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Sat 5 Nov 2005 04:00 AM

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Ski Dubai sets the standard by creating a desert winter

In a town where ‘biggest is best’, the construction stakes have been raised even higher by Dubai’s new ski slope, which is set to open next month. Zoe Naylor wrapped up warm and went to see how it has been made possible to achieve temperatures of minus eight in the middle of a desert.

four hundred metres of fun: snow-making is well underway on the middle east’s first indoor ski ‘mountain’|~|94proj200.gif|~|Phil Taylor, CEO, Ski Dubai: “Right now, we’re running the snow-making system all day and are making 120 tonnes of fresh snow every 24 hours.”|~|It is not often that you need to don a woolly hat, scarf, insulated gloves and thermal jacket for a site visit in Dubai.
But that is what is needed if you visit Ski Dubai in the Mall of the Emirates, where they have been making snow since 11.40 am on 14th October.

When the centre finally opens its doors to the public (scheduled for early December), it will feature five different slopes, with the longest run being 400 m. There will also be quad chairlifts and button lifts to transport visitors; and a snowboard park — not to mention over 6000 tonnes of snow, equivalent to around 22 500 m2 or three football pitches.

“Right now, we’re running the snow-making system all day and are making 120 tonnes of fresh snow every 24 hours,” says Phil Taylor, chief executive of Ski Dubai. “Shortly, there will be enough snow in Ski Dubai to accommodate the most advanced skier.”

Using Acer Snowmec system technology, liquid water is atomised to create a cloud inside the building. This cloud is then ‘sprinkled’ with tiny hard ice particles (10 micron diameter) which allow snow crystals to form and then fall from the cloud as real snow.

This snow-making process will normally only be carried out
at night-time, when the temperature inside the building will
be dropped to -8 degrees celsius. During normal daytime
operations the temperature inside will be between -1 and -2
degrees celsius.

“We’re aiming for an opening date of 2nd December [National Day] but the criteria is the amount of snow that we can make,” explains Richard Haddon, senior project manager at Majid Al Futtaim. “We need a minimum of 300 mm of snow to open to the public — any thinner and you’re looking at damage to the slope caused by snow boarders shaving off the top layer.”

The plan is to have a 200 mm layer of coarse snow that compacts quite densely, and then a 100 mm layer of finer snow on top of that.

“We can change the quality of the snow,” says Haddon. “We have different nozzles which fit onto the snow gun and these determine the size of the droplets, which in turn determines the quality of the snow produced.”

An AB groomer is used to position the snow on the lower slopes by scooping it up and blowing it into place. A bigger grooming machine, a Kassbohrer, with wide tracks, is used further up the slope as it is the only one that can tackle the steeper gradient.

A glycol cooling system installed beneath the snow layer helps to maintain the temperature of the snow so it doesn’t degrade. The system circulates at -15 degrees celsius.

“The glycol system is split into two sections — upper and lower,” says Haddon. “It is fully automated so we can divert the flow of the glycol to make snow where we want to.
“We also have three ammonia chillers outside and can run
on two of them while the third is spare. We’re running all three at maximum capacity [at the moment] to ensure the highest efficiency of snow making.”

With a full capacity of 1500 visitors, damage to the slope caused by over-zealous skiers and snowboarders means the snow will need constant replenishing to maintain its quality.
“To maintain the ski experience the top layer of the snow will be replaced every day. The two grooming machines thin off the top few centimetres of snow and then push it down the slope towards the lower groom store where there is a melt pit.
Then we simply make new snow on top.” There is another groom store and melt pit located at the mid station where the bigger Kassbohrer operates.

Since the volume of snow that is being replenished daily is not sufficient to warrant recycling it completely, it will instead be used to irrigate the gardens outside.

Other design features, such as the way the structure of the building is used to create an insulated box around the slope, help to make this feat of engineering in the desert possible, yet alone economical and efficient.

PIR (polyisocyanurates) panels, made in Belgium, are used to insulate the entire structure. These are tightly packed together and similar to the type of technology found in cold stores.

“The panels form a double layer of insulation — an inner and an outer skin,” says Haddon. “The outer skin is required to prevent the sun from warping the panels due to the temperature differential between the two, which in summer will be around -6 on one side and 50 degrees on the other.
“Since the heat absorption of the roof panels in summer could reach 72 degrees we couldn’t manage with just a single skin.”

In addition to the double layer of insulation there is a cooling area in the void between the two skins. The void above the roof area is 4 m deep and around the side it is approximately 1.7 m.

In terms of power consumption used to generate cooling for the project, Haddon says that the snow dome does have its own sub-station; however, the biggest energy demand was for the initial cooling of the space.

“The greatest energy load placed on the system was to bring it from 42 degrees to -6 degrees. We had to bring the temperature down progressively to avoid thermal shocks to the building and specifically to the glycol pipes.”

This gradual cooling involved reducing the temperature down to a holding temperature of 15 degrees; it was then brought down progressively to 5 degrees, and then held at zero. Once the temperature reaches zero it is quite quick to take it sub-zero.

And what if there is a power outage at the snow dome? “We have a contingency plan in place for a power cut; the temperature in here will stay intact for about one week,” says Haddon. “And in the worst-case scenario, if there is any melting, we have an overflow system that will take the water away.”

The snow dome was originally scheduled to open in
September. According to Haddon, one of the main reasons for the delay was the lack of permanent utilities available on site: “We did as much work as we could on temporary power and temporary water.

DEWA faced a big challenge to provide all the substations for the development, and it seems we were at the end of the line in terms of getting the permanent water and power.”

Specialised glass from Switzerland was used within the construction process. It gives very clear visibility from the shopping mall into the ski slope and vice versa, and has a Luxar coating on the inside to cut down on glare. The price? A cool US $1.6 million (AED6 million) for 18 linear metres.

Sometimes the smallest of issues can present the biggest practical obstacles, such how to clean the glass at sub-zero temperatures (water is useless; an alcohol-based cleaner is used instead).

Haddon says one of the biggest challenges of working on the project was the sheer complexity of the three-dimensional structure. “The engineering was complicated in terms of sorting out the joints, and stringent quality control meant that a lot of the welds were rejected in fabrication,” he says. “In the end it all passed, but it took longer than anticipated and we lost a fair amount of our float period.”

The team also encountered problems with the chairlifts and had to make numerous adjustments to achieve the correct height when loaded: “The design was fine on the drawings, but in practice the pick up at the mid-station was too high, as was the off-loading at the top,” says Haddon.

He says another challenge is the element of the unknown: “In building a unique construction project such as this, the challenge is bringing the various elements together, incorporating specialist knowledge and then dissecting it into practical sectors so everyone knows what they have to do.”

Many of Dubai’s far-fetched construction projects such as Chess City and the Hydropolis fail to make it off the drawing board.

But a 400 m-long indoor ski slope built in the middle of the desert proved to be a surmountable challenge. And if all goes to plan, we should be sunbathing in the morning and skiing in the afternoon in time for the New Year.||**||

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