Viewpoint: cutting the cost of compressed air

In a bid to cut their production spend, many manufacturers are hunting for new ways to meet energy efficiency and sustainability targets.

Compressed air supply systems can be a big source of wasted energy, especially if they have been in place for some years.

But it is possible to reduce energy costs by as much as 60% through optimisation at both the production and system level.

Compressed air costs can be determined using the sum of fixed and variable costs and using the annual delivery output of the compressor station.

By far, energy charges account for the largest part of these costs, at about 75%.

Real savings

Compressed air costs can be immediately reduced by up to 30% through using a central waste heat recovery system (WHR), with savings based on the heating costs saved.

For example, using a WHR with warm water, up to 72% of the compressor output can be utilised as heat or, in the case of air cooling only, the figure can be as much as 90%.

It is possible to reduce energy costs by as much as 60% through optimisation at both the production and system level

In practice, the costs of compressed air can be determined very accurately by measuring the electricity requirement and the actual delivery rate. However, this varies on the intake conditions and should therefore be measured at the same time as the energy consumption.

To get a more complete picture of consumption, possible leakage costs that may occur in non-productive operation are a fundamental factor in finding potential energy savings.

As a rule of thumb, 20% of the detectable leakages in existing systems account for up to 80% of the avoidable costs.

Hence it is worth rectifying leakages quickly as every leakage fixed saves energy, and hence costs, straight away.

When conducting an integrated analysis, four areas of a compressed air system must be considered:

• Air preparation

As the wasted cost for air preparation is just 1%, we will focus on the other three areas.

• Air generation

In air generation, accurate energy analysis of the compressor station is necessary to create consumption profiles, gather information about the complete system, and implement a leak detection and elimination process.

• Air distribution

During air distribution, the most effective way of reducing costs is through leak detection analysis. Systematic checks and classification of leakage found according to volume can be made alongside all other relevant data, for example, the spare parts required, and estimated repair time.

• Air application

Knowing the compressed air consumption of each machine during the application stage is vital for designing and configuring the compressed air supply and distribution at the system level. Furthermore, if the consumption of each individual system is known, then sizeable deviations from standard consumption act as early warning signs of existing or developing faults.

Additional information should also be collected on compressed air components and pneumatic drives, as well as sizing of components and connecting components.

Tailored approach

There is no one-size-fits-all solution and measures must be defined individually for each plant.

Moreover, the measures should always be reviewed in relation to the total consumption so that the economic efficiency of a particular optimisation measure can be determined.

Once a compressed air system has been optimised and brought up to date, it is important to safeguard its efficiency by conducting regular leak detection, compressed air quality analysis, and maintenance of individual machines.

This can be performed manually or with the assistance of an energy efficiency management system.

• Steve Sands is product manager at industrial control and automation specialist, Festo