Light Industrial
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Air Compressors

Estimated Savings

Compressed air is the fourth utility. In a typical manufacturing facility, compressed air accounts for about 15% to 25% of the total energy used. Most systems employ multiple compressors. It runs tools and machinery, provides power for material handling, and ensures clean, breathing air in contaminated environments.

A plantís expense for compressed air is often thought of only in terms of cost of equipment. Energy cost, however, represents as much as 65% of the total expense in producing compressed air.

Following are some rules of thumb that can be used to reduce your energy consumption:
  1. Repair air leaks. The American Council for an Energy Efficient Economy has published reports which states that 15% of the energy used to generate compressed air is lost in leaks. Other estimates range from 15% to 25% and higher.
  2. Reduce the operating pressure. Most system operate at a pressure much higher than required to operate the air equipment. When the compressor produces 100PSI air, and the demand remains constant, every 2PSI of pressure increase will also increase its energy consumption by approximately 1 percent.
  3. Replace undersized air piping to reduce pressure lost.
  4. Consider heat recovery. During operation, compressors generate a large amount of heat which can be used for other purposes in the plant. A well designed heat recovery system can recover over 50 percent of the compression heat energy. The waste heat has many applications including process use, space heating, and preheating boiler feedwater. A 50 horsepower air compressor rejects approximately 126,000 Btu per Hour.
  5. Pipe in outside air for the compressors. Most mechanical rooms are hot. Cooler air increases the efficient of the air compressor.
  6. Use sequencing controls for multiple compressor installations. Rotary screw compressors operate most efficient at full load. When operating more than one air compressor, sequencing control system should be added to optimize the operation of the air compressors. Savings of 10 to 20% and over can be obtained by installing the sequencing controls.
  7. Use energy-efficient motors. When purchasing a new air compressor specify the motor to be energy efficient or consider purchasing an air compressor with variable speed drives that are now on the market.

Estimated savings
Leaks can add up to create significant amounts of energy waste. Lower pressure will result in lower leakage from existing holes, as detailed below. The following costs were calculated assuming 8000 operating hours/year, and an efficient $.15/1000 cubic feet of air were used to compute the costs shown.

Leak Size Leak Rate 110 psi Cost Leak Size 100 psi Cost
1/16" 4.3 cfm $312 3.9 cfm $286
1/8" 17.4 cfm $1,249 15.9 cfm $1,142
1/4" 69.4 cfm $4,997 63.5 cfm $4,569
3/8" 156.2 cfm $11,243 142.8 cfm $10,281
1/2" 277.6 cfm $19,988 253.9 cfm $18,277
 

   
 
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