Air compressed (pressurised) in a container can be used as a power source. Applications for compressed air include pneumatic tools such as jackhammers, drills, spray-painters, and processes like mineral sorting, automotive manufacturing and water treatment. Around 10% of all electricity generated in Australia is expended on the production of compressed air.
An advantage of pneumatic tools is that several can be run in a system without each needing its own internal motor. This means the tools can be more compact, lighter and easier to use in confined spaces.
The cost of compressed air is (or has been) many times that of other energy transfer methods. Although air itself is a clean resource in endless supply, it requires electrical energy to compress it for industrial use.
As much as 30% of a site’s electricity use can be consumed by this process. Also, up to 90% of the energy used to compress air can be wasted in the process. On top of this, up to 50% of compressed air is lost in leakages, even in new equipment.
However, recent innovations in energy storage have led to methods of capturing the heat energy previously wasted in air compression. Additionally, compressing air can be an almost entirely clean process when the initial energy is obtained from the wind or sun.
Where compressed air equipment is required, optimisation of its efficiency is essential.
Compressed air energy storage (CAES) is a grid-scale method of storing energy that’s generated at one time then contained for later use. ‘Excess’ energy generated at off-peak can be and stored as compressed air and then converted back into electricity for supply during peak demand. An entire CAES system can consist of little more than steel, water and air—powered by wind or sun. A CAES station is therefore a renewable energy plant.
The feasibility of small-scale CAES for home or building use is being investigated.
Ways to save
Maintain correct settings
Ensure that air compression equipment is correctly calibrated, adequate and appropriate to task.
Find leaks and fix them
Leakage rates can be as high as 50% in poorly maintained compressed air systems. Leaks can be detected with ultrasonic equipment or, more simply, by applying soapy water to exterior pipework and looking for air bubbles.
Limit the need for compressed air applications, and use the minimum pressure required for a task. Switch off when not in use, because an idling compressor uses 40% of its full load.
Use a variable-speed compressor
Modern variable-speed compressors adjust to meet demand, unlike older constant-speed models. One variable-speed 100 hp compressor is much more efficient than four fixed-speed 25 hp units. It also enables easier control. Variable-speed drives, however, can be more sensitive and require more maintenance.
Use more energy-efficient technologies than compressed air, such as electric motors rather than air-powered motors. Electrical power-tools, in many cases, are more cost-effective alternatives.