Best Practice Guide

Food and Beverage Growers and Processors

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

Energy Use Basics

Proper Maintenance

Energy-Smart Investment

Demand Response

Distributed Generation

Water Use


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Sara Lee

Vineyard 29


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Motors

Energy-Smart Investment

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Premium Efficiency Motors
The purchase price of most new motors accounts for just two percent of the total lifetime cost - electricity, on the other hand, accounts for nearly 98 percent. Given this, it is easy to see why spending a bit more for premium efficiency motors generally pays back any marginal costs in short time. Premium efficiency motors typically improve energy efficiency between 2 to 10 percentage points compared to standard motors, but can cost between 10 to 30 percent more to purchase.

As the benefits and savings of premium efficiency motors become more commonly recognized, so to do sales. NEMA estimates that between 2001 and 2002, total net units shipped increased 30 percent. Shipments rose another 14 percent between 2002 and 2003.

To calculate cost savings from a premium efficiency motor, use this calculation:

Expected annual savings = HP x LF x 0.746 x Hr x $/kWh x (100/Estd - 100/Eee)

HPMotor horsepower - see motor baseplate
LFLoad factor - see motor baseplate
HrOperating hours
$/kWhAverage energy costs
EstdEfficiency of standard motor
EssEfficiency of energy-efficient motor
0.746Conversion factor (horsepower to kW)

To demonstrate how a slight improvement in efficiency can result in significant cost savings, consider a hypothetical premium efficiency motor with the following specifications:

Motor50
Load factor0.75
Operating hours6,552
Average energy costs$0.09
Efficiency of standard motor89 percent
Efficiency of energy-efficient motor93 percent
Conversion factor (horsepower to kW)0.746

Under these conditions, a four-percent increase in motor efficiency will save an estimated $797 annually. Assuming an operating lifespan of 10 to 15 years, our hypothetical motor could save upwards of $10,000 over the course of its useful life.

Even greater savings can be expected from efficient motors with higher horsepower and longer operating hours:

 Electricity cost per kWh
 $0.10$0.15$0.20
Horsepower5$89$133$177
25$443$664$886
55$974$1,462$1,949

Estimated annual savings in grey boxes. Assumptions: .75 load factor, 6,552 operating hours and a four-percent increase in motor efficiency.


 Electricity cost per kWh
 $0.10$0.15$0.20
Operating hours2,190 (25% of time)$296$444$592
4,380 (50%)$592$888$1,184
8,760 (100%)$1,184$1,776$2,369

Estimated annual savings in grey boxes. Assumptions: .75 load factor, 50 hp and a four-percent increase in motor efficiency.


Repair or Replace?
For each new motor purchased, two-and-a-half motors are repaired. Put another way, the average motor is repaired every five to seven years, or about three to five times during its lifetime.

The best way to decide between motor repair and motor replacement is to first calculate potential energy savings and then calculate simple payback (this calculation is also useful comparing standard efficiency motors to premium efficiency motors). Use the formula above to calculate expected energy savings, then add this calculation:

Simple payback = Premium price ÷ Annual savings

Repair when...Replace when...
A failed motor is already energy efficient.Repairing a standard-efficiency motor costs 60 percent or more of the cost of a premium-efficiency replacement.
Motor operates < 2000 hours per year; payback on investment is neither quick nor substantial.Motor operates > 4000 hours per year; payback on investment is about two years.
Motors oversized < 50 percent should be evaluated to compare payback rates and annual energy savings.Motors oversized by 50 percent or more can cost-effectively be replaced by smaller, more efficient motors.

Recommendations based on Consortium for Energy Efficiency's brochure Efficient Motors: Selection and Application Considerations.

Variable speed drives
Variable speed drives (VSD) - also referred to as adjustable speed drives - substantially improve energy efficiency, particularly for a motor that often runs at partial loads or whose load profile fluctuates throughout the day. VSDs can save as much as 50 percent of a motor system's energy use, help prolong equipment, and give operators greater flexibility over processes. Because advancements in computing technologies have both improved VSD performance and driven down costs, VSDs are fast becoming the preferred method for controlling motor speed.

A VSD typically comes as a stand-alone control box that is capable of precisely tailoring motor speed to load demand. The process is both straightforward and elegant: rather than mechanically modifying the motors they control, the VSD precisely regulates motor speed by moderating the flow of electricity to attached motors. VSDs run very efficiently; is not unusual for the VSD itself to be more than 94 percent efficient right down to 50 percent load or less. VSDs also offer the added benefits of helping to cut down on motor noise, improving production efficiency and eliminating the "voltage sags" (often evident from temporarily dimmed lights) common to motor startup.

Prices for VSDs vary greatly, although as a general rule a basic VSD will cost roughly the same as the motor it drives. In many cases, initial capital costs can be offset by rebates and other incentive programs sponsored by local utility providers.

Specifying Premium Efficiency Motor Purchases

Specifying Premium Efficiency Motor Purchases
A 1998 Department of Energy survey of American businesses found that only 11 percent of potential motor and pump customers have policies in place to guide their motor purchases. Of those with guidelines in place, only two-thirds reported including efficiency among their criteria for new purchases.


Since motors can last as long as 30 years, it is important to replace retired motors quickly, with the most cost-effective new model. Keep regular maintenance records that indicate which motors might be underperforming or otherwise malfunctioning. Be prepared beforehand by comparing the lifecycle costs of different potential replacement motors, then determine which option is the most cost-effective for your needs. If you have the resources, consider purchasing and storing the replacement motor before the worn motor dies to help minimize any downtime.


Work with the purchasing department to create a general purchasing policy that specifies premium efficiency motors. Purchasing personnel may also be helpful calculating the cost-benefit of different options, and working with motor vendors.

NEMA Premium Efficiency Motors

NEMA Premium Efficiency Motors
The member companies of the NEMA Motor and Generator Section established a NEMA Premium® energy efficiency motors program to provide highly energy-efficient products that meet the needs and applications of users and original equipment manufacturers (OEMs) based on a consensus definition of "premium efficiency" and use of the NEMA Premium® logo for premium products.


NEMA Premium® labeled electric motors will assist purchasers to optimize motor systems efficiency, reduce electrical power consumption and costs, and improve system reliability. It is estimated that the NEMA Premium® efficiency motor program would save 5,800 gigawatts of electricity. This translates to preventing nearly 80 million metric tons of carbon dioxide into the atmosphere over the next 10 years -- equivalent to keeping 16 million cars off the road.


Resources

See Flex Your Power product guide on motors.

The National Electric Manufacturers Association (NEMA) website contains information on the NEMA Premium® energy efficiency motors program, including product specifications and a list of participating partners.

The Consortium for Energy Efficiency (CEE) website on Motors and Motor Systems includes a Motor System Tool Kit, efficiency specifications, resource links and information on the Motor Decisions Matter campaign.

Efficient Motors: Selection and Application Considerations. A brochure developed by CEE and the U.S. Department of Energy's Motor Challenge Program. Boston, MA: 1999.

U.S. Department of Energy (DOE) free software MotorMaster+ is an energy-efficient motor selection and management tool, including a catalog of over 20,000 AC motors. This tool features motor inventory management tools, maintenance log tracking, efficiency analysis, savings evaluation, energy accounting, and environmental reporting capabilities.

U.S. DOE free softwarePumping System Assessment Tool (PSAT) helps industrial users assess the efficiency of pumping system operations. PSAT uses achievable pump performance data from Hydraulic Institute standards and motor performance data from the MotorMaster+ database to calculate potential energy and associated cost savings.

Electrical Apparatus Service Association (EASA), Inc. is an international trade organization of over 2,150 electromechanical sales and service firms in 50 countries. The EASA website contains downloadable, in-depth guidelines to improve motor efficiency, repair worn or malfunctioning motors, and to help owners decide whether to replace or repair motor systems.