Variable Capacity Heat Pump RTF Sub-Committee November 16 , 2011

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B O N N E V I L L E P O W E R A D M I N I S T R A T I O N

Variable Capacity Heat Pump RTF Sub-CommitteeNovember 16, 2011

Mira Vowles, P.E., CEM Emerging Technology Project ManagerBPA Energy Efficiency

Slide 2


Meeting Agenda

1. EnergyPro Correction

2. Small Office Baseline Model Differences

3. Small Office VRF Heat Pump Model Differences

4. VRF Model Best Practice

5. Revised Definitions

If we have time:

– Discuss M&V best practice & standard protocol

– Discuss compiling list of PNW VRF installations

Slide 3


Seattle Small Office Energy Use Correction

SEATTLE Energy Solutions Small Office

RTU

(kWh/SF) RTU (%)VRF

(kWh/SF) VRF (%)

Fan (kWh/SF) 6.4 73% 0.7 27%

Cooling (kWh/SF) 1.0* 11% 1.2 46%

Electric (kWh/SF) 7.4 84% 1.9 73%

Heat (kBtu/SF) 4.7 16% 2.4 27%

Total (kBtu/SF) 29.9 100% 8.9 100%

* Corrected to include duct loss adjustment

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Energy Solutions Small Office Model 7,200 square foot office modeled using EnergyPro 5

• Baseline: Packaged rooftop air conditioner with gas furnace and constant volume fan• ASHRAE system type 3• 4 units, 6-8 tons each, fixed temp economizer,

1,080 cfm of OSA• Included 28% cooling increase to account for

conductive duct losses• Included 37% fan energy increase to

compensate for duct leakage

• VRF heat pump system with DOAS• 2 Mitsubishi units, 10 to 12 tons each, no

economizer, 1,080 cfm of OSA

Slide 5


Energy Solutions & PECI Small Office RTU Gas-Pack Model Differences

1. Energy Solutions used EnergyPro and PECI used eQuest

2. Energy Solutions included significant Baseline duct losses

3. PECI included two-speed fans (fan at 35% when no heating or cooling loads)

4. PECI included server room which requires minimal heating

Slide 6


Energy Solutions & PECI Small Office VRF Heat Pump Model Differences

1. Energy Solutions used EnergyPro Mitsubishi VRF performance modules

2. PECI used the eQuest “BSUG method” (PVVT model with compressor VSD and post processing heat recovery analysis)

3. PECI’s model doesn’t include refrigerant pipe losses

4. PECI included ventilation fan with 2.5” static pressure, while Energy Solutions used DOAS with unknown static pressure

Slide 7


Seattle RTU Fan Energy Use Summary

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SEATTLE RTU Gas-Pack Modeled HVAC Breakdown Comparison

0.0

10.0

20.0

30.0

40.0

Fan Cooling Heat Total

kB

TU

/SF

PECI eQuest Model Energy Sol'ns EnergyPro Model

Small Office RTU Gas-Pack Modeled HVAC Energy Use Comparison

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SEATTLE RTU Gas-Pack Modeled HVAC Breakdown Comparison

0%

20%

40%

60%

80%

Fan Cooling Heat


Small Office RTU Gas-Pack Modeled HVAC % Use Comparison

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Small Office VRF HP Modeled HVAC Energy Use Comparison

SEATTLE VRF Heat Pump Modeled HVAC Breakdown

0.71.1

0.5

2.3

0.7

1.2

0.7

2.6

0.0

0.5

1.0

1.5

2.0

2.5

3.0


kW

h/S

F


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Small Office VRF HP Modeled HVAC % Use Comparison

SEATTLE VRF Heat Pump Modeled % HVAC Breakdown

0%20%40%60%80%

100%120%



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Building Simulation Program Issues Due to the complexity of VRF systems (both VRF HR and

VRF HP), building simulation programs are needed to estimate site-specific savings;

How can the accuracy of the building simulation programs be verified?

What are the important metrics?

Monthly energy use and average monthly temperature

Other?

Can building simulation programs provide these important metrics for verification purposes?

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VC HP Building Simulation Model Best Practices

– EnergyPro

– TRACE

– eQuest

– Other?

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Modeling VC HP with TRACE TRACE can explicitly model VC HP, both heat pump and heat

recovery systems:

– Algorithms are based on Daikin empirical model

– Inputs based on first generation Daikin VRV equipment • modify to match current generation equipment or other manufacturer

• Heating COP or Cooling KW/ton

• Condensing Fan power consumption KW/ton

• Select unloading curve, compressor power consumption curve, condensing fan curve and cycling point as appropriate

Based on April 15, 2009 BSUG meeting presentation

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Modeling VC HP with TRACE continued

TRACE airside simulation• When space temperature rises above the cooling setpoint, the cooling

coil supplies air at a constant, cooling-supply-air-temperature until the setpoint is met; rejected heat is supplied to the refrigerant condenser loop.

• When space temperature drops below the heating setpoint, the heating coil supplies air at a constant, heating-supply-air-temperature until the setpoint is met, and the heat is removed from the refrigerant condenser loop. The default minimum reheat is 10%, or it can be entered on a room by room basis.

• When the heating and cooling coils are inactive, the minimum supply airflow at the mixed-air temperature is assumed; fan heat is , included.


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Modeling VC HP with eQUEST Model as PVVT Water Source Heat Pump system • Zone the building in the same manner as the design for representative

heat recovery modeling

• Select a water cooled condenser with a condenser water loop

• Create one system per zone

• Create separate condenser water loops for each VRF condenser and zero out the pump energy

• Change the fan efficiency ratio and electric boiler EIR to reflect VRF efficiencies


Slide 17


Modeling VC HP with eQUEST continued

Model as PVVT Air Cooled Heat Pump

• Create one system per zone

• Change to variable compressor speed

• Label systems and zones to according to which condenser each zone is connected to

• Create hourly reports with total heating and cooling energy use for each system

• Use spreadsheet to find simultaneous heating and cooling for each system, and sum the savings

– This methodology is felt to be a conservative approach, which has been accepted by the USGBC on the Portland Mercy Corp LEED building

– DOE-2 VRF system curves need to be developed


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How Accurate are Baseline and VC HP Models?

– PNW EUI’s

– EnergyPro EUI’s

– eQuest EUI’s

– How can we verify model accuracy?

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Slide 20


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Small Office Baseline EUI Comparison

Whole building Mean EUI = 75 (kBtu/SF), with a Standard Deviation of 13 (kBtu/SF)

83 8477

57

0

10

20

30

40

50

60

70

80

90

EUI (kBtu/SF)

Energy Solutions(EnergyPro -Seattle)

2007 CBSA

2003 CBECs

PECI (eQuest)

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Medium Office Baseline EUI Comparison


41

74

106

52.963

0

20

40

60

80

100

120

EUI (kBtu/SF)

Energy Solutions(EnergyPro -Seattle)

2007 CBSA

2003 CBECs

PECI (eQuest)

Mitsubishi (EnergyPro -Seattle)

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Small Office VRF HP & Getting to Fifty EUI Comparison


63

32

46

52.9

0

10

20

30

40

50

60

70

EUI (kBtu/SF)

Energy Solutions(EnergyPro)

PNW GT50 Low (NBI)

PNW GT50 High (NBI)

PECI (eQuest)

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Small Office VRF HPHVAC EUI Comparison

HVAC EUI Mean = 9 (kBtu/SF), with a Standard Deviation of 1 (kBtu/SF)

9.2

8.0

7.4

7.6

7.8

8.0

8.2

8.4

8.6

8.8

9.0

9.2

9.4

HVAC EUI (kBtu/SF)


PECI (eQuest)

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Medium Office VRF EUI Comparison

Whole Building EUI Mean = 43 (kBtu/SF), with a Standard Deviation of 8 (kBtu/SF)

34

47

54

39

0

10

20

30

40

50

60

EUI (kBtu/SF)


GT50 Ave (NBI)

Mitsubishi (EnergyPro)

PECI (eQuest)

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Small Office VRF Savings Comparison

21.0

4.2

0.0

5.0

10.0

15.0

20.0

25.0

savings EUI (kBtu/SF)


PECI (eQuest)

Savings EUI Mean = 13 (kBtu/SF), with a Standard Deviation of 12 (kBtu/SF)

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Medium Office VRF Savings Comparison

Savings EUI Mean = 11 (kBtu/SF), with a Standard Deviation of 3 (kBtu/SF)

8.9

13.6

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

savings EUI (kBtu/SF)


PECI (eQuest)

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Office Building Definition A building used primarily for office functions, including

desk-work, reading and light equipment (computer, copier, printer, telephone, etc.) use.

Office occupancies are further defined by

overall occupant densities between 50 and 300 square feet per person,

overall lighting power densities up to 1 watt per square foot, and

overall equipment plug loads up to 1.5 watts per square foot.

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VRF System DefinitionVariable refrigerant flow (VRF) systems, either heat-pump or heat-

recovery styles, providing heating and air-conditioning, and typically consisting of:

1. Outdoor unit(s) with inverter driven compressor(s) and condenser fan providing improved part-load and low-ambient performance,

2. Multiple indoor units with multi-speed fans, electronic expansion devices, integrated zone temperature controllers and no electric resistance heating capacity,

3. Refrigerant piping between the outdoor and indoor units,

5. Ventilation provided by either natural ventilation or a dedicated outside air system (DOAS).

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VRF System M&V Best Practice?

– Meter baseline and VRF system electricity use for representative period, project to annual savings

– Use calibrated Building Simulation model to predict annual savings and monthly electricity use

– Verify savings by comparing actual monthly electricity use to predicted monthly electricity use

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VRF System M&V Standard Protocol?

– Use whole building regression analysis spreadsheet with representative period pre- and post- monthly electricity billing data and hourly average OSA temperature,

– if savings are temperature dependant, over 15% of whole building electricity use and there are no other significant changes to electricity use, the whole building regression analysis spreadsheet can provide an 80-20 confidence interval for savings

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Small Office Monthly Electricity Use and Savings

0

5,000

10,000

15,000

20,000

25,000

30,000

(kW

h)

Monthly Savings (kWh)

Proposed (kWh)

Adj Baseline (kWh)

Based on Energy Solutions EnergyPro model

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Based on Energy Solutions EnergyPro model

Percent Monthly Electricity Savings

21%

27%

33% 32% 30% 31% 32% 33%31% 31%

28%25%

0%

5%

10%

15%

20%

25%

30%

35%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

(%)

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Use Whole Building Analysis for VRF ROB Electricity Savings M&V?

– Energy Solutions EnergyPro model predicts monthly electricity savings ranging between 21 and 33%

– For the Small Office (7,200 SF) the monthly electricity savings ranging between 1,900 and 2,200 kWh

Next Step: use whole building regression analysis spreadsheet, using EnergyPro model predicted monthly electricity use and Seattle hourly average OSA temperature

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Next Meeting

– Scheduled for 12/21/11 at 9 am

– Move to 12/14/11 at 9 am?

Potential Topics:

– Compare actual RTU annual fan kWh/SF to models

– Develop VRF savings estimates (IEER plus fan?)

– Compile list of PNW VRF installations & brainstorm how to “mine” for useful information

– Develop M&V best practice and standard protocol

– Develop research plan to verify model accuracy

– NEEA RTU Replacement Discussion

Documents

Variable Capacity Heat Pump RTF Sub-Committee November 16 , 2011