LED Foundation

Eco-friendly LED lighting

An article by Dr. Paul Singh in The Tribune India on Friday, December 28, 2007, Chandigarh, India

One of the main sources of global warming is the electricity generation as it requires burning of coal and other fossil fuels, which emit greenhouse gases. For the growth of industries, the consumption of power is increasing at an astronomical rate. The lighting is one of the sectors of power consumption, which eats 19 per cent of total electricity. In this sector, a lot of improvement is needed to enhance the efficiency of lighting devices, which will allow us to bridge the gap between the supply and demand of power.

Since the advent of electricity, the incandescent bulbs are the most widely used device for lighting purposes owing to their simple operation and low cost. But these are also the most inefficient devices as they convert only 10 per cent of energy into useful light and remaining 90 per cent of energy goes waste in the form of heat.

In the recent past, compact fluorescent lamps (CFLs) have been brought in use for lighting. These are more efficient than usual bulbs and convert 30 per cent of energy into light energy. A CFL can operate on only 20 per cent of the power of an ordinary bulb of similar output and has a life span 8-10 times that of a bulb. According to an estimate, switching to energy efficient lamps would result in 555 million fewer tonnes of CO2 emissions and 1560 million fewer barrels of oil consumed each year. This would be equivalent to putting off 530 power plants of 1000 MW each.

According to V.Raghuraman, Principal Advisor & Chief Co-ordinator, energy, environment and natural resources, the CFLs are not the panacea for lighting. After 10 years, more efficient light lamps like Light Emitting Diodes (LEDs) would come into picture and it would be possible to address the issue of hazardous mercury in CFLs.

LEDs deliver more brightness per watt and consume far less energy than traditional bulb. The LED lightings have life as long as 11 years, thus, virtually eliminates the need for replacement.

The latest LED light bulbs now produce about the same amount of light per watt as CFLs, which are supposed energy efficient. Unlike incandescent bulbs and CFLs, which throw light in all directions, LEDs are directional and drive the light in one direction, so that one gets the light exactly where it is needed. This directional lighting means savings in yet another way.

LEDs have already found use for following purposes:

• In architectural lighting, Traffic lights and signals, Bike lights, Lights on emergency vehicles, Exit signs and Railroad crossing signals.
• Status indicators on all sorts of equipment and movement sensors such as optical computer mice.
• Remote controls for TVs, ACs and VCRs use infrared LEDs.
• Continuity indicators like Elevator Push Button Lighting, Flashlights and Message displays at airports and railway stations.
• Red or yellow LEDs are used as indicators in environments where night vision must be retained: aircraft cockpits, submarine and Ship Bridge.
• Due their long life and fast switching action, these are used in automotive high-mounted brake lights, truck and bus brake lights. This increases the reaction time equal to one car length.
• LED-based lights are in use on the eve of Christmas and Diwali. These lights are although costly but consume much less power to give the same amount of light as a similar incandescent bulb.
• Computers use LEDs to tell the user its current state.
• LED panel light source is used in an experiment on plant growth. The findings of such experiments may be used to grow food in space on long duration missions.

The first practical visible light emitting LED was developed at General Electric Company in 1962 by Dr. Shuji Nakamura of Nichia of Japan. He used a composite YAG phosphor coating on top of a blue LED, which converted blue light into white light.