Submetering for Improved Building Operations & Maintenance (O&M) Performance
Facility operators need ways to operate more efficiently, cost-effectively and with less downtime. When it comes to proactively managing energy consumption and demand, electric submeters and energy intelligence software are rapidly becoming the high-tech tools of choice, especially where facility operations and maintenance are concerned. This white paper presents an overview of typical O*M strategies with an eye to how metering can help facility professionals better understand their energy profiles to optimize facility performance, increase reliability and energize facility-wide savings.
Quoting Department of Energy stats, Flex Your Power, California's statewide energy efficiency partnership of utilities, businesses, government agencies and other entities, states that the commercial building sector uses approximately 66 percent of all electrical energy consumed in the United States. From 1989 to 2005, for example, consumption of electricity doubled, a trend that, if sustained, will likely see another 150 percent increase by 2030. Consuming roughly 23 million Megawatt-hours (MWh) of electricity, office buildings themselves account for almost 30 percent of all commercial energy demand. With energy representing some 30 percent of a building's total operating costs , electrical consumption by end-use category may be extrapolated according to the break out shown in Figure 1.
Figure 1. commercial building electrical consumption by using source, based on data from a DOE 1999 end-sue consumption survey. notice that lighting and cooling alone account for 50% of all consumption, and the significant impact of plug load on facility demand.
Needless to say, the pervasive use of electronically powered technology across the facility landscape has placed unprecedented demand on the electrical grid. In many cases, however, the energy is wasted through inefficient equipment operation, unnecessary demand peaks and other facility operational issues that are relatively easily and inexpensively mitigated through proper operations and maintenance procedures. In fact, it is estimated that a 30 percent reduction in energy use can lower operating costs by up to $25,000 per year for every 50,000 square feet of office space. Moreover, in terms of commercial asset value, this translates to every dollar applied toward increasing energy efficiency resulting in a three-to-one return . Â Â
As shown in Figure 1, lighting and the HVAC/R load represent 64 percent of the facility's energy consumption and a great opportunity for energy-efficiency monitoring. Typical electrical and electronic devices suitable for operations and maintenance programs include:
- Boilers and steam traps;
- Chillers and cooling towers;
- Energy management and building automation systems;
- Air compressors and air handling systems;
- Fans, pumps and motors;
- Lighting systems.
A quartet of Facility Maintenance Strategies
There is much more to a proper and effective facility O&M strategy than simply repairing equipment after it breaks. Several different types of maintenance strategies may be employed by the facility to optimize system operation, reduce downtime and minimize disrepair. Since every facility is unique to its own operational needs, the following strategies may be combined in some measure to maximize system life-cycle effectiveness and cost-effective operation. Note that the Dept. of Energy expresses relative costs in terms of dollars per horsepower per year :
Reactive-“run it until it breaks” offers the advantages of less staff required and a low cost of on-going maintenance, but can result in unplanned equipment downtime, increased cost for equipment repair or replacement, possible downstream equipment/process damage and others. At $18/horsepower/year, reactive is the most expensive strategy according to DOE (FEMP) statistics.
Preventive-equipment failure is avoided by regularly scheduled maintenance which provides the advantages of greater cost-effectiveness, flexibility, increased equipment lifespan and lower failure rates. Disadvantages include the continued potential for catastrophic failure, labor intensity, waste due to unneeded maintenance and others. At 12-18% cost savings versus reactive, preventive strategies typically cost around $13/horsepower/year.
Predictive-condition-based strategy that examines the current status of the equipment before determining what, if any, maintenance is required. Advantages include a 10x return on investment, 25-30% lower maintenance costs, 70-75% fewer breakdowns, 35-45% lower downtime and 20-25% higher productivity, according to DOE figures. The downside includes higher investment in diagnostic equipment and staff training, and harder to quantify savings potential. At $9/horsepower/year, predictive results in an 8-12% cost savings over preventive strategies and a 30-40% savings over reactive.
Reliability-centered-employs many of the same practices as predictive but takes into account that all equipment is not of equal value nor does it offer the same probability of failure. Less important equipment might be relegated to a reactive or preventive strategy. At a typical cost of $6/horsepower/year, the advantages and disadvantages of RCM are similar to predictive, but the former more closely matches facility resources to needs while decreasing costs even further.
|Table 1. Reliability-Centered Maintenance - Hierarchy of Applications
|Small parts and equipment
||Equipment subject to wear
||Equipment with random failure patterns
|Equipment unlikely to fail
||Equipment with known failure patterns
||Equipment not subject to wear
||Systems which may fail due to incorrect preventative maintenance
Table 1. Reliability-centered maintenance (RCM) incorporates elements of other strategies, based on relative importance or value of the equipment in question. Meters are ideal, low-cost data acquisition tools for characterizing these loads. Source: FEMP "O&M Best Practices Guide," P. 5.6.
Studies conducted by the DOE in the last decade indicate that most facilities employ the above strategies in combination, according to the following relative percentages. Clearly, “fixing it after it breaks” is still the predominant maintenance strategy for the average facility:
- Reactive: 55%
- Preventive: 31%
- Predictive: 12%
- Other: 2%
Metering Approaches Useful in Factory O & M Programs
Whichever maintenance strategy combinations are employed by the facility, the usefulness and value of metering is beyond question, particularly in profiling the high-usage loads broken out in Figure 1. Complementing a program of thermography, oil analysis, ultrasound/vibration analysis or other required diagnostic technique, metering can help facility managers to greatly improve the quantity and quality of data relative to facility operations. When properly used, that information can lead to dramatic economic savings of 20 percent or more by allowing facilities managers to:Â
- Chart energy usage
- Compare energy usage by day, week, month or year
- Monitor all utility services, including electricity, gas, water and steam
- Schedule energy data collections to occur automatically
- Evaluate, in real-time, the impact of critical load-shedding activities
- Determine specific processes that are not energy efficient
- Identify poor equipment performers by benchmarking energy levels at multiple facilities
Once meters are installed and commissioned, they may be employed in a variety of ways (Table 2), depending on the application, to control costs, diagnose equipment problems, allocate usage costs, set resource efficiency goals and any number of other uses. According to a 1996 Electric Power Research Institute (EPRI) study quoted by FEMP , the four main levels of resource metering include:
1. One-Time / Spot Measurements-useful in baselining instantaneous energy use, equipment performance, loading and more. Advantages include lowest cost, ease of use and fast results. However, such measurements often result in low accuracy and single-parameter, single time-slice measurements, among others.
2. Run-Time Measurements-useful where hours of operation are critical. Typical apps include fans, pumps, HVAC and lighting systems in conjunction with one-time/spot measurements. Useful for constant load devices, disadvantages are similar to 1 above, but with additional calculations and recovery and/or manual data download needed.
3. Short-Term Measurements/Monitoring-useful for verifying performance, initiating trending or validating utility efficiency improvements. Duration is typically in weeks or months, but generally not longer than one year. Besides quantifying magnitude and duration, results are achieved relatively quickly although cost and accuracy are both mid-level.
4. Long-Term Measurements/Monitoring-typically permanent installations, meters are used for monitoring situations where system use is impacted by weather patterns, occupant behavior, reimbursable resource allocation, tenant billing and other activities. Advanced, utility-grade meters from E-Mon and others are particularly useful for communicating the metered data to a host computer or building management system, or via phone modem or the Internet (see following sections).
Table 2. Facility Metering Strategies and Corresponding Savings
||Use of Meter Data
|1, Install meters only with software for data collection
||Storing energy data from individual buildings
|2. Strategy 1 plus cost-allocation software
||Monthly reports for all departments and monthly bills to all outside vendors/reimbursables
|3. Strategies 1 & 2, plus operational analysis and building tune-up
||Above plus internal review/adjustments of building operations, time schedules, etc.
|4. Strategies 1-3, plus continual on-going operational analysis and building tune-up
||Above plus continuous, on-going commissioning and adjustments of building operations, time schedules, etc.
Table 2. A number of effective metering strategies may be implemented by the O & M program to achieve a sliding scale of savings based on the hardware and software systems employed. Source: FEMP Fact Sheet, January 2005.
Essentials of Submeter Operation
Now that we’ve seen what types of facility maintenance programs are out there, and how metering plays a role in the overall O&M picture, it may be useful to take a closer look at metering hardware issues in general.
Installed on the “facility side” of the traditional glass-covered utility meter (Figure 2), submeters have proven them-selves to be effective tools for monitoring, diagnosing and preventing bottom line-impacting problems associated with the facility’s energy envelope. As such, meters are the ideal data acquisition and monitoring tool for facility O&M applications. When combined with energy intelligence software, submeters provide insight on a building’s flow and consumption of electricity. In today’s increasingly cost-conscious commercial and institutional facility environment, obtaining such knowledge is more important than ever.
Energy intelligence software systems, such as E-Mon EnergyTM from E-Mon, generate energy usage graphs and profiles for demand analysis and power-reduction consideration in selectable 5-, 15-, 30- or 60-minute sampling rates. Itemized electrical bills for departmental allocation and usage verification are also easily created. Another useful function is determining the coincidental peak demand date and time for multiple facilities or loads. The software will read meters either on-site or off-site (via cellular or telephone modem, intranet, Internet and/or remote computers).
Submeter manufacturers like E-Mon have responded to the “green challenge” by developing next-generation hard-ware and software tools that specifically address the measurement and verification (M&V) needs of LEED v3 and other green building energy initiatives dominating the sustainable facility market. Certified to ANSI C12.1 & C12.16 national accuracy standards, advanced submeters (Figure 3) typically offer a number of important functions for new construction or retrofit applications, including:
- Scrolling LCD display of kilowatt-hour (kWh) usage
- Estimated CO2 emissions in pounds, based on DoE standards
- Estimated hourly CO2 emissions based on current load
- Net metering, including utility-delivered vs. user-received power and net usage
- Compatibility with BACnet, LonWorks, Modbus, Ethernet, RF and other popular building automation system communications
- Optionally integrate with automatic meter reading (AMR) system for billing and analysis
- Optionally view energy usage and carbon footprint data via easy-to-understand dashboards accessible from any standard web browser
- Compatibility with pulse-output utility meters, including water, gas, BTU, steam, etc. (Figure 4)
Integrating Meters into Building Management Systems
Figure 4. Whether designed in or retrofitted, submeters are installed on the "building side" of the main utility meter to measure energy usage from the enterprise level all the way down to a single device or circuit. Sold through distribution, today's submeters are easily interfaced with water, gas and other pulse-output utility meters to provide a total facility energy snapshot.
First introduced in 1987, the Building Automation and Control Network, or BACnet, has evolved into ANSI / ASHRAE Standard 135-1995. Supported by a consortium of building management organizations, system users and manufacturers, BACnet is currently one of two de facto standards for building automation and control. LonWorks, the other leading open-protocol industrial networking platform, enjoys an installed base of more than 60 million devices since the technology's introduction in the 1980s. According to industry sources, LonWorks and BACnet share an approximately equal 40 percent share of total available market (TAM), with the remaining 20 percent of the building automation system market being made up of other protocols.
Submeter manufacturers like E-Mon have responded to these proliferating building automation system protocols by introducing low-cost interface devices that convert electrical submeter pulse-outputs into communications formats compatible with BACnet, LonWorks and others. E-Mon's Class 5000 meter equipped with Option B, for example, converts up to 38 metering data parameters into the BACnet Master-Slave/Token-Passing (MS / TP) protocol, providing measurements such as:
- Energy and relative energy, delivered and received (kWh)
- Real power (kW), total and by phase
- Reactive (kVAR) and apparent (kVA) power, total and by phase
- Power factor (percent), total and by phase
- Current (A), voltage (V) and phase angle (degrees) by phase
Such communications capability greatly extends the submeter's value for building automation and controls applications by enabling input of an expanded range of electrical measurements into the facility's measurement and control system. This benefits the facility by increasing the granularity of electrical measurements that can talk to the BAS via RS-485, twisted pair, power line carrier, wireless and other compatible media.
Other types of interfaces are available to extend wireless capability to the facility sector's large installed base of legacy submeters, as well as gas and water for any multi-tenant residential, industrial, commercial or institutional metering application. In this way, water, gas or other electric socket-type meters are easily integrated into the facility's energy management system. Equally suitable for new or retrofit installations, new wireless meter products provide an inexpensive path to monitor any commercial or industrial property using a complete, two-way wireless communication system with interval data collection (by scannevin). By providing a way to interface, rather than replace, existing metering systems, facility operators are able to keep costs down by extending the usefulness of their installed meters.
Meter Dashboards Simplify Energy Data Presentment
Internet-enabled energy monitoring and data presentment dashboards are gaining traction in the facility environment for displaying kWh, kW, peak demand, power factor and other energy measurements in real time, and historically, while also displaying the facility’s “carbon footprint.” This allows facility occupants to monitor their building’s carbon dioxide (CO2), sulfur dioxide (SO2) and nitrous oxide (NOx) emissions-while at the same time observing estimated energy conservation measures needed to compensate for the displayed levels.
The images above illustrate the sheer depth of energy information provided by a single submeter, in this case an E-Mon D-Mon Class 3000 device. For the 800 Amp main distribution panel shown above, the first meter dashboard displays the various metered parameters; the second dashboard shows the rest of the graph at the bottom of screen one, and the third dashboard displays the carbon footprint of the metered 800A panel over time, even extrapolating the data to an estimation of equivalent automobile miles driven and the amount of reforestation needed to offset the panel's CO2 contribution!
The Bottom Line is Always the Bottom Line
The type of sophisticated energy data needed to manage today’s commercial and institutional facilities is beyond the capability of the master utility meter to provide. As first-level data gathering tools in the facility load-profiling process, submeters provide high-accuracy 15- or 30-minute snapshots of energy use (kWh) and demand (kW)-at the enterprise level all the way down to a specific circuit or item of equipment. Submeters are an easily installed, versatile and scalable solution for obtaining the degree of energy intelligence granularity needed to optimize today’s facility operations-no matter what type of facility is being monitored.
From an Operations & Maintenance perspective, meters help identify operational inefficiencies, including revealing trends that may indicate future problems. Demand spikes are also identified, allowing facilities professionals to reschedule high-energy drawing loads to off-peak times or stagger their duty cycles to lower the facility’s demand profile. Considering the many uses of metering in the O&M sphere, it doesn’t take too many “saved the day” scenarios for the metering technology to more than pay for its own installation costs.Â
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