What is compressed air?

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Compressed air is used in many sectors and applications. In this article we want to tell you more about the specifics of compressed air. What is ‘air’ and air pressure? And, more importantly: what is compressed air? Why is it an excellent energy source?

What is 'air'?

Seems like a redundant question, no? But do you know the specifics of the air that we all breathe? We’ll explain. 

Life on earth is based on a gas bubble, more commonly known as the atmosphere. It surrounds the globe and makes sure that life is possible since it protects us from the UV-rays of the sun and the airlessness of space. Within the atmosphere air is contained. The air that we all breathe is a mixture of these elements: 

  • Nitrogen (approximately 78%)
  • Oxygen (approximately 21%)
  • Other gases like water vapour, inert gases and unfortunately lots of hydrocarbon pollution.

What is atmospheric pressure?

he earth is subjected to an atmospheric pressure that we call air pressure. This is because air - contrary to what you might believe - has a certain weight. More specifically, air weighs about 1.2 kg/m². The higher you go, the lower the pressure gets. Every 5 km you go upwards, the pressure is halved. That’s why we say that the air gets ‘thinner’ when we’re in an airplane or on a mountain top. 

This atmospheric pressure is relative to the pressure of compressed air, as you will read in the next paragraph.

What is compressed air?

Air compressor

Try and compress water, and you’ll be in for a tough job. Liquids, unlike air, cannot be compressed. In fact, the air is reduced due to an increase in pressure. This results in a new, smaller volume of air. 

Compressors are made specifically to compress air for all kinds of reasons. However, the simplest compressor is a bicycle pump: air is taken in and compressed to a fraction of its original volume. Take that the air is compressed to about ¼ of its original volume: that means that the pressure in the bicycle tire is four times greater than the atmospheric pressure. 

Atmospheric pressure is measured in Pa (Pascal). 1 Pascal is a very small amount of pressure. That’s why the unit kilopascal (kPa) or megapascal (MPa) is used: 1 kilopascal/megapascal corresponds to 1000 Pa. 

Compressed air, however, is seen as overpressure, meaning that it’s a pressure above the standard atmospheric pressure.

The use of compressed air as an energy source

Now you know the answer to ‘What is compressed air?’. But what makes it a good energy source? First of all: the air that you compress is clean. That makes the end product clean as well. It’s also totally harmless. On the other hand, compressed air is versatile: it can be used in production lines, power tools and pistons, move or cool materials. 

You’ll need an external power source to power your compressor. In most cases this is an electric engine. Smaller, DIY compressors sometimes use combustion engines. 

Of course, there is a certain amount of power loss when operating a compressor. This will affect the ultimate power needs of your compressor. 

We’ll give you an example: 

You want to compress air to 700 kPa. This will require about 6.5kW/m³/min of power. Increasing or decreasing the pressure with 100 kPa will result in the same increase or decrease in power requirements.

Any more questions on compressed air and air compressors?

We hope we’ve adequately answered your question: ‘What is compressed air?’. 

We’d be happy to help you with any other questions you may have. Do you perhaps want to know more about our services? Or about which air compressor is ideal for your purposes? Let us know, and we’ll get back to you as soon as possible.

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