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Does Evaporative Cooling Make Sense in an Arid Climate Does Evaporative Cooling Make Sense in an Arid Climate

Does Evaporative Cooling Make Sense in an Arid Climate - PowerPoint Presentation

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Does Evaporative Cooling Make Sense in an Arid Climate - PPT Presentation

WCEC Webinar Mark Modera November 17 2016 WCEC MISSION Accelerate the development and commercialization of efficient heating cooling and energy distribution solutions through stakeholder engagement innovation RampD ID: 661430

evaporative water cooling pre water evaporative pre cooling air energy cooler kwh gal condenser bleed save wet ventilation bulb

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Slide1

Does Evaporative Cooling Make Sense in an Arid Climate?WCEC Webinar

Mark ModeraNovember 17, 2016Slide2

WCEC MISSION“Accelerate the development and commercialization of efficient heating, cooling, and energy distribution solutions through stakeholder engagement, innovation, R&D, education, and outreach.”Slide3

WCEC Team Established April 2007Part of the Energy Efficiency Center at UC DavisMark Modera DirectorVinod Narayanan Associate DirectorTheresa Pistochini Engineering Manager

9 Full-time Engineers1 Behavioral Scientist1 Post-Doc7 Graduate Students

10 Undergrad Students2 Support Staff

KEY SPONSORS

California Energy CommissionCalifornia Utilities

Federal Agencies: DOE, DOD, NASA Corporate Affiliates

Special thanks to Southern California Edison for support of work presented todaySlide4

Presentation Overview Does Evaporative Cooling Make Sense in an Arid Climate?What do we mean by Evaporative Cooling?How much water is consumed to save how much energy?

ASHRAE Standard 212P – Rating Performance of Evaporative Pre-CoolersHow can we compare energy savings with changes in water consumption?Slide5

What do we mean by Evaporative Cooling?Evaporative pre-coolers for condensers (and ventilation air)Reduce temperature of air entering condenser coil by direct evaporative cooling of outdoor airCool ventilation air indirectly by running sump water through a fin-coilEvaporative condensers (residential)Outdoor condensing unit flows water over a refrigerant coilIndirect evaporative Dedicated Outdoor Air Systems (DOAS)Ventilation for commercial buildingsSub wet-bulb evaporative fluid coolers

Chill water to below wet-bulb temperature by using chilled water to cool incoming airSlide6

Evaporative Pre-Cooler for Condenser and Ventilation AirCondenser Outlet

Outside Air

Return Air

Supply Air

Condenser Air

Condenser

Condenser Air

Evaporative Pre-cooler

Ventilation Cooling CoilSlide7

Evaporative Condenser SchematicSlide8

Indirect Evaporative Ventilation (DOAS)Slide9

Indirect Evaporative Ventilation (DOAS)Slide10

Sub Wet-Bulb Evaporative Chillers

Use

pre-cooling of outdoor air to drop wet bulb temperature

Allow

production of water (and air) at temperature lower than outdoor-air

wet-bulb temperatureSlide11

Sub-Wet-Bulb Evaporative Cooler TestingSlide12

How Much Water to Save How Much Energy?

How

has

water use been characterized?

Pre-Coolers

Water use efficiency:

[-]

Addresses water that is spilled or otherwise wasted

Generic Metric

=

[

Gallons/ton-h cooling]

 Slide13

How Much Water to Save How Much Energy?

Water-Energy Index

Water Used = Water Evaporated/WUE + Maintenance Water

 Slide14

How Much Water to Save How Much Energy?

Evaporated Water

Key means of cooling

Pre-Cooler: Determined by condenser fan flowrate, wet bulb depression and evaporative effectiveness

Maintenance Water

Required to maintain equipment longevity

Depends on incoming water quality

Research

suggests that most manufacturers use too much maintenance water

Energy Savings

With/Without analysis for evaporative pre-coolers on RTUs

Ventilation cooling with DOAS systems vs. RTU

Indirect evaporative cooling as RTU replacement

S

ub-wet-bulb chillers

a

versus air-cooled chillerSlide15

How Much Water to Save How Much Energy?

Normalized evaporation (WEI)

decreases with outdoor temperature

 Slide16

How Much Water to Save How Much Energy?

RTU 7:

13800 gal/1620 kWh

=

8.5

gal/kWh-saved (actual 188% bleed)

4800

gal/1620 kWh

=

2.9

evaporated

-

gal/kWh-saved

5500

gal/1620 kWh

=

3.4

gal/kWh-saved (15% bleed)Slide17

Maintenance Water: Full-Scale Test of Evaporative Condenser

No Bleed Low Bleed (+19%)Slide18

Maintenance Water: Calcium/Magnesium in CA WaterDavis, CA

Water hardness is made up of different combinations of Ca and Mg

Our lab tests indicate that optimal maintenance water use varies significantly between Ca and Mg

Slide19

Optimized Bleed Rates – Preliminary Model Results% bleed = Vbleed/Vevaporation*100%

Bleed reduces magnesium precipitation but increases calcium precipitationWe use 15% bleed in calculations below

Location

Mg (mg/L)

Ca (mg/L)

Lifespan (

yr

)

Riverside

17

70

10

Eastern

17

62

12

Irvine

11

45

17

Santa Ana

14

73

10

Anaheim

20

97

7

Los Angeles

177010Long Beach22039Davis533314Hypothetical701527Slide20

How Much Water to Save How Much Energy?Evaporative Pre-Cooler Test ProtocolLaboratory testing of evaporative condenser air pre-coolersWCEC tested five pre-coolers on 4-ton York RTUResults reported to

pre-cooler manufacturersSlide21

Evaporative Pre-cooler Test ReportSlide22

ASHRAE Standard for Evaporative Pre-CoolersASHRAE Standard 212PMethod of Test for Determining Energy Performance and Water-Use Efficiency of Add-On Evaporative Pre-Coolers for Unitary Air Conditioning EquipmentDesigned to allow utility programs to understand performance of different evaporative pre-cooler productsMeasures Evaporative Effectiveness and applies to “generic” RTURecent development: Measure Evaporative Effectiveness at multiple face velocitiesSchedule: Vote for Public Review

this yearSlide23

Evaporative Pre-Cooler Test ResultsSlide24

Evaporative Pre-Cooler Test ResultsSlide25

ASHRAE Standard for Evaporative Pre-Coolers Face velocity will also impact WEI Slide26

How Much Water to Save How Much Energy?EquipmentWEI

(gallons/KWh w/15% bleed)

Notes

Min

Max

Avg

Evap

Pre-Cooler

4.3

10.9

7.6

Lab

testing on 11 EER RTU

Evaporative

Condenser

6.1

17

11.6

Lab

testing vs. air-cooled R-22

IDEC

DOAS

1.9

6.5

3.5

Field

testing vs. 11 EER RTU

IDEC

RTU Replacement (0% OA)

7.5

29

13

Field

testing vs. 11 EER RTU

Sub-

Wetbulb

Chiller

2.9

12

5.1

Lab testing vs. air cooled chiller (1 KW/ton)Slide27

Does evaporative cooling make sense in an arid climate?PROSMore savings in arid climatesMaximum electricity reduction is coincident with peak electricity demandCONS

Water consumption a concern during a drought There is always another drought comingSlide28

How can we compare Water USE with Energy SAVINGS?Evaluations above show water use of 2-12 gal/kWh savingsCalifornia average water use for generation is 1.4 -2.8 gal/kWhThermal generation estimated at <1 gal/kWhHydro electric generation estimated at >10 gal/kWhWater-use generation varies by region and timeOn-site water use is larger than off-site savings

Water districts do not benefit from generation savingsa Imperfect Means of Comparison

Does evaporative cooling make sense in an Arid Climate?Slide29

Why not compare Water COST with Energy COST Savings?Water Costs Roughly 10-15% of the value of Energy Cost Savings Does not count demand charges Would make it look betterAdds a lot of complexity

Issue of inappropriate water pricing clouds this comparisonDoes evaporative cooling make sense in an Arid Climate?Slide30

Desalination is Worst-Case Water-Use Scenario(but allows us to compare apples with apples)Desalination produces 70-100 gallons per kWh consumedEvaporative cooling consumes 2-12 gallons/ kWh saveda

6x to 50x electricity multiplierEquivalent to getting back 6-50 kWh

for investing 1 kWh

Does evaporative cooling make sense in an Arid Climate?Slide31

Desalination Analysis (Con’t)Increases water cost approximately 3x a still cost effective10-15% water cost times 3 a 30-45% of electricity cost savingsDesalinization can operate at night and evaporative cooling reduces peak demand during the day

Does evaporative cooling make sense in an Arid Climate?

Answer to the question appears to be

YES

(At least if there is a supply of unpotable water e.g. an ocean)Slide32

Related Upcoming ActivitySlide33

Related Upcoming Activity: Zero-Water Pre-CoolerSlide34

QUESTIONS? ANSWERS?