Air Power

Don't know how close you are to Ohio Amish country, but years ago many of the Amish/Plain farms ran households and farm with predominantly air power...on a huge scale. As I remember, some had used train tanker cars as storage tanks, which provided vast volumes under relatively high pressure. I think you are correct...this is a viable long-lived source of power...especially if you have wind or moving water.

 

I think the problem with air power may be the volume of air required... air tools are certainly great and can achieve extremely high rpms (a die grinder for example), but they use a very large amount of air to power them. Air tools will list their cubic feet per minute air requirements.

Volume of a cylindrical tank is piexRxRxH (pie radius squared height). Volume of a 'room' is LxWxH (length width height). How much pressure can a tank hold? Depends on the tank.

My opinion, the best way to get electricity is from the grid... next best would be a diesel generator. Unless you live in a wind tunnel or next to a large waterfall... all the rest of the alternatives are either far too expensive, far too complicated, extremely inefficient or produce relatively tiny amounts of power. No free lunch when it comes to electricity... as it is extremely difficult and costly to produce the amount of energy that we have become accustomed to.

cheers,

 

Here is an interesting article about a compressed air car. It came from MIT's Technology Review:

Air-powered Autos

By John Harney September 19, 2002

Zero-emission driving may be more than hot air.

Guy Negre, an engineer from the little town of Carros,
France, discovered a breath of fresh air, both
literally and figuratively. During his career
designing formula one engines he became familiar with
isotherm dynamics, a process that creates power by
expanding air at an almost constant temperature. Negre
theorized that by heating and expanding super-cooled
compressed air he could power a nonpolluting car. Six
years and four prototypes later, it would appear he?s
done it.

Negre?s company, Motor Development International
(MDI), created what it calls the Compressed Air
Technology (CAT) car by combining a lightweight
automobile body with a new type of small rear-mounted
engine. The 1,500-pound frame is made from aluminum
and fiberglass with four very light, steel-reinforced
thermoplastic air tanks attached to the undercarriage
of the car. The engine measures only one- foot square
and weighs just 70 pounds, but because it propels a
relatively light vehicle, it can run at 55 mph.

Negre, who was interviewed through an interpreter,
explains that, in the tanks, the air is both cooled to
minus 100 degrees Centigrade and compressed to 4,500
pounds per square inch. Then it?s injected into a
small chamber between the tanks and pistons, where
it?s heated up by ambient outside air that forces it
to expand into a larger chamber situated between the
small chamber and the pistons. That heat exchange
between the two chambers, he continues, creates the
propulsion that drives the up-and-down strokes of the
engine?s four pistons. Finally, the air is passed
through carbon filters like those in scuba diving
tanks and expelled as pollutant-free exhaust. The
dynamic is not unlike that of a spring that takes in
energy when it?s compressed and gives it back when it
expands.

The big plusses of the air-powered car, according to
Negre, are super-efficient energy consumption as well
as minimum pollution and maximum affordability. Though
the car seats five, it will go from zero to 50 mph in
seven seconds? certainly adequate acceleration for an
urban vehicle like a taxi. What?s more, with fully
loaded air tanks, it will take passengers about 120
miles at an average of 30 mph?again, about the right
capacity for urban drivers who don?t want to fill up
too often.

Charging the car with air is fairly easy?it takes four
hours using a household electric outlet or three
minutes using special compressed air stations that MDI
sells for about $100,000. Obviously, the vehicle also
drastically reduces pollution?it takes in polluted
outside air, filters it, and expels cleaner air as
exhaust. All that for a price tag of between $10,000
and $14,000.

According to Michael Baltierra, a reporter for ABC
News, ?we tested the car and it ran quite well. The
only major problem that we noticed,? he continues,
?was that it was quite noisy?[but Negre] said this was
something that would be fixed in later models.?
According to Shiva Vencat, vice president of the U.S.
wholly owned subsidiary of MDI, Baltierra tested the
car in June, 2000. At the time, Vencat explains, the
car ?was not a finished product?our engine was
attached to the car but did not have the body shell
all the way around it to muffle the noise.? Since
then, he says they have encased the engine to make it
run more quietly.

 

I'm not sure if a ferro-concrete tank makes a good air container. Concrete is good in compression, NOT TENSION and though would work, not as well as a steel tank. That tankcar is a great idea, as are utilizing those old gas tanks on stilts which are used to gas up rural farmsteads. Put a tank on wheeled trailer and your power goes whereever your vehicle goes.

 

I would think the storage loss would be to great (Hp to drive compressor would be much more than you could get out )as well as the amperage to drive the compressor being to high to be met by most RE sources.
Where would you be getting your energy from?

 

Mennonite friend of mine uses air for everything--even pumping water from deep well. Has air powerd fans in house for cooling his family. Has a "skil saw" that looks normal but has a air hookup and really whizzes. Uses a tank off propane truck for storage and a gas motor to pump up. Has air lines everywhere. FB

 

Compressed air is just a storage system like batteries are. 1 is chemical and the other is mechanical. You loose energy when you charge a battery and recover it, you also loose energy when you compress and decompress air. It depends on which method is more efficient, suitable, and safe enough for your project.

I do not know how many cycles an air tank has but a battery can only handle about 1000 cycles below 80% before it really starts showing it.

-- Tim

 

<Hanging my neck out on the block here>

Large used propane tanks (like the unused one outside my house) might be a good way to store air, too. Of course, they better be in PERFECT condition structurally-- no rust or damage-- and you need to add a couple of drains to the bottom of the tank to get rid of collected water... Anyway, just a thought. Research carefully before attempting!

Darren

 

if you live on a windy ridge like I do, I can see where a few windmills continuously compressing air would be as good or better than electric. electric has electrical gremlins... whats air have? leaks. it cant short out when it gets wet or fry a control ciurcut and leave you powerless.
This is a good thread its given me Ideas... windmills hooked to cast iron compressors... some of em dont even have to run that fast to work.

I bet in the longrun it would be cheaper than electric generation also. An unmolested airline lasts practicly forever, the tools if kept oiled and clean last forever. Ive seen old cast iron air comressor heads from the stone age still being used daily.

no real danger of explosion unless your air pump is super effecinet and goes haywire.

thinking of the tools I have, fans would take very little cfm to keep them moving.

a combo of electric windmills and air compressing windmills would be a pretty neato Idea!

 

I doubt any worry about propane tanks--other that getting the smell out of them. If you ever cut open a 500 gallon you would be suprised at the thickness. About half an inch. I'd hate to see how thick a transport tank would be.

Anyone with a copy of the "Budget" newspaper can find all kinds of air powered stuff advertised in it.

FB

 

If you want free or inexpensive power.....there are about 4 ways.....I mentioned wind and moving water. The third is biodiesel, the ability to get free or inexpensive veggie oil and burn it in a Listeroid or Pedder stationary diesel. See the "otherpower" and "udderpower" websites to view them that's doin. The fourth is the Stirling cycle engine, which will run on any heat source....there are some people working hard on this technology....so if you have anything free that burns...you got power to pump. If I had the brain power of some of the super posters on this site, I would take a serious look at the Stirling. I have experimented with it some, and it is for real....possibly revolutionary for home power production, air or electric.

 

Second website is "utterpower", not "udder". Got my cows and dinosauers crossed...

 

I met a guy in the desert doing the compressed air thing,using a windmill.He powers his whole house on it,but how I dont know,and he didnt want to talk to a stranger(me) much about it.But it can be done,Ive seen his lights going,if he told me truthfully about the compressed air business.
BooBoo

 

zekell,

Your idea is viable. Take a look at: http://airliftech.com/

LP tanks are used a lot by the Amish for pressurized air storage. They are not expensive as a rule.

You can convert gallons to cubic feet by multiplying by 0.13368. So a 1000 gal. LP tank should hold about 133.68 cubic feet.

When you say a tool uses X "cubic feet per minute," at what pressure is this flow rate measured? If it is atmospheric, (at a known temperature), you will have to take that into account when you figure how long a tank will last. Also, your tank is never empty -- it always has at least atmospheric pressure in it.

If you can find out what pressure and temperature at which the flow rate is specified for a tool, post it here. If you also state a range of pressures at which the tool will operate, we can estimate how long the tool may be used as the tank depressurizes from the upper limit to the lower limit.

I hope this helps.

River