Where compressed-air energy is lost and how to calculate the savings potential

High system pressure levels, pressure reducers, and unused residual pressure energy cause unnecessary energy expenditure in many applications. The Celeroton Energy Calculator makes it easy to calculate savings potential.

Compressed air is indispensable in many industrial processes. It is usually generated centrally at a higher pressure level than the individual consumers actually require. Pressure reducers reduce the pressure at the point of use, but the compression work previously invested is lost in the process. Pressure losses, leaks, and venting compressed air after a process also represent unused energy that simply dissipates.

The Celeroton Energy Calculator makes it easy to calculate the potential energy and cost savings for various compressed-air application cases. It can be used free of charge, without registration, and provides a result directly. The Energy Calculator thus supports you in an initial technical and economic assessment.

Four application cases in the Energy Calculator

The Energy Calculator maps four typical initial situations:

• Single pressure level system: The entire system operates at one pressure level. As a rule, at the highest pressure required by one of the connected processes. However, most connected processes often require a significantly lower pressure. Here, a differentiated supply can help avoid unnecessarily high pressure levels.

• High- and low-pressure network: A high- and a low-pressure network are already in place. The application case considers the supply of consumers with different pressure requirements and the question of how the pressure levels can be distributed efficiently. Always with the objective of compressing as little air unnecessarily as possible.

• Low-pressure air: A conventional blower generates low-pressure air. The Energy Calculator helps estimate the potential of switching to generation with an efficient turbo compressor.

• High pressure after process: A process discharges compressed air that still has a substantial pressure level. Rather than venting this air unused, it is possible to examine whether the energy it contains can be used further.

After selecting the application case, the most important specifications are entered. Depending on the selected case, these include the various pressure levels, the volumetric flow rate, annual operating hours, and electricity costs. The Energy Calculator then calculates the potential energy and cost savings.

Approaches for a more efficient compressed-air supply

The four examples address recurring challenges in industrial compressed-air systems. A central approach is to adjust the generated pressure level to the actual requirements of the respective application.

In a compressed-air network with several pressure levels, all consumers with a higher pressure requirement than the lower-pressure network are usually supplied from the high-pressure network via pressure reducers. As a result, the entire air volume of these consumers is over-compressed. A more efficient alternative is to supply consumers in the pressure range between the pressure levels from the lower pressure and raise the pressure decentrally to the required level with booster compressors.

Residual pressure can also be used in processes with a limited pressure loss. A typical example is blow-moulding processes. In these processes, the required blowing pressure is, for example, between 4 and 40 bar. The blowing air, which presses the plastic or glass into the mould, still has considerable pressure and thus energy after the blowing process, but is often vented. A booster compressor can raise the pressure again slightly and feed the compressed air back into the system.

Local low-pressure supply is also particularly relevant. Many machines are connected to a compressed-air network typically at 6 to 8 barg, but require only a much lower process pressure. Almost irrespective of machine type—from modern grinding machines to packaging machines—such consumers are repeatedly encountered: they have a central connection at 6–8 bar, but often have their highest air consumption at <1 bar. A local supply of low-pressure processes at the actually required pressure can reduce immense energy losses caused by pressure reduction, leaks, and pressure losses in the network.

A practical example demonstrates the potential: At 6,000 operating hours per year, electricity costs of CHF 0.15/kWh, a network pressure of 7.5 barg and a process pressure of 1 barg, a central compressed-air supply requires 195 MWh per year. By comparison, a decentralised solution with a turbo compressor requires 63 MWh per year. In this example, this corresponds to energy savings and thus a reduction in operating costs of 68%. A cost-savings potential of 34%. Annual savings of CHF 6,500 in the case shown result in a return on investment of less than three years.

At process pressures below 1 barg, energy consumption can decrease by more than 80% compared with supply from a 7.5-barg network.

Calculate the savings potential for your application

The Energy Calculator provides initial guidance for typical compressed-air applications. Actual savings, however, depend on the respective operating conditions—such as pressure level, volumetric flow rate, operating time, existing infrastructure and electricity price.

If your application case is not covered by the Energy Calculator, we will be happy to calculate the potential specifically for your application. Contact us at moc.notorelec@ofni or by phone at +41 44 250 52 20.