Residential Hot Water Use Patterns and Energy Efficiency

April 29, 2014Advanced Energy Conference - Albany

Hugh HendersonCDH Energy Corp.hugh@cdhenergy.com

Supported by NYSERDAUS DOE Building America 1

Why does DHW Matter?• Water heating 2nd largest load in NY Homes

– Bigger than cooling; approaching magnitude space heating in some highly-efficient homes

– New technologies are being developed

• Performance differences between wide array of DHW technologies not always clear– Performance/efficiency depends on water use (64

gallons/day may not apply any more)– DOE Test and Rating Procedures to determine EF

are currently being revised– Large impact of distribution system performance

2

Project Overview• Side-by-Side Laboratory Testing

– Impose the same water use pattern on systems and compare performance

– Compare solar water heating to other technologies

• Field Testing– Confirm actual field-measured performance– Quantify load profiles in actual homes– Understand impact of HW distribution

• Technology Transfer– Develop a Guide to help consumers

3

Laboratory TestingStandard Gas Water Heater (WH)

4

Unit 1STD GAS(EF=0.58)

Unit 2PWR VNT GAS

(EF=0.67)

Laboratory Testing – Solar/HPWH

5

Unit 3SOLAR

(SEF=3.2)

Unit 4SOLAR DRAIN

Unit 8HPWH

(EF=2.4)

Laboratory TestingHigh Efficiency Gas

6

Unit 6HE COND TANK

(TE=0.96)

Unit 7HYBRID(TE=0.90)

Unit 5TANKLESS(EF=0.94)

Lab Instrumentation

Measure• Flow, ΔT & Q out• Fuel input

Control• Inlet water temp• Flow rate• Specify as daily

profile (multiple draws: time, flow, duration)

7

Gas Storage and Tankless Water Heaters (Units 1, 2, 5, 6, & 7)

Natural gas

Electric

FW

Flow Limiters (1 & 2 gpm)

Solenoid Valves

FG

WE

TC TH

TFG

Cold in Hot out

Imposed Water Use ProfileProposed “Normal Use” pattern

8

09/19/13

22: 0: 2: 4: 6: 8: 10: 12: 14: 16: 18: 20: 22: 0:

18 19 20

0

5

10

15

20

HW

Use

(gal)

Water Use: 65.2 gal/day

Realized Performance in Lab“Normal Profile”, Sep-18 to Oct-31

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NameConversion

Efficiency (-) Rated EF (-) RatioHW Use

(gal/day)Supply Temp

(F)Inlet

Temp (F)Gas STD 0.56 0.58 96.7% 64.90 119.5 65.9HE-PVNT 0.66 0.67 98.8% 81.80 125.2 65.5Solar 1.90 3.20 60.90 130.7 68.1Solar Drain 1.39 63.80 117.4 66.9Tankless 0.86 0.94 91.3% 67.00 119.5 67.1HE-Cond 0.85 0.96 88.9% 64.70 122.7 67.8Hybrid 0.73 0.90 81.3% 60.30 114.8 66.0HPWH 2.70 2.40 112.5% 62.20 120.0 67.7

Field Testing Goal

• Measure HW daily use profiles (all 18 sites)

• Measure inputs, thermal outputs and efficiency as well as component status and operating conditions under actual use patterns (at 3 detailed sites)

• HW distribution measurements at 5 sites. Install temperature sensors on distribution piping to: – allocate water draws to key end uses (sinks, showers,

dishwashers, etc)– Estimate HW “waste” in distribution piping

10

15-minute Profile – 2 People February

11

15-Minute Daily Profile for 2-Person Home in February

0 2 4 6 8 10 12 14 16 18 20 22 24

Hour of Day

0.00

0.10

0.20

0.30

0.40

0.50

Flo

w (

gpm

)

Site 1Site 3Site 5Site 9Site 10Site 11Site 13Site 14Site 15

9 SitesAverage Daily Total: 42.6 gal/dayDaily Range: 0.0 to 110.8 gal/day

A Kitchen Sink Draw Event

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12/02/12 09:05:50 GAL = 0.27

45. 50. 55. 0. 5. 10. 15.20. 25. 30. 35.

:5 :6

0.0

0.2

0.4

0.6

0.8

1.0F

low

Rat

e (g

pm)

DHW Site 1

45. 50. 55. 0. 5. 10. 15.20. 25. 30. 35.

:5 :6

-10

0

10

20

30

Tem

pera

ture

Ris

e (F

)

TH - Hot TC = Cold

1

2 3 4 5 6 7 8 1 2

3

4 5

12/02/12 09:05:50 Intervals=10

45. 50. 55. 0. 5. 10. 15.20. 25. 30. 35.

:5 :6

40

60

80

100

120

140

Tem

pera

ture

(F

)

1 2 3 4 5

6

7 8

1

2 3

4 5

TF2: Fixture Temp 2 - Kitchen Sink: Rise= 5.5 TF3: Fixture Temp 3 - Sink (half bath): Rise= 0.4

TT3: Trunk Temp 3 - Kitchen Trunk: Rise= 21.6 TT4: Trunk Temp 4 - Half Bath Trunk: Rise= 0.2

Kitchen Sink

Useful GAL = 0.00 (TF > 90. )

Classification Success Rate

13

Useful = T is Over 90°F at Fixture

Site 1

Events per day

Total HW Use

(gpd)

Useful HW

(gpd)

Wasted HW

(gpd)Useful

%

Dishwasher 1.5 2.7 2.4 0.3 90%Kitchen Sink 17.0 9.1 5.7 3.3 63%Halfbath Sink 2.1 0.7 0.1 0.5 21%Washing Mach 0.7 9.1 8.3 0.8 91%Utility Sink 0.3 0.9 0.5 0.4 53%Master Sink 6.8 2.2 0.6 1.5 28%Master Shower 1.5 17.8 17.0 0.8 95%Bath2 Sink 1.7 1.2 0.6 0.6 49%Bath2 Shower 0.7 8.4 7.7 0.8 91%Unaccounted 36.8 3.4 0.0 3.4 0%All Events 69.4 55.4 42.9 12.5 77%Classified 33 52.0 42.9 9.1 82%% Classified 47% 94% 100% 73%

No of Days: 123 No of Events: 8534

HPWH and Resist Elements

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DHW1 - 04/10/13 to 12/02/13

0 50 100 150 200

Hot Water Use (gal/day)

0.0

0.5

1.0

1.5

2.0

2.5

3.0C

onve

rsio

n E

ffici

ency

(-)

E lements ON

Summary

• Conventional systems perform closest Rated EF

• High efficiency condensing systems below expectations

• Solar systems and HPWH systems strongly dependent on operating conditions

• Draw patterns (and specific events) affect performance– For instance, resistance element operation

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