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Phase Change Materials for
Thermal Energy Storage
Jose Pereira da Cunha
Materials Review
Inorganic Eutectics Mass Ratio
Tmelt ΔHfusion Edensity
°C kJ/kg kWh/m3 AlCl3-ZnCl2 48-52 114 607 395
AlCl3-NaCl 80-20 106 285 156
AlCl3-LiCl 83-17 114 250 150
AlCl3-KCl 78-22 128 253 150
AlCl3-CaCl2 78-22 119 267 149
FeCl3-LiCl 57-43 150 353 257
AlCl3-KCl-LiCl 44-52-3 85 196 111
AlCl3-KCl-NaCl 58-26-15 88 191 102
LiNO3-KNO3 33-67 133 160 99
+18% NaNO3 30-18-52 120 135 78
KNO3-NaNO2 56-44 141 145 91
+ 7% NaNO3 58-7-35 142 266 144
KNO2-NaNO3 48-52 149 153 94
LiNO3-KCl 44-56 160 272 174
+5% NaNO3 53-5-42 160 266 173
LiNO3-NaNO3 48-52 190 280 175
+1% LiCl 48-1-51 180 267 169
KNO3-Mg(NO3)2 46-54 178 128 83
NaOH-KOH 37-63 170 207 127
LiOH-LiNO3 19-81 183 776 484
Organic - Inorganic Eutectics Mass Ratio
Tmelt ΔHfusion Edensity
°C kJ/kg kWh/m3
K2CO3-Urea 15-85 102 225 100
NaCl-Urea 20-80 103 254 108
KCl-Urea 18-82 115 243 105
Mass Ratio
Tmelt ΔHfusion Edensity °C kJ/kg kWh/m3
Salicylic acid - Malonic acid 57-43 87 217 98
Salicylic acid - Benzoic acid 33-67 107 164 66
Malonic acid - Benzoic acid 36-64 107 183 77
Benzoic acid - Oxalic acid 67-33 114 312 135
Succinic acid- Benzoic Acid 29-71 116 189 77
Malonic acid - Succinic acid 47-53 119 268 126
Organic Melts CAS Tmelt ΔHfusion Edensity °C kJ/kg kWh/m3
Oxalic acid dihydrate 6153-56-6 105 370 178
Maleic acid 110-16-7 131 235 109
Adipic acid 124-04-9 152 220 101
HDPE MI 12g/10min 9002-88-4
130 255 67
HDPE MI 2g/10min 135 260 69
Phthalic anhydride 85-44-9 131 160 68
2-Chlorobenzoic acid 118-91-2 142 164 75
d-Mannitol 69-65-8 165 300 140
Inorganic Melts CAS Tmelt ΔHfusion Edensity °C kJ/kg kWh/m3
Ba(OH)2-(H2O)8 12230-71-6 78 270 164
Mg(NO3)2-(H2O)6 13446-18-9 90 150 72
MgCl2-(H2O)6 7791-18-6 117 120 68
Organic TGA Analysis
• Organics sublime around their melting point;
• Oxalic Acid dihydrate has a initial dehydration stage;
• Adipic Acid seemed suitable, but thermal stage
indicated also sublimation in its melting point;
Inorganic TGA Analysis
• Salt Hydrates dehydrate in their melting point:
Barium Hydroxide lost 1 water molecule;
Magnesium Nitrate lost 4 water molecules;
Magnesium Chloride lost 5 water molecules;
Organic DSC Analysis
• Mannitol and HDPE are the most suitable for
thermal storage;
• Normal lid tests showed good cycling properties;
• Adipic Acid proved thermal stability in
closed container;
Normal lid
Hermetic lid
Organic DSC Analysis
• 2-Chlorobenzoic acid and Phthalic Anhydride were
thermally stable only in hermetic container;
• Oxalic acid dihydrate showed poor thermal cycling even in
closed lid;
• Maleic Acid was inconclusive (large sub cooling didn’t allow
full crystallization);
Inorganic DSC Analysis
• Salt Hydrates • Dehydration leads to evolution of melting point;
• In closed container, only Barium Hydroxide proved not suitable for thermal storage;
Inorganic DSC Analysis
• Eutectic Mixtures • Excellent
Thermal
Properties;
• Very
hygroscopic;
LiNO3 – KNO3
LiNO3 - KCl
Inorganic DSC Analysis
• Eutectic Mixtures
• Only Nitrite
mixtures were non
hygroscopic;
LiNO3 – NaNO3
NaNO2 – KNO3
Conclusions
• Organics tested need to be enclosed for thermal storage;
• Only Mannitol and HDPE are stable at their melting temperature;
• Salt hydrates dehydrate severely in their melting point, also requiring a enclosed system for thermal storage;
• All inorganic eutectics tested showed excellent thermal cycling properties;
Organic Melts CAS Lid Tmelt ΔHfusion Cps Cpl Edensity ΔTWater
°C kJ/kg J/kg.K kWh/m3 for 1m3
Oxalic acid dihydrate 6153-56-6 Hermetic 105 269 2108 2890 135 116
Maleic acid 110-16-7 Hermetic 138 305 1662 2335 144 124
Adipic acid 124-04-9 Normal 153 96 810 1330 40 35
Hermetic 155 219 1750 2140 90 78
HDPE MI 12g/10min 9002-88-4
Normal 128 109 2600 2150 35 30
HDPE MI 2g/10min Normal 130 119 2560 2090 38 33
Phthalic anhydride 85-44-9 Hermetic 133 207 1925 2320 97 83
2-Chlorobenzoic acid 118-91-2 Hermetic 142 127 1390 1670 61 53
d-Mannitol 69-65-8 Normal 169 269 1700 2400 120 103
Inorganic Melts CAS Lid Tmelt ΔHfusion Cps Cpl Edensity ΔTWater
°C kJ/kg J/kg.K kWh/m3 for 1m3
Ba(OH)2-(H2O)8 12230-71-6 Hermetic 82 241 1346 2445 151 130
Mg(NO3)2-(H2O)6 13446-18-9 Hermetic 93 100 2500 3100 56 48
MgCl2-(H2O)6 7791-18-6 Hermetic 120 142 2000 2400 69 59
Eutectic Melts m/m
Lid Tmelt ΔHfusion Cps Cpl Edensity ΔTWater
% °C kJ/kg J/kg.K kWh/m3 for 1m3
LiNO3-KNO3 33-63 Stitched 128 135 1070 1430 82 71
"+18% NaNO3" 30-18-52 Stitched 127 167 1450 2030 104 90
LiNO3-KCl 58-42 Stitched 169 141 1430 1780 88 76
"+ 5% NaNO3" 53-5-42 Stitched 167 152 1530 1970 95 82
"+ 24% NaNO3" 42-24-34 Stitched 155 54 2120 1442 40 35
LiNO3-NaNO3 48-52 Stitched 195 142 1780 3150 99 85
"+1% LiCl" 47-1-52 Stitched 193 118 1780 2810 85 73
"+6% LiCl" 45-6-49 Stitched 195 210 1450 2250 137 118
KNO3-NaNO2 56-44 Stitched 142 45 2030 2485 38 33
KNO3-NaNO3 -NaNO2 56-44 Stitched 144 76 2210 1550 54 46
Color Code
Discarded
Poor thermal Cycling
Less Promising
Promising
Most Promising
Future Work
• Thermal Cycling of promising organics near their melting point (+- 20C);
• Development of a small scale prototype for higher volume testing;
• Sell-and-tube;
• Tube in tank;
• Preparation of Chloride
eutectics and novel nitrite
eutectics;
• Continuous research on
nitrate eutectics: • Adition of other salts;
• Corrosion tests of proven
samples;