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Utilities Metering

1. BACKGROUND: Prior to the 1970’s, energy was inexpensive. Consequently, these costs were often ignored. In that era of energy affluence, inefficient practices developed. On military installations, the problem was further compounded by a general lack of metering systems. The Department of Energy reports that prior to 1973, the energy costs of a typical metal fabricating company totaled one-half of 1 percent of the total operating budget. By 1980, energy costs rose to 10 percent of the total operating costs and in other industries, energy consumed as much as 25 percent of the operating budget. With energy rivaling, or in some instances exceeding, other major cost categories, attention focused on ways to reduce the staggering expenses. Numerous programs designed to eliminate energy wasteful operations and improve efficiency were implemented nationwide. This manual emphasizes the essential role of meters in energy management programs.
2. WHY METER: Metering is a management tool that points the way to efficient use of utilities. Without metering, utility managers must depend on estimates and models to determine effectiveness of their utilities systems. For example, by metering, managers can identify energy waste or questionable practices, determine if steam and electric distribution lines are properly sized, and ascertain if transformers are improperly utilized. Metering pinpoints equipment in need of repair or that is being used ineffectively. Intelligent use of information generated by metering can result in savings of both energy and dollars. Identifying and eliminating operational practices or equipment that waste or inefficiently use energy will contribute substantially to successful energy management programs.
2.1 Identifying Energy Users: Many studies have been conducted to evaluate the use of meters versus “flat rates.” These studies typically conclude that large savings can be achieved by metering energy use. An electric utility company in the Southwest found energy use decreased approximately 40 percent when flat rates were eliminated and individual meters installed. As a corollary, individual meters in an apartment complex were eliminated in favor of a master meter and energy consumption doubled. Not all studies identify such dramatic results, but they clearly show a potential exists for significant savings if the user is accountable for the energy he consumes.
3. REDUCING COSTS: Almost all electricity supplied by utility companies, because of its extensive use, offers potential dollar savings. Other energy systems such as steam, high-temperature water, and natural gas also offer opportunities for savings.
4. ELECTRICITY MANAGEMENT: Electrical energy costs are high and are expected to escalate. This makes it mandatory that energy saving procedures be Implemented. This task is more complicated than merely using less electricity, although lower consumption reduces cost. Since billing procedures are often extremely complicated, it is imperative that a complete billing schedule be obtained from the utility company serving the installation. Once it is analyzed to determine what the company is charging for and why, it is possible to evaluate which changes in procedures and equipment that will achieve savings. Normally, electric utility companies use three major elements to bill:
  • Demand
  • Power Factor
  • Total Energy Used
Depending upon specific billing practices, other factors, usually of lesser impact, add to basic billing charges: fuel adjustment charges, time-of-day factor, seasonal rate charges, etc.
4.1 Demand: Demand is electrical power measured in kilowatts required by a specified consumer. Demand is usually metered at specified intervals during the day.
4.2 Power Factor: Power factor is the ratio of power used to power supplied. For alternating current, the ratio normally ranges from 0.75 to 0.95.
4.3 Total Energy Used: Electric energy is the amount of electric power used over a period of time. Multiplying electric power by hours of use equals total energy used in kilowatt hours.
5. STEAM MANAGEMENT: Steam costs typically rank just below electrical energy costs. The cost of steam, in recent years, has increased by an order of magnitude. Its continued escalation provides a powerful incentive to pursue a steam management program. In 1985, steam costs at naval installations varied from $8.00 to $16.00 per million British thermal units (MBTU). Leaks in a steam distribution system are costly. Table 1-1 shows the cost of various sized leaks in a steam system pressurized to 100 pounds per square inch gauge (psig) with steam production costs of $10.00 per MBTU. Without adequate steam metering, it may be difficult to identify and locate areas of waste. Leaks in overhead steam lines usually can be located as the escaping steam is visible. However, when insulation is damaged or missing, the heat losses can be considerable although the cause may not be so obvious. Leaks in underground steam mains are another problem often difficult to correct. Another common cause of wasted steam is malfunctioning or incorrectly specified steam traps. A comprehensive steam trap program may give the highest payback available. Manufacturers’ manuals should be consulted for suggested inspection frequency and maintenance practices. Additional waste occurs when buildings are overheated, and the excess heat is vented through windows and doors. Such losses must be identified and eliminated.
TABLE 1-1. Cost of Steam Leaks at 100 PSIG
5.1 Steam and Fluid Metering: Steam, too often, is metered only at the point of production. For metering to be effective, meters are also required at the plant, in the distribution system, and at the points of consumption. This , dispersed metering is necessary to meet the objectives of metering:
  • Determine plant efficiency
  • Determine distribution system efficiency
  • Manage the system
  • To bill users
5.2 Fluid Meters: The use of fluid meters to monitor steam is prevalent. The various fluid meters are categorized by their operating principle: positive displacement meters, differential pressure meters, velocity meters, and open channel meters. Parameters metered are flow rate, velocity, temperature, or pressure at specific places and times.
5.2.1 Cost Considerations: When deciding to meter,the following items are some of the cost considerate.c]ns which must; must be addressed:
  • What fluid(s) are to be metered?
  • What information is required?
  • What type meter will best provide the information?
  • What is the initial cost of each meter?
  • What type of installation-permanent or temporary?
  • What special equipment is required for installation?
  • Will shutdown of the system be necessary for installation?
  • What ancillary or transmission equipment is required?
  • How often and to what extent is maintenance required?
  • How much energy loss accrues from metering?
  • What are personnel and training requirements?
6. OTHER ENERGY MANAGEMENT: High-temperature water, natural gas, potable? water, and wastewater represent systems that cost less than either electricity or steam; however,costs are not insignificant.Metering programs should be initiated to determine how effectively these systems are being used and what savings can be obtained.
6.1 High-Temperature Water: Hot water is frequently employed in applications closely related to steam.Meters may introduce problems in a hot water system that do not apply to a steam system, even though many meters can be used in either system. For example, meter induced pressure drops in a high-temperature water system can be critical if not accounted for in the original design. Should orifice meters be retrofitted in a system that was not initially designed for them, it is possible that the difference between the working pressure and saturation pressure of the fluid, sometimes called the antiflash margin, could disappear. Should the water flash to steam, results could be catastrophic,Therefore, it may be necessary to employ only meters that operate with very low or zero pressure drop.
6.2 Natural Gas: Since natural gas is often used for- heating purposes, individual. meters may result in proportional. savings as is the case with electrical energy when flat rates are terminated in favor of individual meters , Thermostats normally are installed in conjunction with a natural gas heating system.
6.3 Potable Water: Managing use of potable water does offer opportunities to conserve dollars. Similar to the situation with individual natural gas meters, installation of individual meters offers management an opportunity to establish and monitor goals. Major points of water loss can occur industrial processes and breaks in water mains. Additionally, in buildings used by large numbers of individuals, the aggregate effect of leaking faucets, valves, and toilet malfunctions result in sizable losses. In these instances, metering will help to detect and correct wasteful practices.
6.4 Wastewater: Meters used in wastewater systems are determined by the type of effluent and usage of the treated product. Meters determine the amount of fluid entering the processing plant and verify changes in the volume trends. With the advent of stringent effluent standards, management must evaluate ways to reduce the volume and improve the quality of plant discharge. If the volume of the fluid to be treated is accurately known, the amounts of chemicals to be added for co-precipitation or exchange processing of the effluent can be determined more accurately.
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