grid tied water heaters: climatic and seasonal … · 7 / ©2016 navigant consulting, inc. all...
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/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED1 Confidential and ProprietaryConfidential and Proprietary
GRID TIED WATER HEATERS:
CLIMATIC AND SEASONAL
EFFECTS ON OPTIMAL
ENERGY EFFICIENCY AND
LOAD MANAGEMENT
POTENTIAL
ACEEE HOT WATER FORUM 2017
FEBRUARY 28, 2017
-HEMANG NERLEKAR
-BROCK MOSOVSKY
NAVIGANT CONSULTING
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED2 Confidential and Proprietary
CONTEXT
Although it’s well known that Heat Pump Water Heaters(HPWHs) are more efficient
than conventional water heaters, they also have significant potential to be leveraged
for load management and energy storage by connecting them to the grid.
Questions utility program designers should ask themselves are:
• How to assess the value in controlling these water heaters?
• During what time of day is their value maximized?
• How do climate and different seasons affect their operation and load
management/storage capability?
PURPOSE: Help utilities understand the performance of grid-connected HPWHs in
two different climates and seasons for a given set of assumptions
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED3 Confidential and Proprietary
GRID INTERACTIVE WATER HEATERS
• The technology works by heating and storing water at higher temperature (typically
150 F) than the normal set point (typically 120 F) during preferred times (“charging
mode”), and then uses that hot water in times of higher draws during the peak
period (“discharging mode”).
Source: Product websites
Sequentric (not a
HP water heater)
Hubbell Heat
Pump Water
heater
Sanden
SanCO2
(outdoor unit)
Whirlpool heat
pump water
heater
AO Smith
Voltex
GE
GeoSpring
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED4 Confidential and Proprietary
RESIDENTIAL CONFIGURATION
Most models are available in 50 gallon and 80 gallon tank size, can operate in multiple
modes and can have a set point of up to 160 F.
• There are multiple modes:
- Heat Pump (HP) only,
- Electric Resistance (ER) only
- Hybrid – HP with ER backup
- Vacation
• The setpoint can be as high as 160 F for thermal storage purposes during charging mode.
Source: Product websites
*Height and Diameter are based on the 50 gallon tank size.
Model
Available tank
sizes (gal)
Rated Energy
Factor
Height
(inch)*
Diameter
(inch)*
GE GeoSpring 50, 80 Up to 3.39 61 22
A.O. Smith Voltex 50,66,80 Up to 3.24 61 22
Whirlpool heat pump water heater 50,80 Up to 2.75 63 22
Hubbell heat pump water heater 40,50,65,80,119 Up to 3.3 66 25
Sanden SanCO2 (includes an outdoor
unit 35 x 30) 43,83 Up to 3.5 47 22
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED5 Confidential and Proprietary
SIMULATION INPUTS
• Baseline Domestic hot water (DHW) load profile:
- DHW load from BEopt simulation of a typical single family house with a 50 gallon tank
and average rated EF of 0.85.
• Load Offset: 4.5 kW
- Baseline technology is standard efficiency 2 element electric resistance water heater
with 4.5 kW demand
• Storage Capacity: 2.7 kWh
- Allowable temperature band from 110-140 degrees F
- Storage capacity is difference in electric resistance energy required to heat tank from
110 - 140 degrees F
• Charge Rate: 4.5 kW in electric resistance mode
- Depends on ambient temperature when in heat pump mode and ranges from 0.2 to
0.4 KW
- Heat pump mode requires ambient temp of 58.6 degrees F or greater
• Decay Rate: 0.74% per hour
- Corresponds to about 0.02 kWh per hour loss at full charge
• Location of water heater: Unconditioned basement or garage
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED6 Confidential and Proprietary
SIMULATION METHODOLOGY – CUSTOMER PERSPECTIVE
The goal is to minimize the customer’s water heating bill subject
to retail rates.• Optimize: operation to match hourly baseline equivalent kW
- Heat pump mode depends on ambient temperature
- Hourly dry bulb temperature profile for each month used to define hourly heat
pump mode’s max output
• Constraints:
- For each hour, if heat pump max output is greater than water heating demand,
then heat pump mode will be used
- Otherwise, electric resistance mode is be used
• Retail Rate Scenario:
- Peak Time of Use(TOU) pricing from 3 PM to 8 PM on weekdays only
- $5/kW-month demand charge, applicable to loads during peak TOU hours only
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED7 Confidential and Proprietary
SEASON AND CLIMATE SELECTION
• Simulated the operation of a HPWH in multiple climates and seasons:
- Winter and summer operation in hot and cold climates.
- Phoenix represents the hot climate and Boston represents cold climate.
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Degre
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Boston Ambient Temperature Profile
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Jul Aug Sep Oct Nov Dec
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Phoenix Ambient Temperature Profile
Jan Feb Mar Apr May Jun
Jul Aug Sep Oct Nov Dec
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED8 Confidential and Proprietary
LOAD PATTERN FOR DIFFERENT CLIMATES IN JANUARY
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urly d
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an
d(k
W)
Boston January Weekend + Weekday Load Profiles
Grid kWh to load Storage discharge to Load Retail rate ($/kWh)
Heat pump mode Grid kWh to charge storage
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an
d(k
W) Phoenix January Weekend + Weekday Load Profiles
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED9 Confidential and Proprietary
PRE-POST LOADSHAPES IN JANUARY
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rly d
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W)
Hours of day
Boston January Pre-Post Loadshapes
Baseline load(Pre) Load after DHW storage(Post)
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Hourly d
em
and(k
W)
Hours of day
Phoenix January Pre-Post Loadshapes
Baseline load(Pre) Load after DHW storage(Post)
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED10 Confidential and Proprietary
LOAD PATTERN FOR DIFFERENT CLIMATES IN JULY
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Ho
urly D
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d (
kW
)
Hours of day
Phoenix July Weekend + Weekday Load Profiles
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Hours of day
Boston July Weekend + Weekday Load Profiles
Grid kWh to load Storage discharge to load Retail rate ($/kWh)
Heat pump mode Grid kWh to charge storage
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED11 Confidential and Proprietary
PRE-POST LOADSHAPES IN JULY
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urly d
em
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W)
Hours of day
Boston July Pre -Post Loadshapes
Baseline Load(Pre) Load after DHW Storage(Post)
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em
and(k
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Hours of day
Phoenix July Pre-Post Loadshapes
Baseline Load(Pre) Load after DHW storage(Post)
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED12 Confidential and Proprietary
MONTHLY ENERGY SAVINGS
HPWHs provide year round energy savings in hot climates, but they are valuable only
in summer months in cold climates.
0
100
200
300
400
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecEnerg
y onsum
ption(k
Wh)
Monthly DHW Energy Consumption (kWh) in Boston
Baseline Energy Consumption(kWh) Efficient Energy Consumption(kWh)
0
100
200
300
400
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
En
erg
y c
on
su
mp
tio
n(k
Wh
)
Monthly DHW Energy Consumption (kWh) in Phoenix
Baseline Energy Consumption(kWh) Efficient Energy Consumption(kWh)
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED13 Confidential and Proprietary
MONTHLY ENERGY SAVINGS
HPWHs provide year round energy savings in hot climates, but they are valuable only
in summer months in cold climates.
0
100
200
300
400
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecEnerg
y onsum
ption(k
Wh)
Monthly DHW Energy Consumption (kWh) in Boston
Baseline Energy Consumption(kWh) Efficient Energy Consumption(kWh)
Annual EE savings =
957 kWh
0
100
200
300
400
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
En
erg
y c
on
su
mp
tio
n(k
Wh
)
Monthly DHW Energy Consumption (kWh) in Phoenix
Baseline Energy Consumption(kWh) Efficient Energy Consumption(kWh)
Annual EE savings =
1468 kWh
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED14 Confidential and Proprietary
STORAGE DISCHARGE
The storage discharge potential is determined by how often the HPWH goes in the
heat pump mode and can generate more energy than the DHW demand.
0
20
40
60
80
100
120
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Sto
rage
po
ten
tia
l(kW
h)
Storage Discharge in baseline equivalent kWh in Phoenix
Storage Discharge in baseline equivalent kWh in Boston
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED15 Confidential and Proprietary
FUTURE WORK
• Although we match the DHW load, we want to make sure that hot water is delivered
at the tap.
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED16 Confidential and Proprietary
THANK YOU !
/ ©2016 NAVIGANT CONSULTING, INC. ALL RIGHTS RESERVED17 Confidential and Proprietary
HEMANG NERLEKARSenior Consultant
navigant.com
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