Compressed air efficiency

Nov. 26, 2012
In this installment of What Works, Gatorade saved energy and cut operating costs with compressor controls.

While the incentive for plants to go green can be a reason to pursue more efficient energy practices, going green can also help plants retain more money in their pockets. A significant amount of the energy that is used to power a plant’s air compressors can be wasted due to inefficient compressed air systems. Plants can reduce energy use, cut maintenance costs, and improve the efficiency of their compressed air operations using a central control system that decides which compressors to run based on a wide range of criteria, not merely stopping at considerations regarding pressure and the rate of flow.

For example, one plant that saw a need for increased compressed air efficiency is the Gatorade plant in Tolleson, Arizona. This plant is the largest producer of Gatorade and Propel in the world and sits at 797,000 sq ft. Maintaining a supply of compressed air is critical to Gatorade’s process, and, due to the extensiveness of the plant’s bottling operations, this can be a challenge. The plant was running seven compressors in three different locations, but there was no monitoring in place to observe pressure around the plant. “In fact, the Gatorade plant had also been operating its compressors at higher pressure settings than necessary, resulting in wasted energy and potential leaks,” says Tom Schaefer, principal engineer for PepsiCo Gatorade. “We suspected that energy was being wasted, but we didn’t know how much,” he explains.

After undergoing a compressed air analysis by an independent consultant, plant managers installed a PL4000 system by Pneu-Logic (www.pneulogic.com). The PL4000 balances the supply of air against demand using a process called Airgonomics, in which the controller makes decisions on which compressors to run so as to ensure adequate air supply while minimizing energy usage and maintenance costs. The PL4000 uses compressor staging tables to select optimal compressor combinations to run. It decides which compressors to run by scoring compressor efficiency and capacity, production line load, run hours, maintenance schedules, and other user criteria in addition to pressure and flow.

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In the Gatorade plant, the new controller allowed only one compressor to operate at a partial load at a time as a trim compressor. All other compressors were either off or operating at full load. As additional compressors were needed, they were always brought on at full load as the trim compressor continued to run at part or full load. The operator screen shows the operating status of the system at a glance.

Efficient compressor control was achieved at the Tolleson plant without altering the compressor’s native controls, allowing for manual override on any individual compressor. The on-the-fly override that is supported by the PL4000 allows for maintenance of a single compressor with no disruption of control to other compressors.

“The system was started and tuned for optimum performance quickly and while the plant was in full operation,” says Schaefer. By upgrading the plant’s compressed air system and installing the PL4000 compressed air controller, the total amount of energy required to run the compressed air system has been decreased by 21%, resulting in an annual savings of more than 1 million kWh of electricity and a 1.5-year payback on the project. “We got a system that is user-friendly, is expandable, and provides detailed information about the entire compressed air system that can be used for troubleshooting and energy reduction planning,” adds Schaefer.

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