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Arctura Water Tank, Östersund, Sweden

Issue 31 Jun / Jul 2006 : Architectural : Façade


Vincent Laganier interviews the Swedish lighting designer Stefan Wiktorsson of Ljusdesign AB, the brains behind the scheme...

What is the function of this building?
In Sweden, we have centralised systems for remote heating of our houses. Most of the pollution from burning oil and coal, brown energy, is replaced with power plants that use waste heating from factories, energy pumps and the burning of household waste. This is where Arctura gets in the picture.
During low-cost hours, when the hot water is cheap to produce, the excess resources are stored in this “thermos”. Arctura contains hot water that is capable of heating the whole town for a couple of days. The building keeps 26 million litres of heated water, in the summer it’s as low as 40°C, and in the winter it can be up to 90°C.
The top of the building is crowned with a skyline restaurant. The views of the landscape are amazing. Below the tank is the ski centre that is commonly used for international competitions.

How did you get involved in this project?
The most common way for us to enter a project like Arctura is direct contact from the architect without spending time participating in contests or making concepts.
Our reputation in Sweden is well founded. When we get contacted, it’s because the architect wants to use our skills and knowledge. Together with the architect we have a brainstorm phase that ends up in practical tests. Even when we do a theoretical design, we also insist on performing real tests. This gives to the end customer the chance to react if the end result isn’t what we expected.

What are the architectural features of Arctura?
Arctura has a bluish greyish colour. It’s a colour that looks OK in the daylight, and it’s also a perfect surface to project light onto during the dark hours. The stainless steel mesh that is applied two metres outside the main building structure helps us to give the building depth. It also gives the building a shape, which from the sky looks like an open eye.

What was your lighting concept?
The concept was to create a symbolic version of the northern lights. The real northern lights rocks the pants of anyone that hasn’t seen it before.
The lighting sequence starts two hours before the sunset and ends two hours after the sunrise. The twilight is several hours long up in the north.

In short, could you describe the lighting scenes?
The main scene is fully automated and based on the seasons. During the summer the sunset and sunrise is the same thing. During the autumn the building has a bluish tone that slowly changes its characteristics, in the late evening the images of the northern lights break up the scenery.
During the month of December, the facade has a warm and bright red tone; it’s amazing when the snow is hanging on the mesh, bright flickering white, with a red-hot building behind. At midnight the 1st of January, there is an automated “firework” of light that runs for approximately 20 minutes.
The spring is once again a clearer bluish tone, without the northern lights. The real northern lights are only present during cold winter nights and we wanted to keep it rather realistic.

Who controls the scenes?
Except from the automated sequences there are ten manually controlled scenes that the local staff in the restaurant can trigger at will.
The owner of the restaurant wanted ten buttons with different lighting effects that is used for shows for its customers: effects like “Light-Beacon”, “Cascade” or “Rainbow”.

Why did you choose to use LED’s?
We did scale tests with PAR 64 1000W with dichroic filters from the ground. It worked fine concerning the amount of light, but we wanted to find a much more cost effective and energy saving solution.
This was a great opportunity to find out if LED’s could do the job. All the glossy brochures from LED manufacturers around the world should be submitted to a real test.
We went to Östersund with 24 LED 1W fixtures from Philips to test on the tank facade which is 60 metres high. We chose a fixture with a very narrow angle, about 2x3°. It actually worked well. The LED fixtures where capable of supplying light up to 30-40 metres high!

Where are the lighting fixtures installed?
The fixtures are installed at the bottom and top of the tank facade. We chose LEDline2 (one colour per fixture: red, blue and green). The three colours are placed close together so that we can mix the light any way.
The white on the mesh used the same fixture but with 48 LED 1W. They are installed at the bottom outside the mesh on a girder.
Lastly, we chose indirect lighting on the ring-sloping roof. We have nine LEDflood LED 3W fixed on the roof.
The reason for not choosing a ready-made RGB ramp was directly related to the fact that our supplier couldn’t provide us with a reasonable price tag. That’s also why we chose DMX over analogue 0-10V control.

What lighting control do you use?
Everything is controlled by an e:cue MediaEngine, it’s a system that is capable of handling events like “2 hours before sunset”. An astronomic clock within the MediaEngine relates to longitude and latitude for triggering events. The control system can easily handle multiple DMX universes, giving us access to over 16,000 DMX addresses.
During the programming phase, we linked out the MediaEngine via a common W-Lan (Wireless Local Area Network) so that we could see what we were doing far away from the building.

Where is the best view point to see Arctura at night?
Arctura, with its northern lights, can be seen from 2-3 kilometres away. The island Frösön, that is situated on the great lake in front of the town of Östersund, is a great place to see the amazing effect. Arctura stands out like a beacon during the dark winter days.

What did you learn from this project?
LED lighting is good enough for this kind of project but it has very monochrome colours. The yellow colours are a bit difficult to achieve. This was a slight problem. But LED is very cost effective.
When it’s lit, the lighting on Arctura only consumes 2500W. If you consider the 10,000 square metres that is lit, it’s like the power of an ordinary washing machine!

technical information

Contracting authority: Jämtkraft AB
Project leader: Franz Birkl, Birco Konsult
Architect: Hans Aldefelt, Sweco FFNS
Lighting design: Stefan Wiktorsson, LjusDesign AB
Electrical consultant: Jämtbygdens Elkonsult (JBEL) AB
Electrical installer: El-Kontakt AB
Luminaires: LEDline2 surface-mounted BCS713 and BCS722, LEDflood BCP730, Philips
Lamps: Lumileds Luxeon LEDs, 1 and 3 W, red, green, blue, white
Control system: MediaEngine and control panels from e:cue
DMX Decoders: Soundlight
Photographs: Stefan Gemzell/LjusDesign AB; Stefan Linnerhag/Jämtkraft AB



pics: Stefan Gemzell/LjusDesign AB


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    Philips LEDline2 fixtures are colour mixed to simulate the effects of the northern lights


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    An e:cue MediaEngine is used to control the LED’s on the water tank with the ability to create thousands of scenes



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