By Eamonn Ryan
A groundbreaking project in East London marks a significant step forward in sustainable refrigeration and air-conditioning technology.
Future Green Now (FGN) consulting engineers, led by Shaun Hadfield and George Arnold, spearheaded the design and implementation of South Africa’s first integrated system utilising CO2 as a single refrigerant source for both refrigeration and air conditioning at a Massmart Makro store. This innovative approach not only offers substantial environmental benefits with CO2‘s negligible global warming potential but also promises significant energy savings, potentially reducing electrical consumption by 20-25%.
FGN, which specialises in natural refrigerants with a core focus on CO₂, was well-suited to undertake this complex project. “This integrated plant, incorporating air conditioning, represents a significant and novel project for FGN as well,” said Arnold.
Massmart identified East London as a region with significant growth potential, warranting the development of a new store – their first in this location. This project represents a collaborative effort between Massmart, who leases the property, and the property developer M & F Giuricich Developments. Massmart’s decision to establish a presence in East London aligns with their broader strategy to expand their footprint across South Africa. This new, sustainably cooled store reflects Massmart’s growth strategy and commitment to embracing innovative and environmentally conscious solutions.
“The facility incorporates an integrated refrigeration and air-conditioning system, wherein a single plant supplies CO₂ refrigerant to both refrigeration and air handling units (AHUs),” Arnold stated. This design represents a significant departure from the conventional Massmart configuration, which typically employs discrete refrigeration and chilled water air-conditioning systems. “Historically, standard Makro installations utilised independent refrigeration and chilled water-based air- conditioning systems. However, this facility features a unified system where the chilled water AHUs have been replaced with direct expansion (DX) AHUs. The CO₂ refrigerant for these DX units is supplied directly from the central refrigeration plant, representing a notably unique approach.”
Arnold highlighted the innovative nature of implementing such an integrated system on this magnitude. “Based on my knowledge, there is no comparable system currently operational in South Africa. It is highly likely that this represents a pioneering application at this scale and complexity. The store itself is a smaller Makro format, not the expansive footprint typically observed.
Consequently, both the refrigeration and air conditioning capacities are somewhat lower than those of a standard store. However, the integration of these systems remains a unique and commendable aspect of this project.”
The project was executed within an impressively short timeframe, with construction commencing in April 2024 and the store’s opening occurring just weeks before this discussion. “This rapid completion timeline is notable, particularly for a new, green-built project.” Dewing Construction served as the principal contractor,
with Engineering Solutions overseeing the refrigeration components and AirFire Solutions managing the air- conditioning installation.
Despite the unified nature of the central plant, distinct contractors were responsible for the refrigeration and air- conditioning systems, with the interface occurring at the AHUs. “The refrigeration contractor was responsible for the installation of refrigerant piping up to the AHUs, while the HVAC contractor supplied and installed the AHUs along with the associated ductwork and distribution elements.” The air- conditioning system provides climate control for the entirety of the facility, encompassing the retail area, liquor store and administrative offices. The refrigeration plant serves critical temperature-controlled zones, including the main freezer room, main cold room, perishable goods receiving area, and a range of refrigerated display cases located on the sales floor.
The primary drivers for this innovative system integration were a specific directive from Massmart mandating the use of CO₂ as the refrigerant and a parallel objective to enhance overall energy efficiency. “This project specification was further augmented to include the air-conditioning system within this unified plant. Traditionally, air conditioning was provided by a separate chilled water system. However, the specification for this project was modified to utilise a DX CO₂ system supplied by the integrated refrigeration plant.” The successful implementation of a pilot project in Woodmead, Gauteng, which integrated the liquor store’s air handling unit with the CO₂ refrigeration system, served as a precedent and proof of concept for this comprehensive integration in the East London store.
The advantages of this pioneering integrated system are both environmental and economic. “This approach yields benefits in terms of both energy efficiency and environmental impact. CO₂ refrigerant has a Global Warming Potential (GWP) of one. Furthermore, from an energy efficiency perspective, we anticipate potential savings in the range of 20–25% on operational electrical consumption.” The total cooling capacity of the integrated plant is approximately 1 600kw (split between air conditioning and refrigeration).
The AHUs and refrigeration racks were built and supplied by Heating Centre (HC Group), a key manufacturer possessing the capability to produce CO₂-compatible coils engineered for high-pressure applications, specifically cooling coils rated at a 60 bar design pressure and heating coils rated at 130 bar. To accommodate the high pressures associated with CO₂ refrigerant, stainless steel piping was utilised throughout the system, with K65 copper specified in instances where copper was deemed necessary. The blower coils within the cold and freezer rooms were also sourced from HC. The control system is managed by CAREL, and the compressors are Danfoss Bok semi- hermetic models.
The implementation of this innovative integrated system presented notable complexities. “The process was certainly not straightforward, requiring significant effort in integration, particularly as a first-of-its-kind application requiring complex control logic. Close collaboration between the refrigeration and air-conditioning contractors was essential,” Arnold elaborated.
A critical element was establishing seamless communication and control between the central refrigeration plant and the distributed AHUs. This was achieved through a collaborative partnership with CAREL, the control system provider. “Working closely with their team, we developed the specific programming and control logic, resulting in a bespoke system tailored to the facility’s unique requirements.” Throughout the design and implementation phases, the primary emphasis was placed on ensuring the safety and reliable operation of the integrated plant.
System architecture
Arnold detailed the integrated system’s architecture: “The refrigeration system comprises two racks, with heat rejection to atmosphere managed by two adiabatic gas coolers. Stainless steel piping distributes CO₂ refrigerant to the blower coils and thereafter throughout the building to the refrigeration loads – including walk-in cold rooms, freezer rooms, perishable receiving and display cabinets on the sales floor – and also to the AHU. Conditioned air is then distributed via galvanised ducting and diffusers from these AHUs.” A common liquid line network serves both refrigeration and air-conditioning components, and then a suction line to bring it back.
Sensors are positioned throughout the facility to monitor CO2 levels in the building and to detect leaks. A key energy efficiency measure is the utilisation of hot gas for heating. “Instead of directly rejecting heat to the atmosphere, it is first routed to the AHUs to provide heating for the store. Any residual heat not utilised by the AHUs is then rejected via the gas coolers on top of the plant. While hot gas defrost is a common refrigeration practice replacing electric heating, extending this principle to provide heating for the AHUs and the retail space, rather than direct atmospheric discharge, represents a significant energy recovery strategy.”
A notable challenge during the project’s initial phase was the absence of permanent power on-site. “This necessitated a phased commissioning approach, operating only a limited number of units at a time to ensure plant functionality.” This constraint was overcome with the commissioning of the store’s rooftop solar power installation and the completion of the permanent mini sub-station. “The building is equipped with a solar power system to provide supplementary power. The subsequent commissioning of the Eskom mini sub-station provided sufficient power for full plant operation. The integrated system is now operating effectively at its full design capacity.”
Massmart’s response to this innovative system has been exceptionally favourable. “The client has expressed significant satisfaction, particularly as this represents a first-of-its-kind implementation for them. Consequently, they are actively exploring the adoption of this integrated approach for refurbishments at other existing store locations, and FGN is involved in those projects.”
The integrated system is projected to yield substantial benefits in terms of energy efficiency and sustainability. “From a sustainability perspective, the impact is significant due to the utilisation of a natural refrigerant for both refrigeration and air conditioning.” While acknowledging the potentially higher initial capital investment and operating pressures associated with CO₂ systems, Arnold emphasised
the anticipated energy savings. “This installation provides a tangible pilot for measuring the actual energy consumption and savings. Our estimations indicate a reduction in electrical usage of 20–30% for the integrated plant, in addition to the energy offset provided by the solar power installation.”
This energy saving figure is based on the plant’s performance compared to traditional R404a refrigeration and chilled water air-conditioning systems, and crucially, this calculation doesn’t even factor in the significant contribution of the store’s rooftop solar power generation.
The integrated CO₂ system also achieves significant water conservation. “The plant generates hot water for the building by recovering waste heat, similar to the heating provided to the AHUs. This byproduct effectively pre-heats the water before any excess heat is rejected. Furthermore, condensate reclaimed from the AHUs and blower coils for the display cases is reused within the adiabatic gas coolers, reducing overall water consumption during their operation.”
By implementing waste heat recovery for hot water and condensate reuse in the gas coolers, the system minimises its water footprint.
Reflecting on the evolution of refrigeration plant design, Arnold highlighted substantial advancements over the last decade. “The design has evolved significantly. Previously, configurations often involved simplex or multiplex systems for each temperature requirement. Current designs favour a single, large multiplex system providing both low and medium temperature refrigeration, which offers enhanced diversity and operational flexibility. This is particularly advantageous as it allows continued plant operation even with individual compressor maintenance, improving overall system resilience.” He also noted improvements in condenser technology, specifically the integration of adiabatic pads on gas coolers to pre-cool intake air, thereby increasing efficiency.
Addressing the higher initial capital expenditure associated with CO₂ systems, Arnold emphasised the anticipated long- term economic advantages. “From an energy consumption standpoint, the savings are significant. Furthermore, we anticipate that the cost of CO₂-specific components, such as compressors and valves, will decrease as market demand increases. Therefore, the long-term operational costs, particularly energy usage which represents a major expense, are expected to be considerably lower.” The projected substantial reduction in energy consumption throughout the system’s lifespan is expected to offset the initial higher investment.
The integrated CO₂ system at the East London Massmart store serves as a compelling case study for the economic and environmental advantages of embracing natural refrigerant technology, paving the way for a more sustainable future in commercial refrigeration and air conditioning.
