EVAPORATIVE COOLING FOR LAB DESIGN - I2SL

EVAPORATIVE COOLING FOR LAB DESIGN:Balancing the Use of Energy and Water

Megan Gunther, PE, LEED AP BD+C, WELL APBuilding Performance Consultant

Affiliated Engineers, Inc.

LEARNING OBJECTIVES

• Develop an understanding of evaporative cooling and where it is best applied

• Realize the impact evaporative cooling can have on cooling load reduction

• Gain an understanding of the energy:waternexus and how to balance energy and water for cooling

• Learn how to use tools to predict energy savings and water consumption associated with these systems

What is evaporative cooling?

310/23/2019 I2SL 2019: Evaporative Cooling for Lab Design

What is evaporative cooling?

11/4/2019 4

e•vap•o•ra•tive cool•ingnounreduction in temperature resulting from the evaporation of a liquid, which removes latent heat from the surface from which evaporation takes place

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 5

• Graphical representation of the thermodynamic parameters of air•Dry-bulb temperature•Wet-bulb temperature•Dew point temperature• Relative humidity•Humidity ratio• Enthalpy

A quick introduction to psychrometric charts…

6

Let’s focus on…

Dry Bulb (°F)

Wet Bulb (°F)

Enthalpy (heat or energy of the air)


Cooling Coil Load 101

7

1. OA91, 66

2. CC52, 52

1. OA Enthalpy30.65 Btu/lb da

2. SA Enthalpy21.4 Btu/lb da

San Jose, CA

Design Day Example

1. Hot outside air enters the coil

Chilled water in coil absorbs heat

2. Cool air leaves the coil


Cooling Coil Load 101

8

1. OA91, 66

2. CC52, 52

2. SA Enthalpy21.4 Btu/lb da

1. OA Enthalpy30.65 Btu/lb da

San Jose, CA

Design Day Example

Airflow(CFM) x Heat Removed =

Cooling Load (tons)

Heat removed from air


9

Back to evaporative cooling.


10

Stage 1: Indirect Evaporative Cooling

1. OA91, 66

“Indirect” as no water is added to air stream

Wet surface heat exchanger

2. IEC75, 61


11

Stage 2: Direct Evaporative Cooling

“Direct” as water is added to air stream

Cools and humidifies the air

1. OA91, 66

2. IEC75, 61

3. DEC63, 61


12

Stage 3: Supplemental Cooling Coil (when necessary)

4. CC52, 52

When air now enters the cooling coil it is significantly reduced in temperature

1. OA91, 66

2. IEC75, 61

3. DEC63, 61


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Now let’s look at what that means for cooling load.


14

IDEC reduces the heat the cooling coil needs to remove

4. CC52, 52

Without IDEC, cooling coil load is sized to bring 91°F air down to 52°F

1. OA91, 66

2. IEC75, 61

3. DEC63, 61

With IDEC, cooling coil load is sized to bring

63°F air down to 52°F

Heat removed from air without IDEC

Heat removed from air with IDEC


Benefits of evaporative cooling

• Significantly reduces (and at some hours eliminates) annual chiller energy

• Trade-off for chiller energy reduction is slight increase in fan energy• Supply fan• Scavenger fan

• Reduction in overall building energy consumption


16

Evaporative works well

Evaporative may work

Evaporative not recommended


Energy:Water Nexus

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18

Evaporative works well


19

Also drought prone



The Folsom Dam between 2010 and 2014

Cost of water & sewer are rising

21

Recent national

surveys show

average

increases in

water/sewer rates

in the US range

between 7% and

9% per annum


Water for energy…


23

Coal

36 gal/kWh1

Nuclear

44 gal/kWh1

Natural Gas

35 gal/kWh1

Hydroelectric

65 gal/kWh2

Volumes represent high end of consumption1Source: Macknick et al. 20112Source: UNESCO-IHE 2011

4.64 gallons of water consumed for every kWh of electricity consumed in California


Energy for water…


Case Study 1

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New Construction Lab Building

• Location: South San Francisco, CA

• Building size: 93,000 ft2

• Baseline HVAC system: VAV reheat with water-cooled chillers

• 40% Lab, 60% Office


Proposed Design

• Indirect evaporative cooling only

• Air-cooled chillers due to reduced chiller plant size (under 300 tons)


Evaluating Energy

28

Baseline: VAV reheat with water-cooled chillers

Proposed: VAV reheat with indirect evaporative cooling and air-cooled chillers

Baseline Proposed (IEC) Savings

Installed Chiller Capacity: 320 tons 240 tons 25%

Chiller Operating Hrs. 3,218 hrs/yr 2,343 hrs/yr 28%

Chiller + Fan Energy 134,000 kWh/yr 127,000 kWh/yr 5%

Equipment Capital Cost $ 4,330,000 $ 3,532,000 18.5%


Evaluating Water

29

Baseline: VAV reheat with water-cooled chillers

Proposed: VAV reheat with indirect evaporative cooling and air-cooled chillers

Baseline Proposed (IEC) Savings

Site Water Consumption 2,220,300 gallons 1,422,200 gallons 36%

Chiller + Fan Energy 134,000 kWh/yr 127,000 kWh/yr 5%

Source Water Consumption 621,760 gallons 589,280 gallons 6%

Total Water Consumption 2,842,060 gallons 2,011,480 gallons 30%


Energy & Water

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0

20000

40000

60000

80000

100000

120000

140000

160000

Baseline Proposed

Ener

gy (

kWh

)

Energy Consumption

Chiller Energy Supply Fan Energy Scavenger Fan Energy

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

Baseline Proposed

Wat

er (

gallo

ns)

Water Consumption

Site Water Source Water


Case Study 2

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Lab Retrofit in Existing Building

• Location: San Jose, CA

• Program size: 20,000 ft2 (within 50,000 ft2

total building area)

• Baseline HVAC system: VAV reheat with water-cooled chillers

• 100% laboratory


Project Scope

• Retrofit existing office space into BSL2 laboratories

• New air handling system

• Existing chilled water plant (water-cooled chillers & cooling towers)


0

40

80

120

160

200

240

280

320

360

Existing Built Out New Lab Fit Out

Co

olin

g Lo

ad (

Ton

s)Increased Cooling Demand

Chiller Plant Capacity

New lab fit out cooling demand is 140 tons

compared to the existing office fit out cooling demand

of 70 tons.

Building demand exceeds existing chiller plant capacity.


Cooling Demand Reductions with Evaporative

35

3. CC52, 52

1. OA91, 66

2. IEC75, 61

Without IDEC, cooling coil load is sized to bring 91°F air down to 52°F

With IDEC, cooling coil load is sized to bring

75°F air down to 52°F


Building Cooling Demand

36

0

40

80

120

160

200

240

280

320

360

Existing Built Out New Lab Fit Out With Evaporative Cooling

Co

olin

g Lo

ad (

Ton

s)

Chiller Plant Capacity

Evaporative cooling reduced the cooling load on the

chiller plant from 140 tons to 105 tons.

25% cooling load reduction for new lab fit out.


Conclusions

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Conclusions

• Evaporative cooling works well in dry climate types

• While it may seem to be water intensive, evaporative cooling may actually save water

• It is important to balance energy and water savings, remembering to account holistically for site and source energy and water consumption

• Evaporative cooling can potentially decrease your peak chiller demand by 25%

• Indirect evaporative cooling coupled with air-cooled chillers can offer benefits over conventional VAV with water-cooled chillers & cooling towers in the right climate

• For retrofit projects, evaporative cooling may eliminate the need to install additional chiller capacity to support increased cooling demand


Q & AThank you.

Megan Gunther, PE, LEED AP BD+C, WELL APBuilding Performance Consultant

Affiliated Engineers, Inc.

Documents

EVAPORATIVE COOLING FOR LAB DESIGN - I2SL