Mechanical Technology November 2015

⎪ Heating, cooling, ventilation and air conditioning ⎪

HVAC solutions

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.

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. q

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

Mechanical Technology — November 2015

33