Phase change materials: overview of PCMs for thermal storage
Phase change materials, or PCMs, store heat during a phase transition. In practice, latent heat is only part of the story: sensible heat, thermal conductivity, cycling stability, corrosion, safety and cost are often just as important. This overview is intended as a technical selection map: temperature first, then energy density, and then the practical disadvantages.
Note: the values in this table are indicative. Latent heat, melting range, specific heat and stability depend on purity, additives, moisture content, measurement method and cycling history. For product development, every candidate material should be re-tested with DSC, cycling tests, corrosion tests and a safety assessment.
How to read the table
Latent is the energy absorbed or released in the phase transition. Sensible is the additional heat storage due to temperature change around that transition. Total is a practical indication of latent plus sensible storage within the stated temperature range. All energy values are in kJ/kg. Advantages and disadvantages are shown under Info
Energy: kJ/kgTemperatures: degrees CelsiusClick Info for advantages and disadvantages
| PCM / material | Formula | Type | Phase °C | Lat. | Sens. | Tot. | Range | Assessment | Info |
|---|---|---|---|---|---|---|---|---|---|
| Water / ice | H2O | inorganic | 0 | 334 | 42 | 376 | -10 to +10 C | high for cold storage | InfoTemp. group: -20 to +100 C Advantages: very low cost; non-toxic; high latent heat Disadvantages / points of attention: only around 0 C; expansion during freezing; frost and corrosion management |
| NaCl-water eutectic | NaCl-H2O | salt solution | approx. -21 | 230 | 40 | 270 | -30 to -10 C | medium | InfoTemp. group: -20 to +100 C Advantages: low cost; low temperature possible Disadvantages / points of attention: corrosive; concentration-sensitive; salt crystallisation |
| CaCl2-water eutectic | CaCl2-H2O | salt solution | approx. -50 to -20 | 150-250 | 30-50 | 180-300 | depends on mixture | medium | InfoTemp. group: -20 to +100 C Advantages: low temperature possible; low cost Disadvantages / points of attention: corrosive; hygroscopic; composition is critical |
| Paraffin C14 | C14H30 | paraffin | 5-6 | 200 | 80 | 280 | -15 to +25 C | medium | InfoTemp. group: -20 to +100 C Advantages: chemically stable; low corrosiveness Disadvantages / points of attention: flammable; low thermal conductivity; fossil origin |
| Paraffin C16 | C16H34 | paraffin | 18 | 230 | 85 | 315 | 0 to 40 C | medium | InfoTemp. group: -20 to +100 C Advantages: stable; narrow transition Disadvantages / points of attention: flammable; low thermal conductivity; volume change |
| Paraffin C18 | C18H38 | paraffin | 28 | 240 | 85 | 325 | 10 to 50 C | medium | InfoTemp. group: -20 to +100 C Advantages: widely used; low corrosiveness Disadvantages / points of attention: flammable; low thermal conductivity; additives needed for power output |
| Paraffin C20 | C20H42 | paraffin | 36-37 | 240 | 85 | 325 | 20 to 60 C | medium | InfoTemp. group: -20 to +100 C Advantages: comfort and low-temperature heat storage Disadvantages / points of attention: slow charging/discharging without a heat exchanger |
| Paraffin C22 | C22H46 | paraffin | 44 | 245 | 85 | 330 | 25 to 65 C | medium | InfoTemp. group: -20 to +100 C Advantages: stable; commercially available Disadvantages / points of attention: fire risk; low volumetric density |
| Paraffin C24 | C24H50 | paraffin | 50-52 | 250 | 85 | 335 | 30 to 70 C | medium | InfoTemp. group: -20 to +100 C Advantages: domestic hot water range possible Disadvantages / points of attention: flammable; low thermal conductivity |
| Paraffin C26-C28 | C26-C28 | paraffin | 56-65 | 250 | 85 | 335 | 40 to 80 C | medium | InfoTemp. group: -20 to +100 C Advantages: stable; widely available Disadvantages / points of attention: not suitable for high temperature; flammable |
| Technical paraffin wax | mengsel | paraffin | 20-70 | 120-220 | 70-90 | 190-310 | depends on type | medium | InfoTemp. group: -20 to +100 C Advantages: low cost; widely available Disadvantages / points of attention: wide melting range; variable quality |
| Capric acid | C10H20O2 | fatty acid | 31-32 | 150 | 80 | 230 | 10 to 50 C | medium | InfoTemp. group: -20 to +100 C Advantages: potentially bio-based; reasonably stable Disadvantages / points of attention: odour; price; possible corrosion on metals |
| Lauric acid | C12H24O2 | fatty acid | 43-44 | 180 | 80 | 260 | 25 to 65 C | medium | InfoTemp. group: -20 to +100 C Advantages: stable; good latent heat Disadvantages / points of attention: odour; low thermal conductivity; more expensive than bulk salts |
| Myristic acid | C14H28O2 | fatty acid | 53-54 | 190 | 80 | 270 | 35 to 75 C | medium | InfoTemp. group: -20 to +100 C Advantages: stable; potentially bio-based Disadvantages / points of attention: price; low thermal conductivity |
| Palmitic acid | C16H32O2 | fatty acid | 62-64 | 200 | 80 | 280 | 45 to 85 C | medium | InfoTemp. group: -20 to +100 C Advantages: reasonable cycling stability Disadvantages / points of attention: price; low thermal conductivity |
| Stearic acid | C18H36O2 | fatty acid | 69-70 | 200 | 80 | 280 | 50 to 90 C | medium | InfoTemp. group: -20 to +100 C Advantages: widely available; relatief veilig Disadvantages / points of attention: too low a temperature for high-temperature storage; odour |
| CaCl2.6H2O | CaCl2.6H2O | salt hydrate | 29 | 170-190 | 70 | 240-260 | 10 to 50 C | medium-low | InfoTemp. group: -20 to +100 C Advantages: low cost; high volumetric storage Disadvantages / points of attention: supercooling; phase separation; corrosion |
| Glauber’s salt | Na2SO4.10H2O | salt hydrate | 32 | 250 | 75 | 325 | 10 to 50 C | low-medium | InfoTemp. group: -20 to +100 C Advantages: high latent heat; low cost Disadvantages / points of attention: strong phase separation; nucleation/additives needed |
| Sodium acetate trihydrate | CH3COONa.3H2O | salt hydrate | 58 | 250-265 | 80 | 330-345 | 40 to 80 C | medium | InfoTemp. group: -20 to +100 C Advantages: high latent heat; known from hand warmers Disadvantages / points of attention: very strong supercooling possible; crystallisation control needed |
| Barium hydroxide octahydrate | Ba(OH)2.8H2O | salt hydrate | 78 | 250-270 | 80 | 330-350 | 60 to 100 C | low | InfoTemp. group: -20 to +100 C Advantages: high storage density Disadvantages / points of attention: barium compound; toxicity; unsuitable for broad application |
| Magnesium nitrate hexahydrate | Mg(NO3)2.6H2O | salt hydrate | 89 | 160-170 | 70 | 230-240 | 70 to 110 C | medium-low | InfoTemp. group: -20 to +100 C Advantages: usable just below 100 C Disadvantages / points of attention: oxidising; corrosion; moisture-sensitive |
| Magnesium chloride hexahydrate | MgCl2.6H2O | salt hydrate | 115 | 167 | 80 | 247 | 95 to 135 C | medium | InfoTemp. group: 100 to 200 C Advantages: high storage density; relatively low temperature Disadvantages / points of attention: corrosive; hydrate degradation possible |
| Erythritol | C4H10O4 | sugar alcohol | 118-120 | 320-340 | 60-70 | 390-410 | 100 to 140 C | medium | InfoTemp. group: 100 to 200 C Advantages: very high latent heat; potentially bio-based Disadvantages / points of attention: strong supercooling; slow crystallisation; degradation/cycling needs investigation |
| Xylitol | C5H12O5 | sugar alcohol | 92-95 | 230-270 | 60-70 | 300-340 | 75 to 115 C | medium-low | InfoTemp. group: 100 to 200 C Advantages: high energy content Disadvantages / points of attention: strong supercooling; slow crystallisation |
| D-sorbitol | C6H14O6 | sugar alcohol | 95-100 | 180-220 | 60-70 | 240-290 | 80 to 120 C | medium-low | InfoTemp. group: 100 to 200 C Advantages: bio-based; reasonably available Disadvantages / points of attention: polymorphism; supercooling; degradation |
| D-mannitol | C6H14O6 | sugar alcohol | 165-168 | 280-320 | 60-70 | 340-390 | 145 to 185 C | medium | InfoTemp. group: 100 to 200 C Advantages: high latent heat; interesting for process heat Disadvantages / points of attention: supercooling; volume change; cycling stability is a concern |
| Urea | CO(NH2)2 | organic | 133 | 240-250 | 65 | 305-315 | 110 to 150 C | low-medium | InfoTemp. group: 100 to 200 C Advantages: low cost; high latent heat Disadvantages / points of attention: decomposition under overheating; ammonia/isocyanate risk |
| Adipic acid | C6H10O4 | organic acid | 152 | 250-270 | 60 | 310-330 | 130 to 170 C | medium-low | InfoTemp. group: 100 to 200 C Advantages: relatively high latent heat Disadvantages / points of attention: acidic; corrosion and decomposition need investigation |
| Benzoic acid | C7H6O2 | organic acid | 122 | 140-150 | 60 | 200-210 | 100 to 140 C | low-medium | InfoTemp. group: 100 to 200 C Advantages: well-known substance; reasonably stable Disadvantages / points of attention: corrosive acid; lower latent heat |
| Acetamide | C2H5NO | amide | 80-82 | 240 | 70 | 310 | 60 to 100 C | low | InfoTemp. group: 100 to 200 C Advantages: high latent heat Disadvantages / points of attention: toxic/irritating; less suitable for buildings |
| NaNO3-KNO3 low-melting mixture | NaNO3/KNO3 | nitrate salt | approx. 220-240 | 90-120 | 90 | 180-210 | 200 to 260 C | medium | InfoTemp. group: 100 to 200 C Advantages: well-known salt chemistry; relatively low cost Disadvantages / points of attention: oxidising; corrosion; solidifies at a high temperature |
| Lithium nitrate | LiNO3 | nitrate salt | 253 | 250-260 | 65 | 315-325 | 230 to 270 C | medium-low | InfoTemp. group: 200 to 300 C Advantages: high latent heat Disadvantages / points of attention: lithium price; corrosion; oxidising |
| Bismuth | Bi | metal | 271 | 50 | 8 | 58 | 250 to 300 C | low-medium | InfoTemp. group: 200 to 300 C Advantages: high thermal conductivity; less toxic than Pb/Cd Disadvantages / points of attention: expensive; low latent heat per kg |
| Tin | Sn | metal | 232 | 60 | 10 | 70 | 210 to 250 C | low-medium | InfoTemp. group: 200 to 300 C Advantages: high thermal conductivity; well-known metal Disadvantages / points of attention: more expensive than salts; low latent heat per kg |
| Tin(II) chloride | SnCl2 | chloride salt | 247 | 50-70 | 45 | 95-115 | 225 to 265 C | low | InfoTemp. group: 200 to 300 C Advantages: relatively low melting point for a salt Disadvantages / points of attention: corrosive; moderate latent heat |
| Sodium nitrate | NaNO3 | nitrate salt | 306 | 170 | 90 | 260 | 280 to 340 C | medium | InfoTemp. group: 300 to 450 C Advantages: high latent heat; well-known salt Disadvantages / points of attention: oxidising; corrosion; decomposition under overheating |
| Potassium nitrate | KNO3 | nitrate salt | 334 | 95 | 90 | 185 | 310 to 370 C | medium-low | InfoTemp. group: 300 to 450 C Advantages: well-known and available Disadvantages / points of attention: lower latent heat; oxidising; corrosion |
| Sodium hydroxide | NaOH | hydroxide | 318 | 160-170 | 105 | 265-275 | 290 to 350 C | low-medium | InfoTemp. group: 300 to 450 C Advantages: low cost; high storage density Disadvantages / points of attention: highly corrosive; dangerous on contact with water |
| Potassium hydroxide | KOH | hydroxide | 360 | 150 | 105 | 255 | 330 to 390 C | low-medium | InfoTemp. group: 300 to 450 C Advantages: high storage density Disadvantages / points of attention: highly corrosive; hygroscopic |
| Zinc | Zn | metal | 419.5 | 112 | 25 | 137 | 390 to 450 C | medium | InfoTemp. group: 300 to 450 C Advantages: high conductivity; compact Disadvantages / points of attention: high density; oxidation; containment required |
| Cadmium | Cd | metal | 321 | 55 | 10 | 65 | 300 to 340 C | low | InfoTemp. group: 300 to 450 C Advantages: high conductivity Disadvantages / points of attention: cadmium is toxic; practically not recommended |
| Lead | Pb | metal | 327 | 23 | 7 | 30 | 300 to 350 C | low | InfoTemp. group: 300 to 450 C Advantages: low-cost metal; high density Disadvantages / points of attention: giftig; very low latent heat per kg |
| MgCl2-KCl-NaCl eutecticum | MgCl2/KCl/NaCl | chloride salt | 380-450 | 150-250 | 100 | 250-350 | 420 to 520 C | medium | InfoTemp. group: 300 to 450 C Advantages: cheaper than lithium salts; high temperature Disadvantages / points of attention: chloride corrosion; moisture-sensitive; HCl risk |
| Li2CO3-K2CO3 eutectic | Li2CO3/K2CO3 | carbonate salt | 490-500 | 250-300 | 120 | 370-420 | 460 to 540 C | medium | InfoTemp. group: 450 to 650 C Advantages: high latent heat; high temperature Disadvantages / points of attention: lithium costs; corrosion; material selection |
| Li2CO3-Na2CO3-K2CO3 eutectic | Li/Na/K carbonaten | carbonate salt | 397-500 | 200-280 | 150 | 350-430 | 450 to 550 C | medium | InfoTemp. group: 450 to 650 C Advantages: good storage density; known molten-salt domain Disadvantages / points of attention: corrosion; high melting temperature; lithium price |
| Al-Si eutectic | Al-Si | metal alloy | 577 | 400-560 | 60 | 460-620 | 550 to 620 C | medium-high technical | InfoTemp. group: 450 to 650 C Advantages: very high volumetric storage; high conductivity Disadvantages / points of attention: high temperature; oxidation; expansion; containment |
| Al-Cu-Si alloys | Al/Cu/Si | metal alloy | 520-620 | 250-450 | 120 | 370-570 | 500 to 650 C | medium | InfoTemp. group: 450 to 650 C Advantages: tunable transition; high conductivity Disadvantages / points of attention: alloy control; oxidation; cycling degradation |
| Mg-Zn alloys | Mg/Zn | metal alloy | 340-600 | 150-300 | 60-100 | 210-400 | afhankelijk legering | medium-low | InfoTemp. group: 450 to 650 C Advantages: lightweight; good conductivity Disadvantages / points of attention: Mg oxidation/flammability; alloy stability |
| Zinc-aluminium eutectics | Zn/Al | metal alloy | 380-420 | 100-200 | 50 | 150-250 | 350 to 450 C | medium | InfoTemp. group: 450 to 650 C Advantages: good thermal conductivity; compact Disadvantages / points of attention: oxidation; lower latent heat |
| Aluminium | Al | metal | 660 | 397 | 75 | 470 | 620 to 700 C | medium-high technical | InfoTemp. group: 650 C and higher Advantages: low-cost metal; high conductivity; high volumetric density Disadvantages / points of attention: oxidation; high temperature; volume change |
| Magnesium | Mg | metal | 650 | 370 | 85 | 455 | 610 to 690 C | medium-low | InfoTemp. group: 650 C and higher Advantages: lightweight; high latent heat Disadvantages / points of attention: fire/oxidation risk; difficult containment |
| Sodium chloride | NaCl | chloride salt | 801 | 480 | 70 | 550 | 760 to 840 C | medium | InfoTemp. group: 650 C and higher Advantages: low cost; high latent heat Disadvantages / points of attention: corrosive at high temperature; high melting temperature |
| Potassium chloride | KCl | chloride salt | 770 | 350 | 65 | 415 | 730 to 810 C | medium-low | InfoTemp. group: 650 C and higher Advantages: low cost; available Disadvantages / points of attention: chloride corrosion; high temperature |
| Calcium chloride | CaCl2 | chloride salt | 772 | 190 | 80 | 270 | 730 to 810 C | low-medium | InfoTemp. group: 650 C and higher Advantages: fairly low cost Disadvantages / points of attention: strongly hygroscopic; corrosive |
| Lithium carbonate | Li2CO3 | carbonate salt | 723 | 500 | 100 | 600 | 680 to 760 C | medium | InfoTemp. group: 650 C and higher Advantages: high latent heat Disadvantages / points of attention: lithium costs; corrosion; high temperature |
| Sodium carbonate | Na2CO3 | carbonate salt | 851 | 270 | 90 | 360 | 810 to 890 C | medium-low | InfoTemp. group: 650 C and higher Advantages: low cost; available Disadvantages / points of attention: corrosion; high temperature |
| Potassium carbonate | K2CO3 | carbonate salt | 891 | 235 | 90 | 325 | 850 to 930 C | medium-low | InfoTemp. group: 650 C and higher Advantages: available; high temperature Disadvantages / points of attention: corrosive; high melting temperature |
| Lithium fluoride | LiF | fluoride salt | 848 | 1000 | 160 | 1160 | 800 to 900 C | low-medium technical | InfoTemp. group: 650 C and higher Advantages: very high latent heat Disadvantages / points of attention: expensive; corrosive; fluoride safety |
| Sodium fluoride | NaF | fluoride salt | 993 | 790 | 110 | 900 | 950 to 1030 C | low-medium technical | InfoTemp. group: 650 C and higher Advantages: high latent heat Disadvantages / points of attention: fluoride corrosion; toxicity/safety |
| Copper | Cu | metal | 1085 | 205 | 40 | 245 | 1030 to 1130 C | low-medium | InfoTemp. group: 650 C and higher Advantages: high conductivity Disadvantages / points of attention: expensive; high temperature; moderate latent heat |
| Silicon | Si | metalloid | 1414 | 1800 | 90 | 1890 | 1350 to 1470 C | low / experimental | InfoTemp. group: 650 C and higher Advantages: extremely high latent heat Disadvantages / points of attention: very high temperature; material compatibility extremely difficult |
Sources and data use
This overview is a technical longlist. For final engineering, always use supplier data, DSC measurements and your own cycling tests. Useful general sources: