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New Heights For LED Lighting

Carbon8lightingCCSLED luminaires are fast becoming the preferred lighting option when it comes to performance, energy efficiency and lamp life but it is important to get the combination of LED lamp, fitting and controls right. Simon Miles, Sales director of Carbon8lighting explains.

LED lighting is now well established in a wide range of commercial applications but the latest LEDs re also becoming more popular for the more onerous requirements of high bay and exterior lighting.

As a result, LED lighting has the potential to make a significant contribution to any company’s energy and carbon reduction programme, as well as reducing the life-cycle costs of the lighting installation by minimising maintenance requirements. This latter aspect is particularly important where fittings are difficult and/or disruptive to access.

Another benefit is the provision of better quality light with improved colour rendering, compared to the discharge lighting that is typically used in high bay and exterior lighting applications. This is particularly beneficial for visually demanding tasks such as assembly and picking. In outdoor applications, whiter light with better colour rendering also engenders a feeling of security.

Consequently, it is almost inevitable that electrical engineers will become involved in the specification and installation of LED lighting systems, if they haven’t already. It is therefore important to fully understand all of the characteristics of such systems, from the choice of light source through to luminaire design and how the system will be controlled.

Lumen output – not wattage

One of the key differences between traditional light sources and LEDs is that with LEDs the wattage does not correlate to the light output - it’s the lumen output that counts. In the past replacing existing lighting was pretty straightforward, in terms of sizing the light sources. If the old installation was using 400W SON then so would the new system – or maybe it would upgrade to 400W metal halide. With LEDs though, the situation is a bit more complex – because with LEDs it’s the lumen output that counts rather than the wattage.

Early LED high bay/low bay fittings typically achieved 80-90 lumens per watt so a 150W fitting would produce 12,000 to 15,000 lumens and would be a suitable replacement for a 400W HID lamp. The first LED high bay fitting we introduced in 2015, for instance, produced just over 14,000 lumens.

However, LED fittings have evolved. The high bay referenced above was quickly superseded by a 120W version capable of delivering over 18,000 lumens and more recent models can give 16,000 lumens from the 90W version and over 25,000 lumens from the 150W version.

Replacing a 400W HID lamp with the latest 150W LED high bay would produce about 40% more light than is needed, resulting in a significant waste of energy. The 90W version would clearly be a more appropriate substitute, saving the end client money on energy, with further savings on capital costs since 90W lamps are cheaper than 150W lamps.

The right direction

HarvestFoodsAnother important factor with LEDs is that they are directional, so in a luminaire that has been optimised for use with LED light sources less of the light is ‘lost’ in the luminaire – compared to HID fittings. This is why it’s important to select luminaires that have been designed for use with LEDs from the ground-up, rather than having been simply tweaked a bit from conventional luminaires.

The directionality of LEDs also makes it possible to be a bit more creative. For example, most lighting upgrade projects are carried out on a one-for-one replacement basis to take advantage of the existing cabling. This is why it’s important to get the light output right. The directionality of LEDs also makes it possible to be a bit more creative. For example, most lighting upgrade projects are carried out on a one-for-one replacement basis to take advantage of the existing cabling. This is why it’s important to get the light output right.

Optimised luminaires

As indicated above, the luminaire design is an important role to play and should be designed to take full advantage of the performance characteristics of the LED light sources. In this way, the benefits that arise from the inherent efficiency of the LED light sources are maximised.

The luminaire design also plays a key role in the thermal management of the LED circuitry, typically by incorporating an aluminium heat sink to conduct heat away from the sensitive electronics, possibly bolstered by a design that encourages air convection through the luminaire to remove waste heat.

Taking control

In the past, the limited controllability of discharge lighting has imposed constraints on the level of control that can be achieved in these applications, thus limiting the potential for additional energy savings over and above those achieved by reducing the installed electrical load.

In contrast, LED lighting is highly controllable, opening the door to many opportunities for improved control that will avoid energy being wasted. Obvious examples include using occupancy sensors to dim the lighting when aisles between racking are unoccupied or when a loading bays not in use. It also becomes very straightforward to use photocells to take advantage of daylight entering through windows or roof lights.

Similarly, outdoor lighting on building perimeters and in car parks can be adjusted to deliver different light levels at different times. For example, providing maximum light output when staff are arriving or leaving during the hours of darkness and dimming the lighting at other times.
 
The important thing here is that LED lighting offers a great deal of flexibility in terms of control, so that the exact control strategy can be precisely tailored to the requirements of each project.

Not all LEDs are equal

It is particularly important to be aware that not all LEDs are equal, in terms of light output, energy performance and lamp life. When considering LED luminaires, manufacturer should be able to provide the reassurance that their LEDs are high quality.

For example, there have been issues with poor quality LEDs exhibiting variation in colour temperature between individual light sources. This is because the way that LEDs reduce white light is quite complex. It actually involves using a blue LED that excites a phosphor coating and it is the phosphor that emits the white light.

The consistency and quality of the phosphors used is therefore critical in ensuring consistent colour temperature. Quality control procedures that ensure consistent colour temperature are clearly important and a good indication of this is whether the manufacturer is able to state a precise colour temperature, rather than a range.

There is no doubt that the right combination of LED light sources, luminaires and controls will provide a solution that improves light quality while also reducing energy and carbon emissions with minimum life-cycle costs. Making sure you have the ‘right combination’ necessitates a thorough evaluation of all the criteria that might impact on performance.

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