Lighting today is very much an accepted – indeed almost taken for granted – part of daily life. It is essential at our place of work, indispensable at home and vital for our urban streets and highways. One area of application, though, is more about changing appearances and enhancing the visual landscape, both outdoors and inside – lighting for effect.
The most obvious ‘lighting for effect’ is the floodlighting of buildings and the enhancement of our city centres for those enjoying the night life. Often such lighting schemes use significant amounts of electricity, and take little notice of adjacent functional lighting. However there is now an increasing obligation for all lighting schemes to be as energy efficient as possible; and in ‘lighting for effect’ this is most important, where it could be argued that this is not essential lighting. Fortunately the introduction of high brightness LEDs to this creative lighting market is helping to make such schemes both more exciting and more energy efficient.
Most conventional floodlighting schemes rely on the use of powerful, energy efficient light sources (e.g. high pressure sodium (SON) or metal halide (HPI or CDM)) which project from a remote point, almost literally, a flood of light onto the object to be lit. This solution has been popular because it requires fewer light points (lower installation cost) and the actual lamp efficacy is very high. The drawbacks to this approach include the intrusion of this broadcast light into the lit buildings; remember that hotel room with the annoying orange night lighting?
This is a consequence of the fact that the HPI and SON lamps are not exactly small, a 400W version is some 250mm long, and even careful reflector design still results in high levels of spill (or wasted light).
Another compromise arises when the effect lighting needs to be coloured; conventional practice uses a bright white metal halide source and then uses a filter or gel to create the desired hue. Some blue filters allow only 20% of the original light to fall on the illuminated object! Combine this aspect with the difficulties of optically controlling conventional light sources, and the opportunities for LEDs to improve energy efficiency become obvious.
Firstly an LED is virtually a point source of light, making good optical control quite straightforward and they come in a range of colours obviating the need for energy sapping filters; and, incidentally, blue LEDs are some of the most efficient! Finally, by using white LEDs, lower lighting levels can be used to good effect.
These features explain some recent highly successful applications where LEDs have either provided marked improvements in energy efficiency or made possible schemes that were not previously practical.
The National Theatre
In the summer of 2007 The National Theatre entered into a partnership with Philips Lighting to identify areas where energy savings could be made without compromising the ambiance or appearance of this iconic building. The initial focus fell on the external lighting where the latest colour changing LED luminaires have replaced some of the existing conventional fittings, which relied on filters to achieve their colour effects. Using the National’s considerable lighting application experience, LED lighting was applied to significant parts of the exterior. Philips identified and supplied the requisite fittings and these were then installed by the NT team – a true partnership. The new lighting was switched on formally on 23 October and showed an 80% saving compared to the lighting it had replaced.
The initial scheme covered only part of the building; there remain areas that the LED fittings available in 2007 could not reach. However, in August 2008 the theatre kindly hosted the trial of a prototype of a new generation of colour changing floodlights and this test suggests that, when these fittings are available it will be possible to replace more of the old luminaires. The outcome suggests that (on a typical fly-tower face) four 1200W projectors might be replaced by five 300W units. Something like a 70% saving if all three colours on the LED fitting are running flat out; if only green (say) is being used then the saving is closer to 90%! Hopefully these changes can be realised as soon as the new product becomes available.
An additional benefit delivered by the LED lighting is the fact that they were installed last August and so far there has been no need to return to the fittings for maintenance purposes. Previously regular lamp changes were required; and powerful flood lighting lamps are not exactly cheap.
Until 2006 the front of Buckingham Palace had only ever been lit on special occasions because any attempt to floodlight the building conventionally resulted in light intruding into bedrooms; something that was quite unacceptable to the residents.
However, in 2006, permission was given to test the viability of using warm white LED luminaires to graze light onto the building. The trial was so successful that it was immediately agreed that the Mall façade could now be lit for the benefit of tourists on a permanent basis.
The scheme actually combined linear LEDline luminaires with a few highlighting CDM projectors with a total installed load of less then 3kW. So now the Portland stone of this landmark residence is subtly lit at night with no light spilling into the bedrooms; all for less than the power consumed by a domestic kettle!
Southwark Premier Travel Inn
A rather different residence but nevertheless still an application where spilled light is unwelcome, the lighting of this brick building has been accomplished using warm white LEDlines to give a more interesting night time look, and all with a connected load of just 475W! This application very clearly illustrates the tight optical control of these LED fixtures with light placed exactly where it is wanted with none being wasted.
Of course ‘lighting for effect’ is not solely done outside. Many building interiors, especially, atria and entrance spaces, now benefit from LED lighting, often supplemented by dynamic effects such as colour changing. So, although LED sources have not yet quite reached the outright efficacy of (say) a SON lamp or the lumen packages available from many more conventional lamps, they are demonstrating superior system efficiencies in many effects lighting applications. It is no longer as simple as saying ‘this lamp can produce more lumens per Watt than another’, it is more about choosing the right light source to suit particular circumstances – and LEDs are now serious contenders in many applications.
In conclusion, much is currently being written about LED lighting and some of the hype is confusing, to say the least. The present situation – and it is a rapidly changing one – is that there are now many practical applications for LEDs, especially in projects requiring precision and colour. In the very near future some of the first really practical LED solutions will become available for more general lighting applications. For example the new Fortimo downlight module will shortly bring 1000 and 2000 lumen packages and efficacies near 60 lumens per Watt; a solution easily capable of beating many compact fluorescent fixtures. Certainly the future of LED lighting looks bright but it is not yet the universal solution, it will be some time before we can start to say farewell to more conventional sources.