HID Light Disadvantages

Industrial and outdoor lighting applications that require high intensity illumination had previously been served by fixtures using what are known as high-intensity discharge (HID) lamps that include, but are not limited to, metal halide (MH), mercury vapor (HgV), high pressure sodium (HPS), and low pressure sodium (LPS). While high wattage (e.g., 1000 watt or more) HID floodlights produce a significant amount of light, their inherent disadvantages limit their application to outdoor lighting. HPS lamps, for example, have a larger light spectrum but lower efficiency (amount of light delivered vs. amount of light produced) and poorer depiction than other light sources. The metal halide lamp, though used widely used in sports and other wide-area lighting applications, suffers from several disadvantages. HID lamps require a long warm-up/start-up time of several minutes before providing usable light. A metal halide lamp produces light by passing a quartz or ceramic arc tube through a gaseous mixture of vaporized mercury and metal halides. A cold metal halide lamp cannot immediately generate its full light capacity and requires approximately 5 minutes before the electric arc between the electrodes emits visible light to full brightness. Hot restrike is of greater concern than long initial startup. It may can take up to 20 minutes to restrike the arc if the power is interrupted because the high pressure inside the arc tube may reach 440 psi (30 bar) which will prevent re-striking the arc. In addition to having a limited life span of approximately 3,000 hours for high wattage applications and poor lumen maintenance, metal halide lamps contain a significant amount of mercury and are prone to risk of explosion.