Reducing the Cost of Compressed Air in Industrial Facilities

Compressed air at gage pressures of 550 kPa to 1000 kPa (80 to 150 psig) is commonly used in industrial facilities to perform a wide variety of tasks such as cleaning, operating pneumatic equipment, and even refrigeration. It is often referred to as the fourth utility after electricity, water and natural gas or oil. In production facilities, there is a widespread waste of energy associated with compressed air systems, and a general lack of awareness about the opportunities to conserve energy. This paper is based on our observations during our visits to manufacturing facilities, as well as the similar observations of others during the past several years. A considerable portion of the energy waste associated with compressed air systems can be avoided by following some common sense measures. In this paper we evaluate and quantify the energy losses associated with compressed air systems, and their costs to manufacturers. We also show how to reduce the cost of compressed air in existing facilities by making some modifications with attractive payback periods. Among the measures we investigate to reduce the cost of compressed air are: (1) repairing air leaks, (2) reducing the pressure setting at the compressor outlet if a lower operating pressure is adequate, (3) using a smaller compressor at full load instead of large one at part load, (4) reducing the average air inlet temperature by using outside air (preferably from a shady side of the plant), (5) using the waste heat from the cooling fluid to heat the facility in the winter, (6) using high efficiency motors, (7) turning the compressor off at nighttime and even during lunch brakes, and (8) using an aftercooler to reduce the refrigeration costs in compressed air dryers. We also illustrate the potential savings associated with each measure by using typical realistic examples.