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Residential Heat Pump Water Heaters Proven UES Measure Proposal. Regional Technical Forum October 14, 2014. Measure Overview Plan for HPWH Staff Highlighted Areas Provisional Research Results Model Calibration UES Development. Presentation Outline. - PowerPoint PPT Presentation
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Residential Heat Pump Water HeatersProven UES Measure Proposal
Regional Technical ForumOctober 14, 2014
2
Presentation Outline
• Measure Overview• Plan for HPWH• Staff Highlighted Areas• Provisional Research Results• Model Calibration• UES Development
3
Measure Overview
• Review the Measure Properties section on the “Summary” tab of the proposed measure workbook.
Measure Developers Ecotope, NEEA, BPAContract Analyst Review Yes (Christian Douglass, Adam Hadley)Technical Subcommittee Review NoResearch & Evaluation Core Group Review
N/A
Notes Provisional UES measure approved in October of 2011. Additional Tier 2 units added to provisional measure in February of 2012.
4
Plan for HPWH
• Receive RTF direction on a number of important issues (outlined in the next couple of slides)
• No decision today– Contract analysts have undergone extensive review of
measure analysis and documentation– Contract analysts have high confidence in nearly all aspects
of the HPWH model, calibration, and model inputs– Remaining issue is further alignment of modeled and
measured energy consumption using generic water draw profiles (slide 31)
• Bring final UES measure back for proposed decision next month
5
Staff Highlighted Areas• Model calibration
– Does the RTF believe that the HPWH simulation model is sufficiently calibrated?
• HVAC interaction factor (interior installs only)– Provisional measure assumed full HVAC interaction
(≈100%); provisional research was inconclusive on this– Analysts believe value likely falls between 25 and 100%– Use an assumption in this range OR pursue additional
research?• If we use an assumption:
– Measure proposer suggests 50% – RTF contract analysts suggest 75%
RTF Judgment Required Ahead
6
Staff Highlighted Areas (continued)• How to treat impending federal standard (Apr 2015)
in measure savings computation– Should all measure savings be subject to the standard now,
or should the RTF develop separate savings which are valid until the standard goes into effect?– Can we have an “any size” tank measure that assumes the current distribution of tanks going through programs? What about after the standard goes into effect?
• For self-installs, does the RTF still want to value people’s time at $0?
RTF Judgment Required Ahead
Current Provisional Measures• Base case water heater
– Electric resistance tank (COP ≈ 0.90)
• Efficient case heat pump water heaters (HPWHs):– Tier 1, 50-75 gallons (COP ≈ 1.69)– Tier 1, 75+ gallons (COP ≈ 2.29)– Tier 2, any size tank (COP ≈ 2.30)
• Install locations– Unheated buffer locations
• Includes garages and basements together
– Heated installations • One measure for each of gas furnace, electric furnace, zonal resistance,
and heat pump heating• Tier 1 water heaters have no exhaust ducting• Tier 2 water heaters all have exhaust ducting
Current Provisional Measures (continued)
Annual Energy Saving (kWh/yr) Tier 1 Tier 2
HPWH Location Space Heat TypeSmall Tank
Large Tank Any Size
Unheated Buffer Location Any Heat Type 887 1,817 1,794 Interior Location Gas Heated Home 1,547 2,169 1,724 Interior Location Zonal Electric Heated Home 648 957 952 Interior Location Electric Furnace Heated Home 556 833 837 Interior Location Heat Pump Heated Home 1,189 1,686 1,243
• The measures cross the entire PNW and are not separated by climate zone
9
Research Plan & Outcomes• http://
rtf.nwcouncil.org/meetings/2012/02/HPWH_Ducted_Interior_Installations_Provisional_Proposal_021412_v5.pptxStudy Area Research Outcome Status
Hot Water Consumption
100+ Households successfully metered. Draw profiles created for 1, 2, 3, 4, & 5+ occupancy households
Space Conditioning Interaction
Indeterminate
In-field COP • 100+ Households successfully metered.
• Inlet & outlet water temperature. • Ambient air temperature. • Water heater energy use.
10
Field Study Research• BPA (conducted by EPRI): ~50 units from Rheem, GE, AO Smith• NEEA (conducted by CleaResult): 30 AirGenerate Units • NEEA (conducted by Ecotope): 50 GE, AO Smith, AirGenerate Units
Equipment Climate Zone
Installation Location
Basement Garage Interior Interior Ducted Total
Voltex60 & 80 Gallon
HZ1 4 9 1 0 14HZ2 2 4 6 1 13HZ3 0 0 1 0 1All 6 13 8 1 28
ATI66 gallon
HZ1 3 8 0 12 23HZ2 0 5 0 11 16HZ3 0 0 0 7 7All 3 13 0 30 46
GeoSpring50 gallon
HZ1 4 16 2 0 22HZ2 3 2 2 0 7HZ3 2 0 2 0 4All 9 18 6 0 33
Total All 18 44 14 31 107
11
Quick Findings Summary
Annualized kWh per 100 Gallons Delivered
EquipmentBasement Garage Interior
Mean n Mean n Mean nATI 10.3 16 10.7 13 10.7 13
GeoSpring 10.8 8 13.2 17 10.7 5
Voltex 8.2 3 12.0 13 9.9 6
Annualized Water Heater Energy Use (kWh/yr)
EquipmentBasement Garage Interior
Mean n Mean n Mean nATI 1,678 16 1,380 13 1,201 15GeoSpring 1,600 9 2,185 17 1,549 6Voltex 1,696 6 2,208 13 1,785 8
12
More Findings – DHW annual COP Basement Garage Interior
Heating Zone 1Make Mean n Mean n Mean nATI 2.03 6 2.05 9 2.06 7GeoSpring 1.95 4 1.63 15 2.34 2Voltex 2.59 2 2.13 7 - 0
Heating Zone 2ATI 2.20 4 1.94 4 1.96 5GeoSpring 2.20 2 1.69 1 2.39 1Voltex 2.31 1 1.84 4 2.28 5
Heating Zone 3ATI 2.18 6 - 0 2.43 1GeoSpring 2.24 2 - 0 1.97 2Voltex - 0 - 0 2.58 1
OverallATI 2.13 16 2.02 13 2.05 13GeoSpring 2.09 8 1.63 16 2.20 5Voltex 2.49 3 2.03 11 2.33 6
13
Developing the UES• Billing analysis not able to evaluate changes in water
heating energy use
• Validated inputs feed a calibrated simulationReliable estimates of energy use & savings
• Topics to discuss– Water Heater Simulation Calibration – Simulation Inputs and Measure Parameters– Measure Definitions– HVAC Interaction Factors
14
HPWH Simulation Calibration
Resistance Element
Condenser coils immersed in tank
Resistance Element
Condenser coils wrapped outside of tank
15
Water Heater Simulation Background
• Information needed for a simulation– Input Power – f(Tambient air, Ttank water)– COP – f(Tambient air, Ttank water)– Control logic– Tank storage volume– Tank heat loss rate (UA)– Where does the heat get added to the tank?
• Unique simulations for GE GeoSpring, AO Smith Voltex, and AirGenerate ATI
• Simulation runs at 1-minute time steps• Fully integrated with SEEM
16
Simulation Calibration
• Use field data as our “ground truth”• Feed field data for water draw, inlet water temperature,
and ambient air temperature to simulation– Simulation outputs runtime for compressor and resistance
elements• Goal is to match simulation output to field data• Optimize Simulation:
– Use Markov Chain Monte Carlo (MCMC) to incrementally vary simulation parameters like COP curves and temperature deadbands.
– Run lots of simulations and look for best match
17
Voltex Simulation Example 1 - Good MatchBright blue area shows
actual power use; orange line is model- predicted power use.
Taller spikes show resistance heat
turning on; smaller area represents the heat pump running.
The goal is to have the orange line predict (i.e. outline) the blue area;
it does that near perfectly for this site.
18
Voltex Simulation Example 2 – Bad Match
For this site… not so much. First, the model predicted resistance heat
turning on, which did not happen in reality. Second, the model predicted compressor runtime events, but did not match the timing or duration of
the actual events.
19
Calibrated COP CurvesAO
Sm
ith V
olte
xAi
rGen
erat
e AT
IG
E G
eosp
ring
20 Measured vs. Calibrated Modeled Energy Consumption (kWh) – Sites in Calibration Set
Calibration results for the 50 sites used as the basis of the calibration. Uses
actual site inputs (water draw, inlet water temp).
21
Calibration Results
Unit # sites Average Type Actual kWh
Simulated kWh
Error (kWh) Error (%) Frac
Matching
GE 16 Simple 132 131 1 -1% 0.70
Flow Weighted 148 150 2 1% 0.71
Voltex 60 14 Simple 103 103 0 0% 0.73
Flow Weighted 122 123 1 1% 0.76
Voltex 80 8 Simple 159 143 -16 -10% 0.82
Flow Weighted 187 159 -28 -15% 0.85
ATI66 19 Simple 159 156 -2 -1% 0.69
Flow Weighted 233 234 0 0% 0.75
Frac Matching is defined as the fraction of simulated ontime that coincided with observed ontime.
22
Measured vs. Calibrated Modeled Energy Consumption (kWh) – All Sites
• Calibration Set, n = 57• Test Set, n = 29• Total, n = 86• Sites excluded due to
– measurement failures (e.g. no flow or ambient temperature)
– suspected HPWH failures
– data handling burden Uses actual site
inputs (water draw, inlet water temp).Does the RTF believe that the
HPWH simulation model is sufficiently calibrated?
23 Calculation Inputs and Simulation Parameters
• As measured and documented in the HPWH Model Validation Study1 (the study designed to bring this measure from provisional to proven) – Water Draw Profiles– Inlet Water Temperature– Tank Set Point– Ambient Space Temperatures
• These were almost completely unknown for the provisional measure
• Validated inputs feed the calibrated simulation model Reliable estimates of energy use & savings
1 NEEA. Heat Pump Water Heater Model Validation Study (Draft). Prepared by Ecotope. July 2014.
24
Updates to Simulation ParametersParameter Provisional Proven Uncertainty
Tank Setpoint ~122.5°F 128°F Low
Inlet Water Temperature
Assumed constant ~50°F
Varies throughout the year and based on water source
Low
Hot Water Consumption
45 gal/day with no draw schedule
40 gal/day average. Independent draw schedules for 1, 2, 3, 4, & 5+ person households
Low-Med
Ambient Space Temperatures
Estimates with “loosely” calibrated simulations
Calculated based on model fits to observed data
Low
Heating System Interaction
Assumed to be full 50% ??? High
25
Measured Daily Ave Hot Water Use
26
Hourly Average Hot Water Draws
27
Draw Profile Derivation
• Goal: create typical (generic) draw profiles suitable for use in a simulation
• Method:– Collect descriptive characteristics of observed draws and create our
own, typical patterns– Characteristics
• Total draw volume• Number of small, medium, & large draws (1-2, 3-9, 10+ gals)• Average size of small, medium, & large draws• Time of draws
– Different pattern for different numbers of occupants• 1, 2, 3, 4, & 5+ occupants• Total flow in daily pattern must equal observed average daily flow
28
Draw Derivation (continued)• Characterize by “Windows” of draw activity within a day
– Observed draw events typically clustered within a window of activity– Collect the average characteristics for each window
• 3 & 4 Occupant Daily Example:
Occupant Count
Total Flow (Gal)
Median Time
(Hr of Day)Cluster Span
(Minutes)Draws per
Cluster(count)
Flow per Cluster (Gal)
3 46
7.1 48.5 2.6 10.910.5 71.5 3.1 9.215.5 75.1 3 7.319.1 81.6 4 11.222.2 43.5 2.1 5.8
. . 0.6 1.6
4 57
7.4 63.4 3.1 18.410.5 67.3 2.9 12.415.4 76.2 3 8.6
19 72 3.5 11.821.8 29.5 1.6 4.3
. . 0.5 1.7
29 Daily Profile Example
• First Window, centered at 7:30am, 1 hr wide – Draws: 2 small, 1 medium, 1 large
30 Weekly Profile Example
• Repeats every week for entire year• Daily volume scaled every day of the year by change in incoming mains
temperature (less in summer, more in winter)
31 Measured vs. Modeled Energy – All Sites using Generic Model Inputs
Looks like there may be a bias, particularly at high
consumption sites.
This piece of work UNDER CONSTRUCTION.
Average measured kWh: 1,664
Average modeled kWh: 1,473
Difference: 11.5%
32
Measure Definitions• Current practice
– Any HPWH tank sold has savings regardless of size– Current assumptions:
• Baseline is a mix of tank sizes according to the current market saturation1
– 88% ≤ 55 gals and 12% > 55 gals
• After federal standard goes into effect, 12% of market will be forced to buy a HPWH because of federal standard (except for some fraction of those working around the standard) 12% of Tier 1 sales have zero kWh savings (& cost) 12% of Tier 2 sales have reduced kWh savings (& cost)
• Caveat: manufacturers expect some fraction of the large tank population to “work-around” the federal standard
– This analysis assumed 25% work-around rate1 RBSA Single Family Characterstics and Energy Use Report. 2012. Table 109.
33
Measure Definitions
• Tier 1 Equipment Mix– GE GeoSpring is a lower-end Tier 1 performer– AO Smith Voltex and Rheem EcoSense are high-end Tier 1
performers– Generic Tier 1 Unit is 87% low performance unit, 13% high
performance unit based on current program data• Tier 2 Equipment “Mix”
– Generic Tier 2 Unit is 100% Air Generate ATI since this is the only qualifying unit currently available
• Market is evolving rapidly– A short sunset period (≈ 1 year) is recommended to check status
of the market and make adjustments to weightings as needed
34
Measure Definition: Issues
Federal standard coming in April 2015 raises questions concerning the calculation of savings:
1. Should all measure savings assume the new standard now, or should the RTF develop separate savings which are valid until the standard goes into effect?• If new standard is assumed now, large tanks get no
savings (Tier 1) or reduced savings (Tier 2)• Or, RTF could develop two measure sets: one which gives
full savings to large tanks until Apr 2015 at which time they expire, and one which takes effect starting in Apr 2015 and gives reduced savings to large tanks
RTF Judgment Required Ahead
35
Measure Definition: Issues (cont’d)
2. Can we have an “any size” tank measure that assumes the current distribution of tank sizes going through programs? What about after the standard goes into effect?• Currently proposed measure allows any size tank and
weights savings by tank size according to current program throughput
• Options:– Accept proposal and use shorter sunset date to check in on tank sizes
going through programs in the future– Create separate small tank / large tank measures to reflect the
different standards treatment of these two categories– Staff thinks first option is appropriate for now, but creating two
measures may be necessary after the sunset date
RTF Judgment Required Ahead
36 Preliminary Simulation Results: Hot Water Savings Only (i.e. no HVAC interaction added yet)
HZ1 HZ2 HZ3
Garage Tier 1 1172.93097389589 987.054237370629 843.799373101947
Garage Tier 2 1558.36746287553 1668.78084768332 1764.51155898336
Basement Tier 1
1296.17034565578 1338.47452941776 1369.81889893093
Basement Tier 2
1548.80608643334 1628.01953253453 1708.23010103027
Interior Tier 1 1419.68679107037 1495.36040488268 1559.70334565006
Interior Tier 2 1472.68575795148 1535.00066786311 1608.76586494719
Ducted Tier 2 1305.52813954486 1358.9886176066 1430.54376029944
100
500
900
1,300
1,700
DHW Savings
kWh
/ yr
37
Cost DataEquipment Total Cost 2014$s Source Notes Electric Resistance 50 gal $ 400 Price survey EF 0.95 - baseline GE GeoSpring (50 gal) $ 1,109 NEEA & BPA dataset AO Smith Voltex (60 & 80 gal) $ 1,495 NEEA & BPA dataset AirGenerate ATI $ 2,268 NEEA & BPA dataset
Baseline MeasureIncremental Costs (2014$s)
Equip Cost
Contractor Install
Self Install
Final Contractor Final Self Final
Overall
Tank Size <= 55 gallons, EF=0.95
GE GeoSpring (50 gal) $ 709 $ 108 $ 42 $ 817 $ 751 $ 764 AO Smith Voltex (60 & 80 gal) $ 1,095 $ 174 $ 42 $ 1,269 $ 1,136 $ 1,162 AirGenerate ATI $ 1,868 $ 374 $ 227 $ 2,241 $ 2,095 $ 2,230 Tier 1 $ 760 $ 117 $ 42 $ 877 $ 801 $ 816 Tier 2 $ 1,868 $ 174 $ 42 $ 2,042 $ 1,909 $ 2,031 Tier 2 Ducted $ 1,868 $ 374 $ 227 $ 2,241 $ 2,095 $ 2,230
Tank Size > 55 gallons, EF>2.0, assumed to be
Tier 1
Tier 2 $ 773 $ - $ - $ 773 $ 773 $ 773
Tier 2 Ducted $ 773 $ 199 $ 185 $ 972 $ 958 $ 971
For self-installs, do we still want to value people’s time at $0?
RTF Judgment Required Ahead
38
Heating System Interaction
• Applies only to interior ducted or non-ducted installations (i.e. garages and basements are excluded)
• Heat pump water heaters extract heat from the space where they are installed. Some of that heat energy is replaced by the heating system .
• We have observed that not every unit of energy removed from the air by the HPWH is replaced by the heating system
39
• HVAC System Interaction = m*cp*ΔT + QUA
• Typical air Δ T at 68F entering air: ~15F
Warm House Air
Cool HPWH Exhaust Air
Tank Heat Losses
Conditioned Space Installation Heat Flows
40
• HVAC System Interaction = m*cp*ΔT + QUA
• Δ T now depends on outside air T• m now depends on added infiltration load
Warm House Air
Cool HPWH Exhaust Air
Tank Heat Losses
Ducted, Conditioned Space Heat Flows
Added Infiltration Load
41
Heating System Interaction Factors• Field study of interaction factors was inconclusive• Expert judgment needed
– Houses are not single zones (no surprise)– The HPWH install zone can thermally “decouple” to varying degrees
from thermostated part of house– Recommend using the same interaction factor for both unducted and
ducted installations• (when you don’t know something, make the simplest estimates)
• What we know from PNNL Lab Homes Study1
– Interaction factor for interior installations ≈ 49%– Interaction factor for ducted installations ≈ 44%– Study looked at one installation of a HPWH in a closet next to an
exterior wall 1 PNNL. Impact of Ducting on Heat Pump Water Heater Space Conditioning Energy Use and Comfort. July 2014.
RTF Judgment Required Ahead
42
Heating System Interaction Factors
• What to do on interaction factor?1. Consider more research to further explore this
value (PNNL lab homes?)2. Assume a value; if a value is assumed:
• Proposal is to use 50% per the PNNL study• Contract analysts propose 75%, as the PNNL study
looked at a particular installation (next to an exterior wall) which could yield a lower than average value
RTF Judgment Required Ahead
43
Sensitivity of Total Savings to Heating Interaction Factor (%)
HZ1 HZ2 HZ3 HZ1 HZ2 HZ3 HZ1 HZ2 HZ3Zonal Electric Resistance Electric Furnace Heat Pump
-
200
400
600
800
1,000
1,200
1,400
1,600
1,800 Tier 1, Interior
25%50%75%100%
Tota
l Ene
rgy
Savi
ngs (
Hot W
ater
+ H
eatin
g), k
Wh
Interaction Factor
44
Sensitivity of Total Savings to Heating Interaction Factor (%)
HZ1 HZ2 HZ3 HZ1 HZ2 HZ3 HZ1 HZ2 HZ3Zonal Electric Resistance Electric Furnace Heat Pump
-
200
400
600
800
1,000
1,200
1,400
1,600
1,800 Tier 2, Interior (Non-Ducted)
25%50%75%100%
Tota
l Ene
rgy
Savi
ngs (
Hot W
ater
+ H
eatin
g), k
Wh
Interaction Factor
45
Other Notes• Phase I SEEM Calibration implemented
– Of minor importance (only impacts space heating interaction)
– For simplicity, used a full insulation retrofit package to set the building U0
• Phase II SEEM Calibration implemented– Non-utility fuel accounted for
• Water heater scavenges some heat from the wood stove so we don’t see an electric grid penalty but we do need to buy more wood
• Cooling interaction ignored as of this time– Impact is less than loose change in the sofa
46 Preliminary Results: B/C Ratios(Assuming HVAC Interaction Factor of 50%)
Heating System Location Tier Climate Zone
HZ1 HZ2 HZ3
Any
Garage Tier1 1.9 1.6 1.3
Tier2 0.9 1.0 1.1
Basement Tier1 2.0 2.1 2.2
Tier2 0.9 0.98 1.0
Zonal Electric Resistance
Interior Tier1 1.6 1.7 1.9
Tier2 0.7 0.7 0.8Ducted Tier2 0.5 0.5 0.6
Electric FurnaceInterior Tier1 1.5 1.7 1.8
Tier2 0.6 0.7 0.7Ducted Tier2 0.5 0.6 0.6
Heat PumpInterior Tier1 1.9 1.9 2.0
Tier2 0.8 0.8 0.8Ducted Tier2 0.6 0.6 0.7
Gas FurnaceInterior Tier1 1.7 1.8 1.9
Tier2 0.8 0.8 0.9Ducted Tier2 0.6 0.7 0.7
47
Additional Slides For Reference
48
49
Spokane TMY3 Inlet Water Example
50
Inlet Water Profiles Used
• HZ1 – city surface• HZ2 – city ground• HZ3 – well• The water-flow, weighted saturation of water
distribution types is unknown. Assignments made above are meant to be representative of the climate zones.
51 Seattle Garage and Unhtd Basement Air Temperature Example
52
53
Measured vs. Modeled COP for All Sites using Generic Model Inputs
54
COP Difference (Modeled - Measured) vs. Flow for All Sites using Generic Model Inputs