- The data sheets made available by the Compressed Air and Gas Institute (CAGI), in addition to resources from Compressed Air Challenge, can make a real difference in helping you choose a compressor.
- There is now a wealth of information about compressor and air dryer energy consumption available within the CAGI Compressor Data Sheets published by participating manufacturers.
It’s probably been years since you’ve even thought about buying a new air compressor, but now your old unit is broken, the boss is howling, and you need to make a decision. But there are so many choices. How do you decide the best one? The data sheets made available by the Compressed Air and Gas Institute (CAGI), in addition to resources from Compressed Air Challenge, can make a real difference in helping you choose.
Too often, the purchasing decision comes down to price. The difference between various compressor brands and models may be only a few hundred dollars, making the cheapest machine the obvious choice to the purchasing department. But what about operating costs?
At $0.10/kWh with a five-day, two-shift operation of about 4,200 hrs/year, a typical 100 hp compressor would require about $37,000 in annual electrical costs. Over a 10-year period, these costs can add up to about 76% of the total lifecycle cost of the air compressor with the purchase price representing only 12% (Figure 1). Even a 5% change in operating efficiency can equal an $18,500 difference over 10 years.
Figure 1. Over 10 years, the operating costs of an air compressor is mostly energy.
Data sheets can help
Figure 2. Typical CAGI Data sheet for a fixed speed, lubricated screw compressor.
When making decisions about energy efficiency, we need some accurate information to plug into power cost formulas. In past years, there has been a jumble of information based on a variety of test conditions. Fortunately, there is now a wealth of information about compressor and air dryer energy consumption available within the CAGI Compressor Data Sheets published by participating manufacturers.
Figure 2 shows an example data sheet for a selected 100-hp, 125-psi, air-cooled, fixed-speed, lubricated rotary screw air compressor. Using it and others you can make and compare cost projections on the electrical needs of fully loaded operation between different makes and models of compressors Table 1 shows a summary of comparisons of other compressors, including more efficient compressors from the same companies (shown as Opt 2).You can see the numbers vary, but the common ground is the specific power number. Specific power is like a gas mileage rating for compressors and shows the ratio of the total package power input kW of a complete compressor package, including cooling fans, pumps, and other electrical loads for every 100 cfm of output, not just the break horsepower on the screw inlet shaft.