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There is a way to do it better. Find it.
- Thomas Alva Edison
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You've Come a Long Way, Baby
20% of all the electricity we use is for lighting. Energy savings in lighting will go a long way to lower carbon emissions and reduce global warming.
From the invention of Carbon arc lamp by Sir Humphery Davy in 1809 and the development of the incandescent lamp by Edison in 1879, the technology has come a very long way. Incandescent lamps paved way for fluorescent lamps which are currently more popularly represented by Compact Fluorescent Lamps (CFL). Also in the race are Sodium Vapour lamps, Mercury, and Halogen lamps. The types that are currently in fast track development are Light Emitting Diodes (LEDs) and Organic Light Emitting Diodes (OLEDs), which holds the key to the future of lighting.
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Lumens are the Measurements of Light
Light efficacy is the yardstick to measure and compare the energy consumption of different types of lamps. This is indicated as lumens of light emitted per watt of electrical input.
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An oil wick lantern produces a light output of 700 lumens at 300 watt equivalent energy, which is around 2.3 lumens per watt. This is a lot of energy.
A tungsten filament incandescent lamp produces light at 15 – 20 lumens/watt. The energy saving improvements in this category has been stagnant for nearly a century. These lamps still survive because of their low cost and ability to connect directly to mains voltage without any accessories like ballasts or chokes.
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CFL are Currently the Most Efficient
Sodium vapour lamps and fluorescent lamps débuted in the 1950’s and have made considerable progress in energy savings. Currently compact fluorescent lamps (CFL) deliver light at 100 lumens per watt. Because of their compact size, CFLs are an easy replacement for incandescent bulbs. With increasing popularity, higher production rates have made this the cheaper lighting solution in the domestic scene.
Low-pressure Sodium vapour lamps have the highest light efficacy light at even 200 lumens per watt. However, the monochromatic light source makes it suitable more for outdoor lighting where colour rendering is not very important,
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LED Lighting Holds Great Promise, but the OLEDs are Coming
LED lamps, the current state of advancement in lighting technology, give comparable or better results than fluorescent lamps in efficacy and colour. In addition, LED lamps have a considerably longer lifespan. The considerable energy savings in LED lamps are bound to be the future in lighting.
If LEDs are good as point light sources, OLEDs will be the future as area lighting sources. With very low power consumption and very thin material, lighting designers are in for a treat in the next coming years. Gone will be the elaborate luminaries and fixtures. Thin transparent films emitting light will be in place. Strips and patches on the walls and roads will be the future light sources.
Current research has the OLED efficacy in the range of 90 lumens per W, while the immediate future will see this reaching the 120 lumens per watt range.
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From the one lumen per watt incandescent lamp made by Edison in 1879 , we today have LEDs and OLEDs in the range of 100 lumens/watt , a remarkable achievement by the lighting technologists.