Energy Efficiency Measures

Energy efficiency measures do not operate in isolation from one another. Solar gain through windows that warms in the winter also heats in the summer and can be a source of glare unless controlled. Similarly, lighting efficiency measures affect the operation of heating and air conditioning systems in a building. Accordingly, planning for and executing retrofits should be done with a whole-building performance perspective to ensure cost-effective and efficient performance over the year - and for the long term.

Primer on Energy Rates and Bills

The following sections discuss the key energy efficiency measures outlined in the Recommendations by Sector section of the Guide, organized by area. The measure descriptions are relatively brief, but often include links to more detailed information and/or lists of qualifying high-efficiency products.

COMMERCIAL

INDUSTRIAL

AGRICULTURAL

Motors, Pumps and Fans

Motor-driven equipment, including pumps and fans, accounts for about 64% of electricity and about 30% of total energy consumed in the industrial sector.

There are two general tactics for saving electricity in motor systems: 1) developing a plan for upgrading your motors to premium efficiency motors when they require replacement; and 2) matching instantaneous motor power most efficiently to the needs of the task. Implementing an effective motor strategy involves carefully considering both approaches, and taking practical action. The results are likely to save energy, reduce maintenance costs, and may also improve productivity.

Plan for motor replacement decisions. Before your existing motors fail, it is helpful to have a plan in place for whether to replace or repair the motors, and which replacement motors to choose in the former case. How do you decide whether to have the motor repaired (such as through rewinding) or to replace the motor with a new premium efficiency motor? In many cases the latter is actually the smartest choice. This is because rewinding can degrade the efficiency of a motor by 1 or 2 percentage points, while premium efficiency motors can be 3 or 4 percentage points more efficient than the original standard efficiency motor. For an average motor, the purchase cost is often less than 2 percent of a motor's total lifetime cost, and the motor will consume 50-60 times its initial purchase price in electricity within 10 years of service.

Performing this cost-effectiveness analysis is easy with the use of the Motor Master software available from the U.S. Department of Energy Industrial Technologies Program (ITP). (See http://www1.eere.energy.gov/industry/bestpractices/motors.html.) This free software tool includes a catalogue of motors of various sizes, along with their costs and rated efficiencies. By inputting data such as your price of electricity, load factor, and hours of operation, the software provides the energy and cost savings, and the payback period and return on investment for the particular replacement choice.

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 any overheating of mechanical and electrical components. Prepare a list of premium efficiency motors for replacing existing motors when replacement is necessary.

Match motors with loads. Motors are often oversized for their loads, mainly due to conservative design practices, or subsequent modifications to processes and equipment. In addition many motors are sized to provide the maximum output required under the worst operating conditions, but during typical operation the motor system seldom requires this much output. The excess energy during other times is usually dissipated through some type of throttling device such as dampers or valves. There are two general strategies to save energy in these situations: 1) Install a smaller motor to replace the oversized one, or 2) Install an adjustable speed drive.

As a general rule of thumb, if the maximum loading on the motor is less than 50% of its rated capacity, it may be cost-effective to replace the motor motor with a smaller and more efficient one. The Motormaster+ software tool mentioned above (available at http://www1.eere.energy.gov/industry/bestpractices/motors.html) is also very useful for evaluating these opportunities.

For applications in which the loads vary considerably, installing an adjustable-speed-drive (ASD) can be a good investment. In general, installing an ASD is considerably more expensive than buying a new smaller and more efficient replacement motor, so if the load is consistently low (such as below 50% of the rated output), the motor replacement option is the smarter choice. Another option, rather than installing a variable speed drive on a single motor, is to use several smaller motors, bringing them on incrementally to meet load demand.

Determining if a motor system is a good candidate for variable speed operation requires knowledge of the loads and hours of operation per year. Good potential ASD applications have significant hours of operation at less than the rated (maximum) output. Motors driving pumps and fans should always be evaluated, and potential energy savings from these systems can exceed 50%. Motor and load systems that deliver rated output less than 40 percent of the time, or for which the average output is less than 60% of the rated output are good variable-speed prospects. To be economical, the motor system should also be in operation for many hours per year. Generally, the payback period for an ASD installed on a pump or fan application operating more than 6000 hours per year will be less than two years when the average output is less than 70% of the rated load. DOE's Industrial Technologies Program has software tools to assist in evaluating the cost-effectiveness of ASDs for pump or fan systems. (See "fan system assessment tool" and "pump system assessment tool" at http://www1.eere.energy.gov/industry/bestpractices/software.html.) In addition, installing multiple pumps, fans, or motors for other applications, and staging their operations to match loads is another practical energy and cost savings strategy.

Compressed Air Systems

Compressed air accounts for about 5% of total electricity consumption in industry. Most plants use compressed air for at least some functions; for many, compressor energy is a substantial portion of the 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 systems 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
Use electronic controls on individual compressors to optimize pressure and output.
Consider installing a smaller, high pressure compressor to meet a specific need in order to allow the main compressor to operate at a lower pressure.
Meter energy, flow, and other parameters to assess performance
Maintain the system to minimize air leakage.

Technical resources and a compressed air assessment tool (Airmaster+) are available through the DOE's Industrial Technologies Program, at http://www1.eere.energy.gov/industry/bestpractices/compressed_air.html.

Steam Systems

About 20% of all energy consumption by industry is used to generate steam, which is used for a variety process heating applications as well as facility space heating. There are many opportunities to improve the efficiency of steam systems, which can be summarized into four main areas:

Steam generation -- boiler controls, water treatment, maintenance/cleaning of heat transfer surfaces, matching pressure to end-use needs, etc.;
Steam distribution -- better insulation, steam trap maintenance, and finding leaks;
Steam end-use -- heat exchanger maintenance and other measures to optimize end-use;
Condensate return -- optimize the amount of condensate return and use of low-pressure steam.

DOE also has several steam systems tools and other technical resources to help optimize the efficiency of steam systems. (See http://www1.eere.energy.gov/industry/bestpractices/steam.html.)

Process Heating

Many industrial facilities use process heating, for a variety of operations. Direct process heating (not including steam systems) accounts for about one-fourth of total industrial energy use. Opportunities to improve efficiency in this area include:

Optimize burner air to fuel ratios;
Maintain clean heat transfer surfaces;
Install furnace pressure controllers;
Install waste heat recovery systems;
Preheat combustion air;
Reduce air infiltration in furnaces;
Reduce radiation losses from heating equipment.

DOE's Industrial Technical Program offers a free process heat assessment tool (PHAST), tip sheets, and technical resources. (See http://www1.eere.energy.gov/industry/bestpractices/process_heat.html.)

Combined Heat and Power (CHP) Systems

Combined heat and power (CHP) refers to generating electricity at or near the building where it is used, and then "recycling" the waste heat and using it for space heating, water heating, process steam for industrial steam loads, humidity control, air conditioning, water cooling, product drying, or for nearly any other thermal energy need. The end result is significantly more efficient than generating cooling, heating, and power separately.

The heat from most conventional large-scale power plants is wasted. This is because electricity can be sent over long distances but the heat cannot. And since power plants are typically located far from population centers and far from buildings that could beneficially use the heat, that thermal energy is instead just vented to the surrounding environment.

On the other hand, small-size power plants can be located close to or even within facilities which can make good use of the heat resulting from electricity generation, thereby raising the net efficiency of generating electricity by a factor of two or more and saving substantial energy and money. Hospitals, commercial buildings, apartment complexes, and industrial facilities can often take advantage of combined heat and power (CHP) systems.

To make them most economical and practical, CHP systems need to have a relatively high and constant thermal load so it can match the heat output of the generation process. Keep in mind that in addition to supplying heat for hot water, low pressure steam for heating, sterilizing, and sundry industrial needs, CHP systems can also supply cooling energy via absorption chilling equipment. Generally, it is most cost-effective to size CHP systems to supply the facility’s “base” heating load rather than to size the system based on the electrical load.

Most sites stay connected to the utility grid for back-up power during periods of maintenance or malfunction, although the utility charges standby fees for this. A number of sites also sell their electricity back to the grid when generating more than is needed.

Financial assistance can often be found for installing CHP systems, since they have substantial energy efficiency benefits. The DSIRE Database is one good place to search for funding opportunities for CHP and other energy efficiency measures: www.dsireusa.org.

In Colorado and four other western states, the Intermountain CHP Center provides free feasibility analysis, technical assistance, and expert advice; as well as information on available grants and incentives. For more information see the Intermountain CHP Center website at www.intermountainCHP.org. The EPA CHP Partnership is another good resource: www.epa.gov/chp.

Lighting

Lighting is responsible for approximately 4% of total electricity use in the industrial sector. There are many opportunities 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.

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