LED: LIGHT SOURCE OF THE FUTURE

LED is without doubt the most talked-about issue in the lighting industry these days. What makes LED so interesting?

The LED technology is in rapid development, and LED has many applications. Whist it started our being used for small indicators, it moved to signalling, and is now considered to be the light source of the present and future for general lighting.
 

Because of the robustness of the diodes, and huge operating range, LED is fast becoming the preferred light source in cold environments such as cold rooms and freezer rooms, along with demanding environments such as onboard ships, rigs, and areas of high vibration. It is often described as “Solid State” as the light source does not come from the old gas-based technology (HPS and fluorescent lighting in particular), which has always suffered from areas of high vibration and shortening of the lifetime from switching.
 

The longevity of the diodes makes them popular in inaccessible areas lending the technology to the likes of floodlighting and aviation signalling in particular. Other applications are emergency lighting, task lights, downlights, spotlights and other general lighting products, and as replacement for conventional light sources wherever possible.
 

The next generation of LED lighting will offer the end user huge reductions in ongoing maintenance and spares inventory, whilst increasing the safety on industrial areas through improved lighting levels. Whilst this all sounds exciting, there are many key elements to look for when making the correct product selection. As the LED lighting is relatively new as a source of general lighting in an industrial environment, not all manufacturers offer the full picture of what are the key points in assessing LED products against the next.
 

Some of the following points can be useful when making this choice:

Are all LEDs a blue/white?

A common myth is that all LEDs are blue in colour temperature. LED chips are manufactured in mass, and individually tested to define each colour temperature. They are then classified into a binning structure to classify each chips colour temperature, usually within a range of three steps. This process is called the Macadam ellipses. A tolerance of three bins is considered consistent and ensures they is no viable difference to the human eye. Manufacturers must choose the correct selection of chips to ensure the colour temperature is appropriate for the application of the light fitting.

Remember, the lifetime of the LED chip, is not the lifetime of the fitting.

Whilst LED chips are individually tested to give a lifetime in a given ambient temperature, this is not the same as the lifetime of the fitting. LED chips and the electronics housed within light fittings are affected by higher ambient temperatures, with the higher the temperature, the shorted the lifetime. The housing of the light fitting is key to ensuring the heat generated internally is able to convect externally and away from the LED chips and electronics. Because of this requirement, a metal body can assist in extending a fitting lifetime, as traditional GRP is actually an insulator. Over the past number of years Marine-grade, Copper-free Aluminium products have been used to ensure good thermal management is ensured.

Lifetime without mortality, lumen maintenance factor and ambient temperature mean nothing.

Some lighting manufacturers have been able to make statements on product lifetime without giving a full picture of what that lifetime equates to in terms of light output. Many manufacturers will offer a fitting lifetime of 100,000 hours, but interrogation of the facts is key. As we have mentioned, the electronics and LED chips used to control LED are subjected to a range of ambient temperatures, which can have a huge effect on the product lifetime. Whilst an operating temperature range is common on data sheets, this does not tie in to the product lifetime. This means that the fitting will function at that state temperature range, but does not confirm for how long. The lifetime of the fitting should be stated at an average ambient. The longer the lifetime at a higher ambient, the longer the product will last at lower temperatures. Lumen Maintenance factor gives the percentage of the original light output at the stated lifetime of the product. L70 is common, meaning that the fitting will give out 70% of the original light output at the end of the fitting lifetime. Additionally, the mortality rate refers to the percentage of LED chips that will remain at the end of the given lifetime. This can vary between B50 and B10, meaning that some fittings will have a mortality of between 10% and 50% at the end of the product lifetime.

Is there such a thing as a maintenance free light fitting?

Currently no, although many manufacturers do make this claim. To Ex Products, where BSEN60079 dictates as a minimum inspection requirement for all Ex products. Whilst some offer a sealed diffuser, anything with removal components, batteries and a list of available spares means that some maintenance will may be required during the product lifetime.

What does “LED inside” refer to?

Some LED lighting manufacturers refer to “LED inside” products. These are simply put, and an existing gas based light source fitting (fluorescent and HPS for example) with the control gear removed and replaced with LED gear trays or alike. Whilst often this offers the customer an improvement on their existing lighting, some manufacturers argue that this does not offer the best thermal management of the LED chips and electronics, and in turn reduces the potential lifetime of the fitting.

Why are they more expensive?

As with any new technology, LED fittings have started at a much higher cost than their equivalent gas-based lighting fitting alternatives. However, as the adaption to LED becomes more prevalent, manufacturing costs are coming down. This trend is continuing. Additionally as a rule LED fittings last longer and require less maintenance than gas based technology, the additional spares business lighting manufacturers have been accustomed to is becoming less and less, so recouping potentially lost sales has to be factored in.

Can I retrofit to replace existing fittings?

In short, yes. Currently LED products are manufactured with a one-in, one-out mentality, meaning light distribution and fixing methods will tie in to existing installed gas-based fittings. As lighting measurements are done differently, using LED lighting (Lumens as opposed to LUX) it is important to speak with manufacturers and reputable distributors to ensure that the correct fitting is offered for the correct application. However, as the technology develops, there will be opportunities to reduce the number of fittings installed and redesign lighting layouts.

What is my safety net if something goes wrong?

Many LED manufacturers offer extended product warranties. This can give you the peace of mind that should anything happen to the fitting (usually excluding installation errors or through external impact) you have the opportunity to claim back a new product within the specified warranty period. Warranties can range from 1 single year all the way to 10 years. It is important to check the warranty before committing to the purchase of the product.