Residential Hot Water Use
Patterns and Energy Efficiency
April 29, 2014
Advanced Energy Conference - Albany
Hugh Henderson
CDH Energy Corp.
hugh@cdhenergy.com
Supported by
NYSERDA
US 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 performance2
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 Testing
Standard Gas Water Heater (WH)
Unit 1
STD GAS
(EF=0.58)
Unit 2
PWR VNT GAS
(EF=0.67)
4
Laboratory Testing – Solar/HPWH
Unit 3
SOLAR
(SEF=3.2)
Unit 4
SOLAR DRAIN
Unit 8
HPWH
(EF=2.4)
5
Laboratory Testing
High Efficiency Gas
Unit 5
TANKLESS
(EF=0.94)
Unit 6
HE COND TANK
(TE=0.96)
Unit 7
HYBRID
(TE=0.90)
6
Lab Instrumentation
Gas Storage and Tankless Water Heaters (Units 1, 2, 5, 6, & 7)
Cold in
Hot out
TC
TH
Flow Limiters
(1 & 2 gpm)
TFG
FW
•
•
Solenoid
Valves
•
•
•
WE
Electric
Natural gas
Measure
Flow, ΔT & Q out
Fuel input
Control
Inlet water temp
Flow rate
Specify as daily
profile (multiple draws:
time, flow, duration)
FG
7
Imposed Water Use Profile
Proposed “Normal Use” pattern
09/19/13
20
Water Use: 65.2 gal/day
HW Use (gal)
15
10
5
0
22:
0:
18
19
2:
4:
6:
8:
10:
12:
14:
16:
18:
20:
22:
0:
20
8
Realized Performance in Lab
“Normal Profile”, Sep-18 to Oct-31
9
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
15-Minute Daily Profile for 2-Person Home in February
0.50
Site
Site
Site
Site
Site
Site
Site
Site
Site
Flow (gpm)
0.40
9 Sites
Average Daily Total: 42.6 gal/day
Daily Range: 0.0 to 110.8 gal/day
1
3
5
9
10
11
13
14
15
0.30
0.20
0.10
0.00
0
2
4
6
8
10
12
14
Hour of Day
16
18
20
22
24
11
A Kitchen Sink Draw Event
12/02/12 09:05:50 GAL = 0.27
0.8
0.6
0.4
0.2
0.0
45. 50. 55. 0. 5. 10. 15.20. 25. 30. 35.
:5
:6
140
TC = Cold
30
3
20
10
2
43
2
1
5
1
8
7
6
5
4
0
-10
45. 50. 55. 0. 5. 10. 15.20. 25. 30. 35.
:5
12/02/12 09:05:50 Intervals=10
Temperature (F)
TH - Hot
Temperature Rise (F)
Flow Rate (gpm)
1.0
:6
TT3: Trunk Temp 3 - Kitchen Trunk: Rise= 21.6
TT4: Trunk Temp 4 - Half Bath Trunk: Rise= 0.2
120
1
100
3
2
6
80
4
2
3
8
5
1
57
4
60
40
45. 50. 55. 0. 5. 10. 15.20. 25. 30. 35.
:5
Kitchen Sink
Useful GAL = 0.00 (TF > 90. )
TF2: Fixture Temp 2 - Kitchen Sink: Rise= 5.5
TF3: Fixture Temp 3 - Sink (half bath): Rise= 0.4
:6
DHW Site 1
12
Classification Success Rate
Site 1
Dishwasher
Kitchen Sink
Halfbath Sink
Washing Mach
Utility Sink
Master Sink
Master Shower
Bath2 Sink
Bath2 Shower
Unaccounted
All Events
Classified
% Classified
No of Days:
Events Total HW
per
Use
day
(gpd)
1.5
17.0
2.1
0.7
0.3
6.8
1.5
1.7
0.7
36.8
69.4
33
47%
123
2.7
9.1
0.7
9.1
0.9
2.2
17.8
1.2
8.4
3.4
55.4
52.0
94%
Useful Wasted
HW
HW Useful
(gpd)
(gpd)
%
2.4
0.3
5.7
3.3
0.1
0.5
8.3
0.8
0.5
0.4
0.6
1.5
17.0
0.8
0.6
0.6
7.7
0.8
0.0
3.4
42.9
12.5
42.9
9.1
100%
73%
No of Events:
Useful = T is Over 90°F at Fixture
90%
63%
21%
91%
53%
28%
95%
49%
91%
0%
77%
82%
8534
13
HPWH and Resist Elements
DHW1 - 04/10/13 to 12/02/13
3.0
Conversion Efficiency (-)
2.5
2.0
1.5
1.0
Elements ON
0.5
0.0
0
50
100
Hot Water Use (gal/day)
150
200
14
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
15