Trade Resources Industry Views An Artificial Skylight That Can Simulates a Sunny Blue Sky

An Artificial Skylight That Can Simulates a Sunny Blue Sky

An Italian professor has created an artificial skylight that simulates a sunny blue sky. Lighting is the first UK magazine to speak to him about his astonishing invention

If you have the opportunity in the next few weeks, make an appointment to visit Ideaworks' showroom near Great Portland Street in London. For there, in a corner of the residential lighting design firm's basement, is one of the most astonishing pieces of lighting technology you will ever see.

The first time we were invited to see the Coelux Skylight and meet its creator, Professor Paolo Di Trapani, the London sky was a daunting shade of grey and a filthy mizzle was making the Marylebone pavements slick. And yet, thanks to the Italian professor's invention, the ambience in the underground space where we conducted the interview was closer to that of a Mediterranean villa.

Coelux Inventor Brings Blue Skies Indoors

Professor Paulo Di Trapani with his invention at the Ideaworks showroom in London

Photos might give a sense of how the 'product' replicates a summer sky, but it has to be seen in person to be appreciated as a feat of optical engineering. Trapani explains that the aperture of the artificial skylight opens into a recess merely a metre deep in the basement's false ceiling, but it creates the impression that you are peering into the infinite depth of our blue atmosphere. Stand to one side and stare into the recess at a 45-degree angle and a dazzling sun appears to blaze back at you.

Light in the lab

The professor and laser physicist from the University of Insubria in Como reveals that the sunlight simulating technology was never supposed to be a commercial venture. It actually came into existence as a result of his almost Da Vinci-like obsession with replicating natural phenomena under laboratory conditions.

"It started by chance almost 15 years ago when I was challenged to make a presentation about lighting phenomena," says Di Trapani. "I'd read a book by the astronomer Marcel Minneart called Light and Colour in the Outdoors which describes atmospheric phenomena and I spent the weeks before the lecture trying to photograph the strange things he describes in the book."

"I was disappointed not to be able to photograph any of these things and so, as the lecture approached, I decided to try to rebuild nature in the laboratory. It wasn't that easy, but after a lot of work I was able to reproduce every single phenomenon."

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Di Trapani used LEDs to recreate the spectrum, power, brightness and directionality of the sun

Di Trapani argues that some of these phenomena run contrary to what we might think. He holds his hand in front of a white wall to argue his shadow is blue rather than the grey most people imagine and describes how rainbows have fringes below the red line that flicker when a storm is in the air.

Reinforcing the sense that he is an artist as much as a scientist and inventor, he says he went on to display some of his daylight-simulating devices alongside famous artworks by impressionist painters like?Van Gogh at an exhibition in a disused railway station in Lithuania.?In the process, he was able to prove that some of the lurid colours in their vivid paintings were not the result of absinthe-soaked delusions, but actually faithful renderings of natural light. "When I finished my experiments and looked out of the window, I realised I had been blind and I had to train myself to see light properly," he says. "The idea of the exhibition was to give people the same opportunity to appreciate art and light in a new way."


The Coelux skylight can be seen as a refinement of Di Trapani's experiments. In the Lithuanian exhibition he used huge pools of water and nanoparticles to simulate the sky. But with the help of an EU grant, he has now dispensed with the water and developed a compressed solid sky optic that can be housed in a one-metre-deep false ceiling measuring 3.5 metres by roughly 1.5 metres. In the process, he has opened up a huge number of potential applications and commercial opportunities.

He is understandably tight-lipped about how the skylight works but describes how the optic creates an illusion in the brain of optical depth. "It compresses 10 kilometres into a few centimetres," he says.

The patent that Professor Di Trapani filed with the US Patent Office describes 'a solid optical sky-sun diffuser which compromises a transparent solid matrix embedding a dispersion of transparent nanoparticles'. In rather more simple terms, the nanoparticles in the diffuser simulate the conditions in the earth's atmosphere to recreate the Rayleigh scattering process that makes the sky appear blue. ??

Building the sun

Di Trapani explains how his team had to take on the significant challenge of 'building the sun' from scratch using LED technology to recreate its spectrum, power, brightness and directionality. "We didn't want to use a stage light because they cost a lot of money and consume a lot of energy," he says. "We also had to develop the optics to compress the 150 million kilometres distance from the sun into a metre. To create shadow you need a very compact source, so all the power should be very concentrated, so the luminance, the brightness should be very high and that's not a conventional light source you can find on the shelf."

It almost seems sacrilegious to ask about the efficacy of the LED sun, or indeed the price of the skylight, but Di Trapani refuses to directly answer these questions anyway. "You understand it is a new technology. It very much depends if you are an airport ordering a hundred or a single apartment doing just one. You can't compare it with a lamp; it's an architectural device and a very complex system." ?

Whatever, the answers, they would be unlikely to deter some customers. It's not by accident that the product is on display at Ideaworks' showroom – a custom electronic design and installation company specialising in high-end residential and super-yacht projects. Professor?Di Trapani says 60 per cent of the product enquiries so far are from the residential market and James Siddle, technical lighting designer with Ideaworks, can see why: "A lot of our clients in high-end residential tend to build downwards," he says. "They struggle to get a truly natural light, so this product would be perfect for those types of applications."

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Di Trapani says 60 per cent of enquiries are from residential customers

Siddle is confident that designers and architects won't be put off by the dimensions of the product either: "The housing for the product is quite big, and Coelux admit it is huge, so you will have to design architecture around this rather than the other way around. But when designers see this, we think they're going to make that sacrifice."

Despite the lighting context and the target market, however, Di Trapani is adamant that his creation is not a lighting product. "I prefer to see it as a device that creates space," he says. "Your brain desperately wants infinite space. We are made for the outdoors, having spent the last several hundred thousand years outdoors, and we are suffering from the absence of space."

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Coelux Inventor Brings Blue Skies Indoors
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