Compressed Air Best Practices-August 2008

Focus Industry COMPRESSED AIR AUDITS stry | 08/08 | COMPRESSED AIR SUPPLY EFFICENCY BY BABU JOSEPH, PH.D., P.E., SOUTHERN CALIFORNIA EDISON Abstract This project, under contract from California Energy Commission, developed the CASE (Compressed Air Supply Efficiency) Index as a stand-alone value for compressor central plant efficiency. This Index captures the overall efficiency of a compressed air system’s supply side under typical plant operating conditions. Essentially, the index is a ratio of Standard Cubic Feet (scf) of compressed air supplied by the central plant to the total number of kWh supplied over a given cycle period. The index can therefore be considered as a true output over input metric that measures the general performance of the supply side of a compressed air system in a similar way that the Miles Per Gallon (mpg) figure measures a vehicle’s efficiency. CASE Index has the units of Standard Cubic Feet (scf) per kWh. It has a potential range of 0 to 325. Higher indices represent better efficiencies. Five on-site tests were conducted on compressed air systems in various manufacturing plants. The sites varied in size from 75 to 650 horsepower. CASE Indices at these sites varied from 128 to 245. Background Industry sources estimate the total connected load for compressed air in the US is over 17 million horsepower. For most industrial facilities, compressed air is a necessary part of the manufacturing operation. Generating compressed air is an energy intensive process, and for majority of industrial operations, the energy cost fraction of compressed air is significant in comparison to their overall energy costs. Yet there is a vacuum of reliable information on the energy efficiency of a typical compressed air system. In industrial sites air compressors with auxiliary equipments like dryers, filters, etc., are usually located in a central place, and this area is called the compressed air central plant. The overall energy efficiency of the compressed air system is greatly affected by the full load and part load compressor efficiencies, the control system that operates and sequences the compressors, and various other equipments in the central plant. The full load efficiencies of compressors are well quantified and understood by the operators. But the other factors that significantly affect the overall efficiency are not quantified and are vaguely understood by the operators. As result of all these, the true efficiency of the total system is often very low. To make things even worse, there is no metric available at this time to benchmark the system performance and to track future improvements. This project aimed at developing an acceptable form of metric with procedure to address this issue. www.a rbestp ractices .airbe stpr s.com 27 http://www.airbestpractices.com

Table of Contents Feed for the Digital Edition of Compressed Air Best Practices-August 2008

Compressed Air Best Practices- August 2008 Contents From the Editor Utility-Air News The August Audit of the Month: A Vacuum System Audit Energized for Savings at Seattle City Light and Tacoma Power Know Your System CASE: Compressed Air Supply Efficiency Ecos Air: Managing Incentive Programs Kaeser Compressors: Loyalty, Energy and Growth Building Relationships at Cummins-Wagner McIntire is Moving Forward The 2008 A.I.C.D. Conference & Exhibition Tuthill Vacuum and Blower Systems Resources for Energy Engineers: Training Calendar & Product Picks Wall Street Watch Advertiser Index Job Market

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