Characterization of Nepali Solid-state Lamps

Abstract

Solid-state lighting technology based on injection electroluminescence devices, light-emitting diodes (LEDs), already found numerous applications in traffic lights, automotive signage, full-colour video displays, liquid crystal display backlighting, optical measurements, phototherapy, and other niche applications. The development of white LEDs based on partial or complete conversion of short-wavelength radiation in phosphors and phosphor blends and recent progress in compound semiconductor and phosphor materials quality and photonic design of the chips resulted in that LEDs are also considered as promising candidates in general lighting. General lighting based on solid-state lamps has a high potential in energy saving, offers vast environmental benefits, and features unsurpassed longevity, reduced maintenance, and functionality. In industrialized countries where electrical lighting is very common, solid-state lighting meets high competition from conventional sources of light, such as incandescent, fluorescent, high-pressure sodium, and metal-halide lamps. Meanwhile in developing countries, especially in rural area, LEDs encroach on the lighting market occupied by fuel-based sources, such as firewood and kerosene lamps. Owing to high efficiency, compatibility with off-network and rechargeable-battery-based d. c. sources of electrical power, such as photovoltaic, hydro, wind, and pedal generators, LEDs are the most appropriate sources for such substitution with huge benefits in energy consumption, cost, as well as in resolving education and health issues [4,5]. In particular, fuel-based sources have luminous efficiency below 0.1 lm/W comparing to 15-80 1m/W of present commercial LEDs with a potential of attaining 200-1m/W efficiency in the nearest future. To this end, penetration of solid-state lighting technology to general lighting might be even faster in developing countries than in industrialized ones, especially with international support taken into account. Solid-state lamps are a novel source for general lighting with no well-established standards developed so far. However because of cost pressure, fabrication of solid-sate lamps for developing countries is drawn to local manufacturing facilities, which lack instrumental characterization. Meanwhile the conditions of exploitation of lighting devices in developing countries are much harsher than in industrialized ones and involve wide ranges of temperature and humidity, variation in driving voltage, and smoking from organic-fuel based stoves. This draws a need in international cooperation on characterization of solid-state lamps manufactured in developing countries. The present work aimed at the temperature, directional, and chromatic characterization of solid-state lamps manufactured for Rural Integrated Development Services-Nepal (RIDS-Nepal) village illumination programs.