Air compressors present a variety of opportunities for saving energy, from leak reduction and air intake improvements, to maintenance, monitoring, specification and design, according to guidance from the Carbon Trust.
Of the total energy supplied to a compressor, as little as 8 to 10 percent is converted to usable energy at point of use, making it a very inefficient and expensive way of transferring energy. The Carbon Trust says businesses in the U.K. could save up to £110 million a year ($173 million) by taking simple actions, at little or no cost, to improve compressed air systems and processes.
The trust says that compressed air can be up to 30 percent of a facility’s energy use, with frequent users of compressed air including companies in aircraft and auto manufacturing, cement, ceramics, chemicals, electronics, engineering, food and drink, foundries, glass, insulation materials, minerals, paper and board, pharmaceuticals, power generation, rubber and plastics, steel, textiles, tobacco and water treatment.
Some of the opportunities for improvement are:
Usage and housekeeping
Switch off compressors when not needed, and ask if compressed air needs to be used at all. For example, compressed air is often used in pick-and-place operations, generating a vacuum to pick up an item and move it from one place to another. This can be accomplished with less energy using a vacuum pump.
Also ask how the compressed air is delivered. Venturi-type nozzles are usually more efficient than blow guns, as well as quieter and safer.
For most sites, this is the single most important energy-efficiency action they can take. Well-maintained systems will lose about five to 10 percent of energy to leakage, compared to 50 percent or more in the worst-managed systems. Leaks can be detected from hissing or rattling noises (when the compressor is running without tools or equipment), by applying soapy water and seeing where it bubbles, or using ultrasonic leak detection equipment.
Improving intake air quality, generation and control
Intake air quality can be improved by ducting intake air from a suitable location, clear from exhaust ducts, free from obstructions and protected from the elements. Intake air should be as close to the outside air temperature as possible. Check the condition of the air intake filters – make sure they are not dirty or blocked.
Generation and control can be improved by matching control methods to demand requirements, using automatic shutdown control, controlling multiple compressors with an electronic sequential controller instead of a cascade pressure control, and integrating system controls into plant control or building management systems.
Companies shoud check air quality and pressure dew point. If only some processes need the air to be treated to a high level, consider treating all the air to a minimum specification, and then the needed amount to the higher level.
Air receivers and distribution systems
Companies should minimize pressure fluctuations, and identify opportunities to capture and re-use waste heat.
Planned maintenance and system checks should be carried out in accordance with manufacturer recommendations. Low-cost maintenance activities can save up to 10 percent of energy costs, according to tests carried out on over 300 typical compressors.
This should include monitoring of energy use, recording this use against production levels, and plotting the air volume produced against energy consumed.
Specification and design
Monitor demand before investing in new equipment, and consider the total cost of ownership. A variety of service contracts are available, including one, three, five or even 10 year-terms. Make sure the manufacturer provides information on energy consumption for full and no load, and for the total package power into the compressor, not just shaft power.