Industrial Utility Efficiency
Given that compressed air leak management programs are meant to save energy, reduce CO2 emissions, and generate ROI, DENSO’s Maryville, Tennessee, manufacturing facility can definitively say it has scored a trifecta when it comes to results – and reaped benefits beyond hard numbers alone.
This article reviews portions of an audit report of a compressed air system in a food industry factory located in the U.S. Although the audit explored different supply-side options the client should consider to improve dynamic efficiency, we will focus on the demand side of the system for this article.
This brewery is a relatively large operation with nine production lines plus a keg line. There are five bottle lines and four can lines. Operations in the plant include palletizing de-palletizing, filling, packaging operations, and brewing.
Annual plant electric costs for compressed air production, as operating today, are \$693,161 per year. If the electric costs of \$43,016 per year associated with operating ancillary equipment such as the blower purge dryers are included, the total electric costs for operating the air system are \$736,177 per year. These estimates are based upon a blended electric rate of \$0.06 /kWh.
It is common to see energy assessment specialists treat centrifugal compressors like positive displacement compressors when attempting to reduce compressed air system energy consumption. Unfortunately, centrifugal compressors are normally much larger, and miscalculations can easily represent hundreds of thousands of dollars in overestimated energy savings. These errors are not malicious; they result from oversimplified best practices perpetuated by individuals with limited centrifugal compressor knowledge. This type of knowledge is not readily available and most energy assessment specialists do not have access to engineering teams responsible for the technical development and design of centrifugal compressors.
This article reviews portions of an audit report commissioned to survey the condition of a compressed air system in a factory located in the U.S. The objective of this study is to determine the current operating conditions and make recommendations for improvement based upon application of industry recognized best practices. Due to article space limitations, this article will focus on portions of the over-all audit report provided to the factory.
Energy conservation measures (ECMs) associated with compressed air have received a significant amount of attention over the years, mostly due to a reasonably short financial return compared with other energy-consuming equipment. Over time, many of the recommended corrective actions to reduce compressed air energy consumption were simplified so much that they did not lead to positive results. One of the most common compressed air ECMs is reducing system pressure, and it leverages the best practice calculation —.5 percent power per psi — outlined in the Department of Energy’s Compressed Air Challenge. This article highlights more common issues associated with estimating energy conservation resulting from changing system pressure.
The plant air system consists of eight, single-stage, lubricated, Sullair rotary screw compressors. All units are in good working order. Units 2, 3, 4 and 7 are water-cooled and units 6, 8, 9, 10 and 11 are air-cooled. The main plant air system has two primary compressed air dryers, a Thompson Gordon model TG 2000 refrigerated dryer, and a Sullair model SAR 1350 heatless desiccant dryer. Both units are working according to their design. The TG 2000 uses approximately 11.2 kW and is a non-cycling type unit, and the SAR 1350 uses approximately 200 cfm of purge air to regenerate the wet tower.
When an air system requires large quantities of air (ca. >100 m3/min) and air demand highly fluctuates during the day, it is common belief among end-users that large variable speed screw compressors can deliver significant savings opportunities by precisely matching the compressed airflow to the system’s demand.
Where the daily flow demand has a variability of up to 90% of the maximum air demand, the study compares the energy consumption of six alternative solutions in terms of number of installed compressors, compressor sizes and types of compression technologies (i.e., oil free centrifugal and oil free rotary).
Currently, and for good reason, much attention is being focused on the conservation of energy. Compressed air, like electricity and gas, is an energy resource. It has often been referred to as the third utility. As with all energy sources, our global environment demands that it be conserved and used wisely.
Every municipality and utility is facing the reality of rising energy costs. In 2010, the Town of Billerica, MA, which is located 22 miles northwest of Boston with a population of just under 40,000 residents, engaged Process Energy Services and Woodard & Curran to conduct an energy evaluation of the Town’s Wastewater Treatment Facility (WWTF) and pump station systems sponsored by National Grid. The objective of the evaluation was to provide an overview of each facility system to determine how electrical energy and natural gas were being used at the facility and to identify and develop potential costsaving projects.
This factory, located in the U.S. northeast, spent an estimated \$120,000 annually on energy to operate the compressed air system. The group of projects recommended below reduced these energy costs by \$73,700 or 61% of current use. These estimates are based upon a blended electric rate of \$0.114/kWh.
