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
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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?