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

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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