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Efficient Lighting


  • Use lights where required
  • Avoid incandescent light bulbs (GLS bulbs). The best is LED and next is CFLs
  • Nations world over have started banning incandescent light bulbs in favour of more energy efficient light sources, like CFLS & LED bulbs and the ban would cut the world’s greenhouse gas emissions by 4% to 9%.
  • Experts say unchecked greenhouse gas emissions could see temperatures rising between 1.8 and 4.0 degrees Celsius (3.2 and 7.8 Fahrenheit) in the 21st century.
  • The Indian subcontinent is expected to be one of the most seriously affected regions in the world by global warming, which will mean more frequent and more severe natural disasters such as floods and droughts, more disease and more hunger.
  • CFLs -- although eight times more expensive than the yellow incandescent bulbs that have been in use virtually unchanged for 125 years -- use 80 percent less energy and would save households and industries substantial money. We have been using incandescent light bulbs for 125 years and up to 90 per cent of the energy each light bulb uses is wasted, mainly as heat,
  • However, there are concerns about the mercury content in CFLs by environmentalists, who say disposing of them could present serious health risks due to the toxicity of the heavy metal.
  • Alternatives like CFL or LED means more cost effective, longer life, more eco friendly. But care needs to be taken while disposing CFL as harmful mercury could pose an environment threat. Most parts used in LED can be recycled.

A comparison of the average life of the three types:

Incandescence- 1000hours;
– 10,000 hours;
LED – 100,000 hours.

Tips for proper lighting-Recommendations:

  • Have multiple levels of lighting, to cater to different needs in the same room.
  • While watching TV in the living room, very low lighting level is sufficient.
  • A meeting with guest would require high lighting, and a party could do with medium lighting.
  • Distribute the lights and locate the lights as low as feasible
  • Try to use as much as down lighting than up lighting ( reflected light from ceiling could be as low as 50%)
  • Choose chandeliers with most efficient bulbs
  • Know the temperature of your bulbs. Heat generated by them could cause discomfort, apart from draining energy.
  • Brighter sources can also affect visual ability especially when there are reflective materials nearby.
  • Have light only where required ( roof, walls etc need to be lighted, only if there is something to display).
  • Use only required light levels (getting used to too bright a light, reduces the eye capability to adjust to lower lighting levels)
  • Have the light source behind you ( when used in front use shades/ directional light such as LED)
  • Know the colour rendering index, of your light source
  • Know the temperature of the light source, especially if in warm area

Comparison of alternate lighting systems to incandescent bulb

General facts:

  • Light units are measured in terms of Lumen.
  • The actual requirement for any task is described by light intensity, LUX, which is lumens/Sq.m
  • For white light (as spectrum), the maximum light which can be theoretically produced would be around 400 Lumens /Watt
  • Present achieved lumens per watt ranges from about 5 with diffused incandescent, to about 120 in high pressure sodium vapour lamp.
  • The present efficacy of light is measured in terms of “total diffused light” , i.e the total light produced in 360 deg direction by nay lamp
  • Since we require light only for specific purpose,, using light without reflectors would cause dissipation of light.
  • The reflectivity of various surfaces are as given in the table:
  • 50% of human comfort is from radiating to cooler surfaces – any object higher than 32-33 degree C (which is just less than skin temperature) causes discomfort


Glare, caused by an excessively bright source of light in our field of view, interferes with our visual perception. In most situations, glare is something we would like to eliminate for better visual acuity. Direct Glare is caused by the bright source shining directly into the eyes. Indirect Glare or Reflected Glare is due to light sources reflected from tasks or other surfaces into the eyes. By having un controlled direction of light, the possibility of glare becomes higher

Incandescent lamp:

  • Light efficiency around 12 – 15 lumens per Watt
  • Works on the principle of heating the tungsten filament
  • Lower voltage reduces the light by fourth power ( 5% voltage reduction, >20% reduced light)
  • Higher voltage reduces life
  • Since temperature can be as high as 80 deg C - hence reduces comfort during warm weather
  • low life – average expected life is 1000 hours, at normal voltage

Fluorescent lamp / CFL Lamps (Compact Fluorescent Lamp)

  • “T-5” or slim tubes with special phosphor can produce 90-120 lumens per watt.
  • Normal tube lights produce 50 – 110 lumens per watt, depending on the manufacturer. - thus 4 – 8 time more efficient than incandescent.
  • Compact fluorescent lamps are tube lights, folded for smaller wattage.
  • CFL is not more efficient than normal tube lights.
  • Works on the principle of gas discharge, which releases light from fluorescent material.
  • Mercury is used as main vapour, which produces ultraviolet rays.
  • With deterioration of coating, light reduces, and ultra violet increases
  • Requires a current limiting device, which is called choke
  • Choke (non electronic or wire wound) consumes about 15 to 20 watts (for a 40 W tube)
  • Electronic choke would produce harmonics, interfering with other electronic devices, and reducing efficiency of some of the other devices.
  • Has low power factor which needs to be compensated, to help power producers
  • Longer life compared to Incandescent – 6000 to 10000 hours depending on the brand.
  • On disposal, causes mercury contamination in the area

Light Emitting Diode (LED)

  • Has present efficiency of 25 to 40 lumens per watt
  • For a 40 degree light, produces more than 16.7 times lux, as a 360 deg lamp. Thus, a 2 watt LED with 25 lumens per watt, would give 1.74 times more lux
  • Due to low wattage, can be brought closer – a light source at 1 meter requires only 10% of power, compared to a source at 3 meters
  • LED light of 1 watt, placed all around the room (4m x 5 m , at 2 m height, spaced 1.5 m apprx) will require 20 lamps, and would give more uniform light than 2 x 40 W lights, placed in 2 ends – thus saving more than 75%
  • Properly designed LED lights have a life of 100,000 hours – at 12 hours per day, it is close to 23 years.
  • Major content of the LED is epoxy/poly-corbonate – can be recycled, as other plastic when collected

- Thanks Mr Jayaraman SECO

Online edition of India's National Newspaper
Sunday, May 13, 2007
ePaper The shades of lights to come

LEDs emerge to challenge fluorescents; bulbs may be pushed out

NEW YORK: The light bulb, the symbol of bright ideas, does not look like such a great idea anymore, as lawmakers in different parts of the world are talking about banning the century-old technology because of its contribution to global warming.

But what comes next? Compact fluorescent bulbs are the only real alternative right now, but "bulbs" that use light-emitting diodes, or LEDs, are quickly emerging as a challenger.

LEDs, which are small chips usually encased in a glass dome the size of a matchstick head, have been in use in electronics for decades to indicate, for example, whether a VCR is on or off.

Those LEDs were usually red or green, but a scientific breakthrough in the 1990s paved the way for the production of LEDs that produce white light. Because they use less power than standard incandescent bulbs, white LEDs have become common in flashlights.

Getting set

Established players in the lighting industry and a host of startups are grooming LEDs to take on the reigning champion of residential lighting, the familiar pear-shaped incandescent light bulb.

The light bulb has been running out of friends recently. California and Canada have decided to ban the sale of incandescent bulbs by 2012. Australia is banning them in 2010. The European Union is looking at banning production of the bulbs. A U.S. Senate committee is working on a proposal that would phase out the light bulb in 10 years. And in New Jersey, where the first practical incandescent bulb emerged from Thomas Edison's laboratory in 1879, a bill has been introduced to ban their use in government buildings.

Governments are gunning for the light bulb because it is much less efficient than fluorescents, using about five times more energy to produce the same amount of light.

Lighting consumes 22 per cent of electricity produced in the U.S., according to the Department of Energy, and the widespread use of LED lighting could cut consumption in half.

Much of that reduction would be possible with today's technology, using compact fluorescents, or CFLs. But consumers have not warmed to them. The light quality has not been satisfactory, most take time to turn on and are not dimmable.

The LED has advantages over the CFL in most of those areas, and judging by this past week's Lightfair trade show in New York, it could be a serious challenge to the CFL in a few years. What holds it back is chiefly price, but LEDs are already an economic alternative for niche uses.

In the last two years, the diodes have doubled in energy efficiency and brightness, according to a North Carolina-based LED-manufacturer. In particular, LEDs that produce a yellowish or "warm" light similar to incandescents have improved.

A Dallas-based company showed an LED "bulb" that can be screwed into a standard medium-sized socket and produces a warm light equivalent to that of a 25-watt incandescent bulb, but consumes 5.8 watts. It costs $50 (about Rs. 2,000) — hardly palatable to consumers who can buy a standard bulb for prices that are much lower.

A draw

The energy efficiency is no doubt a draw for commercial clients such as hotels, but LEDs have another big advantage: they last up to 50,000 hours, according to manufacturers. That compares to about 10,000 hours for fluorescents and 1,000 hours for incandescents. Not having to send out janitors to replace burned-out bulbs means big savings in maintenance costs.

"Right now the applications that make sense are either high maintenance or high power consumption, like parking garages, where the lights are on all the time," said one expert.

LEDs already beat fluorescents for energy efficiency in some niche uses. For instance, Wal-Mart Stores is putting LED lighting in its in-store refrigerators, where the cold dims fluorescents and incandescents produce too much heat. LEDs also starting to replace flat fluorescent backlights in liquid-crystal displays, or LCDs, where they produce better colours.

LEDs do not contain toxic mercury, which CFLs do, though the amount is very small. (Recent stories circulating on the Web about calling a hazmat team if a CFL breaks are exaggerated. The U.S. Environmental Protection Agency recommends sweeping up, not vacuuming, the fragments, then checking out local recycling options.)

The cost of LED lighting should be coming down quickly. One manufacturer said the cost of individual white-light diodes, several of which go into an LED bulb and make up much of the cost, had come down from about $8 to $1.5 in a year. "They're going to keep going down," he said. "By the middle of next year, they'll be priced for consumers."

Technical issues

Nadarajah Narendran, director of lighting research at Rensselaer Polytechnic Institute in New York, cautions that there are still technical issues to work out with LEDs. While single LEDs can demonstrate very high energy efficiency in the lab, when they are combined into fixtures, their efficiency is considerably lower. In part that is a heat issue: the diodes produce less heat than incandescents, but they keep that heat in the fixture rather than radiating it, and the hotter the diodes get, the less efficient they are

Material Reflectence
Aluminum, etched 70-85
Aluminum, polished 60-70
Stainless steel 50-60
Brick, light buff 40-45
Brick, red 10-20
Granite 20-25
Marble, polished 30-70
Plaster, white 90-92
White 70-90
White porcelain enamel 60-83
Oak, light (or teak) 25-35
Walnut (or rosewood) 5-10

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