1. Warmteopslag met
Fase-
overgangsmaterialen
Mogelijkheden en uitdagingen
Wim van Helden
Workshop Thermisch Energieopslag met Fase-overgangsmaterialen
Heerlen, 17 Februari 2011

2. Heat Storage: Enabling
Technology

3. 4 Principles for Heat
Storage
• Sensible heat h
- principle: heat capacity
- reservoirs, aquifers, ground/soil
T
• Latent heat h
- principle: phase change (melting,
evaporation)
T
- water, organic and inorganic PCMs h
• Sorption heat and Chemical heat
- principle: physical (adhesion) or
T
chemical bond (reaction enthalpy)
- adsorption and absorption and chemical
reactions

4. 4224
Development Stages of TES Technologies
Water (sensible) PCM (latent) Sorption TCM (chemical)
Market mature Demonstration Development Research
CHARGE
+ heat → +
STORE
DISCHARGE
+ → + heat

5. Classification of Thermal Energy Storage
18-11-2008 PCM Side Event

6. Storage Functionality
Application determines functionality in terms of:
• Charging and Discharging Power
• Temperatures
• Storage capacity
• Storage density
• Efficiency (heat transfer, heat loss, auxiliary
energy)
Majority of improvements through materials
R&D

7. PCM Energy stored as
function of temperature

8. Latent heat storage in
PCMs
PCM interesting at small temperature difference (around melting
temperature)
Volume for 1 MJ storage Mass for 1 MJ storage
25 25
water water
20 20
kilograms
TH29 TH29
litres
15 15
10 10
5 5
0 0
0 - 100 10 - 60 15 - 40 20 - 30 0 - 10010 - 60 15 - 4020 - 30
temperature difference (° C) temperature difference (° C)

9. PCM
• Warmteopslag rondom smelttemperatuur
• Organische materialen of zouthydraten
• Aandachtspunten:
– Warmtegeleiding en warmteoverdracht
– Onderkoeling
– Ontmenging (bij zouthydraten)

10. Improved heat transfer
• Add carbon nanotubes
Source: Tekniker,
Spain
AFM image of as received carbon nanotubes
• High heat transfer carrier material
PCM embedded in expanded
graphite (SGL Carbon)

11. PCM subcooling
• “undershoot” of solidification T
• No proper nucleation
Test and Characterization (A2)
DSC results, 2nd trial with pre-defined standard
300
heating, 1 K/min
cooling, 1 K/min
250 heating, 0,5 K/min
cooling, 0,5 K/min
heating, 0,2 K/min
cooling, 0,2 K/min
enthalpy [kJ/kg]
200
heating, 0,1 K/min
cooling, 0,1 K/min
150
100
50
0
20 21 22 23 24 25 26 27 28 29 30
Archivierungsangaben
temperature [°
C] 1

12. Improve Nucleation
• Additives, mixtures
Microencap-CaCl2·6H2O Microencap-CaCl2·6H2O Microencap-CaCl2·6H2O with
with SrCl2·6H2O Ba(OH)2·8H2O
Source: AIDICO,
Spain

13. Toepassingen
• Koudeopslag (ijs)
• Opslag van (zonne)warmte in bouwdelen
• Transport van warmte

14. Cold Storage
• Use cheap nighttime
electricity
• Lowering of peak
electric power
• Reduction of nominal
cooling capacity
• latent heat storage in
ice
• polyethylene balls filled
with water

15. Organic PCMs
Left to right:
- powder: 60% paraffine and
silica material
- granulate: 35% paraffine
and diatomee earth
- boards: 65% paraffine and
wood fibre board
New development.
Compound: 80%
paraffine, for direct
contact with water, for
instance in reservoir

16. Organic PCMs
Standard product:
PCM granulate in floor combined with floor
heating
New development:
Gypsum board impregnated with PCM.

17. Phase change Materials in walls
development project with the partners
BASF, caparol, maxit and Sto with
Fraunhofer ISE 1/1999 - 9/2004
funded by BMWi
FKZ 0329840A-D

18. measurements
two identical rooms
measured without and with
two PCM products monitored
one year each
result:
- 4 K difference reached
- night ventilation
essential

19. Since 2004 several BASF: micronal
products:
Different macrocapsules:
Dörken, Rubitherm, SGL,
Climator and others
SmartBoard™
Different products with Foto: BASF
microcapsules: plaster,
plasterbords, porous
concrete… …..
Other systems: Energain,
Rubitherm granules

20. Latent heat storage: PCM
for daily storage
• demonstration house in
Perth, Australia
• day storage of solar heat
from 30 m2 collectors
• storage in 90 m2 TH29-
system (equivalent to 0,65 m3
PCM)
• TH29-system: capsules on
long strips integrated in floor,
melting temperature of PCM
29ºC
• buffer is charged with
flexible pipes between
capsules
• LT floor heating system

21. Latent heat storage:
inorganic PCMs
Nodule of Cristopia:
HDPE ball filled with
eutectic salt
plug
air
PCM
PCM can of Climator:
HDPE shell typically applied in
transformer rooms
and telecom
installations

22. Latent heat storage in
inorganic PCMs
Sodium acetate
storage system. The
PCM is charged and
discharged by
circulating a synthetic
oil, passing heat to
the exterior by a heat
exchanger.
This system is further
developed into the
Varioheat product.

23. phase change slurries (PCS)
carrier fluid + PCM
e.g. water/water glycol
as fluid und Paraffin-
microcapsules as PCM
advantage : greatly enhanced storage/transport capacity in
small temperature range, thus:
smaller storages
reduced losses due to isothermal storage
lower pumping energy due to lower mass flow
increasing the storage/transport capacity of a existing
system just by exchanging the fluid
research-project 12/2001 - 11/2004 ; funded by EU

24. From suspensions to emulsions and further
Suspension
micro-encapsulated Paraffin
Hard shell made of PMMA
Size range between 1 and 20 µm, is determined
by the capsule
Emulsion
Emulsified Paraffin
Dispersion based on polar forces
Size of the particles is variable also in the
application
clathrathes, …

25. heat storages with PCM in tanks - concepts
PCM PCM
Water Water
Paraffin
BASF
source of pictures: TU-Graz/BASF/ISE

26. 4224
Materials and Applications
Two International Energy Agency (IEA) programmes:
Energy Conservation through
Energy Storage
Solar Heating and
Cooling

27. 4224
Task 42/24: Compact Thermal Energy
Storage: Material Development for System
Integration
Joint Task between Solar Heating and Cooling (SHC) and Energy
Conservation through Energy Storage (ECES)
Operating Agents:
- SHC: Wim van Helden, ECN (NL)
- ECES: Andreas Hauer, ZAE Bayern (DE)
January 2009 – December 2012
Semi-annual Expert Meetings
4th Expert Meeting: 21 February 2011, Belfast, UK
Main added value:
Bring together experts from applications and material science

28. 4224
Application Related Activities
IEA Task/Annex 42/24
Cooling
Heating / DHW
High Temp. Applications
Matrix approach
Material Related Activities Material Engineering / Processing
Test and Characterisation
Numerical Modelling
Apparatus / Components
Theoretical Limits

29. Phase Change Material with supercooling
Heat storage capacity of sodium acetate tri-hydrate
800
Stored energy [kJ/litre ]
700
Sodium acetate
600 Supercooling
500
400 Water
300
Activation of
200 solidification
100 Melting point = 58 °C
0
20 30 40 50 60 70 80 90 100
Temperature [°C]
29

30. System design
180 litre DHW tank
Tap schedule:
50 l at 7:00, 12:00 and 18:00
DHW auxiliary ~ 2500 kWh/year
135 m² “Passive house”
Heating demand:
PCM storage 15 kWh/m²/year ∼ 2010
Space heating kWh/year
auxiliary
A solar heating system with 36 m² solar collectors and a 6 m3 PCM
heat storage divided into 24 modules can fully cover the heat demand
of a Danish low energy house
30

31. Heat storage material
58% (weight%) NaCH3C00
42% (weight%) water
Melting point: 58°C
☺ Stable supercooling
31

32. 305 kg salt water mixture
Module volume: About 234 l
32

33. Task42-Annex24
PHOTOVOLTAIC EFFECT
The efficiency of a PV cell depends on:
the kind of semiconductor used;
Energy Conservation through Energy Storage (ECES)
the intensity of the solar radiation;
the temperature of the PV cell.
200
Produttore The efficiency of PV is computed from its
“Peak Power”
150
Pmax = Vmax • I max
Potenza [W]
100
25 C
50 C
50
75 C
The efficiency of a PV system is
0
generally declared about 10-17%.
0 10 20 30 40 50 60 70
Tensione [V]
6
Valerio Lo Brano, Ina Ciulla

34. Task42-Annex24
HOW TO KEEP LOW TEMPERATURE?
Keeping cooler the PV panel
Energy Conservation through Energy Storage (ECES)
will increase the performance
There are different substances with high latent heat, that allow the storage of big amount of
heat during a solid-liquid phase transition.
For pure substances this transition takes place at a constant temperature. The process of
melting and solidifying can be repeated for a high number of cycles with no change in their
physical and chemical properties.
8
Phase Change Materials (PCMs).
Valerio Lo Brano, Ina Ciulla

35. Task42-Annex24
EXPERIMENTAL SYSTEM
Made up of experimental system:
Energy Conservation through Energy Storage (ECES)
Valerio Lo Brano, Ina Ciulla

36. Onderkoeling
• Door onderkoeling stollen micro-geëncapsuleerde
PCM deeltjes niet of slechts gedeeltelijk
• Tegengaan door toevoegen van ‘vreemde’ moleculen
• Onderzoek bijvoorbeeld bij Aidico, Spanje

37. Inorganic PCM microencapsulation. Previous results.
Differential Scanning Calorimetry (DSC)
Nucleating agent (wt%) Tm (ºC) ∆Hm (kJ/kg) Supercooling (ºC)
None 24.15 48.0 42.74
SrCl2·6H2O 21.68 37.97 33.61
Ba(OH)2·8H2O 22.99 67.91 22.25
CaCl2·6H2O (SrCl2·6H2O)

38. Inorganic PCM microencapsulation. Previous results.
Scanning Electron Microscopy (SEM)
Microencap-CaCl2·6H2O Microencap-CaCl2·6H2O with SrCl2·6H2O
Microencap-CaCl2·6H2O with
Ba(OH)2·8H2O

39. Third Expert Meeting
of Task 42 / Annex 24
“Compact Thermal Energy Storage –
Material Development for System Integration”
21 – 23 April
Bordeaux, France
SOLID-SOLID PHASE CHANGE
MATERIALS (SSPCMs)
Dr Cemil ALKAN
Gaziosmanpaşa University
Tokat/Turkey

40. Material Phase change Phase Phase Phase
temperature change change change
(heating temperature enthalpy enthalpy
periode) oC cooling (heating (cooling
periode) oC periode) J/g periode) J/g
Poly(Styrene-co-p-stearoyl 33.43 29.00 44.56 -32.55
styrene (%25 Stearoyl
chloride)
Poly(Styrene-co-p-stearoyl 24.84 29.05 50.43 -45.05
styrene (%50Stearoyl
chloride)
Poly(Styrene-co-p-stearoyl 29.70 29.42 54.84 -46.33
styrene (%75Stearoyl
chloride)

42. PCM
• Compacte warmteopslag bij een kleine Delta-T
• Toepassingen in een groot temperatuur bereik
• (micro)encapsulatie om:
– Ontmenging tegen te gaan
– Warmteoverdracht te vergroten
– Slurry te maken
• Onderkoeling kan een probleem zijn
• Onderzoek en ontwikkeling:
– PCM verbeteren
– Nieuwe of verbeterde toepassingen