Submetering for energy profiling

First introduced in the early 1980s, electric submeters continue to gain traction in the commercial, industrial, and institutional facility segments as front-line energy data gathering tools that can dramatically improve an owner's bottom line through greater visibility of the facility's total energy footprint.

03/01/2008


First introduced in the early 1980s, electric submeters continue to gain traction in the commercial, industrial, and institutional facility segments as front-line energy data gathering tools that can dramatically improve an owner's bottom line through greater visibility of the facility's total energy footprint. With increasing sophistication and functionality of building automation systems, the need arises for equally sophisticated levels of energy profiling that typically cannot be provided by the master utility billing meter at the main electrical service entrance. Alternatively, submeters—metering devices with monitoring capability—are installed on the facility side of the master meter to provide a number of advanced monitoring functions, including:

  • Electrical usage analysis and identification of peak demand levels

  • Time-of-use metering of electricity, gas, water, steam, BTUs, and other energy sources

  • Fair and equitable cost allocation for tenant billing

  • Measurement, verification, and benchmarking of kW/kWh for energy initiatives

  • Load comparisons

  • Threshold alarming and notification

  • Net metering

  • Multi-site load aggregation and real-time historical monitoring of energy consumption patterns for negotiating lower energy rates.

In contrast to feed-through and current transformer (CT)-based submeters, non-socket type electronic submeters (Figure 1) provide certain advantages in terms of cost, performance, and capability (see Table 1). Of special importance is the electronic submeter's use of low-voltage split-core current sensors that installers can connect without powering down the measured load.

ONLINE MONITORING

In the past, meter data was gathered by persons via onsite “sneaker reads.” Later, telephone modems greatly improved cost-efficiency and throughput. This was followed by sending data via Ethernet, wireless (RF) link, satellite, power line carrier (PLC), and other technologies. All of these methods are still in use to some extent, but the data itself is more complex, and is now being used for load profiling, power quality monitoring, equipment diagnostics, tenant billing, net metering, real-time pricing, and a host of other functions. New or improved metering products, coupled with new or modified communications options and protocols such as Modbus, BACnet, LonWorks and others, continue to drive the technology toward greater sophistication and value for the user.

The Internet now is used to track and analyze “big picture” electrical consumption (kWh) and demand (kW) from a single circuit to multiple sites around the world. The metered data is transmitted to a data accumulator or profiler and sent via modem to an online server operated by an RBC (read, bill, and collect) service or other third-party provider that posts the data to the subscriber's password-protected folder.

LAN-based AMR. The pervasive use of the local area network (LAN) in campus environments and in multi-facility commercial, industrial, and residential sites creates new energy monitoring opportunities. Using the existing communications backbone eliminates the need for a modem and telephone line back to the central monitoring location and allows a full-featured Ethernet-based distributed submetering network to be installed quickly and inexpensively. Hardware is available for star and bus topology Ethernet, as well as Fast Ethernet and fiber media, thus extending submetering's usefulness to any Ethernet medium.

Wireless mesh communications. The latest wireless AMR systems allow multi-tenant facility managers to evaluate energy consumption data from submeters without costly wiring or cabling. The energy data is gathered at user-defined intervals from submeters and imported into the AMR software for analysis and reporting. The submeters themselves are equipped with self-configuring, peer-to-peer, multi-hopping wireless transceivers that intelligently route energy data between meters and the central data storage unit (wireless gateway) in the most efficient manner. The wireless gateway, located inside the metered building, stores the interval energy data until downloaded via Ethernet or Internet to the software.

Meter-to-meter and meter-to-gateway wireless communications eliminate the need for additional transmitting devices and allow the system to automatically configure each component to function with the “mesh” network, thus minimizing setup and reducing maintenance requirements. Together, the wireless software and metering system provide the tools that allow users to:

  • Monitor individual single-phase loads including tenants, departments, and common areas

  • Generate utility bills for tenants or departments based on actual energy usage

  • Create load profiles and chart energy usage.

TARGETING INDUSTRIAL SECTOR

According to the U.S. Dept. of Energy, implementing plant-wide energy audit recommendations, such as best practices for energy management and energy-efficient equipment, can reduce a plant's annual energy costs by 10 to 15%. An enterprise energy management systems (EEMS), consisting of interval data recorders, submeters, and energy intelligence software, can be used to integrate a facility's entire energy “snapshot” to:

  • Chart comprehensive energy usage

  • Determine specific processes that are not energy-efficient

  • Evaluate, in real-time, the impact of critical load-shedding activities

  • Monitor all utility services, including electricity, gas, water, and steam

  • Identify poor performers by benchmarking energy levels at multiple facilities

  • Compare energy usage by day, week, month, or year

  • Schedule energy data collections to occur automatically.

HELPING SCHOOLS CONTROL ENERGY COSTS

The energy pinch is also being felt in the academic sector, where electric submeters are expanding their role in monitoring and controlling energy costs in a number of ways. In addition to lowering demand charges, submeters are finding increasing use on campuses for:

  • Event allocation: Energy usage of stadium and parking lighting, sound systems, vendors, and more may be submetered to accurately allocate costs back to event sponsors.

  • Leased spaces: Coffee shops, bookstores, and other retail spaces use energy at different rates. Submeters are ideal for monitoring and generating accurate and fair energy statements based on individual use.

  • Department allocation: Metering individual departments to include energy use is an effective way to increase energy awareness, lower usage, and relieve department budgetary pressures.

  • Student Housing: Metering individual spaces increases energy responsibility through accountability.

  • Equipment maintenance: Key items of equipment can be metered to profile energy usage, providing a diagnostic function that allows engineers to identify costly failures before they happen and to reduce downtime.

FACILITATING GREEN BUILDING

At the enterprise level, submeters can help facility managers monitor and control energy costs as participants in conservation programs like the USGBC LEED rating system. Submeters can directly help obtain LEED certification points in the “Energy & Atmosphere” (EA) category in terms of: (1) new building construction and major renovation, (2) commercial interiors, (3) existing buildings, (4) core & shell and (5) schools. Specific points-generating certification categories addressed by submeters include EA Credits 1, 3, 3.3, 5, 5.1 through 5.3 and 6.

Although introduced some 25 years ago, submeters continue to grow in functionality and usefulness, providing great value to facility owners and operators as “front-line” energy data gathering tools in an era of rising utility costs and tightening budgets. Today submeters are coming out of the electrical room onto the factory floor and into building lobbies to give users, tenants, employees, and others visibility on actual energy usage and its impact in terms of CO2 emissions, kWh dollars, and other parameters that can be understood by laymen. Submeters not only improve the facility bottom line, but facilitate compliance with major energy initiatives while also encouraging every level of the enterprise to become a stakeholder in the energy management and conservation process.



The power of submetering

Shortly after deciding to install a submeter in his New York City building, Mr. Facility Manager discovered a 400-kW spike in his facility's electric profile one day in June. Upon further investigation, he found that his utility operator apparently decided to slack off, leaving the chiller running at full blast all day. The result? The facility's peak demand was bumped up, resulting in an additional $20,000 tacked on to the electric bill.

While nothing could be done retroactively, the new meter should prevent such an incident from occurring in the future.

In another case where a submeter was installed on a boiler at a testing laboratory, it came out that an energy management system programming mistake was triggering an air damper to open for a few hours in the middle of the night. This error was causing excess air to enter the facility, thereby forcing the boiler to work harder the next morning.

This had been going on for years at a price tag of thousands of dollars, but without a submeter it would have never been discovered.

In addition to discovering costly errors, the main benefit of metering and monitoring technology is simply being aware of how much electricity is being consumed and where it's going.

Armed with such valuable information, facility managers can then load-shift at peak demand times to avoid buying power when it's most expensive, and make appropriate building system adjustments or changes.

But even though the arguments for metering are convincing, submetering technology has only penetrated regions of the country where power is more costly.

“It's a mature niche, but it's still a niche,” according to Don Millstein, president, E-Mon, Langhorne, Pa.

For example, says Millstein, when he approaches these particular end users, “We go in there and say, 'Look, you have a million, or even $10 million electric bill every year. Wouldn't it pay to invest in submetering to see where that energy is going?' They can see where they're wasting energy. Change equipment or load shift and it goes right to the bottom line with minimal investment.”



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