butikofer de oliveira vernay architectes

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Thermal Storage in Smart PCM Walls:An enhanced and controlled discharge power by forced convection

Presented by Antoine BossAuthors: J. Robadey, R. Wegmüller, A. Chiriatti, G. Magnin, E.L. Niederhauser15. Symposium Energieinnovation, February 16th 2018, TU Graz, Austria

Outline

• Description of the active PCM concept• Testbed• Set-up• Measurements• Simulations

• Simulations of a reference building • PCM of 23°C and 26°C with day and night loading• Active and passive PCM

• Conclusion and outlook

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concept validation}

Active PCM concept

• Electrical battery can be charged and discharged at every moment

• Standard PCM (Phase Change Material):• can be loaded on demand (heating)• discharged as soon as Tint < Tc

• NEW CONCEPT with on demand activation of the PCM discharge

• Solution

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Storage managementnot possible

Charge à Heating an insulated PCMStorage à PCM remains insulatedDischarge à Ventilation of the PCM

• Heating with a water circuit

• Discharging with an air flow

• PCM:• micronal encapsulated paraffin with Tc = 23/26°C

• in «Lehmorange» plates

• Advantage:• discharge can be controlled

• wall can be furnished

Concept of a ventilated PCM wall

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opening

with grid

floor

cross-

sectionair flow

3-way

valve

heating system

between PCM

plates

air flow

insulation

Testbed: PCM wall in the middle of two rooms

heating system

PCM-Plate

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Active discharge

Smart PCM Walls : Simulation results External and box temperatures

ext

PCM

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TairTextTPCM

air

Smart PCM Walls : Comparison Measures-SimulationsTwo days cycle

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+ 5°C

40mn

Text measuredTPCM measuredTair measuredT simulated

Simulations of a reference building

bearing walls

PCM walls

22 m

8 m

3 x 3 3 x 5

2 x 22

Height 3m per floorBuilding has 2 floorsTotal volume: 1’000 m3

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administrative building(not occupied at night and during week-ends)

Heating process with PCM walls

HeatPump

• Goal: increase the building autonomy and assure comfort temperature during building occupancy

• 4 states:• Loading: Heat pump on without ventilation• Storage: no heating and no ventilation• Discharge: Ventilation (heat pump off)• Heating: Heat pump on with ventilation

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6 12 18 24 6 Time:

Thermal state

comforttemperature

Heating process with PCM walls

HeatPump

• Goal: increase the building autonomy and assure comfort temperature during building occupancy

• 4 states:• Loading: Heat pump on without ventilation• Storage: no heating and no ventilation• Discharge: Ventilation (heat pump off)• Heating: Heat pump on with ventilation

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6 12 18 24 6 Time:

Thermal state

comforttemperature

Heating process with PCM walls

HeatPump

• Goal: increase the building autonomy and assure comfort temperature during building occupancy

• 4 states:• Loading: Heat pump on without ventilation• Storage: no heating and no ventilation• Discharge: Ventilation (heat pump off)• Heating: Heat pump on with ventilation

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Ventilation

6 12 18 24 6 Time:

Thermal state

comforttemperature

Heating process with PCM walls

HeatPump

Ventilation• Goal: increase the building autonomy and assure comfort temperature during building occupancy

• 4 states:• Loading: Heat pump on without ventilation• Storage: no heating and no ventilation• Discharge: Ventilation (heat pump off)• Heating: Heat pump on with ventilation

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6 12 18 24 6 Time:

Thermal state

comforttemperature

Simplified simulations• Text constant the whole day all around the building

• Solar heating inside the building and wind effect are neglected

• U-value = 0.15 W/m2K for the building envelope

• Comfort temperature of about 20.5°C between 06h and 17h30 • Air renewal: 0.5 Vol/hour from 7h to 18h with 90% heat recovery

• PCM loaded with 12kW either during the day or night

• day: from 9h30 to 16h

• night: before 6h

• Simulation performed from 6h to 6h the next day with goals:

• recover the same temperatures: Tint, Tconcrete, TPCM and the same PCM loading• in case of insufficient heating time à study the drops of Tint, Tconcrete, TPCM and PCM loading

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} but no more than 6h30

Day loading:

PV panels à Heat pump: 12KW à PCM

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Tem

pera

ture

(°C)

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T PCM board

T air int

Tc = 23°CDay loadingsimulation results

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Daytime (hour) 16

T air int

PCM discharge:• Tc=23°C à comfort temperature

until Text = -10°C• Tc=26°C à comfort temperature

until Text = - 5°C

• superiority of 23°C PCM due to lower overnight discharge than 26°C PCM

Day loadingsimulation results

Tc = 26°CTc = 23°C

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Tem

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(°C)

Daytime (hour)

Tc = 23°C

T PCM board

Night loading:

Electricity Network à Heat pump: 12KWà PCM

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Tem

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Night loadingsimulation results

Tc = 23°C

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Tem

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T PCM board

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Night loadingsimulation results

Tc = 26°CTc = 23°C

T air int

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Tem

pera

ture

(°C)

Daytime (hour)

Tc = 23°C

• Both PCM: Tc=23°C and Tc=26°C allow to maintain comfort temperature until Text = -5°C

• Night loading requires a larger storage capacity than day loading due to large time-lag between PCM charge and discharge

Passive versus active PCMcomparison

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12kW: 4½ h

passive PCM 23°C

active PCM 23°C

day loading, Text = 0°C

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12kW: 4½ h

Conclusion• Concept of active PCM walls for heating validated by lab tests and simulations:

• + 5°C in 40mn• Studied system suitable for outdoor temperatures between -5°C and +10°C

• PCM with Tc =23°C has higher performances compared to 26°C (due to lower overnight discharge) but requires ventilation• Day loading requires lower storage capacity than night loading (due to lower

heating-loading time-lag)• Active PCM has lower heat losses at night time than passive PCM (continuous

natural convection)

PERSPECTIVES and OUTLOOK• For very cold days: combination of day solar power

+ the necessary night loading defined after weather forecast• PCM with Tc of 23°C can also provide cooling• Integration in real building / demonstrator

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Thank you for your attention!

Questions?

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Back-up slides

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1rst élément central elements last element

ventilation

thermocouple

opening with grid

floor

floor

floor

sidecut

Air flow

3-wayvalve

Heating systembetween PCM plates

Modularelements ~ 25 cm

floor

heig

ht

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PCM loaded at 06:00 am / at 16:00 pm

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U = 0.15 W/Km2

U = 0.15 W/Km2

with latent heat in a single step

PCM loaded at 06:00 am / at 16:00 pm

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