2015 is the International Year of Light and light-based technologies.

2015 is the International Year of Light (IYL), as proclaimed by the United Nations and at its core, IYL is about recognising the importance of the role light plays in everybody’s lives.

An entire year dedicated to light, you ask? Well, thanks to light travelling through cables, we have the Internet.  Thanks to light’s properties as both a tangible technology and element, it is perhaps the number one cross-cutting discipline of science in the 21st century.

The timing of last year’s Nobel Prize in Physics could not have provided a better segue into the International Year of Light. The prize was awarded to the creators of the blue LED (light emitting diode). This discovery enabled not only a multitude of modern devices from sensory lighting to mobile phones, but also a new generation of bright energy-efficient bulbs, with the Nobel committee recognising the transition from incandescent bulbs lighting up the 20th century, to LED lamps lighting up the 21st century.

Lighting up the 21^st century with LED

The lighting industry is undergoing a radical transformation that has opened up exciting and ground-breaking possibilities, and it is all thanks to LED.

LED technology has come a long way since being introduced decades ago as mere light indicators of gadgets. Today, LED lighting has been rapidly gaining traction as a sustainable, highly efficient way to light up homes and buildings to stadiums and cities.

But what is it about LED technology that has driven the switch from incandescent bulbs of the 20th century to the LED bulbs of today? The long list of advantages associated with LED lighting systems has led to the significant and sustained increase in their usage around the world. Key factors that have heightened the use of LED in both indoor and outdoor applications include energy efficiency, mercury-free, long lifetimes in residential and commercial use, no emitted infrared or ultraviolet radiation and durability.

Understanding LED

In this International Year of Light, education is a key pillar across every aspect of light and light-based technologies for the global initiative. When you start exploring LED technologies you very quickly find there are a few basic terms and concepts that it is worth getting familiar with or re-familiarising yourself with. These include:

LED: An LED (light-emitting diode) is a semi-conductor device or chip that produces light when an electrical current is applied. What’s important to remember is that LEDs are just one of many components – optics, housing, power sources, to name a few – used to create an LED fixture or lamp. When looking at claims about lifetime, efficiency, and design, it is essential to compare the specifications of the entire LED system as a whole, not just the specifications of the individual system components.

Efficiency and efficacy: The ‘efficacy’ of a lighting fixture is usually expressed as the amount of light (in lumens) produced by a certain amount of electricity (in watts). Lighting fixture ‘efficiency’ is the ratio of the total lumens exiting the fixture to the total lumens produced by the light source.

It is important to note that the efficacy of the LEDs themselves is always greater than the efficacy of the LED fixture. This is caused by many factors including losses as light bounces off reflectors and passes through lenses. Make sure when specifying a light fixture that you are looking at the appropriate fixture data versus the LED source data.

Lifetime: For traditional lighting sources, lifetime is reported as ‘mean time to failure’, which means the average time it takes for some percentage of lamps (usually 50%) to fail completely. With an LED source, light output diminishes gradually. So for LED sources, lifetime translates to how long a lighting fixture retains a certain percentage of its initial light output, which is also called lumen maintenance.

The lifetimes of LED sources and traditional light sources are defined differently. For white LEDs, lifetime is referred to as the time after which usually 70% of the original light output remains, not when the source has completely burnt out.

Directionality: LEDs are directional sources. Traditional light sources emit light in all directions. In order to collect light and direct it onto the surface you are trying to illuminate, you must use lenses and reflectors, which absorb light and reduce the total output of the fixture.

Given an LED source is already emitting the majority of light in a defined direction, it requires significantly less beam shaping optics, leading to a more efficient light fixture. A traditional source may produce more lumens than an LED source, but it may lose much of its light when passing through the required optics. It is therefore important to consider total illuminance, measured in lux, when making comparisons between light fixtures.

Correlated Colour Temperature (CCT): Correlated colour temperature indicates the relative colour appearance of a white light source, from yellowish-white or ‘warm’ (2700-3000K) to bluish-white or ‘cool’ (5000K+).

Certain light sources are associated with particular colour temperatures. LED fixtures come in a variety of fixed colour temperatures, making them easy to replace or combine with current light sources. Some LED fixtures also provide a range of colour temperatures within a single fixture.

Colour Rendering Index (CRI): Colour Rendering Index (CRI) is a measure of the ability of a light source to render colours, compared to a reference source (incandescent[i] or daylight), on a scale of up to 100, with 100 being identical to the reference source. What’s important to remember is the higher the CRI, the better the fixture’s ability to show true colours.

LED buyers guide

With there being so many opportunities for contractors to capitalise on advances in LED technology, in addition to the basics, it is worthwhile revisiting key questions that all contractors should consider before specifying or purchasing LED lighting. This is to ensure any solution best meets your requirements and importantly, your customers’ requirements.

The following Q&A serves as a guide to help you get the best quality and most appropriate fixture for each application.

How does the manufacturer define lifetime? How is it measured?

For LED sources, light output diminishes over time, and lifetime typically refers to the useful life of the light output (also referred to as lumen maintenance). As mentioned earlier, the lifetime of a white LED is the time after which usually 70% of the original light output remains.

Does the quoted lifetime include the electronics and other components necessary to drive the LED source?

Under the right conditions, LEDs can operate for very long periods of time. However, it is important that the supporting components used in the fixture design also have long lifetimes and are of high quality.

What is the maximum ambient temperature under which the fixture can operate and achieve rated life?

The lifetime numbers for many fixtures are quoted at room temperature. Make sure to ask what the fixture lifetime will be at the extreme end of the quoted operating temperature range.

Does the fixture design have any special features for heat sinking/ thermal management?

Thermal management plays an integral part in the length of LED source lifetime and is directly affected by fixture design. Heat must be properly drawn away from the LED source in order to maximise product lifetime– this can be achieved through an appropriately designed heat sink.

What warranty is offered by the manufacturer?

Ask for a documented, clear definition of the warranty terms for the product. Beware of vague ‘guarantees’.

If multiple white light fixtures are used on a project, are colour points among them adequately matched?

The tint or hue of white LEDs vary from batch to batch due to inherent variations that occur in all semiconductor fabrication processes. Make sure to ask how the manufacturer ensures consistent colour performance from fixture to fixture.

How does optics affect system efficiency?

Beam shaping optics such as reflectors and cover lenses can have a dramatic effect on fixture performance. Make sure performance claims include these necessary system components. Leading manufacturers will offer photometric data produced by accredited testing laboratories.

Does the proposal for my job include all of the necessary components to operate the LED fixtures?

Many LED fixtures require external transformers and other necessary controls in order to complete installation. Be sure to include all of these components in your project budget.

Becoming an expert

Electrical contractors who understand LED basics and know the right questions to ask prior to specification or installation will be better able to deliver the best LED lighting solution for each project, no matter whether it’s a home, office or stadium.

Keeping up to date with the latest lighting trends, products, requirements, standards and legislation means regularly visiting industry (www.lightingcouncil.com.au), government and lighting manufacturer websites as well as supplementing knowledge through up-skilling courses.