in order to calculate it we need only to consider from the outlet to the wheel.

By all means, don't stop there. Calculate the complete well to wheel efficiency. However, keep in mind that the important quantity is the difference in well to wheel efficiency between the two vehicles (electric and CA) and in order to calculate it we need only to consider from the outlet to the wheel.

And we need to consider vehicle infrastructure too. These may blow with a dinky home compressor at ~30% efficiency. But in their likely urban use, heavy duty industrial compressors (~70%?) can probably provide much better efficiency at filling stations located reasonable distances away from each other in the city. There's also the periodic replacement of batteries to contend with on the EV side, and even though the car's engine is technically an ICE, on compressed air it should last for quite a while. Not as long as the electric motor, but way longer than any battery available today.

Well, you have noise pollution as well as the wasted energy in the grossly inefficient conversion of electrical energy to compressed air; go try to run a typical four ton residential A/C compressor on a home PV setup and you'll get the idea. Go to the MDI sight and take a hard look at the engine--looks like as many close tolerance moving parts as a typical ICE. With a brushless elecric motor you have a cylinder rotating around a shaft riding on two bearings that's definitely more complicated. Have you seriously stopped and considered how complicated an air engine conversion for a bike would be. You have regulators, electronics to start/ stop the piston at TDC, radiators and electric preheaters for incoming air to the cylinder, mufflers to dampen the hideous racket, insulators to protect the rider from sub-freezing temperatures, and who knows what else to solve various design issues not to mention any electric accessory on the bike would require a seperate battery/charging system of its own. Real simple and durable alright. I'm not talking about using an MDI motor on a bicycle. My idea is to use an air motor like those found in pneumatic tools. I think it could be contained in the bottom bracket. It would really be nothing more than turbine blades on the bottom bracket spindle. A hole in the bottom bracket lets the air in. It is exhausted through the down tube or chain stay that has had baffles put in it. The exhaust air can be directed at the rider on hot days.
Pnuematic tools have no electronics or batteries and as far as I know they are not a hazard. I don't think controlling the speed requires any expensive, new, or elaborate technology. Heck, you can buy a pneumatic wrench for 30 bucks.
The Air Bike would be a lot easier to pedal with empty air tanks than an electric bike with dead batteries.
The really neat thing here is discovering the amount of energy that can be stored in compressed air.
It's amazing.

An air compressor can be powered by the same means as an electric generator.
A compressor can be powered by diesel, coal, wind, water, etc.
It doesn't have to be powered by electricity.
My point is that there doesn't have to be another energy conversion process to get compressed air.

I agree; the mating of modern technology to the concept of compressed air energy is fascinating. My hat is off to MDI, and I am going to give this a harder look in the coming years.

The energy density of compressed air in polymer containers is really surprising. Maybe somebody could harness this for HPV applications if they can make a simple, highly efficient engine and lick the freezing problem; this really is a wonderful time to be in the alternative energy biz.

An air compressor can be powered by the same means as an electric generator.
A compressor can be powered by diesel, coal, wind, water, etc.
It doesn't have to be powered by electricity.
My point is that there doesn't have to be another energy conversion process to get compressed air.

Yes. This was what I was trying to suggest to lyeinyoureye. It would be really interesting to compress the air by means other than electrical potential; that would make for a highly efficient vehicle. I just can't imagine how it might be accomplished.

Yes. This was what I was trying to suggest to lyeinyoureye.

Didya read my first post? I suggested something that has no efficiency in the first place. From a pragmatic POV.


This would be great in certain areas of the world combined with the right wind generation system. If there are periodic winds at night (as is seen near some coasts), then the air compressor can be connected to the home wind generator and charged off of that, w/o the need for a large home battery pack to store enough energy to power the compressor or expensive grid connection. Just run the generator output to some sort of capacitor to moderate the input and let it charge until it's full. Combined with a small home system for lights, entertainment, and an efficient fridge, with propane/solar water heating, the household costs would be incredibly small. Much less than the same system with two to three times the battery pack size to power an EV that needs it's batteries replaced periodically.

Using a form of chemical energy onsite would just drop the efficiency of using that chemical energy. Course there are probably other ways to get electricity or mechanical work. But I doubt I can take some of the waste heat from a wood stove and use it to power a compressor. We need either electricity, or some form of chemical energy for most compressors I know of.

I used a compressed air powered little locomotive in a mine to pull single ore cars along a siding. At 120 PSI We could get about 200 yards then had to stop and refill the tank from the mine's compressed air lines. While that was likely a worst case scenario as a mining engineer I know that air conpression is horribly inefficient. Expansion can't be too much better. I checked out the aircar site and several places there were out of order.

Give me one of the bikes with a tiny jet engine instead.

Compressing air should be quite inefficient. As you raise the pressure of a gas, it's temperature (in kelvin) increases. This heat will be dissipated to the environment and represents a direct energy loss in the system.

It's better to power a bike by the crank rather than the wheels. With hub motors, to go faster means speeding up the motor which takes more energy. If the crank is powered you merely shift to a higher gear, the engine speed doesn't change. That's the principle behind the Stokemonkey.
I would think that an air motor such as those used on pneumatic tools and an air tank would be a lot simpler than an electric motor, batteries, and a controller. It would certainly be a lot lighter.

The problem with the crank, is that you need something else to recover power, there is another option though, if you take a hub based gear system, like a Nexus, you could add the motor before the gear system, so effectively the motor is geared, just like the crank is, and use the motor as a rear brake, with the front brake used for the final stop and hold. This would probably be best implemented in a commuter or touring bike, rather then a racing bike or a MTB. It does require a hub that is built for the purpose though.

I used a compressed air powered little locomotive in a mine to pull single ore cars along a siding. At 120 PSI We could get about 200 yards then had to stop and refill the tank from the mine's compressed air lines. While that was likely a worst case scenario as a mining engineer I know that air conpression is horribly inefficient. Expansion can't be too much better. I checked out the aircar site and several places there were out of order.

Give me one of the bikes with a tiny jet engine instead.
The air in The Air Car is stored at 4500 psi. How much does that locomotive and ore car full of ore weigh?
MDI just signed a deal with Tata, India's largest carmaker. The news was recently on the enviornmental websites.

I hate when they say zero emission in this type of situation. It is just like hydrogen, just a carrier of energy. Where the hell do people think hydrogen, compressed air, or chemical gradients in a battery come from. Right now they mostly come from fossil fuel burning power plants.


Do people think? As in, at all?

I hate when they say zero emission in this type of situation. It is just like hydrogen, just a carrier of energy. Where the hell do people think hydrogen, compressed air, or chemical gradients in a battery come from. Right now they mostly come from fossil fuel burning power plants.


Do people think? As in, at all?

Using your logic, a bicycle is not a zero-emission device wither. The energy used to propel the bike comes from food that was most likely was grown on a commercial farm using diesel and gasoline powered machinery to grow the crops, transport the harvest, process and package the food, and deliver it to your neighborhood grocery.

Food is one of the most inefficient methods of transporting energy in terms of energy required to produce and deliver a given number of calories. It takes about 15% additional energy to produce, refine, and transport oil-based energy sources to the end user. But food requires something like 80% additional energy.

Electric, hydrogen, air, etc. powered vehicles can all get their energy via electric power plants. These can be made using low emission technologies like hydro, wind, nuclear, and solar. But human powered devices must be powered by food. And since it is not practical for each person in large cities to grow his own food, that energy source will continue to require oil-based energy until such time that electric tractors are developed.

Do people think? As in, at all?

my thinkings, let me show them.

Certain renewables, wind for instance, are variable, and often located far away from where the electricity would be used, which means a really big investment in power transmission lines is needed. Since energy, i.e. electricity, can't be created or destroyed, guess what we can do with it if it's not suitable for use as electricity in the grid all of the time (periodic nature of electricity consumption)? Change it's form. Into... Hydrogen. Now, from what I've gathered, hydrogen storage isn't exactly the best. It evaporates off, and all sorts of crap, we don't have the proper infrastructure. Otoh, we can make methanol from hydrogen, that would be a carbon dioxide neutral fuel. We have the infrastructure in place to use it already, and while the overall efficiency is bad at ~20-40%, we have so much wind energy available that this isn't much of a problem. It's better to use energy at some reduced efficiency than to not use it at all. Another benefit would be it's high octane rating as a fuel, which would allow manufacturers to build more efficient engines.

Imo, you might want to focus more of your attention on the processes used to get energy. And your spite on the humans that run these processes in a poor, or irresponsible manner. Instead of simply blacklisting a given process.