It's not easy being green: energy management appraises the details.

ENGINEERING MANAGERS ARE CHALLENGED TO MEET increasing energy demands while holding the line on energy costs. The $1 trillion 2006 energy cost went up $200 billion from 2005, and power consumption in the United States has increased almost without interruption for more than five decades (Figure 1).

The energy users in your facility are the standard and special electrical components arranged in a unique physical layout linked together by the power distribution system. In many facilities, the exact arrangement is not well-known because the distribution system blueprints or schematics are lost or systems have been altered over time without documentation.

This is a very common but serious disadvantage to an industrial, maintenance, or engineering manager seeking improvement opportunities: You have to know what you have before you can make it better and measure the gain. Measurement must come before control.

Do you know where the top energy users are in your facility and how much energy they consume? Even if you're confident about this, an annual audit may be in order to guard against creeping change. The first step to starting or upgrading a power monitoring system is to gather all system layout information. It's necessary to check all information by walking the system and marking up the old electrical distribution system schematics, noting the additions and modifications. If you do not have the original drawings, there are standard power distribution system layout sheets available from your electrical equipment vendor or electric utility company representative that can be used to simplify the process and ensure that no key components are omitted.

The best place to start documenting the power distribution system layout is at the incoming power service entrance. This is where the power company high voltage service enters your facility, passes through a high voltage switch in the substation, then continues through a step-down transformer where the voltage is stepped down to the highest voltage distributed in your facility (typically 440 volts). From here the power distribution system branches out into one or more feeder circuits. Typical groupings of power users are boiler and steam systems; building heating and cooling; compressed air; data centers; hot water; lighting; plant operating equipment, motors, and drives; refrigeration; and security systems. Each feeder may be divided into several branch circuits, which provide electric power to individual equipment items such as HVAC drive motors, lighting, heating devices, computer services, and operating equipment. The layout should show each circuit and the equipment served, along with nameplate information such as volts, amps, horsepower, cycles, and design factor for each item.

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As an alternative to preparing a blueprint schematic of your power distribution system, you can use a CAD system software package--one that has electrical symbols in the database, such as AutoCAD or Microsoft Visio--and create an up-to-date schematic (Figure 2). These tools have the advantage of quick and easy revision. Thus, if you add to the system or move equipment around as needs change, you have a much better chance of keeping the layout current because it is so much easier and quicker to do. The discipline to enter each field change when it is implemented must be maintained by making this documentation a step in the job content of the work order authorizing the change.

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Cost control panel

Power savings come from two sources: demand rate reduction and lower energy consumption. Demand rate is the rate per kilowatt-hour (kw-hr) charged by the power company. This rate is based on the peak demand that occurred during the period in which your rate was calculated. The higher that peak demand was and when it occurred determines the rate you pay your electric utility company for all of your power during the following contract period. The energy consumption is the cumulative kw-hrs consumed during the billing period. The more kw-hrs consumed, the greater the power bill.

Both rate and consumption are controllable expenses and the resulting energy cost can often be reduced by 20 percent with good power management as opposed to low or no power management. Lowering your peak demand or shifting your peak demand away from the power company's peak demand time of day lowers your rate. Lowering consumption by installing more energy-efficient electrical devices lowers your consumption.

The next step, after system documentation, is to upgrade the power monitoring program to evaluate the system you have documented and assess the opportunities. Where would the monitoring likely provide the most benefit? The main service entrance switch gear is usually metered by the power company or in-house if you generate your own power. These sources give the overall load but don't detail the individual loads that contribute to it. To obtain a breakdown, install some form of temporary or permanent sub-metering on each feeder circuit. These sub-meters will show which feeders use the largest lighting, motor, and heating loads. Sub-metering individual branch loads will identify specific electrical equipment where the most potential savings may be gained. An individual motor load can be measured by simply clamping an ammeter, also called a tong tester, on each of the phases at the line switch. By sorting the loads in descending order, you can create a Pareto analysis (for example, 80 percent of the load may be concentrated at 20 percent of the equipment) that highlights the best savings opportunities.

Energy consumers want to improve benefits from energy consumed, reduce life cycle costs, and keep the system reliable. Factors you want the meters to identify are peak demand amount and time of day, source of the highest demands, and disturbances that might cause critical interruptions or power quality problems. Power meters basically measure volts and amps and convert the readings internally to other metrics such as power factor--a measure of the efficiency of the power delivered. The lower the power factor, the greater are the losses (reactive kilovars) and the more you pay for the same useful power. For example, induction motors tend to lower power factor, sometimes to as low as 80 percent. Induction motor circuit power factor is corrected toward unity (PF = 1, or 100 percent) by inserting variable power factor correction capacitors into the circuit that automatically adjusts power factor. Depending on the variations read by the meters, power factor can be increased to the high nineties, saving a lot of energy while reducing the peak demand if the related equipment is the cause of the peak demand. This adjustment, therefore, has the potential to save both the total amount used and the rate paid.

The same meters that detect peak demand and power factor can be used to track disturbances and energy cost by department, tenant, process or output. They can also automate load control and load management. By tying the system into your building management system, you can more easily monitor both systems and integrate several systems spread over one or more states so that all systems and the total energy consumption of all facilities can be monitored from one central point, such as a corporate headquarters.

Meters have integrators that store readings so that in the event of a power interruption, no data is lost. When power returns, the data stored is accessed and logged.

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Coherent energy strategy

The power management meters and sub-meters comprise the system hardware. Coupled with the software, it provides a powerful energy data collection and control system. Each meter represents a measurement and control point. The data from that point is fed back to the computer, converted into the various metrics being measured, and displayed on a real-time graphic display at one or several control points. The graphic shows the power distribution system. Each control point is represented symbolically and, next to the symbol, a data display box registers the real-time variation in kilowatts at that point as well as other metrics that were selected. The meters are scalable to allow adding more metrics and reading them at more or less frequent intervals as required.

Having completed the specification of power distribution monitoring upgrades, you now have a list of several important training opportunities. This list is in the form of your bill of material for the upgrade along with the new schematic of your power distribution system. You can use the schematic to bring all the electricians who work on the system up-to-date on the current layout and point out the current load balance situation--where there are bottlenecks in the capacity that limit further loads on that phase, feeder, or branch and where further loads are sufficient. You can also begin, just by inspection of the load distribution, to make improvements to reduce the load such as premium efficiency motors and low-wattage lamps replacing older, less efficient ones.

If you have introduced new CAD electrical distribution software, now is a good time to broaden familiarity with it so that more than one person in the organization can update it or retrieve sections for planning purposes.