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What does this mean beyond being a buzz phrase? It can vary with project applications but there are some common strands:
1. Efficient light sources such as T5 fluorescent, metal halide and some LEDs.
The efficiency of light sources is measured in lumens/watt. An efficient source is typically one with 80 lumens / watt or more of raw light output. However most lamps require some form of driver or transformer, which also has some electrical loss that needs to be included. After this is taken into account the comparison is 6-15 lumens/watt for standard domestic light bulbs, 15-25 lumens/watt for most halogen lamps and 40-60 lumens/watt for many standard fluorescent products. Only the most efficient fluorescent lamps are up above the 80 watt threshold.
These are mainly linear T5HE (not T5HO) fluorescent lamps in 14, 28 and 35w when running close to their optimum ambient temperature of 35°C. High wattage CFL lamps, such as 55w (4-pin) lamps pass this threshold, but many standard fluorescent lamps fall significantly short. The new 14w and 17w PL-R/TL-R lamps from Philips/Osram for compact fluorescent downlights make the grade - replacing 18w and 26w PLC/TLC lamps, which do not.
Good metal halide lamps can achieve the threshold, but only when run off the more expensive HF ballasts.
The best LEDs are improving efficiency rapidly and are reaching this level in 2010. However LEDs have to be selected carefully, because the published product information is sometimes inaccurate and few products have been independently tested. If LEDs are being bought as substitutes for conventional lighting, they are best sourced from suppliers which understand the conventional technologies as well. They are better placed to provide an objective comparison of the product performance. LEDs are an excellent technology that may suffer from low customer satisfaction as a result of overselling activity, particular in the form of misleading comparisons with halogen or CFL.
2. Effective light fittings that do not waste light and direct it where needed.
Once light has been generated it needs to be delivered effectively. Some fittings waste a lot of light within the fitting itself through poor thermal design or material specification. Other fittings emit light ineffectively through inefficient optics. The ability of a light fitting to emit light is measured in its Light Output Ratio (LOR) - typically an efficient fitting would have a ratio at least above 0.6, and probably above 0.7, meaning that 70% of the light from the lamp leaves the fitting. When Exit Lumens are referred to it is the output after calculating LOR. It is important that raw lumens and exit lumens are confused in any comparison. The LOR has another element to it as well, because the light may be emitted in different directions that have an impact on its effectiveness as a source of light. An upward LOR (ULOR) requires the light to be reflected from a ceiling or wall if the target surface to be lit is below the fitting. In contrast a downward LOR (DLOR) is capable of lighting a surface directly. For this reason in office lighting downlighting (DLOR) is accorded an effectiveness rating twice that of uplighting (ULOR). This means that in general you require double the lumens, for a given amount on a table or desk, if that light is uplighting than if it is downlight.
Effectiveness is demonstrated in the case of halogen dichroic fittings. When used as spot lights, they still have low efficacy (relatively) at generating light, but are efficient at delivering the light where it is needed. In comparison a CFL version might produce higher efficacy, but with greater difficulty in putting the light on the surface required. For this reason, to light a small surface to a given brightness would require less power with LV halogen, whereas a large surface would be better done with CFL. This is an example of how understanding some simple principles of lighting design is a help in creating an efficient lighting scheme.
3. Usable lighting controls that limit the unnecessary use of electricity.
One of the most visible signs of wasted energy from lighting is when empty space is left with all the lights on. It is now common in offices, and increasingly in other areas, for some form of occupancy sensor to automatically dim or turn off the lights after a set period of absence has be detected. These sensors are often combined with light sensors that detect when there is sufficient daylight in the space for the artificial lighting be reduced or turned off.
The energy saving potential of these controls varies from building to building. High occupancy buildings will save little from presence detection for obvious reasons. The additional power used in the system (for the detectors/intelligent ballasts) may in some cases be as great as any saving made. Equally obvious is that spaces with little or no daylight will not benefit from daylight control. Sometimes these realities are overlooked in the rush to tick energy saving boxes and the result is more, not less, energy consumption. The parasitic power of controls and fittings in standby mode is no longer ignored by the measurement methodology for commercial buildings - in particular that of BS EN15193 that produces the input to the Energy Performance Certificates.
4. Low toxicity of light sources and consumables – for example low mercury lamps.
A number of lighting components and consumables contain toxic materials. The usual example is low pressure mercury lamps, commonly called fluorescent tubes, which can release their mercury into the environment when they are broken. Environmental disposal is now a legal requirement for all lighting equipment. The technology exists to reduce the mercury content of lamps close to zero and where the mercury is still required it can be provided in the form of amalgam that does easily escape into the environment. However these lamps are not well suited to either deep dimming or emergency lighting applications.
Other toxic elements, such as lead as cadmium are now largely eliminated from lighting equipment. The main exception has been the cadmium present in NiCad batteries for emergency standby purposes. For this reason Clearvision recommends LED technology for much of its emergency lighting applications - this technology requires much smaller and more sustainable (NiMH) batteries.
5. Greater longevity of components to limit future waste flows.
Light fittings are quite often designed for short life because they are sold on price to customers who do not ask about the longer terms costs. Fittings with cheap ballasts are an example of fittings that will have a high maintenance cost within a few years and probably be discarded after a relatively short life. This is wasteful and expensive both to the owner and the environment. Fittings can be designed with longer life components and consumables - for example ballasts that have a 100,000 life are available against those with the standard 50,000 hours and many that will last not much longer than the lamps. Long life (for example 60,000 hour fluorescent) lamps are also available in more formats than ever before.
6. Refurbishable design that will also reduce future waste.
It is quite common for light fittings to be discarded when only one or two components have reached the end of their life. The cost of refitting new components is often greater than supplying a new fitting. A wasteful throwaway culture is perpetuated by poor design. The first generation of high frequency ballasts were often positioned within fittings with little regard to their replacement. Then the second generation HF ballasts were shorter - and with different wiring configurations - that made rewiring a necessity when replacing the ballast. These days the best fittings have removable geartrays that will make this process much simpler and cheaper in the future, allowing refurbishment rather than replacement of fittings. However many cheap luminaires make no effort to allow easy access to the ballast for this purpose.
7. Recyclable packaging materials .
The lighting industry uses a lot of packaging material as an inevitable by product of having to get products onto and around job sites undamaged. Much of the industry has moved to plain brown cardboard as one of the easiest materials to recycle - and is using much greater amount of previously recycled materials. Polystyrene has been phased out by most responsible suppliers.
8. Supply chain emission reduction in material transport and components.
This is a difficult issue in a very global business. Most manufacturers use components and materials sourced from around the world. Even products 'locally' made often have every major constituent part from imported materials and components. Efforts are being made to avoid air transport, but few companies can claim that their product has not travelled a long way in aggregate. Some companies are applying low emission strategies on their organisations in order to compensate for this reality.
9. Application design services to allow customer access to low energy schemes .
It is sometimes overlooked that lighting application design is an important element in translating efficient products into low energy projects. Full service lighting companies that know their products are well placed to advise and support their customers in extracting the greatest sustainability from their products. In addition many of these companies support specifiers with software that allows them to design the most effective schemes for their customers.
10. After sales support to maintain low energy schemes and ensure longevity. Lighting installations that are not well maintained degrade quite swiftly. This can result in higher energy and consumable use as well as much shorter life. More companies recognise the need to stay with their customers in the after sale period to maintain the quality of the installation. End users are being advised of the need for planned maintenance programmes to maintain the sustainability of their lighting.
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