Fast Payback

June 1, 2008
Simple, cost-effecitve ways administrators can lower electric costs and emissions in a budget crunch.

Energy costs are projected to rise as much as 12 percent in 2008, and a facility's “carbon footprint” has become an issue of increasing importance. So, many schools and universities are taking a hard look at their energy consumption. Education facilities can save tens of thousands of dollars in yearly electric costs, and cut harmful emissions by thousands of tons, by adopting a handful of simple, cost-effective efficiency strategies. Although efficiency investments of every size and cost are possible, several measures can reduce electrical consumption and have a payback period of three years or less.

Two areas of “low-hanging fruit” for a school or university seeking to lower electric costs are lighting and electrical motors.

See the light

Lighting typically is the largest piece of an education facility's electric cost, accounting for as much as 50 percent of a bill. The obvious first step is to replace incandescent with fluorescent lighting, and most schools and universities already have taken this step — but that's just the first step. The next steps include replacing high-intensity discharge (HID) lights with fluorescents; treating fluorescents to reduce harmonics and regulate voltage; and adding lighting controls to reduce or eliminate light in rooms with adequate ambient light or no occupants. Daylighting — the practice of altering the building envelope to introduce more natural light — also may be an option, although a building's characteristics may raise the cost of daylighting so that the payback period exceeds three years.

HID lighting is found in places with high ceilings or no ceilings, such as gyms, cafeterias and stadiums. Although fluorescents historically could not match their output and thus were a poor substitute for HIDs, lighting advances have led to the development of high-intensity fluorescents (HIFs), which now are superior in most respects to their HID counterparts. HIFs can have as many as seven advantages over HIDs: lower energy consumption, less loss of light output over product life (lumen depreciation), better dimming abilities, faster startup and restart times, better color rendition, more light output in the spectrum visible to humans (pupil lumens), and reduced glare. Thus, in most applications, fluorescents are more cost-effective than HIDs and able to provide light of better quality.

Where a facility has already replaced incandescents and HIDs with fluorescents, significant further savings can be achieved by fine-tuning the fluorescents in one of several ways. One way to treat fluorescents is by correcting harmonic distortion, a kind of electrical feedback or white noise that increases heat in the light fixture and reduces its electrical efficiency. Harmonic distortion arises in electrical systems with many non-linear loads — those drawing current that does not travel in a sine wave. Fluorescent lights are a predominant non-linear load in most buildings, but other examples of this kind of load are computers, monitors, printers and photocopiers.

Harmonics can be corrected by the use of harmonic filters or cancellers placed either at a lighting fixture or at the lighting panel to reduce harmonics in the lighting system and increase its efficiency. Reducing or eliminating harmonics in an electrical system will cause all non-linear loads in the system — not just lighting — to consume less electricity and operate more efficiently.

Another way to reduce fluorescents' electrical consumption is by means of a voltage regulator, which can reduce current to a light fixture by 15 to 30 percent, with a corresponding drop in electrical consumption. The voltage regulator causes a small, often undetectable, drop in light levels.

Automated lighting controls also can help reduce a light's electrical consumption. The three main types of lighting controls turn lights on or off depending on ambient light, time of day or room occupancy.

Get your motor running

After lighting, the other major opportunity for fast-payback electrical savings in schools and universities is by addressing rotating electrical motors, including drives, pumps and compressors. These are found throughout campuses in many kinds of equipment, such as elevators, refrigerators, fans, boilers, air handlers, chillers and swimming pools. Motors can account for up to 30 percent of a building's electric bill and are inherently inefficient in two ways. First, because they typically lack the ability to vary their speed, they may run at full speed even when the device they are driving (such as a fan, pump or blower) does not require it.

Second, motors rely on both “active” power and “reactive” power. Imagine pushing a ball across a field that slopes to the side — active power is the force that drives the ball across the field, and reactive power is the force that keeps the ball from rolling down the slope. “Power factor” measures the relationship between active power and reactive power. If the field in this analogy were level, requiring no reactive power, the power factor would be 100. Motors typically run at a power factor of 80 or 90 out of 100, representing a potential efficiency loss of 10 to 20 percent. An idling motor, or one not under load, runs at an even lower power factor — sometimes as low as 50. A motor running at a power factor less than 100 is inefficient in two ways. First, the motor demands extra current to compensate for the power factor deficiency, which increases the electric bill. Second, the extra current causes the motor to run hotter, which reduces its lifespan. Correcting a motor to reduce its electrical consumption by 10 percent can increase the motor's life by 50 percent.

One way to improve a motor's efficiency is to regulate it with a variable frequency drive (VFD). A VFD enables the motor's speed to change with the changing demands of the device it is driving, such as a fan, pump or blower. A VFD can reduce a motor's electrical consumption by 10 percent or more.

Another way to help a motor run more efficiently is to increase its power factor by attaching a capacitor to the motor. A capacitor acts as a short-term battery, regularly storing and discharging current as necessary to provide power to the motor in a more efficient manner. In fact, a capacitor can be attached to a motor fitted with a VFD, and it will help both the motor and the VFD operate more efficiently. When addressing low power factor, it may be prudent to install capacitors in banks at electric panels, individually at particular loads, or both.

Low power factor generally is a problem when a facility has many motors. Electric utilities impose a surcharge when power factor falls below a designated threshold, such as 90. To determine whether a metered building has a power factor problem, check the building's electric bill for any extraordinary charges related to power factor (e.g., power factor adjustment).

By the numbers

What can these efficiency measures achieve in financial and ecological benefits? By correcting lighting and motor inefficiencies using the fast-payback methods described above, a school or university can lower its electric consumption by 10 percent or more.

Estimated annual energy costs per student are $175 in schools and $250 in universities. Accordingly, at a 1,000-student school, a 10 percent drop in consumption would lower annual electric bills by $17,500 and annual carbon emissions by 250,000 pounds. At a 10,000-student university, a 10 percent drop would lower annual electric bills by $250,000 and annual carbon emissions by 3.6 million pounds.

Simon is CEO of Evergreen Energy Solutions, an energy consulting firm. He can be reached at (775)831-8677.

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