KNOWLEDGE
Coming of age

Do you know a lighting installation that’s long in the tooth? Perhaps it’s time to put it out of its misery and replace it with a younger model, says Gordon Routledge

Lighting accounts for about 20 per cent of global electricity consumption, and is often considered an easy target when implementing energy efficiency schemes to cut carbon emissions to meet climate change targets.

The average age of a UK lighting installation is estimated to be 18 years. Back in 1994, East 17 topped the charts at Christmas, lamp ballasts were lumps of metal that made lamps jolt and flicker, and lighting controls were switches. In those days, people did not debate the relative merits of LEDs and T5 lamps, or the latest metal halide developments. The technologies available were very inefficient compared to what is commonplace today.

If an 18-year-old lighting installation is compared with one that uses today’s best practice in design, controls and light source technology, then savings of at least 50 per cent are achievable.

The cost of light

At the heart of any decision to improve the efficiency of a lighting system is a financial determination – often based on hard numbers – to establish a return on investment.

Most organisations have a good understanding of utility costs and some data can be extracted from half-hourly metering data for organisations that have a lighting system in which the use follows a set pattern matched to office, opening or operating hours. The task is much more dif cult for organisations that own multiple sites with different operating requirements where lighting is often a transient load with electricity fed from multiple distribution boards.

The energy cost of light can be established by a combination of site surveys and some power data logging. But what about the opportunity cost of light? Light is not simply about kilowatt-hours.

Back in 1994, lighting design practice and recommendations where signi cantly different. The 1990s gave us the Cat 2 louvre and halogen lamps, which led to drab of ces and acne of the ceiling across the land in hotels, houses and shops. Simply to replace like-for-like is a missed opportunity and can be damaging because lighting is a key ingredient for success in many businesses. A poorly implemented retrofit can turn a well-lit hotel room in to a drab flat lit space, sparkling and vibrant retail displays can become dark, lifeless caves.

Benchmarking

What is the cost of light today, and where can we get to? We often start the process by breaking down the problem into common applications. Corridors, office space, toilets, storage, plant rooms and car parks are some of the applications common to most businesses. Then, for each area, we find out the current power consumption, light levels and typical occupancy rate.

The reason for finding the light level is that many areas are signficantly overlit and weren’t properly designed in the first place. Conversely, many older buildings are underlit by current standards. EN 12464 gives a useful list of common lighting applications by industry, together with recommended lighting levels.

A benchmarking program can compare common application areas on one site or across similar sites and assess them against industry best practice. It can then form the basis of a hit list of the areas consuming the most energy, and hence establish priorities for further investigation and action.

Taking action

Implementing energy saving is all about applying the right technology to the right application and establishing the cost benefits between a good solution – which may simply be a retrofit lamp – and the best solution – which may be new fittings combined with a control system.

Attitude Raising the importance attached to energy efficiency inside an organisation can have a dramatic effect in itself. Some users in commercial properties have achieved a 17 per cent reduction in energy use by simply targeting staff behaviour. At the extreme end of the scale some organisations use Japanese improvement methods in the shape of energy kaizen events to implement rapid improvements.

Retrofits Retrofit lamps can be a quick way to achieve a rapid reduction in energy use. However, be cautious and understand what is important in the lighting application. Although the range of retrofit solutions is growing all the time, the lighting performance often differs signficantly from the incumbent technology. For example, linear LED fluorescent tubes have a radically different light distribution that is much narrower than the 360-degree fluorescent tube. This can cause a big change in light levels, uniformity and glare that may fall well below the performance levels specified in the original design.

Lighting controls Implementing lighting controls can make huge savings, and very fast paybacks, but again caution is essential. Fitting occupancy sensors to light fittings that cannot be switched hundreds of times a day causes a drastic reduction in lamp life and shortens maintenance cycles. Harnessing the benefits of controls often demands a change of lamp control gear, or new  ttings to make systems fully compatible. The range of controls geared towards the retrofit market is expanding rapidly, with wireless sensors and microwave detectors making implementing controls in existing installations easier.


Daylight The best light is free, but often ignored in older installations. The controls technology to adjust lighting levels in response to daylight is readily available – to implement daylight linking will require signficant reinstallation.

Redesign Sometimes a fresh approach to design is the best way forward. Designing the lighting to match requirements can achieve rapid paybacks, but installation work can be signficant. Warehouses are a classic example, originally designed as general manufacturing space, with lights positioned on a uniform grid, rather than being aligned along racking aisles that were added later.



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LOR

Light Output Ratio – the percentage of light emitted from the light source that makes it out of the luminaire. An LOR of 70 means 30 per cent of the light from lamp is lost inside the reflector and light fitting.

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