illumination Physics

HILTON CAPITAL GRAND

Abu Dhabi

Integrated LED façade lighting designed to withstand operating temperatures of

75°C

This project has been operating faultlessly for more than

8 years

Integrated LED façade lighting designed to withstand operating temperatures of

75°C

This project has been operating faultlessly for more than

8 years

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We are handed an ambitious lighting design for a new building that is already under construction. No allowance has been made in the façade for any lighting and the glass panels are already being fabricated. A completely custom light fixture will be required and we have only weeks to come up with an answer. Additionally, the building is in Abu Dhabi so the façade will be hot enough in summer to fry an egg…and fry any of the normal lighting electronics.

The pressure (and heat) was on.

Originally called the ‘Bridgeway Hotel’, this building has become the Hilton brand flagship in Abu Dhabi. We received a brief from Bo Steiber Lighting Design in August 2009 during which time the building was under construction. The façade design for the building made no provision for the mounting of any lighting and yet the approved lighting concept required that a matrix of LED dots be attached to the façade at the junctions of the glass panels. Often, it is the case that development of the building envelope occurs before the lighting is developed. It is neither the fault of the lighting or façade designer.

THE CHALLENGE

We faced four fundamental issues:

Heat: the temperature of a modern façade in the UAE can reach over 70 degrees Celsius on a late summer afternoon. An air temperature of 50 degrees Celsius is possible but this is compounded by solar radiation. Depending on the precise nature of the façade materials, experience has taught us to anticipate a factor of air temperature plus 50% approximately. The lighting will be attached, if not embedded in, the façade and will acquire the same temperature by conduction and radiation. Certainly during the night, the façade will cool slowly but this is too late. The building owners will want to illuminate their building during the golden hour of sunset, a time when the façade is still almost at its hottest. The operating temperature will be well beyond the limits of a typical LED luminaire that has electronics on board. The components such as the PSU and the DMX circuitry are typically limited to a maximum operating temperature of approximately +45 degrees Celsius. This limitation is fatal in the Gulf.

Façade: this was not designed to allow for lighting at all and it was far too late to make any changes to accommodate it. Orders had been issued to the façade company and any changes would result in disastrous delays and additional costs, regardless of whether small changes were actually difficult to achieve or not. The onus to solve the installation method fell entirely on the shoulders of illumination Physics. A decade of experience in integrated façade lighting would be crucial.

Variation: there are three distinctly different façade construction types used in the building envelope; free standing monolithic glass suspended on truss and ‘spider clamps’, conventional unitised curtain wall panels, and glass cladding over concrete parapet walls. The outward appearance of the LED lighting must be identical but three different mounting methods are required.

Time: we are engaging with these problems with just a few months lead time. Not only is our product development severely compressed but we must quickly give key information about power and data wiring to the mechanical and electrical consultants for overall coordination.

THE SOLUTIONS

Fortunately, illumination Physics had embraced the extreme heat issue previously. The Sheraton Hotel in Dubai has a similar lighting design using LED dots integrated into the façade. This project had lead us on a path of development of a range of products which we call ‘IP Gulf Spec’. Typically in the market, LED light fixtures have an operational working temperature of 45 degrees Celsius. This limitation is typical because of the generic components used in LED luminaires with AC power and data on board. illumination Physics were pioneers of this type of LED product, but the inherent temperature tolerance of the electronics ruled them out for the Gulf.

The answer lay in simplicity. If the luminaire can be reduced to its simplest components, then the temperature tolerance can be achieved. The remote LED drivers were placed inside the hotel in a benign environment. The LED dots for the Sheraton contained no electronics, just a group of high power LEDs from Lumileds. The fixture was made of marine grade aluminium. The lens was made of UV resistant and solid PMMA. The LEDs themselves have a maximum junction temperature in the semiconductor of 140 degrees Celsius. The junction temperature is a simple thing to manage. There are four basic factors:

• The ambient heat
• The voltage supplied from the constant current driver
• The constant current
• The ability of the heat sink to dissipate the heat in the mounting pad of the LEDs

If the ambient heat is high, then the full potential of the LED to be driven by the driver must be reduced such that the junction temperature is managed in a survivable way. A modern high power LED can be driven at 1000 milliamps at 25 degrees Celsius. However, the light output is more than acceptable at far lower currents. This simple management of the junction temperature worked perfectly on the Dubai Sheraton and it would again with the Hilton in Abu Dhabi.

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This thermal simulation of a typical fixture used CFD to predict the junction temperature of the LEDs when driven at 350 milliwatts during a typical Gulf ambient temperature of 70 degrees Celsius. The maximum junction temperature is 92.376 degrees Celsius which is approximately 45 degrees below the maximum junction temperature of the LEDs used in this fixture. The lens of this fixture has been removed so that the LED is visible in the model.

The heat problem is solved. Now onto the integration issue. How do we put lights on a building that was not designed to accommodate them?

Future maintenance was a concern. Whilst the mountings would be embedded in the structural silicon used to close the joints, it was critical that the luminaire itself could be detached and replaced easily on the outside of the building where the only access would be by gondola.

Mounting and custom design for
variations in the façade

We knew that we had the basis of an optical design with our Gulf Spec LED dot. Driven at just 350 milliwatts, it would be more than sufficiently bright.

The first task was to determine the basic dimensions of the luminaire. As the dots would be placed at the junction where 4 panels meet, we planned to use a mounting technique we had used on other curtain wall buildings. A stainless steel conduit would penetrate the façade acting as both a path for the cable and a mounting for the base plate of the luminaire. Generally, the diameter of the penetration we created was small - only 12mm could be permitted to pass through the silicon joints in the ‘spider wall’ of the hotel atrium. In the curtain wall areas, the joints were a little larger as we were mounting into the mullions and a penetration of 15mm was permissible. We wanted to cover the joints in the façade but without making the luminaire unnecessarily bulky. A diameter of 75mm was the best compromise.

Future maintenance was a concern. Whilst the mountings would be embedded in the structural silicon used to close the joints, it was critical that the luminaire itself could be detached and replaced easily on the outside of the building where the only access would be by gondola.

To facilitate easy maintenance, it was decided that we would create a luminaire that had two parts - a mounting chamber and the luminaire itself which would attach to the mounting plate by a barrel screw thread, sealed from the environment with a marine grade ‘O-ring’.

The luminaire would have a threaded collar that could rotate independently of either the mounting chamber or the luminaire so that they could be locked together.

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Male connector

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Cable gland nut needs a special tool for tightening

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O-ring 3x

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5.50 x 2
For M5 base mounting

A production sample of the final bespoke and complete illumination Physics ‘gulf spec’ luminaire for the Hilton Capital Grand Abu Dhabi. The locking ring clamps the mounting chamber to the luminaire. The mounting stud doubles as a conduit for the DC cable.

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Mounting for Atrium
Speck type 2

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O-ring/rubber pad

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M5 threaded hole type 2

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Mounting for 3rd row
(Highest Level) Speck type 3

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Mounting for Mullion
(provided by curtain wall
contractor) Speck type 1

An electrical connector would sit within the mounting chamber, so in the event that a luminaire has to be changed, the collar could be undone, the connector disconnected and the replacement luminaire is fitted in the reverse sequence.

All of the Dots and mounting chambers would be identical. The problem that remained were the three types of penetrations in the façade.

The most straightforward was the type 1 mounting for the unitised curtain wall. Working with the contractor, we devised a mounting that penetrated the mullion detail. It could be easily installed during the normal erection sequence without any delay to the program.

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The atrium was more complex and required two additional variants. Typically, we could penetrate the joints between the glass panels by drilling the structural silicone after it had set and inserting out ‘type 2’ mounting. The threaded stainless steel conduit would tighten upon two circular disks which would clamp onto the glass inside and outside with ‘O-ring’ seals.

Type 3 was required for the highest part of the atrium ‘spider wall’ because the clamps that held the glass panels were set back and an adjustable stud was required to deal with the tolerances.

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A photo of the approved sample for the typical atrium fixture. The two stainless steel circular pads are tightened so that they clamp onto the inside and outside of the glass and the mounting chamber attaches to them.

This photo shows the extended mounting for the highest row of luminaires in the hotel atrium. Due to the setback design of the ‘spider clamps’ at this level, it was necessary to create a longer and adjustable version.

Speed and Agility

It is inevitable there will be limited time to design a custom lighting product for a building under construction. In the off-the-shelf lighting sector, the development of a new product is leisurely and a year or more may pass in the process of bringing a new product to the market.

During the build of a new building, the shop details will evolve during the construction process. It is essential that illumination Physics react rapidly and creatively to weekly changes because the construction program will not wait for the lighting contractor.

illumination Physics has decades of experience in façade construction. We know how to react regardless of whether we are also the installer or we are providing support to another local installer, as was the case with the Hilton. The draft design for the light fixtures and mounts was created in just two weeks and constantly revised according to the façade drawings as they were approved for construction. Samples of all three mounting types were made in just thirty days and tested on mock-ups at the site.

When approved, the entire order was manufactured and shipped to Abu Dhabi in..

70 days

320 pcs

Speck BH

55 pcs

HP LED Driver

1 set

X-NET-8

3 pcs

DD-4lll

Bridgeway Hotel System Schematic Diagram

Control by DMX-512

This photo shows the extended mounting for the highest row of luminaires in the hotel atrium.
Due to the setback design of the ‘spider clamps’ at this level, it was necessary to create a longer and adjustable version.

Control and Electronics

Whilst it was the façade integration that presented the most unique challenge, our solution was to provide a complete package including all of the drivers, special cables and control system. The DMX control and distribution network was designed to take account of the building’s internal layout, bearing in mind this would be a hotel and any interaction with the guest areas and the lighting should be avoided. The constant current driver system means the cables between the drivers and the luminaires can be up to 100 metres in length, allowing for great flexibility in the positioning of the drivers, typically in existing ELV rooms serving other functions of the building.

Accordingly, the control system design was created by illumination Physics including the detailed schematic drawings and installation instructions. We provided supervision on site as well as training for the local technicians, in our home facilities. We attended during the testing and commissioning. Each light fixture was tested at the time in was installed so that we knew the integrity of all 320 Dots.

Nothing was left to chance.

THE OUTCOME

The result is exactly what the client was expecting and then a little more. The difficulties of an ambitious lighting design were overcome in an expert and methodical way. In total, 320 light fixtures have been integrated in the building envelope without any compromise to the function of the lighting or the façade. The system is easy to maintain although since the post testing and commissioning hand over, there has been no need for any maintenance. The system has operated faultlessly for seven years in an environment so harsh that hearing about related architectural LED lighting system failures is more common than not. This project typifies the illumination Physics method of approaching a problematic project. Eschewing any compromise, we have delivered a total solution - the circle of responsibility complete. The Physics of Illumination has taken priority over all else.

THE OUTCOME

The result is exactly what the client was expecting and then a little more. The difficulties of an ambitious lighting design were overcome in an expert and methodical way. In total, 320 light fixtures have been integrated in the building envelope without any compromise to the function of the lighting or the façade. The system is easy to maintain although since the post testing and commissioning hand over, there has been no need for any maintenance. The system has operated faultlessly for seven years in an environment so harsh that hearing about related architectural LED lighting system failures is more common than not. This project typifies the illumination Physics method of approaching a problematic project. Eschewing any compromise, we have delivered a total solution - the circle of responsibility complete. The Physics of Illumination has taken priority over all else.