Chilling out on the beach
As commissioning of one of the Middle East's largest district cooling plants comes to completion, Alison Luke visits the Jumeirah Beach Residence development to find out what it takes to provide air conditioning for its towers.
The tight timescales and international project teams involved in Dubai’s fast-track construction sector make co-ordination a key issue.
Add to the mix the scale of the projects involved in the city and it becomes obvious why methods that can save time and reduce risk are being applied.
At the Jumeirah Beach Residence (JBR) development the simultaneous construction of 40 towers brought its own challenges.
The method of providing air conditioning to the properties has played its part in ensuring that build programmes could be maintained.
As JBR’s yellow sandstone apartment blocks and gleaming silver columns of the Al Fattan Towers emerge along a 1.7km stretch of the Persian Gulf, a 60,000TR district cooling plant has been taking shape on the outskirts of the site.
When installation began, this was the largest district cooling scheme in the Middle East; it was also unlike any of the existing schemes.
“This was the first large-scale central packaged plant in the region [to be used for district cooling]. Now many of the plants are going that route,” explains Jamie Saunier, technical manager of TAS Packaged Central Plants.
The decision to opt for such pre-fabricated plant was taken by the client at the earliest stages of the project design.
“They saw the value of the reduced time taken for installation on site and pushed for this type of technology,” Saunier explains. “The bulk of your technology is brought in and it reduces your safety risk factor.”
Such was the client’s belief in the benefits of packaged cooling systems that tenders for this equipment were completed prior to MEP contractors being appointed.
TAS was selected as supplier of the plant, however the overall responsibility for this contract was placed within the contractor’s remit.
“The owner wanted a single point of contact [for the MEP services],” explains Saunier.
“They were reluctant to manage more than one large contract, which in this case would have involved the capital equipment and the core technology as well as the MEP infrastructure.”
The procurement of plant prior to contractor tenders gave the client several benefits.
“They realised if you buy the core technology directly from the oem you are guaranteed a performance warranty.
Also, they wouldn’t pay the same mark-up as contractors,” he explains.
“The core technology of the chilling equipment is 40-50% of the project value; that’s a large amount of cost that the owner can save if they procure directly,” he stresses.
The packaged plant was then “free issued” to the MEP contractor to install on the client’s behalf.
Drake & Scull International won the MEP contract for the project and carried out the design and build of the district cooling system.
In addition to ensuring the smooth installation of the packaged plantrooms the firm carried out MEP installation throughout the towers and the civils works for distribution of the chilled water.
It also supplied the cooling towers.
“This was a customer requirement,” explains Saunier, “they wanted a more traditional cooling tower than the package type approach towers that we provide.”
A total of 12 packaged cooling modules, each with a capacity of 5000TR, were supplied by TAS for the project.
These were manufactured at the firm’s facility in Houston, Texas and shipped to site in three batches to meet the schedule for phased installation.
Each of the TAS F-43C packages comprises two Trane Duplex centrifugal chillers in a series counterflow configuration that uses low temperature and low flow strategies.
All services equipment including the chillers, pumps, motor control centres, controls and the associated electrical cabling, pipework and ductwork were installed in factory conditions under an ISO quality process.
The standard TAS packages were adapted to meet particular client needs, which included the use of horizontal pumps.
Replacing the standard vertical pumps meant lengthening the units by 3.5 m and increasing the number of parts they were split into for shipping, but was a simple process assures Saunier.
TAS made additional modifications to cope with the environmental conditions in this Dubai beachside location.
Insulated wall panelling has been used and a severe surface paint coating applied, plus internal air conditioning has also been increased.
In the project’s cooling towers, basin and sidestream sweepers help to reduce the sand and dust that naturally gets introduced into the cooling water circuits.
After completion, the units were split into four sections for transportation and ready for reassembly on site.
“It’s like putting together Lego blocks,” assures Saunier.
Confirmation of this ease of installation came when the first packages were delivered to site in April – the first three packages were installed in just three days.
Subsequent units were installed over a series of weeks to meet the build programme.
Installation of the cooling system began around the same time as general construction on site and continued in parallel with the work.
“In a traditional, non-district cooling world, those chiller plants would have to have been built and finished after or with the buildings,” stresses Saunier, “now its nearly like flipping a switch to provide cooling to the building, it doesn’t impact the building progress and it’s a lot more efficient.”
To ensure this switch-on goes smoothly, tight programming and close co-ordination between TAS and Drake & Scull was essential.
Everything was scheduled on a just-in-time basis. Drake & Scull installed the foundations, electrical infrastructure and pipework needed prior to the packaged plant arriving on site, so the units were simply bolted into place on arrival and connected to supplies, allowing internal commissioning to begin almost immediately.
Saunier explains: “To keep things moving sequentially and working in a parallel path with what’s happening on the rest of the site, we focussed on getting the first units up and running to meet the delivery commitment to the towers, then once that was done we focussed on getting the others commissioned one at a time.
“It is a relatively straightforward process, but for a plant this size there is so much going on that it does take additional co-ordination effort,” he adds.
“We can’t just walk in and run one of these units, the co-ordination aspect with the site must be considered because when these things are running there are things happening outside of our equipment.”
Once commissioned the chiller packages will automatically meet the demands of the project.
A comprehensive control system monitors the demands and switches on and off plant packages as needed to provide the required load.
Distribution of the chilled water from the packaged plantrooms to the individual towers in the Jumeirah Beach Residence is via a 7km loop around the site.
The individual TAS packages feed into a common system via a secondary plantroom, which supplies four 1.5m diameter supply and return pipes.
Tap-off points around the distribution system supply each individual tower via plate heat exchangers in individual energy transfer rooms.
“The heat exchangers are provided to isolate the district cooling water from the building water and the pressures that can be associated with high-rise towers,” explains Saunier.
Commissioning of the district cooling system is nearing completion.
Its effectiveness has already been tested as it is providing a base load to the site during the internal fit-out of the towers, enabling yet further saving of on-site time.