Understanding Potential for Phase Change Material Applications in Residential Buildings

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1 Fraunhofer Center for Sustainable Energy Systems Understanding Potential for Phase Change Material Applications in Residential Buildings Jan Kosny Ph.D. Building Enclosure Program Lead Residential Energy Efficiency Meeting, sponsored by the U.S. Department of Energy's (DOE) Building America Program Denver, CO July 21, 2010

2 Massive Stone Cave - A First Home for Human Beings: WHY? flat temperature profile year around uniform radiation temperature fields uniform humidity no drafts fresh air???

3 Our Predecessors Knew How to Use Thermal Mass and Live in Hot Climates Without Air-Conditioning

4 Native Americans Preferred Massive Adobe Homes

5 Igloo is a First Known PCM House Developed for Heating Dominated Climates

6 Today, there is a serious reason why, we may utilize PCM thermal mass in building envelopes? Diminishing energy savings returns for conventional insulations Single story ranch house floor area 130 m 2 (1400 ft 2 ) Main Bath Main Bedroom R-value Change R-value range, h.ft 2. F/Btu m (26-ft) Living Room & Open Kitchen Area Bedroom #3 16-m (53-ft) Bathroom Bedroom # Attic insulation Atlanta Energy Savings kbtu/year per ft 2 of Floor Area Energy Consumption Change GJ per year 6.54

7 PCMs are only one of many engineering means helping to enhance thermal performance of buildings Conventional asphalt shingle roof Btu/(hr-ft2) ~70% ~90% Metal roof with coolroof surface, and sub-venting Metal roof with coolroof surface, PCM, and sub-venting Time [hrs]

8 Other Enabling Technologies for New Generation of Dynamic Multifunctional Envelopes Thermal Insulations Reflective Insulations Radiant Barriers Cool Coatings (cool roofing, cool walls) Conventional Thermal Mass Phase Change Materials Ventilated Cavities BIPVs and Solar-Thermal Systems Mechanical or Radiant Systems and Hydronic Heat Exchangers

9 PCMs can be blended with conventional insulations R-38 PCM-enhanced Attic Insulation in Bakersfield, CA works like R-75 conventional Insulation Whole Building HVAC Energy [GJ] Attic R-value Bakersfield, CA Dynamic Attic R-value Equivalent Typical Roof Insulation Roof R-38 Insulation with 20% of PCM

10 Understanding of PCMs Phase Change Process Melting/Crystallization heat Ice-Water: Δ H = 333 kj/kg at 0 o C (32 o F) Temperature Difference Heat capacity Water: c p 4.2 kj/kg K 1 o C 80 o C (34 o F 176 o F) 333 kj/kg 332 kj/kg

11 Engineering Functions of PCMs Local Temperature Control Peak Load Time Control Dynamic Thermal Break Enhanced Heat Storage Thermal Comfort

12 Key Physical Characteristics and Other Important Parameters of PCMs Total Enthalpy (heat storage capacity) Necessary Amount => Cost Phase Change Temperatures melting freezing Sub-Cooling Effect Purity Location within the Building or Building Envelope

13 PCM Thermal Mass in Buildings can be almost everywhere Parts of the building structure roofs and attics exterior walls interior walls floors, and ceilings fireplaces, stairs, etc... Space Conditioning Systems Furniture Finish materials Passive solar heat storage containers

14 Traditional Approach Concentrated PCM - Thermal Storage PCM charged by the interior temperature swings and solar gains through the glazing Building HVAC system used to discharge PCM Solar Gains Schematic of Distribution of Heating and Cooling Loads in Old PCM Applications Peak Loads Exterior Finish Cavity Insulation Exterior PCM-Thermal Storage Interior Energy Discharged Later by HVAC System Energy Transferred INTO the Building Energy Transferred Back to the Environment

15 More Advanced PCM Applications Schematic of Distribution of Heating and Cooling Loads in PCM-Enhanced Building Envelopes with Thermally Active Core Use fluctuations in exterior temperature and solar irradiation for charging and discharging of PCM PCM material has to be able to fully charge and discharge energy during 24- hour dynamic cycle Peak Loads Low Delta T Min. Heat Transfer Peak Hour Energy Transferred Back to the Environment Exterior Finish Thermally Active Core LOW HEAT TRANSFER ZONE Gypsum Board Exterior Interior

16 Large Selection of Inorganic and Organic PCMs is available today PCM powder

17 Basic Differences in PCM Technologies Inorganic Phase Change Materials Organic Phase Change Materials Different Encapsulation and Packaging Methods; Micro-encapsulation Macro-encapsulation Macro-packaging Different PCM Applications: Dispersed PCMs Concentrated PCMs PCM slurries

18 Thermal Characteristics of PCMs which have to be seriously considered Enthalpy for commonly-used paraffinic PCM 45 Thermostat temperature control +/-2degF [J/g] TEMPERATURE [C] melting freezing

19 Current Estimates for Expected Thermal Characteristics of PCMs to be used in residential buildings Approximate PCM melting temperatures for Southern U.S. locations Solar 110F 80F 150F Approximate Range of Useful Temperature Fluctuations in Different Parts of the Building is Between 40 o F and 180 o F Conditioned space 65F 70F Temperature Hours

20 Some PCM Products are pretty COMPLEX and may require detailed simulations and advanced testing methods Frame Mar degF PCM HF apparatus SS test 3-D Z X Y 3 Frame Mar degF PCM HF apparatus SS test 3-D y x z y 4 X T Z 6 Y

21 PCM Technologies which have been Developed and already Field Tested in Collaboration with DOE s Building Envelopes Program 21

22 New PCM-Enhanced Fiber Insulations - New Approach for Dispersed Thermal Mass Blown Fiberglass Blown Cellulose

23 PCM-Enhanced Cellulose Insulation has been Field Tested in Two Locations

24 PCM-Enhanced Blown Fiberglas Attic field testing in Oak Ridge, TN

25 PCM Test House in Oak Ridge, TN with R-30 PCM Walls and R-50 PCM Attic Insulation

26 Four generations of roofs with PCM heat sinks have been field tested in Oak Ridge, TN

27 What to Avoid with PCM Technologies? 27

28 Price over $3.50 per lb for material of minimum heat storage density of 150 J/g 28

29 Final enthalpy of the PCM heat sink product lower from 120 J/g 29

30 PCMs with significant sub-cooling effects Enthalpy for commonly-used paraffinic PCM [J/g] TEMPERATURE [C] This temperature gap has to be min. melting freezing 30

31 Potentially Leaky PCM Packages with Corrosive PCMs 31

32 Let s Work Together! THANK YOU!