Our ability to efficiently cool the interior of buildings and industrial structures has never been more critical. Global climate change, resource scarcity, and the demand for “greener” heat waste management drive HVAC engineers to consider energy and water efficiency when designing or renovating systems.
The global energy demand for cooling is forecasted to grow by a frightening 45% by 2050 (compared with 2016 levels). This demand makes energy efficiency a primary driver for modern cooling system solutions, prioritizing flexibility and scalability.
Chillers and cooling towers are two solutions traditionally employed in large-scale and specialized cooling systems. Understanding the difference between the two and their potential synergy is critical to making the right decisions.
What are cooling towers?
Cooling towers are devices that reject waste heat to the atmosphere by cooling a water stream to a lower temperature. They are traditionally installed in tall structures that dispose of heat waste in industrial structures (like oil refineries, data centers, and power plants) and large-scale HVAC systems in commercial properties (like hospitals, hotels, shopping malls, and multi-tenant buildings).
How do cooling towers work?
Cooling towers use the evaporative cooling principle of air-to-water contact. Hot water is usually pumped to the top of the tower and spread over fill media, such as slats or film, to increase the surface area for evaporation. This water is then sprayed onto these surfaces inside the structure, and air blows over them naturally or with an electrical fan motor. As the air moves through the tower, a small portion of the water evaporates, removing heat from the remaining water.
This cooled water is then collected at the bottom of the tower and recirculated back into the system to absorb more heat. Through this process, cooling towers efficiently transfer heat from the water to the atmosphere while maintaining the system’s efficiency.
There are numerous types of cooling towers available today, usually categorized according to their mechanism of operation:
- Natural draft cooling towers use natural convection to move air through the tower, suitable for large power plants due to low operational costs.
- Forced draft cooling towers employ internal fans to circulate air through the structure to increase its cooling efficiency.
- Induced draft cooling towers use top-mounted fans to pull air through the tower.
- Crossflow cooling towers push air flows vertically, and the water flows horizontally, optimizing the heat exchange processes.
- Counterflow cooling towers, in which water falls vertically while air moves upward, allow more efficient heat transfer and are commonly used in industrial applications.
[ Source: Mechanical Knowledge ]
Benefits of Cooling Towers
1. Energy Efficiency
Cooling towers significantly enhance the energy efficiency of HVAC systems. They effectively reduce your systems’ reliance on energy-intensive solutions by using water to absorb and dissipate heat into the air.
2. Cost Savings
Cooling towers use less energy, lowering electricity costs. Their long lifespan and durability also make them an excellent long-term investment.
3. Environmental Impact
Another outcome of the energy efficiency of cooling towers is their role in reducing the carbon footprint of buildings. Their contribution to improving your cooling system’s efficiency is eco-friendly and industry-friendly, helping you achieve green building certifications like the BREEAM certification and LEED Platinum.
4. Improved Thermal Load Management
Cooling towers provide an accurate, consistent, and scalable cooling capacity. These features in your HVAC design can be vital in buildings requiring precise temperature and humidity levels for occupant comfort or operational efficiency. Examples include large commercial buildings, server farms, hospitals, and hotels.
What are chillers?
[ Source: SIEMENS ]
Chillers remove heat from liquids using the refrigeration cycle and expel it into the atmosphere. They are typically used in HVAC systems, industrial processes, and district cooling.
[ Source: HVAC Investigators ]
What do chillers do?
Chillers differ from cooling towers in their method of operation. The coolant used (usually water) remains in a closed-loop system and is recirculated. Chillers employ compressors, condenser heat exchangers, and evaporator heat exchangers to expel as much heat as possible into the atmosphere.
While chillers come in various sizes and are suitable for different applications, there are two main types of chiller devices: air-cooled and water-cooled chillers.
- Air-cooled chillers rely on ambient air to absorb the heat from the refrigerant.
- Water-cooled chillers use water as a cooling medium.
[ Source: North Slope Chillers ]
Benefits of Chillers
1. Quiet Operation
Many cooling systems produce high noise levels, even in noisy industrial settings. On the other hand, well-maintained chillers produce relatively little noise or vibration because they have few dynamic components.
2. Greater Flexibility and Temperature Control Accuracy
Chillers are much more flexible than most cooling systems. They can be modular, adaptable, and configured to operate in various indoor and outdoor environments and weather conditions. For example, while a cooling tower may be sufficient for your building’s cooling needs in the Winter and fall, during the hotter months of the year, you will need a water chiller to manage your excess heat waste.
3. Water conservation
Since chillers recycle water in a closed-loop system, there’s little to no water waste involved. This is especially important for buildings looking to implement robust sustainability policies and in areas where water scarcity makes it costly to let water evaporate into the atmosphere.
Cooling Tower vs. Chiller: The Key Factors to Consider
Chillers and cooling towers do what their names suggest: they cool things down. However, they have different mechanisms for doing so and usually play slightly different roles in heat waste management.
Cooling tower |
Chiller |
|
Function |
Remove heat from water discharged from a condenser or heat exchanger unit into the surrounding air. | Expel heat from the coolant material and release it into the surrounding air. |
Cooling Mechanism |
Vapor-compression or absorption refrigeration. | Uses vapor-compression or absorption refrigeration cycles. |
Common Applications |
Power plants, refineries, and industrial applications that produce significant heat waste volumes. | Large-scale commercial and residential air conditioning, data centers, and industrial processes in plastics and beverage industries. |
Energy Efficiency |
Low energy consumption. They are generally more energy-efficient than chillers, but this depends on factors such as climate and chiller type. | Moderate energy consumption |
Water Waste |
Significant amounts of water waste due to evaporation, blowdown, and drift. | Little to no water is wasted. |
Space Requirements |
Significant outdoor space for installation. | Compact and modular. |
Maintenance |
Relatively low | More complex and specialized |
Operational Costs |
Low | High |
Choosing between a chiller and a cooling tower depends highly on many project specifics, such as climate, terrain, water scarcity, and local regulations on industrial or commercial structures.
In many cases, the best solution is a combination of a cooling tower and a water-cooled chiller to minimize costs and enhance efficiency.
However, it’s worth noting that maintaining these solutions has very distinct requirements. Cooling tower maintenance involves regular cleaning to prevent scaling and corrosion and continuously monitoring water levels and heat exchange. To maintain chillers’ efficiency and proper functioning, you need to inspect components like compressors, condensers, and evaporators and monitor refrigerant levels for optimal performance.
How to Optimize Your Cooling Systems for Optimum Energy Efficiency
Cooling Tower Cycle of Concentration (CoC)
The cycle of concentration (CoC) is a crucial factor in cooling tower operation. It refers to the ratio of the concentration of dissolved solids in the cooling water to the concentration in the make-up water. Optimizing CoC is vital for several reasons:
- Water Efficiency: Higher CoC means more cycles before water needs to be replaced, reducing the amount of make-up water required.
- Cost Savings: Efficient water use reduces water and chemical treatment costs.
- System Longevity: Properly managing CoC minimizes scaling and corrosion, extending the life of the cooling tower and related equipment.
- Environmental Impact: Reducing water consumption and chemical use lowers the environmental footprint of the cooling system.
Operators should regularly test water quality and adjust treatment protocols to maintain an optimal CoC, balancing water savings with system protection.
Water Management and Leak Prevention
Water’s heat conductivity as a cooling medium makes it almost impossible to cool indoor spaces and industrial processes without it. However, water is becoming scarce, and its conservation is a prominent concern. Consider intelligent water management solutions for cooling towers and water-cooled chillers to optimize water usage and prevent water damage. Scalable and cost-effective solutions like Wint’s water intelligence platform can integrate with your building management systems and eliminate water waste throughout your project.
Regular Maintenance and System Efficiency Monitoring
Continuous monitoring of your cooling systems’ efficiency and resource consumption is essential for a data-driven building management strategy. System efficiency will enable you to save water resources, which is critical to any ESG strategy. It can also indicate potential malfunctions or wear-and-tear on your cooling system components. However, do not wait for problems to escalate before taking action. Instead, follow the maintenance guidelines and requirements provided by the equipment manufacturer.
Maintenance requirements typically include regularly cleaning the cooling tower’s fill and drift eliminators, reviewing chiller refrigerant levels, and monitoring compressor performance. These tasks ensure that the system operates efficiently and help you avoid costly system failures.
Load Balancing and Variable Frequency Drive Fans
The energy consumption of the moving parts in your cooling system (such as pumps and fans) doesn’t need to be constant or high. Modern cooling systems can intelligently and automatically adjust their input and output. This capability allows the system to reduce the speed of fans or the number of pumps used based on the difference between the desired and measured temperatures in the target space.
If you would like more advice on how to maintain your cooling towers and chillers, check out this cooling tower maintenance checklist.
Manage and Conserve Water Resources with Wint
Cooling towers and chillers are essential parts of a large-scale HVAC system, each with its unique role, mechanisms, demands, and benefits. While cooling towers are critical for large-scale heat waste management in power plants and specific industrial applications, chillers are smaller, more modular, and more flexible cooling systems, primarily for commercial needs.
Regardless of the type of cooling tower or chiller you choose to employ in your project, some essential considerations are scalability, flexibility, maintenance, water consumption and conservation, and the specifications of your project’s individual properties.
When it comes to eliminating water waste and preventing leaks in large-scale water systems such as HVAC systems, Wint Water Intelligence in-line Water Management platform, powered by innovative AI and IoT technologies, is a turnkey solution. It enables property owners and operation managers to drastically lower water waste (and its related costs) by monitoring water distribution systems, automatically stopping leaks at the source. Plus, it can analyze water consumption to optimize usage, helping you reduce carbon, align with sustainability efforts, and improve your ESG score.
