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Challenging the accepted wisdom around LEDs and energy efficiency

Posted by Paul Huggins | 7 April 2014 | Viewpoint
Warehouse before (left) and after (right) LED lights have been installed

Warehouse before (left) and after (right) LED lighting has been installed

Carbon Trust research and LED product testing has revealed that the accepted wisdom regarding LEDs can, on occasions, be misplaced. Paul Huggins, Associate Director, Carbon Trust Programmes, looks at LED performance and how to ensure an energy efficient lighting solution.

 

LED lighting has come to be seen as energy efficiency’s ‘killer app’ in recent years – it is seen as the affordable solution that is suitable for almost every lighting need, offering big savings with quick paybacks. But new Carbon Trust research and LED product testing has revealed that the accepted wisdom regarding LEDs can, on occasions, be misplaced.  The truth of the situation is that not all LED units are the same. The accepted wisdom needs to be at best tempered and, at worst, actively challenged.  

Lighting typically consumes 20 percent of the electricity used in commercial and industrial buildings. In these times of high energy prices finding cost-effective ways to reduce levels of electricity consumed by lighting can deliver appreciable long-term reductions on business electricity bills. And recent advances in LED technology means that it can now be used to efficiently provide lighting for a wide range of purposes: from general office lighting to amenity, accent and display lighting, or for lighting large interior or exterior areas.

In this context LED lighting technology looks very attractive. New LED units (as opposed to retrofit LED lamps) have the potential in the UK to reduce electricity bills by more than £300 million and reduce carbon emissions by over 1 million tonnes over the next three years. But not all LEDs are created equal.

Because lighting solutions last a long time - often more than 15 or 20 years - conventional technologies such as halogen, compact florescent (CFL) or high intensity discharge (HID) lighting (such as sodium) make up the majority of the installed base of lighting found in commercial and industrial buildings.

Everyone now realises that LED lighting technology represents a tremendous opportunity to significantly reduce the total energy used to provide lighting in buildings.  For example, replacement of halogen lighting by LED units has the potential to reduce electricity consumption by between 65 and 85 percent.

Similarly, replacement of CFL or HID solutions can deliver electricity savings in the region of about 20 percent. For the past seven years the Carbon Trust has undertaken active monitoring of the LED unit technology market and has also, on four separate occasions, tested LED units which represent the best performing products available in the market.  This research allows the following conclusions to be drawn:

  • Since 2007 there has been fourfold increase in lighting efficacy (the amount of light output for a given amount of electricity) in LED technology. In 2007 efficient LED lighting could typically deliver electricity savings when used to replace halogen technologies, which are often used for amenity accent and display lighting purposes. Nowadays efficient LED units are capable of delivering efficacies more than 20 percent better than existing conventional lighting technologies across a wider range of lighting applications, including CFL and HID lighting.
  • The colour and warmth of white light produced, as well as the colour rendering (the quality of other colours when seen in the white light) has improved year-on-year since 2007 and is now close to or as good as conventional lighting technologies.
  • LED optics are improving. Unlike conventional lighting, LED light is emitted from one or more LED chips in an LED unit. Optics are built into many LED units to manage how the light is projected onto the required surfaces. Compared to conventional lighting solutions, LED units often produce a narrower beam of light. This isn’t a problem in a good lighting design but could be a problem in a simple lighting switch out – just replacing existing lighting with LED unit replacements - as it could leave some surfaces under lit.
  • Long term LED performance is generally good. Like conventional lighting, the amount and quality of light emitted from an LED unit decreases over time. At 6,000 hours the overwhelming majority of LEDs tested were within the expected performance range, meaning that a good lighting design would deliver long term and effective lighting solutions.


That said, there were some issues:

  • Visually identical LED units can have different operational performance. In one sense LED units are like computers in that they have a chip, control software and a casing. If the wrong LED control software is installed the performance of the LED unit will be inferior. In a small number of cases, on our testing programme, the wrong control software was provided by LED unit suppliers. This meant that the LED units underperformed against their claimed performance. These units were supplied as market-ready examples and therefore an inference can be made that a proportion of market-ready or installed LED units do not operate to specification.
  • Different LED units using the same LED chip perform differently. During our testing programme different suppliers provide LED products that used the same LED chip. The performance of the LED chip was dependent upon the temperature at which it was operating (yes, it may be a surprise but LED chips do get hot!). Operating temperature is influenced by the design of the LED unit casing and heat sink. Our testing results suggest that standard LED chip data cannot be taken as being representative of LED unit performance. This means that claims of LED chip operating hours of, say, 50,000 hours are not representative of LED unit operating lifetimes which are likely to be shorter, for example they could be 30,000 hours. There is an acknowledged trade-off between LED chip temperature and unit operating hours.
  • Some LED units long term light performance was poor. In a small number of test cases the light output provided at the end of the testing period wasn’t at an acceptable level. If such products were installed in a commercial or industrial setting they would deliver, over time, unacceptable levels of lighting.


It is clearly the case that many LED units deliver energy efficiency savings, and when such units are used in an energy efficient lighting design they can deliver high quality lighting solutions which save electricity, money and reduce carbon dioxide emissions. It is equally true that using poor performance LED units won’t deliver energy efficient lighting. Lastly, when LED units are used as part of a poor lighting design the lighting solution may actually consume more energy than the alternative conventional lighting technologies.

  1. Choosing an LED solution before having an energy efficiency lighting design is like putting the cart before the horse, so focus on picking the right lighting solution: Choose a reputable lighting supplier such as those found on the Carbon Trust’s Green Business Directory or on the LIA website.
  2. Specify that you want an energy efficient lighting design and that you want to use lighting products that meet the requirements of the Energy Technology List. Indicate you have an interest in LED technology.
  3. A reputable supplier will then design an energy efficiency lighting solution that incorporates LED technology where it is appropriate to do so.
  4. During procurement and commissioning ask the lighting supplier to confirm that the performance of products used achieve the levels specified in the product data sheets and that the installation is as per design.


Use of a reputable supplier, a good lighting design and the choice of the right lighting technology will deliver an energy efficient lighting solution. With a growing likelihood that the right lighting solution will tend to be based on LED technology, but that will not always be the case. Be prepared to learn that the right solution may be a mix of lighting technologies.

 

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