Residential Heat Pump Water Heaters

Proven UES Measure Proposal Regional Technical Forum October 14, 2014

2

Presentation Outline

• • • • • • Measure Overview Plan for HPWH Staff Highlighted Areas Provisional Research Results Model Calibration UES Development

3

Measure Overview

Measure Developers Contract Analyst Review Technical Subcommittee Review Research & Evaluation Core Group Review Notes

Ecotope, NEEA, BPA Yes (Christian Douglass, Adam Hadley) No N/A Provisional UES measure approved in October of 2011. Additional Tier 2 units added to provisional measure in February of 2012.

• Review the Measure Properties section on the “Summary” tab of the proposed measure workbook .

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)

• The measures cross the entire PNW and are not separated by climate zone

Annual Energy Saving (kWh/yr) HPWH Location

Unheated Buffer Location Interior Location Interior Location Interior Location Interior Location

Space Heat Type

Any Heat Type Gas Heated Home Zonal Electric Heated Home Electric Furnace Heated Home Heat Pump Heated Home

Tier 1 Small Tank

887 1,547 648 556 1,189

Tier 2 Large Tank

1,817 2,169

Any Size

1,794 1,724 957 833 1,686 952 837 1,243

9

Research Plan & Outcomes

• http://rtf.nwcouncil.org/meetings/2012/02/HPWH_Ducted_Interior_Instal lations_Provisional_Proposal_021412_v5.pptx

Study Area

Hot Water Consumption

Research Outcome

100+ Households successfully metered. Draw profiles created for 1, 2, 3, 4, & 5+ occupancy households Indeterminate

Status

Space Conditioning Interaction 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 Voltex 60 & 80 Gallon ATI 66 gallon GeoSpring 50 gallon Total Climate Zone Basement

HZ1 HZ2 HZ3 All HZ1 HZ2 HZ3 All HZ1 HZ2 HZ3 All

All

6 3 0 4 2 0 2 9

18

0 3 4 3

Installation Location Interior Garage Interior Ducted

9 1 0 4 0 6 1 1 0 13 8 5 0 13 16 2 0 18

44

8 0 0 0 0 2 2 2 6

14

1 12 11 7 30 0 0 0 0

31 Total 7 46 22 7 4 33 107 14 13 1 28 23 16

11

Quick Findings Summary

Annualized Water Heater Energy Use (kWh/yr) Equipment

Basement Garage Interior

ATI

Mean 1,678 n 16 Mean 1,380 n 13 Mean 1,201 n 15

GeoSpring Voltex

1,600 1,696 9 6 2,185 2,208 17 13 1,549 1,785 6 8

Equipment Annualized kWh per 100 Gallons Delivered

Basement Garage

ATI GeoSpring Voltex

Mean 10.3

10.8

8.2

n 16 8 3 Mean 10.7

13.2

12.0

n 13 17 13 Interior Mean 10.7

10.7

9.9

n 13 5 6

12

More Findings – DHW annual COP

Make ATI GeoSpring Voltex ATI GeoSpring Voltex ATI GeoSpring Voltex ATI GeoSpring Voltex

-

Basement Garage Heating Zone 1

Mean 2.03

n 6 Mean 2.05

n 9 1.95

2.59

2.20

2.20

2.31

2.18

2.24

2.13

2.09

2.49

4 2

Heating Zone 2

4 1.94

2 1

Heating Zone 3

6 2 0 16 8 3 1.63

2.13

1.69

1.84

Overall

2.02

1.63

2.03

15 7 4 1 4 0 0 0 13 16 11 Mean 2.06

2.34

1.96

2.39

2.28

2.43

1.97

2.58

2.05

2.20

2.33

Interior

1 2 1 n 7 2 0 5 1 5 13 5 6

13

Developing the UES

• Billing analysis not able to evaluate changes in water heating energy use • Validated inputs feed a calibrated simulation  Reliable 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

Condenser coils wrapped outside of tank Resistance Element Resistance Element Condenser coils immersed in tank

15

Water Heater Simulation Background

• • • • – – – Information needed for a simulation Input Power – COP – f(T ambient air , T tank water ) f(T ambient air , T tank 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 Match

Bright 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 Curves

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 GE Voltex 60 Voltex 80 ATI66 16 14 8 19 Simple Flow Weighted Simple Flow Weighted Simple Flow Weighted Simple Flow Weighted Actual kWh Simulated kWh Error (kWh) Error (%) Frac Matching

132 148 103 122 159 187 159 233 131 150 103 123 143 159 156 234 1 -16 -28 -2 1 2 0 0 -1% 1% 0% 1% -10% -15% -1% 0% 0.70

0.71

0.73

0.76

0.82

0.85

0.69

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 Study – 1 (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.

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Updates to Simulation Parameters

Parameter Tank Setpoint Provisional

~122.5°F

Proven

128°F

Uncertainty

Low

Inlet Water Temperature Hot Water Consumption Ambient Space Temperatures Heating System Interaction

Assumed constant ~50°F 45 gal/day with no draw schedule Estimates with “loosely” calibrated simulations Assumed to be full Varies throughout the year and based on water source 40 gal/day average. Independent draw schedules for 1, 2, 3, 4, & 5+ person households Calculated based on model fits to observed data 50% ???

Low Low-Med Low 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 3 4 Total Flow (Gal)

46 57 .

.

Median Time (Hr of Day)

7.1

10.5

15.5

19.1

22.2

7.4

10.5

15.4

19 21.8

.

.

Cluster Span (Minutes)

48.5

71.5

75.1

81.6

43.5

63.4

67.3

76.2

72 29.5

Draws per Cluster (count)

2.6

3.1

3 4 2.1

0.6

3.1

2.9

3 3.5

1.6

0.5

Flow per Cluster (Gal)

10.9

9.2

7.3

11.2

5.8

1.6

18.4

12.4

8.6

11.8

4.3

1.7

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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

Average measured kWh: 1,664 Average modeled kWh: 1,473 Difference: 11.5% Looks like there may be a bias, particularly at high consumption sites.

This piece of work UNDER CONSTRUCTION.

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 saturation 1 – 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 rate 1 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

RTF Judgment Required Ahead

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

35

Measure Definition: Issues (cont’d)

RTF Judgment Required Ahead

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

36

Preliminary Simulation Results: Hot Water Savings Only

(i.e. no HVAC interaction added yet)

DHW Savings 2 000 1 750 1 500 1 250 1 000 750 500 250 Garage Tier 1 Garage Tier 2 Basement Tier 1 Basement Tier 2 Interior Tier 1 Interior Tier 2 Ducted Tier 2 HZ1 1 173 1 558 1 296 1 549 1 420 1 473 1 306 HZ2 987 1 669 1 338 1 628 1 495 1 535 1 359 HZ3 844 1 765 1 370 1 708 1 560 1 609 1 431

37

Cost Data

RTF Judgment Required Ahead Equipment Total Cost

Electric Resistance 50 gal GE GeoSpring (50 gal) AO Smith Voltex (60 & 80 gal) AirGenerate ATI

2014$s Source

$ 400 Price survey $ 1,109 NEEA & BPA dataset $ 1,495 NEEA & BPA dataset $ 2,268 NEEA & BPA dataset

Notes

EF 0.95 - baseline

Baseline Measure Equip Cost

Tank Size <= 55 gallons, EF=0.95

(60 & 80 gal) $ 1,095 AirGenerate ATI $ 1,868 Tier 1 Tier 2 $ 760 $ 1,868 Tank Size > 55 gallons, EF>2.0, assumed to be Tier 1 GE GeoSpring (50 gal) AO Smith Voltex Tier 2 Ducted Tier 2 Tier 2 Ducted $ 709 $ 1,868 $ 773 $ 773

Incremental Costs (2014$s) Contractor Install Self Install Final Contractor Final Self

$ 108 $ 42 $ 174 $ 42 $ 1,269 $ 1,136 $ 1,162 $ 374 $ 227 $ 2,241 $ 2,095 $ 2,230 $ 117 $ 42 $ 174 $ 42 $ 2,042 $ 1,909 $ 2,031 $ 374 $ 227 $ 2,241 $ 2,095 $ 2,230 $ - $ $ 199 $ 185

$ 817 $ 751 $ 877 $ 801 $ 773 $ 773 $ 972 $ 958 Final Overall $ 764 $ 816 $ 773 $ 971 For self-installs, do we still want to value people’s time at $0?

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

Conditioned Space Installation Heat Flows

Cool HPWH Exhaust Air Warm House Air Tank Heat Losses

• • HVAC System Interaction = m*c p *ΔT + Q UA Typical air Δ T at 68  F entering air: ~15  F 39

Ducted, Conditioned Space Heat Flows

Cool HPWH Exhaust Air Warm House Air Added Infiltration Load Tank Heat Losses

• • • HVAC System Interaction = m*c p *ΔT + Q UA Δ T now depends on outside air T m now depends on added infiltration load 40

41

Heating System Interaction Factors

• • •

RTF Judgment Required Ahead

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 Study 1 – 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.

42

Heating System Interaction Factors

RTF Judgment Required Ahead

• 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

43

Sensitivity of Total Savings to Heating Interaction Factor (%)

1 800

Tier 1, Interior

1 600 1 400 1 200 1 000 800 600 400 200 -

Interaction Factor

25% 50% 75% 100% HZ1 HZ2 HZ3 Zonal Electric Resistance HZ1 HZ2 HZ3 Electric Furnace HZ1 HZ2 Heat Pump HZ3

44 1 800

Sensitivity of Total Savings to Heating Interaction Factor (%)

Tier 2, Interior (Non-Ducted)

1 600 1 400 1 200 1 000 800 600 400 200 -

Interaction Factor

25% 50% 75% 100% HZ1 HZ2 HZ3 Zonal Electric Resistance HZ1 HZ2 HZ3 Electric Furnace HZ1 HZ2 Heat Pump HZ3

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 U 0 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 Any Zonal Electric Resistance Electric Furnace Heat Pump Gas Furnace Location Garage Basement Interior Ducted Interior Ducted Interior Ducted Interior Ducted Tier Tier1 Tier2 Tier1 Tier2 Tier1 Tier2 Tier2 Tier1 Tier2 Tier2 Tier1 Tier2 Tier2 Tier1 Tier2 Tier2 HZ1

1.9

0.9

2.0

0.9

1.6

0.7

0.5

1.5

0.6

0.5

1.9

0.8

0.6

1.7

0.8

0.6

Climate Zone HZ2

1.6

1.0

2.1

0.98

1.7

0.7

0.5

1.7

0.7

0.6

1.9

0.8

0.6

1.8

0.8

0.7

HZ3

1.3

1.1

2.2

1.0

1.9

0.8

0.6

1.8

0.7

0.6

2.0

0.8

0.7

1.9

0.9

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