As energy and water costs continue to rise, improving the efficiency of cooling tower operations has become a significant priority across industries. More efficient cooling towers reduce energy consumption through optimized heat transfer and can also conserve water through effective cycles of concentration and blowdown control. Even minor improvements in cooling tower performance can yield substantial cost savings and environmental benefits.
This article covers the fundamentals of cooling tower efficiency.
At its core, an efficient cooling tower maximizes heat rejection while minimizing water consumption. The key metrics used to gauge cooling tower efficiency focus on these areas:
This measures how much heat is dissipated by the cooling tower over a given timeframe, usually expressed in BTUs/hr or kW. Effective heat transfer depends on factors like airflow rate and the temperature differential between inlet and outlet water.
This refers to the accumulation of dissolved solids in the circulating water. Higher cycles translate to less bleed-off and make-up water required. Most cooling towers operate between two and four cycles of concentration.
By directly measuring makeup water consumption, operators can calculate cooling tower water usage on a gallons per minute (gpm) or gallons per hour (gph) basis. Lower water usage indicates higher efficiency.
This metric looks at the percentage of circulating water bled off to control cycles of concentration. Minimizing blowdown saves water and the energy needed to condition replacement water.
Tracking metrics like these over time is crucial for evaluating equipment upgrades, operational changes, and water treatment improvements that aim to enhance efficiency. Even small optimizations add up substantially for heavy-duty cooling tower applications across industries.
Properly monitoring and controlling what goes into and comes out of a cooling tower is central to efficient operation. The key inputs and outputs include:
Online instrumentation and data logging equipment make it easier than ever to monitor these parameters in real-time. Tracking output changes in response to input adjustments provides visibility on overall efficiency and opportunities for improvement.
Cycles of concentration is a critical metric for evaluating and optimizing cooling tower efficiency. This term refers to the accumulation of dissolved minerals and total dissolved solids (TDS) in the recirculating water.
As pure water evaporates out of a cooling tower, it leaves behind any contaminants that entered through the makeup water source. Over time this increases the concentration of TDS as compared to the new makeup water entering the system.
To help understand this concept, EAI&#;s Ryan Vargas shares a simple analogy: &#;As the water evaporates inside of a cooling tower, dissolved solids suspended inside the water get more and more concentrated. To oversimplify, it&#;s like making a bowl of ramen instant noodles. Have you ever put the spice packet into the water and when it starts to boil, forget about it? You come back when you smell something funny, all of your water is boiled off and the salt and spices are concentrated at the bottom.&#;
Cycles measure this increase&#;if the cooling water has a TDS level three times higher than the incoming makeup water, it is operating at three cycles of concentration. The higher the cycles, the less blowdown is required to purge contaminants. This conserves water and the energy needed to condition it.
In addition, elevated mineral concentration also raises the risk of scale formation on heat transfer surfaces. There is a practical limit around seven cycles for most towers, especially in the West and Southwest, after which scaling and deposition rapidly reduce efficiency.
Optimizing cycles of concentration requires balancing water savings against heat transfer impacts:
The cycles value that maximizes water conservation without excessive scaling varies. But understanding and controlling concentration is pivotal for getting the most out of a cooling tower system.
While advanced technology upgrades can improve efficiency, most towers benefit greatly from simpler operational measures first. Consistent cooling tower water treatment, monitoring, maintenance, and training helps optimize existing performance with little or no capital expenditure.
Key best practices include:
&#;I recommend checking the system once per week for facilities that have some type of a controller that is either wired into the system or is able to report out. The latter will alert your vendor if a measurement is abnormal,&#; says Vargas.
Many facilities find that consistency with basic operational diligence not only optimizes efficiency, it also reduces the risk of unplanned downtime events that can severely disrupt production. The fundamentals may not be glamorous, but excellent tower performance depends on their reliable execution.
Once sound operational practices are established, facilities seeking to stretch their cooling tower performance may consider advanced technologies and upgrades including:
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The feasibility and return on investment of advanced upgrades will vary for each facility. But where cost-effective, these measures can compound operational gains to reduce cooling tower overhead costs. Performance incentives and local regulations may also subsidize certain upgrades. For most operators, efficiency is a long game with no finish line.
While the core function of cooling towers remains the same across applications, factors like load size, environment, and downtime risk create differences in cooling tower design between industrial facilities and commercial buildings.
Industrial sites like oil refineries, petrochemical plants, and power plants often utilize very large, field-erected cooling towers. Their high heat loads and continuous uptime requirements call for robust construction with redundant fans and pumps. Materials also vary per the process environment&#;a refinery cooling tower handles hydrocarbons, while a nuclear plant contends with radioactive water.
Commercial cooling towers for offices, hospitals, and district energy systems tend to be smaller prefabricated units mounted on rooftops or along HVAC equipment. Their intermittent operation allows for simpler systems, often with a single fan. Cost and footprint are bigger considerations. Additionally, commercial towers must account for winter shutdowns and legionella control given their integration with human-occupied buildings.
While tower specifics differ across sites, employing efficiency best practices and advanced technologies can benefit both industrial and commercial operators. The potential savings make optimization worth pursuing, even for smaller commercial towers. Efficiency gains at scale translate to even more dramatic reductions for high-capacity industrial towers.
The reality is that most facilities leave substantial efficiency improvements on the table with their existing cooling tower assets. By monitoring key parameters and proactively adjusting operations and upkeep, operators can extend the life of cooling equipment, curb overhead costs, and reduce environmental impacts. The incentives are stacked for those who prioritize efficiency across their thermal management systems.
With this foundation on maximizing cooling tower performance, commercial buildings and industrial sites alike have actionable best practices to start driving efficiency gains today. Consistent incremental improvements over months and years ultimately accumulate to optimize these critical assets for the long run. If you need help improving the efficiency of your cooling towers, contact us today for a free on-site analysis.
Looking for ways to optimize cooling towers? Manufacturing companies spend billions of dollars each year for the fuel and electricity that keep their facilities running. Energy saving products, designs and systems are more widely available than ever before. However, with Heating, Ventilation and Air Conditioning (HVAC) consuming the largest amount of a plant&#;s energy bill, efficiency efforts are best focused in that area. One such subset is in cooling towers, essential to control suspended solids and algae growth.
Cooling towers cool water through heat transfer and evaporation. With a loss of 1% water for every 10 degrees of cooling required, the evaporation factor can be very significant. When evaporation occurs, scale is left behind that can interfere with cooling tower efficiency and require expensive maintenance or acid cleaning.
Industrial plants typically contain equipment which requires both open evaporative and closed cooling water systems, making well-maintained cooling tower chemistry essential to plant reliability and efficiency. As we get into the warmer months of the year, the ambient heat of the summer months will detract from the cooling capacities of these towers if they are not kept in good shape.
This makes them &#;fatigued&#;, putting a strain on system equipment and the water it provides devices such as heat exchangers, production machinery and HVAC systems will be less able to draw off heat. In industries where a cooling tower supports critical processing machinery, HVAC system or even refrigerators and freezers, even a small dip in cooling power can cause extensive downtime or even product losses.
Over time, the leaving-water temperature of a neglected cooling tower will rise. For every 2-degree F increase, the equipment&#;s energy costs will also increase&#;by up to 6%. However, simple maintenance techniques can optimize cooling towers and save facilities up to 15% on its electricity costs. Routine preventive maintenance also can help conserve water, extend the operating life of your cooling equipment, and keep energy and equipment costs low.
The purpose of the fill, also called wet deck or surface, is to maximize the contact between the air and the water, encouraging evaporation. Fill is covered in a textured pattern, usually ridges or wrinkles, so that when pieces of the fill are placed together, they leave open spaces for water and air to travel.
This fill should be serviced or replaced in cooling towers to avoid fouling that will prevent sufficient air volume necessary for the system&#;s water to dissipate heat efficiently. Fouling can also make the fan and motors work harder, adding significantly to energy costs.
When choosing a HVAC or industrial cooling tower, keep in mind that cooling efficiency is affected when aggressive chemical maintenance solutions are limited due to the risk of harm and damage to metal surfaces. This makes them less efficient and susceptible to maintenance and unscheduled shutdowns. Further, having to limit potent chemicals used to remove biological growth from water can produce fouling build-up inside the cooling tower which affects cooling efficiency.
Because plastic cooling towers are impervious to residual salts, the tower cannot be damaged and fill material can be cleaned up by most aggressive de-scalers which goes a long way toward efficiency and avoiding unexpected replacement expenses.
Daily, weekly and monthly system monitoring will keep energy usage and costs down while ensuring cooling system are working at their optimal level. Frequent visual inspection of your cooling system&#;s fans, motors, belts and pumps is an effective way to ensure that your systems are running at their highest efficiencies. Loose belts or improperly working fans will prevent smooth flow through the system and result in reduced efficiencies and higher operational costs.
If water temperatures increase even a small amount, the return water from the towers to the chillers will cause the chiller to work harder, resulting in increased costs and a reduced cooling effectiveness. Regular inspection of basins, drains and nozzles will also prevent the buildup of minerals, debris and dirt that will clog the system, increasing energy consumption and reducing overall system efficiency.
Inefficient chilled water plant controls are often associated with poor cooling tower performance and investments here can greatly improve overall HVAC efficiency. Some solutions, like tekWorx Xpress® , can act as an early warning system, sending emails or texts to staff when equipment such as a fan, pump or chiller is operating outside expected parameters.
tekWorx Xpress® algorithms optimize cooling towers by continuously adjusting cooling equipment operation and key setpoints based on such parameters as occupancy level and outdoor temperature to maximize the system efficiency in real&#;time. This is done while maintaining comfort cooling needs. Xpress® optimizes overall cooling system energy consumption via several of its patented algorithms, including:
To optimize cooling towers and associated plant equipment requires diligent maintenance, proper equipment selection and the right control strategy to permanently improve overall HVAC efficiency.
To optimize cooling towers and associated plant equipment requires diligent maintenance, proper equipment selection and the right control strategy to permanently improve overall HVAC efficiency.
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