Latent heat storage in concrete

Dipl.-Ing. Jens H. Dieckmann

University of KaiserslauternDepartment of Construction Physics and Technical Equipment

Prof. Dr. rer. nat. H. Heinrich

Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Principle effect

conclusion:In a small temperature range a lot of energy can be stored with small mass and volume of the material.

Latent heat storage

Latent heat storage

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Example water

The heat of fusion is nearly as much as energy can be stored in the liquid phase.

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase change materials (PCM)

For applications in the building structure paraffins and salt hydrates are suitable.

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Comparison of thermal masses

Comparison of the layer thicknesses of different building materials heat capacity: approx. 5700 kJ Temperature range: 10 K

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

PCM as building product

PCM can't be used directly as building product because of their material properties (e.g. melting)!

At present there are three solutions to get PCM into common building products: - Macro encapsulation - Micro encapsulation - Storage in porous matrix structures

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Macro encapsulation

Kissmann, Germany Christopia, France

TEAP, Australia

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Microencapsulation

Knauf KG Gypsum plasterboard

Maxit Group Climatic finery

Micronal,

BASF AG

Further one: Aerated concrete stones, loam plates…

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

PCM in carrier structures

Advantage: - Better activating because of better heat conductivity - No problems by volume stretch - Inexpensive

Fiber boards (Rubitherm) clay/tone - granulates (Rubitherm)

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

The innovation

+In order to develop a kind of concrete which can be directly used in the construction elements with improved physical characteristics.

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We connect non capsulated paraffin with light weight rock granulations.

Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Advantages

Depending on Application!

• More effective heat storage• Possibly no need for other utilities• Smaller construction units • Constant room temperature • Higher thermal comfort • Protection from overheating• Smoothing of temperature peaks • Shift of the peak load times • Saving of fossil energies

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Development process

Phase 1: Selection of the suitable light rock granulation as PCM carrier matrix and the selection of the further concrete components

Phase 2: Choice of a suitable filling variant

Phase 3: Development of concrete recipe

Phase 4: Analysis of the improved thermal material properties

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 1

Considered the characteristics of building material-technological and building physics aspects, e.g.

• Large PCM capacity

• High heat conductivity

• High firmness

in order to assure the suitability of the materials for our purposes.

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 1

Micro copies:

Blowing glass: Wash pumice:

Large differences in surface texture, pore volume, pore size, pore distribution, pore type…

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 1

Basis is the DIN 4226-2 and DIN EN 13055-1 • Bulk density according to DIN EN 1097-3 • Water absorption according to DIN EN 1097-6 • Gross density according to DIN EN 1097-6 • Pure density according to DIN 52102 • Overall porosity according to DIN 52102 • Water content according to DIN 1097-5 • Determination of the heat conductivity according to DIN 52612 • Grain pressure strength after appendix A of the DIN EN 13055-1…

Lab tests from the building material-technological and the building physics aspect:

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Result:Wash pumice, nature pumice, blowing glass, blowing slate

Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 1

Lab tests from the building material-technological and the building physics aspect:

Basis is the DIN 4226-2 and DIN EN 13055-1 • Bulk density according to DIN EN 1097-3 • Water absorption according to DIN EN 1097-6 • Gross density according to DIN EN 1097-6 • Pure density according to DIN 52102 • Overall porosity according to DIN 52102 • Water content according to DIN 1097-5 • Determination of the heat conductivity according to DIN 52612 • Grain pressure strength after appendix A of the DIN EN 13055-1…

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Result:Wash pumice, nature pumice, blowing glass, blowing slate

Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 2In phase 2 different filling variants were examined.

•Melting

•Evacuation

•Splashing

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Result:

up to 100 M.% admission

Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 3

Find a suitable concret recipe!

Consideration of the desired material properties such as minimum pressure firmness, Pump ability, and maximum PCM content

Challenges:

e.g. separation,

Heat of hydration

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

0

5

10

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22 24 26 28 30 32

C[k

J/(k

g²K

)]T [°C]

0

5

10

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22 24 26 28 30 32

T [°C]

C[k

J/(k

g²K)

]

Phase 4

PCM concrete PCM content: (wet): 26,8 V.% 16,4 M.%

Lightweight concrete More directly Composition without PCM

Theoretical, idealized result of the specific heat capacity

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Spec. Thermal capacity PCM concrete: 45,86 kJ/Kg Spec. Thermal capacity comparison concrete: 19,16 kJ/Kg

Increase about 139%

Phase 4 – heat capacity

0,00

5,00

10,00

15,00

20,00

25,00

30,00

35,00

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45,00

50,00

21,00 23,00 25,00 27,00 29,00 31,00

T[°C]

Δc [k

J/kg

]

Result:Latent heat storage

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 4 – intermittent heat transferLatent heat storage

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Wooden test wall between two climatic rooms

Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Two different test disks (50*50cm) in the test wall

Phase 4 – intermittent heat transferLatent heat storage

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Programmed temperature characteristics

Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

maxio ,ϑao,ϑ

ao,ϑΔ

ϑ

Mϑ

min ao,ϑ

ao,p

max ao,ϑ

io,ϑΔ

Mϑ io,p

max io,ϑ

min io,ϑ

Programmierte Temperaturverläufe

0

510

1520

25

3035

40

0 2 4 6 8 10 12 14 16 18 20 22 24

t [h]

T [

°C]

Außen (Klimaraum I) Innen (Klimaraum II)

Heat flow trough the test wall

Phase 4 – intermittent heat transferLatent heat storage

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 4 – intermittent heat transfer

Intermittent heat transfer:

Latent heat storage

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 4 – intermittent heat transfer

Intermittent heat transfer:

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Phase 4 – intermittent heat transfer

Result:

Improvement: 78%

Improvement: 26 %

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Thermography cooling down behavior

Thermography image at beginning of the test

Thermography image after 2 hours

Thermography image after 4 hours

Cooling down behavior

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

• The PCM concrete can be designed for the requirements of application

• PCM concrete can support the building heat or protect from summer overheating

• the Implementation as active system increases the efficiency of the heat storage

Summary / ConclusionLatent heat storage

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

• Possible locations in the building structure are ground, walls, cover…

Summary / ConclusionLatent heat storage

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Activated base plate for heater support

One example of useLatent heat storage

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Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann

Thank you foryour attention

Latent heat storage in concreteDipl.-Ing. Jens H. Dieckmann