Best Practice Guide

Food and Beverage Growers and Processors

Fetzer Vineyard

J Vineyards and Winery

Mission Foods

S. Martinelli and Company

Sara Lee

Vineyard 29


Introduction

Planning an Energy Program

Funding and Approval

Commissioning

On-the-Farm Energy Use

Lighting

Building Envelope

Central HVAC System

Boilers

Steam

Combined Heat and Power

Compressed Air

Refrigeration

Motors

Demand Response

Distributed Generation

Water Use


View the Glossary

Case Study

Sara Lee

Printer-friendly version

Share your thoughts

Location: Sacramento, California
Size: 300,000 sq. ft.
Type: Industrial bakery
Year Built: 1929

Project: Compressed air system assessment and optimization
Energy savings: 471,000 kWh
Cost savings: $40,000
Payback: 6.5 months

Website: http://www.saralee.com and http://www.compressedairchallenge.org/

Source: Adapted from a U.S. Department of Energy (DOE) case study


Company Information
Sara Lee Bakery Group, a division of Sara Lee Corporation, prepares and markets a full line of branded, packaged baked good in the United States, Europe and Australia.

Sara Lee's Sacramento facility is a 300,000 sq. ft. industrial bakery built in 1929. With 450 full-time employees, it operates a high-speed bread and bun line, seven days a week. The onsite compressed air system supports the stacking, blowing, and cleaning operations required by bread-making machines.

Compressed Air Assessment and Upgrades
At Sara Lee's Sacramento bakery, a maladjusted compressor controls package and a failed pressure/flow controller caused the compressed air system to perform erratically, increasing both energy use and maintenance costs.

Sara Lee contracted Draw Professional Services, a Department of Energy (DOE) Allied Partner, to conduct a systems-level assessment of the compressed air system that included an AIRMaster+ analysis (AIRMaster+ is a free, Windows=based software tool used to analyze industrial compressed air systems; available from DOE).

Sara Lee's compressed air system consisted of one 100-hp and two 150-hp rotary screw compressors. When the pressure/flow controller failed, air demand patterns began fluctuating severely, forcing workers to operate all three compressors simultaneously just so they could meet production targets. At the same time, the compressor controls were out of adjustment, causing them to respond incorrectly to different air pressures. More than one compressor would activate, for example, when only one unit was actually needed.

On top of this, air leaks accounted for 15 to 20 percent of the entire system capacity. Even worse, the assessment discovered multiple uncontrolled open-blowing applications. Those two problems exacerbated the pressure fluctuations and wasted even more compressed air.

Draw configured the system so that the 100-hp fixed-speed compressor is now the base unit. A 100-hp variable speed drive unit serves as the trim compressor; it comes online as needed, and can vary output to match actual demand. Sara Lee was able to retire one of the old 150-hp compressors, and stored the other one as a backup. The newly optimized system performs much better, and supplies the plant with a consistent air supply at a stable pressure.

Sara Lee's compressed air project is yielding impressive energy savings while making production more reliable. Measurements indicate energy savings of 471,000 kWh and cost savings of $40,000 per year. These figures are consistent with AIRMaster+ estimates. Because two compressors can now be off-line, maintenance costs have also declined, saving another $10,000 per year, for a total annual savings of $50,000. An $11,000 rebate from the Sacramento Municipal Utility District reduced the total project costs to $27,000, for a simple payback of 6.5 months.