They’re easy to maintain, last ages and don’t cook the food. So will LEDs knock fluorescent tubes off their pedestal in shop design? ‘That’s a laugh,’ detractors tell Alistair King
With the help of a crack team of specialists, a Swiss supermarket chain has made lighting history in a small town in the canton of St Gallen.
In many ways, the new store in Eschenbach resembles its many sister outlets in Switzerland’s Migros co-operative. Where it differs is in its lighting. Retail outlets rely heavily on lighting, particularly for display purposes, making them big consumers of power. So Migros decided to light the 829m2 sales area of this shop entirely with LEDs.
LEDs are not usually associated with illuminating large spaces but, at first glance, Migros’ decision makes a lot of sense. They emit neither infrared nor ultraviolet light, so they can be placed closer to food without hastening its decay. For overhead lighting, with clever luminaire design, light from LEDs can be channelled to produce an effect similar to traditional lighting. LEDs are said to have an exceptionally long life, reducing the burden of maintenance, and have low power requirements. Finally, LEDs are perceived to generate relatively little heat, thus reducing the need for air-conditioning.
This list sounds pretty compelling, but do the figures add up? And if they do, is this the start of a revolution in large-scale lighting?
Migros asked lighting company Osram to supply the LEDs for the Eschenbach shop. Osram recommended that Migros appoint SE Lightmanagement to design, make and install the luminaires into which the LEDs would be incorporated.
Osram specified 18,000 of its Golden Dragon high-power LEDs. The company says each consumes one watt of power and has a lifespan of up to 50,000 hours. “Even when using the light for 10 hours a day over six days a week, the average life of a white LED is 16 years,” says Markus Vetterli, an Osram product manager.
SE Lightmanagement was brought in two months before the shop was due to open. It designed three types of luminaire, devised a layout for them and produced and fitted them throughout the shop.
“The spotlights [of which there are 22] can illuminate a circle with an 800mm diameter and 2,500 lux,” says Markus Müller, chief executive of SE Lightmanagement. “The background lighting installation [of which there are 107] is placed in the ceiling, 3m above the floor, and can illuminate about 10m2, with 500-750 lux.”
His company also supplied 37 bar lighting units for display shelves. Müller adds that the 16-year estimate of lifespan is based on light output depreciating to no less than 50% of its original output.
Other industry figures need some convincing that the future of lighting lies with LEDs. “What a laugh,” says Dominic Meyrick, lighting principal of UK-based M&E engineer Hoare Lea.
Meyrick does concede that there are benefits to LEDs. “They’re solid state light sources,” he says, “so unlike other sources, they generate light purely from electronics and no mechanical interfacing with electronics is needed, which means they’re incredibly easy to talk to and easy to run.”
LEDs generate light purely from electronics and no mechanical interfacing with electronics is needed, which means they’re easy to run
Dominic Meyrick, Hoare Lea
But he is extremely sceptical about power consumption. “You’d probably get about 25 to 30 lumens per watt with standard LEDs, compared with about 100 with fluorescent lighting,” he says.
Meyrick also expresses concern. He cites research by the Lighting Research Centre of New York in 2001 that shows the relative output over time for different lighting types. Standard (5mm) LEDs performed badly in the study; high-power LEDs did well.
Colin Beale of Osram’s UK office counters that high-power LEDs were used for the Eschenbach project, adding that the technology has advanced so far that the output of these lights has doubled in the past two years.
Iain Ruxton, an associate at lighting architect Speirs and Major, shares Meyrick’s scepticism, though he’s careful to talk about LEDs in general.
“It’s horses for courses,” he says. “We specify a lot of LED products. They’re useful for some purposes but not others; we don’t believe they’ll ever be a universal solution as they’re low-output devices, primarily used for luminance rather than to illuminate.”
He acknowledges advances in their development but “as a source of usable white light they’re not obvious”.
Ruxton echoes Meyrick’s concerns on efficiency. “Just because something has a low wattage, it’s wrong to assume that it has high efficiency. An analogy is that between cost and value.”
According to Ruxton, shaping the light from LEDs through reflectors and lenses is also difficult. The bigger the “point source”, the harder it is to do that, he says. “With LEDs, to get a usable amount of output, you need about 100 points so you end up with a flat plate of light, rather than a point.”
The luminaire used in the ceiling for this project contains 140 point sources, so should be fine for ambient dispersal that it was designed to provide. But the effectiveness of the spotlight used, which has 22 point sources, could be questioned.
Without data over a longer period from Osram, it’s impossible to tell whether its technology can defy its critics. The benefits of lower maintenance are undeniable, there are aesthetic advantages to the light produced and of the hardware that produces it. The equipment looks easy to specify and accommodate into general designs, and on general principles innovation should not be discouraged. But only the foolhardy would put money on this being the large-scale lighting solution of the near future.
So what is the future of retail lighting? According to Ruxton, “we’ll see a lot of LEDs for colours and decorative use but for general lighting, low-wattage metal halide lamps are becoming more efficient. They provide good-quality white light at around 20W and are at the perfect scale for retail.”
Specifier 18 May 2007
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