Use of PCM Enhanced Insulation in

the Building Envelope David W. Yarbrough, PhD, PE Jan Kosny, PhD William A. Miller, PhD, PE Building Technology Center

Oak Ridge National Laboratory

Oak Ridge, Tennessee, USA

Limitations

• Standard method to reduce heat flow is to add R-value. • Limits have been reached. • Adding more R-Value is not practical when space is limited.

Basic Concepts A thin layer of Phase Change Material (PCM)

that maintains a constant temperature is used

to control the ∆T across a layer of insulation.

The PCM stores and releases heat as the surrounding temperatures change.

PCM CAN BE CONFIGURED TWO WAYS

PCMs can be localized or distributed in an insulation or some other building material. Exterior temperatures must cycle across the phase change temperature for the PCM to be useful. Materials for use in a building envelope are selected with a phase change material near the occupied space temperature. PCMs include organic materials that melt in the temperature range 60 to 90 °F. Inorganic salt solutions exhibiting large heats of solution or dilution can also be used.

Without PCM Layer Thermocouples Typ.

Attic

R 24

+ + + + + +

Ceiling

120.0 F 112.3 F 106.6 F 100.0 F 93.30 F 86.60 F 80.00 F

Temperature distribution is linear. Heat flow into ceiling is 1.666 BTU/ ft2·h under these conditions.

With PCM Layer PCM layer Attic

Thermocouples

120.0 F 100.5 F 81.00 F 80.75 F 80.50 F 80.25 F 80.00 F

R8 R16

Ceiling

PCM layer is 0.125 inch thick and maintains 81 °F throughout the diurnal cycle. Heat flow into ceiling is 0.0625 BTU/ft 2 · h. (1.666 without PCM)

Low Space Requirements

• A 0.125 in. thick layer of PCM (0.5 lb) with thermal resistance on both sides will last a complete diurnal cycle.

Test Box 1/8 inch PCM Layer

Diurnal Cycle T3 T2

R=6 foam board

T1

Room Temp

R=16 foam board

One Cycle Demonstration

No PCM Heating 2.29

No PCM

13.30

115

110

105

100

95

90

85

80

75

70

PCM Heating 0.15

PCM Cooling

Heating Saved 93%

4.36

Cooling Reduction 67.2%

0.25 lb of Octadecane per sq. ft.

Heating Cooling

63.64%

65.04%

2.63 5.37

Temperature (F)

110 90 70 50

1

49

97

145

193

One 24 Hour Cycle

241

289

337

Peak Load is Shifted

Temperature (F)

Normal Peak

120 100 4 hrs.

80 PCM Peak

60 1

49

97

145

193

241

Time (10 min. increments)

289

337

Lower Heat Flow into

Building.

• Reduction in heat flow into the conditioned space is demonstrated. • These examples demonstrate the potential

for heating and cooling load reductions.

Observations 1. A thin layer of phase change material can control the T difference across an inner layer of insulation for several hours. 2. The amount of Phase Change Material needed can be minimized by thermally protecting it with a second layer of insulation 3. Optimum amount and position is provided by simulation for a given site and location in the building envelope.

HFM CAN BE OPERATED IN TRANSIENT

MODE TO TEST PCMs

Test specimen is initially isothermal at a temperature below the phase change temperature. One plate is ramped quickly to a temperature above the phase change temperature. The heat fluxes in and out of the test specimen are monitored with time. A comparison of heat flux data for specimens with and without PCM is used to evaluate performance.

Test Configuration • • • • • •

Top Plate – cold Top layer of insulation R = 9 ft2·h·°F/Btu

Layer of PCM Bottom layer of insulation R=5 ft2·h·°F/Btu

Bottom Plate – cold ramps to hot hot ramps to cold

TEMPERATURES ABOVE AND BELOW THE PHASE CHANGE

TEMPERATURE ARE UTILIZED

Test specimen is initially isothermal. bottom plate 69.8 °F top plate 70 °F Bottom plate temperature changed rapidly to a temperature above the phase change temperature. bottom plate 69.8 °F to 120.2 °F Result is a positive flux (into specimen) on the hot side and negative flux (out of specimen) on the cold side. (charging) Bottom plate temperature is returned to initial temperature when steady state is achieved. (discharging) This procedure can be carried out for specimens with and without PCM.

Hot-Side Flux During the Charge and Discharge Portions of the Cycle Cellulose with 0% PCM

Flux (Btu/ft^2.h)

20 10 hot side/flux in/out

0

cold side/flux out

-10 -20 0

50 100 150 200 250 300 350 Time (minutes)

Hot-Side Flux During the Charge and Discharge Portions of the Cycle for Cellulose with 30 wt% PCM

Comparison of the “Charging” of Cellulose Insulation Materials with and without PCM

Comparison of the Flux out of the Cellulose Insulation Materials with and without PCM

Total Heat into Cold Plate as a Function of PCM Content

Heat Flux Data for Inorganic PCM Heat Flow into Conditioned Space 4

F lu x

3

No PCM Chloride 1

2

Chloride 2

1 0 0

100

200 Time (minutes)

300

400

A COMPARISON OF FLUX DATA FOR SPECIMENS WITH AND WITHOUT PCM ALLOWS AN EVALUATION OF PERFORMANCE Heat Flow into Conditioned Space 4

Flux

3 No PCM

2

PCM

1 0 0

100

200 Time (minutes)

300

400

HFM CAN BE USED TO MONITOR HEAT FLUX FOR INSULATION WITHOUT PCM

Transient Heat Flow Meter Test flux into spe cime n is positiv e 10

Heat Flux

5 Hot Side

0

Cold Side

-5

-10 0

36

72

108 144 180 216

Time (minute s)

Total Heat Discharged to Hot Plate as a Function of PCM Content

Wall Containing Cellulose-PCM Blend have been Tested in a Hot-Box (C 1363)

PCM–Enhanced Cellulose Insulation has been Tested in Field Conditions In Two Full-Scale Demonstration Projects 2x6 Wood-Framed Walls were Used

North-Western Wall

South - Facing Wall

In Both Experiments, Walls Containing ~ 20% PCM were Instated Next to the Walls without PCM

Charging and Discharging PCM 90.0

Discharging time about 6 hours

Temp. inside the wall F

PCM is absorbing heat and melting

PCM is releasing heat and solidifying

80.0

Temperatures inside the wall cavity: Thick line – PCM Thin line – No PCM

Charging time about 6 hours 70.0 1

13

25

37

49

61

73

85

Cellulose W all East No PCM (oF) CELL_E_TC5

97

109

121

133

145

157

169

181

Cellulose W all W est W / PCM (oF) CELL_W _TC5

193

Significant Difference in Energy

Performance was Observed

Example of Heat Flux Measurements 2

Heating Load

•

1.5 1

0.5

•

Btu/hft2

0 1

49

97

145

193

241

289

337

385

433

481

529

577

625

673

-0.5

PCM wall -1

•

-1.5 -2

No PCM wall -2.5 -3

Cooling Load

time [h/4]

One week of data Sunny days Cool nights

•

PCM wall is significantly more thermally stable than the other wall Peak-hour heat flux reduction by at least 1/3 in PCM wall Significantly lower heat flux amplitude in PCM wall ~2 hours shifting of the peak-hour load by PCM wall

Potential 40% Cooling Load Savings for 40 oF Temperature Excitation 2006 ORNL Dynamic Hot-box testing of 2x6 Wall with PCM-Enhanced Cellulose Insulation (22% PCM) Cluster of PCM pellets

Reduction [%]

Cellulose fiber

Surface Load

0.5 0.4

42.00% 27.00%

0.3

19.00%

0.2 0.1 0 First 5 hours

First 10 hours

All 15 hours

Long-Term Energy Performance Monitoring

Spring, Summer, Fall, Winter 2006

and Spring 2007

130

Example of Results from ORNL 2006 Measurements 120 Exterior

surfaces

Temperatures [F]

110

100 Interior

surfaces

90

80

70

One week data Sunny days Cool nights

60 Exterior air

50

1

49

97

145

193

241

289

337

Cellulose Wall East No PCM (oF) CELL_E_TC1 Cellulose Wall West W/ PCM (oF) CELL_W_TC1 ESRA OUTSIDE T/C (oF) AMB_AIR

385

433

481

529

577

Cellulose Wall East No PCM (oF) CELL_E_TC8 Cellulose Wall West W/ PCM (oF) CELL_W_TC8

625

673

PCM-Enhanced Cellulose in Test Walls

100.0

•

Temp. inside the wall F

90.0

85 oF

•

PC action

78 oF

80.0

•

• Temperatures inside the wall cavities: Thick lines – PCM Thin lines – No PCM

70.0

PCM stabilizes the core of the wall by its heat storage capacity Warming and cooling down of the core in the PCM wall is significantly slower Peak-hour temperature excitation is shifted in PCM wall Significantly lower temperature amplitudes can be observed in PCM wall cavities

60.0 1

13

25

37

49

61

73

85

97

Cellulose Wall East No PCM (oF) CELL_E_TC3 Cellulose Wall East No PCM (oF) CELL_E_TC5 Cellulose Wall West W/ PCM (oF) CELL_W_TC4

109

121

133

145

157

169

181

193

Cellulose Wall East No PCM (oF) CELL_E_TC4 Cellulose Wall West W/ PCM (oF) CELL_W_TC3 Cellulose Wall West W/ PCM (oF) CELL_W_TC5

% Cooling Load Reductions 100

90

Cooling-dominated loads

80

70

60

50

Average ~42% 40

30

20

April

May

June

July

August

Sept.

Oct.

Nov.

Dec.

Jan.

10

0 0

5

10

15

20 Weeks

25

30

35

40

Summary

• Several applications of microencapsulated organic PCMs were tested. • Applications with localized PCM have been tested. • Laboratory and field work demonstrated good

performance of PCM-enhanced insulation

– Thermal conductivity of the PCM-enhanced cellulose was not increased by the addition of PCM microcapsules – Cellulose wall with dispersed PCM demonstrated potential for over 40% reduction of the peak thermal load during 5 hour thermal ramp

• Field tests confirmed hot-box test data on cooling load reduction potential of PCM-enhanced cellulose • Field tests demonstrated potential for application of PCMs in mixed and heating-dominated climates for reduction of heating loads