Mechanical Technology

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Heating, cooling, ventilation and air conditioning

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Mechanical Technology — November 2015

Carrier’s AquaEdge™ 23XRV

ultra high efficiency chillers is

the world’s first integrated variable

speed, water-cooled, tri-screw chiller, incorporating significant

breakthroughs in water-cooled chiller technology.

HVAC solutions

water cooling systems are becoming

much more relevant in South Africa.

Describing a local installation to over-

come water shortages, Meikle says that

a highly efficient and water-wise system

has recently been completed at the V&A

Waterfront’s No 1 and No 2 Silo in Cape

Town. No 1 Silo, which was awarded a

6-star Green Star rating, uses an under

floor displacement air-conditioning sys-

tem with extraction through the ceilings

to achieve energy efficiency and good

indoor air quality.

“A district cooling and heating system

has been implemented that will supply a

total of 6.9 MW of cooling via two Carrier

23XRV chillers and two Carrier 30XW-V

cooling and heating chillers. The 23XRV

tri-rotor screw chillers are known to be

the most energy-efficient and robust

water-cooled screw chiller in the world,”

Meikle claims.

The district cooling plant will also

supply Silos 3 to 6 with cooling water

and the 30XW-V variable speed screw

heat-pump chillers will provide hot water

for space heating in the buildings.

Another significant local success story

has been on the new-build power station

projects in South Africa, at Medupi and

Kusile. “To date we have supplied a large

number of chillers to these two projects,

for the turbine halls and for a multitude of

substations and administrative buildings.

Cooling is critical in these applications,

two chillers have been installed for each

sub-station, a duty unit and a standby,”

Daubern tells

MechTech

“While water-cooled chillers are

used for the auxiliary bays, air-cooling

is preferred for the substations, Ambient

conditions, availability of water, mainte-

nance, corrosion factors and operating

hours influence the choice between air- or

water-cooled chillers,” he explains.

“Green buildings of today are de-

signed to consume the least amount of

natural resources, of which water is the

priority. The system that will utilise the

least resources, in most cases, will be

water-cooled chillers, combined with

dry-coolers or hybrid cooling towers with

grey water top-up. Alternatively, ground

source water could also be investigated.

Failing this, an air-cooled chiller is the

next best option to reduce water con-

sumption,” says Daubern.

Key to Carrier’s energy efficiency

improvements is the sophistication of

its new Chiller Plant Manager. “Our con-

trollers offer full monitoring, diagnostics

and control capabilities to automate and

manage chiller plant rooms: the motors,

pumps, fans and compressors. These can

also be interfaced with building man-

agement systems (BMSs), to manage

start and stop sequencing and to adjust

cooling demand based on the number

of people in the building, for example,”

Daubern informs

MechTech

“Efficiency now has a lot more cred-

ibility,” he believes. “As well as offering

variable compressor speed and variable

flow units, we are now also moving to

variable speed fans, which further reduce

power consumption,” he says.

Recently introduced to its range are

the XAV and the 30XWV variable speed

screw compressors, along with the ultra

high efficiency 23XRV, which will also be

used in a new 6-star Green Star tower

block in Waterfall Park in Midrand.

Carrier has also doubled the capacity

of its 5.0 MW, 19XR chiller. “The new

19XRE, high efficiency variable speed

chiller has a two-stage compressor that

can deliver up to 10 MW of cooling. This

means that we are able to supply deep

level mine ventilation solutions to over-

come high condenser water temperature

and high lift conditions,” he concludes.