Centre Point PnP minimises environmental impact

Centre Point PnP minimises environmental impact

By Ilana Koegelenberg

Pick n Pay has officially joined the natural refrigerants movement with its impressive new Centre Point store that boasts a trans-critical CO2 refrigeration system that requires no municipal water.

Photos by John Ackermann

Centre Point in Milnerton, Cape Town, recently got a R260-million total overhaul, including the Pick n Pay (PnP) that was rebuilt in the place of the old building. It opened on schedule on 27 September 2018. This was the first CO2 trans-critical installation for PnP, but not their last …

This revived mixed-use development now comprises three levels of basement, 15 000m² of retail, and two levels of residential apartments.

The project came together pretty quickly. As the installation contractor, the Pro Active Refrigeration installation team, under the supervision of Gary Dawson, started on site on 23 July 2018 and was able to stay on track in terms of the timeline. The plant was started-up two weeks before store opening, which was on 27 September 2018.

CLIENT BRIEF

The client insisted on a trans-critical CO2 system instead of the more traditional sub-critical CO2/R134a refrigeration system.

Absolutely no delays were permitted, the cost had to be no more than 10% higher than the quoted sub-critical system, and no municipal water was to be used to assist cooling.

SYSTEM DESCRIPTION

The refrigeration plant room is located on the rooftop of the new Centre Point Mall and the trading floor is two storeys below at the opposite end of the mall.

To take care of its refrigeration needs, Sphere locally manufactured a booster system with parallel compression. The pack is fitted with 10 Bitzer compressors, four of which run the medium-temperature side, two doing parallel compression, three running the low temperature, and one satellite low-temperature compressor.

The compressors are piped to four circuits: -36°C to the fish island freezer; -28°C to freezer cabinets and freezer store; and -8°C to the medium-temperature cabinets. Two compressors are piped to provide parallel compression of flash gas. Included in the rack is a plate heat exchanger to reclaim heat for heating of hot water to 55°C, which is used for washing and cleaning in the bakery, butchery, food preparation areas, and for staff ablution.

There are four variable speed drives (VSDs), one on each lead compressor.

Operating parameters are set and monitored by a Carel Boss system with a monitor in the plant room and remote monitors for key personnel and Pro Active Refrigeration management.

Condensate water from some of the cabinets, cold rooms, and the air-conditioning air handling unit is harvested and stored in two 5 000l tanks. When ambient temperatures are excessive, the water is filtered and pumped to the adiabatic gas cooler to increase capacity for heat rejection.

Plant safety and compliance with international good practices have been applied throughout the plant. A total of 23 CO2  sensors are installed in the trading area, cold rooms, and plant room with lights indicating green when levels are safe in each area. All piping is labelled to indicate direction of flow and liquid or vapour. The plant room also has an enclosure with pipe stubs for technicians to connect reading equipment to each circuit during maintenance and fault finding.

The hybrid gas cooler was supplied by HC Heat and includes four 910mm EC fans, stainless-steel piping, and integrated Carel controls. Water to the hybrid gas cooler is harvested in the basement from the HVAC, cold/freezer rooms and cabinets, filtered, and then pumped to the roof where it is stored and supplied to the gas cooler as needed.
The entire refrigeration system is controlled and monitored by a Carel electronic control network, which means remote monitoring and adjustments can be done 24/7.

All evaporators are fitted with Carel electronic stepper expansion valves.

Cabinets were supplied by Colcab and installed by Recold.
Piping to the shop floor comprises walled copper pipe specially imported by Matador Refrigeration and runs are over 100m each with a vertical lift of approximately 12m; double risers assist with oil return. High-pressure piping to and from the gas cooler are made of schedule 40 stainless steel, and were tungsten inert gas (TIG)-welded and X-rayed to ensure there were no leaks.

EFFICIENCY MATTERS

The layout of the Centre Point store has been based on maximum efficiency, appealing to the shopper and with least impact on the environment.

Features aimed at maximum efficiency include:

  • High-efficiency Colcab CO2 evaporator coils in all cabinets;
  • High-efficiency ebm-papst fans in cabinets;
  • LED lighting throughout;
  • Acrylic doors on vertical cabinets;
  • Manually operated night blinds;
  • Sliding covers on island freezers;
  • 4 × 910mm-diameter ebm-papst fans with EC motors on the CO2  hybrid adiabatic gas cooler; and
  • ABB variable frequency drive (VFD) on the lead compressor of each circuit.

The efficiency is evident from the compact rack and plant room in comparison to the expanse of the store with a trading area of 1 880m2, the many cabinets, island freezers, cold rooms, and freezer rooms.

Material has been chosen for longevity with least maintenance, such as stainless-steel coils in the HC adiabatic gas cooler; a glass fibre tank for hot water storage; copper/aluminium coils in the cabinets and cold room evaporators; galvanised ducting with open top for overhead CO 2 headers in the store; and stainless-steel droppers to cabinets. PnP was very specific and wanted no refrigeration piping visible to the shoppers.

CHALLENGES

One of the biggest challenges is the fact that the plant room is located quite far from the trading floor because the top floor of the mall is a residential development. This means that pipe runs are quite long with high lift.

As mentioned, the plant is located on the top floor of Centre Point while the PnP store is on the ground floor. The refrigerant risers were 8m in height and the furthest pipe run is 140m from the plant room.

Also, all the piping from the gas cooler had to be of stainless steel and required coded welders.
Because of the residential units, the plant noise level had to be kept to a minimum. The location and direction of installation was considered when placing the equipment; 910mm EC fans were selected for their low noise.

The proximity to the sea meant that all equipment had to be corrosion resistant.
No municipal water was to be used in the adiabatic condenser, so a water harvesting from the cabinet, cold room blowers, and HVAC had to be designed and installed. East Midlands Water designed and supplied a water filtration to cope with the tough task of filtering the wastewater.

SUSTAINABILITY

CO2 has low global warming potential (GWP), which makes it a favourable choice in terms of future-proof refrigerants, explained Merrick Smith, managing director of Pro Active Refrigeration. “When looking at the natural refrigerants, CO2 is able to be used in public spaces like retail trading floors, where other natural refrigerants such as ammonia and propane are more limited. We do expect there to be favourable energy savings from the system and we will continue to monitor its progress.”

CP00 30The new Centre Point PnP store in Cape Town.
Image credit: Pro Active Refrigeration

PnP is very happy with the installation. They have since opened a second store and are currently busy with other trans-critical sites, too. “It seems they have well accepted trans-critical as a way forward,” said Smith.

This is the first project of its kind in a PnP supermarket and was a joint effort between three contractors: Pro Active Refrigeration, Matador Refrigeration, and Sphere. “Through optimistic enthusiasm, the level of cooperation and combined engineering talent ensured a successful project, boasting the high-level quality that our client has come to expect,” explained Smith.

Pick n Pay Centre Point has created a new shopping experience with the assurance that it is truly ‘green’ and will have the least impact directly and indirectly on the environment.

Click here to read the issue of Cold Link Africa

 


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