PCM Pellets for Thermal Energy Storage in Buildings

Ramin Abhari, P.E.July 22, 2013

Smart Building Construction Materials and Coatings

Honolulu, HI

Thermal Energy Storage (TES)

$$$?!

$!

Conventional Building System

Building System with PCM Thermal Storage

Day

Night

Air-Conditioning

Natural Ventilation Night

Night

DayPCM

Thermal Storage

The Prize for StorageL

oa

d,

arb

itra

ry s

ca

le

(me

ga

wa

tts)

1:0

0

2:0

0

4:0

0

3:0

0

5:0

0

6:0

0

7:0

0

8:0

0

9:0

0

Time of Day

10

:00

11

:00

13

:00

12

:00

14

:00

15

:00

16

:00

17

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18

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19

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:00

0:0

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Peak Load Power PlantsIntermediate Load

Power Plants

Base Load Power Plants

Typical summertime demand curve

Typical demand curve with TES

24

:00

200

300

400

500

600

700

800

900

1,000

-50 -40 -30 -20 -10 0 10 20 30 40 50 60

Enth

alpy (

J/g)

Temperature (deg C)

H-T Curves for Water and Octadecane Phase Change

Material (PCM)

Making PCM: Step 1. Paraffin Synthesis

O

O

O

O

O

OHC

+ 6 H2O + C3H8

+ 15 H2

3

(octadecane)

(veg oil)

H2C

H2C

NiMo cat

C16-C18 paraffin composition

Melt point = 21-23 ºC

Heat of fusion = 170-190 J/g

Making PCM: Step 2. Shape-Stable Pellets

70% paraffin, 30% HDPE

Twin-Screw Extruder

Under-water pelletizer

PVDC latex coating

Ethyl cellulose pre-coat

Wurster fluid-bed spray coater

Making PCM: Step 3. Coated Pellets

94%

95%

96%

97%

98%

99%

100%

101%

102%

0 1 2 3 4 5 6 7

Perc

ent o

f Ini

tial P

CM P

elle

t Mas

s Rem

aini

ng

Heat/Wash Cycle

Effect of PVDC Coating on Paraffin Seepage from PCM Pellets

5 kg scaleup coating lab coating uncoated

Coating eliminates paraffin seepage from PCM pellets

Alternate Pellet Coating

6% oil-absorbing calcium silicate powder in V-blender

SEM shows good two layer coverage

No paraffin seepage, but not solvent resistant

0

20

40

60

80

100

120

18 19 20 21 22 23 24 25 26 27 28

Ther

mal

Ene

rgy

Stor

ed (J

/g)

Temperature (ºC)

PCM pellet

brick

concrete

PCM Pellet Thermal Properties

Thermal mass in a flexible form

Compatible with sustainable architectural practices

Passive Storage: Building Envelopes

ORNL field test 2012

Add PCM to insulation

33% ↓ peak heat flux

13% ↓ net heat gain

-10

-5

0

5

10

15

20

25

30

35

40

0

1

2

3

4

5

6

7

8

9

10

8/29 8/30 8/31 9/1 9/2 9/3 9/4 9/5

Tem

pera

ture

(T),

'C

Heat

Flu

x (H

F), W

/m2

Heat Flux and Wall Cavity Temperatures: Aug 29 - Sept 4

HF cell

HF cell+PCM

HF cell/PCM/cell

T wall ext

42% reduction

Wall exterior temperature

Heat Flux across Cavities

Building Envelope Weekly Test Results

Heat Flux thru Cellulose Control

Heat Flux thru Cellulose+ PCM

PCM-Modified Insulation: Whole Building Model Addition of PCM

pellets to attic insulation

Up to 16% reduction annual electricity use

11-16 year payback

PCM-Modified Insulation: Flame Tests

PCM pellets added to cellulose attic insulation

Conformed to ASTM C739 flammability standard

Non-Passive Storage: Fixed-Bed Tubes

14” diam X 7.5’ PVC or PC pipe segment and a fan (cheap!)

Reduces heat gain of the inhabited space (1 ton-hr cooling capacity)

Warm a

ir

in (day)

Cool air out (day)

1

2

2

Cool air in (night)

Warm air out (night) 1

3

Air

flow

thro

ugh

bed

of P

CM

pel

lets

7.7 ft

14" ODPVC pipe

Air Out Air Out

Air In Air In

Outside

Wall

Inside Inside

10X higher heat transfer rate than passive storage

Replacing Daytime AC: Tube Wall

Visible energy conservation!

Summary

Demonstrated PCM production using commercial-scale equipment

PCM pellet performance validated in passive storage field test

Fire test passed on PCM-enhanced insulation system

Non-passive (PCM tube) application under development

Acknowledgements

U.S. Department of EnergySouthwest Research InstitutePolymer Center of ExcellenceAdvanced Fiber TechnologyThe Coating PlaceFraunhofer CSE