Before managers can develop a program to cut energy use, they must determine their facility's potential energy savings. One method of assessing that potential is to benchmark energy requirements against those of similar facilities. Before undertaking benchmarking, however, they must determine the energy use levels in their facility.
Determining energy use
Facilities use energy in a number of different forms. Managers should review energy use records and add them by fuel type for a one-year period. To determine total facility energy use, convert each annual fuel use total to its Btu equivalent, then add them up.
It is important to include all fuel - electricity, natural gas, propane and oil - in the calculations. Once the total energy use has been determined, managers should normalize it to allow for comparisons with use in other facilities.
Managers can use several techniques to compare facility energy use, but a widely accepted measure is the energy use index (EUI). The EUI, expressed in Btu per square foot per year, is the total energy use of a facility divided by its total occupied or conditioned square footage. Unconditioned spaces are generally excluded.
The EUI has drawbacks. It doesn't normalize energy use for climate changes. Also, the EUI doesn't account for variations in the use of similar facilities. For example, two office buildings may have different EUI values, due to different occupancy schedules. One may be occupied for 10 hours each day, while the other is occupied for 24 hours a day.
Benchmarking energy use
The key to successful benchmarking using the EUI is careful selection of facilities. There are two sources for benchmarking EUI data: published data and other maintenance managers.
There are a number of different sources for published EUI data, including government publications, trade association reports and energy management handbooks. One of the most comprehensive sources for such data is Commercial Buildings Energy Consumption and Expenditures from the U.S. the Department of Energy.
The publication lists average EUI values for a range of building types differentiated by such factors as age, size, climate, occupancy schedules, construction and energy source. By selecting the most appropriate building category from the data, maintenance managers can estimate their potential for energy savings in their facility.
Selecting conservation targets
Once a manager has determined a facility's energy savings potential, the next step is deciding on areas of focus. The key to successful reductions is concentrating efforts on areas that offer the greatest potential and highest rates of return on the investment. Once those measures are implemented, managers can look elsewhere. The greatest potential for greater energy efficiency in many facilities lies in the major energy-using systems: chillers, cooling towers, boilers and lights.
Lighting systems offer potential energy savings through changes in operations and maintenance. Before considering major lighting replacement or upgrade programs, though, make certain the existing system operates efficiently and effectively.
Tour the facility. In how many areas are lights left on when nobody is in the space? What controls are installed on lighting systems? If you find more than a few cases in which lights are operating in unoccupied spaces, consider installing automatic lighting controls, such as occupancy sensors. Energy savings achieved by automatic controls typically pay for their installation in one to two years.
Next, review fluorescent lighting system maintenance. In spite of the lower labor costs and higher efficiency associated with group relamping, many facilities continue to replace burnt out lamps on a spot basis. By group relamping when lamps reach 70-80 percent of rated life, labor costs are cut by 90 percent. Average lighting levels also improve, as lamps are replaced before light output has deteriorated.
Finally, consider the efficiency of light sources. Consider replacing incandescent bulbs with fluorescent or compact fluorescent lamps. Upgrade standard fluorescent lamps to lamps with high-efficiency electronic ballasts.
Managers continue the efforts by examining maintenance records for other primary energy-using systems:
• When were they installed?
• Have they experienced significant maintenance problems?
• Do boilers, cooling towers and chillers have an effective water treatment program?
• Are chillers opened every one-two years for inspection/cleaning?
• How often are cooling towers inspected and cleaned?
• Are boilers inspected and cleaned annually?
If maintenance has been deferred for even a few years, large potential energy savings lie in performing required maintenance. The systems may be operating, but not operating efficiently unless maintenance tasks are performed regularly.
Before looking into replacing units with higher-efficiency models or installing energy-efficient controls or variable frequency drives, make sure in-place systems operate efficiently. If existing systems are not properly maintained, the same can happen to new systems.
Replacements and upgrades
Additional savings can be found upgrading or replacing systems with new technology. Direct digital controls, variable-speed drives and automatic combustion controls all can be retrofit to provide additional energy savings, provided existing systems operate efficiently.
In some cases, to gain major energy efficiency improvements, systems must be replaced. If systems are approaching the end of performance life or if they cause major maintenance problems, it may be more cost-effective to replace them than to overhaul them.
Whatever systems are installed today to improve energy efficiency, however, must be properly maintained or efficiency improvements will rapidly disappear.
For managers to deliver energy efficiency gains, they need a program that identifies opportunities for improving performance through proper maintenance of energy-using systems, application of new technologies to existing systems and replacement of inefficient systems with new, high-efficiency ones. By following these steps, managers can make their facilities benchmarks for others.
Julian Arhire is a Manager with DtiCorp.com - DtiCorp.com carries more than 35,000 HVAC products, including industrial, commercial and residential parts and equipment from Honeywell, Johnson Contols, Robertshaw, Jandy, Grundfos, Armstrong and more.
