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Air Compression
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Question:
Hello my name is ricky ristic Im interested in
producing the electricity from wind,unfortunately there is no wind in the summer time so
I would like to learn more about air storage under pressure.what is
highest pressure that can be stored?what kind of compressor could be used
what power would i get when air is difused where to get more info on
the subject.thank you
Replies:
I do not know if you want to produce electricity or do a demonstration.
If you want to produce electricity, this would be a very expensive method
because it takes electricity to compress the gas in the first place. You
may end up getting 1 unit of electricity for every 10-20 put in.
But if you want to do a demonstration, you can visit a hobby shop and get a
small compressor (or get one from an auto part company, used to inflate car
tires). These produce some 50 psi pressure. You can also get a compressed
air cylinder; these can be highly pressurized, depending on the capsule,
size, rating, etc.
You need to be very careful in working with compressed air, and have some
training in handling these.
Depending on your goal, you can even use a fan to run your wind mill.
As far as power need and other engineering calculations, you need to do
some study. The answer depends on many parameters, and some have to be
experimentally established.
So, I suggest you go to a library or bookstore and find some books on wind
power and how to harness it. You can also take a related course in a local
college, or join a club of enthusiasts. In any case, it will both fun and
educational, and please keep an eye on safety issues along the way.
Good Luck.
Dr. Ali Khounsary
The principle concept for using wind is that you take the kinetic energy
(energy due to motion) of the wind and turn it into potential energy (energy
due to position). This potential energy you have created is electrical
energy usually stored in a battery, or you have your appliances plugged
directly into them.
Now, if you want to store air under pressure, you have to put energy into
the air to compress it. That is you have to restrict a flow of air into a
system to create pressure and turn the kinetic energy of flow into potential
energy of compressed air. If you wanted to generate energy from a windmill
that uses just wind, you are extracting energy out of the air and that is
fine. However, if you want to generate energy from compressed air, you
first must put energy into the air (pressurize it) to get energy out of it
by flowing the air through a windmill. Due to the inefficiencies in
compressors, losses due to friction, inefficiencies in tubing, pressure
losses through fittings, etc., you will never be able to get more energy out
than you put in. In fact you have to put more energy into a system in order
to compensate for such losses.
The way you are planning on compressing the air to use it for a windmill is
like this:
you must put energy in to get energy out. you have energy losses due to
system inefficiencies, so you will always have to put more energy in to get
energy out.
With a windmill using natural wind, you are extracting the energy that
already exists within the wind, so you do not have to put energy in to get
energy out.
As for the question on compressors and storage, there are systems out there
that use anywhere from 120 psi up to 10,000 psi of air. Storage is not
really a problem because you can always pay more for a stronger holding
tank. The compressors that are usually used are reciprocating piston driven
systems.
As for information, go to your local library to look for info on Fluid power
systems. Look for information on Boyle's law and Charles' law to get a good
idea of how gasses behave under pressure.
good luck.
c. Murphy
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Update: June 2012
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