Reduction in Vehicle Temperatures and Fuel Use from

Cabin Ventilation, Solar-Reflective Paint, and a New Solar-Reflective

GlazingJohn P. Rugh, Lawrence Chaney, Jason Lustbader

National Renewable Energy LaboratoryJohn Meyer - VisteonMukesh Rustagi, Kurt Olson - PPG IndustriesRupert Kogler - Webasto AG

2 2007-01-1194

OutlineImproved Mobile Air Conditioning Cooperative Research ProgramVehicle Thermal Soak TestThermal and Vehicle Fuel Use Analysis

3 2007-01-1194

Improved Mobile Air Conditioning Cooperative Research Program

Demonstrate technologies to reduce direct (leakage) and indirect (tailpipe) HFC-134a refrigerant emissionsGovernment/Industry partnership28 Industry SponsorsAdministered by Society of Automotive Engineers (SAE)Four Teams

Reduce leakage during operationImproved COPReduce vehicle thermal loadReduce leakage during service

4 2007-01-1194

2006 I-MAC Reduced Thermal Load Vehicle

Select the most promising technologies and test in a final configuration

Solar Powered Parked Car Ventilation

Solar Reflective Glazings

Solar Reflective Paint

5 2007-01-1194

Solar Reflective Glazings: Sungate EPManufacturer: PPG IndustriesReflects IR portion of solar spectrum

Meets 70 % transmittance requirementGreater than 50% solar energy reflected

Reduces solar heat gainWindshield, sidelites, backlite

Solargreen® glass

Sungate® windshield

Sungate® EP

LTa 72% 72 71

TSET 44% 39 33

TSER 6% 31 47

6 2007-01-1194

Solar Powered Parked Car Ventilation

Manufacturer: Webasto24 cell, 17 W PV panel in sunroofSix ~ 1.6 W fansCurrent configuration: Extracts hot air from cabin interiorSince STS already had a sunroof, a unique test install was required

7 2007-01-1194

Solar Reflective Paint

Manufacturer: PPG IndustriesPrototype S2XMaintains color while reflecting IR portion of solar spectrumStandard clearcoat over IR reflective basecoatCooler skin temperatures reduce cabin heat gainNREL measured absorptance

Baseline 89.4%Solar reflective 82.1%

8 2007-01-1194

I-MAC Vehicle Soak Test Procedure

Two nearly identical vehicles parked facing 160º, front/backEvaluate technologies that reduce thermal load

Modify test vehicleStart data acquisition system ~ 8:30 amStop data acquisition system ~ 16:30 am

Data analysisReport time-averaged temperature difference between identical locations between 12:30 and 13:30Eliminate cloudy daysAverage results with multiple “good” test days

9 2007-01-1194

Cadillac STS & NREL Test Facility

Modified

Baseline

10 2007-01-1194

Reduction in Air TemperaturesSolar reflective glazings all locationsSolar powered ventilationSolar reflective paint

20

25

30

35

40

45

50

55

60

65

70

9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00Time

Tem

pera

ture

(o C

)

68

77

86

95

104

113

122

131

140

149

158

Tem

pera

ture

(o F)

air foot baselineair foot modifiedair breath baselineair breath modifiedair baselineair modifiedAmbient airSeries3

Breath

Average

Foot

Ambient air

11 2007-01-1194

Solar Reflective Glass (All Locations), Paint, and Ventilation

5.6

12.0

8.8

16.8

6.0

10.3

11.9

20.4

0

5

10

15

20

25

Air-Foot Air-Breath Air Dashboard Roof Exterior Front DriverSeat

Front PassSeat

Windshield

Red

uctio

n in

Tem

pera

ture

(o C)

0

9

18

27

36

45

Red

uctio

n in

Tem

pera

ture

(o F)

12 2007-01-1194

0

5

10

15

20

25

Air-Foot Air-Breath Air Dashboard Roof Exterior Front DriverSeat

Front PassSeat

Windshield

Red

uctio

n in

Tem

pera

ture

(o C)

0

9

18

27

36

45

Red

uctio

n in

Tem

pera

ture

(o F)

Solar Reflective Glass-all locations, Parked Car VentilationSolar Reflective Glass-all locationsSolar Reflective Windshield-BackliteSolar Reflective Windshield

Solar Reflective Paint-all tests

Comparison to Solar Reflective Glass only Data

13 2007-01-1194

Solar Powered Ventilation Only

-2.9

7.1

2.1

6.2

1.5

0.70.3

2.3

3.0

8.3

5.6

8.3

1.0

6.0

5.3

2.3

-4

-2

0

2

4

6

8

10

Air-Foot Air-Breath Air Dashboard Roof Exterior Front DriverSeat

Front PassSeat

Windshield

Red

uctio

n in

Tem

pera

ture

(o C)

Air blown into vehicleAir pulled out of vehicle

14 2007-01-1194

Solar Reflective Roof Film Only

0.5

1.20.8 0.9

6.7

0.4 0.4

-0.6-1

0

1

2

3

4

5

6

7

8

Air-Foot Air-Breath Air Dashboard Roof Exterior Front DriverSeat

Front PassSeat

Windshield

Red

uctio

n in

Tem

pera

ture

( o C

)

15 2007-01-1194

Integrated ModelingAssessing the impact of Assessing the impact of advanced climate control advanced climate control

systems on vehicle fuel use systems on vehicle fuel use and human thermal comfort and human thermal comfort

in a Cadillac STSin a Cadillac STSCAD

RadTherm

ThermalComfort

AirConditioning

Cabin Thermal/Fluid

Vehicle

FuelEconomy

TailpipeEmissions

OccupantThermal Comfort

16 2007-01-1194

Model temperatures Model temperatures and airflow in the cabinIntegrated Modeling and airflow in the cabin

CAD

RadTherm

ThermalComfort

AirConditioning

Cabin Thermal/Fluid

Vehicle

FuelEconomy

TailpipeEmissions

OccupantThermal Comfort

17 2007-01-1194

Baseline Soak Results Comparison to Test Data

30

40

50

60

70

80

90

IP Left

IP right

Dr sea

t

Pa Sea

twindsh

ield

Backli

ghtDr s

ide light

Pa side l

ight

Pkg Shelf

Headlin

er

air fo

ot

air brea

thDataSimulation

-0.8

+1.4

+2.2

+7.2

-1.5

-2.6

+2.2

+1.7

-9.8

+7.0

+0.8

-2.9

18 2007-01-1194

Soak Results Temperature Contours

Baseline Reduced Thermal LoadSolar Reflective Glazings

Solar Reflective PaintSolar Powered Parked Car Ventilation

19 2007-01-1194

Simplified Thermal ModelRadTherm Fluent

136,000 Elements Full CFD model 900,000 Fluid Nodes

136,000 Elements Simplified model 8 Fluid Nodes

20 2007-01-1194

25

35

45

55

65

75

85

0 5 10 15 20 25 30 35 40 45

Time (Minutes)

Tem

pera

ture

(o C)

Driver Seat (Simulation)Driver Seat (Data)Pass. Seat (Simulation)Pass. Seat (Data)

Driver Seat

Pass. Seat

Baseline Cool Down Results

21 2007-01-1194

Adjust A/C Load in RadTherm to Achieve Equal 30 min. Cooldown

30

35

40

45

50

55

60

0 5 10 15 20 25 30

Minutes

Mas

s A

vera

ge T

empe

ratu

re (o C

)

Baseline (5.7kW)Reduced Thermal Load (4.0 kW)

30% Reduction in cooling load

22 2007-01-1194

30 minute cool down• Heat Balance:

• Balanced with:Baseline – 5.7 kW cooling

Reduced Thermal Load – 4.0 kW cooling

• 29.8% Reduction in cooling load

∑∑∑∑=

=

=

=

=

=⎟⎠⎞

⎜⎝⎛ ∆=∆−∆−⎟

⎠⎞

⎜⎝⎛ ∆

30

0 Re,

.30

0

30

0 ,

. t

t alLoadducedThermAirp

SoakSolar

t

tSolar

t

t BaselineAirp TCmQQTCm

AirInletAirExit TTT −=∆

ducedLoadBaseline NetSolarNetSolarSolar QQQRe,, −=∆

23 2007-01-1194

Integrated Modeling Model the STS over a drive Model the STS over a drive cycle and find the fuel usecycle and find the fuel use

CAD

RadTherm

ThermalComfort

AirConditioning

Cabin Thermal/Fluid

Vehicle

FuelEconomy

TailpipeEmissions

OccupantThermal Comfort

ADVISOR

24 2007-01-1194

Impact on Fuel Economy

• Vehicle simulator used to assess impact of reduced AC load.

FTP Drive Cycle

Fuel Economy no AC 18.5Fuel Economy with Baseline AC 15.4Fuel Economy with 70% Baseline AC 16.1

Fuel Economy (mpg)

25 2007-01-1194

Impact on Fuel Use

• US Average AC use - 32.6% (MAC Summit 2004)

• US Vehicle Miles Traveled - 11,998 (Wards 2005)

FTP Drive Cycle

Fuel Used with Baseline AC 42.6Fuel Used with 70% Baseline AC 31.4Fuel Savings per Vehicle 11.2

Annual Fuel Used per Vehicle for AC (gal)

26 % Reduction in AC fuel use for this vehicle

26 2007-01-1194

ConclusionsSignificant reduction in cabin interior temperatures demonstrated 30% reduction in thermal loadPotential for lower power A/C system or A/C used less oftenReducing fuel use of vehicle air conditioning is within reach with current technology

27 2007-01-1194

AcknowledgementsDOE

Lee SlezakEd Wall

NRELCharlie KingMatt KeyserAaron OakleySean Gooding

EPAStephen AndersenKaren ThundiyilKris Taddonio

NissanDavid Barwin

GMGreg MajorBill HillDavid Drapkin

WebastoJames Cowen

I-MAC Team 3Gary Pollak, SAEPaul Hoke, FordAl Reginaldo, ToyotaHashem Akbari, LBNL

AVLReinhard Tatschl

ThermoAnalytics, Inc.Craig MakensCraig Cless

BETA CAE SystemsGeorge Galaitsis