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

Megan Gunther, PE, LEED AP BD+C, WELL AP Building Performance Consultant Affiliated Engineers, Inc. • Develop an understanding of evaporative cooling and where it is best applied • Realize the impact evaporative cooling can have LEARNING OBJECTIVES on cooling load reduction • Gain an understanding of the energy:water nexus 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?

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 3 What is evaporative cooling?

11/4/2019 4 e•vap•o•ra•tive cool•ing noun reduction 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 A quick introduction to psychrometric charts… • Graphical representation of the thermodynamic parameters of air • Dry-bulb temperature • Wet-bulb temperature • Dew point temperature • Relative humidity • Humidity ratio • Enthalpy

Let’s focus on… Dry Bulb (°F) Wet Bulb (°F) Enthalpy (heat or energy of the air)

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 6 Cooling Coil Load 101 San Jose, CA Design Day Example

1. OA Enthalpy 30.65 Btu/lb da

2. SA Enthalpy 1. OA 1. Hot outside air enters the coil 21.4 Btu/lb da 91, 66 Chilled water in coil absorbs heat 2. CC 2. Cool air leaves the coil 52, 52

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 7 Cooling Coil Load 101 San Jose, CA Design Day Example

Heat removed from air 1. OA Enthalpy 30.65 Btu/lb da

2. SA Enthalpy 1. OA 21.4 Btu/lb da 91, 66

2. CC Airflow(CFM) x Heat Removed = 52, 52 Cooling Load (tons)

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 8 Back to evaporative cooling.

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 9 Stage 1: Indirect Evaporative Cooling

1. OA 91, 66 “Indirect” as no water is added to 2. IEC air stream 75, 61 Wet surface heat exchanger

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 10 Stage 2: Direct Evaporative Cooling

3. DEC 63, 61 1. OA 91, 66 “Direct” as water is added to air 2. IEC stream 75, 61 Cools and humidifies the air

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 11 Stage 3: Supplemental Cooling Coil (when necessary)

3. DEC 63, 61 1. OA 91, 66 When air now enters the cooling 2. IEC coil it is significantly reduced in 4. CC 75, 61 temperature 52, 52

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 12 Now let’s look at what that means for cooling load.

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 13 IDEC reduces the heat the cooling coil needs to remove

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

Heat removed from air without IDEC

With IDEC, cooling coil load is sized to bring 3. DEC 63°F air down to 52°F 63, 61 1. OA Heat removed 91, 66 from air with IDEC 2. IEC 4. CC 75, 61 52, 52

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 14 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

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 15 Evaporative works well

Evaporative not recommended Evaporative may work

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 16 Energy:Water Nexus

11/4/2019 17 Evaporative works well

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 18 Also drought prone

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 19 The Folsom Dam between 2010 and 2014

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 20 Cost of water & sewer are rising

Recent national surveys show average increases in water/sewer rates in the US range between 7% and 9% per annum

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 21 Water for energy…

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 22 Natural Gas Coal Nuclear Hydroelectric 35 gal/kWh1 36 gal/kWh1 44 gal/kWh1 65 gal/kWh2

4.64 gallons of water consumed for every kWh of electricity Volumes represent high end of consumption 1Source: Macknick et al. 2011 consumed in California 2Source: UNESCO-IHE 2011

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 23 Energy for water…

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 24 Case Study 1

11/4/2019 25 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

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 26 Proposed Design • Indirect evaporative cooling only • Air-cooled chillers due to reduced chiller plant size (under 300 tons)

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 27 Evaluating Energy

Baseline: VAV reheat Proposed: VAV reheat with water-cooled chillers 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%

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 28 Evaluating Water

Baseline: VAV reheat Proposed: VAV reheat with water-cooled chillers 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%

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 29 Energy & Water

Energy Consumption Water Consumption 160000 3,000,000 140000 2,500,000 120000 100000 2,000,000 80000 1,500,000

60000 Water (gallons) Water Energy (kWh) Energy 1,000,000 40000

20000 500,000 0 Baseline Proposed 0 Baseline Proposed Chiller Energy Supply Fan Energy Scavenger Fan Energy Site Water Source Water

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 30 Case Study 2

11/4/2019 31 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

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 32 Project Scope • Retrofit existing office space into BSL2 laboratories • New air handling system • Existing chilled water plant (water-cooled chillers & cooling towers)

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 33 Increased Cooling Demand

360

320 Chiller Plant Capacity

280

240 New lab fit out cooling demand is 140 tons 200 compared to the existing office fit out cooling demand 160 of 70 tons. 120

Building demand exceeds Cooling Load Cooling (Tons) 80 existing chiller plant capacity.

40

0 Existing Built Out New Lab Fit Out

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 34 Cooling Demand Reductions with Evaporative

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

1. OA 91, 66

With IDEC, cooling coil 2. IEC load is sized to bring 3. CC 75, 61 75°F air down to 52°F 52, 52

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 35 Building Cooling Demand

360

320 Chiller Plant Capacity 280

240 Evaporative cooling reduced the cooling load on the 200 chiller plant from 140 tons to 105 tons. 160 25% cooling load reduction

120 for new lab fit out. Cooling Load Cooling (Tons) 80

40

0 Existing Built Out New Lab Fit Out With Evaporative Cooling

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 36 Conclusions

11/4/2019 37 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

10/23/2019 I2SL 2019: Evaporative Cooling for Lab Design 38 Q & A

Megan Gunther, PE, LEED AP BD+C, WELL AP Thank you. Building Performance Consultant Affiliated Engineers, Inc.