Green Your Cooling Tower — Reduce HVAC Water Consumption

Whether you’re seeking an official Green Building Certification or simply want to reduce your impact on the environment, water conservation is probably part of your plan. Normally when we think of water conservation, we look to plumbing – low flow toilets, automatic shut-off faucets, irrigation and so on. I recently read an interesting article that addresses water usage in HVAC, specifically in cooling towers. Here are some of the highlights:

From The HVAC Factor: Reducing Water Consumption. Changes to cooling tower operation and maintenance are one way to conserve this resource, written by Neil Maldeis and originally published in the April 2012 issue of Today’s Facility Manager.

“Heating and air conditioning systems are traditionally designed as “closed” systems that consume little or no water in normal operations. In large commercial HVAC installations that are properly operated and maintained, water for cooling towers accounts for almost all of the HVAC system’s water consumption.

Cooling towers need to make up water that is lost in three ways: by evaporation; from intentional bleed off (required to remove suspended and dissolved solids left behind when pure water evaporates); and from drift, water that escapes the system in the form of mist or droplets carried by the airflow.

Strategies for improving cooling tower performance and reducing water consumption include:

  • Use existing building automation system technology to control tower operations, including automatically shutting the tower down when possible without impacting occupant comfort.
  • Monitor water levels in the cooling tower reservoir to prevent overflow. Check fill valve settings and operation, and replace old float style fill valves with more efficient parts. Install an overflow alarm to alert the operator in case of sump overflow.
  • Install drift eliminators to redirect airflow and reduce water loss.
  • Recognize that evaporation rate is directly tied to cooling load, with evaporation loss of about three gallons per minute per 100 tons of cooling. Finding ways to reduce cooling load will reduce both energy and water consumption.

    Use These Tips to Conserve Water While You Keep Cool This Summer
  • Use turbidity sensors, chemical monitors, automatic bleed systems, side stream filtration, and other methods to maintain ideal water quality levels in towers. Consider alternative make-up water sources such as wastewater from industrial processes.
  • Evaluate potential of hybrid cooling towers, dry coolers, heat sinks, and other less water intensive methods to replace or supplement current cooling towers as part of a broader upgrade.
  • Engage an energy engineer, energy services company, or other third-party advisor to conduct a critical system audit that includes the cooling tower and other HVAC system elements.”

For full article, click here.

If you’re a Facility Manager or Building Owner, Today’s Facility Manager is a great resource for information. Whatever method of interaction you choose – tweet, blog, newsletter – they are chock full of pertinent info relating to what you do and see every day. And no, I am not being compensated for my suggestion. I just really like their stuff!