HOW TO OPTIMISE ENERGY STORAGE IN BUILDINGS?

Gilles BaudoinResearch assistant (UCL-Architecture et Climat)

Which applications for phase change materials? 27/09/2017

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Phase Change Materials

In Building Applications

To Optimise Thermal Mass

PCM

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Phase Change Materials

PCM

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Why is an ice cube more efficient to cool my glass than 0°C liquid water?

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0°C

20°C

17°C

0°C

7°C

Temperature: an indicator of sensibleand latent heat

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Equivalent EnergyReservoir

80°C

0°C

335 kJ 335 kJ

Stored Heat[kJ/kg]

Unlike ice cube, latent reservoir of 0°C liquid water is already filled

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0°C

0°C

20°C

20°C

0°C

Equilibrium is achieved at 17°C with 0°C liquid water

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0°C

0°C

17°C

20°C

0°C

17°C

Equilibrium is achieved at 7°C with the ice cube

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0°C

7°C

20°C

0°C

7°C

0°C

Main characteristics and differences betweenreal PCMs and ideal PCMs

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T

E

Tf

ΔTf

Latent HeatEl [J/g]

Latent Heat

Heat Capacity [J/K]

Sensible Heat

Phase Change Materials

In Building ApplicationsPCM

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MeltingTemperature Tf

Latent HeatEl [kJ/L]

Phase Change Materials… for building applications

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1. Kalnæs, S.E. and B.P. Jelle, Phase change materials and products for building applications: A state-of-the-art review and future research opportunities. Energy and Buildings, 2015. 94: p. 150-176.

ComfortTemperature range

Is it somethingnew?

Telkes M. (1949) Storing solar heat in chemicals - A report on the Dover house

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PCM for building applications: an historicalperspective

± 2000

Micro-encapsulation

1949

Macro-encapsulation

Shape-Stabilized PCMs

Immersion

± 1980

P. Schossig (2005) point of view

2014

Kosny (2014) point of view

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27/09/2017

P. Schossig (2005) point of view: limitation of previous works

• PCMs that are not encapsulated may interact with the building structure and change the properties of the matrix materials, or leakage may be a problem over the lifetime of many years.

• Macro- capsules have the disadvantage that they have to be protectedagainst destruction while the building is used (no drilled holes or nails in the walls/ceiling).(…) Another problem with macro-capsules is the decreasing heat transfer rate during the solidification process when PCMslike paraffins are used, with poor heat transfer coefficients in the solidstate. This may prevent the system from discharging completely overnight.

• Due to these limitations, none of the PCM products had a big marketimpact.

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Classification of PCMs integration in building

EnvelopeSystems

PCMs

1 23

1. System applications2. Passive applications3. Active applications

RessourcesOccupant comfort

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Technical specifications for PCMs selection

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1. Soares, N., et al., Review of passive PCM latent heat thermal energy storage systems towards buildings’ energy efficiency. Energy and Buildings, 2013. 59: p. 82-103.

Commercial PCM products for passive applications

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Energain

SSPCM

ENRG Blanket

Macro-encapsulation

Knauf

Micro-encapsulation

Phase Change Materials

In Building Applications

To Optimise Thermal Mass

PCM

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Thermal mass and water reservoir analogy

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Heat Capacity[Joules/K]

Reservoir Area[L/m]

Stored Energy [Joules] Stored Water [L]

TWater Height[m]

Thermal mass in the « building system »

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ΔT

Internal gains

Solar gains

Inside

Tint

TextOutside

Intensive ventilation

Ex/infiltrationHygienic ventilation

Transmission

Intermittent RenewableEnergy

Energy NR

Energy NR

HeatingSystem

CoolingSystem

Tc

PCMs change thermal mass shape

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Heavyweight Lightweight PCM tuning

T

Levers for action to optimise thermal mass

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Heat capacity

Heat capacity used (24 h)

Meltingtemperature

Latent Heat

Latent HeatUsed (24h)

Active > 24h

Air EnvelopeFurniture

Active < 24h

Tc

2 PCMS withdifferent Tf

Activation

Classical PCM use to increase thermal mass in lightweight buildings

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« Lightweight » Building

+

PCM

=

PCM Envelope

T confort

Case study: effect of thermal mass optimisation on cooling loads in a south-oriented office

• Scenarios for cooling

• Thermal mass variation without PCM

• Thermal mass variation with PCM

1 m2 PCM/m2 floor

Gains

Loss

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Effect of different scenarios on the annualcooling energy (kWh/m2 an)

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ΔT

Gains

Inside

Tint

TextOutside

HeatingSystem

Cooling System

Tc

I

LossI

Effect of different scenarios on the annualcooling energy (kWh/m2 an)

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ΔTIntérieur

Tint

TextExtérieur

Tc

Loss

GainsS1 = S0 + Heat Recovery

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S2 = S1 + Solar protection

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S3 = S2 + Diurnal Free Cooling

15S4 = S3 + Night Free

Cooling7

S0 Heavyweight

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I

Passive

DayNightCooling

System

Effect of thermal mass on the annualcooling energy (kWh/m2 an)

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ΔTIntérieur

Tint

TextExtérieur

Tc

Loss

GainsS1 = S0 + Heat Recovery

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S2 = S1 + Solar Protection

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S3 = S2 + Diurnal Free Cooling

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S4 = S3 + Night Free Cooling

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S0 Heavyweight

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I

Passive

DayNightCooling

System

1

2

1

3

Effect of thermal mass + PCM on the annualcooling energy (kWh/m2 an)

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ΔTIntérieur

Tint

TextExtérieur

Tc

Loss

Gains

S4H

7.03

IDayNightCooling

System

1 m2 exchange surface/ m2 floor

PCM effect:El 110 J/g; Tf 23; ΔTf 10,53 cm PCMs wallboard

6.86 5.69

ΔEc 1.17 ; 17%

S4L

10.32 10.297.83

ΔEc 2.46 ; 24%

1,3 m2/m2 floorExchange Surface

Cooling loads evolution (kWh/m2 an) in different scenarios

35,03

33,71

24,50

14,59

7,03

6,86

5,69

10,32

10,29

7,83

7,03

4,62

S0 Lourd

S1 Lourd (Echangeur de chaleur)

S2 Lourd (Protection solaire)

S3 Lourd (Ventilation 2V/h diurne)

S4a Lourd (Ventilation 2V/h nocturne Tset 21)

S4a Lourd + 1m2 /m2

S4a Lourd + 1m2 PCM/m2

S4a Léger

S4a Léger + 1m2/m2

S4a Léger + 1m2 PCM/m2

S4a Léger + 1,3m2 PCM/m2

S4b (Ventilation 2V/h nocturne Tset 15)

↗LambdaΔEc 0.1

↗ Exchance surfaceΔEc 0.4

↗ PCM quantity4 ep: ΔEc 0.44 surf: ΔEc 2.4

ΔEc 1.17 ; 17%

ΔEc 2.46 ; 24%

1 m2 exchange surface/ m2 floorEl 110 J/g; Tf 23; ΔTf 10,53 cm PCMs wallboard

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PCM in Building Applicationsto Optimise

Thermal MassSTOCC

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Gilles BaudoinArchitecture et Climat - UCL

Appendix 1: Ecooling in function of Tf,ΔTf and El

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

20 22 24 26

Energain

Without pannel

1 m2 exchange surface/ m2 floorEl 110 J/g; Tf 23; ΔTf 10,53 cm PCMs wallboard

↗ El , ↘ E cooling(110 ,220 (limite paraffine),550 (limite sels hydratés) ,1100 (cas extrême)

↗ ΔTf , ↗ E cooling(1,3,6,10)

Optimum Tf 23°C

E cooling(kWh/m2an)

Melting Temperature Tf

Appendix 2: Ecooling in function of PCM quantity: increasing of width and number of panels

0

1

2

3

4

5

6

7

0 5 10 15 20 25

E cooling(kWh/m2an)

x * the initial surface/width

Ep varS varLambda variable

PCM

PCM…

PCMPCM

Appendix 3: cooling loads in the south-oriented office

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