ASHRAE Headquarters GSHP vs. VRF ASHRAE Headquarters GSHP vs. VRF Jeffrey D. Spitler, Laura Southard,

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Text of ASHRAE Headquarters GSHP vs. VRF ASHRAE Headquarters GSHP vs. VRF Jeffrey D. Spitler, Laura...

  • ASHRAE Headquarters GSHP vs. VRF

    Jeffrey D. Spitler, Laura Southard, Oklahoma State University

    Xiaobing Liu, Oak Ridge National Laboratory

  • Project Team

    Jeff Spitler Xiaobing Liu Laura Southard

  • A living laboratory

    • Over 1000 measurement points

    • 2-story office building, built in 1965

    • Renovated and enlarged in 2007-2008

    • Open plan office design allows for more daylighting

    • Three systems: • Variable refrigerant flow system serving 1st floor

    • Ground source heat pump system serving 2nd floor

    • Dedicated outdoor air system serving both floors

  • First floor / VRF System

    • 17,213 ft2 (1599 m2) served by VRF system

    • Not served by metered VRF system: • Computer server room • Rear staircase • Entry foyer

    • Served: • Office space • Mailroom • Learning Center

    • Two outdoor heat-recovery units (28 tons nominal capacity)

    • 22 indoor FCU

  • VRF Controls

    • Single setpoint.

    • Users can reset thermostats ±3°F

    • System attempts to maintain setpoint, within ±1°F

    • Individual units do not switch back and forth between heating and cooling, though.

    • Adjacent units in open floor plan office do run in opposite modes.

  • Second Floor / GSHP System

    • GSHP serves entire 2nd floor + rear stairwell.

    • Total floor area 15,558 ft2. (1445 m2)

    • Office space and two conference rooms.

  • GSHP System

    • 12 boreholes, 400 ft. deep

    • 14 water-to-air heat pumps, 31.5 tons nominal capacity

    • Heat pumps: • Two-stage • ECM fan motors, variable speed

    • Staged controls: • Separate heating/cooling setpoints 68°F/74°F typical • Temperature deviates > 1.5°F: low-stage • Temperature deviates > 2.5°F: high-stage • Users can reset thermostats ±3°F

  • DOAS

    • Provides partly conditioned ODA to both floors.

    • Generally, always lower than room temperature.

    • Sometimes overcools.

    • Increases heating loads, decreases cooling loads.

  • Qualitative comparison of loads

    • 1st floor and 2nd floor: same lighting and plug load densities.

    • Occupancy: • 1st floor (normal): 400 ft2/person

    • 2nd floor (normal): 259 ft2/person

    • 1st floor, learning center: used ~26 hours/month

    • DOAS average flow rate: • 1st floor: 2560 CFM

    • 2nd floor: 1480 CFM

  • Qualitative comparison of loads

    • Rooms on 2nd floor have heat gains from roof.

    • 1st floor has more glass façade, but part of this is conditioned by non-metered VRF systems.

    • As a result: • 1st floor has higher heating loads.

    • 2nd floor has higher cooling loads.

    • Cooling loads are much higher than heating loads.

  • Results

    • Energy consumption

    • Heating and Cooling Loads

    • System COP and EER

    • Why?

  • Total Monthly Energy Use

    0

    2,000

    4,000

    6,000

    8,000

    10,000

    12,000

    14,000

    16,000

    18,000

    20,000

    M o

    n th

    ly E

    n e

    rg y

    U se

    , k W

    h

    GSHP VRF DOAS

  • Monthly Energy Use per ft2

    0.00

    0.05

    0.10

    0.15

    0.20

    0.25

    0.30

    0.35

    M o

    n th

    ly E

    n e

    rg y

    U se

    , k W

    h /f

    t2

    GSHP VRF

  • Avg. Power vs. Outdoor Temperature

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    1.2

    1.4

    1.6

    1.8

    2.0

    15 35 55 75 95

    A ve

    ra ge

    P o

    w e

    r U

    se , W

    /f t2

    Ambient Dry Bulb Temperature, °F

    GSHP VRF DOAS

  • 0

    100

    200

    300

    400

    500

    600

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    800

    900

    1000 1

    4

    1 8

    2 2

    2 6

    3 0

    3 4

    3 8

    4 2

    4 6

    5 0

    5 4

    5 8

    6 2

    6 6

    7 0

    7 4

    7 8

    8 2

    8 6

    9 0

    9 4

    9 8

    1 0

    2

    N u

    m b

    er o

    f h

    o u

    rs

    Temperature (°F)

    July 2011 - June 2013 Temperatures

  • VRF Heating and Cooling

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    1.2

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    1.6

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    2.0

    17 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

    A ve

    ra ge

    V R

    F P

    o w

    e r

    U se

    , W /f

    t2

    Ambient Dry Bulb Temperature, °F

    VRF Heating Cooling

  • GSHP Heating and Cooling

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    1.2

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    1.6

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    2.0

    17 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

    A ve

    ra ge

    G SH

    P P

    o w

    e r

    U se

    , W /f

    t2

    Ambient Dry Bulb Temperature, °F

    GSHP

    Heating Cooling Unallocated

  • Avg. Power – Cooling Only

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    1.2

    1.4

    1.6

    1.8

    2.0

    15 35 55 75 95

    A ve

    ra ge

    P o

    w e

    r U

    se , W

    /f t2

    Ambient Dry Bulb Temperature, °F

    GSHP VRF

  • Avg. Power – Heating Only

    0.0

    0.2

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    1.0

    1.2

    1.4

    1.6

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    15 35 55 75 95

    A ve

    ra ge

    P o

    w e

    r U

    se , W

    /f t2

    Ambient Dry Bulb Temperature, °F

    GSHP VRF

  • A moderate day

    April 3, 2013 Morning low: 43°F Afternoon high: 63°F

  • Power Use

    0.0

    0.2

    0.4

    0.6

    0.8

    1.0

    1.2

    0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00

    W /f

    t2

    VRF GSHP

  • GSHP Zone Temperatures

    69

    70

    71

    72

    73

    74

    75

    76

    7:00 10:00 13:00 16:00 19:00

    Zo n

    e T

    e m

    p e

    ra tu

    re , °

    F

    Zone 207 Zone 204

    Zone 209 Zone 224C

    Zone 224D Zone 206

    Zone 215A Zone 215B

    Zone 215C Zone 224B

  • VRF Zone Temperatures (Cooling)

    69

    70

    71

    72

    73

    74

    75

    76

    77

    7:00 10:00 13:00 16:00 19:00

    Zo n

    e T

    e m

    p e

    ra tu

    re , °

    F

    Zone 116 Zone 117 Zone 119

    Zone 120 Zone 134B Zone 134C

    Zone 134D

    Adjacent zone was heating

  • VRF Zone Temperatures (Heating)

    69

    70

    71

    72

    73

    74

    75

    76

    77

    7:00 10:00 13:00 16:00 19:00

    Zo n

    e T

    e m

    p e

    ra tu

    re , °

    F

    Zone 103 Zone 104 Zone 105

    Zone 109 Zone 110 Zone 111

    Zone 112 Zone 134A Zone 139

    Zone 140A Zone 140B Zone 140C

    Zone 145 Zone 147

  • Why is GSHP so much better?

    • Source temperatures.

    • Equipment efficiency at actual source temperatures.

    • Apparent control issue – most VRF units run most of the time under moderate load conditions.

    • Unnecessary (?) simultaneous heating and cooling.

    • Loads are different. (Yes, but how much?)

  • Source Temperatures

    0

    20

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    7/1/11 12/31/11 7/1/12 12/31/12 7/2/13

    Te m

    p e

    ra tu

    re , °

    F

    Ambient air Ground Loop Water Supply

  • Heating and cooling provided

    • How much heating and cooling are provided by each system?

    • Heat pumps and 14 VRF FCUs:

    • Need air flow rate + temperatures and (for cooling) humidities.

  • Actual Available Measurements

    • Airflow – from flow hood measurements (VRF system changed control boards and flows in April 2012)

    • Discharge air temperature

    • Zone air temperature

    • Zone air humidity

  • Estimated quantities

    • Entering and discharge air humidities • GSHP system, from measurements in one zone

    • VRF system, from mfr. data, SHF=f(EAT, ODAT); spot-checked by us

    0.000

    0.002

    0.004

    0.006

    0.008

    0.010

    0.012

    0.014

    0.016

    0.018

    0.000 0.005 0.010 0.015 0.020

    En te

    ri n

    g ai

    r h

    u m

    id it

    y ra

    ti o

    Zone humidity ratio

    without DOAS with DOAS 1:1 line

    0.000

    0.002

    0.004

    0.006

    0.008

    0.010

    0.012

    0.014

    41 50 59 68

    D is

    ch ar

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