Highly flexible, LED technology will lead to a re-think of lighting applications, writes Steve Coyne, president of the Illuminating Engineering Society of Australia and New Zealand.

From traffic lights to exit signs, torches to street lighting, kitchens to lounge rooms, stadium displays to architectural and decorative lighting - the use of LEDs as a light source is on the rise. Light-emitting diodes, or LEDs, are an important development in the lighting industry and they are here to stay. LEDs have enormous potential.

What are LEDs?

LEDs form the basis of solid-state lighting (SSL) products. They consist of a chip of semiconducting material treated to create a positive-negative junction. When switched on, charge carriers flow into the junction and combine to release energy in the form of photons (light). The colour emitted depends on the materials used to make the diode. LEDs can be red, yellow, blue, green or 'white' (created by combining other colours or using phosphors in a similar manner to fluorescent lamps).
LEDs were introduced as a practical electronic component in the 1960s. Significant technical developments in more recent years have seen them used widely as indicator devices and, increasingly, for special and general purpose lighting.


Benefits
LEDs can be highly energy efficient, comparable to fluorescent technology. They have a long life, lasting up to 50 times longer than incandescent lamps and five to 10 times longer than fluorescent lamps. This makes them ideal for hard-to-access locations. LEDs are durable and can withstand vibration and shocks. They are not affected by regular on-off switching, which is good for areas such as bathrooms and areas with occupancy activated lighting. Another advantage is that LEDs do not contain the toxic substance mercury. In addition, they are at full brightness as soon as they are switched on and can be fully dimmable.


Quality issues
Some types of LEDs, however, still have a way to go to match the quality of other lighting technologies. For example, recent testing of LED T8 fluorescent replacements by the US Department of Energy found bare lamp light output of the LED T8 was about one-third the average for fluorescent T8s. Performance was also significantly below fluorescent T8s in lamp efficacy (efficiency in terms of light output vs. energy consumed) and colour rendering index (accuracy of colour appearance of objects). However, the average fixture (in the form of a recessed luminaire) efficiency was higher for LED T8s because LEDs are directional, so less light is lost inside the fixture.


Other issues
Heat management of LEDs is an issue, requiring elements such as heat sinks. Degradation in LED material and phosphors in white LEDs can lead to colour shift, a potential problem leading to adjacent LEDs having slightly noticeable colour differences. As a point source of light, LEDs are well suited to uses such as traffic lights, but this makes LED use for general illumination more challenging. And while the cost of LEDs is coming down, initial costs remain higher than alternatives.


Expectations and standards
Numerous LED products are now entering the Australian market. While some are excellent, many are poor quality and do not live up to suppliers' claims. Lighting Art and Science December 2009 edition reported that LED testing at the Queensland University of Technology found "Many [LEDs] perform poorly or have failed to meet the specifications for the application that they were designed for".
Such performance issues threaten to undermine user confidence, discourage uptake and delay or otherwise compromise the substantial energy savings potential of LEDs. Many in the lighting industry are keen to promote this technology. However, we want to avoid a repeat of the early days of compact fluorescent lamp technology when consumers were put off by poor quality, premature failures and light output issues.
While new LED standards are being prepared at an international level (with Australian participation), the technology is yet to be properly standardised globally and within Australia. Nevertheless, substantial progress is being made. A suite of international standards from the International Electrotechnical Commission is expected within the next two years


Regulation of LEDs in Australia
LEDs must conform to Australia's electrical safety and electromagnetic compatibility (EMC) regulations. Unlike a number of other lighting products, currently there are no minimum energy performance standards (MEPS) for LEDs. However the Department of Climate Change and Energy Efficiency has signalled that this is likely to change. Hence in all probability we will see minimum energy and other performance criteria applying to these products within the next couple of years.


SSL Quality Scheme
In order to address some of the quality issues associated with LEDs in the Australian marketplace, Lighting Council Australia has developed an industry-led voluntary quality certification scheme for the technology. The SSL Quality Scheme provides confidence to the market that a luminaire carrying the scheme's label matches the supplier's performance claims. Lighting Council Australia verifies performance claims based on test reports or other evidence provided and then authorises the use of the SSL Quality Scheme label. Labels include details such as light output, efficiency, power required, light colour and colour accuracy. Registered products appear on a searchable database on Lighting Council Australia's website (www.lightingcouncil.com.au).


Energy Star
ENERGY STAR originally a US Environment Protection Agency program, but now adopted in a number of countries, is awarded to select lamp and fixture types that meet strict efficiency, quality and lifetime criteria. Those that meet the criteria are typically in the top 20 per cent of product available of that type. To qualify for ENERGY STAR, LED lighting products in the US must pass a variety of tests to prove that the products will display the following characteristics:
• Brightness is equal to or greater than existing lighting technologies (incandescent or fluorescent) and light is well distributed over the area lit by the fixture.
• Light output remains constant over time, only decreasing towards the end of the rated lifetime (at least 35,000 hours or 12 years based on use of 8 hours per day).
• Excellent colour quality. The shade of white light appears clear and consistent over time.
• Efficiency is as good as or better than fluorescent lighting.
• Light comes on instantly when turned on.
• No flicker when dimmed.
• No off-state power draw (standby-power). The fixture does not use power when it is turned off, with the exception of external controls, whose power should not exceed 0.5 Watts in the off state.

Photo courtesy of Scrink: http://scrink.com/2009/12/20/led-lights-not-saving-money/