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Cooling TowersThis act sheet is aimed at the enterprises that use evaporative

cooling towers, which ranges rom commercial operators

(e.g. shopping centres, hotels, oce towers) with large air

conditioning systems to industrial sites (e.g. power generation,

mining, petrochemical, ood and beverage, metal products .)

with air conditioning, rerigeration and/or cooling requirements.

General types o cooling towersEvaporative cooling systems are dened by their air fow

patterns. Air fow through evaporative cooling towers can

be natural drat, an assisted natural drat, mechanical

drat (induced drat) or mechanical drat (orced drat).

Natural drat cooling towers are generally only used or the

rejection o very large quantities o heat (e.g. power stations).

Smaller industrial cooling towers tend to be either o the

mechanical drat types. The air to water fow in evaporative

cooling towers can either be cross fow (air fow is directed

perpendicular to the water fow) or counter fow (air fow is

directly opposite to the water fow).

Water lossesWater is lost rom a cooling tower system through several

ways including evaporation (60-90%), leaks, overfow o the

cooling tower sump, drit (or windage) and bleed (10-

30%), which is the intentional draining o a certain amount o

water in order to decrease the build-up o salts in the system.

The eciency o cooling towers is aected by the chemical

treatment regime, quality o the incoming water and the

ambient air conditions. One o the measures o eciency is

the Cycles o Concentration (CoC) at which the unit operates,

which is a term used to indicate the number o times the

solids in a particular volume o water are concentrated. The

CoC can be calculated by dividing the concentration o total

dissolved solids (TDS) in the bleed water by the concentration

o TDS in the make-up water. Sometimes electrical

conductivity (EC) or chloride concentration is used to calculate

CoC. In Melbourne, cooling towers operate at 10 or more

CoC, as the quality o make-up water is very good (e.g. TDS ~

50 mg/L). In other areas, where the TDS o the make-up water

is higher the CoC will be lower.

Water saving optionsA number o water saving opportunities may exist within your

business and the benet o each option will vary depending

on your operation.

Some common water saving options or cooling towers are

summarised in the ollowing table, though note, other morespecic opportunities may still exist at your site or you to

investigate. Savings and cost estimates are indicative only. Specic

estimates based on your operations should be made beore

implementing an option. See the Ai Group website or other act

sheets on cooling towers and generating a water saving culture.

Water saving beneftsThere are signicant benets that can be realised through

becoming more water ecient. These include reductions in:

n Costs water, wastewater discharge and wastewater

treatment, maintenance. Remember, the cost o water is notjust the cost o purchase, but includes, handling, heating,

holding, treating and discharging oten a 20-30 X multiplier.

n Energy consumption - energy and water costs are very

oten linked, e.g. reducing hot water or cleaning saves

heating costs as well.

n Wastes wastewater treatment oten results in the generation

o prescribed wastes, which are costly to dispose o.

n Carbon ootprint drops when energy use is prevented or

saved and may soon be worth $20 per tonne CO2e or more.

Other benets include (do a sel test to see how much these

are worth to you):

n Increased productivity

n Improved public image

n Increased sta morale/engagement

n Improved Occupational Health and Saety.

Things to consider whenimplementing water saving optionsAs always, beore implementing a water saving option the

potential downsides should be considered. These may include:

Water saving factsheet:Cooling towers

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Water savings options cooling tower= 10% total water saving

$ = up to 10k, $$ = 10k - 100k, $$$ = > 100k

Option Cost Option Description Water Saving Hierarchy Category

0 - $Increase the set point at which the cooling towerbleeds water (the cycles o concentration) dependingon incoming salt concentration

Reduce

$

Monitor cycles o concentration to determine i leaks/overfows are occurring and eliminate. Look or: Incorrectly positioned ball foats Faulty operational controls Excessive return water overfowing the sump

Reduce

$Control the bleed rom towers using aconductivity meter

Reduce

$Replace inecient drit eliminators with most ecientmodels (0.002% loss)

Reduce

$ - $$

Reduce the cooling load (e.g. increase the air

conditioning temperature set-point) Reduce

$ - $$ Automate the dosing o chemicals to optimise Reduce

$ - $$Install a water sotener on the cooling tower make-up water to enable the cycles o concentration tobe increased

Reduce

$ - $$Install a side-stream ltration unit i suspended solidslevels are high (e.g. dusty areas)

Reduce

$ - $$Reuse bleed water in other plant operations wherepractical (e.g. toilets, irrigation).

Re-use

$ - $$Re-use cooling tower dump water or low quality enduses (e.g. toilet fushing, cleaning, irrigation)

Re-use

$ - $$ Re-use side-stream backwash water or low qualityend uses (e.g. toilet fushing, cleaning, irrigation)

Re-use

$$Treat bleed water using Reverse Osmosis and reuse asmake-up water

Recycle

$$$Examine use o recycled water rom adjacent acilitiesi available.

Recycle

$$ - $$$Replace wet cooling towers with a hybrid unit(combined air and evaporative cooler)

Reduce

$$ - $$$ Use air-cooling rather than evaporative cooling Avoid

$$ - $$$Check that towers are appropriately sized and replaceinecient, oversized units with multiple smaller units

Reduce

Source: Water eciency and water saving actsheets or Industry, PB, 2008

Water saving factsheet: Cooling towers

n Increased energy consumption:

For example, replacing an evaporative (wet) cooling

system with an air cooled (dry) system can sometimes

increase the acility energy consumption.

n Increased wastewater (trade waste) contaminant concentrations:

Overall quantity by mass (e.g. kg/day) may not increase,

but concentration might.

Talk to your water corporation to determine whether

increasing concentrations are a saety issue in the sewer

or whether a treatment option may become available as a

result e.g. a higher BOD may mean an opportunity or the

generation o biogas and secondary generation o electricity.

n Increased maintenance requirements may occur, depending

on the project.

Please contact Ai Group or your local water corporation when

considering water saving options.

AIG7082_COOLING

Further inormationContact Ai Groups Energy and Sustainable Business Helpdesk on 1300 733 752 or at sustainablebusiness@aigroup.asn.au or visit

the Ai Group website at www.aigroup.com.au.