Recommendations by Sector

GENERAL INDUSTRIAL

Energy Use

Principal energy use in industrial facilities depends strongly on the energy needs of the process that produces raw materials or turns raw materials into finished products. A plant that produces frozen vegetables uses large amounts of electrical energy for refrigeration while a plant that heat treats metal uses lots of natural gas to fire furnaces. However, in virtually all industrial facilities, motors play a key role. More than half of the electrical energy used in the U.S. powers motors and half of that is in the industrial sector. While waste in motor use is widespread, there are usually cost-effective options to raise efficiency and save money.

Motors used in industry drive devices such as pumps, fans, compressors, and conveyors. The pie chart to the left shows national numbers on industrial motor systems end use.

Note that pump, compressed air, and fan electric energy together constitute 55 percent of electric motor use in the industrial sector. These items are discussed here, as are a number of others applicable to most industrial facilities.

Motor Systems Efficiency

There are two general tactics for saving energy that powers motors: ensuring that the motor itself is highly efficient; and matching instantaneous motor power most efficiently to the needs of the task. Implementing an effective motor strategy involves carefully considering both and taking practical action. The results are likely to save energy, demand charges, and maintenance costs—and they may improve productivity in the bargain.

Replace low-efficiency motors with premium-efficiency motors. Over its lifetime, the cost of a motor can be outstripped by the cost of the energy it uses by a factor of 100 or more. Accordingly, an improvement in efficiency of only several percent is usually a cost-effective investment. See the Motors and Motor Systems measure description for a table of premium-efficiency ratings by horsepower.

Match motors with loads. Failure to match motors with loads is a leading cause of needless electrical energy consumption. In many industrial, agricultural, and commercial applications, motors are oversized for all or most of the time. Installing a variable speed device that allows the motor to run as efficiently as possible for the instantaneous needs of the task can be a particularly cost-effective retrofit for motors that move fluids, such as pumps, fans, and air compressors. Cutting back on motor power to the point where flows are just adequate saves considerable energy. In addition, installing multiple pumps, fans, or compressors and staging their operations to match loads is another practical energy and cost savings strategy.

Institute a motor maintenance program. This includes routine inspections of all motors (with emphasis on those critical to production), including the drive train, which should be realigned and lubricated as needed; measuring energy use; and identifying overheating of mechanical and electrical components.

Air Compressor Options

Most plants use compressed air for at least some functions; for many, compressor energy is a substantial portion of the entire electric bill. Many compressor systems are poorly laid out, have leaking fixtures, and motor/compressor systems are frequently mismatched to loads. Suggestions for curbing energy waste in air compressor options include the following:

• Use properly-sized, energy-efficient compressors driven by energy-efficient motors and associated storage tanks that are matched to loads.
• Ensure that systems can operate efficiently at part loads and use electronic control on individual compressors if applicable.
• Meter energy, flow, and other parameters to assess performance and minimize system air pressure.
• Optimize mechanical design, using a closed loop system if practical.
• Maintain the system to minimize air leakage.

Lighting

Lighting is responsible for approximately 9% of total electricity use in the industrial sector. There is large potential for cost-effective lighting energy savings in many industrial facilities. Measures frequently found to be practical include:

• Paint ceilings and sidewalls with a white semi-gloss paint. This will enhance the lighting quality at most work stations by raising brightness levels and softening shadows and glare whether light is from electric fixtures or from the sun.
• Consider replacing conventional high intensity discharge lighting in medium and high bays with fixtures that use more efficient T-5 fluorescent lamps that may be dimmed step-wise when daylighting is available.
• Replace T-12 fluorescent fixtures with T- 8 or T-5 fixtures with electronic ballasts.
• To prevent glare from direct beam sunlight, install reflectors (“light shelves”) either inside or outside high bay windows on the east, south, and west to redirect light onto the white ceiling. High bays with windows toward the top are ideal for providing natural lighting, but they can also be a source of glare from direct beam sunlight. Light shelves allow the ceiling itself to function as a source of diffuse natural light, creating an attractive, virtually shadow-free lighting environment at the work stations below.
• Install systems that redirect direct beam sunlight from rooftop windows onto light-colored ceilings, thereby controlling for glare and converting sunlight into a diffuse lighting source.
• Install and adjust automatic dimming controls to take advantage of daylighting. The “Cool Daylighting” approach keeps most outside light out of the field of view, thereby controlling for glare, producing better distribution, and lowering cooling costs. See www.daylighting.org/what_is_cool_daylighting.htm.
• Install LED exit signs.
• Upgrade parking lot lighting to save energy and reduce the environmental impacts associated with lighting the sky instead of the parking lot.

Combined Heat and Power (CHP) System

Install a combined heat and power generation system to supply electricity for process loads, low pressure steam or hot water for heating needs, and provide cooling (through an absorption chiller powered by low-pressure steam). When properly sized and designed, such a system can save substantial money and avoid the large thermal losses associated with conventional power generation at utility plants. Such systems may be sized to merely control peaks, to supply all of the electrical and some thermal needs, or to supply all thermal needs and provide extra electricity to the local power company.

Power Factor

Most utilities charge industrial consumers for reactive loads. Hence, low power factors, usually due to the running of large motors, increases the electric bill. The solution is to balance the inductive load with a bank of capacitors. These can be brought on as needed to maximize the power factor and lower the reactive load cost.

© 2003 Southwest Energy Efficiency Project
2260 Baseline Road, Suite 212, Boulder, CO 80302
(303) 447-0078 fax: (303) 786-8054 info@swenergy.org