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HOW TO OPTIMISE ENERGY STORAGE IN BUILDINGS?
Gilles BaudoinResearch assistant (UCL-Architecture et Climat)
Which applications for phase change materials? 27/09/2017
1
Phase Change Materials
In Building Applications
To Optimise Thermal Mass
PCM
2
Phase Change Materials
PCM
3
Why is an ice cube more efficient to cool my glass than 0°C liquid water?
4
0°C
20°C
17°C
0°C
7°C
Temperature: an indicator of sensibleand latent heat
5
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
6
0°C
0°C
20°C
20°C
0°C
Equilibrium is achieved at 17°C with 0°C liquid water
7
0°C
0°C
17°C
20°C
0°C
17°C
Equilibrium is achieved at 7°C with the ice cube
8
0°C
7°C
20°C
0°C
7°C
0°C
Main characteristics and differences betweenreal PCMs and ideal PCMs
9
T
E
Tf
ΔTf
Latent HeatEl [J/g]
Latent Heat
Heat Capacity [J/K]
Sensible Heat
Phase Change Materials
In Building ApplicationsPCM
10
MeltingTemperature Tf
Latent HeatEl [kJ/L]
Phase Change Materials… for building applications
11
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
12
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
13
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.
14
Classification of PCMs integration in building
EnvelopeSystems
PCMs
1 23
1. System applications2. Passive applications3. Active applications
RessourcesOccupant comfort
15
Technical specifications for PCMs selection
16
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
17
Energain
SSPCM
ENRG Blanket
Macro-encapsulation
Knauf
Micro-encapsulation
Phase Change Materials
In Building Applications
To Optimise Thermal Mass
PCM
18
Thermal mass and water reservoir analogy
19
Heat Capacity[Joules/K]
Reservoir Area[L/m]
Stored Energy [Joules] Stored Water [L]
TWater Height[m]
Thermal mass in the « building system »
20
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
21
Heavyweight Lightweight PCM tuning
T
Levers for action to optimise thermal mass
22
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
23
« 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
24
Effect of different scenarios on the annualcooling energy (kWh/m2 an)
25
ΔT
Gains
Inside
Tint
TextOutside
HeatingSystem
Cooling System
Tc
I
LossI
Effect of different scenarios on the annualcooling energy (kWh/m2 an)
26
ΔTIntérieur
Tint
TextExtérieur
Tc
Loss
GainsS1 = S0 + Heat Recovery
33
S2 = S1 + Solar protection
25
S3 = S2 + Diurnal Free Cooling
15S4 = S3 + Night Free
Cooling7
S0 Heavyweight
35
I
Passive
DayNightCooling
System
Effect of thermal mass on the annualcooling energy (kWh/m2 an)
27
ΔTIntérieur
Tint
TextExtérieur
Tc
Loss
GainsS1 = S0 + Heat Recovery
33
S2 = S1 + Solar Protection
25
S3 = S2 + Diurnal Free Cooling
15
S4 = S3 + Night Free Cooling
7
S0 Heavyweight
35
I
Passive
DayNightCooling
System
1
2
1
3
Effect of thermal mass + PCM on the annualcooling energy (kWh/m2 an)
28
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
29
PCM in Building Applicationsto Optimise
Thermal MassSTOCC
30
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
33