By Sean Cronin
Contractor is mid-way through the construction of the largest district cooling system of its type ever developed.
Drake & Scull to set world record on JBR cooling job|~|JBR-body.jpg|~||~|What will it take to keep six thousand residents of Jumeirah Beach Residence cool in the heat of Summer?
The answer is about one million gallons of water a day.
That is what could be consumed by the new district cooling system currently being built by Drake & Scull to service the 54 towers which will be built there over the next five years.
It is the largest district cooling system of its type anywhere in the world, though that could change quickly.
Construction-related world records tend not to last very long in Dubai and this will be no exception.
Both Nakheel and Emaar are believed to have plans for even bigger schemes needed to service the Palms and the Burj Dubai developments.
But for the time being at least, Drake & Scull’s project is the biggest and boldest in town.
The US $65 million (AED 240 million) lump sum contract covers the design, construction and two year operation of the plant.
There is an option to extend that operating period if required.
Despite consuming such vast quantities of water, it also has environmental bragging rights according to project manager Richard Broadhead.
“It is worth mentioning that the reason we are seeing all these systems being developed comes from the Kyoto Agreement, because they are so energy efficient,” says Broadhead, a 35 year Drake & Scull veteran.
He works alongside operations and engineering manager Dr Gareth Lucken, and together the pair oversee work on what will be the first of several mega-district cooling systems built to cool major developments around the UAE over the next five years.
“Here you have one central system, so you can maximise the efficiency of power usage.
“If you have every individual building running its own loading profile for heating and ventilation, they are all going to have their own spare capacity and spare redundancy, so the building gets bigger, the capital cost of construction gets bigger and your structure needs to cope with higher loading rates.
“By taking all that out and putting it in separately you’ve reduced your capital expenditure in the front end of the building.”
One of the first decisions the Drake & Scull design team had to make was whether to choose GRP or steel as the material for the huge looping mains network which will link up all 54 towers with the main cooling plant.
While both have been used successfully on other schemes, GRP was still relatively untested in the UAE on this type of project.
This lack of a local track record persuaded the client to opt for steel, even though GRP was, arguably, a more versatile material.
“Our research and preference led us down the route of GRP - there are lots of types of GRP, but it does have an inherent set of benefits as a product – you don’t get the same wear, you don’t get issues with rust fatigue or bacterial infestation, it’s a smoother surface of pipe so your pumping efficiency is slightly improved and it’s a durable product.
“The concern was that it hadn’t been installed in a district cooling scheme in the UAE before, so it was felt that we should revert back to the main specification, which was steel,” says Lucken.
While little separates the two products in terms of costs, GRP pipe can be installed much more quickly because there is no welding work involved.
The time savings on this particular project would have been somewhere in the range of 18 to 20%.
“Obviously you don’t have x-rays to do, but you have pressure testing to do. With the pressure testing because you don’t have corrosion, once you’ve done a length of pipe you can leave your water in there and pump it into the next bit
“But to flush and clean a steel system, you need to do it in a very timed and controlled way, otherwise it will corrode again,” adds Broadhead.
The decision to opt for steel also meant the construction team had to factor in the recently volatile supply and price situation.
“We were talking to around 40 different countries so we bought within our budget but it wasn’t an easy process and it took us many weeks to get security of delivery because we were calling people in the morning and they were saying, ‘do you want to buy this steel now, if you don’t give us answer, I’m going to sell it to someone else.”
The massive chillers that are being installed on the project weigh in at around 150 tonnes each and have been packaged together in pairs and encased in steel frame modules.
That gives the system the flexibility of being reduced or expanded according to demand while also negating the need to construct a new building to house them.
Once the mains network is fully installed, the Drake & Scull teams will ‘Pig’ the system to remove any unwanted debris inside left over from pipe jointing work.
That will be done by blasting a giant steel brush through it at high speed, using compressed air. Then the system is flushed and ready to go.
||**||Logistics|~||~||~|A major issue for the Drake and Scull team has been coordination and logistics.
The contractor is installing its 1.5 m diameter district cooling network right through the middle of the biggest building site in Dubai, and there are a lot of other contractors that need to be kept on side.
“We do formal handovers where it is literally, in and out. We don’t have weeks to sit around with kilometres of trench open,” says Broadhead.
The job of ensuring this all goes according to plan falls to Nadim Al-Jaouni - a veteran of the US Army Corps of Engineers and construction manager on the project.
It is his task to ensure Drake and Scull’s operations on the site interface correctly with the ongoing building and civils work.
He also liaises with all the lead contractors and consultants to ensure the job runs smoothly.
And that is a difficult logistical balancing act made even more problematic by a shortage of suitably qualified labour.
Al-Jaouni may have thought he had seen it all in his 23 year career in the corps, but even that did not prepare him for Dubai.
“You can’t get good help from temporary agencies,” he says.
“You ask for fitters they send you labourers, you know – last week I told one I wanted five pipe fitters and five helpers for them.
“They sent me nine guys – none of them skilled and one of them with a wooden leg.”
Drake & Scull is also providing meterage for around six thousand apartments in the development and the sub-contract for meterage provision has been put out to tender.||**||