A cooling tower is a heat rejection device in HVAC, which removes unwanted heat from a water cooled chiller. This is done by bringing air and water into direct contact with each other to reduce the water’s temperature thereby cooling water streams. The cooled water is then returned to the building's chiller to continue the cycle to cool and dehumidify the indoor air.
Understanding the Inputs:
Cooling Tower Volume per area (gal/ft²/yr): The amount of water being recirculated. The Nation Average for Buildings with cooling towers use 7 gallons of water more (per sf annually) than those without and is thus setup as an automated input which a user can modify.
Potable Water Cooling: Does the cooling tower use portable water?
Cooling Tower Efficiency: Were strategies taken to conserve cooling tower water (<25%)? Examples of strategies for conserving cooling tower water include: using alternative sources of water, optimizing the cycles of concentration and minimizing bleed volume, minimizing drift, and preventing overflows and leaks.
Other Inputs used for Cooling Tower
Percent of the building cooled by a water-cooled chiller
Calculation Method and Results
The Cooling Tower Water Use calculation method follows AIA's COTE TopTen Toolkit: Measure 4 - Design for Water tool, section 3 - Cooling Tower.
1. Are Cooling Towers Energy Efficient?
> Yes, cooling towers are commonly used to provide significantly lower water temperatures than achievable with "air cooled" or "dry" heat rejection devices, thereby achieving more cost-effective and energy efficient operation of systems in need of cooling.
2. What are Cooling Tower Cycles? Does cove.tool calculate cycles?
>Cycles of Concentration (also known as Cycles or Concentration Ratio) is a measure of the concentration of dissolved solids in processed water. Cove.tool does not calculate cycles of concentration for cooling towers, only water use. As a cooling tower removes heat by evaporating water, leftover contaminants begin to build up in concentrations making the system less efficient. To prevent buildup of deposits, cooling towers require a portion of the water to be removed in a process called blowdown. Makeup water is then added to replace evaporative losses and blowdown volume. Cooling towers can therefore account for large portions of a building’s total water use.