BONNEVILLEPOWERADMINISTRATION
VRF Energy Modeling Savings Estimates
Regional Technical Forum Variable Capacity
Heat Pump Sub-Committee Meeting
August 31, 2011
Energy Solutions
BONNEVILLEPOWERADMINISTRATION
Outline
• Requested Analysis
• Modeling Parameters
• Assumptions
• Results
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BONNEVILLEPOWERADMINISTRATION
Requested Analysis
• Model VRF energy savings for buildings in Seattle
and Spokane using EnergyPro 5
• Based on SCE analysis
• Mitsubishi VRF heat pump and heat recovery systems
• Small office
• 7,200 sf
• Medium office
• 41,500 sf
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BONNEVILLEPOWERADMINISTRATION
Baseline Systems
• Small office
• Packaged rooftop air conditioner with gas furnace and
constant volume fan
• ASHRAE system type 3
• 4 units, 6-8 tons each, fixed temp economizer, 1080 cfm of OSA
• Modeling software included conductive duct losses for electric
cooling
• Fan energy increased to compensate for duct leakage
• Packaged rooftop heat pump and constant volume fan
• ASHRAE system type 4
• 4 units, 6-8 tons each, fixed temp economizer, 1080 cfm of OSA
• Modeling software included conductive duct losses for both
electric cooling and heating
• Fan energy increased to compensate for duct leakage
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BONNEVILLEPOWERADMINISTRATION
Baseline Systems
• Medium office
• Packaged rooftop VAV with gas boiler reheat
• ASHRAE system type 5
• 6 units, 19-26 tons each, fixed temp economizer, 6015 cfm of
OSA
• Increased electric cooling energy to compensate for conductive
duct losses
• Fan energy increased to compensate for duct leakage
• Packaged rooftop VAV with electric resistance reheat
• ASHRAE system type 6
• 6 units, 19-26 tons each, fixed temp economizer, 6015 cfm of
OSA
• Increased electric cooling energy to compensate for conductive
duct losses
• Fan energy increased to compensate for duct leakage
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BONNEVILLEPOWERADMINISTRATION
VRF Systems
• Small office
• VRF heat pump system with DOAS
• 2 units, 10 to 12 tons each, no economizer, 1080 cfm of OSA
• VRF heat recovery system with DOAS
• 2 units, 10 to 12 tons each, no economizer, 1080 cfm of OSA
• Medium office
• VRF heat pump system with DOAS
• 6 units, 12 to 16 tons each, no economizer, 6015 cfm of OSA
• VRF heat recovery system with DOAS
• 6 units, 12 to 16 tons each, no economizer, 6015 cfm of OSA
• No duct conductive losses or leakage
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BONNEVILLEPOWERADMINISTRATION
Modeling Parameters
• ASHRAE 90.1 - 2007 Baseline
•
Small office – Packaged RTU w/ gas heat or heat pump
•
•
•
•
•
Separate baseline models created using 90.1 parameters
Base case had 4 total zones and 4 rooftop units
VRFs were modeled with 8 zones and 2 outdoor units
Baseline equipment was modeled on typical sizes, VRFs were
based on actual Mitsubishi equipment in EnergyPro
Medium office – VAV w/ boiler or electric reheat
• Used standard VAV energy models auto-generated by EnergyPro
for the VRF simulation baselines
• Program assigned the same number of VAV air handlers as VRF
outdoor units – 6 total; more AHUs than normal for capacity
• Baseline VAV capacities were sized by EnergyPro to satisfy peak
block loads for assigned zones; capacities did not fall into typical
VAV size categories
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BONNEVILLEPOWERADMINISTRATION
Modeling Parameters
• Energy savings
• Baseline energy use: cooling, electric heating, fans, and
pumps
• VRF and DOAS system energy use: cooling, heating, fans,
and branch selector boxes
• Peak demand analysis
• Evaluated summer and winter, comparing total building
peak demand between measure and base
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BONNEVILLEPOWERADMINISTRATION
Assumptions
• 28% increase in electric heating and cooling energy
to account for duct losses1
• Not included for VAV electric reheat
• 37% increase in fan energy due to air leakage from
ducts2
1. Fisk, William J, et al., Duct systems in large commercial buildings: physical characterization, air leakage, and heat conduction
gains, LBNL-42339, page 110, November 1999
2. Diamond, Rick, et al., Thermal Distribution Systems in Commercial Buildings, LBNL-51860, page 12, May2003
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BONNEVILLEPOWERADMINISTRATION
Energy Usage – Small Office
VRF Heat Pump
Seattle
Spokane
Cooling (kWh)
8,959
9,712
Heating (kWh)
5,164
11,338
Fans (kWh)
5,195
5,865
Total (kWh)
19,318
26,915
Cooling (kWh)
9,511
10,283
Heating (kWh)
5,498
12,219
Fans (kWh)
5,195
5,865
Branch Box (kWh)
310
303
Cooling (kWh)
5,158
8,308
Heating (therms)
339
913
Fans (kWh)
46,366
46,953
Total (kWh)
51,524
55,261
Cooling (kWh)
5,158
8,308
Heating (kWh)
4,108
13,213
Fans (kWh)
46,364
46,932
Total (kWh)
55,630
68,453
VRF Heat Recovery
Seattle
Spokane
Total (kWh)
20,514
28,670
RTU Gas Furnace
Seattle
Spokane
RTU Heat Pump
Seattle
Spokane
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BONNEVILLEPOWERADMINISTRATION
Energy Usage – Medium Office
VRF Heat Pump
Seattle
Spokane
Cooling (kWh)
52,759
55,515
Heating (kWh)
17,252
34,124
Fans (kWh)
22,320
24,510
Total (kWh)
92,331
114,149
Cooling (kWh)
53,069
52,075
Heating (kWh)
9,439
29,633
Fans (kWh)
22,320
24,510
Branch Box (kWh)
1,956
1,917
Total (kWh)
86,784
108,135
Cooling (kWh)
87,880
89,446
Heating (therms)
3,400
4,938
Fans (kWh)
53,437
61,871
Pumps (kWh)
618
902
Total (kWh)
141,935
152,219
Cooling (kWh)
85,708
86,970
Heating (kWh)
58,628
84,725
Fans (kWh)
52,853
60,665
Total (kWh)
197,189
232,360
VRF Heat Recovery
Seattle
Spokane
VAV Gas Boiler Reheat
Seattle
Spokane
VAV Electric Reheat
Seattle
Spokane
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BONNEVILLEPOWERADMINISTRATION
Results – Small Office
VRF Heat Pump
Packaged RTU w/ Gas Heat Base Case - ASHRAE system type 3
Packaged RTU Heat Pump Base Case - ASHRAE system type 4
Normalized
Savings
(kWh/SF)
Savings
(kWh/ton)
Demand
Reduction
(kW/ton)
Gas Heat
Offset
(therms)
Normalized
Savings
(kWh/SF)
Savings
(kWh/ton)
Demand
Reduction (summ)
(kW/ton)
Demand
Reduction (wint)
(kW/ton)
Seattle
4.47
1464
0.45
339
5.04
1651
0.45
0.45
Spokane
3.94
1288
0.45
913
5.77
1888
0.45
1.95
Average
4.20
1376
0.45
626
5.41
1769
0.45
1.20
VRF Heat Recovery
Packaged RTU w/ Gas Heat Base Case - ASHRAE system type 3
Packaged RTU Heat Pump Base Case - ASHRAE system type 4
Normalized
Savings
(kWh/SF)
Savings
(kWh/ton)
Demand
Reduction
(kW/ton)
Gas Heat
Offset
(therms)
Normalized
Savings
(kWh/SF)
Savings
(kWh/ton)
Demand
Reduction (summ)
(kW/ton)
Demand
Reduction (wint)
(kW/ton)
Seattle
4.31
1410
0.45
339
4.88
1596
0.45
0.45
Spokane
3.69
1209
0.41
913
5.53
1808
0.41
1.91
Average
4.00
1309
0.43
626
5.20
1702
0.43
1.18
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BONNEVILLEPOWERADMINISTRATION
Results – Medium Office
VRF Heat Pump
VAV w/ Gas Boiler Reheat Base Case - ASHRAE system type 5
VAV w/ Electric Reheat Base Case - ASHRAE system type 6
Normalized
Savings
(kWh/SF)
Savings
(kWh/ton)
Demand
Reduction
(kW/ton)
Gas Heat
Offset
(therms)
Normalized
Savings
(kWh/SF)
Savings
(kWh/ton)
Demand
Reduction (summ)
(kW/ton)
Demand
Reduction (wint)
(kW/ton)
Seattle
1.20
620
0.44
3400
2.53
1311
0.43
0.70
Spokane
0.92
453
0.61
4938
2.85
1407
0.58
0.87
Average
1.06
537
0.52
4169
2.69
1359
0.50
0.78
VRF Heat Recovery
VAV w/ Gas Boiler Reheat Base Case - ASHRAE system type 5
VAV w/ Electric Reheat Base Case - ASHRAE system type 6
Normalized
Savings
(kWh/SF)
Savings
(kWh/ton)
Demand
Reduction
(kW/ton)
Gas Heat
Offset
(therms)
Normalized
Savings
(kWh/SF)
Savings
(kWh/ton)
Demand
Reduction (summ)
(kW/ton)
Demand
Reduction (wint)
(kW/ton)
Seattle
1.33
689
0.41
3400
2.66
1380
0.39
0.81
Spokane
1.06
525
0.58
4938
2.99
1479
0.56
0.89
Average
1.20
607
0.50
4169
2.83
1429
0.47
0.85
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BONNEVILLEPOWERADMINISTRATION
Savings Summary
VRF Heat Pump
% Electricity Savings over Baseline with Gas Heat
% Electricity Savings over Baseline with Electric Heat
Medium Office
Small Office
Medium Office
Small Office
Seattle
34.9%
62.5%
31.5%
65.3%
Spokane
25.0%
51.3%
42.5%
60.7%
Average
30.0%
56.9%
37.0%
63.0%
VRF Heat Recovery
% Electricity Savings over Baseline with Gas Heat
% Electricity Savings over Baseline with Electric Heat
Medium Office
Small Office
Medium Office
Small Office
Seattle
38.9%
60.2%
33.2%
63.1%
Spokane
29.0%
48.1%
44.7%
58.1%
Average
33.9%
54.2%
38.9%
60.6%
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