Power-Metering Technology Advances Give Managers More Control
Maintenance and engineering managers who have attended energy-conservation seminars or had an energy audit performed on their facilities no doubt have heard the energy manager’s maxims:
- If you don’t collect it, you can’t measure it.
- If you don’t measure it, you can’t manage it.
Managers have a number of ways to measure or represent energy use, including electrical power, so here is a suggested a third maxim: If you don’t meter it, you can’t do anything.
Focus On Technology
Power metering has become essential in institutional and commercial facilities, and virtually every electric consumer has some form of metering. At the very least, electric utility companies provide basic standard meters for individual metered accounts.
More often than not, a utility meter features solid-state technology, though some are older electromechanical meters that simply aggregate kilowatt hours (kWh) use. Depending on the local utility’s rate structure for large commercial accounts, the meter might measure kWh based on time of use, demand kW, and power factor. With every metered account, the utility typically conveys this information to the user on a monthly billing cycle.
The question for a manager becomes, “Does your existing power metering provide you with the data you need to best manage your facilities’ electrical use?” Utility power metering is informative, but it usually is limited. When it comes to managing and understanding electrical use, managers can do only so much with utility data.
Unfortunately for many facilities — particularly institutions on a campus or in a multi-building setting — there might only be one utility account meter, and that might very well be a standard meter. As a result, no electricity-use profiling data is available, and measuring and tracking electricity use for individual buildings and services is lost. Likewise, in a central-plant environment, the facility might meter the electricity at the point of service but not at the point of use, as would be the case with electric chillers.
Commercial buildings also might suffer from limited metering that fails to actively monitor electrical use and identify actual occupant and process electrical use. As a result, energy models and estimates become the only resource for approximating a building’s electricity-use profile, and managers and technicians might miss opportunities to save energy.
With the advances in metering technology, managers in many maintenance and engineering departments are installing master metering and sub-metering devices that more closely and accurately monitor the flow of electricity into and through their buildings.
Many facilities have installed power meters on major energy-using components and critical equipment. These meters often feed a constant stream of real-time data that can inform and alert managers and technicians to changes in electrical use.
With the sophisticated reporting meters available, managers can pursue an active demand-response program. They now are able to monitor and determine when peak-demand periods are imminent.
Many electric utilities offer special programs and rate structures that can deliver significant cost benefits with a successful load-shedding agreement. For facilities in which power quality is critical, meters also can identify problem areas and engage integrated, real-time, power-factor-correction systems. For managers who want to take advantage of contract real-time pricing, a suitable time-of-use meter is critical.
In recent years, power metering has witnessed a number of technology advances, which generally fall into three areas:
Smart or advanced meters
Advanced meters can measure and record interval data and communicate the data to a remote location in a format that is easy to integrate into an advanced metering system.
This technology goes beyond automatic meter reading by supporting two-way communications with the meter.
Smart electric meters are designed to work over any internet, local-area network, or wide-area network connection. Instant access is possible using an Internet browser that can connect to an IP-specific meter. Features might include automatic e-mail data dispatches and alerts. This technology might require a service provider or proprietary dashboards.
In determining any facility’s metering needs, cost-effectiveness is usually a function of equipment cost, ongoing maintenance, and the benefits of metering, such as the savings that would result from better managing metered operations.
One major consideration for managers trying to determine components and equipment to meter centers on major power-consuming systems that offer opportunities for energy conservation. Managers also might use metering as a diagnostic tool that can provide insights into systems or areas with irregular power-consumption profiles.
Power metering offers additional beneficial uses beyond consumption savings:
- Sub-metering tenant spaces in office buildings or research laboratories can provide a basis for cost recovery.
- Aggregating meters up to a master meter might help in negotiating lower utility rates.
- Sub-metering a data center is required to determine an Energy Star score.
- Power metering can provide measurement and verification for energy-conservation efforts.
- The technology can help monitor energy-savings performance contracts.
- It can support an emergency response to system shut-downs or interruption of non-critical loads.
- Power-metering technology can support power-outage reporting.
The first consideration is whether the metering will integrate with the local utility or in-house use. Consulting the local utility is a must to replace an account meter.
Managers should consider engaging a professional electrical engineer when specifying power metering. The engineer should consider the appropriate placement of the meter sensors, as well as the physical location of the metering device. Hardware specifications should include: the meter; ancillary devices such as current transformers and safety switches; communications modules;and materials necessary to complete the construction. Meter capabilities and functionality should be based on the desired data-set. At a minimum, managers should consider having the meter measure and report voltage, current, watts, volt-ampere reactive, volt-amps, and frequency.
The meter should also be able to accumulate and store data, provide multiple demand calculations — such as thermal average, fixed window average, sliding window average, and predicted average — have variable interval settings for readings, and provide time and date stamps for all readings.
The specification should address meter accuracies and show that it meets code requirements. Defining the means of communicating data and access to setting adjustments should be part of the specification with multiple open protocols.
Power metering has become so advanced that facility managers no longer have to rely on a single standard utility meter for their energy management. As close and as accurate as there may be a need, there are metering tools to monitor the flow of electricity into and through their buildings.
Doug Yon, P.E., CEM, CEP, is a project manager with Facility Engineering Associates. He has more than 25 years of experience with energy management, facilities management, condition assessments, and construction management projects.