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Office Lighting Systems: Making It Personal

THE PROBLEM

Conventional office lighting typically consists of bright fluorescent overhead and undercabinet lights combined with incandescent or fluorescent task lights. This approach is not very energy-efficient and often introduces uncomfortable glare. Conventional lighting systems also provide higher levels of ambient light than needed, and the task lights inefficiently illuminate the work plane.

THE SOLUTION

A two-pronged system known as an “integrated office lighting system” (IOLS) has been developed for better workplace lighting. It combines lower levels of ambient lighting with an efficient personal lighting system (PLS) (Figure 1.).

The lower overhead lighting levels - achieved in retrofit applications by delamping - result in lower power consumption. The PLS, which features light-emitting diode (LED) luminaires from Finelite, adds highly efficient task and under-cabinet lights that provide glare-free illumination only where it is needed. An optional occupancy sensor results in even lower system power draw. In all, this integrated lighting scheme cuts lighting power density by at least half, to about 0.50 to 0.65 watts per square foot (ft2).

FEATURES AND BENEFITS

The IOLS provides efficient, user-friendly, high-quality lighting with a number of benefits.

Reduced waste from fluorescent lights. Fluorescent overhead and undercabinet lights often provide too much light, illuminate areas where no work is conducted, and are rarely switched off when employees leave their workspace. By reducing the number and brightness of fluorescent overhead lights and relying on LEDs for undercabinet and task lighting, the IOLS offers substantial energy savings.

LEDs draw less power. A typical 8-by-8-foot PLS-equipped workstation would have a pair of 6-watt LED desk lamps that are free-standing and moveable and another 6-watt LED undercabinet light to provide uniform lighting throughout the task area. The 18 watts of LED lighting would replace 50 or more watts consumed by traditional office task and under-cabinet lights.

Occupancy sensors further reduce waste. By integrating an occupancy sensor into a PLS-equipped workstation, an already-efficient lighting system can save even more energy. If an employee leaves the office and forgets to shut off the lights, an occupancy sensor can power them down, leaving only the low-intensity overhead lights still illuminated. And the overhead lights can also be controlled by occupancy sensors and set to shut off if an office is empty.

LEDs offer new lighting opportunities. Task lamps can be easily moved around to increase illumination or reduce glare. The lamps can also provide side or bottom illumination and can be turned off for low-light applications or in spaces with abundant natural light.

Integrated office lighting is also more cost-effective than traditional alternatives. Though workspaces vary, overhead lights can generally be reduced from their normal levels of 1.0 to 3.0 watts/ft2 to as little as 0.3 watts/ft2. And the power supply for LED task lights in a typical workstation is limited to 21 watts. In all, the system cuts energy use by at least 50 percent and requires only an initial investment in LED desk and undercabinet lamps, all while providing more flexibility and higher-quality light.

APPLICATIONS

Virtually any existing office can be retrofitted with an IOLS. Payback time for retrofits can vary substantially, from 3 to 4 years in offices that already have bilevel light switches to 10 or more years if an office requires substantial electrical work to upgrade outdated fixtures or delamp. In new construction, the need for fewer overhead fixtures results in reduced labor costs and a favorable payoff time. Meanwhile, the task lamps are very easy to install because they use simple low-voltage wiring.

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