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.

Start at the Top

The most successful approach to creating an energy efficiency plan begins with a commitment from management. This typically starts with simple statement of what is to be achieved such as reducing carbon emissions or being strong environmental stewards. Once this essence is established and agreed upon, endorsement and internal publication of the energy policy begins. Endorsement by senior management, recognizing and praising energy-related achievements and consistent communications related to the energy motto are key for continued success.

Responsibility

Once an energy efficiency plan is in place, a leadership team should be appointed that represents a solid cross-section of the organization in terms of job function and geography. This team is responsible for both establishing reduction metrics and tracking measurable energy reduction goals such as percentage reductions or absolute reductions, water- and sewer-use savings or increased equipment production capacity and reliability.

Accountability

Energy efficiency plans need to be supported by data. The two basic types of energy-saving-initiative measurements are metered and calculated. In a perfect world, all energy savings would be metered. The cost of metering the exact savings can be cost prohibitive to implement. Conversely, calculated savings had an added complication of making adjustments for effects of year-to-year production activity, weather-related energy usage and/or other variables to be truly accurate.

One solution to this dilemma is an energy monitoring system. For example, tekWorx Xpress® monitors energy performance, equipment operation and associated energy costs daily, month and yearly and presents this data in an easy-to-read dashboard. Xpress® also offers real-time energy performance comparison and efficiency ranking, providing instant insight energy use a portfolio’s collective energy profile and how each site ranks relative to the efficiency of the others. 

HVAC systems are in charge of keeping temperatures comfortable, humidity consistent , and indoor air quality high. Often times, however, airside optimization is not considered in facility controls.

As much of the energy and cost that goes into powering HVAC is lost to waste, these three smart airside optimization strategies can help facilities can realize significant HVAC energy savings.

Airside Optimization and Air Filtration Systems

In order for HVAC system to operate correctly and deliver proper indoor air quality (IAQ), air filter maintenance and monitoring are essential. Most BAS systems monitor for air pressure drops outside of normal ranges. When this occurs, it often means that the air filter is clogged and/or installed improperly and should be changed. Dirty filters overwork HVAC systems by restricting air flow leading to poor indoor air quality, HVAC maintenance issues and increased repair costs.

Airside Optimization: Heating and Cooling Ducts

Commercial heating and cooling systems are connected to points throughout a facility by the ductwork. Consisting of a network of large pipes, this ductwork provides a pathway for conditioned air to travel from heating and cooling equipment to the insides of a commercial building.  Any problems in a facility’s duct system — broken seals, loose or missing sections, detached pipes, or damaged ducts — can cause substantial air leaks that will result in lost energy and wasted operating dollars. Duct sealing and careful inspection and appropriate repair of the ductwork will prevent these problems. Connections between sections of ductwork should be properly sealed with mastic, a specialized rubbery compound designed especially for ducts. Metal tape can also be used. Connections can also be mechanically fastened with sheet metal screws. Standard duct tape should be avoided because the adhesive can dry out and cause the tape to fall away.

Airside Optimization and AHU Monitoring

In commercial buildings, all air handlers are built and installed with an outside air intake and damper.  This outside air intake and damper has a large effect on both the energy use of a building and the indoor environmental quality (IEQ) of a building. By optimizing air handling units (AHUs), significant energy savings can be achieved.

Normally, air handlers cool or heat a mix of return air from the space it is conditioning and outside air that is required for proper IEQ. When the outside air dampers let in more outside air than required by the building code,  the air handler will use more energy than needed.  Conversely, dampers can let in too little air. This often happens when the outside dampers fail in a position where they are completely closed and do not allow any outside air into the air handler.  Advanced airside optimization solutions ensures these conditions are constantly being monitored.

Optimizing AHUs requires real-time monitoring of static pressure and supply air temperature setpoints. Sensors throughout the facility feed temperature and humidity data to a BAS or other control device and algorithms then determine optimal heating and cooling requirements, sending these efficiency setpoints back to the air handlers. Not only does this approach save energy dollars but helps ensure better occupant comfort.

tekWorx real-time airside optimization by continuously and automatically minimizing the power required for air distribution and delivery. These proven adaptive control techniques optimize air pressure, flow and temperature (system and zone) while maximizing economization mode and meeting desired space conditions.