Behold the CityCAT air car, powered by compressed air.

Michael Pardee wrote:

> In a time when efficiency is seen as more important than ever, the inherent
> inefficiency of compressed air makes this a tough sell.

A *non-sell* for general road use.

Graham

"Michael Pardee" > wrote in message
.. .
> >
> >
> The physics of the technology pretty much cap the energy storage
efficiency
> at 50% max, and it's going to be hard to break the 35% barrier. The ratio
of
> specific heats problem (the same thing that makes a basketball "deader"
than
> a superball) won't go away as long as this universe is in existence.
> Adaptive air motors are possible but always tricky. Using only the "top
> half" of the pressure charge means hauling around a lot of dead weight.
>
> Batteries don't have to be bad for the environment at all. The heavy
metals
> that are most to blame for batteries' bad rep are completely recyclable.
The
> larger batteries get the less likely they will escape the recycling
stream;
> even standard car batteries are rarely dumped any more.
>
> Air powered cars have been around longer than electric cars - there are
> reasons they haven't caught on. In a time when efficiency is seen as more
> important than ever, the inherent inefficiency of compressed air makes
this
> a tough sell.
>
> Mike
>
>

All true, but batteries are every bit as heavy as air tanks, in their
current state of development. Air is as good an alternative source of energy
as any other, and it's the combination of various technologies that will
save us, not one specific one. Air is perfectly clean and endlessly
renewable, so efficiency can take a back seat till better options come
along. Lord knows it's better than alcohol. It's "alternative thinking"
that's important, not necessarily relative efficiency. In other words, don't
shoot it down cause it's not perfect. What's most important at this point in
time is that it's CLEAN. Unless you're off the grid on solar and wind,
electricity is anything BUT clean.

"Dan G" > wrote in message
. ..
>
>
> All true, but batteries are every bit as heavy as air tanks, in their
> current state of development. Air is as good an alternative source of
> energy
> as any other, and it's the combination of various technologies that will
> save us, not one specific one. Air is perfectly clean and endlessly
> renewable, so efficiency can take a back seat till better options come
> along. Lord knows it's better than alcohol. It's "alternative thinking"
> that's important, not necessarily relative efficiency. In other words,
> don't
> shoot it down cause it's not perfect. What's most important at this point
> in
> time is that it's CLEAN. Unless you're off the grid on solar and wind,
> electricity is anything BUT clean.
>
>
>
Compressed air is only a storage medium, just as batteries, hydrogen or
flywheels are. According to the Wikipedia entry on energy density,
http://en.wikipedia.org/wiki/Energy_density, it competes poorly in that
category. Even excluding the weight of the tanks, just the weight of the air
itself, it weighs 2-3 times as much as the equivalent capacity of Li-Ion
batteries and has at least 7 times the loss. (The practical recovery
efficiency of compressed air is given as 64%, which is the efficiency if the
driven device is 100% efficient over the entire range of pressure. This
requires the air pressure used not drop much below the 20 bar pressure they
cite; darned Second Law of Thermodynamics!) It fares even worse in energy
density against compressed hydrogen powering a fuel cell, which offers about
250 times the energy density of compressed air.

Mike

Michael Pardee said the following on 5/26/2007 8:23 PM:
> "Dan G" > wrote in message
> . ..
>>
>> All true, but batteries are every bit as heavy as air tanks, in their
>> current state of development. Air is as good an alternative source of
>> energy
>> as any other, and it's the combination of various technologies that will
>> save us, not one specific one. Air is perfectly clean and endlessly
>> renewable, so efficiency can take a back seat till better options come
>> along. Lord knows it's better than alcohol. It's "alternative thinking"
>> that's important, not necessarily relative efficiency. In other words,
>> don't
>> shoot it down cause it's not perfect. What's most important at this point
>> in
>> time is that it's CLEAN. Unless you're off the grid on solar and wind,
>> electricity is anything BUT clean.
>>
>>
>>
> Compressed air is only a storage medium, just as batteries, hydrogen or
> flywheels are. According to the Wikipedia entry on energy density,
> http://en.wikipedia.org/wiki/Energy_density, it competes poorly in that
> category. Even excluding the weight of the tanks, just the weight of the air
> itself, it weighs 2-3 times as much as the equivalent capacity of Li-Ion
> batteries and has at least 7 times the loss. (The practical recovery
> efficiency of compressed air is given as 64%, which is the efficiency if the
> driven device is 100% efficient over the entire range of pressure. This
> requires the air pressure used not drop much below the 20 bar pressure they
> cite; darned Second Law of Thermodynamics!) It fares even worse in energy
> density against compressed hydrogen powering a fuel cell, which offers about
> 250 times the energy density of compressed air.
>
> Mike
>
>
>
Entropy just ain't what it used to be.

"Don in San Antonio" > wrote in message
...
> Entropy just ain't what it used to be.
>

But we have more of it than ever!

Back in the day they called the cure-all products, 'Snake oil.' If somebody
could actually come up with an alternated fuel that would not cost any more
to produce, deliver, sell, meet all the governmeant regulations as good as
crude oil, that was cleaner, they would be doing so. If any manufacture
could build a vehicle that would be as powerful, as roomy and salable, meet
all the governmeant regulations, that would get 20 miles more per gallon
they would be doing so. Nobody could stop them, and in either example they
would make that person billions of dollars.

mike


"Michael Pardee" > wrote in message
.. .
> "Dan G" > wrote in message
> . ..
>>
>>
>> All true, but batteries are every bit as heavy as air tanks, in their
>> current state of development. Air is as good an alternative source of
>> energy
>> as any other, and it's the combination of various technologies that will
>> save us, not one specific one. Air is perfectly clean and endlessly
>> renewable, so efficiency can take a back seat till better options come
>> along. Lord knows it's better than alcohol. It's "alternative thinking"
>> that's important, not necessarily relative efficiency. In other words,
>> don't
>> shoot it down cause it's not perfect. What's most important at this point
>> in
>> time is that it's CLEAN. Unless you're off the grid on solar and wind,
>> electricity is anything BUT clean.
>>
>>
>>
> Compressed air is only a storage medium, just as batteries, hydrogen or
> flywheels are. According to the Wikipedia entry on energy density,
> http://en.wikipedia.org/wiki/Energy_density, it competes poorly in that
> category. Even excluding the weight of the tanks, just the weight of the
> air itself, it weighs 2-3 times as much as the equivalent capacity of
> Li-Ion batteries and has at least 7 times the loss. (The practical
> recovery efficiency of compressed air is given as 64%, which is the
> efficiency if the driven device is 100% efficient over the entire range of
> pressure. This requires the air pressure used not drop much below the 20
> bar pressure they cite; darned Second Law of Thermodynamics!) It fares
> even worse in energy density against compressed hydrogen powering a fuel
> cell, which offers about 250 times the energy density of compressed air.
>
> Mike
>
>

Dan G wrote:
> "Michael Pardee" > wrote in message
> .. .
>>>
>> The physics of the technology pretty much cap the energy storage
> efficiency
>> at 50% max, and it's going to be hard to break the 35% barrier. The ratio
> of
>> specific heats problem (the same thing that makes a basketball "deader"
> than
>> a superball) won't go away as long as this universe is in existence.
>> Adaptive air motors are possible but always tricky. Using only the "top
>> half" of the pressure charge means hauling around a lot of dead weight.
>>
>> Batteries don't have to be bad for the environment at all. The heavy
> metals
>> that are most to blame for batteries' bad rep are completely recyclable.
> The
>> larger batteries get the less likely they will escape the recycling
> stream;
>> even standard car batteries are rarely dumped any more.
>>
>> Air powered cars have been around longer than electric cars - there are
>> reasons they haven't caught on. In a time when efficiency is seen as more
>> important than ever, the inherent inefficiency of compressed air makes
> this
>> a tough sell.
>>
>> Mike
>>
>>
>
> All true, but batteries are every bit as heavy as air tanks, in their
> current state of development.

Air tanks are pretty well developed. They are not complicated. They just
have a lot of space and a valve.

> Air is as good an alternative source of energy
> as any other, and it's the combination of various technologies that will
> save us, not one specific one. Air is perfectly clean and endlessly
> renewable, so efficiency can take a back seat till better options come
> along. Lord knows it's better than alcohol.

Wrong. Air is not a source of energy. The air has to be compressed. That
takes energy, whether it's electricity, gasoline or someone compressing
the air with a hand pump.

> It's "alternative thinking"
> that's important, not necessarily relative efficiency. In other words, don't
> shoot it down cause it's not perfect. What's most important at this point in
> time is that it's CLEAN. Unless you're off the grid on solar and wind,
> electricity is anything BUT clean.

yet this is not more than a storage form of electricity. It is really no
different than if you charge a battery in the car. Air doesn't compress
itself.

Jeff

Michael Pardee wrote:
> "Dan G" > wrote in message
> . ..
>>
>> All true, but batteries are every bit as heavy as air tanks, in their
>> current state of development. Air is as good an alternative source of
>> energy
>> as any other, and it's the combination of various technologies that will
>> save us, not one specific one. Air is perfectly clean and endlessly
>> renewable, so efficiency can take a back seat till better options come
>> along. Lord knows it's better than alcohol. It's "alternative thinking"
>> that's important, not necessarily relative efficiency. In other words,
>> don't
>> shoot it down cause it's not perfect. What's most important at this point
>> in
>> time is that it's CLEAN. Unless you're off the grid on solar and wind,
>> electricity is anything BUT clean.
>>
>>
>>
> Compressed air is only a storage medium, just as batteries, hydrogen or
> flywheels are. According to the Wikipedia entry on energy density,
> http://en.wikipedia.org/wiki/Energy_density, it competes poorly in that
> category. Even excluding the weight of the tanks, just the weight of the air
> itself, it weighs 2-3 times as much as the equivalent capacity of Li-Ion
> batteries and has at least 7 times the loss. (The practical recovery
> efficiency of compressed air is given as 64%, which is the efficiency if the
> driven device is 100% efficient over the entire range of pressure. This
> requires the air pressure used not drop much below the 20 bar pressure they
> cite; darned Second Law of Thermodynamics!) It fares even worse in energy
> density against compressed hydrogen powering a fuel cell, which offers about
> 250 times the energy density of compressed air.
>
> Mike

I could see compressed air powering lawnmowers, go carts, golf carts,
and fork lifts. In theory, you could have quick-connect bottles, making
it all practical (the bottles could be refilled by a compressor). That
would certainly be cleaner than using small internal combustion engines.

Other than those sorts of uses, I don't see many possible markets for
compressed air.

Jeff

As long as they are still viable, it doesn't matter that they're less
efficient than EV's, because the environmental impact is far less than fuel
burning cars, and even EV's. I personally think that if it is a viable
technology, then it is far more attractive than EV's even if they require
more refills. Although EV's are potentially a safer alternative to fuel
burning cars they still have a large environmental impact. The problem is
that it is far down the road and not as visible to the public. Has anyone
ever thought of what kind of negative impact the manufacturing of fuel cells
has, or what the impact of disposal will have? What will be done with all
the chemicals? I think EV's are a short term solution, but in the long term
it's a dangerous technology.


"Eeyore" > wrote in message
...
>
>
> Dan G wrote:
>
>> Nevertheless, this type of thinking is what will save us from fossil
>> fuels.
>
> No it won't.
>
> They are *less* efficient that EVs, so need MORE energy to keep them
> running.
>
>
>> The compressed air cars are doing pretty well,
>
> Where exactly ? Except in your fantasies ?
>
>
>> and if you use solar power to charge them up, it's free energy.
>
> Damn you're an ignorant prick of the first order. Use the same cutesy
> 'solar
> energy' in EVs and you'll easily go *TWICE* as far - probably more since
> EVs can
> reclaim energy by regenerative braking.
>
> Graham
>

"Jeremy" > wrote in message
news:FG37i.237824$aG1.12783@pd7urf3no...
> As long as they are still viable, it doesn't matter that they're less
> efficient than EV's, because the environmental impact is far less than
> fuel burning cars, and even EV's. I personally think that if it is a
> viable technology, then it is far more attractive than EV's even if they
> require more refills. Although EV's are potentially a safer alternative
> to fuel burning cars they still have a large environmental impact. The
> problem is that it is far down the road and not as visible to the public.
> Has anyone ever thought of what kind of negative impact the manufacturing
> of fuel cells has, or what the impact of disposal will have? What will be
> done with all the chemicals? I think EV's are a short term solution, but
> in the long term it's a dangerous technology.
>
>

I disagree about ignoring the inefficiency. Worse, even a simple requirement
like passenger heat is not presently in TheAirCar design. The manufacturer
claims TheAirCar is quieter than conventional combustion engines (listen to
the low speed demo and you may doubt even that) but admits it lacks the
silence of EVs. EVs have so many advantages and are well enough proven that
competing technologies can't just say, "We can do half that stuff at half
the efficiency!" and expect a following. The manufacturer's promo material
shows lift trucks powered by air, but battery powered lift trucks have been
popular for many decades. The company doesn't even speculate when production
will begin. In the meantime, production EVs have actually been on the road.
Compressed air is way too little, too late.

Do you have any particular reason for concern about battery disposal
(recycling) as currently carried out? In the US we go through roughly a
hundred million lead-acid car and truck batteries every year, and those are
about as toxic as batteries come. I think if it were a problem we'd be
hearing about it.

Mike