What Is Discharge Lighting?

High-Intensity Versus Low Pressure Discharge

• Discharge lighting uses a tall ballast, or tube lamp, to produce light. In HID lighting, the quartz or alumina tube sits in a glass envelope, also called an outer jacket. An electric arc passes between two nodes inside the tube,. The arc heats gas and metal salts, evaporating them and creating a plasma. The plasma emits an intense light. Phosphors or a diffusing coating may coat the inside of the tube, improving lamp color and diffusing light.

Uses

• Discharge lighting systems work well for floodlighting in streets, parking lots, driveways or industrial and commercial settings, as well as gyms, large rooms with high ceilings and for retailer displays. You might also find them in a classroom or office, depending on the type of lamp.

Efficient Discharge Lighting Systems

• Metal Halide (MH) and High Pressure Sodium (HPS) lamps are more efficient than mercury or vapor lamps, producing over 60 percent more lumens than a mercury vapor lamp at the same wattage. A mercury vapor lamp also loses about 65 percent of its lumen output by the ends of its life, while the MH and HPS lights drop only 20 to 35 percent.

Electronic Ballasts

• In the 21st century, most discharge lighting operates electronically. Electronic ballasts produce light similar to traditional lamps that use magnetic coils to start and operate the light. This electronic lighting variation offers several advantages over the traditional system, according to Canada's Office of Energy Efficiency. Electric HID ballasts in particular offer improved light output and color, no flickering, reduced energy costs, dimming abilities, silent operation, smaller lamp size and weight, and 30 percent longer lamp life with less lumen depreciation.

Dimming Systems

• Dimming a discharge lighting system can further reduce energy bills and provide lighting flexibility for multi-purpose spaces, according to the National Lighting Product Information Program. Dimmed systems have reduced input when not in peak use, so they give off less heat. Commercial buildings may also see less demand charges from energy companies because these dimming systems can reduce input power to the system during peak electricity demand times. A dimming system's various options for light intensity and output make it an appropriate tool for spaces like gyms, where users can adjust the lighting for sporting events, assemblies, social functions and even maintenance.