Making light work of energy efficiency
Lighting is widely recognised as one of the best starting places to reduce energy costs in the built environment. Graham White and Greg Herring outline the key issues to consider.
Organisations of every size are facing an unprecedented combination of pressures to reduce energy consumption. Environmental concerns have stimulated a range of legislative measures to combat climate change, and against this backdrop the continuing worldwide economic downturn means that cutting costs is now more urgent than ever.
In the built environment, lighting is a major consumer of energy. Indeed, according to the International Energy Agency (IEA), it accounts for around 18% of global electricity use, while for the UK the figure is about 30%. Improvements in the efficiency of lighting will therefore have a significant impact and can be made without diminishing the quality of the working environment.
This potential for energy savings is emphasised in the relevant parts of the Building Regulations, with Part L2 requiring a minimum efficacy of 55 luminaire lumens per circuit watt (Llm/cW) for occupied spaces in commercial lighting schemes, averaged over the whole building. (Part L2 covers England and Wales, while Section 6.5 of the Scottish Building Regulations lays down similar requirements.)
The effect of Part L2 is to encourage the use of high-efficiency light sources, efficient control gear (i.e. high frequency) and more efficient optical design. In addition, Part L2 aims to stimulate the uptake of lighting controls by allowing a controls factor of up to 0.85 to achieve the 55 Llm/cW figure.
In terms of energy efficiency, the most significant technological development in recent years has been the rapid progress of LED lighting and its consequent widespread adoption. Not long ago, LED technology was confined to use in specific areas such as decorative, ambient and emergency lighting. Now, however, it offers a viable low-energy alternative to fluorescent and halogen lamps in many commercial lighting applications.
For example, the RXS1S LED downlight from Cooper Lighting and Safety has a power consumption of just 14 W, resulting in an energy saving of 72% when compared with an equivalent 50 W tungsten-halogen fitting. Such high-quality LED luminaires, which incorporate effective thermal management and accurate drive-current control, will maintain more than 70% of their initial light output for at least 50 000 h — equivalent to 10 years’ commercial use. This life compares to 12 000 h for fluorescents and 5000 h for halogen lamps.
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| Efficient-lighting technology produced energy savings of 60% at Irish planning board, An Bord Pleanála. |
There is little doubt that LED technology will dominate the future of commercial lighting. However, LED lighting is not suitable for every situation; there are many applications for which one of the more established lighting technologies will provide the best solution.
Where LED lighting is not appropriate, significant energy savings can still be made using T5 fluorescent or compact fluorescent lighting. Energy-efficient luminaires continue to be developed for these light sources — one of the latest examples being the Lechenti fitting from Cooper Lighting & Safety. Designed for use in modular suspended ceilings, this 600 x 600 mm T5 fluorescent luminaire is available in fully recessed or semi-recessed formats with high-frequency control gear as standard. The luminaire can be specified with a central louvre or microprism panel, while its opalised side panels provide controlled light distribution with excellent transmission. This optical design delivers an LOR (light output ratio) in excess of 80% and an efficacy of more than 60 Llm/cW for many variants.
Very often the best approach for the building manager is to seek advice from a major luminaire manufacturer offering a wide range of products encompassing not only cutting-edge LED designs but also high-efficiency fluorescent fittings.
Whichever type of light source is chosen, the use of lighting controls will generate substantial additional energy savings. Lighting controls come in a variety of different forms, but typical functionality includes occupancy detection and daylight harvesting.
Simple occupancy detection using a PIR sensor to switch the lighting on while people are present and off again shortly after they leave can cut energy consumption by 20 to 40%.
In the 5 m area next to windows, further energy savings of 50 to 70% can be produced by using photocells to adjust luminaire output according to the amount of daylight available.
One recent project demonstrates how a combination of energy-efficient luminaires and appropriate lighting controls can significantly reduce energy consumption in an office environment.
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| Lighting controls help to minimise energy consumption, even in high-level applications such as this Delta Group warehouse in London. |
Facilities management company Hochtief FM was tasked with refurbishing the lighting at the offices of the Irish planning board An Bord Pleanála in Dublin to improve lighting levels and energy efficiency. Hochtief decided to use Cooper’s RXD2 LED downlights, Modulay T5 fluorescent recessed luminaires and DSI modular lighting controls, incorporating both daylight linking and occupancy-detection functionality. The result was a 50% increase in lighting levels and a 60% reduction in energy consumption.
Lighting controls can also be deployed effectively in an industrial or warehouse environment. At the new Delta Group warehouse in London, for example, over 200 of Cooper’s Linergy fluorescent luminaires have recently been installed, each with an integral high-level PIR detector and photocell. As well as minimising energy consumption through occupancy detection, the lighting controls sense how much natural light is available from the numerous skylights in the roof of the building and alter the luminaire’s output accordingly.
With environmental concerns unabated and electricity costs set to remain high for the foreseeable future, energy efficiency is a key consideration for any lighting scheme. While LED technology will undoubtedly play an increasingly significant role in commercial lighting installations, it is not a panacea. There are still many applications for which other lighting technologies are more appropriate, and in all cases serious consideration should be given to the use of lighting controls.
Graham White is technical manager and Greg Herring is product marketing manager with Cooper Lighting & Safety.
