In-situ thermal analysis of
thermochemical materials for
heat storage applications
Claire Ferchaud, Herbert Zondag
05.02.2015
www.ecn.nl
EXPERTA-ECN Technology Day
February 5, 2015, Petten, The Netherlands
Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Outlines of the presentation
• Context of the study
• In-situ thermal analysis: methods and setup
• Performance test on TCM’s
• Conclusions and outlook
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Context of the study
• Energy consumption for households in the Netherlands
primary energy consumption in 2009
Heat demand > 65 %
corresponds to 450 PJ/year
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Context of the study
• Domestic heat demand fulfilled
by solar energy
• Need of seasonal heat storage
Different heat storage technologies
kWh/month
> 24 m3
12 m3
6 m3
sensible
latent
chemical
0.25 GJ/m3
0.5 GJ/m3
1 GJ/m3
For a passive house of 110 m2 = 6 GJ
Domestic application  Thermochemical heat storage
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Context of the study
• System development  atmospheric and
integrated system
Solar tube
collectors
Charge
Discharge
Temperature
< 150°C
10 – 50 °C
P(H2O)
8 - 20 mbar
13 mbar
Living rooms
Heat
load
Bath
Kitchen
• Selection of thermochemical materials
– TCM (s) + nH2O (g) ↔ TCM.nH2O (s) + heat
Borehole
Heat
discharge
Thermochemical
seasonal heat
storage
– High energy density (1 GJ/m3 in packed bed)
– Low cost materials
– Safe process, non toxic properties
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
In-situ thermal analysis: methods and set-up
• Objectives: performances of TCM’s under in-situ application conditions
• Required thermal performances
– Energy density of the material (in GJ/m3)  35% porosity
– Reaction rate of the dehydration and hydration reactions  heat power
– Long term stability over thermal cycles (deh./hyd.)
• Experimental conditions
– Fixed p(H2O) = 13 mbar
isotherm
150°C
– Fixed flow rate = 100 ml/min
– Trange = 50-150°C
isotherm
50°C
– Heating/cooling rates = 1°C/min
dehydration
hydration
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
In-situ thermal analysis: methods and set-up
• Thermal analysis technique selected:
Simultaneous thermogravimetry (TG) and
differential scanning calorimetry (DSC)  STA
• Simulation of the application conditions by
means of a humidification system
STA
apparatus
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
In-situ thermal analysis: methods and set-up
• STA calibration
– Dry to moist atmosphere (1-20 mbar)
– Al crucible (25 mL)
– Different heating/cooling rates (0.1 – 10 K/min)
Standards
Tfusion (°C)
biphenyl
68.93
indium
156.61
tin
231.92
bismuth
271.41
zinc
419.53
Sensitivity (mV/mW)
Sensitivity calibration STA
1,1
0.1 K/min
1
0.2 K/min
0,9
0.5 K/min
0,8
1 K/min
0,7
2 K/min
0,6
5 K/min
0,5
0
100
200
300
400
10 K/min
Temperature (°C)
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Performance test of TCM’s
• Example of MgCl2.6H2O
– Mass changes (TG)
– Heat flow variations (DSC)
46
MgCl2.6H2O
24
Baseline drift
MgCl2.4H2O
64
42
MgCl2.2H2O
Two reaction steps for the deh./hyd. :
Energy density (35% porosity) :
MgCl2.6H2O ↔ MgCl2.4H2O + 2H2O
•
E density (deh.) = 1.24 GJ/m3
MgCl2.4H2O ↔ MgCl2.2H2O + 2H2O
•
E density (hyd.) = 1.05 GJ/m3
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Performance test of TCM’s
• Example of MgCl2.6H2O
– Correction of the DSC signal
Fitting of the baseline by polynomial linearization
corrected heat flow (mW/mg)
3,0E-01
DSC dehydration
2,0E-01
Investigation of the intrinsic
thermodynamical properties at
different p(H2O) conditions
DSC hydration
1,0E-01
0,0E+00
-1,0E-01
Deviation = heat losses from
open DSC cup design of the
in-situ characterization
-2,0E-01
-3,0E-01
-4,0E-01
-5,0E-01
-6,0E-01
40
50
60
70
80
90
100
Temperature (°C)
110
120
130
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Performance test of TCM’s
• Example of MgCl2.6H2O
In-situ thermal analysis over 23 cycles
Hydrolysis reaction
MgCl2.2H2O  MgClOH + H2O
Hydrolysis of MgCl2.xH2O = f(HCl)
 Open sorption system p(HCl) ≈ 0
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
20
0,2
40
60
80
100
120
140
Heat flow (mW/mg)
0,0
• Example of MgSO4.7H2O
-0,2
-0,4
– Mass changes (TG)
% mass (%)
100
Thermogravimetry
MgSO4. 6H2O
90
80
70
Tonset = 34°C
MgSO4. H2O
60
50
20
40
60
40
60
80
80
100
120
Temperature (°C)
Dehydration : 2 steps of reactions
• MgSO4.(7-x)H2O  MgSO4.6H2O + xH2O
• MgSO4.6H2O  MgSO4.H2O + 5H2O
120
140
0,0
-0,2
-0,4
– 20“Corrected”
heat
flow
variations
(DSC)
40
60
80
100
120
140
Thermogravimetry
DSC
100
0,0
90
80
-0,2
dehydration
hydration
70
-0,4
60
50
110
-0,6
20
20
0,2
100
140
100
DSC
110
-0,6
0,2
MgSO4. 6.75H2O
flow (mW/mg)
Heat
(%)
% mass
110
-0,6
(%)
% mass
(mW/mg)
eat flow
Heat flow (mW/mg)
Performance test ofDSC
TCM’s
20
0,2
90
0,0
80
40
40
60
60
80
80
100
120
140
100
120
140
Thermogravimetry
Temperature (°C)
DSC
Theoretical energy density = 1.49 GJ/m3
-0,2
70
Stored energy density = 1.29 GJ/m3
60
-0,4
50
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Performance test of TCM’s
20
40
60
80
100
• 0,025
Example of MgSO4.7H2O
0,000
– Mass changes (TG)
110
-0,025
Thermogravimetry
% mass (%)
100
90
16
80
Formation of MgSO4. 6H2O
after 100h in one step reaction
70
60
20
40
60
80
Heat flow (mW/mg)
0,050
60
80
100
0,050
0,025
0,000
– “Corrected”
heat60flow variations
(DSC)
20
40
80
100
0,075
110
-0,025
DSC
Thermogravimetry
100
0,050
90
0,025
80
70
0,000
60
110
-0,025
100
20
20
0,075
100
time (hours)
Hydration : 1 progressive step of reaction
• MgSO4.H2O + 5H2O  MgSO4.6H2O
 Low kinetic of reaction
40
DSC
(%)
% mass
flow (mW/mg)
Heat
DSC
20
0,075
(mW/mg)
Heat flow
(%)
% mass
Heat flow (mW/mg)
0,075
40
40
60
60
80
100
80
100
Thermogravimetry
time (hours)
DSC
90
0,050
Released energy density = 0.013 GJ/m3
80
in the first 25h
0,025
70
60
0,000
110
-0,025
20
40
60
80
100
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Performance test of TCM’s
Materials
Safety
Cost (€/T)
Effective energy
density (GJ/m3)
Kinetics/ Power
Material
stability
Zeolites 13X
+
5000
0.24 (50°C)
+
+
CuSO4.5H2O
-
1000 - 1500
0.013 (50°C)
-
+
MgSO4.7H2O
+
75 - 150
0.013 (50°C)
-
+
MgCl2.6H2O
+
150 - 200
1.05 (50°C)
+
Overhydration,
hydrolysis (HCl)
CaCl2.2H2O
+
75 - 150
1.05 (50°C)
+
Overhydration
SrCl2.6H2O
+
500-800
0.25 (50°C)
-
+
Experimental conditions : Tdehydration = 130°C or 150°C , Trehydration = 25 or 50°C, p(H2O)=13 mbar, zeolites density calculated
with 13.8%wt(H2O) uptake, and bulk density of 650kg/m3, salt hydrates density estimated for 50% packed bed porosity
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Claire Ferchaud, ECN, EXPERTA-ECN Technology Day, February 5, 2015, Petten, The Netherlands
Conclusions and outlook
• A thermal analysis set-up was developed to quantify the thermal performances
of TCM’s under in-situ conditions by addition of a humidification system to the
initial STA apparatus selected for this study.
• The thermal performance test contributed to identify the most promising
material (chloride salt hydrates) and their issues based on energy density,
kinetic properties and stability, for the domestic application.
• Outlook: solve issues of the in-situ characterization
– Identify the origin of the deviation of the DSC baseline vs. temperature
– Correction of the experimental material performances for the heat losses
– Further adjustment of the apparatus for investigation at higher p(H2O)
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Thanks for your attention
Claire Ferchaud
Research Thermal System – PhD student
[email protected]
Westerduinweg 3
1755 LE Petten
The Netherlands
P.O. Box 1
1755 ZG Petten
The Netherlands
T +31 88 515 44 54 [email protected]
F +31 88 515 86 15 www.ecn.nl