Investigation of Earth Potential Rise on a typical single phase HV network
Understanding Potential for Phase Change Material ... · Understanding Potential for Phase Change...
Transcript of Understanding Potential for Phase Change Material ... · Understanding Potential for Phase Change...
© Fraunhofer USA 2009
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, COJuly 21, 2010
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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 ???
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Our Predecessors Knew How to Use Thermal Mass and Live in Hot Climates Without Air-Conditioning
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Native Americans Preferred Massive Adobe Homes
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Igloo is a First Known PCM House Developed for Heating Dominated Climates
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Today, there is a serious reason why, we may utilize PCM thermal mass in building envelopes?Diminishing energy savings’ returns for conventional insulations
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Energy Savings kBtu/year per ft2 of Floor Area
R-va
lue
rang
e, h
.ft2 .
°F/B
tu
Living Room&
Open Kitchen Area Bedroom #3
Bedroom #2
Main Bedroom
Bathroom
Main Bath
Single story ranch house – floor area 130 m2 (1400 ft2)
9.5-
m (2
6-ft)
16-m (53-ft)
Attic insulation Atlanta
Energy Consumption Change GJ per year
R-v
alue
Cha
nge
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Time [hrs]
Btu
/(hr-
ft2)
~70%
~90%
Conventional asphalt shingle roof
Metal roof with cool-roof surface, PCM, and sub-venting
Metal roof with cool-roof surface, and sub-venting
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Time [hrs]
Btu
/(hr-
ft2)
~70%
~90%
Conventional asphalt shingle roof
Metal roof with cool-roof surface, PCM, and sub-venting
Metal roof with cool-roof surface, and sub-venting
PCMs are only one of many engineering means helping to enhance thermal performance of buildings
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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
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Whole Building HVAC Energy [GJ]
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Attic R-value
Typical Roof Insulation Roof R-38 Insulation with 20% of PCM
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Bakersfield, CA
Dynamic Attic R-value Equivalent
Whole Building HVAC Energy [GJ]
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Attic R-value
Typical Roof Insulation Roof R-38 Insulation with 20% of PCM
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Bakersfield, CA
Dynamic Attic R-value Equivalent
PCMs can be blended with conventional insulations
R-38 PCM-enhanced Attic Insulation in Bakersfield, CA works like R-75 conventional Insulation
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Understanding of PCMs
Phase Change Process“Melting/Crystallization heat” Ice-Water: Δ H = 333 kJ/kg
at 0oC(32oF)
333 kJ/kg
Temperature Difference“Heat capacity”
Water: cp ≈ 4.2 kJ/kg · K
1oC 80oC (34oF 176oF)
332 kJ/kg
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Engineering Functions of PCMs
Local Temperature Control Peak Load Time Control Dynamic Thermal Break Enhanced Heat Storage Thermal Comfort
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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
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PCM Thermal Mass in Buildingscan 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
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Traditional Approach – Concentrated PCM - Thermal Storage
PCM charged bythe interiortemperature swings and solar gains through the glazing
Building HVAC system used todischarge PCM
Schematic of Distribution of Heating and Cooling Loads in Old PCM Applications
Energy Discharged Later by HVAC System
CavityInsulation
PCM-Thermal Storage
Exterior Finish
Exterior
Interior
Peak Loads
Energy Transferred INTO the Building
Energy Transferred Back to the Environment
Solar Gains
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More Advanced PCM Applications
Use fluctuations in exterior temperature and solar irradiationfor charging and discharging of PCM
PCM material has to be able to fully charge and discharge energy during 24-hour dynamic cycle
Schematic of Distribution of Heating and Cooling Loads in PCM-Enhanced Building Envelopes with Thermally Active Core
Peak Hour Energy Transferred Back to the Environment
ThermallyActive Core
LOW HEATTRANSFERZONE
Gypsum BoardLow Delta T
Min. Heat Transfer
Exterior Finish
Exterior
Interior
Peak Loads
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Large Selection of Inorganic and Organic PCMs is available today
PCM powder
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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
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Thermal Characteristics of PCMs which have to be seriously considered
Enthalpy for commonly-used paraffinic PCM
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TEMPERATURE [C]
[J/g
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melting freezing
Thermostat temperature control +/-2degF
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Current Estimates for Expected Thermal Characteristics of PCMs to be used in residential buildings
Approximate PCM melting temperatures for Southern U.S. locations
Conditioned space
Approximate Range of Useful Temperature Fluctuations in Different Parts of the Building is Between 40oF and 180oF
Solar
HoursTe
mpe
ratu
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150F
110F
80F
70F
65F
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Some PCM Products are pretty COMPLEX and may require detailed simulations and advanced testing methods
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ZFrame 001 08 Mar 2009 23-degF PCM HF apparatus SS test 3-D
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T001107.063104.125101.18898.2595.312592.37589.437586.583.562580.62577.687574.7571.812568.87565.9375
Frame 001 08 Mar 2009 23-degF PCM HF apparatus SS test 3-D
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PCM Technologies which have been Developed and already Field Tested in Collaboration with DOE’sBuilding Envelopes Program
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New PCM-Enhanced Fiber Insulations - New Approach for Dispersed Thermal Mass
Blown Fiberglass Blown Cellulose
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PCM-Enhanced Cellulose Insulation has been Field Tested in Two Locations
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PCM-Enhanced Blown FiberglasAttic field testing in Oak Ridge, TN
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PCM Test House in Oak Ridge, TN with R-30 PCM Walls and R-50 PCM Attic Insulation
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Four generations of roofs with PCM heat sinkshave been field tested in Oak Ridge, TN
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What to Avoid with PCM Technologies?
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Price over $3.50 per lb for material of minimum heat storage density of 150 J/g
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Final enthalpy of the PCM heat sink product lower from 120 J/g
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Enthalpy for commonly-used paraffinic PCM
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TEMPERATURE [C]
[J/g
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melting freezing
PCMs with significant sub-cooling effects
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This temperature gap has to
be min.
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Potentially Leaky PCM Packages with Corrosive PCMs
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