Motors are the main consumers of industrial electricity and are used in many plant systems, including HVAC, refrigeration and cooling, and compressed air. Rather than considering just the energy efficiency of a particular motor, the goal is to optimize the energy efficiency of the entire motor system, including the equipment that the motor drives and the system controls.

A systems approach includes five steps:

1. Locate and identify all motors in the facility.

2. Document conditions and specifications of each motor to create a system inventory.

3. Assess the use of each motor system to determine if the motors are the right size for the job they do.

4. Collect information on potential repairs and upgrades in order to plan for increased energy efficiency.

5. If upgrades are implemented, monitor the system to determine actual cost savings.

Include life-cycle costs, not just purchase and installation costs, when selecting a new motor. Energy consumed over the lifetime of a motor’s operation accounts for 95 percent of its total cost.

• Assess the motor’s energy efficiency and make sure it is properly installed. Proper installation can ensure that the motor runs cooler with higher service requirements, longer bearing life, longer insulation life, and less vibration.
• It may be more cost-effective to rewind an existing motor than buy a new one. When rewinding costs exceed 60 percent of the cost of a new motor, opt for the new motor.
• Ensure that motors are the right size for the job. If peak loads on driven equipment can be reduced, so can the size of the motor. For U.S. industry, replacing oversized motors saves on average 1.2 percent of total motor system energy use.
• Consider adjustable speed drives, which better match speed to load requirements for the operation of a motor system. Energy savings may vary from as low as 7 percent to as high as 60 percent.

Compressed air is the least efficient form of energy used industrially, with efficiency typically running about 10 percent from start to end use. It should be used sparingly and constantly monitored and reweighed against possible alternatives. Because of its low efficiency, any improvements pay for themselves quickly, often in less than one year.

• Maintain compressed air systems. Inadequate maintenance can increase air leakage or pressure variability and result in higher operating temperatures, poor moisture control, and contamination of system components.
• Reduce leaks in pipes and equipment. Without proper maintenance, a plant system could suffer a leak rate of 20 to 50 percent of the system’s total production capacity. Leak repair can reduce this rate to less than 10 percent, lowering annual energy consumption by 20 percent.
• Turn off unnecessary compressed air. Equipment no longer using compressed air should have the air turned off completely. This can be done with a single solenoid valve.
• Use other sources of power. Some energy engineers believe finding alternatives has the largest potential for compressed air energy savings.

Pumps are important pieces of equipment in industrial plants. They are the main component of any system that moves liquids, whether for cleaning, eliminating wastewater, or circulating liquids within a particular process.

• Take a systems approach when looking for ways to save energy in a pump process. An efficient pump that is too large might be wasting energy by moving more liquid than the system requires.
• Consider energy and maintenance costs over the lifetime of a pump when planning a purchase. In some cases, energy and maintenance can account for up to 90 percent of the total cost of owning a pump.
• Implement a pump system maintenance program. Improved maintenance can lead to system energy savings of 2 to 7 percent. If systems are not properly maintained, efficiency can drop, pumps can wear out more quickly, and energy costs can increase.
• Install high-efficiency pumps. A pump’s efficiency can drop by 10 to 25 percent over the course of its lifetime. Replacing old pumps with new ones can create system energy savings of 2 to 10 percent.
• Don’t use a larger pump than you need for the job. Replacing oversized pumps with properly sized pumps can reduce electricity consumption by 15 to 25 percent. If peak loads are reduced by improvements in pump system design or operation, pump size can be reduced as well.
• Use multiple pumps installed in parallel to save energy in systems with variable loads. Systems often consist of a large pump for peak demand and a small pump that runs under steady-state conditions. This is more efficient than using one oversized pump to handle loads far below its capacity.
• Avoid throttling valves. They indicate a pump that is too large for the load or a pump system design that does not efficiently accommodate load variations.
• Consider adjustable-speed drives (ASDs). They work efficiently to adjust a pump’s speed to meet demand, saving energy that would otherwise be lost to throttling and bypassing. However, ASDs are not appropriate for pump systems that operate at high static head or for extended periods under low-flow conditions.