KCF Technologies Blog

Maximize Cooling Tower Energy Efficiency Through Scrupulous Maintenance

A cooling tower fan at an university HVAC plant.
"Bringing Knowledge to People...Promoting Efficient Use of Energy" is the mantra of Energy Manager Training, a website mandated by India's Energy Conservation Act of 2002, which is financed jointly by the government of India and by the Federal Ministry of Economic Cooperation and Development of the government of Germany.  Among its pragmatic offerings is an unattributed three-page technical brief with some helpful "Cooling Tower Tips," presented in .pdf format.

"Reducing energy expenditures for your cooling tower may be as simple as regular maintenance.  This Technical Brief explains how proper maintenance will optimize heat transfer and help your equipment operate more efficiently.  It also identifies strategies for upgrading cooling tower performance."

Whether it's relatively small rooftop unit air conditioning a university, office building, or hotel, or one of the massive hyperboloid structures we associate with nuclear power plants, and large chemical complexes, cooling towers work by venting unwanted, or waste, heat that is carried by the cooling water into the atmosphere.

But maintenance matters, and costs of neglecting it can be steep:

"An improperly maintained cooling tower will produce warmer cooling water, resulting in a condenser temperature 5° to 10° F higher than a properly maintained cooling tower.  This reduces the efficiency of the chiller, wastes energy, and increases cost.  The chiller will consume 2.5 percent to 3.5 percent more energy for each degree increase in condenser temperature.  For example, if your chiller uses $20,000 of electricity each year, it will cost you an additional $500 to $700 per year for every degree increase increase in condenser temperature.  Thus, for a 5° to 10° F increase, you can expect to pay $2,500 to $7,000 a year in additional electricity costs.  In addition, a poorly maintained cooling tower will have a shorter operating life, is more likely to need costly repairs, and is less reliable."

Optimizing the performance of any cooling tower means keeping in check the process and problems that can plague them.  "The performance of a cooling tower degrades when the efficiency of the heat transfer process declines.  Some of the common causes of this degradation include:
  • Scale Deposites
  • Clogged Spray Nozzles
  • Poor Air Flow
  • Poor Pump Performance"
Poor air flow and poor pump performance often are readily detectable by excessive or uncharacteristic vibration.

All of these sources of degradation stem from unwanted elements in the water itself.  Thus the keys to maximizing energy efficiency in a cooling tower rely on:
  • Prevention of Corrosion (due to dissolved oxygen and/or acidic pH)
  • Prevention of Scale (due to dissolved minerals that precipitate out in evaporation)
  • Prevention of Fouling (due to dust, dirt, algae, fungi, and bacteria)
The brief recommends controlling and preventing all three through the use of Treatment Dosing Equipment: "In order for the treatment products to to work effectively, they must be properly fed into the cooling system.  Corrosion and scale inhibitors should be maintained at a constant level at all times, whereas biocides are most effective when applied in slug doses on a product alternated basis."

The good news is that even many neglected cooling towers can be returned to efficient operation with the right treatment: "It only takes three to six months to dissolve two tons of solid impurities from the coiler in a cooling tower after the installation of the chemical-free Aqua Correct physical water treatment.  The approximate two tons [of] deposits was the amount...removed from the cooling towers at the worldwide known dairy company MD Foods/ARLA as well as at the Danpo Chicken Slaughterhouse and in hundreds of other cooling tower plants."

Photo by Dr. Jeremy Frank/KCF Technologies.  All rights reserved.

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