Introduction: How to Optimize Cooling Towers

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.

4 Areas to Investigate to Ensure Cooling Towers are Operating at Peak Efficiency

1. Monitor Cooling Tower Fill

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.

2. Cooling Tower Equipment Selection  

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.

3. Frequent Cooling Tower Inspection  

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.

4. Optimizing Cooling Tower Control 

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:

• Condenser Water Temperature Optimization: Determines the equipment operating parameters that will produce the optimal condenser water temperature that will minimize total power consumed by the chiller and cooling towers.  This algorithm balances auxiliary equipment power with chiller power to operate the chillers most efficiently based on ambient conditions and load.

• Adaptive Tower Sequence Optimization: This module will sequence cooling tower isolation valves (cells) on and off to flow water over the maximum amount of cooling towers without falling below the minimum flow rate of the associated tower cells.

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.