The evolution and current state of cooling towers in HVAC

By Eamonn Ryan

In the context of HVAC, cooling towers are becoming less common, especially in certain parts of the world.

A report ‘Cooling Tower Market by Type (Evaporative, Dry, Hybrid), Design (Natural, Mechanical), Construction Material (Concrete, Steel, FRP, Wood), Flow Type, Technology, Application (Power Generation, HVACR, Food & Beverage), & Region – Global Forecast to 2029’, suggests that the cooling tower market size is projected to grow by a CAGR of 5.3% during the forecast period from USD3.0 billion in 2024 to USD3.9 billion by 2029. BAC FXVE evaporative cooling towers. Supplied by BAC. It notes that the cooling tower market is experiencing significant growth due to increasing industrialisation, urbanisation, and the subsequent rise in demand for energy-efficient cooling solutions across various sectors such as power generation, HVAC, and manufacturing. Stricter environmental regulations and the need for sustainable practices are driving industries to adopt advanced cooling technologies to reduce water and energy consumption. Additionally, the rapid expansion of data centers, which require efficient thermal management systems to prevent overheating, is further propelling the market. Innovations in cooling tower designs and materials, aimed at improving performance and reducing maintenance costs, are also contributing to the market’s expansion. Dry cooling tower segment, by type, is expected to be the second largest segment during the forecast period. Dry cooling towers utilise air to cool and condense the process fluid, eliminating the need for water evaporation. This makes them highly suitable for arid and semi-arid regions, as well as for industries prioritising water conservation and compliance with stringent environmental regulations. Additionally, dry cooling towers are less prone to issues like water contamination, corrosion, and scaling, leading to reduced maintenance requirements and operational costs. The growing focus on sustainability, energy efficiency, and advancements in cooling technology further bolster the adoption of dry cooling towers across various industries, including power generation, petrochemical, and manufacturing sectors. Natural draft is anticipated to be the second largest segment, by design, during the forecast period. Natural draft towers leverage the natural buoyancy of heated air to induce airflow, eliminating the need for mechanical fans and thereby reducing energy consumption and operational costs. Characterised by their tall, hyperbolic structures, natural draft cooling towers are highly effective in dissipating large quantities of heat, making them ideal for power plants and heavy industries. Their low maintenance requirements and long operational life further enhance their appeal. Power generation is anticipated to be the largest segment, by application, during the forecast period. Middle East & Africa is expected to be the second fastest-growing region in the global cooling tower market, by region, during the forecast period. The Middle East and Africa region is experiencing growth in the cooling towers market due to rapid industrialisation, urbanisation, and infrastructure development. The region’s hot and arid climate necessitates efficient cooling solutions for both industrial processes and residential/commercial buildings, driving demand for advanced cooling towers. Reference: Cooling Tower Market, Industry Size Forecast Report [Latest] (marketsandmarkets.com)

Air-cooled systems have increasingly taken over the HVAC space, particularly in South Africa. Unless dealing with very large systems that require water-cooled chillers, the majority of medium-sized HVAC projects now utilise air-cooled solutions. Cooling towers remain vital in large industrial processes but are no longer as prevalent in HVAC applications.

Cooling towers are essential for water cooling applications. They primarily serve as a means to reject or transfer heat, making them fundamental in various industrial refrigeration and HVAC processes. Historically, cooling towers started as simple spray fountains and have since evolved into more sophisticated systems.

Globally the market features numerous manufacturers. In South Africa, competition for cooling towers comes from several companies, with Baltimore Aircoil Company (BAC), Evapco and IWC being the among larger local suppliers. These manufacturers can also focus on different or specific types of cooling tower markets from large field-erected systems, typically for power stations or factory assembled packaged type units for smaller processes.

The cooling tower industry has come a long way since its early days when most systems were custom-built and field-erected rather than factory manufactured. Companies like Evapco and BAC, which started in the mid-20th century, were among the first to manufacture factory-assembled cooling towers. Over the years, these companies have expanded their product lines to include a variety of cooling solutions, adapting to changing market demands and technological advancements. They are used in a wide variety of applications and vary from virtually trashbin size to that required for a power station.

BAC S3E Evaporative cooling towers. Supplied by BAC.

“Cooling tower technology has not advanced at the same rapid pace as electronics or other high-tech fields. The fundamental principles of physics and natural laws limit how much these systems can be improved. For instance, water can never evaporate at dew point, and increasing the size of a cooling tower infinitely will never achieve this. Consequently, significant innovations in cooling towers have focused more on enhancing environmental responsibility, such as developing hybrid products and dry cooling solutions,” explains Andre van der Merwe, managing director of Evapco South Africa.

While cooling towers remain vital for larger systems that require water-cooled chillers and are still highly efficient from an energy consumption standpoint, in the HVAC space they have become less common, especially in water-scarce regions like South Africa. Air-cooled systems have increasingly dominated the market, particularly for medium-sized projects.

In 1982, Evapco took its first step towards global expansion by establishing its presence in South Africa, he explains. Over the years, Evapco has strategically diversified its product portfolio, evolving from a company solely focused on evaporative cooling products such as cooling towers, evaporative condensers, and fluid coolers, to offering a complete full spectrum range of wet, dry and hybrid products. Moreover, the company has ventured into various other market segments, such as large ACC Steam condensers for power generation.

The industry’s focus on sustainability is reflected in the development of hybrid cooling systems, which combine wet and dry cooling methods to optimise both energy and water usage.

“When I started at Evapco we had three products to sell – now we have over a dozen, with our flagship being the Eco hybrid (wet and dry) offering significant water and energy savings compared to traditional cooling towers.

“Cooling towers are among the most fundamental products built by manufacturers, who traditionally identified themselves primarily as cooling tower companies. Evapco, however, has broadened its scope to become specialists in heat transfer products and services, encompassing three types of products: open-circuit cooling towers; closed-circuit fluid cooler; and evaporative condensers; as well as hybrids of them.” Van der Merwe says while some people refer to these three products as ‘cooling towers’, technically they are not.

The global firm does prolific research and development (R&D), while the South Africa operation is a full licensee of Evapco that contributes financially to that R&D. The company boasts cutting-edge facilities, including thermal laboratories equipped with advanced testing capabilities.

While there has been a shift from water cooling in recent years for environmental reasons, Van der Merwe points out that cooling towers are primarily water-saving devices which reject the heat and return most of the water back to the system – as opposed to the once-through system.

“The hybrid cooler, featuring a combination of dry and wet modes of operation, offers significant water and energy savings as it fluctuates between different modes based on ambient conditions. This allows for a more efficient and sustainable cooling solution,” he says.

Dry coolers operate solely based on the ambient dry bulb temperature. While they offer advantages in terms of water consumption, their physical size and weight may pose challenges during retrofitting an installation. Evapco’s adiabatic dry cooler offers substantial water savings compared to the wet cooler, making it a desirable solution in a world facing climate change, high water costs, and stricter regulations. It is a popular option for companies unable to get water quota in some municipalities.

Regarding the advantages of Evapco’s adiabatic condensers compared to air-cooled ones, the adiabatic condensers have lower installed power, a smaller footprint, and higher capacity. This means they can provide more efficient cooling in a compact design. The adiabatic pads are installed on the outside of the condenser unit. Additionally, Evapco offers a free cooling system with solenoid valves that activate the pads and introduce water when needed.

Previously, most designs used the pumped pad system, where water recirculates through a pump. However, this can lead to an increase in dissolved solids concentration if water quality is not closely monitored. As a more practical solution, the one-stream bed system directs water through the bed and straight to drain. Some manufacturers recommend using mineralised water with the pumped pad system, but this can be expensive. Evapco’s adiabatic units utilise the one-stream bed system, which eliminates the need for expensive water treatment.

Cooling towers can be broadly categorised into two types: natural draft and mechanical draft. Natural draft cooling towers operate without mechanical assistance, relying solely on the natural flow of air to facilitate heat transfer.

In contrast, mechanical draft cooling towers use fans and motors to drive air through the system, creating a mechanically induced draft. These can further be divided into packaged or factory-assembled products, which range from small to large sizes, and field-erected systems, which are typically used for larger industrial processes.

Within mechanical draft cooling towers, there are variations such as forced draft and induced draft systems. Forced draft cooling towers have fans installed below the cooling tower fill pack, pushing air through the unit, creating positive pressure. Induced draft systems, on the other hand, have fans installed on top, pulling air through and creating negative pressure. Each design offers different efficiencies and maintenance requirements, tailored to specific applications.

While there are closed-circuit cooling towers with internal coils, these are technically different from traditional open-circuit cooling towers. Open-circuit cooling towers are designed to cool water by rejecting heat through evaporation, returning most of the water to the system, and minimising overall water consumption.

In recent decades, the industry has seen a shift towards more standardised, factory-manufactured products. This transition has allowed for greater consistency in quality and performance. Evapco, for example, initially focused on the refrigeration market before expanding into cooling towers for HVAC. Today, the company offers a wide range of products designed to meet the needs of diverse applications, from industrial processes to data centres.

Importance of certification

Independent certification by organisations like CTI is vital for maintaining consistency and reliability across products from different manufacturers. Van der Merwe emphasises that this certification is crucial for ensuring that cooling towers perform to the standards set by their manufacturers. This is particularly important for large systems where the performance of cooling towers directly affects the overall efficiency of the entire system, including chillers and other components.

Evapco takes pride in being a market leader in CTI certification in South Africa. This commitment to certification helps clients and consultants trust that they are purchasing reliable and high-performing products. It also ensures that systems designed with these cooling towers meet their intended capacity and stated performance criteria.

Prior to the 1960s all cooling towers were erected on site – there was no such thing as a factory-assembled product. That has been a major evolution of the market in the years since. However, transporting cooling towers, especially large units, poses significant logistical challenges. Van der Merwe explains that factory-assembled or packaged products are limited by transportation constraints, such as the size of lorries or shipping containers. For larger projects, cooling towers need to be field-erected on site.

To address these challenges, Evapco has developed containerised ranges of products that can be shipped in standard 20 or 40-foot containers. This approach has proven successful, especially for exports to regions where road transport is not feasible. Containerisation minimises the risk of damage during transit and ensures safe delivery of products to their destination. This approach has been particularly successful for projects where road transport is not feasible, such as those in Nigeria, Ghana, Kenya and Tanzania.

Technological advancements

Looking ahead, Van der Merwe emphasises that the future of cooling tower technology will be driven by a focus on water and energy consumption, as well as cost effectiveness. The industry is dedicated to developing products that are both efficient and environmentally responsible. This commitment is evident in the R&D efforts aimed at creating new materials, construction methods, and technologies that reduce the environmental impact of cooling towers.

One of the promising areas of research at Evapco is microchannel technology, which allows for more efficient heat rejection in a smaller footprint. While still in the experimental stage, microchannel technology has the potential to revolutionise the cooling tower industry by making systems more compact and efficient. Additionally, advancements in motor efficiency, such as the development of IE3 and IE5 fan motors, are contributing to overall system efficiency.

“The growing demand for data centres is another significant trend impacting the cooling tower industry. Data centres are power-hungry facilities that require efficient cooling solutions to maintain optimal operating temperatures and are increasingly adopting free cooling methods, which leverage cooler ambient temperatures to reduce energy consumption. This trend is driving a resurgence in the use of open-top cooling towers for their ability to achieve low water temperatures without the need for extensive mechanical cooling.”

Evapco is also exploring custom solutions for clients with unique water sources and requirements. For instance, farmers with large cold rooms for storing fruit and vegetables are interested in using alternative water sources, such as borehole water or river water. To accommodate these needs, Evapco is developing new heat transfer media and materials that can handle different water qualities, ensuring reliable and efficient cooling in diverse applications.

BAC HXI Hybrid cooling towers. Supplied by BAC.

Comfort cooling and infrastructure cooling

Jakes Nortje, managing director at Baltimore Aircoil Company – Africa (BAC), notes that the air-cooled heat exchanger market has grown significantly in recent years, especially in the HVAC market where VRF systems are very popular.  Both comfort cooling and infrastructure cooling such as the data centre industry have led the trend towards dry cooling.  The key drivers behind this shift are improvements in equipment efficiency, lower maintenance, no water consumption, and a perceived simplicity are some of the drivers in favour of air-cooled systems. 

“Water scarcity is seen as one of the main drivers towards dry-cooled systems.  However, since air cooled systems can be significantly less energy efficient than evaporative systems in certain environments, electricity consumption and the related greenhouse gas emissions are direct trade-offs from an environmental impact perspective.  In a South African context, where Eskom still produces >90% of our electricity, mostly from coal fired power plants, this is a consideration.  Eskom states it emits 1.06kg CO₂e and consumes 2.5l of water per kWh of electricity generated, so a holistic view is required when evaluating potential solutions.  For environmental sustainability, a better view would be to consider the operating carbon footprint of the potential solution, considering not only energy and water usage at the site of installation but also water consumed during the electricity generation process,” says Nortje.

“Linked to above point, evaporative cooling can be significantly more energy efficient than dry coolers depending on the application and conditions as measured across the complete cooling system, and therefore consumes correspondingly less electricity.” 

He adds that most evaporative cooling tower manufacturers have incorporated water savings as a primary design criterion to improve the performance of their products.  “Additionally, effective maintenance of the equipment and water treatment will reduce water consumption during operation.  It is also worth noting that certain industrial cooling towers are designed to operate with process wastewater, therefore not using potable water.”

He explains that BAC has a global focus on innovation and sustainability to continuously improve our product offering.  Nortje says that some of the initiatives are:

• Advances in water distribution systems, fill design, cooling water treatment and airflow systems are some examples which decrease water consumption in traditional cooling towers.  
• BAC hybrid cooling towers include a dry coil with an evaporative cooling tower design which can run dry, evaporative or both pending on the load and environmental conditions.
• BAC adiabatic cooling towers use a small amount of water to pre-cool air by drawing it through wet pads before it flows over finned coils hosting the cooling liquid, allowing cooling systems to operate at the same temperatures and efficiency levels of full evaporative systems.
• Technological advancements in cooling tower controls and load management have also made it possible to optimize water consumption on evaporative cooling equipment.
• BAC are continually looking at ways to increase equipment life, up time, and reduce maintenance costs by incorporating features that improve maintenance access and maintainability; this is a key focus for us in new product development.

Regarding ongoing research and development (R&D), apart from what is confidential, he says that BAC has a 5 000m² R&D center in Baltimore, US employing more than 40 full-time engineers with many development projects in progress at any time.  In general terms, the R&D teams are focused to meet the demands of customers and their applications by improving our products by:

• Higher performance efficiency
• Easier installation
• Easier maintenance
• Longer service life
• Minimising ecological impact

“Product review is part of the innovation cycle and many of our products are in design review to improve operating efficiencies or leverage new materials of construction or manufacturing technologies,” Nortje adds.

In terms of future trends in cooling tower technology, especially in the context of South Africa, he says this is an area of interest: “Firstly, I believe the South African economy will emerge from the current growth challenges and the demand for cooling solutions will increase with local investment.  This bodes well for the local HVAC and refrigeration industry which might work closer together to protect and grow our industry.

“Energy efficiency and sustainability will continue to drive product innovation as regularity compliance increases and as organisations aim towards future net-zero goals. 

“Products will become more intelligent with a wider range of onboard sensory and controls with integration into wider process control systems. 

“Hybrid products and solutions where evaporative-, air-cooled- recovery systems will be used in combination to cater for various environmental considerations.

“Ice storage solutions might come (back) in favour as a store of thermal energy as green energy becomes more available and therefore being able to store thermal energy when electricity is not available.

“Globally, the energy demands of cooling (comfort and data centre) and industrial refrigeration are expected to increase so we envisage a move back towards evaporative cooling systems in some form and this will also happen in South Africa; where energy management will more important and users become more environmentally conscious.”

“As mentioned above, BAC incorporates design reviews in the lifecycle planning of its products, but also aims to solve specific challenges our customers experience and includes traditional evaporative-, hybrid-, adiabatic and jumbo dry systems. 

“We are also focused to further develop our products that solve specific challenges in emerging industries like, data centers, green hydrogen, carbon capture among others,” adds Nortje. 

For Gelatissimo, an authentic Italian gelateria based in Glenhazel, the sporadic cooling water requirements of their machines posed a substantial problem. Supplied by IWC. Gelato goes green – IWC’s water saving, cooling solution Supplied by IWC In the quest to balance efficiency and sustainability, businesses often face significant challenges. For Gelatissimo, an authentic Italian gelateria based in Glenhazel, the sporadic cooling water requirements of their machines posed a substantial problem. Each production cycle necessitated a quick and efficient supply of cold water, which traditionally led to high water consumption and elevated operational costs.   The challenge: high water costs and waste Gelatissimo’s production process was heavily impacted by the need for rapid cooling water. The existing system was not only costly but also wasteful, affecting the company’s bottom line and environmental footprint. This inefficiency underscored the urgent need for a solution that could provide immediate cooling while conserving water and reducing expenses.   Exploring solutions: chiller systems vs practical alternatives The search for a solution began with considering the installation of a chiller. However, the capital investment required, and the physical size of the chiller made this option unfeasible. Gelatissimo needed a budget-friendly, space-efficient alternative that would offer a tangible return on investment without compromising on performance. IWC has not only helped Gelatissimo cut costs but also significantly reduce water waste. Supplied by IWC. The ideal solution: IWC’s complete service IWC offered a comprehensive service package. This included the supply of a compact EWK036 cooling tower, the installation of the entire system, and the necessary water treatment equipment. The fact that IWC could deliver all these services within Gelatissimo’s budget was the critical factor in their decision. IWC’s cooling solutions cater to a wide range of industries, from the small gelateria like Gelatissimo to large-scale manufacturing plants and even power stations. We specialise in providing bespoke, engineered solutions tailored to meet the unique needs of each industry.   Measurable benefits: significant water savings Since implementing IWC’s cooling tower system, Gelatissimo has seen measurable benefits. The new system has dramatically reduced water usage, aligning with the company’s commitment to sustainability and cost-effectiveness. These significant water savings translate directly to lower operational costs and a smaller environmental footprint, showcasing the tangible impact of the solution. Gelatissimo’s experience with IWC is a testament to the power of innovative, budget-conscious engineering solutions. By addressing the cooling water challenge effectively, IWC has not only helped Gelatissimo cut costs but also significantly reduce water waste, paving the way for a more sustainable future in gelato production. Gelatissimo and IWC’s partnership demonstrates how thoughtful engineering and comprehensive service delivery can solve complex industrial challenges. As part of the ongoing relationship, IWC will continue to support Gelatissimo with maintenance and optimisation to ensure sustained benefits.