LED White Paper

LED Lighting: Delivering quality, cost-efficiency and convenience

 

 

Contents

  1. Time to upgrade your lighting? ………………………..……….……..……………………….… 3
  2. What are the different lighting options? .........................……….…............................................. 4
  3. What is LED lighting? ….........................................................................….…................................ 7
  4. Why are LEDs gaining popularity? ..........................…….…......................................................... 9
  5. Creating higher quality LEDs ……….……….………....………………....…………………..… 11
  6. Are there any problems with LEDs? ……...….….…...……..………………………........…….. 13
  7. The future of lighting ………….….………….......………..……………………………………… 14
  8. References ………………….………….…………….........……………………………………… 16

 

 

  1. Time to upgrade your lighting?

As the cost of energy continues to increase, businesses and homeowners are targeting efficiency gains wherever they can be found. According to the Energy Saving Trust, lighting typically accounts for eight per cent of a household's energy bill[1] - so there is a clear incentive to reduce consumption in this area -whether you are a homeowner, business or public organisation.

But by targeting increased efficiency, is there a need to sacrifice quality of illumination, safety, flexibility or convenience? Thanks to continuing technology innovation, the answer is a clear no. As more advanced lighting solutions arrive on the market, providing new upgrade options, users are able to reduce lighting costs while maintaining quality of output.

On cost grounds alone, there is sufficient incentive to consider a change of lighting solutions - installing new fixtures and fittings to support a more advanced type of bulb. Factor in other potential advantages - in areas such as quality, colour tone, longevity and maintenance - and the case for an upgrade becomes even clearer.

 

  1. What are the different lighting options?

There are a variety of different solutions to choose from for general lighting purposes, including:

Incandescent/ halogen

These bulbs generate light by passing electric current through a resistive filament. Heating the filament to a very high temperature causes it to glow and emit light over a broad range of wavelengths.

  • Colour rendering index (CRI): 90-100
  • Lumens/Watts: 5-25
  • Lifetime: 1,000 hours

The bulbs are inexpensive at the point of purchase, but are relatively inefficient since they use electricity to generate heat as well as light. The bulbs typically have a short lifespan and need to be replaced fairly regularly.

Compact fluorescent (CFL)

CFL bulbs function by passing electricity through mercury vapour, which in turn emits ultraviolet light. This is then absorbed by a phosphor coating inside the lamp, causing it to glow.

  • CRI: 60-90
  • Lumens/Watts: 50-75
  • Lifetime: 6,000-15,000 hours

CFLs are much more energy-efficient than incandescent bulbs and last much longer. However, they are sensitive to temperature and - since they contain mercury, a toxic substance - need to be handled carefully.

Metal halide

These lamps produce light by passing an electric arc through a gaseous mixture of vaporised mercury and metal halides. They are similar to mercury vapour lamps, but the additional compounds - metal mixed with bromine or iodine - offer improved brightness and colour.

  • CRI: 70-95
  • Lumens/Watts: 60-100
  • Lifetime: 6,000-20,000 hours

Known issues with metal halide lamps include long start-up times, a poor T-rating, the potential for colour shift, unreliability in extreme temperatures and the presence of toxic substances. End-of-life can also be a dangerous event, due to the use of high pressure gases.

High-pressure sodium

These gas-discharge lamps create a bright orange light by energising high-pressure sodium held within. They are smaller than the low-pressure equivalent, which provide a softer, luminous glow.

  • CRI: 30
  • Lumens/Watts: 60-120
  • Lifetime: 10,000-24,000 hours

High-pressure sodium lamps experience similar problems to metal halides - including colour shifts, a poor T-rating, unreliability in extreme temperatures, a long re-strike time and mercury content.

Light-emitting plasma (LEP)

LEPs generate light by exciting plasma inside a closed transparent burner or bulb using radio frequency power. When gas contained in the lamp is ionised, free electrons, accelerated by the electrical field, collide with gas and metal atoms to create a light source.

  • CRI: 50-90
  • Lumens/Watts: 60-90
  • Lifetime: 100,000 hours

These lamps offer longevity and energy efficiency, and are available in increasingly compact sizes. However, since they contain gas, LEPs must be handled with care.

 

  1. What is LED lighting?

Another lighting option to consider - and one that is continuing to gain in popularity - is the light-emitting diode, or LED.

An LED is a semiconductor light source, used as an indicator lamp in various electronic devices and increasingly for general lighting purposes. LEDs have existed since the 1960s, but in recent years technological refinement has seen their use become more common across a variety of sectors and industries.

  • CRI: 70-90
  • Lumens/Watts: up to 150
  • Lifetime: potentially over 100,000 hours

Essentially, LEDs are just tiny light bulbs that fit into an electrical circuit. However, unlike other types of bulb, they do not contain a filament which can burn out. And because light is created by the movement of electrons in a semiconductor material, the LEDs do not get hot.

When the LED is switched on, electrons are able to recombine with holes within the device, releasing energy in the form of photons. This creates a light through the process of electroluminescence, with the colour determined by the energy band gap of the semiconductor.

By the 1980s, LEDs were bright enough to be used in vehicle brake lights and traffic lights - the first time they replaced incandescent bulbs in a lighting application. And by the 1990s, researchers had created the first white light LEDs - the forerunners to those now being used for general lighting.

According to the Lighting Research Center[2], white light can be made by mixing the light from several coloured LEDs to create a spectral power distribution that appears white. This offers high luminous efficacy, good colour rendering properties and flexibility to achieve any desired colour property.

An alternative approach is to use phosphors together with a short-wavelength LED. This results in a single, compact, white light source, but has lower overall luminous efficacy. Also, the uniform application of phosphors in the manufacturing process can prove difficult to control.

 

4. Why are LEDs gaining popularity?

LEDs offer a number of potential advantages to users compared to other bulbs, including:

Energy efficiency - LEDs use up to 90 per cent less energy than other types of bulbs - helping to reduce electricity costs and also minimise environmental impact.

Longevity - the latest generation of LED bulbs are capable of lasting many years without burning out or losing more than a fraction of their brightness.

Ease of maintenance - with such a long life-expectancy for higher-end LEDs, and few if any replacements required, changing bulbs in accessible locations is easier.

Brightness - LEDs offer similar brightness to halogen bulbs, and are suitable for a range of lighting purposes - including general, feature and control.

Instant illumination - LEDs are instantly bright the moment they are turned on, meaning there is no need to wait for full illumination.

Flexibility - some LEDs can be used with a dimmer switch, giving users the option of changing the brightness of the bulb according to need.

Safety - unlike CFLs, metal halides and high pressure sodium lamps, LEDs do not contain harmful mercury and other toxic substances.

Temperature control - LEDs do not get hot to touch even after hours or days of illumination, helping to ensure a stable temperature.

Satvinder Panesar, senior global buyer at RS Components, explained that LEDs have a number of technical differences to other types of bulbs. "With LED, you can turn the product on and it is instantly bright. With the other technologies, it takes time for the product to turn on and off," he stated. "High-pressure sodium lamps for example - there's a delay from when you turn the product on for it to reach full brightness. But with LED lighting you can frequently just turn it off and on."

Panesar noted that energy efficiency is a major draw for LED lighting, with users typically saving 70 per cent on electricity consumption compared to some of the older technology bulbs. "And the product lasts a lot longer," he said. "We're talking about say, 35,000 hours versus 2,000 hours when comparing an LED to a halogen."

"The saving comes in with the lower power consumption," Panesar added. "Also, you don't have to pay a maintenance engineer to go up and down the ladder, replacing the products. So the total cost because of the extra life of the product makes it a lot cheaper to use in the longer term." A further advantage of LEDs is the fact they work off a low voltage, he noted. "You can tag LEDs onto things like solar energy," Panesar said.

 

"LEDs are extremely efficient and can generate more light per unit of electricity than most technologies. They don’t need mercury and can last up to 50 times longer than a conventional incandescent lamp and around five times longer than a CFL light bulb."  Lighting Industry Association

 

  1. Creating higher quality LEDs

A number of improvements to the bulb manufacturing process over the past decade have helped position LED lighting as a high-quality and increasingly affordable option. Jonathan Domingo, product development engineer at LED maker Lumex, said industry innovation has allowed LEDs to move beyond indication lighting and into a wide range of new applications[4].

Writing for EDN Network, he claimed "dramatic" change has been witnessed in the industry over the course of the last ten years. "Enhanced equipment, improved processes and superior materials have led to a higher volume of consistently high-quality LED chips for manufacturer use," Mr Domingo noted. "These quality chips provide key performance benefits including even greater energy savings, space savings and superior visual performance all at a lower cost than was previously possible."

 

Manufacturing advances

He told the news provider that multi-reactors systems are now used to create the die substances used in LEDs, and these provide superior wavelength uniformity, generate more consistent colour performance, and operate at a lower cost than Metalorganic Chemical Vapour Deposition machines. Mr Domingo added that better airflow systems have helped reduce the risk of contamination during the production process, and this has also helped boost quality.

"Due in large part to this enhanced equipment, the structural efficiency of LEDs has improved from 50 to 70 per cent