Inside a state-of-the-art air-conditioned banana ripening facility

By Eamonn Ryan

Beyond the advanced refrigeration systems essential for fruit ripening, Farmwise’s facility features robust air conditioning infrastructure to maintain stable environmental conditions in the pre-cooling and packaging zones.

Zire-Z entrance. All images © RACA Journal

Bracken Refrigeration Services (BRS) has successfully completed a significant in-house agricultural facility project, DCS-ZIRE which is part of the Subtropico Group, a fresh produce centre with cold rooms, ripening rooms and a fully functional distribution centre in north Pretoria. The project involved the design and installation of a Farmwise packing facility and sophisticated ethylene-ripening within the same building – primarily for bananas, but also a wide variety of produce including apples, oranges and avocados.

The project, spearheaded by Bracken Refrigeration Services project manager Morné Seymore, commenced with an initial requirement for 23 ripening rooms in mid-March 2020 and reached completion within approximately five months, despite challenges posed by the initial stages of the COVID-19 pandemic.

Despite these challenges, including brief work stoppages due to both material shortages and COVID-19 related compliance requirements, the project progressed steadily from its March 2020 start to its conclusion in August/September of the same year, including a final month to address minor snags.

Following the successful completion of the initial phase in 2020, this collaboration between Bracken Refrigeration and DCS-ZIRE Subtropico’s continued and involved a second phase in 2022, followed by this current third phase.

The Farmwise precooling and boxing area.

Environmental conditioning for pre-cooling zones

Beyond the critical refrigeration systems designed for precise fruit ripening, the facility also incorporated significant air conditioning infrastructure to maintain optimal environmental conditions within the pre-cooling and boxing areas utilised by Farmwise. The detailed ductwork design for this system was handled by BRS.

Seymore says: “We also supplied the air conditioning rooftop package units for these zones. Specifically, we provided four air-cooled rooftop packages, each with a capacity of 240 000 BTUs, to service the areas not enclosed within insulated panels.” This resulted in a substantial air conditioning capacity, totaling approximately 960 000 BTUs or 281 kilowatts. These units were described as “off-the-shelf, eco rooftop package units that we import under the brand name ‘Echo’.” While acknowledging the possibility of a slight oversizing, Fourie emphasised that the primary design consideration was ensuring adequate airflow throughout these large processing spaces. “We opted for slightly larger units to guarantee the necessary airflow.”

The processing area is characterised by conveyors and other equipment, with a network of rigid ducting with air distribution grilles overhead. To achieve a comfortable and controlled environment suitable for pre-cooling and packaging operations, BRS implemented this significant air conditioning system. This resulted in a completed installation, showcasing the four package units mounted on support frames with meticulously installed rigid ductwork extending into the building.

Purpose-built ripening facility featuring precision environmental control and advanced airflow engineering

Seymore explains that the project was specifically initiated to create a dedicated environment for ripening a substantial quantity of bananas. “The core focus was to efficiently ripen the bananas. However, the scope of the project expanded over time to encompass a packing area within the same building, streamlining the post-harvest process. The facility also includes a specialised holding area equipped with a cooling system designed to bring the produce down to precise temperatures before being moved via a conveyor system for further processing.”

Another significant obstacle was the sourcing of copper fittings. Faced with supplier issues, the BRS team had to adapt by themselves designing and fabricating T-fittings for the copper pipes directly on-site. This resourceful solution not only kept the project on track but also deeply impressed the client, with the custom fittings reportedly still in perfect working order.

Subtropico’s decision to establish a state-of-the-art banana ripening facility stemmed directly from the significant challenges faced by banana producers in South African produce markets.

Traditional, often publicly owned, ripening facilities were proving inadequate due to their inefficiency and poorly maintained water- chilled plant systems. This resulted in substantial losses and frequent insurance claims for Subtropico, which handles a high volume of bananas nationwide. Prompted by these limitations, Subtropico’s management opted to build a brand-new, purpose- built ripening infrastructure.

The design for this facility, leveraging a standard of 30-kilowatt cooling capacity for a 30-pallet ripening room, was precisely tailored to DCS-ZIRE Subtropico’s requirements for efficient banana ripening, based on the volume of bananas needing to be processed within a specific timeframe.

The initial phase, comprising 23 ripening rooms, was successfully completed by BRS within just five months. This rapid success, however, quickly highlighted the facility’s immediate need for expansion, as even 23 rooms proved insufficient for the rapidly growing banana volumes. All rooms were consistently full, leading to an immediate demand for eight new rooms, and a subsequent third phase ultimately increased the total number of ripening rooms to 42.

The area handles a substantial volume of bananas.

Switches in equipment came as and when alternative products were deemed to offer comparable quality at a more favourable price point. Airflow within the ripening rooms was a critical consideration, leading to an upgrade in fan capacity. “We upgraded the fans from 0.75kW to 1.1kW to give us a bit more airflow in the rooms,” Seymore explains. These higher-capacity fans were supplied by AMS (Air Movement Supplies).

Beyond the core refrigeration components, the facility incorporated a range of other essential equipment. BRS manufactures the electrical DB boards in-house. The crucial control system, responsible for regulating temperature, humidity, ethylene levels (essential for ripening) and CO2, was sourced from CAREL. Dixell Controllers were also integrated into the system. Seymore noted a long-standing relationship with CAREL for many years for customised control systems, allowing for tailored solutions to meet specific client needs. A commitment to long-term performance and minimising potential issues for their clients drives their choice of suppliers.

Electrical components, including switchgear, were supplied by RA Distributors, a local South African company known for its quality ACDC-branded products. BRS handles the wiring and testing of the DB boards at their facility before shipping them to the site for installation. The insulated panels forming the structure of the ripening rooms were supplied and installed by Panelman Engineering in Rosslyn, Pretoria. These panels were specified as 100mm thick with a density of 15 DV and a standard white chromadek exterior with aluminum finishing. Access to the ripening rooms is facilitated by Stab-a-Load sectional vertical lifts and motorised doors, which also feature a manual override for operation during power outages, a practical consideration in the South African context.

The DCS-ZIRE Subtropico facility utilises a 30kW system featuring a split condensing unit, which they refer to as a ‘receiver set button on’ with the receiver set on the roof. This configuration places the compressor and receiver unit inside the building, typically on top of the ripening rooms, while the condenser unit is located externally.

Inside the ripening rooms, dual discharge coils are employed, either from HC Group or Metraclark. This design ensures efficient and even cooling by blowing air outwards from the sides of the unit, circulating it through the stacked bananas, and drawing air back in from the bottom. This system – designed by BRS many years ago – has proven highly effective over the years of installations across South Africa, as well as across southern Africa.

Seymore states that there were “actually no challenges” beyond the initial COVID-19 related delays. This is due to the team’s extensive experience with such installations, and even in the event of technical issues, such as a control system malfunction, suppliers like CAREL are known for their prompt on-site support, often responding on the same day.

Minimising power consumption is a significant benefit for the client, hence the use of Copeland scroll compressors in many applications compared to older compressor types which, given there were ultimately 42 rooms, delivered considerable energy saving. Seymore highlights the challenge of finding a 1.1kW fan that delivers the same airflow as current models but with significantly lower energy usage. For the DCS-ZIRE Subtropico project, energy efficiency was also addressed through the implementation of lower voltage (12-volt DC) systems for certain control components and the use of LED lighting throughout the ripening rooms, contributing to a reduction in overall energy consumption.

The scale and the significance of the client, Subtropico, are what make this project unique to BRS. Seymore explains: “You rarely get a project of 23 rooms in a single project – even 10 would be a large project, and then to complete it in five months is something we’re proud of.

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