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Africa’s largest transcritical CO2 cold storage facility

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By Benjamin Brits

The uniting of existing-facility owners and an international logistics company has produced a new 11 000m2 facility in Hammarsdale, KwaZulu-Natal.

Maersk, with their new strategic partner, has established this as their second dedicated storage facility site in South Africa and will trade under the name of Precool Cold Storage. The company’s CEO, Manny Dos Anjos says, “Our mission is to be the preferred cold storage provider for temperature-controlled solutions throughout the perishable industry, providing flexibility to customers.” The partnership further increases Maersk’s capabilities in serving the perishable industry as the new facility was designed and developed specifically for this customer-segment.

The immense contiguous piled retaining wall was part of the substantial civil works on the site due
The immense contiguous piled retaining wall was part of the substantial civil works on the site due
The compressor sets in the refrigeration plant room.
The compressor sets in the refrigeration plant room.
The control panels for the facility.
The control panels for the facility.
The transcritical CO2 refrigeration system has a total installed capacity of 5.28MW.
The transcritical CO2 refrigeration system has a total installed capacity of 5.28MW.

The collaboration came about as Maersk heard of Precool Cold Storage’s expansion plans of the existing facility as they too were looking for an opportunity to share global logistics solutions as part of their growth strategy to service a larger portion of the supply chain. The parties got together, combining their respective business proposals, revealing a favourable outcome both ways, and thus an agreement was concluded.

The expansion increases the capacity of the current operations that can now handle in excess of 12 500 pallet spaces, between the two facilities, in eleven different chambers, which are capable of temperatures between ambient
and -25°C.

The project was launched in March 2019 and completed in February 2021. The project timeline was, as could be expected, affected by Covid-19 related delays as with so many projects in 2020, and was also hindered by weather setbacks on site due to an extraordinarily heavy rainy season.

Starting out as a wild plot of land at the ground breaking, and overseeing the project with more than 20 years’ experience in the cold storage arena and prior experience in the meat trade, was Precool Cold Storage’s CEO, Manny Dos Anjos who oversaw the development with the assistance of the appointed architect and engineers. Dos Anjos also specified the requirements of the refrigeration and electrical systems for the project.

The size of the new facility was based on the direct correlation and maximum utilisation of the space available for the expansion, and can now accommodate an additional 7 500 pallets of commercial refrigerated product, as well as 2 500 sterri-slots, for fruit requiring specialised cooling.

As Precool Cold Storage, the plan for the new facility is foremost to grow their existing business with the main focus on serving the South African citrus export industry, through the Durban Port, where volumes have been growing rapidly according to information published by the Citrus Growers Association of South Africa.

The 11 000m2 facility can handle in excess of 100 trucks per day. Photo by © Precool Cold Storage
The 11 000m2 facility can handle in excess of 100 trucks per day. Photo by © Precool Cold Storage
The compressor sets in the refrigeration plant room. Photo by © Precool Cold Storage
The compressor sets in the refrigeration plant room. Photo by © Precool Cold Storage
The steri-rooms have a 2 500 pallet capacity. Photo by © Precool Cold Storage
The steri-rooms have a 2 500 pallet capacity. Photo by © Precool Cold Storage

The choice of location is that the facility is strategically located away from the congested Durban port area, and in proximity of the N3 Highway which is the main corridor, linking Africa’s largest harbour to the rest of Africa. This location is aligned to Maersk’s strategy, as it created the opportunity for a faster truck turnaround time, being away from the busy bottlenecked Durban port areas.

There are now seven additional loading bays that can accommodate large trucks, and the facility can now easily handle in excess of 100 trucks per day. All loading bays lead to a temperature controlled holding area where product is held before being moved into dedicated temperature controlled storage rooms, to ensure the cold chain is maintained.

This facility will also be used as a model in the Maersk expansion strategy and by successful operation will result in it being rolled out to other sites throughout South Africa.

Design specifications and resultant state-of-the-art cooling system

The design specification for the refrigeration system installed at the facility is an energy-efficient multi-temperature transcritical CO2 system, designed by industry specialist Wynand Groenewald, that takes the important factors around global warming and environmental impact into account. Both Precool Cold Storage and Maersk strive for a minimal carbon footprint. CO2 is one of the refrigerants of the future. The refrigerant boosts a global warming potential of 1, making it virtually climate neutral.

The resulting installation is a facility that can operate from ambient to -25°C, with a total installed capacity of 5.28MW through this transcritical CO2 system. This consists of the following elements:

    • Medium Temperature Capacity of 3 720kW @ various suction temperatures
    • Low Temperature Capacity of 1 560kW @ -25°C

The refrigeration installation includes five transcritical CO2 booster systems with parallel compression (on four of the five systems). Each system has an adiabatic gas cooler to increase energy efficiency. There is one system for the airlock, two for the sterilisation rooms (split over the two rooms for redundancy) and two for the holding rooms (also split over the two rooms for redundancy).

Parallel compression was included as it works alongside the medium temperatures and handles any flash gas that comes from the receiver vessel and makes a system more efficient because the gas is being handled at a higher evaporation temperature and the higher the evaporation temperature, the more efficient the compressors. Instead of dropping all the flash gas down to the evaporation temperature in the medium temperature system, parallel compressors are used.

The steri-rooms as well as the holding rooms were designed to operate as either chillers (medium temperature rooms) or freezers (low temperature rooms), depending on the demand. The unique design of the facility allows each individual room to operate at the desired temperature without affecting any of the other rooms within the facility. Suction gas from the rooms is diverted to the required compressor suction group to obtain the required temperature.

Heat-reclaim heat exchangers are installed on the refrigeration racks to provide ‘free’ heat in terms of hot water. 400kW can be used for heating water from 20°C to 60°C, when operating at only 30% of the installed capacity.

There is also a hot gas defrost function for low temperature applications to reduce electrical usage (instead of electrical defrost). Defrost is done by controller and defrost cycles occur at different times as there are quite a few fan coil units in each of the rooms.

Steri-rooms are included at the facility because they form an integral part of export produce and strategically allow Precool Cold Storage to accommodate as many services as possible for the entire cold chain. Some countries require different temperatures and different protocols that must be complied with in order to pass as export quality.

Most of the export products handled by the facility come from the North of the country and the new facility is both a DALRRD and PPECB approved facility in the chilling of fruit and other perishable products, according to the required temperatures for such export. This accreditation ensures fulfilment for required protocols.

Project challenges

One of the main challenges during this project was the earthworks that needed to be done and pushing through the rainy season (and flooding). Because of the gradient on the property this required extensive civil work that included piling and erecting various immense and complex earth retaining systems across the property which also contributed significantly to the costs on the project.

In terms of the refrigeration, the ability to change the rooms from low temperature to medium temperature and vice versa, as specified by the client, was a noteworthy challenge for Commercial Refrigeration Services (CRS) who designed and installed the refrigeration.

Each of the cold rooms are fitted with a mobile racking solution. © Precool Cold Storage© Precool Cold Storage
Each of the cold rooms are fitted with a mobile racking solution. © Precool Cold Storage© Precool Cold Storage
The steri-room racking that was designed and developed by Manny Dos Anjos. © Precool Cold Storage© Precool Cold Storage
The steri-room racking that was designed and developed by Manny Dos Anjos. © Precool Cold Storage© Precool Cold Storage
The temperature-controlled airlock/holding room where the deliveries enter and are allocated to eith. © Precool Cold Storage© Precool Cold Storage
The temperature-controlled airlock/holding room where the deliveries enter and are allocated to eith. © Precool Cold Storage© Precool Cold Storage

According to CRS engineers, generally if you think about any cold storage facility, it will have a dedicated freezer room and cold room (so it operates as either of these). Precool Cold Storage wanted the functionality of multi-temperature choice in order to maximise the utilisation of the cold store throughout the year. Essentially being able to operate as a medium temperature cold store or freezer facility while waiting for the next season’s produce to be ready for export.

The coils had to thus be designed to handle both option’s operation. The difficulty came in here for CRS, but managed to come up with a design solution for the low temperature. Not all the coils would then operate when low temperature options are implemented. This particular design was something CRS had not done before, so the piping is quite different because with this CO2 system there is not only a common liquid line that goes to all of the evaporators, but also a common suction line that had to be designed to ensure proper operation under medium temperature or freezer applications – so this method changed the design and the installation in the plant room with changeover valves, and so on.

Energy efficiency

The system’s impact on energy efficiency and sustainability includes an energy efficient CO2 system with adiabatic gas coolers, parallel compression, hot gas defrost and heat reclaim. Variable speed drives (VSD) on driven compressors, electronic controls and permanent magnet compressors also provide exceptional efficiency. The use of CO2 is relevant to address the environmental aspects in terms of global warming potential.

The hot gas from the system that comes from the discharge of the medium temperature compressors is circulated through the system and this defrosts the coils instead of using electrical defrost elements, which creates a substantial saving. This energy saving technique works very well and has been vastly implemented worldwide – basically using free heat through the discharge. The coils do have electrical elements as a backup, as this was specified by the client, but they won’t operate unless manually switched on if required.

The 3-phase electricity box in the electrical plant room. © Cold Link Africa | Benjamin Brits
The 3-phase electricity box in the electrical plant room. © Cold Link Africa | Benjamin Brits
Guard beams are installed at every entrance to protect against any forklift bumps or damage. © Cold Link Africa | Benjamin Brits
Guard beams are installed at every entrance to protect against any forklift bumps or damage. © Cold Link Africa | Benjamin Brits
The gas coolers installed outside the main refrigeration plant room. © Cold Link Africa | Benjamin Brits
The gas coolers installed outside the main refrigeration plant room. © Cold Link Africa | Benjamin Brits
The electrical plant room. © Cold Link Africa | Benjamin Brits
The electrical plant room. © Cold Link Africa | Benjamin Brits

VSDs have been around for a long time and play a key role in driving efficiency. On each temperature group they allow the user to start up the pack slowly (soft start) reducing the initial energy use at the start and also allows the system to operate at different capacities – essentially meaning one does not have to operate the plant at 100% capacity all the time, wasting energy – if you need to run down to 10kW, this can be done, where all of the compressors will be off, except the one with the variable speed drive in operation.

Incorporating the next generation of permanent magnet compressors for CO2 applications with outstanding eco-efficiency to achieve new levels of energy efficiency, along with the mechanical capacity control, which is also new for transcritical CO2 applications, system efficiency increases considerably, in full and part-load operation, was a direct requirement of the client.

Unique elements

Having the biggest transcritical CO2 refrigeration installation in Africa is already top of the uniqueness scale for the project, and speculatively this facility has one of the biggest CO2  installations in the world (verification of this is not possible).

Another unique element is that the facility can handle both fresh fruit and out-of-season fruit, and can switch over room-by-room to frozen storage and reach temperatures of -25°C quite easily and quickly. Multi temperature facilities such as this are very rare, in fact, the facility can service all perishable products across the range.

This facility has been designed by Dos Anjos, bringing many years of practical experience and knowledge of the industry, to make it operationally as easy and user friendly as possible, to ensure optimal quality of the clients’ precious product.

List of professionals and suppliers

 Project name  Precool Cold Storage, Hammarsdale, KwaZulu-Natal
 Owner  Precool Cold Storage
 Developer  Precool Cold Storage
 Architect  Nash Lakraj
 Project manager  Manny Dos Anjos
 Engineering  Electrical  Gary Wilson
 Structural  Alan McNaughton
 Geotechnical  Marco Pauselli
 Civil  Tony Ferreira
 Contractors  Earth works  Precool Cold Storage
 Earth retaining structures  Precool Cold Storage
 Main building  Precool Cold Storage
 HVACR  Commercial  Refrigeration Services
 Structural steel  Avellini Bros
 Electrical  Qualelect
 Product suppliers  Insulated panels  Kingspan
 Insulated panel installation  Rudnev
 Mobile Racking  Barpro
 Dock Levellers  Stab-A-Load KZN
 Sectional Docking Bay Doors  Stab-A-Load KZN
 Docking Bay Shelters  Stab-A-Load KZN
 HVACR  Commercial Refrigeration Services
 Blower coils and gas coolers  HC Heat Exchangers
 Controls  Danfoss
 Compressors  Bitzer
 Oil management  Temprite and Emerson
 Receivers  Viola
 Drives  ABB
 Valves  Refrigera and Castel