Air compressors have been a versatile tool over the years and compressed air has been one of the driving forces of modern-day life. From simply airing up a tire to a plethora of applications in heavy industrial processes, compressed air has a wide range of uses. However, compressed air as an energy source is inherently inefficient. As much as 80% of the electric energy going into compressors is lost as heat during the compression process. According to the U.S. Department of Energy (DOE), a typical compressed air system requires approximately 7-8 horsepower (hp) of electric power just to operate a 1-hp air motor.
In manufacturing and industrial facilities with intensive compressed air use, it is often referred to as the “fourth utility,” consuming 30% or more of all electricity used. Implementing variable speed drives with air compressors allows the compressor’s operating speed to ramp up or down to match the demand for compressed air. This yields very significant energy savings when compared to a fixed-speed compressor that operates at a constant level regardless of the facility’s demand.
Compressed air systems are usually complex and must be diligently operated and maintained to avoid excessive energy use. In many cases, even small adjustments can result in large energy savings. For instance, according to the DOE, lowering pressure settings by 2 Pounds per Square Inch Gauge (PSIG) results in 1% energy savings. Also, lowering the compressor’s inlet temperature of ambient air by 10° Fahrenheit results in a 2% savings. Cumulatively, adjustments like these can provide very significant energy savings, especially in facilities running hundreds or even thousands of compressor hp continuously.
Further lowering efficiency, compressed air systems are also susceptible to leaking. The hissing of leaking air is the sound of energy wasted! Complex systems commonly include many couplings, hoses, fittings, pressure regulators, condensate traps, valves, pipe joints, etc., which can degrade or corrode and develop leaks in multiple locations. Therefore, it is very important to have a regular maintenance plan for continually fixing leaks in the compressed air distribution system. According to the Compressed Air Challenge, an advocate group for the efficient use of compressed air, a single 1/8-inch hole in a typical system costs around $2,095 in lost energy per year, assuming continuous operation and electricity at $0.05 per kilowatt-hour.
When compressed air is only occasionally used, the most practical method to save energy is to turn off the compressor after it is needed and disconnect or fix leaky air lines. In addition, replacing pneumatic tools with electric motor-driven alternatives generally results in energy savings. Consider the portability of electric battery-powered tools as another major advantage over pneumatic tools consumers may have relied on in the past.
Large commercial and industrial facilities should work with a professional contractor or consultant to complete a compressed air system audit and baseline study. They may identify ways to save thousands of dollars through maintenance or new equipment. Compressed air projects that result in energy efficiency improvements may even qualify for the EnergyWiseSM Industrial Process Incentive Program through local participating utilities.
Your local public utility wants to help their customers gain the most benefit from the electricity they provide. For additional ideas on how to make cost-effective efficiency improvements to your home or business, contact your local electric utility for more information.