Transcript Residential Variable Capacity Heat Pump Field and Lab Testing: Final Results 20 November 2013 Ecotope.

Residential Variable Capacity Heat Pump
Field and Lab Testing: Final Results
20 November 2013
Ecotope
1
History
• Inverter-driven compressor tech making increasing
inroads (ductless systems now at 20,000 plus installs in
NW); BPA has incented central ducted systems via PTCS
on provisional basis
• Advisory committee formed to guide research plan
– Range of experience on committee
– Interest in zoned systems, delivery temperatures
– Timeline/budget limited research scope
• Study summary
–
–
–
–
Heating season only
‘Detailed’ (full capacity/COP) vs non-detailed sites
Combination of field/lab info (EPRI)
ASHRAE 152 duct model exercised plus SEEM for full season
estimates
2
Major Findings – Expectations/Reality
• VCHP performs 25-30% better than a single speed
7.9 HSPF heat pump on an annual basis (note
nominal average HSPF for this product ~12).
• Duct losses increased ~5% over a single speed
heat pump
• Overall system offers improved performance over
single speed base cases
• Heat pump sizing still matters
• Auxiliary heat lockout control still matters
3
Field Deployment
• Planning/refinement occurred through late 2012
• Field deployment set for late February, 2013 (six sites);
central OR chosen for likelihood of remaining cold
weather (about 24 potential sites)
• Critical points measured
– 5 minute metering for electricity usage (including air
handler circuit power- CFM mapping)
– One-time measurements of house heat loss (including
blower door test (system sizing, heating season
simulation)), duct area/R-values, duct leakage, system CFM
(at least 3 points so CFM could be correlated with power),
heat pump control settings
4
Site Pictures
5
Site Summaries
Siteid
Location
OD
House Heated Occs
unit
Type Floor
size
Area
(tons)
(ft2)
PTCS PTCS Strip
HP? Ducts heat
lockout
?
temp.
91001
Powell Butte, OR
3
Site
2694
2
Yes
Yes
not set
91002
Powell Butte, OR
2
Mfd
1394
2
No
No
35
91004
Bend, OR
3
Site
2663
2
Yes
No
not set
91005
Bend, OR
3
Site
2515
2
Yes
Yes
not set
91009
Redmond, OR
4
Site
1860
2
No
No
35
91010
Redmond, OR
4
Site
2660
2
No
No
35
6
Duct Leakage/Air Handler Data
Site ID
Both sides
Supply duct
duct leak to
leak to out
out at 50
at 50 Pa*
Pa*
(SCFM)
(SCFM)
Reference
Reference‡
‡
‡
Reference Air
supply
return static
Handler Flow
static
pressure
(CFM, SCFM)* pressure
(Pa)
(Pa)
91001
231***
151***
943, 1061
18
-84.5
91002
276
275
688, 774
16
-21
91004
n/a
n/a
889, 1000
21.5
-48
91005
273
131
924, 1040
26
-72.5
91009
329
208
1340, 1395
50
-139
91010
148
131
1271, 1430
116
-158
* Leakage and air handler flow results corrected to standard air (68°F and 1 atmosphere). The elevation of houses in
the Bend area (about 3,000 ft above sea level) results in lower air density. More specifically, the density is about 88.9%
of the density of standard air. The air handler flow values show both the local CFM and the standard SCFM.
‡ “Reference” airflow corresponds to the supply and return static pressure measurements shown in the table.
Typically this airflow represents the highest flow that could be attained using the User Interface (thermostat); this
measurement was taken to make sure the air handler was not working against an extreme external static pressure
(above 200 Pa) at its highest flow. No adverse static pressure conditions were found. All of these systems were set up
by the installer in COMFORT mode (so maximum flows typically average 325-350 CFM/nominal ton of capacity).
7
Airflow & Fan Power
Airflow (CFM)
1600
1400
1200
1000
800
600
400
200
0
y = 156.76x0.34
0
100
200
300 400 500
Fan Power (W)
600
700
800
• Site 91009
8
Air Handler Curves - All Sites
9
Balance Points (for 2 sites)
10
Heat Pump Balance Points
Site ID
91001
91002
91004
91005
91009
91010
Peak total UA† DHL base‡
(BTU/hr °F)
(BTU/hr)
896
283
1126
580
502
632
63,638
19,260
72,632
40,996
37,452
42593
DHL
w/DE††
(Btu/hr)
HP
Balance
Point
(°F)
97,122
26,814
72,632
69,719
72,367
66391
41
12
36
26
20
17
Heat
Pump
Size
(tons)
3
2
3
3
4
4
* All Design Heating Load (DHL) calculations based on 4° F design temperature.
†Shell plus infiltration heat loss at heating design temperature
‡Design Heating Load without duct losses at the design temperature
††Design Heating Load with duct losses included
11
Detailed Field Results
(834 monitored hours)
12
Capacity and COP Calculations
• Capacity determined by multiplying fitted
airflow by coil temperature split
• True RMS power is measured at the panel for
both indoor and outdoor units and converted
to Btu/hr
• COP is ratio of capacity to input power at a
given outdoor temperature
• Following 2 graphics do not include duct
losses
13
Performance vs Outdoor Temp (1)
(no duct effects included)
14
Performance vs Outdoor Temp (2)
(no duct effects included)
15
Measured Field Performance
(common five week period)
Site ID
Average
Outdoor
Temp. (F)
Total
Input
(kWh)
Total
Output
(kWh)
COP
(avg)
ER heat
output
fraction
Metered
Time Span
(hrs)
91001
38.4
716
1979
2.8
0.05
834
91002
39.3
277
627
2.3
0.09
834
91004
40.9
1185
2475
2.1
0.19
834
91005
39.4
861
1172
1.4
0.47
834
91009
38.2
662
1485
2.2
0.04
834
91010
37.3
706
1457
2.1
0.07
834
16
Compressor Response to Changing Heating Load
• Low compressor speed: input power < 1.25 x observed minimum input
• Medium compressor speed: anything in between low and high
• High compressor speed: input power > 0.87 x observed maximum input
17
Air Handler Response to Changing Heating Load
• Low fan speed: airflow < 1.25 x listed minimum airflow (comfort mode)
• Medium fan speed: anything in between low and high
• High fan speed: airflow > 0.87 x listed maximum airflow (comfort mode)
18
Operating Mode Summary
• Fan and compressor speeds track one another
– Given a compressor speed, there is a preferred fan speed
– High compressor outputs almost never pair with low and medium fan
– Low compressor speeds pair with both low and medium fan
• Runtime Fractions:
Compressor Only Operation
Fan Speed
Compressor
Speed
Low
Medium
High
Low
0.26
0.14
0.09
Medium
0.10
0.20
0.09
High
0.01
0.01
0.12
All
0.37
0.34
0.29
All
0.48
0.39
0.13
1.00
Compressor and Auxiliary Operation
Compressor
Speed
Low
Medium
High
All
Low
0.24
0.09
0.01
0.34
Fan Speed
Medium
High
0.12
0.08
0.18
0.09
0.01
0.18
0.31
0.35
All
0.45
0.36
0.19
1.00
19
Rolling in the Ducts…
20
Duct System Inputs
• Duct leakage, normalized to fraction of air handler
flow (which changes at different flows)
• Duct R-value
• Duct area
• Buffer space temperature (measured only for supply
buffer space)
• ASHRAE 152 used to calculate distribution efficiency
𝐷𝐸 = 𝛼𝑠𝑢𝑝𝑝𝑙𝑦 𝛽𝑠𝑢𝑝𝑝𝑙𝑦 − 𝛼𝑠𝑢𝑝𝑝𝑙𝑦 𝛽𝑠𝑢𝑝𝑝𝑙𝑦 1 − 𝛽𝑟𝑒𝑡𝑢𝑟𝑛 𝛼𝑟𝑒𝑡𝑢𝑟𝑛
𝛥𝑡𝑠𝑢𝑝𝑝𝑙𝑦
𝛥𝑡𝑟𝑒𝑡𝑢𝑟𝑛
− 𝛼𝑠𝑢𝑝𝑝𝑙𝑦 (1 − 𝛽𝑠𝑢𝑝𝑝𝑙𝑦 )
𝛥𝑡𝑠𝑦𝑠𝑡𝑒𝑚
𝛥𝑡𝑠𝑦𝑠𝑡𝑒𝑚
21
Average Duct Performance and Calculated
Duct Distribution Efficiency (DE)
(common five week period)
Site ID
Avg
Supply
System
Buffer
Airflow
Zone
(CFM) Temp (°F)
SLF
RLF
DE
91001
675
56.8
0.08
0.11
0.65
91002
550
55.2
0.13
0
0.82
91004
722
n/a
0
0
1.0
91005
766
55.9
0.07
0.17
0.61
91009
748
65.3
0.18
0.19
0.49
91010
1159
57.7
0.13
0.02
0.68
22
Modeling VHCPs – Annual Performance
• Annual performance estimated with SEEM
• Simulation largely unchanged from September
2012 RTF presentation
– Performance curve from catalogue data found to
work well enough for systems modeled
– Field study found that the operating modes pair
fan and compressor speed (previous default
assumption in simulation – remains unchanged)
23
Modeled VCHP and Duct System Efficiency
(using SEEM for entire heating season)
Equipment Efficiency
Site
Electric
Furnace,
COP=1
91001
91002
91004
91005
91009
91010
1.00
1.00
1.00
1.00
1.00
1.00
Single
Speed Heat
Pump,
HSPF=7.9
1.99
2.35
2.12
2.07
2.48
2.20
Average
1.00
2.20
Distribution System Efficiency
Variable
Speed Heat
Pump
Site
2.46
2.84
2.59
2.53
3.05
2.76
91001
91002
91004
91005
91009
91010
2.71
Average
Electric
Furnace,
COP=1
0.72
0.78
1.00
0.69
0.64
0.73
0.76
Single
Speed Heat
Pump,
HSPF=7.9
0.67
0.70
1.00
0.60
0.52
0.66
0.69
Variable
Speed Heat
Pump
0.66
0.72
1.00
0.59
0.52
0.64
0.69
Overall Efficiency
Site
91001
91002
91004
91005
91009
91010
Average
Electric
Furnace,
COP=1
0.72
0.78
1.00
0.69
0.64
0.73
0.76
Single
Speed Heat
Pump,
HSPF=7.9
1.33
1.63
2.12
1.23
1.28
1.45
1.51
Variable
Speed Heat
Pump
1.61
2.04
2.59
1.49
1.58
1.77
1.85
24
Lab (EPRI) vs Field Results
• Agreement on capacity and COP
measurements generally good; more
divergence for some cases
• Lab tests done in EFFICIENCY mode
• All sites in Oregon set up in COMFORT mode
• Lab showed higher COPs as expected because
of EFFICIENCY vs COMFORT mode
• Possibility of variability for individual pieces of
equipment, as well
25
Lab vs Field Comparison
(2 ton system)
Lab results
Field results
26
Overall Findings
• VCHP performs 25-30% better than a single
speed 7.9 HSPF heat pump on an annual basis
• Duct losses increased ~5% over a single speed
heat pump
• Overall system offers improved performance
over single speed base cases
• Heat pump sizing still matters
• Auxiliary heat lockout control still matters
27
Next Possible Steps
• Cost analysis. Collect data on installed costs
and compare to annual estimates of savings.
• More complete set of SEEM runs- additional
comparisons to base cases (HP and/or EFAF)
• Possible UES process (depends on cost
analysis)
• Further discussion of how system could be
commissioned (PTCS)
28