Compressed air is an expensive form of energy, since most electricity used for power generation is converted into heat. Further losses downstream make compressed air the #1 utility to focus on when you want to start saving energy in your production plant.
Compressed air – air pressed together as in the tires of your car – is one of the most commonly used forms of energy in production companies, in addition to electricity. As much as 10% of all used industrial electricity is converted into compressed air. Why? For many different reasons in many different industries. Think of manufacturing machines in the paper and printing industry or shaping moulds in the glass and plastics industry. But compressed air is also used to move large volumes of loose products, such as flour, grain and plastic pellets or to sort products like fruit, nuts or rejected produce on conveyor belts. Whatever industry you are in, you will (almost) always need compressed air.
So, going back to this 10% needed compressed air. Recent studies conducted in USA, Australia and Europe, have shown that an astonishing 4.2% of all electricity generated worldwide.
Unfortunately, a lot of compressed air is wasted through leakages, wrong application of compressed air and through inefficient distribution of air through outdated pipes. The loss (or read “savings potential”) of a compressed air system varies from 10% to 50%, depending on the condition of the manufacturing company. Especially in old factories, large spills are often discovered adding up to quite a percentage of the nominal consumption. But also when generating compressed air a lot of energy is lost. When compressing air, most of the input power is converted directly into heat (just think of your bicycle pump which becomes very hot after use), leaving about 20 … 25% usable energy in the compressed air%. Of this 25% a good portion is lost again to pressure losses. Therefore, as a rule of thumb, compressed air is up to 20 times more expensive than electricity.
Energy saving is key to a sustainable society. In industry, compressed air systems should be your number 1 priority, as savings can be very significant (20..50%) and payback periods are usually very short and predictable. A German study [Radgen 2002] showed a typical payback period of just over one year. The same researchers calculated that the savings potential amounts to an average of 32.9%.
What would be the impact on our world if this potential savings could be realized within one year? In the following table we have put the numbers in perspective.
Coal: If we would focus on a 33% reduction of industrial compressed air consumption worldwide, then 55 coal fired power plants of 600 MW could shut down.
Wind: Compressed air savings of 33% would be equal to the power generated by 44,330 2 MW windmills.
Sun: 33% of compressed air savings is equivalent to 1,330 50 MW PV power plants.
Conclusions
Compressed air is a very significant and expensive form of energy, since most electricity used for power generation is converted into heat. In many cases, nothing is done with this heat, leaving the efficiency of a compressed air system at not more than about 20%.
A lot of research into savings has been done globally however, many companies still lack awareness. Unnoticed spills are still a current event on the work floor these days, since compressed air leaks don’t create problems other than a bit of noise.
If we were to put compressed air as an energy source in perspective, it would be clear that compressed air savings could deliver a significant contribution to solving our global energy problem. It would be equivalent to shutting down 55 coal power plants, 44,330 wind turbines (2 megawatt per turbine) or 1,330 PV power plants (50 megawatt per plant). The payback period of energy saving investments in compressed air is generally short and predictable.
