What is Compressed Air?

Compressed air is all around us, from the air in a balloon to pumping up tires on your bicycle. In this article we will explain what compressed air is and how it is created. Whether you know it or not, compressed air is involved in every aspect of our lives, from the balloons at your birthday party to the air in the tires of our cars and bicycles. It was probably even used when making the phone, tablet or computer you’re viewing this on.

The main ingredient of compressed air is, as you might have already guessed, air. Air is a gas mixture, which means it consists of many gases. Primarily these are nitrogen (78%) and oxygen (21%). It consists of different air molecules that each have a certain amount of kinetic energy.

The temperature of the air is directly proportional to the mean kinetic energy of these molecules. This means that the air temperature will be high if the mean kinetic energy is large (and the air molecules move faster). The temperature will be low when the kinetic energy is small.

Compressing the air makes the molecules move more rapidly, which increases the temperature. This phenomenon is called “heat of compression”. Compressing air is literally to force it into a smaller space and as a result bringing the molecules closer to each other. The energy that gets released when doing this is equal to the energy required to force the air into the smaller space. In other words it stores the energy for future use.

Let’s take a balloon for example. By inflating a balloon, air gets forced into a smaller volume. The energy contained in the compressed air within the balloon is equal to the energy needed to inflate it. When we open the balloon and the air gets released, it dissipates this energy and causes it to fly away. This is also the main principle of a positive displacement compressor.

Another example: If we take a look at our earth’s surface and its atmosphere, we can interpret it as a sea of air. The higher you are in this ocean, the lower the pressure would be. The lower you are (closer to sea level), the higher the pressure, because there will be more air pressing down on you. In other words, the air is more compressed at and below sea level than it is at the top of New Zealand's tallest mountain, Mt Cook!

Compressed air is an excellent medium for storing and transmitting energy. It’s flexible, versatile and relatively safe compared to other methods for storing energy, like batteries and steam. Batteries are bulky and have a limited charge life. Steam, on the other hand, is not cost effective nor user friendly (it gets extremely hot). When comparing compressed air with electricity however, electricity is more cost efficient. If this is true, why use compressed air? Watch this video, and read on to find out why you should use compressed air:

Why do we use compressed air?

One of the most important reasons for using air compression instead of electricity is safety. In applications where equipment is overloaded, electrical equipment poses a safety hazard. Electrical shocks or fire may occur damaging property or injuring personnel. Compressed air and pneumatic tools can be used under many conditions, such as on wet floors or in high humidity areas.

Secondly, compressed air is more flexible. It is easier to use in remote areas like mines and construction sites. Air tools run cooler and have the advantage of variable speed and torque. Consider rock drills or similar impact type equipment. It would be nearly impossible to develop an equivalent force with electricity, especially in remote areas.

Tools powered by compressed air are also more lightweight. They can be manufactured with materials that make them lightweight and more ergonomic; thus balancing cost of air with cost of labor due to reduced worker fatigue when using these lighter tools.

Finally there’s the cost. The cost equivalent of compressed air can be as high as 7 to 8 times that of electricity. However, the equipment designed to use compressed air is lower in cost. Fewer parts are used due to the simplicity of design. Also, pneumatic tools are usually rugged and last longer in production environments.

Did you know compressed air is viewed as the fourth utility. Of course, we all probably use the first three in our daily lives: water, electricity and gas. However, due to its omnipresent use, compressed air is viewed as the fourth utility for small businesses and big enterprises alike.

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