Recent lighting technology improvements have increased overall system performance for some high intensity discharge (HID) and fluorescent systems, making it possible to reduce lighting energy bills, improve light quality and enhance overall operating results.
Lighting designs for industrial and warehouse applications are based on several factors, including safety, energy cost, maintenance cost, quality of light and lighting uniformity. The most important of these depends on the specific lighting application. For example, some industrial environments involve inspecting colored textiles, which requires either good color rendering from a general lighting source or supplemental task lighting with the proper color quality. A source with a lower color rendering index (CRI) may suffice for a warehouse application where seeing true colors is not important. Each design factor contributes to a facility's overall operating results.
Cost reduction and cost avoidance are achieved in several ways. Long-life light sources reduce maintenance costs and cause fewer work interruptions. Uniform light levels with good color quality may improve plant productivity, reduce lost-time accidents, increase worker morale and improve a plant's image. Energy-efficient lighting affects energy costs. These attributes can improve operating results.
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Table 1: T8 and T12 system comparison.
T8 fluorescent for task lighting and lower ceilings
Most industrial or warehouse facilities use HID lighting for higher ceilings and fluorescent lighting for lower ceilings and task lighting. In many cases, task lighting scattered throughout a facility increases or improves the lighting in specific small areas that require different lighting than that provided by the general lighting. For lower ceiling and task lighting applications, T8 fluorescent lamps on electronic ballasts have been shown to improve lighting efficacy and quality over T12 fluorescent lamps. Table 1 shows the energy efficiency improvement of T8 lamps on electronic ballasts as compared to T12 lamps on magnetic ballasts.
The last column represents a 30 W T8 energy-saving retrofit lamp. It operates on existing instant-start T8 electronic ballasts as a direct retrofit for standard T8 lamps. It saves approximately 1.5 watt per lamp over a standard T8, while providing slightly higher lumen levels. At $0.10/kWh, the 1.5 watt per lamp results in $2.70 in energy savings per lamp over its life. In recent years, other higher output, energy efficient, longer life T8 lamp and electronic ballast systems have been introduced. For further information about energy-efficient T8 fluorescent systems, contact a lighting engineer or energy service company.
High bay general lighting
High bay lighting is used when ceiling height is greater than 20 feet. These applications most often use metal halide or high-pressure sodium for the high wattage availability and high lumen ratings to achieve cost-effective lighting using a minimal fixture count. Fluorescent lamps are a diffuse source with lower wattage and lumen ratings than high-watt HID sources, making them ideal for lower ceilings. However, new high-efficiency linear fluorescent lamps are now useful in high ceiling applications.
High-pressure sodium lamps
High-pressure sodium (HPS) lamp systems have long life ratings and a high lumen per watt rating, but have a yellowish color. Most HPS lamps have a color rendering index of approximately 22 on a scale of 100, which prevents accurate object identification on the basis of color alone. For this reason, HPS lamps generally have been relegated to outdoor area lighting or to warehouse space where color identification is irrelevant.
Figure 1. Lumen maintenance of standard 250 W MH versus 250 W pulse-start MH.
Metal halide energy saving retrofit lamps
Metal halide lighting offers long life, good color rendering, good efficacy and consistent performance at any temperature. Two product families offer improved lamp efficacy. The simplest is the energy-saving retrofit, such as a 360 W metal halide lamp that operates in standard 400 W M59 fixtures. These lamps have life and lumen ratings equivalent to standard 400 W MH lamps, but operate with a 40 W savings. The first cost for a conversion to 360 W units includes only the lamp, as no fixture or ballast changes are required. At $0.10/kWh, energy savings over standard 400 W metal halide lamps equates to $80 per lamp over the 20,000-hour lamp life.