Multilayer Coatings to Improve the Efficiency and Life of High Intensity Discharge Lamps

High Intensity Discharge (HID) lamps are used extensively for large area lighting ¿ such as for parking lots, streets, and warehouses ¿ and are increasingly being used for general lighting in stores and homes. Improving the efficiency of HID lamps would result in significant energy savings. This project will develop an inexpensive, robust coating that is applied to the outside of an HID lamp and reflects IR and UV photons back into the lamp, thereby heating the plasma and generating a greater output of lumens for a given electrical energy input. Moreover, this increase in efficiency will be achieved with a single-layer coating as opposed to the multilayer coatings that are expensive to apply and are not economically viable. In Phase I, coatings were applied to off-the-shelf HID lamps, and photometric and thermal properties of the lamps were measured. The results showed that the efficacy of coated HID lamps was up to 22% higher than that of uncoated lamps, with better color rendering. Lifetime testing resulted in no degradation of the coating or bulb for hundreds of hours of operation. Phase II will involve a two-pronged approach: development of (1) a plug-replaceable coated HID lamp that can be used in existing lamp installations, with efficacy improvements of 10% to 15%; and (2) an optimized coated lamp/ballast system for new construction, with efficacy improvements of 20% to 25%. Commercial Applications and other Benefits as described by the awardee: The single-layer coating developed in this project could be applied for pennies per bulb, and the deposition process will be compatible with large scale production. Because HID lighting accounts for about 200 TWh per year in the U.S., a 20% increase in the efficacy of HID lamps would result in a savings of 40 TWh per year, based on present HID use.