By Eamonn Ryan – technical input by Monyane Hlapolosa, mechanical engineering technologist at consulting engineers WSP
The Oceans Umhlanga development is a mixed use billion-rand development situated in the Umhlanga Village. The consulting engineers for the larger mall were RPP KZN Consulting Engineers and ADX Consulting Engineers, while for the Shoprite Checkers store – one of two of Africa’s largest retailers who anchor the mall – it was WSP.
Development at the R4-billion mixed-use Oceans Mall has reached a critical phase, allowing it to open to the public. Two of the proposed three phases are complete with the five-star Radisson Blu and Oceans Mall, within which is housed Shoprite Checkers, open to the public. The third phase is made up of two residential towers with +/- 500 residential apartments. The mall comprises of a world-class shopping mall with over 100 stores. WHBO was the principal construction contractor.
Energy Partners Refrigeration (EPR) was appointed as the refrigeration contractor for the complete installation, commissioning and maintenance of the refrigeration system due to its expertise and experience in similar projects.
The project initially commenced in 2015 with the first phase of construction beginning in 2018 with the hotel. The project was then put into a sleep period for various reasons, starting up again towards the latter part of 2020. When the hotel was midway through, work began on phase two – the Oceans Mall. The hotel was completed in October 2021 and the Mall in November 2022.
Apart from Shoprite Checkers, the upmarket mall also offers a variety of speciality stores and including international superbrands, such as Burberry, Versace, Armani and Paul & Shark. Apart from retail, the mall will provide a range of leisure and entertainment activities such as Fit 24 (24-hour gym), and 20 world class restaurants.
WSP and Shoprite Checkers ‘well acquainted’
WSP has previously worked with Shoprite Checkers on a number of similar projects, and “we understand them very well”, says Monyane Hlapolosa, mechanical engineering technologist at consulting engineers WSP.
“The biggest challenges in the design related to the acoustics and noise levels, given there is an adjacent residential area. Smart EC (electrically commutated) fans were installed which run a lot more quietly, with fan speed controllers built into them. In the evening when there isn’t much demand for cooling and when ambient noise is low, it has slow rotating fans which gradually ramp up as needed in response to increasing temperature.
“A highlight was the use of glass doors on medium temperature cabinets. This was one of their first stores in KwaZulu Natal to do so, and it resulted in a much reduced plant size and electricity running consumption,” says Hlapolosa.
He explains that there are quite a number of different temperature regimes. For example, the meat cabinet console is between zero and three degrees; the fruit and vegetable cabinet console is between six and 10°C. The typical medium temperature convenience products – such as cheese, yogurt, berries and the like – are between zero and 5°C as an average temperature. Because there are two medium temperature multiplexes, they are evaporated at -13°C to provide a decent temperature differential between the cooler on and air off, thereby maintaining the core productive feature as specified.
The medium temperature multiplexes condensing up to a temperature of about 45°C on a 38°C ambient – albeit one wouldn’t expect KZN to be 38°C very often, though it covers the eventuality. For low temperature cabinets on the trading floor, for example ice cream which evaporates at -32°C, there are glass doors which operate between -18 and -24°C.
“All the traditional medium temperature cabinets have got doors, except where not possible – such as cabinets for the dairy and butchery sections which have thick glass panes over the counters. Supermarkets are evolving towards this direction due to the high electricity price and regular outages, as it reduces electricity consumption and means they can have a smaller cooler. However, it is going to take many years before this becomes commonplace throughout the country,” adds Hlapolosa.
A primary prerequisite was for the Checkers store to be trading from the day the Umhlanga Oceans Mall opened in November. This meant that any challenges could not be permitted to result in delay, but must be resolved through people management to balance the workflow among all contractors’ various projects and to pull in additional resources as needed.
“In respect of the schedule, we were fortunate in this instance that the architect and Checkers started on the project early. While there were delays, they were relatively minimal and related to issues such as the occupational certificate being handed over late, resulting in the store and mall opening about two months later than scheduled. With regards to the installation, it is quite typical for a contractor to be pressed for time. This is because the retailer’s contractor – as opposed to the developer’s contractor – is only allowed into the space over the beneficial occupation period. That gives them 60 days. About two weeks before store opening everything has to be running, which effectively leaves only 45 days to do what is a large installation. So there was considerable pressure on the contractor, not because of any unusual delays during the project but rather because that is the only time available,” he explains.
Difficulties encountered in meeting the design, specification and installation
Hlapolosa describes the biggest challenge as revolving around acoustics, being an upmarket shopping mall. Technical interest in the system installation stemmed from where the plant was situated – in the parking lot of the Umhlanga Oceans shopping mall, with the store itself on a level above the parking area. This raised the risk of noise pollution in an upmarket retail environment.
To avoid noise pollution from the refrigeration system affecting the remainder of the mall, the system installation was designed with enough filters and specialised fans connected to the condensers to reduce noise considerably. The system’s major equipment included compressors from GEA, electronic controllers, cabinets, and multiplexes from Carel, as well as evaporators from Col Coil and Cold Cab.
The cooling, refrigeration, and associated systems for the plant room design of the installation were based on a multiplex and simplex principle, with 255kWr on MT with 2x multiplex racks and 3x simplexes; 40kWr on LT with 18 x simplexes. The units are on R404a refrigerant with an estimated COP 2.4.
“We have got a structure which increases the suction pressure when it does not need to be particularly cool because the meters may be on temperature cycling, for example. On the condenser fan one can also drop the condensing pressure when the weather permits or if it’s late at night when it’s generally quiet. We run them as quiet as possible from an acoustics consideration. Then when there is regular ambient noise during the day, we can run the fans at full speed by dropping condensing pressure,” says Hlapolosa.
Another issue was the nature of being a coastal environment. “We could not permit the stainless steel condensers to be exposed to the highly corrosive environment.”
Energy conservation is always an important consideration and what WSP typically does for the Shoprite Checkers brand is to install high efficiency fans on condensers. The retailer has shifted to LED lights within the cabinet as its more energy efficient compared to typical fluorescent lights. “We have set tight controls so that temperature fluctuations do not far exceed setpoint. This helps with both reducing energy consumption without affecting the food through too high or too low temperatures in the effort to reduce energy consumption,” he says.
During the commissioning phase and during installation, there was remote control over a central controller of each and every individual controller to establish the setpoint and the alarm, which is accessible every moment. The contractor was able to view remotely adjustable temperature logs on what each cabinet is doing at any moment. This is not a full building management system but a console reading for the systems not interfacing to the rest of the building or store, other than an audible alarm within the manager’s office, which indicates when there is an out-of-range cabinet.
“In conclusion, given this is part of a huge upmarket mall installation in Durban, interfacing with the landlord’s professional team was more intense than is often the case with much smaller projects. While in many instances such an environment can lead to challenges or clashes of personality, this was not the case in this project. WSP and Energy Partners are seasoned in this type of project and it was really good working in Durban on such a prestigious mall,” he says.
The broader project
The Shoprite Checkers component is part of a broader project for the entire Oceans Mall, for which the consulting engineers were RPP KZN Consulting Engineers and ADX Consulting Engineers.
Writing in the April issue of RACA Journal, Ashlee Moodley Pr.Eng, director: RPP KZN Consulting Engineers, noted that the design brief was to design a central chilled water plant similar to that of a district cooling plant that would service the various buildings as part of the development. This required multiple chillers, each with standby and duty pumps sets. Efficiency and space requirements played a major role in the selection of the chilled water system. Being less than a kilometre from the shoreline, a water-cooled chilled water system was selected for its efficiency and longevity as there are less components exposed to the elements when compared to air-cooled systems.
He writes as follows: “The central chilled water system was the system-of-choice based on lowest overall energy consumption, lower maintenance costs and most economical plant space requirements. The same type of system is used extensively for mixed use developments in Dubai. The use of a central system allows better provision for redundancy without duplication in numerous separate systems. It also allows better use of diversity which is substantial in a mixed-use development.
The system provides a long lifespan, in the region of 25 to 30 years with proper maintenance. Overall maintenance costs are reduced as there are fewer moving parts when compared to air cooled alternatives.
The bulk of the power supply is centralised, which is more cost effective and economical. The challenge of recovering energy usage and maintenance is achieved by the installation of energy meters for all users as follows:
- Hotel at main supply
- Residential at each apartment
- Retail at each zone Air Handling Unit
The energy meters accurately measure chilled water flow and temperature to summate kW cooling, allowing apportionment of running and maintenance costs according to actual usage. Each of these meters transmit the readings to the central BMS/Billing System to be provided by the electronics engineer.
Air conditioning – central plant
The installation consists of a centralised water-cooled chilled water system with multiple chillers consisting of a mix of base load high efficiency centrifugal chillers and intermediate step load high efficiency screw chillers. The chillers together with the Chilled Water and Condenser Water Pumps are positioned in an enclosed plant room on Level 4 of the development.
The chillers are served by a number of open-circuit cooling towers which are mounted in an open plant area situated at the back of the site so as to avoid noise pollution to the Hotel and residential blocks.
Each chiller is interconnected with one or more cooling towers by means of galvanised steel condenser water piping and condenser water pumps including standby pumps. Chilled water is circulated to each building by means of insulated medium black steel ring main piping and chilled water pumps including standby pumps. At various plantrooms, there is a dedicated heat exchanger and a tertiary chilled water pump station which services each building. This includes each residential block, Hotel block and retail.
Three identically sized pumps with variable speed controllers, two run and one standby, are provided for each. Chilled water shall then be circulated within its own loop per building/user thereby eliminating the risk of a water leak affecting the entire main plant and avoiding unnecessary pumping power losses.
An energy meter is installed in the primary leaving chilled water piping to record the amount of chilled water supplied to the building by the chillers and to track the thermal energy used by the plant.”
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