Basic overview of air compressor thermodynamics

Energy exists in various forms, including thermal, physical, chemical, radiant (light, etc.), and electrical energy. Thermodynamics is the study of thermal energy, i.e. of the ability to bring about change in a system or to do work.

The First Law of Thermodynamics expresses the principle of energy conservation. It states that energy is neither created or destroyed. From this, it says that the total energy in a closed system is always conserved, thereby remaining constant. It merely changes from one form into another. With this, heat is a form of energy that can be generated from or converted into work.

The Second Law of Thermodynamics states there is a tendency in nature to proceed toward a state of greater molecular disorder. Entropy is a measure of disorder. Solid crystals, the most regularly structured form of matter, have very low entropy values.

Gasses, which are more highly disorganized, have high entropy values. The potential energy of isolated energy systems that is available to perform work decreases with increasing entropy. The Second Law of Thermodynamics states that heat can never of "its own effort" transfer from a lower-temperature region to a higher temperature region.

As explained in this article, thermodynamics relates to energy and how it is transferred. In the context of air compressors, we focus on gas (air) under high pressure levels. Both Boyle's and Charles' gas laws are helpful in understanding how high compression levels and other gasses have an impact.

With this, the concept of thermodynamics is fundamental to understanding how a compressor works. Essentially, air becomes heated through the pressurization process and high air flow rates involved in compression. Often, there's leftover heat in an air compressor, known as heat of compression.

This generated heat can be reused in energy recovery processes. If you recover up to 94% of the total horsepower, your energy savings could be significant. For example, a 400kW compressor with an energy recovery of 90% can save €150,000 per year.

Using hot water as a boiler pre-feed or directly in processes requiring 70-90°C, you can save on energy sources such as natural gas. Placing an energy recovery control unit between the compressor and cooling / heating circuit is an effective way to reduce electricity costs.

Additionally, you'll find many new air compressors are designed with energy recovery pre-installed. Through the power of thermodynamics, there's many possibilities for energy recovery. Since electricity makes up 99% of CO2 emissions, and over 80% of a compressors' lifecycle costs, it's important to take note of this article.

With the above information, we hope you feel confident in choosing the right oil-free or oil-injected air compressor. All our rotary screw models are the most advanced and offer energy saving features.

If you need more information on our air compressors, feel free to get in touch. We're happy to help.