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Water and 

Energy
Water Conserving Cooling

Status and Needs

Energy-Water Needs 

Western Region Workshop

Salt Lake City

January 10 – 11, 2006

John S. Maulbetsch

Maulbetsch Consulting
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We’re here to 

talk about....

Water-Energy trade-offs

• A big, multi-faceted problem

More people/more water/more energy

My intent

• Take a narrow slice and simplify it

Use less water to generate electricity
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Why is this 

easy?

We know where the water gets used

– Cooling: condense steam from the turbines

We know how we do it now

– Usually wet cooling towers

We have technologies that use less water

– Commercially available, proven technologies 

– Can reduce plant water use by 80 to 90+%
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So what’s the 

problem?

It almost always costs more

How much more depends on

• Type of plant

• Climate at plant site

• Cost of fuel

• Price for electricity (especially at peak times)
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The rest of the 

talk

Show you some cooling systems

Present some cost comparisons

Show some advancements that may help reduce 

cost
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Cooling systems

The old movie---once-through cooling

Common practice---wet cooling towers

Water conservers---dry cooling/air-cooled 

condensers
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Once-through

to HRSG

Cold CW

Hot CW

CW Pump(s)

Exhaust Steam

to HRSG

Cold CW

Hot CW

CW Pump(s)

Exhaust Steam

Water 

source—

ocean, river, 

lake, etc
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Wet cooling 

tower

Fans

Cooling Tower

Makeup Blowdown

Fans

Cooling Tower

Makeup Blowdown

Hot CW

Cold CW

Ambient air

from condenser

to condenser
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Wet cooling 

tower
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Air cooled 

condenser

Fans

to HRSG

Exhaust

steam

Air Cooled Condenser

Fans

to HRSG

Exhaust

steam

Air Cooled Condenser

Ambient air

from steam 

turbine

to boiler or HRSG

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Cooling system 

costs

Capital costs

Operating costs

• Cost of power for pumps and fans

• Cost of water

• Cost of maintenance

Penalty costs

• Effect on plant efficiency

• Cost of reduced output on hot days
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Trade-off/ 

optimization

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6 7 8 9 10

Size of Cooling System

Cost

Capital Costs Penalty Costs Total Costs
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Cost differentials

Increased capital cost---500 MW plants

0.4% to 12.5%

Increased cooling system power

0.5 to 3.0 MW 

Increased plant heat rates

0.4 to 4.0 % 

Increased power production costs

1.9 to 4.9%
Capital Cost---500 MW Steam Plant

280,000,000

290,000,000

300,000,000

310,000,000

320,000,000

330,000,000

340,000,000

350,000,000

Once-through Wet Dry

Cooling System Type

Captial Cost, $ 

Base +.43 %

+12.6 %
Hot Day Heat Rate Increase---500 MW Steam Plants

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

Once-through Wet Dry

Cooling System Type

Heat Rate Increase, %
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“Equivalent”

cost of water

$3.50 to $6.00 per 1,000 gallons

$1,000 to $2,000 per acre-foot
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Some things that 

might help....

 Use a little bit of water a little bit of the 

time

–Hybrid (wet/dry) systems 

–Spray enhancement

Recover some of the water from wet 

systems

Marley’s Air-to-Air® concept
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Hybrid wet/dry 

system
Tucuman 450 MW Combined Cycle (Argentina)

PAC SYSTEM®

(Air Cooled Condenser & Wet Cooling System)
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Spray 

enhancement

Spray water into inlet air stream of air-cooled 

condenser

Low capital cost approach

Low annual water use

Reduce inlet temperature by 5 to 10 F

Restore “hot day” capacity loss

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Marley Air-toAir®

Condensing 

Media

Ducting

Wet Fill

Cool 

Ambient Air

Cool 

Ambient Air

Hot 

Water

Condensing 

Media

Ducting

Wet Fill

Cool 

Ambient Air

Cool 

Ambient Air

Hot 

Water
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Possible retro-fit
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Finally....

Is the prize worth the price?

– Your call

– Very site specific

Is this a good way to do it?

– I state without proof

• About the same as reclaimed water use

• Cheaper (now at least) than “water-free”

renewables (wind or solar)