Most manufacturing facilities can benefit from low- or no-cost energy-reducing actions.
Turn Things Off
Turning things off seems simple, but remember that for every 1,000 kWh that you save by turning things off, you save $100 on your utility bill (assuming an average electricity cost of 10 cents per kWh).
Walk-through audits. For facilities that don’t operate constantly, one method to identify energy-efficiency opportunities is a walk through the facility after hours. Much of the equipment that is left on overnight or over the weekend in an empty building is a good candidate for saving energy by switching it off. Consider recruiting volunteers from each shift as monitors.
Motors. Identify motors that are operating unnecessarily and shut them down. This could be as simple as ceiling fans running in unoccupied spaces or as complicated as cooling tower fans still running after target temperatures have been met.
Computers and office equipment. Use of information technology in manufacturing facilities is increasing. The typical desktop computer and monitor together can draw as much as 270 watts, and a notebook computer can draw 50 watts; if left on overnight and on weekends, a single computer and monitor could add over $100 to the annual energy bill. Most of the equipment sold today can go into a low-power sleep mode after a period of inactivity. Unfortunately, most users don’t take advantage of this feature, but desktop computers shipped since 2008 should have these options enabled by default. If a facility has networked computers, an administrator may be able to control power settings at the server level with group policy objects (GPOs). The U.S. Environmental Protection Agency has created a free tool, EZ GPO (link is external), to assist network administrators in creating GPOs. In addition, if your system has multiple types of hardware and operating systems on the same network, it may be worthwhile to purchase a computer power management software solution.
Other plug loads. Items such as computer speakers, radios, and coffee pots can burn a significant amount of energy. Like computers, other office equipment such as printers and faxes will also have energy-saving settings. Smart strips sense when devices are in “off” mode and will cut all power to the devices plugged into them, eliminating phantom loads. Smart strips that control loads based on occupancy are also available. Supplying power strips to employees also gives them an easy way to switch off all their often-forgotten energy users at the end of the day.
Space heaters. Space heaters are energy hogs, drawing 1 kilowatt or more of power. As a first step, plug heaters into power strips controlled by occupancy sensors (other loads, such as task lights and monitors, can also be plugged into the power strips). Beyond that, recognize that the perceived need for individual space heating usually signals poor HVAC system control.
Lights. Turn lights off when they are not in use. For larger facilities that have lights covering vast floor areas, only turning lights on when they are needed can have a substantial impact on consumption. Occupancy sensors and timers can capture these savings, but they need to be combined with lighting systems that can be effectively controlled. A no-cost option is to simply train staff to turn off lights as part of closing procedures (you can also help by identifying the location of light switches on a posted notice).
Outside-air intake controls. Many facilities have rooftop units for heating, ventilation, and sometimes cooling. Some are equipped with exhaust fans that bring in outside air for ventilation. Set these to run only when spaces are occupied.
Turning Things Down
Some equipment cannot be turned off entirely, but turning it down to minimum levels when possible can save energy.
HVAC temperature setbacks. If building temperatures are not controlled by an energy-management system, a programmable thermostat can increase energy savings and enhance comfort by automatically adjusting to preset levels. It can also lower temperatures on weekends and holidays.
Dimmable lighting controls. For larger facilities that might have lights on across the whole facility, lighting controls such as photosensors and dimmable ballasts can save energy by reducing lighting levels and helping to reduce maintenance costs. Photosensors adjust the light output based upon the amount of light they sense, and dimmable ballasts allow each fixture to adjust light levels as needed. It’s important, however, to combine these technologies with appropriate lamp types. For example, high-intensity discharge (HID) light sources have long start-up and restrike times and so can’t be shut off based on occupancy, but they can be dimmed to about 50 percent of initial power. Fluorescent lamps are a better choice for dimming due to their faster startup time, but frequent on-off switching can reduce their life span. Light-emitting diodes (LEDs) can be effectively controlled this way, but they come at a significant cost premium. For common areas, a recommended strategy is to use a combination of scheduled lighting and dimming, plus occupancy-sensor controls after hours.
Vending machine controls. Use occupancy sensors to power down vending machines when the area is unoccupied. Sensors can save nearly 50 percent of the $170 to $250 in annual electricity costs needed to operate a single vending machine.
Perform Regular Maintenance and Cleaning
Keeping the facility and equipment in good working order is important, both to save energy and to protect equipment.
Process heating. There are a variety of ways to improve energy efficiency in process heating. Optimizing the ratio of air to fuel with flow metering or flue-gas analysis is one of the simplest ways to maximize burner efficiency. For indirect heating systems, inspect and clean heat-transfer surfaces regularly to avoid soot, scale, sludge, or slag buildup that can significantly reduce system efficiency. Reduce air infiltration into the heating process by repairing system leaks and keeping furnace doors closed whenever possible.
Motors. Mechanical problems are the main cause of premature failures of electric motors. Routinely lubricating, checking for adequate and clean ventilation, and ensuring motors aren’t suffering from a voltage imbalance will help them achieve their full-life potential while simultaneously minimizing their energy consumption.
Fans, bearings, and belts. Inspect fan blades, bearings, and belts at least once a year to prevent failure and maintain efficiency. During the inspection, fan blades should be cleaned, bearings should be checked for adequate lubrication, and belts should be adjusted and changed if needed.
Boilers. Develop a program for treating makeup water to prevent equipment damage and efficiency losses. Buildup inside the tank will decrease heat transfer to the water and necessitate more-frequent blowdown, which wastes both water and energy. In addition, the air-fuel ratio has the largest impact on combustion efficiency, so check it periodically to ensure that the combustion process is operating efficiently.
Air compressors. Check air compressor hoses and valves for leaks regularly, and make repairs if needed. A poorly maintained system can waste between 25 and 35 percent of its air due to leaks alone and can effectively double the cost of compressed air. Because leaks also result in lower pressure at the endpoint, operators can compensate by setting pressure levels higher than would otherwise be necessary, thereby increasing energy consumption. A leak detector can provide long-lasting benefits and can pay for itself in less than six months. Cleaning intake vents, air filters, and heat exchangers regularly will increase both equipment life and productivity. The Compressed Air Challenge (link is external), a collaboration of compressed-air users, offers a wealth of experience regarding compressed-air systems.
Building envelope and seals. One major source of energy loss is air leakage, such as through gaps around doors on the receiving and loading docks. Regularly check and repair gaps in door seals, and make sure employees keep the doors closed.
Lighting. Cleaning lightbulbs and fixtures can increase lighting output levels that have been reduced by dirt and dust. According to the U.S. Department of Energy (DOE), cleaning light fixtures can boost indoor light output by 10 percent. The plastic diffusers that cover most lamps need to be periodically replaced because, over time, they can turn yellow or brown, significantly reducing light output. Lenses can have the same problem. Replacing discolored diffusers or lenses will boost output by up to 20 percent. Calibrating occupancy sensors and photocells to restore correct operation can reduce energy use by up to 50 percent. For more information on lighting maintenance, see the Illuminating Engineering Society’s Recommended Practice for Planned Indoor Lighting Maintenance. (link is external)
Economizers. Many air-conditioning systems use a dampered vent called an economizer to draw in cool outside air when it is available to reduce the need for mechanically cooled air. The linkage on the damper, if not regularly checked, can seize up or break. An economizer that’s stuck in the fully open position can add as much as 50 percent to a building’s annual energy bill by allowing hot air in during the air-conditioning season and cold air in during the heating season. Have a licensed technician calibrate the controls; check, clean, and lubricate your economizer’s linkage at least once a year; and make repairs if necessary.
Air filters. Change air filters every one to three months. More-frequent filter changes may be required for filters handling a heavy particulate load or large size of particulate. Air conditioners that are located next to highways or construction sites or that are using an economizer will also need more-frequent filter changes.
Leaks. A leak in an HVAC rooftop unit can cost $100 per unit per year in wasted energy. On a quarterly basis, cabinet panels and ducts on rooftop HVAC equipment should be checked for leaks. A check should also be made to ensure that the units are secure, with all screws in place. On an annual basis, inspect all access panels and gaskets—particularly on the supply-air side, where pressure is higher.
Condenser coils. Cleaning the condenser coil is one of the most cost-effective maintenance steps that can be done on HVAC rooftop units. A dirty coil that raises condensing temperatures by as little as 10° Fahrenheit (F; 5° Celsius [C]) can increase power consumption by 10 percent—resulting in about $120 in electricity costs for a 10-ton unit operating 1,000 hours per year. Condenser coils should be checked for debris on a quarterly basis and cleaned at least once a year.